1. CSSR (CALL SETUP SUCCESS RATE)Definition: Rate of calls going until TCH successful assignment

2. SCR (SUCCESSFULL CALL RATE)Definition: Rate of calls going until normal release that is not interrupted by SDCCH DROP, neither by assignment failures, and neither by CALL DROP.

3. CALL DROP RATE (CDR)Definition: Rate of all losses of TCH connections during a call in relation to the number of successful Call Setups

4. HOSR (HAND OVER SUCCESS RATE)Definition: Successful internal and external outgoing handovers of total number of internal and external outgoing handover attempts

5. PSR (PAGING SUCCESS RATE)Definition: Rate of successful paging attempts of total number of paging attempts. The formula is based on NSS point of view (based on MSC or LAC)

6. LOCATION UPDATE SUCCESS RATEDefinition: Successful location updateattempts of total number of location update attempts. The formula is based on NSS point of view.

7. SDCCH BLOCK RATEDefinition: SDCCH congestion of total number of SDCCH seizure attempts

8. SDCCH DROP RATEDefinition: Dropped SDCCH connections of total number of SDCCH connections without TCH congestion.

9. TCH ASSIGNMENT BLOCK RATEDefinition: Rate of TCH unsuccessful seizures during assignment procedure due to congestion

10. TCH Assignment Failure Rate (exclude blocking)Definition: Rate of RTCH seizure failed (system + radio) during normal assignment procedure over the total amount of RTCH request for normal assignment procedure

11. EMD (Erlang Minute per Drop)Definition: Total of Erlang minutes (TCH occupation) in one period measurement per drop call (after TCH Assignment).

12. TCH AvailabilityDefinition: Available TCH of total number of defined TCH

13. RACH Success RateDefinition: Rate of Successful RACH over the total number of channel required message received

Why 13Kbps???? In GSM Um interface the voice code of each channel is 13kbps, from where we can say like this ? The Transcoder (XCDR) is required to convert the speech or data output from the MSC (64 kbit/s PCM), into the form specified by GSM specifications for transmission over the air interface, that is, between the BSS and MS (64 kbit/s to 16 kbit/s and vice versa).

The 64 kbit/s Pulse Code Modulation (PCM) circuits from the MSC, if transmitted on the air interface without modification, would occupy an excessive amount of radio bandwidth.

This would use the available radio spectrum inefficiently. The required bandwidth is therefore reduced by processing the 64 kbit/s circuits so that the amount of information required to transmit digitized voice falls to a gross rate of 16 kbit/s.

The transcoding function may be located at the MSC, BSC, or BTS.The content of the 16 kbit/s data depends on the coding algorithm used.  There are two speech coding algorithms available and selecting which one to use depends on the capabilities of the mobile equipment and the network configuration.

The Full Rate speech algorithm is supported by all mobiles and networks.  It produces 13 kbit/s of coded speech data plus 3 kbit/s of control data which is commonly referred to as TRAU data (Transcoder Rate Adaption Unit).  The TRAU data on the downlink will be used by the BTS and therefore removed from the 13 k of speech data beforetransmission on the air interface.  the 13 kbit/s of speech data is processed at the BTS to form a gross rate of 22.8 kbit/s on the air interface which includes forward errorcorrection.  In the uplink direction the BTS adds in TRAU data which will be used by the transcoder.

Enhanced Full Rate is an improved speech coding algorithm and is only supported by Phase 2+ mobiles and is optional in the Network.  It produces 12.2 kbit/s from each 64 kbit/s PCM channel.  The TRAU data in this case is made up to 3.8 kbit/s to keep the channel rate to and from

the BTS at 16 kbit/s as for Full Rate.  As with Full Rate the TRAU data is used at the BTS and Transcoder.

For data transmissions the data is not transcoded but data rate adapted from 9.6 kbit/s (4.8 kbit/s or 2.4 kbit/s may also be used) up to a gross rate of 16 kbit/s for transmission over the terrestrial interfaces, again this 16 kbit/s contains a 3 kbit/s TRAU.

