Dynamic PDTCH Preemption

All PDTCH(Except fixed ones) need to captured by Voice TCH when needed

Underlaid traffic is shifted to Overlaid and call dropped eventually when all channels are occupied by PDTCH and cannot be pre-empted

1. When the initial call receive level is > Threshold A  and all TCH channels are congestion at the same time, the call can occupy the UL or OL PDTCH.

2. When the initial call receive level is <= Threshold A , it can only use UL TCH channel, if UL TCHs are congestion, then it can only occupy the UL PDTCH.

useful document, thanks