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Myson Engineering Systems

Drive Test

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Sr. No Activity Type Description

1 Benchmarking Drive for checking the difference between operators

2 Cluster Drives Drive test between difference operators for checking the RX Level, RX Quality, SQI, C/I, CSSR

& DCR etc.

3 Rehoming Activity Drive to newly Rhome sites to confirm the status either sites working properly.

4 Single Site DT Drive newly Commissioned sites, swap sites to check the implemented parameters & Rx level,

Rx Quality, SQI & C/I etc.

5 Optimization DT Joint visit for hardware changes and confirm the status on the site, changes in azimuth,

Electrical tilt, mechanical tilt, etc.

6 Reports & Analyze log

files Making reports for sites , cluster drives & Benchmarking

Work Process Collect OMC Parameter

Database RF Network Design

Cell File (TEMS) And Dot Tab Site (MapInfo)

Drive Test Measurements

Analysis Programs

Coverage

Dropped Calls

Call Setup Success

Handover Perf.

Speech Quality

General Check

Verification of RF Network Design

Site Check

SQI

Drive Test Tools

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TEMS Phone

Laptop For Data collection

USB GPS for Rout

TEMS Software & installation

CD

Drive Test Tools

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Data cables

Inverter for Laptop charging

Laptop charger

Car for DT

Following is the procedure and parameters that need to checked while performing Drive Test for a New Site.

1. Physical Verification, Alarm Verification, Frequency Plan Verification

2. CPC (Cell Parameter Check)

3. MOC (Mobile Originated Calls)

4. MTC (Mobile Terminated Calls – Prepaid to Postpaid)

5. SMS (Short Messaging Service)

6. GPRS

7. EDGE

8. Intra Site Handover

9. Inter Site Handover

10. TRX Test

11. Idle Drive (Normal Drive & Frequency Lock Drive)

12. Dedicated Drive

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Physical Verification Physical Verification is carried out by verifying physical parameter of the New Site with the TSSR (Technical Site Survey Report) such as Address, Lat, Long, Building Height, Antenna Height, Antenna Type, Orientation, and Tilt. Alarm Verification Alarms are generated mainly due to number of reasons, and these needs to check before Drive is being carried out for the Site. Alarms are checked from the NOC (Network Operating Centre) and if found needs to be verified before drive being carried out. Frequency Plan Verification Frequency Plan can be verified from the NOC (Network Operating Centre) for BCCH and TCH frequencies being implemented as per the Site Integration Sheet sent to NOC (Network Operating Centre). Hardware Configuration Verification Hardware verification is performed to know the Site type, BTS Type, TRX Configuration, VSWR checking, Power measurement for each TRX.

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Given are the parameters that need to be checked while performing CPC.

CGI (Cell Global Identity) consists if MCC+NCC+LAC+CI

Cell GPRS Support

GSM Band

BCCH Frequency

BSIC

Mode

Time Slot

Channel Type

Channel Mode

Speech Codec

Hopping Channel

Hopping frequency

MAIO

HSN

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1.Time: It is system time of computer.

2.Cell name: It displays the name of the sector which is serving according to the cell file that is loaded in TEMS.

3.CGI : It stands for the Cell Global Identity which is unique for every sector of the site. It consists of MCC,MNC,LAC,CI.

MCC: Mobile Country Code 0 – 999 MNC: Mobile Network Code 0 – 99 LAC : Location Area Code 0 -65535 CI: Cell Identity 0 – 65535

•Cell GPRS Support: Tells sector is having GPRS or not. Values are Yes or No .

•Band : It tells in which Freq. Band mobile is operating e.g. GSM 900/ 1800.

•BCCH ARFCN: It tells by which BCCH is the mobile station getting served.

•TCH ARFCN: On which Traffic Freq. call is going on.

•BSIC (Base Station Identity Code) : It is combination of Network Color Code (NCC) (0 – 7) & Base Station Color Code (BCC) (0 – 7). e.g. 62. It is decoded by mobile on every Sync. Channel Message.

•Mode: It is shows in which state is mobile operating, Idle, Dedicated & Packet.

•Time slot: On which time slot of current TCH call is going on. Viz. time slot no. of TRX.

•Channel Type: Type of channel mobile is getting now. Like BCCH / SDCCH/8 + SACCH/C8 or CBCH / TCH/F +FACCH/F +SACCH/F.

