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This slide is covering cellular concepts like Frequency reuse, splitting handoff etc
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04132023 1
UNIT-3
THE CELLUAR CONCEPT
DrVrince Vimal MIT MIET GROUP MEERUT
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 2
Cellular Systems--Cellular Concepts The cellular concept was a major breakthrough in solving the
problem of spectral congestion and user capacity It offered very high capacity in a limited spectrum allocation without any major technological changes
The cellular concept has the following system level ideas
Replacing a single high power transmitter with many low power transmitters each providing coverage to only a small area
Neighboring cells are assigned different groups of channels in order to minimize interference
The same set of channels is then reused at different geographical locations
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 3
When designing a cellular mobile communication system it is important to provide good coverage and services in a high user-density area
Reuse can be done once the total interference from all users in the cells using the same frequency (co-channel cell) for transmission suffers from sufficient attenuation Factors need to be considered include
Geographical separation (path loss)
Shadowing effect
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 4
Cell Footprint
The actual radio coverage of a cell is known as the cell footprint
Irregular cell structure and irregular placing of the transmitter may be acceptable in the initial system design However as traffic grows where new cells and channels need to be added it may lead to inability to reuse frequencies because of co-channel interference
For systematic cell planning a regular shape is assumed for the footprint
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 5
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 6
Frequency reuse Cellular system depends upon intelligent allocation and reuse
of channels Each BS is allocated separate group of channels to be used in
small geographic region called as CELL Adjacent cells are allocated separate group of channels BS antenna are designed to provide coverage to particular
cell By doing this same group of channels can be used again in
separate cells physically at large distance from cell containing those channels by very well keeping interference within tolerable limits
This design process of selecting and allocating the channels of CBS within system is called as frequency reuse
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 7
A cellular system which has a total of S duplex channels
S channels are divided among N cells with each cell uses unique and disjoint channels
If each cell is allocated a group of k channels then S = k N
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 8
Terminologybull Cluster size The N cells which collectively use the
complete set of available frequency is called the cluster size
bull Co-channel cell The set of cells using the same set of frequencies as the target cell
bull Interference tier A set of co-channel cells at the same distance from the reference cell is called an interference tier The set of closest co-channel cells is call the first tier There is always 6 co-channel cells in the first tier
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 9
Co-ordinates for hexagonal cellular geometry
bull With these co-ordinates an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 2
Cellular Systems--Cellular Concepts The cellular concept was a major breakthrough in solving the
problem of spectral congestion and user capacity It offered very high capacity in a limited spectrum allocation without any major technological changes
The cellular concept has the following system level ideas
Replacing a single high power transmitter with many low power transmitters each providing coverage to only a small area
Neighboring cells are assigned different groups of channels in order to minimize interference
The same set of channels is then reused at different geographical locations
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 3
When designing a cellular mobile communication system it is important to provide good coverage and services in a high user-density area
Reuse can be done once the total interference from all users in the cells using the same frequency (co-channel cell) for transmission suffers from sufficient attenuation Factors need to be considered include
Geographical separation (path loss)
Shadowing effect
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 4
Cell Footprint
The actual radio coverage of a cell is known as the cell footprint
Irregular cell structure and irregular placing of the transmitter may be acceptable in the initial system design However as traffic grows where new cells and channels need to be added it may lead to inability to reuse frequencies because of co-channel interference
For systematic cell planning a regular shape is assumed for the footprint
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 5
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 6
Frequency reuse Cellular system depends upon intelligent allocation and reuse
of channels Each BS is allocated separate group of channels to be used in
small geographic region called as CELL Adjacent cells are allocated separate group of channels BS antenna are designed to provide coverage to particular
cell By doing this same group of channels can be used again in
separate cells physically at large distance from cell containing those channels by very well keeping interference within tolerable limits
This design process of selecting and allocating the channels of CBS within system is called as frequency reuse
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 7
A cellular system which has a total of S duplex channels
S channels are divided among N cells with each cell uses unique and disjoint channels
If each cell is allocated a group of k channels then S = k N
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 8
Terminologybull Cluster size The N cells which collectively use the
complete set of available frequency is called the cluster size
bull Co-channel cell The set of cells using the same set of frequencies as the target cell
bull Interference tier A set of co-channel cells at the same distance from the reference cell is called an interference tier The set of closest co-channel cells is call the first tier There is always 6 co-channel cells in the first tier
