The effect of handover quality on buffering requirements in WATM

In order to maintain quality of service (QoS) guarantees during a wireless ATM handover, the cell stream must be buffered while a new connection is established. Once handoff is complete, the buffers can be emptied and normal transmission resumes. This prevents cell loss but can introduce cell delay variation (CDV) which is detrimental to real time and delay sensitive services. Additional flow control buffers can overcome this; however, the quality of the handoff will greatly affect the loading on these buffers. In this paper a lossless handover method is analysed using the Opnet simulation tool, varying qualities of handoff are modelled and the buffer loading is measured. Practical data gathered using a 5 GHz variable rate modem is included in the model to provide radio performance characteristics and allow cell retransmission rates and other factors that will affect the handover to be incorporated. The results from the Opnet simulation are presented including cell delay and delay variation, utilisation and loading of buffers and handover efficiency.