CSSR

BSS CSSR = Immediate Assignment Success Rate x TCH Assignment Success Rate x (1 - SDCCH Drop Rate) x 100%

y Check Immediate Assignment Success Rate y Check Assignment Success Rate y Check SDCCH Drop Rate

DCR
TCH call drop rate (including handover) = Number of call drops on TCH/(Number of successful TCH seizures (signaling channel) + Number of successful TCH seizures (TCH) + Number of successful TCH Seizures in TCH handovers (TCH)) x 100% TCH call drop rate (excluding handover) = Number of call drops on TCH/Number of successful TCH seizures (TCH) x 100%
           

Hardware failure Transmission problem Version upgrade Parameter setting Intra-network and inter-network interference Coverage problem Antenna system problem Imbalance between uplink and downlink Repeater problem Swapping TRX Usibility Bad HOSR

Pareameter Setting 1. 2. 3. 4. 5. The parameters SACCH Multi-Frames and Radio Link Timeout are set to too small values. The parameter RXLEV_ACCESS_MIN is set to a too small value. The parameter RACH Min.Access Level is set to a too small value. The parameters Min DL Power on HO Candidate Cell and Min Access Level Offset are inappropriately set. The length of timer T3103 (this timer is set to wait for a Handover Complete message) is set to a too small value.

6. 7. 8. 9.

The length of timer T3109 (this timer is set to wait for a Release Indication message) is set to a too small value. The length of timer T3111 (this timer specifies the connection release delay) is set to a too small value. The length of timer T305/T308 is set to an invalid or too great value. The parameter TCH Traffic Busy Threshold is set to a too small value.

10. The parameter Call Reestablishment Forbidden is set to Yes. 11. The parameters related to edge handover are inappropriately set. 12. The parameters related to BQ handover are inappropriately set. 13. The parameters related to interference handover are inappropriately set. 14. The parameters related to concentric cell handover are inappropriately set. 15. The parameters related to power control are inappropriately set. 16. T200 and N200 are set to too small values. 17. Some neighboring cell relations are not configured. 18. The parameter MAIO is inappropriately set. 19. The parameter Disconnect Handover Protect Timer is set to a too small value. 20. The parameter TR1N is set to a too small value. 21. The parameters Software Parameter 13 and MAX TA are set to too small values. 22. DL Qual. Limit for AMR FR 23. UL Qual. Limit for AMR FR 24. DL Qual. Limit for AMR HR 25. UL Qual. Limit for AMR HR

If a repeater is used, the parameter Directly Magnifier Site Flag is set to No.

Traffic Balancing
 Assign-optimum-level Threshold  OtoU HO Received Level Threshold  UtoO HO Received Level Threshold

TCH Congestion rate

Seizure Requests x 100%

       

Network capacity and traffic distribution Faults occurred during equipment installation, transmission, or on the hardware Network interference KPI measurement problems Incorrect parameter settings Third-party device problems Software version problems Check LAC planning( on LAC boundary high pagging occur. So high PSR will gone to down and Blocking can occur.

Parameter check

1. 2. 3. 4. 5. 6. 7. 8. 9.

TCH Traffic Busy Threshold(%) is incorrectly set.

incorrectly set. Assignment Cell Load Judge Enable (BSC6000) is invalid. Directed Retry Load Access Threshold is invalid.
Balance Traffic Allowed is not set.

Load HO Allowed is not set. Load HO Step Period is set to a too great value. RACH Min.Access Level is set to a too small value. Cell reselection parameters are incorrectly set.

10. Cell Direct Try Forbidden Threshold (BSC6000) is incorrectly set. 11. Direct Retry is set to No. 12. SDCCH Dynamic Adjustment is invalid. 13. Flow control parameters are invalid. 14. Speech Version is incorrectly set.

SDCCH CONGESTION
SDCCH congestion rate = Failed SDCCH seizures due to busy SDCCH/Total requests for the SDCCH x 100%
SDCCH Blocking Rate = SDCCH Blocked Calls/ SDCCH Seizure Requests *100

y y y y

Check Equipment faulty and transmission Check Improper Data Configration Check Interference Check LAC planning( on LAC boundary high pagging occur. So high PSR will gone to down and Blocking can occur.

