Wireless Mesh Network Media Access Control And Routing Protocols Research

In recent years, with the tremendous development in wireless technology, wireless network has been widely applied. More and more people expect easy-to-access quality wireless communication. There is an increasing demand for services that need high bandwidth support and QoS guarantee, such as video transmission, which pushes forward the technical innovation of wireless access networks.Wireless mesh network (WMN) is a new broadband wireless network framework. It is a multi-hop network formed by peer-to-peer backbone nodes. Because of the short distance within one hop, nodes in WMN can transmit with lower power and higher bandwidth can be achieved, which reduce the cost. Because of its robustness, easy deploy, wider network coverage, larger network capacity, and lower early phrase investment, WMN is advanced to the traditional wireless networks. It is particularly suitable for broadband wireless access backbone networks. WMN has drawn the attentions form both the world of academy and the world of engineering, thus becoming a hot technology. WMN will definitely become an essential part of the Internet of the next generation.In WMN, multiple channel allocation strategies, MAC protocols, and routing protocols are very important issues. High effective channel allocation strategies can take full advantage of the limited channel resources and highly enhance the network throughput. The MAC protocol that effectively supports multi-hop data packets forwarding is crucial to enhance the performance of WMN. The key to WMN routing protocols is to automatically adapt to the frequent rapid changes in WMN and to quickly forward the packets.This dissertation focuses on the MAC protocols and routing protocols in WMN and includes the following parts: an introduction to WMN, IEEE802 series protocols, multiple channel allocation strategies, multiple MAC protocols, and self-adaptive routing strategies that support WMN structure. The research topics and contributions are as follows:In Chapter Two, I introduce and analyze the WMN IEEE802 series protocols that can cover different geographic ranges. These protocols consist of IEEE802.16 for constructing metropolitan area networks and IEEE802.15.5 for building personal area networks. The focus is on wireless local area network standard draft IEEE 802.11s.Chapter Three discusses the representative centralized channel allocation strategies and distributed channel allocation strategies. Centralized channel allocation strategies require the network traffic model in advance. They are of lower extension and can not self-adapt to network traffic changes. Although distributed channel allocation strategies have good extension, problems like channel dependence still exist. Therefore, a multiple channel allocation strategy based on interference model is proposed. The simulation results demonstrate that this strategy can effectively reduce channel interference in the whole network, and therefore enhance the network throughput.Chapter Four examines some typical MAC protocols and points out their weakness. When the number of active stations increases, the throughput performance of distributed single channel IEEE802.11DCF protocol based on contention deteriorates significantly. The disadvantage for 2P protocol is that the backbone links share a common channel, resulting in the bottleneck of the network throughput. The performance of the single interface multiple channel MAC protocol under common channel framework proposed in IEEE802.11s draft is restricted by the common control channel. A new multiple channel WMN MAC protocol MESH-MAC is designed. Forming links among neighboring backbone nodes by directional antennas, this protocol enables WMN to cover larger area and increases multiple orthogonal channel spatial reuse. To achieve reliable data forwarding, a new time synchronization mechanism is also proposed. The simulation results indicate that compared to IEEE 802.11 and 2P protocols, Mesh-MAC protocol is much better in performance and effectiveness.The routing protocol for WMN should self-adapt to the fast changing environments like dynamically changing traffic and fast changing wireless link quality. The traditional routing protocols designed for wired networks can not handle well the rapid changes in WMN.Chapter Five first introduces some Ad hoc routing protocols that are more closely related to WMN routing protocols, followed by analyzing some typical WMN routing protocols. The last part presents a WMN self-adaptive routing strategy based on interference model (IBAR). By selecting minimum interference route, it notably improves routing effectiveness. In order to adapt to the dynamically changing network environment, IBAR periodically adjusts the routes self-adaptively and balance the load in WMN gateway nodes. An effective method is proposed to solve the oscillation caused by self-adaptive routing strategy. By simulation, IBAR improves WMN throughput performance notably compared to AODV and HWMP protocols.The novel algorithms and mechanisms proposed in this dissertation have been theoretically explored and verified by computer simulations. They can be applied to the designing of WMN MAC and routing protocols.