dt post processing

UCE Telecom Solutions Ltd. UCE Confidential Documents

Post Processing & Log files Analysis in GSM


Drive testing is the most common and maybe the best way to analyze Network performance by means of coverage evaluation, system availability, network capacity, network retainibility and call quality. Although it gives idea only on downlink side of the process, it provides huge perspective to the service provider about what’s happening with a subscriber point of view.

The drive testing is basically collecting measurement data with a TEMS phone, but the main concern is the analysis and evaluation part that is done after competition of the test. Remember that you are always asked to perform a drive test for not only showing the problems, but alsoexplaining them and providing useful recommendations to correct them.


Drive testing is principally applied in both the planning and optimization 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.► To provide the initial test parameters used in Benchmarking.► 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.


► 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 windstorm or electrical storms.

► To monitor the performance of a competitor’s network.


Some areas of a network will have greater performance problems than others. Drive testing should not be regular 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. Sometime operators can perform drive test for their customarycheck for a certain city or some specific clusters of a city.


Drive test can be performed in very many ways. Different types of drive test fulfill different types of requirement from the customer.

► Single site Drive Test► Cluster Drive Test► Acceptance Drive Test► Site Swapping Drive Test► Benchmarking Drive Test► Functionality Test► Walk Test for IBS


►TEMS Investigation Data Collection.►Nemo.►Agilent.►Genex Prov.►Pilot Pananuma ect….


►TEMS Investigation Route Analysis.►MapInfo.►MCOM.►Actix Spotlight Analyzer.►Nemo.►Ranopt.►LDAT.►TEMS Desk Cat. Etc….


► Plotting RX Level and Quality Information for overall picture of the driven area.► Analyzing Network feature performance after new implementations.► Transferring comments on parameter implementations after new changes.►Analyzing all Log files.►Analyzing HO Failure.►Analyzing Dropped call.►Analyzing Poor Rx Level & Rx Quality.►Analyzing Interference Level.►Analyzing Blocked Call.


► Defining missing neighbor relations.► Proposing new sites or sector additions with Before & After coverage plots.► Proposing antenna azimuth changes.► Proposing antenna tilt changes.► Proposing antenna type changes.► Pre-Planning of interfered frequencies.► BSIC changes.► Adjusting Handover margins (Power Budget, Level, Quality, Umbrella HOs).►Adjusting Idle Mode Parameter(CRO,CRH).► Adjusting accessibility parameters (RX Lev Acc Min, etc..)► Changing power parameters► TMA adds


RxLevel_Before Rectification RxLevel_After Rectification

Cell Name BSC Type Parameter Name Old value New value Modification Reason

application time applicant Approved?

[Y/N]SYSIB3B SYHBS172 Physical Parameter Antenna Uptilt (Elect) [900

band] 6 4 To improve RxLev

28-Jan-10 Razzaque Y

SYARA1A SYHBS172 Physical Parameter Antenna Uptilt (Elect) [900 band] 7 6 To improve

RxLev28-Jan-10 Razzaque Y

SYSIB3B SYHBS172 Physical Parameter Antenna Uptilt (Elect) [1800 band] 6 4 To improve

RxLevel31-Jan-10 Razzaque Y

SYARA1A SYHBS172 Physical Parameter Antenna Uptilt (Elect) [1800 band] 7 6 To improve



RxLevel_Before Rectification RxLevel_After RectificationCell Name BSC Type Parameter Name Old value New value Modification

Reasonapplication

time applicant Approved? [Y/N]

SYKJS1C SYHBS172 Physical Parameter Antenna Uptilt (Elect) [900 band] 6 5 To improve


SYKJS1C SYHBS172 Physical Parameter Antenna Azimuth (Elect) [900 band] 240 230 To improve


SYKHP1C SYHBS172 Physical Parameter Antenna Uptilt (Elect) [900 band] 6 4 To improve









Possible reasons for interference problems in a cellular network could be:

• External interference• Bad or too tight frequency plan• Dragged Calls due to missing neighbor relations and congestion• Antenna positions and/or antenna type• HW problems• Incorrect parameter settings


We already know ….