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 9
Co-ordinates for hexagonal cellular geometry
bull With these co-ordinates an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 3
When designing a cellular mobile communication system it is important to provide good coverage and services in a high user-density area
Reuse can be done once the total interference from all users in the cells using the same frequency (co-channel cell) for transmission suffers from sufficient attenuation Factors need to be considered include
Geographical separation (path loss)
Shadowing effect
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 4
Cell Footprint
The actual radio coverage of a cell is known as the cell footprint
Irregular cell structure and irregular placing of the transmitter may be acceptable in the initial system design However as traffic grows where new cells and channels need to be added it may lead to inability to reuse frequencies because of co-channel interference
For systematic cell planning a regular shape is assumed for the footprint
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 5
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 6
Frequency reuse Cellular system depends upon intelligent allocation and reuse
of channels Each BS is allocated separate group of channels to be used in
small geographic region called as CELL Adjacent cells are allocated separate group of channels BS antenna are designed to provide coverage to particular
cell By doing this same group of channels can be used again in
separate cells physically at large distance from cell containing those channels by very well keeping interference within tolerable limits
This design process of selecting and allocating the channels of CBS within system is called as frequency reuse
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 7
A cellular system which has a total of S duplex channels
S channels are divided among N cells with each cell uses unique and disjoint channels
If each cell is allocated a group of k channels then S = k N
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 8
Terminologybull Cluster size The N cells which collectively use the
complete set of available frequency is called the cluster size
bull Co-channel cell The set of cells using the same set of frequencies as the target cell
bull Interference tier A set of co-channel cells at the same distance from the reference cell is called an interference tier The set of closest co-channel cells is call the first tier There is always 6 co-channel cells in the first tier
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 9
Co-ordinates for hexagonal cellular geometry
bull With these co-ordinates an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 4
Cell Footprint
The actual radio coverage of a cell is known as the cell footprint
Irregular cell structure and irregular placing of the transmitter may be acceptable in the initial system design However as traffic grows where new cells and channels need to be added it may lead to inability to reuse frequencies because of co-channel interference
For systematic cell planning a regular shape is assumed for the footprint
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 5
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 6
Frequency reuse Cellular system depends upon intelligent allocation and reuse
of channels Each BS is allocated separate group of channels to be used in
small geographic region called as CELL Adjacent cells are allocated separate group of channels BS antenna are designed to provide coverage to particular
cell By doing this same group of channels can be used again in
separate cells physically at large distance from cell containing those channels by very well keeping interference within tolerable limits
This design process of selecting and allocating the channels of CBS within system is called as frequency reuse
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 7
A cellular system which has a total of S duplex channels
S channels are divided among N cells with each cell uses unique and disjoint channels
If each cell is allocated a group of k channels then S = k N
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 8
Terminologybull Cluster size The N cells which collectively use the
complete set of available frequency is called the cluster size
bull Co-channel cell The set of cells using the same set of frequencies as the target cell
bull Interference tier A set of co-channel cells at the same distance from the reference cell is called an interference tier The set of closest co-channel cells is call the first tier There is always 6 co-channel cells in the first tier
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 9
Co-ordinates for hexagonal cellular geometry
bull With these co-ordinates an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 5
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 6
Frequency reuse Cellular system depends upon intelligent allocation and reuse
of channels Each BS is allocated separate group of channels to be used in
small geographic region called as CELL Adjacent cells are allocated separate group of channels BS antenna are designed to provide coverage to particular
cell By doing this same group of channels can be used again in
separate cells physically at large distance from cell containing those channels by very well keeping interference within tolerable limits
This design process of selecting and allocating the channels of CBS within system is called as frequency reuse
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 7
A cellular system which has a total of S duplex channels
S channels are divided among N cells with each cell uses unique and disjoint channels
If each cell is allocated a group of k channels then S = k N
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 8
Terminologybull Cluster size The N cells which collectively use the
complete set of available frequency is called the cluster size
bull Co-channel cell The set of cells using the same set of frequencies as the target cell
bull Interference tier A set of co-channel cells at the same distance from the reference cell is called an interference tier The set of closest co-channel cells is call the first tier There is always 6 co-channel cells in the first tier
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 9
