Analyzing the Effect of Soft Handover on Handover Performance Evaluation Metrics Under Load Condition

With increasing popularity of wireless local area network (WLAN) and emerging real-time applications, seamless mobility has become one of the primary concerns. Hence, the choice of a proper handover algorithm is of utmost importance. Various performance evaluation metrics for handover algorithms have been proposed in this regard. We argue that in a multiple access point (AP) scenario, the load on each of the APs, the requested data rate of the mobile terminal, and the soft handover have significant impact on these metrics. In this paper, we present an analytical framework to measure various handover performance evaluation metrics under both load condition and soft handover for a specific data rate request. Our approach is based on finding the circular region centered around an AP within which the requested data rate can be satisfied. We have considered WLAN usage efficiency, handover failure probability, and unnecessary handover probability as evaluation metrics. We have analyzed the impact of load and soft handover on these metrics. The impact of velocity on these metrics has also been analyzed. We also have derived lower bounds on both handover failure probability and unnecessary handover probability by formulating the problem into three circle intersection problem. The circular coverage assumption used in the framework is also validated through simulation.