Research On Key Technologies In Ad Hoc Networks

Ad Hoc networks are full-distributed wireless packet switch networks. In this environment, a mobile node may function as a communication terminal and as a router. In such networks, a data packet is relayed hop-by-hop between two adjacent nodes, without any supports of infrastructure. The distinguish features of the networks, which are self-organizing, self-managing, and multihop, make Ad Hoc networks' constructing more convenient and flexible. As a result, Ad Hoc networks have broad prospects in such communication scenarios as battlefield, public service, emergency rescue, intelligent transport, small office, conference meetings and so on. Nowadays, Ad Hoc networks are hot research areas both in home and abroad.Because of dynamic topologies, limited bandwidth, energy constrains, there are still quite a number of problems for opening services in Ad Hoc networks. To develop routing protocol with energy saving strategy, security-guarantee, multicast and support of quality of service, medium access control scheme, and network management are all key and difficult points in research. Under the support of the national natural science foundation project No. 60672132 (Research on key technologies of MPLS based Ad Hoc wireless mobile networks), the thesis focuses on some key technologies in network layer and medium access control layer of Ad Hoc networks. The main innovations are as follows.1. The architecture of MPLS technology is simplified according to the character of Ad Hoc networks, and the network architecture of MPLS based Ad Hoc networks is proposed, which provides technique support for the research on MPLS based Ad Hoc networks.2. A novel routing algorithm, LSMR (Label Switching Multipath Routing), is proposed, by applying label based rapid forwarding property of MPLS technology into Ad Hoc networks. LSMR migrates the advantages of label switching and multipath routing, and can establish multiple node disjoint label switched paths between source and destination node on demand, which allow the entire packet forwarding operation to be executed within the link layer on multiple label switched paths. LSMR can speed up packet forwarding and increase network throughput. Label switched path provides connection-oriented path with end-to-end QoS guarantee.3. The reason of the path decreasing problem in node-disjointmultipath routing algorithm is analyzed, and the impact of the number of neighbor nodes, path length and forwarding scheme on path decreasing probability is theoretically derivated. Based on the analytical results, a new algorithm AODV-TF (AODV Twice Forward), is proposed to diminish path decreasing probability by revising the forwarding scheme of routing request.4. In order to improve performance of the real-time traffic in Ad Hocnetworks, a new medium access control scheme called RL-DCF (Realtime-oriented Label-switching DCF), is proposed based on 802.11 DCF. RL-DCF adopts three schemes, such as label switching in MAC layer, consecutive transmission and retransmission control, in order to decrease the end-to-end delay and increase the network throughput of realtime traffic.5. To solve the unfair problem between different traffics in RL-DCF,and avoiding network congestion, DL-DCF (Differentiated Label-switching DCF) is proposed. DL-DCF provides different type of traffic with different consecutive transmission probability, in order to differentiate the real-time traffic from the best effort one. The performance of two types of traffic gets improved, and the control overhead is decreased.6. An ant-colony based dynamic routing algorithm, ADRA isproposed for Ad Hoc networks. The pheromone of ant colony is used to reflect metrics of the path, and hence can guide the choising of paths. By ant colony optimization, pheromone of the route is updated dynamicly, which can improve the performance of networks.