Parameter Setting y y y y y

SDCCH Availability LAC T3101 (the timer used in the immediate assignment procedure) T3212 (the timer used for periodic updating) range 0 to 255, we adjust 20. 1=6mins T3111 (The timer )

SDCCH DROP RATE

Hardware failure Transmission Version upgrade Parameter setting Intra-network and inter-network interference Poor Coverage Imbalance between uplink and downlink Hardware Faulty

Parameter Setting

1. SACCH Multi-Frames (SACCH period (480ms)) and Radio Link Timeout(SACCH period (480ms)) are set to too small values. 2. RACH Min.Access Level(dBm) is set to a too small value. 3. T200 SDCCH(5ms) and N200 of SDCCH are set to too small values.

4. MAIO is set improperly.

Path Imbalance
Antenna and feeder installation TMA installation Incorrect parameter settings Hardware fault Repeater Antenna matching problem MS user behavior Parameter Setting 1. MS_TXPWR_MAX_CCH

Problem handling started

When the fault is related to Immediate Assignment Success Rate, SDCCH Drop Rate or Assignment Success Rate

Start

Analysis of low immediate assignment success rate

Find cells with low immediate assignment success rate

Equipmen t fault?

Yes

Check TRX availability and TRX alarm

Check SDCCH availablity

Check number of SDCCH activation failures/timeout

TRX fault or transmission failure

Um interface fault? No

Ye s

Idle interference band/signaling analysis

TRX receive level and quality analysis

RACH overload times

Solve Interferenc e problem

Ye Insufficient system s capacity?

SDCCH seizure Normal success rate (location update)

SDCCH and TCH traffic volume analysis

Incoming and outgoing handovers of the cell

Replan the location areas

No

Abnorma l Traffic volume per SDCCH exceeds paln

Hardware expansion

MS fault?

Analyze signaling and traffic statistics of cells with problem

Enable CBA of the cell

For swapped network, check whether the problem exists in ventor's network

Locate problem and submit report

No Problem solved? Yes End

Check whether the BTS is an operational Huawei BTS

Possible cause analysis 1

Possible cause analysis 2

1. Check the hardware configuration

Coverage decrease is caused by combination loss due to capacity expansion? Configuration of neighboring cell relations is missing? Check for clock faults, radio link faults, intermittent disconnection, or TRX communication fault. Compare the drive test data before and after network swapping. If the coverage is normal, the BTS fault is excluded from the cause. Check antenna and feeder connections, connectors, combiner, and VSWR. Check whether the antenna is aging. Test the power on top of the cabinet. If the power and receive sensitivity are normal, exclude the BTS fault from the cause.

Check for TRX fault or TRX insufficiency, which may cause congestion and traffic volume decrease.

2. Check the parameter settings

Check the parameters: Cell Layer, Power Class, RACH Min.Access Level, RXLEV_ACCESS_MIN, and CRO.

3. Check the alarms and traffic statistics

Check whether congestion occurs and whether coverage is normal according to traffic statistics, and check the uplink and downlink receive quality.

4. Compare the drive test data

Communicate with the customer that makes complaints and conduct field tests to obtain the first-hand data.

5. Check the BTS antenna and feeder

Check whether the tilt or azimuth angle of the antenna changes , because the main and diversity of the BCCH omnidirectional antenna may change the coverage area, thus decreasing the traffic volume.

6. Test the power on top of the cabinet

Check whether additional losses are introduced, such as the additional jumpers, added TMA, and surge protector.

7. Find out other possible causes

Start

Are the uplink a downlink in balan the cell?

Check the connect the antenna and fee these cells.

Is there any problems antenna and feeder con

Check the param settings in this c

-Thanks & Regards Ashutosh Vats | RF Optimizer | Technical | Metro Wireless Engineering (India) Pvt. Ltd .| 309-310,Udyog Vihar, NearMTS, Phase IV, Gurgaon | Mobile: +91-8126412554, +8801755526518