Research On Power Allocation Technology For Wireless Cooperative Communication User Nodes

Cooperative relay technology has been shown to be effective to mitigate the negativeeffects of multi-path fading and to attain broader coverage range, which has wide applicationprospects in the future wireless communication networks. Differing from traditionalsingle-hop networks, a transmission of cooperative relay networks is implementedcooperatively by the source and its relays, so the system resource needs to be allocatedbetween the source and the relays based on the channel status of the links among the source,the relays and the destination, which have a great effect on the system performance. Thechoice of relay nodes and optimum power allocation was discussed in this paper.To begin with, we analyzed the one-way and two-way relay system model and principleof operation. Then, we researched the transmission mechanism and application environmentof three collaboration protocol including the fixed relaying, selection relaying and incrementalrelaying. In addition, compared channel capacity of one-way relay system with two-way relaysystem, the simulation results show that two-way relay system achieve channel capacity thatare substantially larger than the capacity of one-way relay system.Next, we discussed the optimum power allocation problem of three node of two-wayrelay system. We first derived each node optimum power allocation coefficient to minimizethe outage probability and maximize the total capacity respectively under Rayleigh fadingchannel; Then, we studied the performance of outage under Nakagami-m fading channel andderived a lower bound of outage probability. Furthermore, considering a total transmit powerbudget and minimizes the outage probability as the optimization criterion, we discussed anoptimum power allocation method. Simulation results verify the accuracy of theoreticalanalysis.At last, we studied two optimal joint relay selection and power allocation schemes in themulti-node of two-way relay networks. One is in the principle of minimum outage probabilityto conduct the selection of relay nodes, derived closed-form solution of outage probability,based on the optimal choice of relay, the optimal power allocation was conducted; the other isbased on the maximization of the smaller of the received signal-to-noise-ratios (SNRs) of thetwo transceivers under a total transmit power budget, maximize the system capacity as the optimization criterion, and apply SNR balancing scheme with the weighting coefficients tosolving, gained optimal power allocation solution and optimal choice of relay scheme. In themean time, the performance improvements of outage probability and channel capacity withjoint relay selection and power allocation schemes is analyzed.