Research On Cooperative Communication Based On Optimal Relay Node Selection

Multiple-input multiple-output(MIMO)is a technology which can obtain space diversity gain by embedding a plurality of antennas in modern wireless transceiver.However,under the control of the size and cost of wireless devices,a single terminal placed more antennas is impractical.Collaborative communication as a relay transmission can make the network nodes constitute a distributed antenna system,nodes cooperate with each other to obtain the performance of the system which is similar to MIMO,thus greatly improve system capacity and reduce the occurrence of interruption.At present,the research of cooperative communication is mainly focused on relay node selection strategy,power allocation and network coding,etc.In this paper,we mainly study the relay node selection strategy of cooperative communication,and the theoretical and innovative points of the research are as follows:Firstly,this paper summarizes the basic theory of cooperative communication,mainly introduces the complex and changeable channel characteristics of wireless networks.The paper describes three kinds of processing protocols of cooperative transmission,and the diversity of merging technology for suppression of fading and illustrates their advantages and disadvantages.Considering how to evaluate system,notes the channel capacity,the interrupt probability and the average error probability of three performance metrics.Secondly,this paper studies the one-way relay selection strategy for cooperative communication.The transmission characteristics of AF and DF are analyzed in theory,simulation results show that the DF transmission compared to the AF transmission on the link quality requirements are higher,and more suitable for working in the high SNR region.Based on the one-way cooperative ARS-M adaptive multi relay selection algorithm,an improved ARS-M relay selection algorithm is proposed.Compared to the previous algorithm,the number of relay nodes in multi-relay cooperative is defined,and the occurrence of more cooperative relaying is avoided.And the relay selection process is according to the different forwarding ways of AF and DF to choose different relay selection strategy,which can more fully reflect their own advantages.Simulation results show that the proposed algorithm can effectively reduce the occurrence of the system outage events under the premise of the reasonable allocation of the relay resources.Finally,this paper studies the two-way relay selection strategy of cooperative communication.The main work of this part is the research on the single relay selection of the two-way multi relay cooperative network under the AF forwarding mode.The paper comes up with a minimizing outage probability of relay selection algorithm.In order to optimize the outage probability as the goal,derives two-way amplify and forward relay network outage probability expressions,and then selects the minimum outage probability of relay nodes.In order to reduce the relay selection of computational complexity and the number of comparisons,we need to set a signal-to-noise threshold,the threshold values for the average value of all the relay signal-to-noise ratio,removes a portion of relay nodes with poor link quality by repeatedly comparing the difference relay nodes,then selects the minimum outage probability of relay nodes.Taking into account the power allocation problem,a power allocation algorithm based on optimal capacity is proposed,which combines the obtained power with the relay selection strategy to optimize the performance of the system.Simulation results show that the joint optimization strategy can be used to enhance the overall rate of the two-way AF relay system,and it also can reduce the outage probability.