Hi Sheldon,
I can explain. We have made use of Flexi Abis plan. then we have kept the following parameter:
NUMREQEGPRSBPC=3
FPDCH=2
here we are not allocating a fixed PDCH. But the extra BPC will work as On Demand EGPRS timeslot supporting (64Kbps).
Normal On demand does not need any allocation but it supports only GPRS (16Kbps)
I have checked the PCU congestion, even that is not congested. But my SGSN utilization is around 98% in all BSC.