Below mentioned parameters may cause TCH Congestion & also help you to reduce TCH Congestion:

1. TCH Traffic Busy Threshold(%)
2. RXLEV_ACCESS_MIN
3. SACCH Multi-Frames and Radio Link Timeout
4. SDCCH Dynamic Adjustment
5. RACH Min.Access Level
6. Speech Version
7. TCH Immediate Assignment
8. Speech Version
9. Fix Abis Prior Choose Abis Load Threshold
10. Assignment Cell Load Judge Enable
11. Flex Abis Prior Choose Abis Load Threshold
12. Directed Retry Load Access Threshold
13. Balance Traffic Allowed
14. Load HO Allowed
15. Load HO Step Period
16. Load HO Step Level
17. Cell Direct Try Forbidden Threshold
18. Direct Retry
19. SDCCH Dynamic Adjustment
20. Direct Retry and Cell Direct Try Forbidden Threshold
21. AMR TCH/H Prior Allowed
22. T3103
23. T3107
24. F2H HO th/ H2F HO th
25. Maximum Ratio Threshold of PDTCH