Radio resource management for mobile WiMAX network

Abstract

Worldwide interoperability for Microwave Access (WiMAX) is one of the broadband wireless technologies that uses Orthogonal Frequency Division Multiple Access (OFDMA) and is anticipated to be a viable alternative to traditional wired broadband technique due to it is cost efficiency. It has been an emerging wireless broadband technology, in which the resources are limited. Thus, there is dramatic need to effectively manage the available resources and provide the necessary Quality of Service (QoS) for different traffic classes. Therefore, an effective admission control, scheduling and resource allocation are critical for the WiMAX network. The first contribution of this thesis is the development of link aware call admission control with service differentiation. The total link bandwidth is partitioned into portions such that each portion is dedicated to unique traffic. The amount of bandwidth dedicated to each portion is based on the probability mass function of the traffic arrival rate. A traffic can only be admitted when there is enough bandwidth in the portion allocated to that particular traffic. Firstly a two partitions call admission control is considered called dual partition call admission control. The scheme primarily partitioned the bandwidth into constant bit rate and variable bit rate traffics. Simulation result shows 63.63% increment in service flow acceptance and 21.42% reduction in blocking probability when compared to conventional call admission control. To accommodate handover services, partition base call admission control (PB CAC) is proposed. By allocating a third bandwidth portion for handover, service flow acceptance increased by 25%, with reduction of both blocking and dropping probability by 15.63% and 21.66% respectively. By using fuzzy logic in PB CAC, the dropping probability is reduced by 51.60%. The second contribution is the enhancement of the earliest deadline first (EDF) scheduling algorithm. The enhancement is based on the criterion for buffer selection in which the earliest deadline first scheduler should serve. The criterion for scheduling a packet depends on the queuing state and the QoS requirement of a particular service flow. The proposed algorithm utilizes link quality and is called link and queuing aware EDF scheduling algorithm (LQA-EDF). The modified algorithm outperformed the conventional EDF by about 5.77% in terms of throughput with fairness among service flows. The third contribution is the development of subcarrier and power allocation algorithm with aim of reducing the computational complexity. The allocation of subcarrier uses unsorted list technique by using biologically inspired algorithm which is based on particle swarm optimization. The power allocation employs the conventional water filling algorithm for optimal power distribution among users. The proposed technique has reduced the computational complexity by 31.2% compared to linear technique which uses sorted list and by 90.5% compared to root finding method.