An Interference Graph Based MACProtocol For Ad Hoc Networks

The Ad Hoc Networks are composed of a collection of wireless nodes, which are connected together by their wireless links. Ad Hoc Net works don't have the central control mechanism and don't need the support of static communication equipment. As the nodes attend, leave or move, Ad Hoc Networks can be self organized and controlled. In the Ad Hoc Networks, each node may function as communication terminal or intermediate node (routers). One distinguishing feature is that users, when communicating to each other, may establish a multi-hop path among these wireless links, quite different with current existing networks. Another distinguishing feature is that the network topology in Ad Hoc Networks may be frequently changed and dynamically adapted. Due to their high flexibility and high survival ability, Ad Hoc networks are very much suitable for the use in battlefield communications; nonetheless, more and more civil communications such as rescue operations and city bus communication are adopting Ad Hoc networks in recent years. The huge application fields let the Ad Hoc Networks become a current research hotspot.However, people have worked on the research of Ad Hoc Networks for many years. Due to the characteristic such as none central control, dynamic topology and unstable network nodes, there are also many difficulty problems haven't been solved.Hidden terminal and exposed terminal are two problems existed in the Ad Hoc Networks which can decrease the network performance deeply. Hidden terminal causes the network conflict and exposed terminal decrease the spatial reuse. Though IEEE 802.11 MAC protocol has been widely used in Ad Hoc Networks, due to it uses simplified interference model, the hidden terminal and exposed terminal problem can't be solved by IEEE 802.11 MAC protocol.In order to solve these two problems, people have proposed several new MAC protocols and methods. But due the misunderstanding of interference range and some difficulty problem like large interference range, these research results can't totally solve those two problems. In this paper, we propose a new MAC protocol named "Interference Graph based MAC protocol" which used interference graph to model the conflict information and use Busy Tone signal to block the interference nodes. IG-MAC protocol eliminates the affect of big interference range that can totally solve the hidden terminal problem. In the other hand, IG-MAC protocol codes the communication nodes information into the Busy Tone signal which can let the IG-MAC protocol won't block the wrong nodes and solves the exposed terminal problem. In our works, we implement IG-MAC protocol and a simple version of IEEE 802.11 MAC protocol by using the network simulation. We compare the IG-MAC protocol and IEEE 802.11 MAC protocol in three different aspects. The simulation result told us that IG-MAC protocol can improve the network performance substantially.In the end of the paper, we conclude the whole research process and propose the further work.