Research And Optimization On Media Access Control Protocol In Multi-Channel Wireless Mesh Networks

As the key technology for NGN, Wireless Mesh Networks (WMNs) has the capability of self-forming, self-healing, and self-organization.It can provide the access to Internet with high capacity and high speed. WMNs are attracting more and more attention from both industry and academia.The main work of this dissertation is focus on the MAC (Media Access Control,MAC) layer research in multi-channel WMNs.The details are following:Firstly, this dissertation introduces the research background and the process of industrialization and standardization of WMN. The network concept and topology structure are analyzed.Both the difficulty and solution in MAC protocol design are summarized.This dissertation also introduces the QoS (Quality of Service) guarantee mechanisms and application scenarios in WMN.Secondly, this dissertation provides the current study situation of MAC protocol in multi-channel WMN. The advantages and disadvantages of existing MAC protocol are given.This dissertation emphasizes Multi-channel Hyacinth architecture.The improvement of distributed channel assignment algorithm for Hyacinth architecture is also done in this dissertation.This new algorithm can improve network performance through assigning channels according to a dynamic period adapting to both network load and channel quality.Then, this dissertation designed the multi-channel MAC protocol EMMAC (Enhanced Multi-channel Media Access Control)guaranteeing QoS based on multi-channel protocol MMAC. EMMAC protocol can distinguish the priorities of different nodes and channels while assigning channels,in order to provide better user experience.EMMAC applies Common Channel Framework (CCF) to negotiate data transmission and RTS/CTS mode to negotiate media access,in order to avoid the impact of transmission collision and hiding station on network performance.The media access algorithm of EMMAC is the improved backoff algorithm, BEIED (Binary Exponential Backoff Algorithm) proposed in this dissertation.This is a simple and efficient method to resolve the unfairness while contending media and no QoS guarantee in BEB algorithm.The detailed frame format and handshake scheme are also illustrated.This dissertation applies two-dimension Markov chain model to demonstrate node behavior and channel access process with probability method.Also transmission delay and throughput are analyzed.Through the compare among traditional DCF, MMAC and EMMAC in multi-channel WMN, the performance superiority of EMMAC is proved.Finally, the work of this dissertation is summarized, and the follow-up work is explored.