Research And Realization Of The Multi-Channel MAC Protocol In Ad Hoc Network

Ad Hoc network is a special kind of wireless mobile networks. All nodes in the network are equal, without any central control node. Nodes not only have the general function required by mobile terminals, but also possess the ability to forward messages. MAC protocol, which is at the bottom layer of the Ad Hoc network protocol, determines the channel used by network and has a great impact on network performance. MAC protocol is one of the pivotal protocols in Ad Hoc network to ensure efficient network communication. The research on MAC protocols of Ad Hoc Network has been a hot issue, and has a very important practical significance. In traditional single-channel MAC protocol, all control packets and data packets are transmitted in the same channel, which not only results in inefficient data transmission, but also can not solve key issues in Ad Hoc network such as hidden terminal and exposed terminal problem. All of these have seriously affected the performance of data transmission networks.Based on the analysis of the domestic and overseas research on MAC protocol of Ad Hoc Network, MAC protocol backoff algorithm becomes an emphasis of our research. Basing on communication state estimating idea of local area network, it puts forward a fair and efficient backoff algorithm (Both Fairness And Efficiency, BFAE) in nodes channel competition and evaluates the fairness of node channel competition by calculating the fairness index for channel competition of all network links. The analysis and the result of stimulation experiment show that compared with the standard BEB algorithm in IEEE 802.11 and other algorithms, the proposed algorithm is not only simple, but also has an excellent performance in fairness of node channel competition under the circumstances of a high throughput of the network.Based on the idea of multi-NIC and multi-channel data transmission, an Ad Hoc network for multi-channel MAC protocol-MCMAC (Multi-Channel MAC, MCMAC) has been designed and implemented. To achieve the goal of multi-channel data transmission, multi-NIC has been adopted in MCMAC. At the same time, RTS-CTS-DATA-ACK handshake process in IEEE 802.11 is modified to adapt multi-channel data transmission in MCMAC, which solves Hidden terminal and exposed terminal problems in MCMAC. In order to attain both efficiency and fairness in node channel competition, BFAE backoff algorithm is adopted in MCMAC protocol.Under the NS2 platform, simulation experiments are carried out to get contrast between MCMAC protocol and other single-channel MAC protocol. Experimental data show that, compared with the traditional single-channel MAC protocol, MCMAC protocol not only solves the traditional hidden terminal and exposed terminal problem in Ad Hoc network, but also has unparalleled advantage in network transmission performance, such as high throughput and low packet loss rate.