Relay Selection And Powerallocationalgorithms For Two-way Cooperative Communication System

Multi-antenna input-output (MIMO) spatial diversity techniques cansignificantly enhance the system capacity of wireless mobile communication, but it isdifficult to realize because of its high complexity technology and expensive. Thecooperative communication is another effective way to enhance the capacity of thewireless mobile communication system, in a multi-user communication environment,it generates a equivalent virtual MIMO communication environment through a sharedsurrounding the antenna of the mobile communication users, thereby obtain thecorresponding spatial diversity, significantly improve the transmission performanceand capacity of the wireless mobile communication system. This paper focuses onrelay selection algorithm and power allocation scheme within cooperated nodes.Main research contents are as follows:（1）The paper briefly introduces cooperative communication theory foundationknowledge, mainly including wireless channel characteristics and several commonchannel fading models, time diversity, frequency diversity, space diversity and threekinds of merging technology. This paper detailedly introduces three cooperativetransmission protocols, including amplify-and-forward, decode-and-forward andcoding forward.（2）A detailed analysis of several existing relay selection algorithms, this paperproposed relay algorithm, which based on the signal-to-noise ratio and channel gaintwo-way relay selection algorithm. The proposed algorithm considered the directtransmission link between the source node and the destination node. Only when thedirect transmission fails, it uses cooperative communication mode, this explored theproblem of when to cooperate. In addition, it analyzes the outage probabilityperformance of the improved algorithm.（3）This paper studies the problem about transmission power allocation, and theoptimal power allocation called R-OPA is proposed for two-way AF collaborationsystem, the upper bound of average sum-rate is its objective function. In a singlecooperative relay system, the algorithm allocates the transmission power reasonably.In addition, in the premise of R-OPA algorithm, system outage probabilityperformance is analyzed, and closed expressions of upper and lower bounds of theoutage probability are obtained. Simulation results show that the improved relay selection algorithm can getabout4dB gain, and the total rate of the system upgraded to1.4. Power allocationalgorithm is proposed in this paper, which is based on channel statisticalcharacteristics and doesn’t need to update the channel state information in real-time.It has low complexity characteristics. And compared with equal power allocationalgorithm, it can improve the system average rate and reduce the outage probability.