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8/10/2019 Frequency Planning and Neighbor Cell Planning
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Frequency Planning and
Neighbor Cell Planning
ISSUE1.0
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Chapter 1 Frequency planning
Chapter 2 Tight frequency reuse
Chapter 3 Frequency hopping
Chapter 4 Neighbor Cell Planning
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Content of Frequency planning
Frequency resource of GSM system
Requirement for interference and carrier-to-
interference ratio
Signal quality grade coding
Concept of frequency reuse
4*3 frequency reuse
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GSM 900 :
GSM 1800 : 1710 1785 1805 1880
Duplex distance : 95 MHz
890 915 935 960
Duplex distance : 45 MHz
Frequency Resource of GSM System
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Frequency Band Configuration
GSM900:
BTS receiver (uplink ): f1 (n) =890.2+ (n-1)*0.2MHz
BTS transmitter (downlink ): f2 (n) =f1 (n) +45 MHz
GSM1800:
BTS receiver (uplink ): f1 (n) =1710.2 + (n-512) *0.2 MHz
BTS transmitter (downlink ): f2 (n) =f1 (n) +95 MHz
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All useful signals carrier
All useless signals interference=
GSM standard: C / I >= 9 dB
In practical projects: C / I >= 12dB
Useful signal Noise from environment
Other signals
Requirement for Interference and
Carrier-to-Interference Ratio
C/I =
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Requirement for Interference and
Carrier-To-Interference Ratio
All useful signals carrier
All useless signals interference=
GSM standard: C / I >= 9 dB
In practical projects: C / I >= 12dB
Useful signal Noise from environment
Other signals
C/I =
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Effect of Interference
Decrease of signal quality
Bit error Recoverable: channel coding, error correction
Irrecoverable: phase distortion System interference model
Unbalanced: uplink interference downlinkinterference
Asymmetrical: the interference is different at
the MS and BTS ends
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RXQUAL Mean BER BER rangeclass (%) from... to
0 0.14 < 0.2%
1 0.28 0.2 ... 0.4 %
2 0.57 0.4 ... 0.8 %
3 1.13 0.8 ... 1.6 %
4 2.26 1.6 ... 3.2 %
5 4.53 3.2 ... 6.4 %6 9.05 6.4 ... 12.8 %
7 18.1 > 12.8 %
Fairly good
Intolerable
Good
Acceptable
Signal Quality
Receiving quality (RXQUAL parameter)
Level of receiving quality (0 ... 7)
Bit error rate before decoding and error correction
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{fi,fj..fk}
{fi,fj..fk} {fi,fj..fk} {fi,fj..fk}.. ..
Macro-cell system
d
Micro-cell system
Concept of Frequency Reuse
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The Reason of Frequency Reuse
Frequency resource is limited. If there is 8MHz
frequency resource, 8 MHz = 40 channels * 8
timeslots = 320
==> max. 320 users can access the network
at the same time.
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Looser reuse
Higher frequency reuseefficiency, but interference
is serious. More technique
Is needed.
Tighter reuse
0 10 20
Little interference, but frequency
reuse efficiency is low.
Reuse Density Reuse density is the number of cells in a
basic reuse cluster.
4*312
n*mn*m
n: BTS number in a basic reuse cluster
m: Frequency group number in a BTS
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Interference (C/I) Estimation
6
1
q
I
C
1/2
q = D/R = ( 3 k )
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R
D
This old-fashioned frequency distribution
mode is not recommended
Frequency Reuse Patterns
Purpose: to minimize the interference in thewhole network with the final frequencyallocation plan
Theoretically
Regular hexagon cell
Regular network distribution
Cell cluster
Multiplexing distance
D = R *sqrt(3*K)
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A1
C1
B1
D1A2
A3B2
B3
C2
C3D2
D3
A1
C1
B1
D1A2
A3B2
B3
C2
C3D2
D3
A1
C1
B1
D1A2
A3B2
B3
C2
C3D2
D3 A1C1
B1
D1A2
A3B2
B3
C2
C3D2
D3
A1
C1
B1
D1A2
A3B2
B3
C2
C3
D2D3
A1C1
B1
D1A2
A3B2
B3
C2
C3D2
D3
4*3 Frequency Reuse
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A1 B1 C1 D1 A2 B2 C2 D2 A3 B3 C3 D3
34 34 35 36 37 38 39
40 41 42 43 44 45 46 47 48 49 50 51
52 53 54 55 56 57 58 59 60 61 62 63
64 65 66 67 68 69 70 71 72 73 74 75
76 77 78 79 80 81 82 83 84 85 86 87
88 89 90 91 92 93 94 95
Illustration of Frequency Allocation of
4*3 Frequency Reuse
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Chapter 1 Frequency planning
Chapter 2 Tight frequency reuse
Chapter 3 Frequency hopping
Chapter 4 Neighbor Cell Planning
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Tight Frequency Reuse Technology
Multi-layer reuse pattern
Underlaid and overlaid cell
1*3
1*1
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Multi-layer Reuse Pattern
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BCCH: n1
TCH1: n2
TCH2: n3
TCHm-1: nm
n1 n2n3 n4 ...... nm
And n1+n2+...+nm
=n
Multi-layer Reuse Pattern
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Multi-layer Reuse Pattern Frequency
Allocation Suppose that the available frequency carrier is 10MHZ, channel
number is 4694, the Multi-layer reuse pattern should be:
RC type Allocatedfrequencies
Number ofavailablefrequencies
BCCH 46~57 12
TCH1 58~66 9
TCH2 67~74 8
TCH3 75~82 8
TCH4 83~88 6
TCH5 89~94 6
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BCCH TCH1 TCH2 TCH3 TCH4
{f1,f3,f5...f23}
{f1,f2,f3,f4,f5...f40}
{f2,f4..f22,f24...f40}
Multi-layer Reuse Pattern Frequency
Allocation
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cap N BW
re use
i
i
.
