Research On Key Techniques Of Routing And MAC In Wireless Ad Hoc Networks

Wireless Ad hoc network is a collection of peer wireless mobile or stationary nodes that autonomously form a multi-hop network without relying on preexisting fixed network infrastructure and with distributed administration. This kind of network will play a key role in many environments, e.g. military communication, disaster rescue, temporary conference and etc. However, comparing to other traditional communication network, Wireless Ad hoc network with the characteristics of self-organization,dynamic topology and etc. These characteristics pose severe challenges to design special routing and MAC protocol. This paper discusses and analyzes the problems of routing protocol as well as MAC protocol. The major contribution or this thesis are listed as follows:Chapter I mainly surveyed the history of Ad hoc network as well as its characteristics and primary application scenario. Then analyzed the architecture of Ad hoc network and explained the current research key problems. In order to make an in-depth knowledge of Ad hoc network, we established a testbed to test the performance in real environment.Chapter II presented the in-depth analysis of the impact of radio propagation to IEEE802.11MAC, then proposed a priority-based coordinating MAC protocol—CoMAC. CoMAC protocol based on the IEEE802.11MAC and made full use of radio characteristic. CoMAC introduced the concept of coordinating transport node in Multi-hop wireless Ad hoc network and chose the coordinating node based on the network condition, so that it can reduce the collision probability of packets and then improve the space reuse ratio of the network..Chapter III targeted at the irregularay of the radio propagation, analyzed the impact to all other protocols of the asymmetric link, then proposed an Asymmetric link aware MAC protocol—A~2MAC. The protocol first built the link condition aware neighbor table of the different network by using the algorithm of building the link condition aware neighbor table, and then design the MAC protocol based on the neighbor table, it can effectively reduce the collision problem cased by asymmetric link.Chapter IV analyzed the reseach condition and key problems of QoS routing in MANET, then proposed a QoS routing protocol of multi-hop WLAN—MQR. In this protocol, nodes-tree algorithm can organize the tree network topology based on the hop counts between MN and AP and the residual energy of the MNs, what's more, this protocol improve the traditional residual bandwidth estimation algorithm to make the node available bandwidth estimation much more precise and provide soft-QoS guarantee for packet flow based on the node available bandwidth during the routing.Chapter V analyzed all kinds of secure problems of Ad hoc network routing, then proposed an on-demand secure multi-path DSR protocol—SeMDSR and specified its framework and principle. Simulation result showed that the new protocol can alleviate some major security problems (i.e. fabrication, modification, routing black-hole attack, routing replay attack) with routing in mobile Ad hoc networks. A multi-path selection algorithm was proposed to alleviate routing rediscovery brought by DoS problem caused by evil nodes or by network environment changes.Chapter VI concluded the whole thesis and discussed the further work.