Research On Energy Efficiency Based Cooperative Communication System

Over the years, the development of wireless communication has always stressed to provide users3A Service (Anytime, Anywhere, Any media). The user at anytime, anywhere through any medium can get high-quality communication services. With the rapid development of communication, the investment in mobile terminals, the number of base stations, data centers and other communications equipment is increasing. The proportion energy consumption of the communication industry accounted for society’s total energy consumption is growing. Many standardization organizations and operators are beginning to concern the energy efficiency of the next generation wireless communications technology. Many researches are in progress aimed at improving the energy efficiency of wireless communication networks. With the continuous progress of the construction of resource-saving society, we can foresee that the requirement of energy efficiency in communication systems will become increasingly strict in the future of wireless communication networks and devices.MIMO (multiple-input multiple-output) can obtain space diversity by employing multiple antennas at the transmitter and the receiver, which will combat multipath fading effectively. However, due to the restricted size and complexity of the wireless terminal device, it is impractical for terminals to employ multiple antennas in some scenarios. A. Sendonaris et al in2002propose cooperative communication technologies [2][3]. By use the broadcast nature of wireless channels, the single-antenna terminals in a multi-user scenario can share each other’s antenna to form a virtual MIMO system. Cooperative communication can improve the reliability of communication system and improve system performance and extend the coverage of wireless communication. This paper focuses on relay selection and power allocation strategies based on energy efficiency in cooperative communication. This work has a strong theoretical significance and application prospects.In this thesis, we firstly introduce the basic concepts and principles of cooperative communication. We discuss the hot research issues related to cooperative communication. Then, we propose a single relay node cooperative communication systems based on the energy efficiency. The transmission system can operate in two different modes, direct transmission mode and the cooperation mode. The optimum transmission mode will be chosen based on the energy efficiency of the system. Simulation results show that the position of the relay node cans impact energy efficiency of the system a lot. And the different relay selection strategies between the system based on performance and energy efficiency are analyzed.Secondly, we consider multi-relay nodes cooperative relay system based on energy efficiency. All relay nodes are assumed to be independent and identically distributed. We first choose the optimal transmission mode based on energy efficiency of different transmission link. To optimize the system’s energy efficiency, we obtain the system optimal transmission power under different transmission mode. In cooperative mode transmission, the optimum power allocation factor is given.Finally, in the case of multiple relay nodes are randomly distributed, we use particle swarm optimization algorithm to analyze the energy efficiency of different power allocation schemes. Then we study how the distribution of the relay nodes can affect energy efficiency of the system. Simulation results indicate that the energy efficiency performance of proposed power allocation scheme is better than the other schemes.