Study On Selection Cooperation In Wireless Sensor Networks

As a novel transmission strategy, cooperative transmission is suitable for wirelesssensor network (WSN) for its multi-user diversity and improved communicationreliability. Among various cooperative schemes, selection cooperation is an effectivecooperative method for its simplify and easy implementation. In this scheme, thecooperative transmission is performed only by one best relay node selected frommultiple relays and it achieves the full diversity gain. Therefore, selection cooperationbecomes a preferable cooperative scheme for WSN. However, it does not designed andoptimized for WSN initially, so it is significant to investigate improved selectioncooperation schemes and their performance for meeting the requirements of WSN,including low complexity, energy efficiency, and cross layer design.In this dissertation, considering the characteristics and requirements of WSN,following the steps of model building, scheme design, theoretical analysis, simulationresults, and experimental tests, we focus on the selection cooperation schemesoptimized for WSN.Considering the requirement of low complexity, we first develop a lightweightselection cooperation protocol with feedback. The scheme does not require the radio ofnodes to perform combining reception and channel sorting. So it reduces the complexitygreatly. Through outage probability and diversity-multiplexing tradeoff (DMT) analysis,we reveal an interesting fact that choosing any node that successfully receives themessage from the source and the feedback frame from the destination as the best relay,the protocol always achieves the optimal DMT. This result overcomes the limitation thatthe node with the maximum relay-destination channel has to be selected as the bestrelay for obtaining the optimal DMT in conventional selection cooperation schemes. Italso establishes a framework for obtaining multiple optimization objectives in selectioncooperation networks. As an illustrative example, we then develop two best relayselection methods for relay balance without sacrificing the full diversity order, whichhave remarkable balance effect and prolong the network life time.Next, using cross layer design principle, we propose a context-aware selectioncooperation scheme based on sensor relationship for heterogeneous networks. Weconsider a heterogeneous wireless sensor network consisting of different kinds ofsensors where the activities of one kind of sensors are designed to trigger by the other kinds of sensors. The prior transmissions of the inducing sensors make up the context ofthe transmissions of the following sensors. By exploiting the context information andthe transmission relation, in the proposed scheme, the inducing sensors can cooperatewith the following sensors after their own transmissions for improving thecommunication reliability of the latter nodes. Through performance analysis, we showthat the protocol achieves the full diversity gain with the cross layer optimization fromapplication layer to physical layer. We further develop an energy-efficient best relayselection method based on power control where the power consumption is minimizedwithout decreasing the full diversity order. The method fits the requirement of lowenergy consumption in WSN.For interferential scenarios in WSN, we proposed a non-orthogonal selectioncooperation scheme for multiple points to one point case. By using successiveinterference cancellation in the sink node, the effect of interference is reduced and thefeedback delay problem is solved. Through the outage probability analysis andcomparison, we show that the spectral efficiency is improved while the system stillkeeps acceptable transmission reliability.Finally, we establish and implement an improved selection cooperationexperimental platform based on WSN to address the issue of test bed for cooperativetransmission. The architecture of the platform is presented and the selection cooperationschemes are deeply integrated into the IEEE802.15.4standard (Wireless MediumAccess Control and Physical Layer Specifications for Low-Rate Wireless Personal AreaNetworks). The platform is built with commodity hardware of wireless sensors andopen-source protocol stack and has the advantage of low cost and flexibility. Based onthe experimental platform, the performance of proposed cooperative schemes in thisdissertation is verified by detailed tests.The work in this dissertation combines the cooperative transmission and the WSN.On one hand, it enhances the basic schemes of selection cooperation and extends itsapplication areas. On the other hand, it improves the transmission reliability of wirelesssensor networks and contributes to the practical deployment and applications ofselection cooperation in WSN.