Research And System Desiqn On MAC Protocol For Adaptive Traffic In Wireless Sensor Networks

Wireless sensor networks(WSNs)is a new kind of network which has been an active research area in the past few years.Easy installation,less maintenance costs and mobility support motivate the use of WSNs for military applications,environment monitoring,industrial automation and many other applications.WSN build the bridge of physical world and information world,and it has been considered as one of the most important emerging technologies for the 21st century.Medium access control(MAC)layer protocol plays a fundamental role in network stack of WSNs.It allocates the limited radio resource among sensor nodes,and has a great influence on the WSN performance such as network throughput,transmission delay,energy cost,etc.Considering the variable network load in WSNs,this thesis focuses on the research of traffic adaptive MAC protocols and their system implementation in WSN.The contributions of this thesis are summarized as follows:To enhance the limited throughput of low-power MAC protocols when dealing with time constrained burst traffic,we propose eQueue-MAC,a duty-cycle based CSMA/TDMA hybrid traffic adaptive MAC protocol.With the use of packet buffer queue length of nodes as the network traffic information,eQueue-MAC can assign enough dynamic TDMA slots to relevant nodes for contention free data transmission.Through extensive experimental measurements,we showed that eQueue-MAC protocol has a good performance in various network traffic.To promote the transmission robustness under interference induced by single channel MAC protocols,we proposed mQueue-MAC,a multi-channel and channel hopping based MAC protocol.A channel selection mechanism is designed for the coordinator devices to maintain their own superframes in different channels and cooperate with each other.According to predefined channel set and hopping list,devices can communicate in channel hopping mode in dynamic Time Slotted Channel Hopping(TSCH)period.A channel blacklist mechanism is proposed for banning the channel which has low communication quality for a long time.Experimental results showed that mQueue-MAC outperforms existing WSNs MAC protocols in terms of delay,energy cost and reliability.The MAC protocols proposed above has been successfully implemented on the EM357 SOC chips.Moreover,an integrated network data collection system is designed for data collection,calculation and persistence using different kinds of data sources.Compressive sensing technique is also introduced into the system in consideration of data sparsity of signals in the environment.A novel compressive sensing based downsampling sublayer is implemented on the sensor device side,and an asynchronous compressive sensing reconstruction engine is designed on the server side.Experimental results confirm substantial performance on availability and effectiveness of the system.