| A Wireless Mesh Network (WMN) is a distribution network of mesh topology, in which the communications between nodes rely on mutual collaboration in wireless multi-hop manner, to provide Internet access for End-Users. WMNs have recently received a great deal of global attention because of its advantages of high capacity, high data rate, low cost and good scalability. However, the mesh network topology, multi-radio multi-channel configuration, and the complexity of wireless environment make the system performance unfit for the requirement of users. So the design of routing and transmission protocols is critical to the performance of wireless mesh networks, and it has been an active area of research recently.Focused on the mesh routing and transmission, this dissertation discusses and analyzes the problems of routing protocol, network coding and congestion control in detail. Main contents and innovations are listed as follows:1) The background and research status of WMNs are reviewed firstly. Problems within each layer, especially in routing and transmission layers, are introduced.2) The study of existing routing protocols in WMNs shows that the selection of routing metrics is very important. A routing protocol named MEIL (Routing Metric on ETX, Interference and Load) is proposed in Chapter 3. MEIL designs routing metrics according to the wireless link loss, interference between channels as well as the load of wireless mesh nodes. Then it chooses the path with lower loss, smaller interference and lighter load. Simulation results show that it improves the throughput of wireless mesh network efficiently.3) Considering the instability of link quality, Chapter 3 also presents a novel routing protocol named SPRP (Simple Proportional Routing Protocol). SPRP constructs a spanning tree based on the gateway node in advance. It doesn't choose the "Best Path", but selects next hop for a single packet according to the wireless link loss at that instant. In this way, SPRP can efficiently mitigate the impact of high loss rates and balance the load of nodes. Simulation results indicate that SPRP outperforms other common routing protocols with better packet delivery ratio and less end-to-end delay. 4) Based on the research of network coding, Chapter 4 proposes a Proportional Network Coding with Priority (PNCP) method. Considering the diversity of traffic flows and the stochastic nature of the packet arrival process in wireless mesh networks, PNCP keeps different queues in node buffer for different flows. Whether a packet is transmitted with or without network coding is determined by its priority and the queue state. A Markov Chain Model is formulated to analyze PNCP's performance in terms of delay and packet loss. Theoretical calculation and simulation results show that PNCP produces better performance than the current strategy without degrading the predominance of network coding.5) The application of TCP over wireless mesh networks is a challenging work due to high bit error rates. Chapter 5 proposed a congestion control scheme MRBR (Modified Reno Based RTT). In slow start phase, MRBR estimates the bandwidth using RTT to avoid sequential packets loss. In congestion avoidance phase, MRBR estimates congestion level by RTT, distinguishes between wireless link error and network congestion, as well as changes the congestion window size. Network simulation shows that MRBR improves the throughput of wireless mesh networks.
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