The Research Of Performance And Power Allocation In Single Relay Cooperative Communication System

Abstract:With the growth of demand for new wireless communication business, wireless communication technology is develop rapidly towards the direction of high-speed, multi-service and wide bandwidth. In wireless communication system, the channel path loss and fading are affects the quality of the signal, the diversity technique can effectively combat channel fading. Each neighboring mobile terminal shared their antennas to transmit information in order to achieve a virtual multiple antenna arrays. Because it can obtain spatial diversity gain and improve the communication system spectral efficiency and reliability in the cooperative diversity multi-user communication system.In this paper, we mainly studied amplify-and-forward, decode-and-forward and code cooperation three cooperative diversity protocols. Firstly, we introduce the background and significance of cooperative diversity and the current research progress. The characteristics of wireless channel, classification of diversity and diversity combining technology are detailed description. Also, we analyze the Rayleigh fading channel models and the works of three cooperative diversity protocols. It is the foundation of subsequent system performance analysis.Then, the moment generating function is introduced to study the system performance of wireless fading channel. We derive amplify-and-forward and decode-and-forward mathematical model of the system symbol error rate in Rayleigh fading channel. So we get the closed form expression between the system symbol error rate and SNR in AF and DF protocols with M-PSK and M-QAM signals. The performance of the two protocols in different modulation system is simulated analysis and compared in Rayleigh fading channel. It has very important theoretical significance for further research of amplify-and-forward and decode-and-forward protocols.Finally, the power allocation optimization for coded cooperative system has been studied. Under the condition of coded cooperation using RCPC coding in Rayleigh fading channels, we derive the outage probability mathematical model by Taylor series expansion and high SNR approximation. So we obtained the outage probability closed-form expressions which reveal the relationship between the outage probability and other three variables(outage rate, collaborative degree and power allocation coefficient). By comparing the simulation analysis, we obtain the optimal power allocation coefficient and the effect of outage rate and collaborative degree for the communication system performance. Optimal power allocation can reduce system power consumption by rational use the each mobile terminal resources. So it can enhance the capacity of the system and maximize the performance of the communication network.