自组网环境下基于QoS的路由协议

自组网是一组带有无线收发装置的移动节点组成的一个多跳的临时性的自治系统。在这种环境中，由于节点无线通信覆盖范围的有限性，需要借助其它中间节点进行分组转发到达信宿。常规路由协议在自组网环境无法有效地正常运行。文中首先描述了自组网的概念和特点，在此基础上提出了自组网环境下的基于QoS的路由协议。该路由协议的主要思想是根据无线链路两个重要指标：平均错误分组率和生存时间进行路由发现、选择和维护。相对于跳数而言，它们向用户提供了最有可能满足特定QoS需求的信息流的传输。

QoS Routing in ad-hoc Network

Ad hoc network is a multi-hop temporary autonomous system of mobile nodes with wireless transmitters and receivers without the aid of preestablished network infrastructure. In such an environment, it may be necessary for one mobile node, in order to communicate with another node, to depend on a chain of intermediate nodes forwarding packets, due to the limited propagation range of each mobile node. Due to frequently changing topology and limited wireless bandwidth, conventional routing protocols cannot adapt well to such an environment. Furthermore, QoS support is one of the major concerns in ad hoc network. In an ad hoc network with the dynamics of nodes, hidden terminals, and fluctuating link characteristics, it is not a trivial issue to provide end-to-end QoS support. This problem should be addressed at multiple layer of the network protocol stack, such as transport layer, network layer and medium access control layer. It is important to take into account QoS requirements when designing routing protocols. This paper presents a distributed adaptive link state routing protocol for finding and maintaining the routes, which is most likely to meet QoS requirements, based on the two characteristics: Average Error Packets Rate (AEPR) and Living Time (LT). The AEPR criterion allows the protocol to differentiate between good and bad receiving quality channels. The LT criterion biases the protocol toward choosing a channel that has existed for a longer period of time. The routes selected in the protocol are not necessarily the paths with shortest hops, but they do give routes that have better receiving quality and that last longer, which may be more important and meaningful in ad hoc network environment. The protocol could be regard as QoS aware routing. The simulation results clearly indicate that the performance of the protocol exceeds conventional routing protocol such as Distributed Bellman-Ford and Ideal Link-state as the rate of topological changes is increased.