All measurements can be saved to log files where they are time stamped and positioned geographically (latitude and longitude collected from GPS). Data up to 4 mobiles and a scanner can be logged simultaneously. Using command sequence, various tests can be automated. Log files can be exported as user defined tab-delimited text or other format.
Drive-test tools are used to measure Network Coverage, Capacity, Quality and different RF parameters
RF Coverage
Coverage holes
• Antenna positioning
• Antenna Tilt
• Handover
• Power settings
• Indoor coverage
• Micro cells RF Quality
Dropped calls
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Drive tool captures all information sending from BCCH channel
Information on BCCH identifies the network and cell 1. Occupies Time Slot 0
2. Cell ID, MCC, MNC
3. Neighbours, hop sequences, paging information
4. All timeslots on the BCH ARFCN are always on with the max power.
With Frequency Re-use, also need BSIC to assist in identifying the cell Base Station Identity Code
Base Station Identity Code
• Part of the BCH
• Coded into the synchronization burst
• Two octal digits (value 0 to 7)
• Broadcast Colour Code (BCC)
• National Colour Code (NCC)
BSIC discriminates re-use cells within the network and between other networks
Idle Mode Measurement updates Serving Cell
• Running average of 5 measurement samples per Rxlev value.
• Measurement samples collected over a period of : = 5 secs to Max ( 5s, five consecutive paging blocks of that MS)
• This period can range between 5secs to 10.5 secs, depending upon the paging repetition rate parameter settings.
Neighbour Cells
• Running average of 5 measurement samples per Rxlev value of each neighbour cell.
• Measurement samples should be collected over a period of :
= 5 secs to Max [ 5s, (5*N + 6) DIV 7) * BS_PA_MFRMS / 4 ]
N is the number of non-serving cell BCCH carriers in the BA list (max 32)
• BSIC for the same the Neighbour cell ARFCN is verified every 20 secs
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C1 measurement
C1 is the path loss criterion, which is used to estimate the balance between uplink and downlink
• Mobile camps on to a cell where C1 is the maximum
• Mobile in idle mode will at regular intervals carry out C1 measurements for both serving cell and Top 6 neighbour cells.
• Mobile will do a cell reselection to a neighbour whose C1 exceeds the C1 of the server
• Mobile will provided addition hysteresis value to be added to the C1 of the server when the neighbour is in different LAC
C1 Calculations C1 = A - max ( B,0 )
A = Average Received signal Level - Min Receive Level B = Access Power - Max power of Mobile ( Classmark ) A = + = Good Downlink Path
B = -- = Good Uplink Path ---For Cell selection C1 > 0
---For Cell Reselection C1 of new cell > C1 of current cell or C1 falls below 0, both for a period of 5 seconds.
C2 Measurements
CELL_RESELECT_OFFSET : ( 0 - 126 dB // 2 dB steps )
Positive or a negative offsets applied to cells permanently over C1 Used for prioritazation in cell reselection ( ex: umbrella cells) TEMPORARY_OFFSET : ( 0 - 60 dB // 10 dB steps)
Negative offset applied to a neighbor cell whose C1 exceeds C1 of server Offset remains valid for a timer duration
Used for optimizing frequent cell reselections.
PENALTY_TIME : ( 20s to 620s // 20secs steps)
The duration for which the Temporary_Offset is applied.
•C2 measurements are optionally used to optimize and prioritize cell reselections.
•Additional parameters are broadcasted to the Mobile, which are implemented over C1 calculations.
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Phone Measurement Report
Rxlev
• During reception of burst for serving cell
• Minimum one neighbor cell measured in 1 frame RxQual
• BER measurements carried over 26 bits of midamble
• Ranges between 0 - 7 ( 0 indicates no errors ) Full and Sub
Rxlev_Full&RxQual_Full: Measurements taken over full set of TDMA frames Full set of TDMA frames : 102 for SDCCH Full set of TDMA frames : 104 TCH
Rxlev_Sub&RxQual_Sub: Measurements taken over subset of TDMA frames
If even one frame is not transmitted in the measurement period, then it is considered as subset of TDMA frames
When do we practically consider sub?
• When DTX used, and the receiver enters the DTX mode, then the measurement done over all the frames is not valid.
• With DTX, if there is completely no speech for 480ms, then still there will be 8 frames of SID and 4 frames of SACCH, these 12 subset frames will be used for sub measurements.
• DTX is not used on BCCH carrier (all timeslots), hence if the call is on a TCH timeslot which is on a BCH carrier, then it will always be FULL, and in the measurement report both Sub and Full values will be same.
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• DTX is not used on the SDCCH also, hence the above clause applies to this also.
• On a TCH carrier, when DTX was used by the BTS in the previous 480ms period, measurement is Sub, else it is full.
• If Frequency Hopping was used, and BCH carrier was a part of it, and downlink power control is used, then the Rxlev measurements will always be sub ( since BCH carrier frames are not included in the Rxlev measurement averaging), but RxQual will be full.
