Research On Performance Of Opportunistic Cooperative Communication System And Resource Optimization In Multi-User Cooperative Communication System

In recent years, the cooperative communication has become the research hotspot in the field of communication. Various studies results show that cooperative communications has made a significant improvement in the system indicators, like combating the channel fading, enhancing the channel capacity, spectrum utilization and reliability. As an important part of the cooperative diversity, and due to its excellent performance, simple implementation and extensibility, opportunistic cooperative technology has got more and more attentions. At the meanwhile, how to allocate the limited resources in a reasonable and effective way, that is very important and has practical significance to further improve the performance of wireless cooperative systems. The dissertation deeply studies the key principles of cooperative communications and related technologies firstly. On this basis, we analyze the effect of outdated channel state information on the opportunistic cooperative system from two aspects of system outage probability and diversity order. We also make research for resource optimization problem in multi-user cooperative communication system. Aiming at maximizing system channel capacity, we propose an algorithm based on genetic algorithm. The main works of the thesis are summarized as follows:(1)We make a deep research on the effect of outdated CSI on the performance of an opportunistic cooperative system. We first study the principle of the opportunity cooperative communication and make a brief introduction. After that, we study the effect of outdated CSI on the performance of an opportunistic cooperative system in not considering direct link. On this basis, we focus on the effect of outdated CSI on the performance of an opportunistic cooperative system in considering direct link. We drive an analytical expression for the system outage probability, and then analyses the effect of outdated channel state information on the opportunistic cooperative system for the diversity order. The result of theoretical analysis and computer simulation show that system performance deteriorates with decreasing the correlation coefficient p of the ideal channel and the feedback delay channel, and increases with the increase of number of relay nodes.(2)We also make a deep research for resource optimization problem in multi-user cooperative communication system. We establish a multi-user cooperative communication system model; drive the expression of the channel capacity. According to the principle of genetic algorithm, we construct the chromosome structure which suitable for the model for this paper, propose a new genetic algorithm joint relay selection, power allocation and bandwidth allocation aiming at maximizing system channel capacity. We describe the specific steps of the proposed algorithm in detail, including the selection, crossover and mutation operation. Finally the algorithm is simulated in MATLAB platform, simulation results show that the proposed algorithm can improve the system capacity and close to theoretical upper bound.