We’re experience poor CSSR in some sites after BSC software upgrade. Strangely other sites within same BSC are OK. The issue is TCH Attempts increased and TCH assignment failure increased. SDCCH Assignment success is ok, the problem is on TCH Assignment, and it seems there’s a significant increase in incoming handovers and mostly they fail. HO Parameters and Neighbors are OK.No HW Alarms. What is this?
Same situation in our network (NSN vendor) after upgrade new BSC software. There’re no main changes on the KPI several hour after upgrade. But, the Tch assignment success rate on the BSC was degraded after this activity …
TCH Attempts increased because subcribers cannot make call so they keep trying. Therefore TCH Attempts and TCH Assignment failure both increase.
You can check if the TCH Assignment Preparation Fail due to BSS (HW) increase or not. If true, then some HWs or the BSC need resetting.
Did you strictly follow the upgrade procedure? Which vendor?