Investigation On A QoS Based Queue Backoff Fair Scheduling For MANET

Mobile Ad Hoc Network (MANET) is a special multihop network without a centralized administration. Investigations on MANET have received considerable interest in recent years due to its capability to deploy quickly without any infrastructure. An efficient and effective Medium Access Control (MAC) protocol is essential as the shared channel is a scarce resource in mobile Ad hoc network. Moreover, because of the rising popularity of multimedia applications and potential commercial usage of MANET, QoS based MAC protocols have become a key issue for MANET. Therefore, the main goal of this thesis is to investigate a simple yet effective QoS based fair scheduling scheme in order to provide desired bandwidth distribution among different flows sharing the channel in mobile Ad hoc network environment.This thesis first reviews the characteristics of MANET and its related QoS based research fields. Afterwards, the thesis goes deep into the study of the fair scheduling issue in MANET, and then proposes a new fully distributed, simple yet effective Queue Backoff Weighted Fair scheduling algorithm, which can provide service differentiation of the traffic flows while achieving fair access to all mobile nodes.Focus on the limitations of the existing Fairness Index (FI), this thesis proposes an Improved Fairness Index (IFI). Based on 1FI, the optimization of channel access fairness relative to effective aggregate throughput is equivalent to minimization of the EFI.Analysis and computer simnlntion in Network Simulator 2 under Linux system have proved the correctness and the effectiveness of the algorithm. Several simulations were run under different scenarios (static and mobile environments) for different types of traffic (CBR/UDP and bursty traffic) in order to verify the performance of the proposed QBWF algorithm. Key metrics, such as throughput and channel utilization were used to measure the improvements and perform the analysis and simulation results.Analysis and simulation results show that, compared with the IEEE802.11 Binary Exponential Backoff (BEB) algorithm and other algorithms that have been employed to address the fairness problem, the proposed QBWF algorithm is simpler and practical. Also, by choosing appropriate parameters, the QBWF algorithm can effectively improve the channel access fairness and achieve a preferable trade-off between fairness and throughput. In addition, service differentiation can be achieved among flows with different QoS requirements and thus the QoS for Medium Access Control in mobile Ad hoc network is improved.Finally, the thesis concludes by summarizing the main contributions of the research and by presenting directions for future work.