MAC Protocol Design Of Wireless Sensor Networks In Intelligent Transportation System

Traffic congestion and traffic accidents become the major obstacle of the city todevelop itself. Wireless sensor network is developing rapidly in recent years. It is anew type of network. Its real-time monitoring and dynamically sensing are suitablefor the characteristics of intelligent transportation system. In wireless sensor networks,MAC protocol is responsible for allocating the limited resources of wireless channel.Its design directly affects the performance of the network. For monitoring the bridgesin intelligent transportation system, this paper proposes a multiple priorities andmulti-channel MAC protocol (Multi-Priority Multi-Channel MAC, MPMC-MAC)in wireless sensor network. MPMC-MAC protocol design content can be dividedinto the following aspects:Firstly, four frame structure and the form of super frame were designed for theprotocol. Then, according to the time of sensing events, nodes dynamically adjustthe length of active cycle and sleep cycle. In active stage, the protocol adopts themethod which combines competition way with scheduling way get the channel. Atthe same time, with respect to the manner of access channel in active cycle, nodesalso take dynamic adjustment. According to the situation of network load to adjustthe length of the scheduling and competition way, to ensure the success rate ofchannel access, and to make the channel utilization rate was improved, This methodalso can ensure the expansibility of the network.Secondly, we design an algorithm of priority allocation. This algorithmcombines the type of data and frequency of sending data. According to two kinds offactors, the algorithm allocates priority information of nodes. Based on wirelesschannel situation of bridge, the algorithm allocates channels according to the priorityinformation. The node which is allocated a higher priority has a high probability to beassigned a better channel. So we can ensure the node which has high frequency ofsending and important types of data can get a better resource of channels. When theretransmission happens due to channel conflict, the protocol needs to allocate retransmission channel for the node. This protocol designs a method which combinesretransmission times, priority information and residual energy for the node toredistribute retransmission channels. This method ensures the node which hashigh-priority to get better channels, and can guarantee the fairness of the network.Finally, NS-2software is used in this paper, and the simulation parameters is setaccording to the situation of wireless network which around bridges. Simulationresults indicate MPMC-MAC performs better than other MAC protocols in networkthroughput, average transmission delay, energy consumption and packet drop rate.