Performance Analysis And Multiple Access Interference Suppression For Wireless Cooperative Systems

Cooperative transmission, as a promising technique exploiting space diversity gain,offers a new dimension of freedom, which makes higher transmission rate and higherspectrum utilization possible. Single antenna and portable mobile terminals coordinate andshare wireless resource each other. Accordingly, multiple communication links between thesource nodes and the destination nodes are established with a virtual MIMO (Multiple Inputand Multiple Output) system, providing approaches for MIMO technique implementation. Asa result, cooperative transmission is taken as one of the key technologies for future wirelesscommunication networks and draw tremendous attention. Also, it has become a hotspot in theresearch of the wireless communication field.Therefore, this thesis focuses on the performance evaluation of cooperative transmissionover all kind of environments. Based on these evaluation results, the problem of multipleaccess interference suppressions when terminals and relay nodes access into the wirelesschannels is studied. This thesis attempts to be self-contained and begins with a summary ofefforts poured into the topic by both domestic and international researchers. Holding singlerelay cooperative transmission systems as objective, this thesis will focus on performanceanalysis of opportunistic relaying and selection relaying over fading channels, and the effectsof variable CSI (Channel State Information) on system are well analyzed by lateral andvertical directions. Then, the theoretical analysis obtained above draw forth the multiplespectrum access interference and possible solutions resolving multiple access interferencesuppressions are provided at last. The results and conclusions obtained in this thesis can bepartial theoretical bases for the future wireless communication networks.The main contributions of this thesis are as follows:1) With the probability and statistics theory, aiming at single relay wireless networks,the performance parameters of two single relay selection cooperative transmissionsystems over Nakagami fading channels are put forward. For single relay cooperativetransmission can decrease multiple access interference and improve spectrumutilization, especcially in dense network circumstance, outage probability, symbolerror rate and channel capacity performances for opportunistic relaying and selectionrelaying with DF (Decode-and-Forward) are derived at arbitrary signal-to-ratios,respectively. Then, the theoretical analyses are validated by Monte Carlo simulations.The obtained closed-form expressions provide an analytic method of studying wireless cooperative transmission systems.2) CSI is crucial to all kinds of protocol designs for wireless networks. Based on theperformance parameters of single relay cooperative communication, the effects oflateral and vertical CSI correlation on cooperative transmission systems are wellanalyzed. Both the theoretical analysis and simulations show that, from lateraldirection, the varied wireless channels may bring fatal influence to the performanceof the cooperative network, and the more time correlation, the little effects oncooperative performance. However, from vertical direction, the more spacecorrelation, the more effects on cooperative performance. Moreover, simulationresults show that the derived exact results very well match with the simulation curves,which illustrate the validity of overall numerical performance analyses results.3) Due to the complex spectrum management in multi-relay channel accesses fordistributed wireless cooperative networks, an improved DTR (Distributed ThresholdRelaying) algorithm is proposed based on the local game between source and relays,which selects a best relay offering cooperation. In our novel algorithm, each sourcecontrols its standard of accessing channel with threshold scheme adaptively, whichsubstitutes base station or AP (Access Point) in centralized networks and couldcarried out in distributed systems. In addition, the added communication overheadwould pay less compared with the backoff time and collision in DTR. Analysis andsimulation results show that our proposed algorithm, without increasing significantnetwork overhead, provides less delay consumption and more throughputimprovement compared to DTR.