Radio Link Counter
Under what conditions will this decrement -- Poor RF link (Rxlev and RxQual) -- Interference
-- Uplink Problems!!!!
Frame Erasure Rate (FER)
3 bits CRC is added to the dedicated channels and on Type 1a bits of speech, in the coding process
• If the CRC detection at the Mobile is invalid, it indicates a Bad frame and FER counter goes up. • The effect perceived by the user is a “Ping-Pong” sound.
• FER is very useful to estimate quality under frequency hopping conditions, when Rxqual is bursty.
• Under Frequency Hopping condition, Rxqual does not resemble a true picture of quality, FER is the preferred parameter.
• Since only 3 bits are used for CRC, the probability of detecting bad frames is only 12.5%
• How do we measure FER %?
• % of speech frames erased over last 4 measurement periods
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Call Control Messages (CM)
Manages functions for circuit switched call control
• Alerting
Mobility Management Messaging (MM) Manages who you are and where you are
• Location Update Requesting
Radio Resource Messaging (RR)
Controls How the Air Interface is Managed Channel Assignments & Releases Handovers
The following Info Messages are broadcasted by BCCH channel
Interference
Interference in GSM systems are classified into three major categories:-
Co-channel interference
Adjacent channel interference
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External interference
Performance Monitoring Measurement Voice (Statistical and Geographical) –
Call Success Rate
Call Drop Rate
Handover Success Rate
No Service
Percentage Quality
Percentage Coverage
Percentage Interference
Cell footprint
Handover footprint
Q.A Drive Process Suggestion
Routes should be predefined
Test plans should be preset
Drive Duration and Time of Day should be pre-planned
Peak Traffic Hours should be used for QA test
Markers and Notes should be used
Data should be preferably binned
Use Analysis Reporter to get quick shot QA performance Report
Thresholds should be standardized
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KPI – QA – TEST Call Performance
Blocked Call Rate
Dropped Call Rate
Handover Failures Coverage
RF Idle Mode Coverage (Rxlev_Full)
RF Receiver Based Coverage (Top N Power)
Service Coverage (C/I In Idle Mode)
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Interference Reduction (or shift???)
Power Settings, Antenna Tilts, Antenna height change, Frequency Parameters
Coverage Holes
Adequate Coverage to Hot Spots, Indoor
Capacity Balancing
Cell configuration, Power, Antenna
Optimization Challenges
Optimization in most cases is of two types:- Overall: Done over a wide geography Selected: Done over a selected problem area
For overall , drive test is done over a large area for verification
For selected, drive test is done over the selected area, where optimization work was done, but the problems (specific to frequency related) gets shifted to other areas. So it should be taken care specially.
Pre Optimization Drive test data is generally derived from QA Drive test itself
Post Optimization Drive test can also be undertaken by QA team in a selected zone.
Different types of drive test carried out in different scenarios
Road drive test (high road, main road and small streets)
Cluster drive test
Customer complaints based drive test
Poor KPI of the site based drive test
Railway drive test
New site optimization drive test
TRAI drive test
Different Types of Drive Tools were supplied in Different Phase in Eastern Zone--- 1. Agilent Drive Test Tools---PH IV
2. TEMS Drive Test Tools---PH V 3. NEMO Drive Test Tools---PH VII
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2G sites down count – number of sites down due to transmission and other reasons ,
3G sites down count – number of sites down due to transmission and other reasons ,
Number of Sites (2G and 3G) down more than 3 days.
Any Network Elements Failure in Core or RAN which effects Traffic directly.
Per day revenue from prepaid ,
VLR count ,
Active customer of postpaid ,
Active customer of prepaid ,
GP1 and GP2 customer count ,
Addition / Deletion of the customers ,
2G voice traffic whole day (Erlang) from BSC level,
3G voice traffic whole day (Erlang) from RNC level ,
2G data traffic whole day (GB) from SGSN level,
2G Max Throughput(Mbps) from SGSN level ,
3G data traffic whole day (GB)from SGSN level ,
3G Max Throughput(Mbps) from SGSN level ,
Total Numbers of HW Fault, VSWR and Tx Fluctuation effect KPI.
2G KPI :
Number of sector with Call Drop > 2% and 3%
Number of sector with TchBlk> 2%
Number of sector with SdcchBlk>1%
Number of sector with CSSR<95%
9.2 On monthly basis
2G network availability , downtime and number of worst affected BTS,
3G network availability ,downtime and number of worst affected NodeB,
Number of New sites (2G &3G) addition in Network.
Number of Closed sites (2G &3G) in Network
Total revenue from prepaid and postpaid ,
Addition / Deletion of the customers ,
MNP ratio
Change of VLR count w.r.t previous month ,
2G voice traffic whole month (Erlang) from BSC level,
3G voice traffic whole month (Erlang) from RNC level ,
2G data traffic whole month (GB) from SGSN level
2G Max Throughput(Mbps) from SGSN level ,
3G data traffic whole month (GB)from SGSN level ,