Abstract:
Achieving seamless homogeneous handover in mobile WiMAX due to its low cost and state of the art technology will enable ubiquitous broadband access to high volume applications especially with the high global increase in mobile subscribers. Extending this seamless handover across network technologies-heterogeneous handover- like WiFi will further lower cost, improve battery life and enable high productivity for end users. In this project, ways of optimizing handover in mobile WiMAX network, and the design and evaluation of system-level performance of different select handover scenarios were analyzed. Modeled voice application on a mobile node at pedestrian and vehicular speeds was used for the analysis with the media independent handover (MIH) network simulator 2 (NS-2) as simulation tool. MATLAB-based Trace Graph and Microsoft excel were used as the MAC layer packet-level analysis tools. The average handover delay from the simulation result is found to be 46 msec in all the simulation which fell below the WiMAX forum’s recommended handover delay of 150 msec for VoIP. The average handover jitter of 47msec also fell under the standard value of 50 msec. It was determined that the heterogeneous handover to WiFi network has acceptable throughput, delay, latency with no packet lost for voice packets. However, there were significant drop in throughput observed during WiMAX handover periods with highest drop of 5 packets/sec from 50 packets/sec at normal operation. This is due to packet loss caused by Doppler spread at vehicular speed and low SINR (signal-to-interference noise) at non overlapping cells and large base station distances. These throughput drops can be mitigated by appropriate channel modelling, adaptive sampling of Orthogonal Frequency Division Multiplexing (OFDM) symbols at high speed, antenna diversity, and also by making sure that all cells overlap during base station deployments.
