Voice Drop Call Rate Vs EGPRS Mbytes

Z,

Are you sure the drop is corelated to the GPRS traffic ? What about CS Traffic ?
I would say that at the busy hour (CS and PS), then more radio frequencies are busy, therefore the quality of the air interface is degraded. That leads to higher call drop rate.

If that’s not the case, then let’s assume the GPRS traffic does indeed impact the CS drop. The only thing i can think about is how the capacity is distributed between CS and PS. Perhaps a CS call is trying to perform a HO towards a cell, but this cell can’t accept this incoming HO because all its resources are already occupied. And perhaps the PDCH are not released to make room for the incoming HO (this is a strategy which is vendor dependent).

In order to try out this method, try decreasing the max amount of pdch in the cells, and globally, try making the allocation of CS call more aggressive –> PDCH should be preempted faster.

What is the cause of drop?

During GPRS transfer, there is no DL Power control. So basically, the amount of interference increases in the network if there is too much PS Traffic.
UL Power Control is usually not activated neither, so same thing apply in UL as well.

Can you see an increase in the ratio of Quality HO, or Interference HO (especially downlink ?)

You said the GPRS UL PC made it worse. How can GPRS UL PC impact the CS Call drop ?!? GPRS PC and voice PC are different mechanisms, with different parameters.

You can check also something (this is vendor dependent): the PS traffic is perhaps enjoying the best TRXs of the cell (less interference, less hopping, … ?) while the CS traffic is set on the worst TRX ?