For Siemens you not need fixed PDCH in case of EDGE.
EMANPRESPRM – EGPRS maximum Number of PDCH reserved Primary, this parameter defines the number of traffic channels reserved for EGPRS in the Primary Area.
During Cell Reselection or Routing Area Code update the data transmission is suspended for a few seconds. Solution is NACC. NACC could be Intra BSC or External (ENACCE – External Network Assisted Cell Change).
Do you reserved AGCH (NBLKACGR=1).