The Research Of Hybrid MAC Protocol With QOS Guarantee In Ad Hoc Network

Ad Hoc network is a kind of peer-to-peer network.It has many features such as centerless,The nodes in the network are equal.It has no fixed base station or mobile switching center,and all agreements must be distributed.The nodes act as host and router at the same time,it is responsible for routing and forwarding.With a node joining,leaving and moving,the nodes in the Ad Hoc network organize themselves.Ad Hoc network can support user's mobile features quickly and flexibly and realize the multimedia continuous seamless communication comprehensively.So,Ad Hoc network has become an active research category of personal communications and the Internet increasingly.The research purpose of the paper is to provide high quality of service with the load of the system changing.Based on the proposed hybrid MAC protocol and the research experience,the paper put forward a kind of hybrid MAC protocol MH-TDMA,which based on TDMA access protocol and avoiding conflict access protocol.According to the the competition condition of nodes in the network,the protocol can adjust the channel access strategy.With low load,the MAC mechanism will be CSMA/CA.When the data has led to a sudden increased load in the network,the MH-TDMA will detect the network congestion,and then work as a dynamic TDMA in the congestion area.In addition,local synchronization method is used in the initial stage.MH-TDMA combines TDMA protocol and CSMA/CA protocol and such a hybrid access strategy has an advantage of competition and distribution agreement.It is not only beneficial to reduce the probability of data conflict,but also effcient for maintaining a higher channel utilization and high throughput rate,which make the internet keep a good overall performance as the load altering.According to the QOS metrics we designed the congestion resource scheduling module and analyzed the MH-TDMA QOS guarantee.According to the multiple-hop characteristics of Ad Hoc network,the paper only designed the two jump competition between nodes.At the allocation of time slot phase,when the conflicts occur between nodes,we will delete again after long time slot,segment time slot or using double frame to solve.In the time slot competition stage,when the waiting time competition is long,the paper designed a mechanism to make high-priority business waiting time is less than the low priority.In retreat mechanism,the paper makes high-priority business retreat the shortest time and then the mechanism can keep the QOS agreement.Based on the theory of the protocol algorithm,the paper uses the network simulator(NS2).The simulation results show that MH-TDMA protocol can improve the network throughput capacity and reduce the average access delay,and keep a good QOS guarantee.