Topics: Drop, Trigraph Pages: 3 (556 words) Published: January 26, 2014
Factor Affecting SDCCH Drop
Double-Access /Multiple reservations due to co-Bsic, co-BCCH. Check and improve frequency plan.
RACH retransmissions/Multiple reservations due to bad coverage or interference and high numberOfRachRetransmissions. Lower RACH retransmission parameter value. Check and improve frequency plan and/or downtilt. FM:

Check alarms
RACH retransmission parameter value
Check Frequency plan
BTS is not declared in MSC
RxQuality report
TA report
Interference statistics

Radio Fails
Check alarms and RxQuality report to verify whether there is a badly functioning TRX. Fix hardware problem. Check antenna line.

Coverage. Verify TA report and planning tool.
Interference. Check Frequency Plan. Solution e.g. add sites, down tilt antennas, increase RxLevAccessMin. Extended coverage of cells in location area borders. Check LU parameters and/or downtilt 100% ABIS Fails

Failure in BTS software (BCSU reset in BSC).
100% AIF Fails
BTS connected to other BSC or BTS is not declared in MSC.

Check the High SD drop Cells from the BSS KPI reports
Look into the Drop Reason whether it is due to RF fail or any HW reason or any Signaling issue .If HW, site fluctuation or Signaling issue escalate the same to O&M/OMC team for rectification Check the proper A-bis link PCM mapping and signaling channel definition thro OMC engineer. Look into the coverage foot print of the same thro TA report and the site Data base if the cell is overshooting to longer distances optimize the same . If SD is configured in BCH carrier then look for the C/I condition for the BCH carrier looking into the reuse patterns. If SD is configured in Hopping TRX then look into the TRX performance and bad samples in that TRX and check the VSWR/Antenna /Combiner connections to the TRX .U can get a hint if you look at the assignment success ration of the cell. Look into the Quality samples in the TRX in which the SD is configured if...
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