•Channel Mode : Shows mode of coding like Speech Full Rate of Half Rate.

•Speech Codec: It shows FR for Full Rate, HR for Half Rate & EFR for Enhanced Full Rate.

•Ciphering Algorithm : It shows ciphering algorithm used by the system to protect data for privacy. E.g. Cipher by A5/2.

•Sub Channel Number: It is displayed at a time when mobile is on dedicated mode at time of call setup when it is getting SDCCH at that time it shows which SDCCH it is getting out of 8 available. E.g. 2.

•Hopping Channel : It shows that current sector is having hopping feature or not. Values are Yes or No.

•Hopping Frequencies : It displays no. of freq. on which mobile is allowed to hop. viz. MA List for hopping of that sector.

•Mobile Allocation Index Offset (MAIO): It is the number which tells from which freq. from given MA list for sector hopping has to be started. E.g. 0 means sector will start from first freq. to hop.

•Hopping Sequence Number (HSN) : Indicates sequence in which frequencies are allowed to hop from the MA List. 0- 63. 0 for Cyclic Hopping, 1 – 63 random hopping sequences.

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Given are parameter need to be checked while performing MOC and MTC

RX Level (-47 dbm to -110dbm)

RX Quality (0 to 7)

SQI (20 to 30)

DTX

HSN (Hopping Sequence Number) (0 to 63)

MAIO

Hopping Frequency

C/ I Ratio (>15 dbm)

C/ A Ratio (>12 dbm)

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•RxLev : Receiving level in terms of dBm that mobile is receiving from the site. Range of -30 dBm to -110dBm.

•RxQual : Quality of voice which is measured on basis of BER. Range of RxQual 0 -7.

•FER : Frame Erasure Rate it represents the percentage of frames being dropped due to high number of non-corrected bit errors in the frame. It is indication of voice quality in network.

•BER Actual : Ratio of the number of bit errors to the total number of bits transmitted in a given time interval. BER is a measure for the voice quality in network.. Depending on BER RxQual is measured. E,g, BER 0 to 0.2 % corresponds to RxQual 0. Max. BER countable and useful is up to 12.8 % which corresponds to RxQual of max. 7.

•SQI : SQI is a more sophisticated measure which is dedicated to reflecting the quality of the speech (as opposed to radio environment conditions). This means that when optimizing the speech quality in your network, SQI is the best criterion to use. SQI is updated at 0.5 s intervals. It is computed on basis of BER and FER. For EFR 30, FR – 21 & HR – 17 are respectively ideal values.

•C/I : The carrier-over-interference ratio is the ratio between the signal strength of the current serving cell and the signal strength of undesired (interfering) signal components. It should be at least > 9 .

•MS Power Control Level: Displays range of power control from 0 to 8 depending upon network design. E.g. 0 means no power control and 1 means level that is defined by operator viz. 2 dBm less acc.

•DTX : Discontinuous transmission (DTX) is a mechanism allowing the radio transmitter to be switched off during speech pauses. This feature reduces the power consumption of the transmitter, which is important for MSs, and decreases the overall interference level on the radio channels affecting the capacity of the network..

•TA : Value that the base station calculates from access bursts and sends to the mobile station (MS) enabling the MS to advance the timing of its transmissions to the BS so as to compensate for propagation delay. Value of 0 means MS in radius of 550mt. From BS.

•RL Timeout Counter (Cur) : This parameter define the maximum value of the radio link counter expressed in SACCH blocks. Range of 4 – 64 in step size of 4. it shows current value of RLT. Decrease by 1 but increase by 2. When it reaches zero it results in normal DROP Call.

•RL Timeout Counter (MAX) : This parameter define the maximum value of the radio link counter expressed in SACCH blocks. Range of 4 – 64 in step size of 4. it shows current value of RLT. Normally 16, 20, 24.

•MS Behavior Modified : This window shows current settings for the mobile station, for instance whether handover is disabled or multiband reporting enabled.

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This is performed to check whether GPRS is working on the Site. This is done by browsing a web page in browser of the phone. For GPRS to be checked it is Necessary to see that the handset is WAP, GPRS enabled.

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ModeGPRS

This is performed to check whether Edge is working on the Site. This is done by browsing a web page in browser of the phone. For Edge to be checked it is Necessary to see that the handset is WAP, EDGE enabled.

