Performance Analysis And Power Allocation In Relay-aided Cellular System

With the rapid development of wireless communication technology in recent decades and the sustained growth in the number of mobile users worldwide, the quality expectations of wireless communication users on the business experience are getting higher and higher. In order to provide faster data rate, greater system capacity and a better user experience, and to ensure the transmission of multimedia new business, the technologies of OFDMA, MIMO and Relay in cellular networks have been introduced. Thus, performance of the cellular system and robustness of communication link are effectively improved.This thesis introduces the theory of related technologies for OFDMA, MIMO channel capacity and the scenario of relay system. After the analysis of distance selection method, a new relay selection method is proposed which achieves further improvement on the system capacity. The performance of the traditional cellular system compares with relay-aided system show that using the new relay selection method, the capacity of OFDMA-MIMO cellular system can be increased to30%or even more; the system performance is optimized if the cell radius increases; if the ratio of two time slots is2, system obtains the optimal performance; in addition, the requirements of mobile users' transmission power can be reduced if the power ratio of the source and the relay is appropriate.This thesis discusses the power allocation algorithm in OFDMA-MIMO fixed relay system with limited power. After the analysis of Lagrange algorithm, a computer-aided algorithm with a simpler structure is provided to achieve the maximum capacity of the system. Simulation results show that the relay location, the antennas number and the minimum power component have great impact on system capacity. Finally, if the minimum power component is10-2, the algorithm not only avoids the high complexity of the algorithm, but also can keep good balance between system capacity and complexity.