Advantages of Multi-layer Reuse
Pattern
Capacity increase when reuse density is multiplied: Supposing there are 300 cells Bandwidth: 8 MHz (40 frequency)
Normal 4*3 reuse: reuse density=12 ==> network capacity = 40/12 * 300 = 1000
TRX
Multiple reuse: BCCH layer: re-use =14, (14 frq.) Normal TCH layer: re-use =10, (20 frq.) Aggressive TCH layer:re-use = 6, (6 frq.) ==> Network capacity = (1 +2 +1)* 300 = 1200
TRX
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cap N BW
re use
i
i
.
Advantages of Multi-layer Reuse
Pattern Capacity increases when reuse density is multiplied:
Supposing there are 300 cells Bandwidth: 8 MHz (40 frequency)
Normal 4*3 reuse: reuse density=12 ==> network capacity = 40/12 * 300 = 1000 TRX
Multiple reuse: BCCH layer: re-use =14, (14 frq.) Normal TCH layer: re-use =10, (20 frq.) Aggressive TCH layer:re-use = 6, (6 frq.) ==> Network capacity = (1 +2 +1)* 300 = 1200
TRX
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The inner circle covers a smaller area, and the frequency
can be reused more tightly.
Underlaid/Overlaid Frequency
Allocation
Overlaid-cellUnderlaid-cell
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Super fn
Regular fm Regular fm
Regular fm
Super fn
BCCH 15f Regular 24f Super 12f
BCCH Reuse density: 15
R TCH TRX reuse density: 12
S TCH TRX reuse density: 6
Overlaid/Underlaid Frequency
Configuration
Super fn
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BCCH14+TCH36
1BCCH+3TCH
1BCCH+3TCH 1BCCH+3TCH
1BCCH+12TCH
1BCCH+12TCH 1BCCH+12TCH
4*3 1*3
4*3 and 1*3 Reuse Patterns
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TRX1 TRX2 ... TRX7
TRX8TRX9... TRX14 TRX15TRX16...TRX21
TRX1TRX2 ... TRX7
TRX8TRX9... TRX14 TRX15TRX16...TRX21
The red items are BCCH RCs
Illustration of 1*3 TCH Frequency
Allocation
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Frequency Planning Principle There should be no co-channel frequency carriers in one BTS.
The frequency separation between BCCH and TCH in the same cell shouldbe not less than 400K.
When frequency hopping is not used, the separation of TCH in the samecell should be not less than 400K.
In non-1*3 reuse mode, co-channel should be avoided between theimmediately neighbor BTS.
Neighbor BTS should not have co-channels facing each other directly.
Normally, with 1*3 reuse, the number of the hopping frequenciesshould be not less than twice of the number of frequency hopping TRXin the same cell.
Pay close attention to co-channel reuse, avoiding the situation that thesame BCCH has the same BSIC in adjacent area.
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.
Example of Frequency Planning
An example network in a specific place, BTSare densely located. The topography is plain.The maximum BTS configuration is S3/3/2
Initial planning:
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Example of Frequency Planning
Final frequency planning:
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Example of 1*3 Frequency Reuse
Suppose 900 band: 96124
BTS configuration: S3/3/3
BCCH layer: 96
109 reuse pattern: 4*3 TCH layer: 110124 reuse pattern: 1*3
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Group 1 (MA1): 110 111 112 113 114 Cell1
Group 2 (MA2): 115 116 117 118 119 Cell2
Group 3 (MA3): 120 121 122 123 124 Cell3
TCH Consecutive Allocation Scheme
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TCH Interval Allocation Scheme
Group 1 (MA1): 110 113 116 119 122 Cell1
Group 2 (MA2): 111 114 117 120 123 Cell2
Group 3 (MA3): 112 115 118 121 124 Cell3
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Comparison Between Multi-layer
reuse and 1*3 For Multi-layer reuse pattern, either Base band hopping or RF hopping can be
used. But for 1x3 reuse, only RF hopping can be used.