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Mode EDGE

Intra Handover is performed to check whether handover is taking place both ways on the Site.

Handover is performed among all the Sectors of the Site.

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Inter site Handover is performed to check whether handover is taking place both ways on the Site with its adjacent neighbor. Handover needs to check mandatory for primary neighbor.

Handover is performed with the entire defined neighbor's in the integration sheet.

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Idle Drive is performed in two fashion • Normal Drive • Frequency Lock Drive Normal Drive This is done to frame the potential area of the new site planned. It also helps us to get to know the important neighboring sites for which the handover has to take place. Frequency Lock Drive This is done by locking the BCCH frequency of the serving cell and performing the drive for the same cell unless the mobile enters into No Service Mode. This is use- full for making decision related to GSM antenna height, tilt, and orientation. Dedicated Drive Dedicated drive is an important part of Drive Test. Here call is made to a test number and drive is done for the potential areas of the Site. During drive being carried out one has constantly monitor parameters such as RX Level, RX Quality, SQI, DTX, C/I Ratio, Hopping Channel, Neighbor list, TA (Timing Advance).

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Testing Live

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GSM Call Flow (GSM Originating Call)

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GSM Call Flow (GSM Originating Call)

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GSM Call Flow (GSM Originating Call)

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GSM Call Flow (GSM Originating Call)

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DT report Sample

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Site Checklist

Site Code LLR536

Site Id 1959

City LAHORE

Latitude 31.473487

Longitude 74.415446

Site Type (1 to 6) 3

RF Design

Antenna Band Height (m) Azimuth

(Degree) Mech Tilt (Degree) Elect Tilt (Degree) Antenna type

Sector 1 900 20 0 0 6 K742266

1800 20 0 0 4 K742266

Sector 2 900 22 120 0 6 K742266

1800 22 120 0 4 K742266

Sector 3 900 20 230 0 6 K742266

1800 20 230 0 4 K742266

Sector 4

Band Sector BCCH LAC NCC BCC HSN

GSM 900

Sect A 76 409 3 7 13

Sect B 65 409 4 6 13

Sect C 67 409 3 6 13

Sect D

GSM 1800

Sect A

Sect B

Sect C

Sect D

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Site Drive Test Analysis

Band Sector

BCCH / TRX1 TRX 2 TRX 3 TRX 4

Freq/Maio Rx Lev Maio Rx Lev Maio Rx Lev Maio Rx Lev

GSM 900

Sect A 76 -34 0 -34

Sect B 65 -34 2 -34

Sect C 67 -34 4 -34

GSM 1800

Sect A 0 -34 2 -34

Sect B 8 -34 10 -34

Sect C 16 -34 18 -34

Site HO

Sector Calls

Established

Successful

Calls Blocked Calls Dropped Calls

No. of Attempts No. of Success

56 56

Sect A 16 16 0 0

Sect B 16 16 0 0 SEC A SEC B SEC C

Sect C 16 16 0 0 HR Status Not Set Not Set Not Set

PC Status Not Set Not Set Not Set

TA Restriction 255 255 255

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Rx Quality Plot .

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RX Level Plot .

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DT Reports for Data Radio Network Planning

Site EDGE Verification Report

Site ID: LLR536

Site Type: GSM:2/2/2,

DCS:2/2/2

Date: 10-Sep-08

Site Configuration (GERNAL)

LAYER STRATEGY BTSs BAND TRXs TSL0 TSL1 TSL2 TSL3 TSL4 TSL5 TSL6 TSL7 PSW

terr.

Cell / Segment Option1 Layer1 CSW, GPRS, EGPRS

BTS1 900 TRX1 CBCCH

SDCC

H

TCH/

D

TCH/

D

Defaul

t

Defaul

t

Defaul

t

Dedicate

d EGPRS

TRX2 SDCCH TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F

BTS2 1800

TRX3 TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F TCH/F

TRX4 TCH/F TCH/F TCH/F TCH/F Defaul

t

Defaul

t

Defaul

t

Dedicate

d GPRS

Cell Reselection (E-G-E) TEST Static Downloading

TEST ( 320 KB)

Sectors Yes No Sectors Downloading time

(Sec)

Avg Data rate

(Kbps) TA C/I

Sec-1 a Sec-1 38.73 66.10 0 35

Sec-2 a Sec-2 41.3 61.99 0 35

Sec-3 a Sec-3 38.98 65.67 0 35

PDP Context Activation Routing Area Update

Activation Failure Success rate Area Update Failure Rate

20 0 100% 0 0 100%

RLC EDGE Throughputs

Sectors Peak Throughput

Minimum

Throughtput

Peak

Throughput Minimum Throughtput

UL (Kbps) DL (Kbps)

Sec-1 15.34 0.63 172.52 12.68

Sec-2 5.75 0.63 136.23 10.14

Sec-3 5.06 0.63 120.01 10.03

Drive Test throughput Distribution .

