Cross-Layer Routing Protocol Based On Link Available Bandwidth Estimation In Wireless Ad Hoc Networks

Due to its independence of fixed infrastructure, quick networking, and strong anti-destroying, wireless ad hoc networks have been widely used in the field of military and civil communications. In recent years, with the rapid increase of multimedia business type and number, how to guarantee the quality of service(QoS) of multimedia business has received wide attentions from people. In the condition of multi-hop, shared and limited bandwidth in ad hoc networks, in order to realize the multimedia business flows' QoS guarantee, we must put forward an accurate and real-time available bandwidth estimation method in the data link layer, so we can realize cross-layer routing according to available bandwidth results based on this method. Our innovative work centres on the above key problems, and the main innovation points are summarized as follows:(1). Based on the full comparison of the existing two kinds of available bandwidth estimation method, according to the two difficult problems when evaluating available bandwidth in ad hoc networks: the desynchrony in available period between transmitter and receiver, as well as the transmitting failures because of hidden nodes, we put forward a link available bandwidth estimation method based on distributed coordination function(DCF) protocol. Firstly, the method defines the maximum throughput in a link that can be seen as the upper limit of the available bandwidth in a link. Then, the method requires transmitter/receiver nodes to detect their own available periods using carrier sensing ability. Through analyzing the desynchrony in available period between transmitter and receiver, we get the preliminary estimate. Lastly, the method discusses the transmitting interruption because of hidden nodes in two cases to amend the preliminary estimate. Finally, we get the revised estimate. The simulation results verify the accuracy of the available bandwidth method.(2). Based on fully verying the link available bandwidth's important influence on the performance of routing protocol, combined with the above link available bandwidth estimaton method and the AODV routing protocol, we design the cross-layer routing protocol based on link available bandwidth estimation. The routing protocol comprehensively considers link available bandwidth and hops of the multi-hop path in the routing discovery process, which not only ensures the QoS of existing business flows, but also finds a transmission path meeting their bandwidth consuption for the new business flows. In order to realize the admission control of business flows, the routing protocol evaluates available bandwidth of a link with the help of Hello packets that exchange available period information between neighbor nodes. In the process of predicting bandwidth consumption of multi-hop path, the routing protocol fully considers the “intra-flow contention”, pointing out that the business flow's bandwidth consumption at a node should be contention count times its required bandwidth. Based on the above two aspects, the routing protocol conducts admission control of business flows, selecting the route with link available bandwidth satisfying bandwidth consumption and less route length. The simulation results show that the routing protocol can effectively provide Qo S guarantees for the exsting flows and new flows.