Multi-layer reuse pattern is a gradual process for TCH frequency planning. In
other words, the reuse is rather loose in TCH1 layer and it is quite close in the
last TCH layer (such as TCH5). The reason for this pattern is that base band
hopping is used in the Multi-layer reuse pattern. When there are rather few
frequency carriers, the hopping gain is small. Therefore, more frequency carriersshould be allocated for the layer with small TCH and then the reuse coefficient is
relatively large. When RF hopping is used in the Multi-layer reuse pattern and
there are a large number of frequency carriers, the hopping gain is high and the
reuse coefficient can be very small. In addition, the Multi-layer reuse pattern is of
a free pattern. It is different from base band hopping, in which the reuse must be
loose in the first TCH layer and more close in inner layers.
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Chapter 1 Frequency planning
Chapter 2 Tight frequency reuse
Chapter 3 Frequency hopping
Chapter 4 Neighbor cell planning
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Content of Frequency Hopping
Class of hopping
Advantages of hopping
Parameter of hopping
Collocation of hopping data
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Content of Frequency Hopping
Class of hopping
Advantages of hopping
Parameter of hopping
Collocation of hopping data
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Frequency Hopping
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Class of Hopping
Hopping can be implemented in two ways
Base-band hopping
RF hopping
Class according to the min hopping time unit
Timeslot hopping
Frame hopping
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Base Band Hopping Principle
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RF Hopping Principle
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Class of Hopping
Frame hopping
Frequency changes every TDMA frame. The different
channel of one TRX uses the same MAIO.
Timeslot hopping
Frequency changes every timeslot. The different channel
of one TRX uses the different MAIO.
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Advantages of Hopping
Get an agreeable radio environment.
Provide a similar communication quality for
every user.
Tighter reuse patterns are possible to be usedfor larger capacity.
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Smoothen the rapid fading (Rayleigh fading)
Frequency Diversity of Hopping
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Smoothen and average the interference
Interference Diversity of Hopping
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Hopping Parameters
All the parameters which are related to hopping are configured in
cell/configure Hopping data
Hopping mode: the mode used by the BTS system, including three
options: not hopping, base band hopping and RF hopping.
MA (Mobile Allocation Set): the set of available RF bands when
hopping, containing at most 64 frequency carriers. The frequency
being used must be those of the available frequency
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Description of Hopping Parameters
HSNhopping sequence number063.
HSN=0cycle hopping.
HSN0random hopping. Every sequence number
corresponds a pseudo random sequence.
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Hopping Parameters
MAIO (Mobile Allocation Index Offset): used to define the initialfrequency of the hopping.
Be careful to configure the MAIO of same timeslot in all channels,
otherwise interference occurs.
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Description Hopping Parameters
At the air interface, the frequency used on a specific burst is
an element in MA set. MAI is used for indication, referring to
a specific element in the MA set.
MAI is the function of TDMA FN, HSN and MAIO.
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Chapter 1 Frequency planning
Chapter 2 Tight frequency reuse
Chapter 3 Frequency hopping
Chapter 4 Neighbor cell planning
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Why
Handover is based on the neighbor relationship. Existing problem of neighbor planning No neighbor relationship, no handover
Co-BCCH and co-basic between adjacent cells leadto handover failure.
redundant neighbors
missing neighbor
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Neighbor Cell Description
There are table BA1 and table BA2.
Table BA1 describes BCCH frequencies of the adjacent cells to be measured when the MS is in
idle mode.
Table BA2 describes BCCH frequencies of the adjacent cells to be measured when the MS is in
dedicated mode.
There are two kinds of neighbors
bidirectional neighbors
unidirectional neighbors
Bidirectional neighbors are common, and unidirectional neighbors are used in special
condition, such as overshooting
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The cells of co-site must be set as neighbor cells The cells confronting directly must be added to neighbor list
The cells facing toward the same direction should be neighbors The cells shooting by the original cell
The cells shooting at the original cell
The cells, one site apart, face to face should be neighbor cells.
Neighbor Planning Principle
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Demonstration (ideally)
co-site cellConfronting cell
same directional cell
one site apart
face to face cell
Original cell
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