Improving The Quality Of Service Queue Management And Scheduling In Wireless Mesh Network

Wireless mesh network (WMN) is a wireless distributed network with large capacity, high speed and multi-hop, which play important role in integration of various existing wireless network. However, the diversity of services makes quality of service in WMN more difficulty than other networks. Fair scheduling of data streams among nodes is an essential technique in ensuring the quality of service for network users. In order to use the limited WMN network resources fairly and efficiently, data flows scheduling in and between the nodes are studied in this thesis.Firstly, an Adaptive Overtime Detection Model (AODM) is proposed to solve buffer contention problem of self-flow and relay-flow in nodes caused by related location-based competition, and manage the packets in the buffer queues. By designing the threshold and packet loss function of buffer queue which are suitable for wireless multi-hop network, packets reaching the node are timeout estimated. Based on estimating results, the channel state is monitored in real time by using the channel prediction factor to adjust the packet loss rate, and the value of the threshold is adjusted according to changes of the node's transmission rate. Furthermore, A selective packet loss strategy is designed as packet loss method of buffer queue. In the premise of guaranteeing queue length of node, the model selects packet into buffer queue according to hop in order to reduce the dropping probability of relay-flow.Secondly, an Installment Coordination-Scheduling-based Fair Queuing algorithm (ICSFQ) is proposed considering such problems as unfair channel allocation among nodes in binary exponential backoff mechanism of traditional MAC layer. Through the establishment of installment coordination-scheduling model, data communication process of nodes is divided into three periods, namely, sending stage, compensation stage and dormancy stage. According to model parameters, time constraint functions are designed to limit the execution time length of each period. The transmission of packets of the node itself is made in the sending stage, compensation flow queue, which is defines each node, executes resource compensation to other nodes in compensation stage and the abandonment of channel with sending rights delivered to other nodes is carried out in dormancy stage. Each node completes fair transmission of network packet together in accordance with fixed coordination scheduling rule of model.Finally, performance evaluation, including throughput, packet loss ratio, buffer queue length and fairness, is carried out to nodes by using NS2 simulation tool, so as to examine the effectiveness of the proposed AODM and ICSFQ.