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Drive Test C/I Distribution .

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EDGE Connection Stability

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EDGE RLC throughput coverage .

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EDGE Coding Scheme coverage .

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EDGE Coding Scheme Usage .

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Cluster Drive report

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RX LEVEL

.

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RX Quality

.

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SQI

.

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Event Plots

.

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Benchmarking Plots

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RX Level plot

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Rx Qual

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RX level

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Rx quality

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Events

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CC Messages Count

CC Setup 11

CC Call Confirmed 0

CC Connect 10

CC Alerting 10

RR Messages Count

RR Handover Command 43

RR Handover Complete 34

RR Handover Failure 9

MM Messages Count

MM Location Updating Request 1

MM Location Updating Accept 1

MM Location Updating Reject 0

Events Formulae

CSSR 1: (Calls Completed + Calls Dropped) / Call Attempts

CSSR 2: Outgoing and Incoming Call Setup / Call Attempts

CCR 1: Calls Completed / Call Attempts

CCR 2: Calls Completed / Calls Setup OK

HSR: Handovers Successful / Handover Attempts

LUSR: Location Update Successful / Location Update Attempts

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Summary

Call Setup Success Rate (CSSR) 75.00% 83.33%

Call Completion Rate (CCR) 66.67% 80.00%

Handover Success Rate (HSR) 79.07%

Location Update Success Rate (LUSR) 100.00%

Events

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The Events Count

Outgoing Call Starts 12

Outgoing Call Setup OK 10

Outgoing Call Setup Failure 2

Incoming Call Starts 0

Incoming Call Setup OK 0

Incoming Call Setup Failure 0

Call Completed 8

Call Dropped 1

Handover OK 34

Handover Failure 9

Location Update OK 1

Location Update Failure 0

Rx level Distribution

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0

2000

4000

6000

8000

10000

12000

-110 -106 -102 -98 -94 -90 -86 -82 -78 -74 -70 -66 -62 -58 -54 -50 -46 -42

#

dBm

RxLevSub Distribution

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Rx Qual Distribution

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0

20000

40000

60000

80000

100000

120000

0 1 2 3 4 5 6 7

#

RxQual

RxQualSub Distribution

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TA Distribution

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

0

2000

4000

6000

8000

10000

12000

14000

16000

18000

20000

0 3 6 9 12 15 18 21 24 27 30 33 36 39 42 45 48 51 54 57 60 63

#

TA

TA Distribution

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TEMS Log files & Analyze

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TEMS LOG-FILE ANALYSIS

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Requirements

To analyze a log-file, the analyzer must have a complete know

how of the data collection.

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Things to Analyze Although there are many things to note during the log-file analysis but they

can be summarized under different topics:

Coverage Analysis

Quality Analysis

Handover Analysis

Drop Call Analysis

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Coverage

Analysis

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Coverage Analysis

Doing coverage analysis from log-files usually we come across following

problems:

Low Rx_Level

Lack of Dominant Server

Sudden Decrease in Rx_Level

Almost same Rx_Level

Drop call due to Bad Coverage

Access Failures

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Low Rx_Level In areas where there are few sites and too many different types of terrain structures like hills or obstacles those stopping the line of sight to the broadcasting signal, there might be a lot of coverage holes or places with insufficient signal level.

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Lack of Dominant Server

Signals of more than one cell can be reaching a spot with low level causing

ping pong handovers. This might happen because the MS is located on the

cell borders and there is no any best server to keep the call.

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Sudden Decrease in Rx_Level

Tunnel Effect:

Engineer may notice sudden decrease on signal level when analyzing the log

files. This will result in excessive number of

handovers. Before suspecting anything else, check if the test was performed

on a highway and that particular area was a tunnel or not. Signal level on

the chart will make a curve rather than unstable changes. Tunnel effect will

most likely result in ping pong handovers.

