Gsm bss network kpi (sdcch congestion Rate) Optimization Manual

Cause	BSC-Level
TRX-Level
Interference	None.	Interference band measurement per TRX AS4200A:Mean Number of SDCCHs in Interference Band 1 AS4200B: Mean Number of SDCCHs in Interference Band 2 AS4200C: Mean Number of SDCCHs in Interference Band 3 AS4200D: Mean Number of SDCCHs in Interference Band 4 AS4200E: Mean Number of SDCCHs in Interference Band 5 S4350D: Radio Link Failures (SDCCH)

4Test Method

The SDCCH congestion rate is one of the KPIs, which can be obtained through the registration or reporting of the related KPIs. Generally, SDCCH congestion rate is not measured through drive tests because of the limited samples, incomplete test routes, and the irregular occurrence of the congestion in areas with low traffic.
At present, the vendors and mobile operators use different formulas to calculate the SDCCH congestion rate, thus leading to different values of this counter. In actual measurement, you should register the specific counters and use an appropriate formula to calculate the value of the counter.

5Case Analysis of SDCCH Congestion Rate

5.1Congestion Caused by Improper Configuration of Power

Description
The engineers observe the status of each board of the BTS3001C-204 (configured with two omni-directional antennas) on the LMT and find that they are in normal state. The traffic measurement results, however, show that the congestion rate in this BTS is high (13%). Then the engineers observe the status of the TCH and find that the TCH of TRX1 is idle whereas the TCH and SDCCH of TRX0 are busy.
Alarm Information
None.
[Cause Analysis]
The possible reason is that the output power of TRX1 is small and is not detected by the BTS3001C.Most MSs are not assigned a TCH of TRX1 successfully except those close to the BTS. This causes the SDCCH to be occupied for a long time, thus leading to the SDCCH congestion.
Handling Procedure
a. Block the TCHs of TRX1, and the SDCCH counters are normal.
b. Use a power meter to measure the output power of TRX1 and TRX0. The result shows that the output power of TRX1 is very small but that of TRX0 is normal.
c. Replace the BTS and all counters are normal.