Research On Multi-channel Protocols For Wireless Sensor Networks

Wireless sensor network is a kind of close range,low power consumption and self organizing network,which is widely used in military,industry,transportation,home and other fields.With the development of WSN,it has made some progress in many aspects.As a link channel between the physical layer and the network layer,the MAC layer has been a concern of researchers.In this paper,MAC protocol is divided into single channel and multi-channel MAC protocol based on the number of channel.Through comparison of two kinds of protocol features,we point out that multi-channel MAC protocol has more advantages,but also will bring the channel allocation,hidden terminal of multi-channel problems etc..One of the research focuses of the current multi-channel MAC protocol about the wireless sensor networks is the channel assignment and access algorithm.Based on many kinds of multi-channel MAC protocol,this paper analyzed and designed an adaptive network environment of multi-channel MAC protocol— SMMAC protocol,which is based on the evaluation of the quality of the channel,judge the environmental situation at the nodes of the current node,and then select the channel assignment the way.Firstly,in order to reflect the current network situation effectively,appropriate channel quality determination method is needed.The effective data rate of nodes and the average time delay of data transmission are used as the indication of channel quality.And the availability of these two indexes is verified by simulation experiment.The EWMA model is used to evaluate the quality of the channel to satisfy the requirement of network stability and sensitivity.According to the evaluation of the quality of the channel,the Markov process is used to judge the current network environment and select the fixed channel allocation or dynamic channel allocation.Secondly,in order to ensure the efficiency of dynamic channel allocation,the method of game distribution based on regret degree is adopted,and the parameters of the algorithm are discussed and solved.After that,the rule based CSMA/CA channel access mechanism is adopted to reduce the channel access delay.Finally,on the basis of the former,we design a complete SMMAC protocol,including frame format,node state conversion,and function design,and discuss and solve the problem of interference,multi-channel hidden terminal that may occur during the operation of the time synchronization protocol.Then we use the Castalia based on open source OMNe T++ platform to simulate the protocol,which showsthat it has good adaptability to different node density and different load conditions.