Context Aware Handover for WiFi and Its Extension to WiMAX

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IEEE 802.11 or Fidelity has become a popular wireless technology to offer high speed Internet access at public places called the as well as to support ubiquitous Internet connectivity through institute wide wireless local area networks (WLANs). However, existing researches has shown that due to wide-spread deployments of WiFi based network connectivity zones, more numbers of wireless access points (APs) are deployed than requirements, however, users tend to concentrate at few areas making traffic load imbalance across the network. The design philosophy of IEEE 802.11 connection establishment and handover from one AP to another is based on signal strength which is biased towards the distance between the AP and the client nodes. Severe performance and quality of service (QoS) degradation and capacity underutilization are observed due to this imbalance traffic distribution, which is the main concern of research in this thesis. The first contribution of the thesis explores the inherent problems of IEEE 802.11 handover management policies, and proposes a context-aware handover mechanism to balance traffic load across the network. The proposed mechanism works in coordination of information exchange between the AP and the wireless client that experiences performance degradation due to traffic overload at its present point of attachment. This coordination helps the wireless client to perform a horizontal handover to another AP in the vicinity, that significantly improves the network capacity. The performance of the proposed context aware handover mechanism is analyzed using theoretical analysis as well as from practical testbed results. The second contribution of the thesis extends the context aware handover to incorporate multiple traffic classes, where different traffic classes require different amount of bandwidth to sustain for acceptable quality of experience (QoE) to the end users. Consequently, a class aware load balancing is designed to reserve traffic resources a prior when an impending handover is observed.
Supervisor: Sukumar Nandi