Drive Testing

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The Purpose of Drive Testing

Drive testing is principally applied in both the planning and optimisation stage of

network development. However, there are other purposes for which drive testing can be used:•To provide path loss data for initial site survey work•To verify the propagation prediction during the initial planning of the network.•To verify the network system parameters, as defined in the EG8:

GSM/DCS System-Specific Parameters.•To provide the initial test parameters used in Benchmarking (as defined in

the “Analysis” section of the Network Performance and Monitoring Guideline).•To verify the performance of the network after changes have been made

e.g. When a new TRX is added; the removal or addition of a new site; any power Adjustments or changes to the antenna; any changes in clutter or traffic habits such as the addition of new roads etc.•To measure any interference problems such as coverage from

neighboring Countries.•To locate any RF issues relating to traffic problems such as dropped or

blocked calls.•To locate any poor coverage areas.•To monitor the network against a slow degradation over time, as well

as Monitoring the network after sudden environmental conditions, such as gales or electrical storms.•To monitor the performance of a competitor’s network.

When to Drive Test

Drive testing can take place during the day or at night and is dependant upon

the  Operator’s requirements and subscriber habits.

Drive testing during the day will mimic the conditions as seen by subscribers,

but may  clog up the network if call analysis is being performed.

Drive testing during the night will allow a greater area to be surveyed due to

the reduction  in vehicular congestion. It will also allow for certain test signals to be transmitted and  

 tested, particularly when setting up a new site, without interrupting normal operation.

However, night-time testing does not mimic the conditions experienced by subscribers.

For planning purposes, drive testing is typically performed at night and for

maintenance  purposes, drive testing is performed during the day.

Where to Drive Test

Some areas of a network will have greater performance problems than others. Drive testing should not be uniform throughout the whole network, but should be weighted 

 

towards areas where there are significant RF problems.There may be other areas of the network that require temporary coverage during a certain time of the year e.g. an exhibition centre or a sports stadium. These areas should be 

 

examined and planned in greater detail.

It is important that a drive test is documented. This is specified by the Operator and can either take the form of creating a new item of documentation or filling in an existing 

 

document. 

 

All documentation will be passed to Analysts and Engineers, who will need 

 

accurate records of any test work carried out.

----Route PlansThe area to be drive tested is ascertained before leaving the office. There are three levels of drive testing depending on the purpose of the test:Primary Route: This includes all major roads, highways and throughfares and should be given priority to all other roads when conducting a coverage test, unless a new site is put 

 into service for a specific objective.Secondary Route: This includes all streets, by-streets and compounds, where

accessible, such as a University Campus. Secondary routes are used in areas where problems have been located during a primary route test and further investigation is needed.Miscellaneous Routes: This includes in-building and non-access routes to vehicles such as shopping malls, golf courses, airports, hotels, conference centres etc. A

route is prepared by photocopying a map and highlighting the route to be driven. For primary routes, a map of scale no less than 1:20,000 should be used, and a map of scale 1:10,000 is recommended for secondary routes. It is recommended that the route is marked in a contiguous circuit, taking account of one-way streets at this stage.A drive test should be planned in both directions, where possible, and at the same

speed. This minimises any errors and checks the point of handovers and cell dimensioning. For new sites that are being tested, it is recommended that the transceiver is forced to camp onto the cell (forbidding any handovers) in order to ascertain the full coverage of the cell.The test should be re-driven with any forced handovers removed.

Layer 1 Messages

Other Layer 1 criteria that is useful for field measurements include:C1 criteria•ARFCN of Serving Cell - (TCH in dedicated mode, BCCH in idle mode))•Time Slot (TS)•

Layer 3 Messages

All Layer 3 messages should be collected where possible. Layer 3 Messages are

used by Analysts to determine more accurately the cause of a problem within the network.Some field test equipment can perform basic analysis of particular Layer 3

messages during data collection. This enables certain conditions such as call classification or handovers to be flagged to the survey technician.