Co-ordinates for hexagonal cellular geometry
bull With these co-ordinates an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 6
Frequency reuse Cellular system depends upon intelligent allocation and reuse
of channels Each BS is allocated separate group of channels to be used in
small geographic region called as CELL Adjacent cells are allocated separate group of channels BS antenna are designed to provide coverage to particular
cell By doing this same group of channels can be used again in
separate cells physically at large distance from cell containing those channels by very well keeping interference within tolerable limits
This design process of selecting and allocating the channels of CBS within system is called as frequency reuse
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 7
A cellular system which has a total of S duplex channels
S channels are divided among N cells with each cell uses unique and disjoint channels
If each cell is allocated a group of k channels then S = k N
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 8
Terminologybull Cluster size The N cells which collectively use the
complete set of available frequency is called the cluster size
bull Co-channel cell The set of cells using the same set of frequencies as the target cell
bull Interference tier A set of co-channel cells at the same distance from the reference cell is called an interference tier The set of closest co-channel cells is call the first tier There is always 6 co-channel cells in the first tier
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 9
Co-ordinates for hexagonal cellular geometry
bull With these co-ordinates an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 7
A cellular system which has a total of S duplex channels
S channels are divided among N cells with each cell uses unique and disjoint channels
If each cell is allocated a group of k channels then S = k N
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 8
Terminologybull Cluster size The N cells which collectively use the
complete set of available frequency is called the cluster size
bull Co-channel cell The set of cells using the same set of frequencies as the target cell
bull Interference tier A set of co-channel cells at the same distance from the reference cell is called an interference tier The set of closest co-channel cells is call the first tier There is always 6 co-channel cells in the first tier
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 9
Co-ordinates for hexagonal cellular geometry
bull With these co-ordinates an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 8
Terminologybull Cluster size The N cells which collectively use the
complete set of available frequency is called the cluster size
bull Co-channel cell The set of cells using the same set of frequencies as the target cell
bull Interference tier A set of co-channel cells at the same distance from the reference cell is called an interference tier The set of closest co-channel cells is call the first tier There is always 6 co-channel cells in the first tier
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 9
Co-ordinates for hexagonal cellular geometry
bull With these co-ordinates an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 9
Co-ordinates for hexagonal cellular geometry
bull With these co-ordinates an array of cells can be laid out so that the center of every cell falls on a point specified by a pair of integer co-ordinates
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 10
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 11
Designing a cellular system
bull N=19bull (i=3 j=2)
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 12
Designing a cellular system
bull The cluster size must satisfy N = i2 + ij + j2 where i j are non-negative integers
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 13
bull Can also verify that
where Q is the co-channel reuse ratio
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Problem
bull Total 33 MHz bw allocated to a FDD cellular system which uses 25 kHz simplex channels to provide full duplex voice and control channels Find the number of channels available per cell if a system uses a) four-cell reuse b) 7-cell reuse If 1 MHz of the allocated spectrum is dedicated to control channels find an equitable distribution of control channels amp voice channels
bull Total bw = 33 MHzndash Channel bw = 2 X 25khz = 50 khz ndash Total available channels S = 33 00050 = 660 channels
bull For N=4ndash Total no of ch per cell k = 6604 = 165 channels
bull For N = 7ndash Total no of ch per cell k = 6607 = 95 channels
bull 1MHz for control channels ie 100050 = 20 control channels So only 640 channels (660-20) would be allotted for voice
bull For N = 4 ndash 5 control ch + 160 voice ch per cell
bull For N =7ndash 4 cells with (3 control ch + 92 voice ch) amp 2 cells with (3 control + 90 voice ch) amp 1 cell with (2 control
ch + 92 voice channels)ndash Each cell with 1 control ch and 4 cells with 91 voice ch and 3 cells with 92 voice ch
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 15
Handover Handoff
Occurs as a mobile moves into a different cell during an existing call or when going from one cellular system into another
It must be user transparent successful and not too frequent
Not only involves identifying a new BS but also requires that the voice and control signals be allocated to channels associated with the new BS
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 16
Once a particular signal level Pmin is specified as the minimum usable signal for acceptable voice quality at the BS receiver a slightly stronger signal level PHO is used as a threshold at which a handover is made
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 17
bull =handoff threshold -Minimum acceptablesignal to maintain the callbull too smallndash Insufficient time to complete handoff before call is lostndash More call losses
bull too largendash Too many handoffsndash Burden for MSC
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 18
Dwell Time
The time over which a user remains within one cell is called the dwell time
The statistics of the dwell time are important for the practical design of handover algorithms
The statistics of the dwell time vary greatly depending on the speed of the user and the type of radio coverage
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 19
Handover indicator
