Research On Cooperative Relay Strategy And Resource Allocation For Wireless Communication Networks

Wireless cooperative relay technology has been proposed for wireless networkapplications to enhance system coverage, link reliability and data transmission, to lowerterminal transmit power and to decrease bit error rate (BER) in recent years. This noveltechnology has attracted extensive industrial and academic attention. In the future wirelesscommunication networks, the performance in cooperative communication depends oncareful resource allocation, such as relay selection and power control. MIMO relaychannels, which combine the multiple antenna system and the relay, can improve thespectral efficiency of relay network. This thesis focuses on the themes of the performanceanalysis of relay transmission, relay node selection and resources allocation in the wirelesscooperative relay networks. Detailed contents are as follows:Firstly, we considered a three-node wireless relay channel consisting of a source, adestination and a relay in a Rayleigh-fading environment. The consumption of time andpower by the relay operating in the full-duplex mode for relaying data was discussed, whenthe capacity of the channel between the relay and the destination (RD channel) is biggerthan that of the channel between the source and the relay (SR channel). It proves that theratio of the relay-transmit period to the given time window could be decreased in the costof consuming more energy in that case. Then, the upper and lower bounds (ULBs) on thecapacity for the relay channel were also explored, when the relay operates in half duplexmode and the source can only send in the relay-receive period.Secondly, we proposed a distributed buyer and seller game theoretical frameworkover multi-user cooperative communication networks to achieve optimal relay selectionand power allocation based on user’s link quality requirement. The power of the sourcenodes and relay nodes were jointly considered to benefit the utilities of source nodes andthe relay nodes in this paper. The proposed approach not only helps the source find therelays at relatively better locations and allocates an optimal amount of power among thesource node and the relays for minimization of the source nodes payment, but also helpsthe competing relays maximize their own utilities by asking the optimal prices.Furthermore, the optimal prices could be decided by the local channel state information(CSI) and price per unit power of other relays. If the total number of available relay nodesincreases for the same data transimission, the energy consumption of the whole networks can be decreased subject to the signal to noise ratio constraint.Thirdly, based on Nash bargaining game, the problem of resource sharing amongselfish nodes in wireless cooperative networks is considered. In the system, each node canact as a source as well as a potential relay, and both nodes are willing to achieve an extrarate increase by jointly adjusting their channel bandwidth and power levels for cooperativerelaying. First, a two-user algorithm is proposed to bargain joint bandwidth and powerallocation (JBPA) between two users. Then a multiuser bargaining algorithm is developedbased on the Hungarian method. Nash bargaining solution (NBS) is applied to formulatethe JBPA problem to guarantee fairness. And, the optimal coalitions are formed by usingthe Hungarian method, such that the overall network rate increase is also maximized.Simulation results indicate that the proposed algorithm can guarantee fairness betweencooperative partners, but also maximize the overall network rate increase.In the end, we exploited node cooperation for achieving physical layer based securityin a cooperative wireless network. The case of one source-destination pair with the help ofmultiple cooperating nodes in the presence of one eavesdropper was considered to improvethe performance of secure wireless communications. A novel cooperative schemeDecode-and-forward plus cooperative jamming (DFCJ) was proposed. In this scheme, therelay nodes transmit a weighted version of the source signals plus a common weightedjamming signal to confound the eavesdropper. The novel system design was proposed todetermine cooperative node weights and the allocation of transmit power. For DFCJ, in thecondition of the complete nulling of jamming signals at the destination, a closed-formsolution was firstly obtained to minimize the total transmit power subject to a secrecy rateconstraint, then, a optimal power allocation was obtained via iterative algorithms tomaximize the achievable secrecy rate subject to a total transmit power constraint. Thenumerical evaluation of the transmit power and the obtained secrecy rate results showedthat more cooperation nodes may be involved into cooperation in the DFCJ scheme, and heperformance of wireless physical layer security can been furtherly improved, as comparedto the DF and CJ scheme.