Call Classification

In principle there are five call classifications, some of which can be sub-divided further.

Good Calls: These are calls that are successfully placed on the network and

maintained for the required duration.Dropped Calls: These are calls that are successfully placed on to the network

but are terminated without authorisation. Using Layer 3 Messages, these calls can be sub-divided into:End User Hang-up•System Hang-up•Other•Blocked Calls: These are calls that cannot be placed on to the network. Again, usingLayer 3 messages, these can be sub-divided as follows:System Busy•End User Engaged•No Service•Other•

Roamed Calls: These are calls that are successfully placed on another

network. Roamed calls may also be good calls or dropped calls.Noisy Calls: These are calls which have been successfully completed for the duration

of the call but which experienced a number of noise bursts that a subscriber may find intolerable. The threshold for determining the level of poor audio is programmed during the set-up of the test.In GSM, this particular classification is very difficult to determine with great

accuracy. It should be noted that it is not enough to monitor just the RxLEV and the RxQUAL.

TroubleshootingNo Data CollectedOccasionally, the equipment fails to trigger the collection device to save the data to file.Check all cables•Ensure the Processing Unit is powered•Re-start the laptop computer•Re-start the equipment•Re-drive the test.•

No Positional Information CollectedIf data is collected using GPS only, it may be possible that satellite reception was

lost during a drive through a tunnel etc. It is important that back-up equipment is used, such as a Dead-Reckoning device, since a GPS receiver will re-transmit the last known position until it receives an update. If the vehicle moves without GPS cover, the data will be inaccurate and cannot be analysed.Check the GPS antenna cable to the receiver•Drive to an open area and ensure that the GPS system is working correctly•If required, install a back-up positional device to safeguard against lost GPS•Coverage HolesIf there are patches of poor coverage in unexpected areas, it may indicate the fringes of acoverage hole. It is important to re-drive this particular area.Complete a route plan using secondary roads as far as possible•Make notes of any buildings / obstructions that may cause shadowing•Take note of pedestrian / vehicular habits in the area•

Dropped Calls

Dropped calls can be caused by either RF environments or incorrect system parameters.The following data should be checked to ensure that it has been collected properly.Layer 3 Messages•Neighbour Cell List (BA Table)•RxLEV (Server• & Neighbour)RxQUAL (Server• & Neighbour)

Finally, ensure that the automatic setting for the call length is not shorter than that

for the timer monitoring for unauthorised call drop-outs. The setting should be a minimum of 30 seconds.

Handover Problems

Handover problems are generally caused by inaccurate settings of the handover boundary.This can cause ping-ponging, where the server will keep changing, and congestion at theswitch. Check the following.The transceiver antenna is fitted correctly•Collection of Layer 3 Messages•Collection of Neighbour Cell List (BA Table)•Collection of Scanning Information•Collection of Cell Identities•Collection of T.Adv for the Serving Cell•Also, ensure that the collection of data from the new serving cell immediately after

the handover has occurred (particularly RxLEV and RxQUAL) is not timed to occur prior to the-synchronisation of the transceiver itself.If a particular serving cell can be isolated as a potential cause of handover

problems, slowly drive around the cell in a radius of around 500m - 1km, checking when handovers occur.Blocked Calls / System BusyIf calls are repeatedly classified as blocked, it is recommended that the drive test

is temporarily halted in order to try and locate the cause.Check that the number called is fully functional•Check that there is adequate coverage from the expected serving BTS•Check the equipment transceiver is functioning correctly by using an ordinary•mobile to call the officeIf all appears functional, try to place calls through an alternative BTS. If this•succeeds, inform the office immediately and re-suspend the drive test.