Each BS constantly monitors the signal strengths of all of its reverse voice channels to determine the relative location of each mobile user with respect to the BS This information is forwarded to the MSC who makes decisions regarding handover
Mobile assisted handover (MAHO) The mobile station measures the received power from surrounding BSs and continually reports the results of these measurements to the serving BS
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Practical handover
bull The Umbrella Cell approach will help to solve this problems High speed users are serviced by large (macro) cells while low speed users are handled by small (micro) cells
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Practical handoverbull A hard handover does ldquobreak before makerdquo
ie The old channel connection is broken before the new allocated channel connection is setup This obviously can cause call dropping
bull In soft handover we do ldquomake before breakrdquo ie The new channel connection is established before the old channel connection is released This is realized in CDMA where also BS diversity is used to improve boundary condition
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Interference and System Capacity
bull In a given coverage area there are several cells that use the same set of frequencies These cells are called co-channel cells The interference between signals from these cells is called co-channel interference
bull If all cells are approximately of the same size and the path loss exponent is the same throughout the coverage area the transmit power of each BS is almost equal We can show that worse case signal to co-channel interference is independent of the transmitted power It becomes a function of the cell radius R and the distance to the nearest co-channel cell Drsquo
bull On control channel If leads to missed or block calls
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 23
In urban areas more severe due high RF noise floor
The 2 major types are
Co-Channel interference
Adjacent channel interfernce
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
04132023 DrVrince Vimal MIT MIET GROUP MEERUT 24
Interference and System Capacity
Q- Co-Channel reuse ratio is given by-
Let i0 is the no of co- channel nterfering cells than
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
ndash Received power at a distance d from the transmitting antenna is approximated by
ndash Useful signal at the cell boundary is the weakest given by Pr (R) Interference signal from the co-channel cell is given to be Pr (D ) prime
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Interference and System Capacityndash Drsquo is normally
approximated by the base station separation between the two cells D unless when accuracy is needed Hence
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Interference and System Capacity
bull For the forward link a very general case
where Di is the distance of the ith interfering cell from the mobile i0 is the total number of co-channel cells exist
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Interference and System Capacity
bull If only first tier co-channel cells are considered then i0 = 6
Unless otherwise stated normally assuming Di asymp D for all i
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Outage probabilitybull The probability that a mobile station does not receive a
usable signalbull For GSM this is 12 dB and for AMPS this is 18 dB If
there is 6 co-channel cells then
bull Exercise please verify thisndash For n=4 a minimum cluster size of N=7 is needed to meet the
SIR requirements for AMPSndash For n=4 a minimum cluster size of N=4 is required to meet the
SIR requirements for GSM
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Outage probability
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Outage probability
bull Approximation in distance has been made on the 2nd tier onwards
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Outage probability
bull More accurate SIR can be obtained by computing the actual distance
bull Our computation of outage only based on path loss For more accurate modeling shadowing and fast fading need to be taken into consideration This will not be covered in this course
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Coverage Problemsbull Revision
ndash Recall that the mean measured value
ndash Measurement shows that at any value of d the path loss PL(d) at a particular location is random and distributed log-normally (normal in dB) about this mean value
Pr (d)dB = Pr (d)dB + Xσwhere Xσ is a zero-mean Gaussian distributed random variable (in dB) with standard deviation σ(in dB)
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Boundary coveragebull There will be a proportion of locations at distance R (cell radius) where a
terminal would experience a received signal above a threshold γ (γ is usually the receiver sensitivity)
bull where Q(x) is the standard normal distribution
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Cell coveragebull Proportion of locations within the area defined by the cell
radius R receiving a signal above the threshold γ
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Cell coverage Solution can be found using the graph provided (n path loss exponent)
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Cell coveragebull Example if n=4 σ=8 dB and if the boundary is to have
75 coverage (75 of the time the signal is to exceed the threshold at the boundary) then the area coverage is equal to 94
bull If n=2 σ=8 dB and if the boundary is to have 75 coverage then the area coverage is equal to 91
bull 1048713 An operator needs to meet certain coverage criteria This is typically the ldquo90 rulerdquo ndash 90 of a given geographical area must be covered for 90 of the time
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area
Cell coveragebull The mean signal level at any distance is determined by path
loss and the variance is determined by the resulting fading distribution (log-normal shadowing Rayleigh fading Nakagami-m etc) In this course we will deal with log-normal shadowing only
bull The proportion of locations covered at a given distance (cell boundary for example) from BS can be found directly from the resultant signal pdfcdf
bull The proportion of locations covered within a circular region defined by a radius R (the cell area for example) can be found by integrating the resultant cdf over the cell area