Study On The Strategies Of Relay Selection In Wireless Networks

Cooperative communication increases wireless transmission rate and reliability,meanwhile it enlarges coverage area and saves energy, thus it attracts much attention inacademic circles. The basic model of cooperative communication is three nodes dual hopcooperative relaying, in which relay selection influences cooperative capacity, terminal powerconsumption, throughput, end-to-end bit error rate and spectral efficiency. Many studies focuson relay selection of single user, namely single user selects one or several relays frommultiple candidate relays; while in multi-source multi-relay wireless network, how to assignappropriate relay for each user has been less studied. In case of that, this dissertation focuseson relay selection in multi-source multi-relay network based on three nodes dual hop model.The dissertation firstly introduces four kinds of models of three nodes dual hop relaysystem and two types of relaying technology, then introduces capacity formulae of DF and AFrelaying systems, at the same time analyzes outage probability and end-to-end error bit rate ofDF relaying system.Based on the single user relay selection algorithm, the relay selection algorithm inmulti-source multi-relay network is analysed, centralized and distributed relay selectionalgorithms baed on two types of basic network models are proposed, with the aim tomaximize system benefits. On the minimization of system power consumption, the proposedcentralized algorithm has little signaling overhead and effectively avoids selfish and cheatingbehavior; the proposed distributed algorithm is proved to be the assignment mechanismachieving the maximum benefit for all nodes, and it can converge quickly. On themaximization of system benefits (system capacity gain minus power consumption), theproposed centralized and distributed algorithms both achieve the maximal intra-matched-pairprofit and maximal inter-matched-pair profit; meanwhile the weighting factor between systemcapacity gain and power consumption, namely unit power cost is an adjustable parameter.Then the additive interference produced by co-channel relay nodes in multi-sourcemulti-relay network is considered. Interferenced nodes list is constructed by each potentialrelay to record the interference to the choosed relays, a joint relay selection and power controlalgorithm is proposed to select the relay which has the maximal cooperative capacity withoutinterfering other destination nodes and selected relay nodes; in each iteration the selectedrelay with maximal interference coefficient would decrease its transmission power in order todecrease its interference coefficient. The algorithm converges when the interference coefficient of each selected relay is zero, namely each selected relay achieves the maximalcooperative capacity without causing interference to other destination nodes and selectedrelay nodes, the maximum network capacity without interference is achieved.Game theory is exploited to analyze the behaviour of duopoly relays when facing thesame users. Different from the relaying service through selling transmission power in manyresearches, the duopoly relays sell their bandwidth with the corresponding throughput, whichis easy for users to monitor and urges the relays to behavior honestly. On the pricecompetition of relays with fixed available bandwidth, the uniqueness of Nash equilibrium isproved, and a distributed discrete price adjustment is proposed to achieve Nash equilibrium;with which both relays sale their whole available bandwidth. On the price competition ofrelays with flexible resale bandwidth, a price strategy guiding the achievement of Nashequilibrium is designed, with which the duopoly relays obtain the maximum profits whilemaintaining their own user groups.