Dropped Call(TCH Drop-SDCCH Drop)-TCH Drop AnalysisEmail This BlogThis! Share to Twitter Share to Facebook Share to Google Buzz

 Step to check TCH Drop Analysis.

1. Radio Link Time-Out

Every time a SACCH message can not be decoded the radio link time-out counter is decreased by 1. If the message can be decoded the counter is incremented by 2. However, the value can not exceed the initial value. The initial value is set by the parameter RLINKT for radio link time-out in the mobile station and by RLINKUP for timeout in the BSC. If the mobile moves out of coverage and no measurement reports are received in the BSC, there will be a radio link time-out and the message Channel Release (cause: abnormal release, unspecified) is sent to the mobile station and the SACCH is deactivated in the BTS. A Clear Request message is sent to the MSC. To be sure that the mobile has stopped transmitting, the BSC now waits RLINKT SACCH periods before the timeslot is released and a new call can be established on the channel.Visit Out Forum For more Optimization Tips

2. Layer 2 Time-OutIf the BTS never get an acknowledge on a Layer 2 message after the time T200XN200, the BTS will send Error Indication (cause: T200 expired) to the BSC, which will send Channel Release (cause: abnormal release, timer expired) to the mobile station and a Clear Request to the MSC. The SACCH is deactivated and the BSC waits RLINKT SACCH periods before the timeslot is released and a new call can use the channel. This is only valid if the call is in steady state, i.e. not during handover or assignment. 

If you like this than Become our Friend on Facebook Click Here3. Release IndicationWhen the BTS received a layer 2 DISC frame from the mobile it replies with a Layer 2 UA frame to the mobile station and a Release Indication to the BSC. The system does only react on Release Indication if it is received during a normal disconnection situation. If such a message is received unexpectedly this will usually cause radio link time-out or timer T200 expiration as the mobile station stops the transmitting of measurement reports. It is also possible that the release will be normal depending on when the Release Indication is received.Visit Out Forum For more Optimization Tips4. MSC Time-OutNormal Release:If the MSC never received a response on a message (e.g. Identity Request) and there is no radio link time-out or layer 2 time-out, the MSC will send a Clear Command to the BSC. The time-out is depending on the message. When receiving Clear Command, the BSC will send a Channel Release (cause: normal release) and then deactivates the SACCH.Reject (only SDCCH):If the MSC never receives a response on the first message after Establish Indication, the MSC will send a reject message. If the connection was a Location Update it will be a Location Update Reject (cause: network failure) and if the connection was a mobile originating call (CM Service Request) a CM Service Reject (cause: network failure) will be sent. The MSC will then send a Clear Command to the BSC and the call is cleared by Channel Release (cause: normal release).

If you like this than Become our Friend on Facebook Click Here5. Assignment to TCHBefore sending an Assignment Command from the BSC at TCH assignment, the following two criterion have to be fulfilled:a. There must be a TCH channel available, i.e. no congestionb. The locating algorithm must have received at least one valid measurement report.If either of the criterion is not fulfilled, Assignment Command will not be sent and a Channel Release (cause: abnormal release, unspecified) will be sent to the mobile station and a Clear Request to the MSC. Visit Out Forum For more Optimization TipsTCH Drop reason (1)The classification of TCH Drop Reasons are arranged in the order of priority:1.Excessive Timing Advance2.Low Signal Strength3.Bad Quality4.Sudden Loss of Connection5.Other Reasons

Excessive Timing AdvanceThe TCH Drop counters due to Excessive Timing Advance will pegged when the during the time of disconnection, the last Timing Advance value recorded was higher than the TALIM Parameter. This drop reason is commonly apparent to isolated or island sites with a wide coverage area.Action:Check if the cell parameter TALIM is < "63"Solution:Set TALIM to a value close to 63.Tilt antenna/reduce antenna height/output power, etc. for co-channel cells.

