Power Allocation Strategy In Wireless Cooperative Communication System

Mobile communication has been developing rapidly since the 21 st century, especially in recent years. The development of mobile communication is irresistible. By the end of 2014 mobile phone users reached 1.286 billion, which puts forward higher requirements for future communication with high-speed wireless rate, large capacity, diversification of development and planning. As a multi-antenna extension technology, cooperative communication is a new research focus in the field, which can avoid the huge cost of increasing the number of base stations, without being limited by the volume of mobile terminals and the power constraints.The idea of cooperative communication is to use multiple nodes in the network to achieve a shared transmission path, so as to improve the throughput of the whole network, which has a very broad application prospects in the future communication field. Transmission bandwidth is divided into a series of sub-carriers orthogonal set of non-overlapping by Orthogonal Frequency Division Multiple Access technology.Different sets of subcarriers are assigned to different users to achieve multiple access with multi-user access, which can not only improve the spectrum efficiency but also avoid the multiple access interference under ideal synchronization system. Therefore the cooperative communication technology and OFDMA technology are combined to improve the spectrum efficiency, increase the system capacity,improve service quality and reliability of the system, and the system cost is reduced greatly.However, wireless cooperative OFDMA system contains power, time, frequency, size and other wireless resource. Among them the power resource is very important for data transmission. In this thesis, we put the power allocation relay selection and subcarrier pairing together in order to achieve good system performance.Firstly, the thesis gives a brief introduction of the principle and the significance development of the cooperative communication. on this basis, research on power allocation strategy in cooperative communication is introduced.Secondly, it analyzed the cooperative communication system model and collaborative strategies. The model and principle of collaboration systems are introduced at first. Then several common collaboration strategy and outage probability performance is derived.In the next place, study the relay selection in cooperative communication systems.Mainly introduces the relay node selection method based on the outage probability, the BER performance and the capacity threshold, choose the appropriate number of relay to take participate in the cooperative communications, and through modeling and system simulation data to analysis and verification.Finally, the thesis of cooperative OFDMA communication system focuses on the power allocation. The cooperation strategy of the second chapter and the relay node selection of thethird chapter are applied to the OFDMA system, which studies the power allocation strategy for OFDMA cooperative communication system to improve system capacity performance based on AF mode. This chapter first to start the relay selection and subcarrier pairing, and then to select nodes and carrier of power allocation, and use MATLAB simulation prove that the capacity of the system increases, the complexity of the system reduces, and the QOS of the system improves. It has a good prospect in the future of wireless communication field.