Link Availability Prediction And Policy Routing For Heterogeneous Ad Hoc Networks

Ad Hoc, which indicates a network with special purpose, means "for this purpose only". It derives from the Latin and The Committee of IEEE 802.11 uses Ad Hoc to represent multi-hop, peer to peer, and distributed self-organizing mobile communication networks. This type of network does not require fixed infrastructures, and is suitable for fast networking to communicate in floods, earthquakes or military scenes. Routing is a very important part of network and so it is to Ad Hoc. Tranditional Ad hoc network routing protocols typically choose hop as the basis for routing selection. But the disadvantage of using hops as routing criterion is that it’s prone to hot spot effect, edge effect, link failure and low communication quality of the link. The settle scheme for these disadvantages is the introduction of an index measuring link availability. And it can improve the property of routing protocols measurable. Current researches in this field mainly focused on homogeneous network.Previous studies about link prediction mainly focus on homogeneous Ad Hoc networks, but the heterogeneous one is more widely used. So we carried out some studies based on a multi-level Ad Hoc and heterogeneous network architecture, which in an autonomous area the heterogeneous network that consisting of 802.11 and 3G extends the coverage of 3G networks and provides access to Internet for Ad Hoc networks.Firstly, we categorize and analyze the forecasting methods of mobile Ad Hoc networks. It can be divided into three types which are forecasting based on mobility model, cross layer design and the combining one. The mobility model requires to model node mobility, which is comparatively accurate in a short prediction time. Information extracted from the low level of the protocol stack is needed by the cross-layer design, but the result about increasing packet delivery rate and reducing delay is fruitful. The integration of the previous methods behaves well in reducing latecy and increasing packet delivery ratio.Secondly, so as to choose a better link before routing, signal to noise ratio is used to forecaste link availability based on the idea of cross-layer design and the analysis of existing methods. We named the new method "Prediction of Two-hop-styled Link Availability Base on Cross Layer Design". The simulation result shows that the new method has a good adaptability to node mobility but its performance will decline with the growth of the network size.Thirdly, in the network model studied in this thesis, the load and communication quality of 3G link affects the performance of the entire network of Internet services. We improve an load balancing algorithm and then present a service gateway selection algorithm which considering the characteristics of the Ad Hoc network and the quality of 3G link based on link availability. And it balances the gateway load of heterogeneous network and improves network performance.Fourthly, in order to solve the communication problem of multi-level heterogeneous Ad Hoc network architecture this article studies, according to the thought of strategy routing, we propose a routing policy for across subnet or autonomous communication. The main idea is taking domain ID, network number and source address into consideration. Finally, we analysis the performance of the existing Ad Hoc network routing protocols. Meanwhile, an improved method about the routing protocol is presented based on the research results proposed in this thesis.