TCH Drop Reasons (2)Low Signal Strength on Down or Uplink or Both LinksThe drops counters due to Low Signal Strength will be pegged when the Signal Strength during the last Measurement Report before the call dropped is below the LOWSSDL and/or LOWSSUL Thresholds. LOWSSDL and LOWSSUL are BSC Exchange Property parameters which is used only for statistics purposes and does not affect the behavior of calls. If both UL and DL Signal Strength are below the thresholds, only

Drop due to Low SS BL will pegged. Normally a call is dropped at the border of large rural cell with insufficient coverage. Bad tunnel coverage cause many dropped calls as well as so called coverage holes. Bad indoor coverage will result in dropped calls. Building shadowing could be another reason.Visit Out Forum For more Optimization Tips

Action:Check coverage plots.Check output power.Check power balance and link budget.Check if Omni site.Check antenna configuration & type.Check antenna installation.Perform drive tests & site survey.Check TRX/TS with high CONERRCNT.

Solution:Add a repeater to increase coverage in for example a tunnel.Change to a better antenna (with higher gain) for the base station.Add a new base station if there are large coverage holes.Block/Deblock TRX

TCH Drop Reasons (3)Poor Quality on Down or Uplink or Both LinksThe drops counters due to Bad Quality will be pegged when the Signal Strength during the last Measurement Report before the call dropped is above the BADQDL and/or BADQUL Thresholds. BADQDL and BADQUL (expressed in DTQU) are BSC Exchange Property parameters which is used only for statistics purposes and does not affect the behavior of calls. If both UL and DL Quality are above the thresholds, only Drop due to BAD Quality BL will pegged.Problem on Bad Quality is usually associated with Co-channel Interference on BCCH or TCH. Faulty MAIO assignment can cause frequency collisions on co-sited cells especially on 1x1 Reuse. External interference is also one possible cause of problem on quality.If you like this than Become our Friend on Facebook Click HereAction:Check C/I and C/A plots.Check Frequency Plan (Co-BCCH or Co-BSIC Problem).

Check MAIO, HOP, HSN parameters.Check FHOP if correctly configured (BB or SY).Check for External Interference.Perform drive tests.

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Solution:Change BCCH frequency.Change BSIC.Change MAIO, HOP, HSN.Change FHOP.Record RIR or on-site Frequency Scanning to identify source of interference.Use available radio features.

TCH Drop Reasons (4)Sudden Loss of ConnectionDrops due to Sudden Loss are drops that have not been registered as low signal strength, excessive timing advance, bad quality or hardware (other) reasons, and the locating procedure indicates missing measurement results from the MS.There are some common scenarios that could lead to Sudden Loss of connections such as very sudden and severe drops in signal strength, such as when subscribers enter into buildings, elevators, parking garages, etc., very sudden and severe occurrence of interference, MS runs out of battery during conversation, Handover Lost, BTS HW faults, Synchronization or A-bis link fault (transmission faults), andMS Faults.

Action:Check BTS Error Logs, Alarms and Fault Codes.Check CONERRCNT per TRX and TS.Check Transmission Link (A-bis).Check for DIP Slips.Check LAPD Congestion.Correlate Handover Lost to Drops due to Sudden Loss

Solution:Fix Hardware Faults and Alarms.Reset TRX with high CONERRCNT.

Ensure that Synchronization and A-bis Link are stable.Change RBLT with high DIP Slips.Change CONFACT or increase Transmission CapacityInvestigate HO Lost Problem

TCH Drop Reasons (5)TCH Drops due to Other ReasonsTCH drops due to Other Reasons are computed by subtracting the sum of drops due to Excessive TA, Low SS, Bad Quality and Sudden Loss from the Total TCH Drop Counts. Drops due to Other Reasons are generally associated with hardware problems, transmission link problems on A-bis, Ater or Ainterfaces, and sometimes Handover Lost.

