Access Technology Research For Self-Organized Emergency Communication

All nodes in wireless self-organized network are mobile nodes with wireless communication abilities. It is a kind of self-organized, temporary, multi-hop routing supported, dynamical topology supported, peer-to-peer and self-recovery wireless network. Currently, the most widely used wireless self-organized network is Ad Hoc network, which is defined in IEEE802.11standard. Ad Hoc network can work without the supports of network infrastructures, and has lower node ability requirement and networking delay than other new wireless network such as satellite communication network. Channel access technology is a very important part in Ad Hoc network technologies, especially in emergency communication. Channel access protocol has a great influence on networking efficiency and communication quality of the network. These factors affect the network communication ability in emergency relief directly.Firstly, the paper researches the characters and abilities of Ad Hoc network, Ad Hoc networking technologies, emergency communication, and some existing channel access protocols for Ad Hoc network. Secondly, based on the802.11DCF (Distributed Coordination Function) protocol, the paper designs a new channel access protocol, ECS-DCF (Emergency Communication Supported DCF), which has a new back-off mechanism called DEB (Dynamically Exponential Back-off) and suitable for emergency communication. Then, the paper simulates and tests the new protocol, with the networking process of hierarchical Ad Hoc network, which is designed in a related project in our lab, by using NS-3network simulation tool. Finally, the paper compares the performance of the two protocols, and makes analysis and conclusions by the results.The hierarchical Ad Hoc network structure and networking process in the paper reduces broadcasting cost, path loss and confliction probability in emergency communication network. Therefore, it has higher networking efficiency and reasonable resources allocation method. The channel access protocol and the back-off mechanism are based on the characters of emergency communication. They can provide higher networking and node accessing efficiency, and better performance to the hierarchical Ad Hoc network in emergency communication.