Performance Analysis And Improvement Of Ad Hoc Network's MAC Protocols

Mobile Ad hoc Network (MANET) is a network formed by a series of mobile hosts with wireless transceivers. It is a multi-hop and instant self-organizing network without the aid of any established infrastructure or centralized administration. MANET can be built up rapidly and flexibly, and it is free from the restriction of wired network, therefore, it can be widely applied to such situations as: military action, emergency search, disaster rescue, law enforcement and office meeting.In MANET, the channel resource is limited due to all of the mobile nodes shareing the same wireless channel under the condition of single channel. Therefore, an effective MAC protocol is required to coordinate the access of the nodes to the channel. Without its coordination, colisions would result from multiple nodes attempting to transmit data on the wireless channel at the same time.At first, the characteristics of MANET and its related techniques are reviewed in this thesis. Afterwards, the relevent research results and the problems of MANET's MAC protocols are studied deeply. Great attentions are paid to fair scheduling isssues and using ratio of the wireless channel. Then a dynamic backoff medium access control scheme is presented to improve fairness and throughput of MANET. Moreover, the QoS mechanism of MANET is also discussed.Simulation is operated with NS2 under Linux, and the simulation results show that, the presented algorithm is simpler and more practical, while it can improve the fair index of MANET to a large extent compared with the IEEE802.11 Binary Exponential Backoff(BEB) algorithm. It can make better use of the wireless channel by dynamically adjusting its backoff timer according to the network's contest situation. What's more, the algorithm can satisfy QoS requirement of real-time service.Finally, the thesis draws conclusions by summarizing the main contributionsof the research and by presenting directions for future work.