Action:Check BTS Error Logs.Check Alarms and Fault Codes.Check CONERRCNT per TRX and TS.Check Transmission Link (A-bis).Check for DIP Slips.Correlate Handover Lost to Drops due to Other Reasons

Solution:Fix Hardware Faults and Alarms.Reset TRX with high CONERRCNT.Ensure that Synchronization and A-bis Link are stable.Change RBLT with high DIP Slips.Investigate HO Lost Problem

Problem reason of drop in SDCCH

Low Signal Strength on Down or UplinkThe reason for poor coverage could be too few sites, wrong output power, shadowing, no indoor coverage or network equipment failure.Action: Check coverage plots.Check output power. Perform drive tests. Check BTS error logSolution: Add new sites. Increase output power. Repair faulty equipment.

Poor Quality on Down or UplinkAction: Check C/I and C/A plots. Check frequency plan. Perform drive tests.

Solution: Change frequency. Use available radio features.

Too High Timing AdvanceAction: Check if the cell parameter TALIM is < style="font-weight: bold;">Solution: Set TALIM to a value close to 63. Tilt antenna/reduce antenna height/output power, etc. for cochannel cells.

Mobile ErrorSome old mobiles may cause dropped calls if certain radio network features are used. Another reason is that the MS is damaged and not working properly.Action: Check MS fleet.Solution: Inform operator.

Subscriber BehaviorPoorly educated subscribers could use their handsets incorrectly by not raising antennas, choosing illadvised locations to attempt calls, etc.Action: Check customer complaints and their MS.

Battery FlawWhen a subscriber runs out of battery during a conversation, the call will be registered as dropped call due to low signal strength or others.Action: Check if MS power regulation is used. Check if DTX uplink is used.

Congestion on TCHThe SDCCH is dropped when congestion on TCH.Action: Check TCH congestionSolution: Increase capacity on TCH or using features like Assignment to another cell, Cell Load Sharing, HCS, Dynamic Half-Rate Allocation and FR-HR Mode Adaptation etc

GSM IDENTITY NUMBERS(IMSI,TMSI,CGI,MSRN,IMEI)Email This BlogThis! Share to Twitter Share to Facebook Share to Google Buzz

GSM identities

The GSM network is complex and consists of the Switching System (SS)

and the Base Station System (BSS). The switching system, which consists

of HLR, MSC, VLR, AUC and EIR, interfaces both the Base Station

System and also other networks like PSTN/ISDN, data networks or other

PLMNs.

In order to switch a call to a mobile subscriber, the right entities need to be

involved. It is therefore important to address them correctly. The numbers

used to identify the identities in a GSM/PLMN network is described in this

chapter. See also Figure 56.

Numbering plans are used to identify different networks. For a telephone

number in the PSTN/ISDN network, numbering plans E.164 is used.

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Mobile Station ISDN Number (MSISDN)

The MSISDN is a number which uniquely identifies a mobile telephone

subscription in the public switched telephone network numbering plan.

According to the CCITT recommendations, the mobile telephone number

or catalogue number to be dialled is composed in the following way:

MSISDN = CC + NDC + SN

CC = Country Code

NDC = National Destination Code

SN = Subscriber Number

A National Destination Code is allocated to each GSM PLMN. In some

countries, more than one NDC may be required for each GSM PLMN. The

international MSISDN number may be of variable length. The maximum

length shall be 15 digits, prefixes not included.

Each subscription is connected to one Home Location Register (HLR).

The length of the MSISDN depends on the structure and numbering plan

of each operator, as an application of CCITT recommendation E.164.

The following is an example of dialling a GSM subscriber.

International Mobile Subscriber Identity (IMSI)

The IMSI is the information which uniquely identifies a subscriber in a

GSM/PLMN.