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Almost Same Rx_Level The network needs big optimization work when there are too many cells having overlapping

coverage. This will cause quality problems because of frequency reuse and immediate action to

optimize cell coverage should be taken. Other cells else than the one that suppose to serve at

that particular area should be coverage reduced by power reductions, down tilts or other

configuration changes.

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Drop Call due to Bad Coverage

Call is dropped because of poor coverage. The signal level goes down below

the minimum signal level that system could carry on. Remember this

minimum level is much lower than RX Access Minimum Level.

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Access Failures

Access failures can happen because of low level below ACCMIN, bad quality or blocking in the

target cell, or hardware failures. If you get a blocked call message during call set–up, it is

because the signal leveling the cell you are trying to make call set–up is below ACCMIN which

prevents MS to access the cell. ACCMIN is generally set to –104dBm depending on sensitivity

level of equipments and is referred during call set–up. A low value of ACCMIN means that the

coverage in idle mode is improved at the expense of the risk of having an increased number of

call set–up failures.

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Quality

Analysis

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Quality Analysis

While doing the quality analysis in a log-file, one comes across different

cases:

BER & FER

Bad Quality due to Signal Strength (FER is BAD)

Bad Quality due to Signal Strength (FER is OK)

SQI

Collusion of MA list causing low C/I

Interference

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BER & FER

BER Stands for Bit Error Rate

FER stands for Frame Erasure Ratio

The BER and FER caused by the radio network is the most important speech

quality degradation factors. The BER and frame erasure ratio (FER) are

dependent on a number of factors such as fading and interference. The

degradation can be minimized by using the radio network features DTX,

Power control and Frequency hopping.

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Bad Quality due to signal strength

(FER is BAD)

As the signal strength drops down, the quality of the call becomes worse being effected by

interference or fading or both. Consequently the system becomes weaker to handle the

interference. Notice that not only Rx Quality is bad, but also FER is high. SQI is still within

acceptable limits. That’s why we check all RX Quality, FER and SQI when analyzing interference

problems. System will face bad RX Quality, drop calls and ping pong handovers in such

environments.

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Bad Quality due to signal strength

(FER is OK)

The difference of this case from the previous is only the difference in FER. Signal strength is

also bad in this, but FER is still fine which means there is no obvious interference in the area.

The area in this case should most probably be a flat area without any obstacles to create

reflection and the site density should not be dense or re–use of frequencies is good to prevent

any co–channel interference.

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SQI

SQI, Speech Quality Index is another expression when Quality is concerned.

However, the RxQual measure is based on a simple transformation of the estimated average bit

error rate, and two calls having the same RxQual ratings can be perceived as having quite

different speech quality. One of the reasons for this is that there are other parameters than

the bit error rate that affects the perceived speech quality.

A short, very deep fading dip has a different effect on the speech than a constant low bit error

level, even if the average rate is the same.

The TEMS Speech Quality Index, which is an estimate of the perceived speech quality as

experienced by the mobile user, is based on handover events and on the bit error and frame

erasure distributions. Extensive listening tests on real GSM networks have been made to

identify what type of error situations cause poor speech quality. By using the results from the

listening tests and the full

information about the errors and their distributions, it is possible to produce the TEMS Speech

Quality Index. The Speech Quality Index is available every 0.5 second in TEMS and predicts the

instant speech quality in a phone call/radio–link in real–time.

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Collusion of MA list causing low C/I

The collusion of frequencies with neighboring cells MAIO list frequencies become

more significant with dropping signal level. To prevent this kind of interference,

MAIO lists of neighboring cells should be properly planned or MAIO step could be

used.

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Interference

There are two types interferences usually faced during the drive test:

Co-Channel Interference

Interference created by same frequencies is Co-Channel Interference. It is rarely

faced in any network.

Adjacent Channel Interference

Interference created by adjacent frequencies is called Adjacent Channel

Interference. There are few cases in any network regarding this kind of interference.

Interference can cause harm to network by creating drop calls, bad quality patches,

voice distortion etc.

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Interference

72

Hand Over

Analysis

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Hand Over Analysis

Hand Over contributes to one of the main KPIs in any network. Four main kinds of handovers take place in the networks:

Intra- Cell Handovers

Intra-BSC Handovers

Inter-BSC Handovers

Inter-MSC Handovers

All the above handovers do follow the HO algorithm. HO algorithm in different vendors systems or even in operators using the same equipment could be different. In TEMS following Layer-3 messages contribute to Handover.

