DT Parameters.pdf
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Transcript of DT Parameters.pdf
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Why perform a Drive test?
Every alive Network needs to be under continues
control to maintain/improve the performance. Optimization is basically the only way to keep track of
the network by looking deep into statistics andcollecting/analyzing drive test data.
Drive test helps operation and maintenance fortroubleshooting purposes.
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GSM Parameters
RxLevel
RxQuality Frame Erasure Rate ( FER )
Bit Error Rate ( BER )
Carrier to Interferer ( C/I )
Speech Quality Index ( SQI )
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RxLevel The power level corresponding to the average received
signal level of the downlink as measured by the mobilestation.
Normal Range is from -30 to 70.
Level lower than -70 shows low signal levels.
Amplifiers, New site proposal, Hardware check could
alter the low signal level.
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RxQuality The level corresponding to the mobile station's
perceived quality of the downlink signal.
Normal range is from 0 to 4. Quality higher than 4 can result in Call drops, Call
blocks, Muted calls, Handover failures, Interference.
Numerous alternatives could be used to make the
quality normal, which can include setting RFparameters from OMC.
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Frame Erasure Rate ( FER )A speech quality degrade factor that indicates fading
and interference.
Normally should be less than 4%. FER greater than 4% that degrades RxLevel, RxQuality,
BER, SQI and C/I indicates fading that leads to Calldrops, Call blocks, Muted calls and Handover failures.
FER plays a major role in troubleshooting ofInterference.
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Bit Error Rate ( BER ) The number of received bits that have been altered
due to noise, interference and distortion, divided bythe total number of transferred bits during a studiedtime interval.
For a perfect system, no bits are to be lost.
Loss of bits can result in fading and interference that
leads to Call drops, Call blocks, Muted calls andHandover failures.
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Carrier to Interferer ( C/ I ) Cochannel interference is the term used for
interference in a cell caused by carriers with the samefrequency present in other cells.
Normal Range of C/I should be greater than 12 dB.
Value lower than 12 dB indicates interference with acertain frequency that could be co-channel or adjacent
channel interference. Neighbor sites should be properly planned to
overcome interference problems.
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Speech Quality Index ( SQI ) SQI is an estimate of the perceived speech quality as
experienced by the mobile user, is based on handoverevents and on the bit error and frame erasuredistributions.
SQI should be greater than 18.
Low SQI indicates degraded speech quality and
interference. RF parameter tuning could level the SQI back to its
normal value.
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CDMA Parameters
RxLevel
TxPower Carrier Energy to Interference( Ec/Io )
Carrier to Interferer ( C/I )
Signal to Noise Ratio ( SNR )
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RxLevel The power level corresponding to the average received
signal level of the downlink as measured by the mobilestation.
Normal Range is from -30 to 80.
Level lower than -80 shows low signal levels.
New site proposal, Hardware check could alter the low
signal level.
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TxPower
Tx Power Control determines how the transmit power
of the receiving base station will vary. TxPower should be upto -20.
Value less than -20 will indicate Interference that canresult in Call drops, Call blocks, Voice breaks.
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Carrier Energy to Interference ( Ec/Io)
The ratio of received pilot energy, Ec, to total received
energy or the total power spectral density, Io. Ec/Io should be upto -13dB.
Values less than -13dB could be due to bad terrain,interference or increased number of users.
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Carrier to Interferer ( C/ I ) Cochannel interference is the term used for
interference in a cell caused by carriers with the samefrequency present in other cells.
Normal Range of C/I should be less than 12dB.
Value greater than 12 dB indicates interference with acertain frequency that results in a low throughput.
Neighbor sites should be properly planned toovercome interference problems.
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Signal to Noise Ratio ( SNR )
Signal to Noise ratio of the carrier.
SNR should be less than 6%.Values higher than that will result in low throughput,
voice quality breaks
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