Co-Channel Interference

•BCH - BCH•TCH - BCH•BCH - TCH•TCH - TCH

C/I Value is= 12dB without frequency hopping and 9 dBwith frequency hopping.

Adjacent Channel Interference

•BCH - BCH•TCH - BCH•BCH - TCH•TCH - TCH•C/A Value is= –9dB

Multipath


•Real Time Measurements with Interference Analyzer•Secondary BSIC decode ( with specific level limitations)•Primary - Interference includes Multipath also•Discriminate between Multipath and Co_Channel by using :

-- Secondary BSIC -- Measurement Status-- Delay Spread Chart

BCH - BCH

TCH - BCH

•Real Time Measurements with Interference Analyzer•No Secondary BSIC decode•Identify TCH as the source by using

Measurement Status - NO FCH


•TCH -TCH interference will be dominant when two TCH slots in both the re-use cells come in synch and they are ON.•Viper cannot measure interference on any Non-BCH carrier. So we need to take the intrusive approach. •Change the Frequencies and then measure, but this will also not be effective since TCH carrier is active only when call is on.•The most effective way is to measure the delta of the BCH carriers, since propagation will remain almost the same for both the BCH and TCH carriers, so if we measure ratio of F1/F9 in C2 , we can correlate this to the ratio of F5/F5 , there may be some difference with the practical values, since multipath effects are frequency dependent.

C1 C2

F1 F9

F5 F5

F1 & F9 : BCHF5 : TCH


Handover is a key function in a GSM network. If the handover performance is bad the subscribers will perceive the quality of the network as bad.

Possible reasons for handover problems in a cellular network could be:

• TCH congestion• Parameter settings• HW problems• Interference• Poor coverage• Missing neighbor cell relations or missing measurement frequencies• Incorrect Inter-MSC handover definitions• Incorrect Inter BSC Handover definitions


►Fault Description:

Some Customer complain in this area. There are many HO failure of that area. We performed DT & also found some HO failure in that area.


► Analysis

HO Failure due to CO-BCCH interference of source cell GPTONKC(BCCH-103) & Target Cell DHUTA8A(BCCH-103).

.► Solutions: Change BCCH of cell DHUTA8A from 103 to 101.



Some Customer complain in this area. There are many HO failure of that area. We performed DT & also found some HO failure in that area.


► Analysis

Handover Failure due to missing neighbour..

► Solutions: Make HO relation between cell DHFRM1C & DHKRB3C.


The retainibility performance evaluates the systems ability to handle established connections. Dropped calls are probably the single most important quality item to control in the system. The level of dropped calls in the system is in high extent depending on the initial RF planning, optimization and also the system growth.


Possible reasons for a high rate of dropped calls could be:

• TCH Congestion• Parameter Settings• HW problems• Interference• Poor signal strength• Missing cell relations and/or missing measurement frequencies• Bad quality• Sudden loss of connection (only TCH)• Excessive timing advance• Other


►SDCCH Drops – Cause -Coverage -Interference & Multipath -BTS performance

► TCH Drops – Causes -Coverage -Interference & Multipath -BTS performance -Pre-emption

► Handover Failure – Causes -Threshold parameters -Missing neighbors

► Solutions to Dropped Calls◦ Optimize Coverage◦ Interference Management◦ Optimize neighbors◦ Optimize handover

parameters◦ Effective Frequency

Hopping◦ Use of DTX & Power

control


► Poor Speech Quality could be due to •Patchy Coverage ( holes)•No Target cell for Handover•Echo , Audio holes, Voice Clipping•Interference ---:

•Co-channel•Adjacent channel•External•Multipath•Noise



Rx Quality is Bad


► Analysis

Poor quality due to co BCCH interference between cell DHFRM3C (BCCH-111) & DHFRM9C(BCCH-111) both are neighbors.

.

► Solutions: Change BCCH of cell DHFRM3C from 111 to 113.


RxLevel_Before Rectification RxLevel_After Rectification

Cell Name BSC Type Parameter Name Old value New value Modification Reason

application time applicant Approved?

[Y/N]SYKJS1C SYHBS172 Physical Parameter Antenna Uptilt (Elect) [900

band] 6 5 To improve RxLev

28-Jan-10 Razzaque Y












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