Research On Qulity Of Service Mechanism In Wireless Mesh Networks

With the tremendous development of mobile communication technologies, wireless mesh networks have become a hotspot since they have the potentials to expand the coverage of the mobile communication systems, balance the services of adjacent cells, and enhance the data rate at the edge of cells by multi-hop transmission. Due to particular characteristics of wireless mesh networks in topologies and services, the original QoS models and algorithms can't guarantee its QoS.Using the cross-layer design approach, the thesis proposes a priority queue algorithm based distributed coordination function (DCF) mechanism and a cross-layer rate control algorithm dependent on network performance parameters to increase utilization of wireless resource while guaranteeing the quality of services of multimedia services. We introduce a controller between two layers of the wireless mesh networks to monitor the performance and demand of each layer and adjust the algorithm parameters dynamically. The network performance is also enhanced through the realization of better QoS of multimedia services and lower burden for exchange of information among different layers.In the proposed QoS model, the DCF mechanism of IEEE 802.11 on medium access control (MAC) layer is modified; Transmission priority is adapted to QoS demands and the queue lengths in the buffer. The packet marking is used to record and transfer the information of packets' priority on network layer. On Transport Layer, we use the rate controlling mechanism to opportunistically allocate resource to non-real-time services while guaranteeing the QoS requirement of real-time services. Simulation results demonstrate that the proposed QoS model could distinguish between different services, guarantee the appropriate QoS, and enhance the performance of the whole networks.