Research On Realtime Multimedia Transmission And Throughput Capacity In Wireless Mesh Networks

Wireless Mesh Network (WMN) is a new kind of network which provides large capacity, high speed and wide coverage. It also takes the advantage of transmission reliability, scalability and etc. It consists of wireless mesh backbone network and wireless mesh client network (Wireless Ad hoc Network).It is an important issue to transmit the real-time multimedia traffic and provide QoS guarantee in wireless ad hoc networks. For this problem, we design a new DSR routing protocol-QDSR protocol. We extend the DSR routing protocol by adding the QoS support and admission control mechanisms to DSR. For each new multimedia traffic in ad hoc network, the admission control mechanism judges whether the QoS parameters such as bandwidth, delay meet the new multimedia traffic requirements. If so, the new traffic is allowed to enter the network. This mechanism ensures the transmission quality of new and existing traffics.The reliable transmission of real-time multimedia traffic has the stringent requirements for delay and wireless network topology changes frequenly in wireless ad hoc networks. In this dissertation, we analyze these problems, and propose two approaches to improve them: First, we present a new link-failure detection algorithm-dynamic ACK algorithm. This algorithm lets the upstream node adjust the number and time interval when packets need to be confirmed according to the link status. A downstream node will only confirm the packets that need to be confirmed. Secondly, we present a QoS backup route mechanism. During the traffic transmission using the primary route, we maintain a backup route. When the primary route breaks down, this mechanism guarantee traffic will switch to the backup route with no delay which avoids delay of rediscovery route. The experimental results show that the proposed algorithms and mechanisms can be able to well satisfy the transmissions need of a variety of traffic including video applications under the moderate situations of load and mobility in wireless ad hoc network.The number of gateways and mesh routers, and the number of interfaces and channels will affect the capacity of the network in wireless mesh backbone network. In this dissertation, we analyze the effect of the wireless bandwidth, the number of gateways and mesh routers, and the number of interfaces and channels on capacity and the average throughput of mesh routers, study the capacity of wireless mesh backbone network, then derive the asymptotic upper bound for the average throughput of mesh router. In order to improve the overall WMN performance, we design the load balancing and route algorithm of mesh backbone network, which optimizes resource allocation and improves the utilization of resources in WMN.As the simulation technology is very difficult to reflect the reality of the wireless networks. Based on the above research, we build a wireless mesh network testbed and design a multi-interface routing protocol. We have done the extensive experiments and made the performance evaluations for the proposed algorithms and mechanisms on testbed. The experimental results show that our approaches improve the network capacity greatly. Meanwhile, our evaluation demonstrates that our load balancing algorithm with multi-interface routing protocol can effectively utilize the channel resources and optimize the performances.