摘要
无线Mesh网(Wireless Mesh Networks, WMN)是一种基于多跳路由、对等网络技术的高容量、高速率的新型网络。WMN本质上属于Ad hoc网络,但是它与后者存在较大的区别。与Ad hoc网络相比,其用户终端的移动性较弱。WMN一般不作为一个独立的网络结构存在,而是作为因特网的“最后一公里”接入网。目前,WMN中常用的路由协议大多来自对Ad hoc网络路由协议的改进,对于支持多射频多信道路由协议的研究才刚起步。本文对WMN中支持多射频多信道的跨层路由协议进行研究,对已有算法进行改进,并通过仿真评测其性能。
本文首先介绍了无线Mesh网的特点及其应用情况,结合其移动性特点选择先应式路由协议OLSR作为研究对象,着重介绍了OLSR路由协议以及跨层路由的设计方法。然后,将射频切换、信道分配与路由相结合进行跨层路由优化,基于路径链路信道多样性参数设计新的路由判据,并结合OLSR协议详细阐述了改进的跨层路由协议一-FC-OLSR具体的实现细节和过程。在FC-OLSR中,无线节点比较节点与目的节点的ID值后,多次利用Dijkstra算法计算到达某一目的节点的多条路径,保证本节点和目的节点建立到彼此的路径时所计算出的路径相同。利用新设计的CSI-HOP路由判据选出性能最优的两条路径,利用节点流入、流出路径选择方案选出源目的节点彼此间的不相交路径,可以减少源目的节点对通信时中间节点的切换时延。最后,利用OPNET网络仿真平台对多射频多信道跨层路由协议进行了仿真研究。仿真结果表明:与文献中已有协议相比,改进的FC-OLSR协议能更好地改善网络性能。
Wireless mesh network is a new network structure with high rate and high capacity, which is based on multi-hop routing and peer-to-peer network technology. Wireless mesh network belongs to Ad hoc networks in nature. The biggest difference between them is user terminal mobility. Generally, wireless mesh network cannot act as an independent network, but as the last mile access network of internet. At present, the routing protocols used in wireless mesh network mainly come from the revision of classic routing protocol of the Ad hoc networks. The study of routing protocols of multi-radio multi-channel wireless mesh networks is still in the experimental research.
This paper first introduces the characteristics of topology for wireless mesh network, and combined with the mobility performance of the node, chooses the OLSR routing protocol as research object. Secondly, we introduce the OLSR routing protocols and the design method of cross-layer routing in detail. And then, we propose a scheme in which radio interface switching, channel allocation and routing function of network layer is integrated in order to optimize routing protocol of cross layer. Finally, we describe the specific details and process of implementation of cross layer design with OLSR protocol, and propose an improved routing protocol called FC-OLSR.
In the FC-OLSR protocol, wireless nodes compare the IDs of source node with the destination node, and choose Dijkstra algorithm to calculate the multiple paths which reach a certain node, in order to ensure that paths established by the node and destination node to each others are same. It chooses two paths with optimal performance by a revised routing metric called CSI-HOP. The selected path of the node is disjoint with the destination node through the scheme for the outward and return paths of the node, which can reduce the delay of switch time in intermediate nodes when the node is communicating with the destination. Finally, simulations based on the OPNET network simulation platform are used to evaluate the multi-radio multi-channel cross-layer routing protocol. The simulation results show that the performance of FC-OLSR is better than M-OLSR.
引文
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