Sys Info Type 5

Sys Info Type 6

Measurement Reports

Handover Command

Handover Access

Handover Complete

74

Hand Over Analysis

TYPES OF HANDOVER

Power Budget Handover (value depends upon PGBT HO Margin)

Level Handover (value set -95dBm for DL & -105dBm for UL)

Quality Handover (value set to 3.2% to 6.4% for both DL & UL)

Interference Handover (value set to -80dBm for both DL & UL)

Umbrella Handover (value set to -80 to -90dBm & PGBT Margin to max.)

MS distance Handover (value set to max. by default)

Intra-Cell Handover

Rapid Field Handover (value set to -110dBm by default)

Directed Retry Handover

75

Hand Over Analysis

Reasons for handover failure could be unavailable time slots because of high traffic,

congestion, low signal strength or bad quality on target cell. Handover can be failed because of

hardware problems in target cells –more likely TRX or time slot problems. Doing the HO

analysis, one faces the following problems:

Late Handovers

Ping-Pong Handovers

Missing Neighbor Relation

T3124 Expiry

Neighbor Cell in another BSC/MSC

76

Late Handovers There will be such cases that you will notice handover process taking place a little late. There could be couple of reasons to that. First thing to check will be handover margins between the neighbors. If margins for level, quality or power budget handovers are not set correctly, handover will not take place at the right time. If margins are too much, handover will happen late, vice versa. If umbrella handover is enabled between two neighbors, you will notice that the small site will still keep the traffic although the level of umbrella cell id too much higher. This is due to HO Level Umbrella RX Level which is set to some definite level.

77

Ping-Pong Handovers Ping-Pong Handovers take place due to following reasons:

• MS moving in Zig Zag direction between the cells.

• Incorrect HO Margins

• lack of dominancy

• Too many overlapping regions

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Missing Neighbor Relation

If a handover is not performed to a neighbor cell that seems to be best

server, there is a possibility of a missing neighbor relation. This will happen

with sudden appearance of strong cell in the neighbor list just after a

handover.

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T3124 Expiry

T3124 is the timer which is started when the Ho reference is sent in the HO

access burst. HO failure is faced when this timer is expired which means

that either the burst is not sent properly or not recognized at the other end.

Shown in the “Additional Information Message” in Mode Reports

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Neighbor Cell in another BSC/MSC

You will always observe handover problems in BSC borders, because neighbor relations in these cases need extra attention. When the neighbor is in another BSC, the neighbor needs to be defined as an external cell in neighboring BSC with correct CGI, BCCH, BSIC and power related parameters. This must also be like this on the other way to have a mutual neighbor relation. If the neighboring cell belongs to a different MSC, the cell needs to be defined as an outer cell in neighboring MSC with correct CGI and MSC name/address. This must also be like this on the other way to have a mutual neighbor relation.

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Drop Call

Analysis

82

Drop Call Analysis

If the radio link fails after the mobile sends the Service Connect Complete

Message then it is considered a dropped call. General reasons for drop calls

are as follows:

o Drop Call due to Low Signal Strength

o Drop Call due to Bad RX Quality

o Drop Call due to Not–happening Handover

o Drop Call due to Interference

83

Drop Call due to Low Signal Level

Low signal strength in any area can be a cause for the drop call. The signal

level goes down below the minimum signal level that system could carry on.

Remember this minimum level is much lower than RX Access Minimum Level

to prevent on–going call from dropping.

84

Drop Call due to Bad Rx quality

Sometimes the level is good or in the satisfactory range but the call is

dropped because of the degraded trend of Rx quality. The degradation in

this case is caused by the ping pong handovers between different cells.

85

Drop Call due to Not Happening Hand

Over

Sometimes the call is dropped due to not happening hand over. This case is

faced when there is problem in the neighbor definitions of any cell, BSC or

any MSC. The MS moves on & the cells other than the serving cell are not

properly defined as neighbors then the call will be dragged until it crosses

the max TA value & the call is dropped.

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Drop Call due to Interference

One of the reasons for the drop calls is interference also. It might be co-

channel & might be adjacent channel.

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Thanks

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