For a correct identification over the radio path and through the GSM

PLMN network, a specific identity is allocated to each subscriber. This

identity is called the International Mobile Subscriber Identity (IMSI) and

is used for all signalling in the PLMN. It will be stored in the Subscriber

Identity Module (SIM), as well as in the Home Location Register (HLR)

and in the serving Visitor Location Register (VLR).The IMSI consists of three different parts:

IMSI = MCC + MNC + MSIN

MCC = Mobile Country Code (3 digits)

MNC = Mobile Network Code (2 digits)

MSIN = Mobile Subscriber Identification Number (max 10 digits)

According to the GSM recommendations, the IMSI will have a length of

maximum 15 digits.

All network–related subscriber information is connected to the IMSI. See

also Figure 56.

Mobile Station Roaming Number (MSRN)

HLR knows in what MSC/VLR Service Area the subscriber is located. In

order to provide a temporary number to be used for routing, the HLR

requests the current MSC/VLR to allocate and return a Mobile Station

Roaming Number (MSRN) for the called subscriber, see Figure 56.

At reception of the MSRN, HLR sends it to the GMSC, which can now

route the call to the MSC/VLR exchange where the called subscriber is

currently registered.

The interrogation call routing function (request for an MSRN) is part of

the Mobile Application Part (MAP). All data exchanged between the

GMSC - HLR - MSC/VLR for the purpose of interrogation is sent over

the No. 7 signalling network.

The Mobile Station Roaming Number (MSRN), according to the GSM

recommendations, consists of three parts:

MSRN = CC + NDC + SN

CC = Country Code

NDC = National Destination Code

SN = Subscriber Number

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Temporary Mobile Subscriber Identity (TMSI)

The TMSI is a temporary number used instead of the IMSI to identify an

MS. It raises the subscriber’s confidentiality and is known within the

serving MSC/VLR-area and changed at certain events or time intervals.

The structure of the TMSI may be chosen by each administration but

should have a maximum length of four octets (8 digits).

International Mobile station Equipment Identity (IMEI)

The IMEI is used for equipment identification. An IMEI uniquely identifies a

mobile station as a piece or assembly of equipment. (See IMEI, chapter 5.)

IMEI = TAC + FAC + SNR + sp

TAC = Type Approval Code (6 digits), determined by a central GSM body

FAC = Final Assembly Code (2 digits), identifies the manufacturer

SNR = Serial Number (6 digits), an individual serial number of six digits

uniquely identifying all equipment within each TAC and FAC

sp = spare for future use (1 digit)

According to the GSM specification, IMEI has the length of 15 digits.

Location Area Identity (LAI)

LAI is used for location updating of mobile subscribers.

LAI = MCC + MNC + LAC

MCC = Mobile Country Code (3 digits), identifies the country. It follows the

same numbering plan as MCC in IMSI.

MNC = Mobile Network Code (2 digits), identifies the GSM/PLMN in that

country and follows the same numbering plan as the MNC in IMSI.

LAC = Location Area Code, identifies a location area within a GSM PLMN

network. The maximum length of LAC is 16 bits, enabling 65 536 different

location areas to be defined in one GSM PLMN.

Cell Global Identity (CGI)

CGI is used for cell identification within the GSM network. This is done by

adding a Cell Identity (CI) to the location area identity.

CGI = MCC + MNC + LAC + CI

CI = Cell Identity, identifies a cell within a location area, maximum 16 bits

Base Station Identity Code (BSIC)

BSIC allows a mobile station to distinguish between different neighboring

base stations.

BSIC = NCC + BCC

NCC = Network Colour Code (3 bits), identifies the GSM PLMN.

Note that it does not uniquely identify the operator. NCC is primarily used

to distinguish between operators on each side of border.

BCC = Base Station Colour Code (3 bits), identifies the Base Station to

help distinguish between BTS using the same BCCH frequencies

Location Number (LN)

Location Number is a number related to a certain geographical area, as

specified by the network operator by ”tying” the location numbers to cells,

location areas, or MSC/VLR service areas.

The Location Number is used to implement features like Regional /Local

subscription and Geographical differentiated charging.