The Research On The Key Technology Of Wireless Cooperative Communication System

With the development of wireless communication technology, the demands for high communication quality and performance are growing. In recent years, many new communication technologies and methods are promoted to satisfy these demands such as MIMO and cooperative communication. As is well known, MIMO technology possesses many advantages such as the improvement of system reliability, enhancement of system capacity, high efficiency of frequency bandwidth and so on. However, the communication end can not be equipped with much more antennas for the limitation of size, communication ability, computation ability, energy consumption and so on. So how to use the advantages of MIMO technology in these environments attracted more attention by researchers. And then, the concept of cooperative communication was promoted. In the area of cooperative communication, the system capacity, power allocation, selection of cooperative nodes and the properties of complex cooperative communication system are some key technologies and this paper focuses on these problems.An optimal power allocation algorithm based on capacity for the cooperative communication system was promoted. In the cooperative communication system, if the power is allocated equally in every user's antenna, the capacity can not be improvement optimally. Although some papers optimized the power allocation for the first hop and the second hop, the power of each hop still equally allocated to each user's antenna. To further improve the capacity, in this paper, the optimal power allocation algorithm was promoted, which reallocated the power in each antenna. Simulation results show that the promoted algorithm improves the system performance and enhances the capacity further.A realistic capacity evaluation method for the cellular cooperative communication system with many cooperative nodes in the area of combination of cellular and cooperative communication was promoted. Recently, the multi-hop cellular system was attracted more attention as it can effectively improve the performance of cellular system. However, there are lots of works only adopt multi-hop methods to reduce the path loss without considering the key factors such as the mobility of users in cellular, the number of antennas in receiver, co-channel interference, the scheme of cooperative transmission and so on. In this paper, the factors mentioned above are considered. And at the same time, a realistic cellular cooperative communication system with many cooperative nodes and the users' mobility model in multi-hop cellular system were established, which could further complete the researches on cellular system. Simulation results show that with the fast or slow users'mobility, the capacity of two-hop cellular cooperative communication system is higher than non-cooperative communication system. And during a certain time interval, the capacity ratio between cellular cooperative communication system and non-cooperative communication system fluctuates and the fluctuation of capacity ratio with fast users'mobility is larger than the one with slow users'mobility.Several cooperative nodes selection schemes with tow hop AF (Amplify-and-Forward) scheme that can improve the system performances are promoted. In the cellular cooperative communication system, the adoption of cooperative communication can improve the cellular system performance, but the energy of each user in cellular are limited and then if the using of cooperation without considering the users'energy consumption, a lot of cooperative nodes will die and decrease, which will influence the performance of cellular cooperative communication system. Few papers refer to this problem. In this paper, some cooperative nodes selection schemes with tow hop AF scheme in cellular cooperative communication system are promoted. Simulation results show that the trade-off between system capacity and cell lifetime can be realized effectively.The fast cooperative nodes selection algorithm for general cooperative communication system is promoted. The traditional cooperative nodes selection algorithm always adopts the exhaustive method. When selecting m cooperative nodes from M available cooperative nodes, traditional method needs C (M, m) times, which is high in computation complexity. To decrease the computation complexity, in this paper, two kinds of cooperative nodes selection algorithms based on channel capacity are promoted. Simulation results show that the promoted algorithms not only obtained almost the same channel capacity to traditional way when the same number of cooperative nodes are selected, but also decrease the computation complexity.This paper also investigated the properties of complex cooperative communication system in degree distribution and robustness in the area of combination of complex networks and cooperative communication system. Recently, as an effective method to combat the channel fading, cooperative communication technology has become a hot research area and at the same time, the research on the complex networks has also drawn more attention by researchers. So using the research method on complex networks to investigate the properties of complex cooperative communication system has valuable significance. There are fewer paper refer to this area. In this paper, the model of complex cooperative communication system was established and the properties of degree distribution and robustness of complex cooperative communication system were analyzed. Simulation results show that the degree distribution of complex cooperative communication system is power law and the complex cooperative communication system is robust than non-cooperative communication system in combating the random node failure and attention node attack.