High SDCCH Blocking Statistical Analysis

SDCCH Blocking is a critical KPI that depicts the quality of optimization in a network as this KPI is mostlty controlled via soft optimization. The considerations for maintaining this KPI are as follows:

1. SDCCH/TCH Availability %
1. Many times, the SDCCH traffic is enough to be carried in defined channels, but still the blocking is high. This could be mostly due to momentary surge in traffic or site fluctutation causing blocks for a small portion of an hour, thereby averaging the traffic/availability in the hour.
2. SDCCH Drops
1. TA Analysis
2. Interference (Co/Adjacent)
3. TCH Congestion
4. Equipment Failure
5. Low output power
3. SDCCH Channels/Traffic/Blocking (Erlang Table)
1. SDCCH Addition (Static/Dynamic)
2. SDCCH/TCH Conversion Timer
3. Maximum SDCCH Channels Threshold
4. Penalty Timer (Set PT = 31 of cell)
5. Increase CRH (Cell Reselect Hysteresis) if cell is on LAC Boundary
6. Directed Retry (Forced)

High TCH Blocking Cell Statistical Analysis

Below mentioned procedure should be adopted in general to resolve the TCH blocking issue:

1. Check TCH Availability % (Cell/Neighbours)
2. HRU % (Half Rate Utilization)
1. If HRU = 0; Enable HR
2. If HRU > 0; Tune HR Thresholds
3. TA Analysis (TA Distribution)
4. Traffic Balancing
1. CRO (Cell Reselect Offset) Adjustment (reduce in Cell/Increase in Neighbours)
2. Penalty Timer
3. Traffic Handover
4. Downtilt
5. Neighbour Audit
6. Propose TRX/Sector/Site Addition

Low HSR Cell Statistical Analysis

Following statistics should be checked for low HOSR Cell Analysis:

1. IHSR %
2. HOSR %
3. IBI % (Band 4+5)
4. TRX Efficiency
5. Hardware Alarms (Clock Reference, PCM/SUMA Issue)
6. Neighbour Definitions
7. Handover Stats per adjacency (Attempts, Success, Fails)
8. Handover Parameters (Margins, Priority)
9. Handover distribution
10. TA distribution

High DCR Cell Statistical Analysis

Following statistics trend (say 2 weeks) should be checked for high DCR Cell:

1. TRX Efficiency %
2. Equipment Failure Drops (RTC/BSS/Abis/Equipment Failure etc)
3. Incoming Handover Success Rate (IHSR)
4. Handover Failures
5. IBI % (Band 4+5)
6. Handover Drops
7. Radio Drops
8. UL/DL Level Drops
9. UL/DL Quality Drops
10. TA (Timing Advance) Drops
11. TA Distribution
12. Handover Distribution
13. RxQual Rank/Index (Mean Quality of UL/DL Signals)
14. Delta Path Loss (Path Imbalance)

KPIs Thresholds

What should be the values of network KPIs to be considered as degraded? Different operators have their own targets and it varies greatly depending upon vendor SLA (Service Level Agreement), Terrain (Plain/ Hilly/), Urban/Rural Area etc. However general idea is presented below:

• DCR % (Dropped Call Rate) < 1-2%
• HOSR % (Handover Success Rate) > 95-98%
• TCH Blocking % < 2% (GoS Standard)
• SDCCH Blocking % < 0.1%
• TRX Efficiency % (TCH Seizures/TCH Call Attempts X 100) > 90-99%
• IBI % (Band 4+5) < 1%

Major KPIs

The major KPIs that need to be monitored on daily basis on BSC/Cell/TRX level in a network are:

1. DCR  % (Dropped Call Rate)
2. HOSR % (Handover Success Rate)
3. TCH Blocking %
4. SDCCH Blocking %
5. TRX Efficiency % (TCH Seizures/TCH Call Attempts X 100)
6. IBI % (Band 4+5)