Ad Hoc Networks Qos Mac Protocol

Ad hoc Network 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.Ad hoc Network 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.In Ad hoc Network,the channel resource is limited due to all of the mobile nodes sharing 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.At the same time, the application environments and potential applications in commerce require that wireless ad hoc networks should support Quality-of-Service(QoS).A QoS-aware MAC protocol is a key factor for QoS supporting components at upper layers.The simple effective and providing service differentiation MAC protocols are therefore very important.At first,the concept,features,applications of Ad Hoc Networks and the hot research fields are reviewed in this thesis,and the QoS support in MAC layer is also recommended. Afterwords,the simulation system and methods of OPNET are introduced briefly.Then studied the performance of 802.11 DCF and 802.11e EDCF in multi-hop Ad Hoc Networks with simulation method.EDCF can improve the QoS of multi-media traffic based on the expense of low-priority traffic,but it didn't consider the cumulative effect of the delay when a packet was retransfered by many middle nodes in multi-hop Ad Hoc Networks,and the cumulative effect of the delay is negative for the multi-media traffic traversed from many hops.This thesis proposed a More Hop First system based on EDCF(MHF-EDCF) with cross-layer method in order to offer the multi-media packets with more hops higher priority,so they can access the channel more quickly,and reduc the end-to-end delay. Finally,compare the performance of MHF-EDCF and EDCF using simulation method with OPNET Modeler 10.5 software.The simulation results show that,compared with EDCF, MHF-EDCF can greatly reduce the end-to-end delay of multi-media traffic,and to a certain extent,it can improve network throughput.