Research On Cooperative Diversity In Wireless Communications

In wireless communications system, diversity is a kind of effective technique to resist multi-path fading and channel interference. Comparing with time diversity and frequency diversity, space diversity is able to improve the transmission reliability of the system without increasing cost of time and bandwidth for transmission. Cooperative diversity is an emerging technique which makes a user with single transmitter can realize space diversity in distributed communication networks. It collects the nodes in the wireless networks to form a virtual multi-antenna array. As a result, the system exploits the cooperation among all the nodes to obtain diversity gain. In a word, cooperative diversity realized a so-called "virtual" MIMO through a distributed fashion and created a way to apply MIMO in real scenario.Space-Time coding and processing are powerful techniques to obtain multi-antenna diversity gain. Distributed Space-Time Cooperative system is a kind of system which combines Space-Time coding and cooperative diversity. This system is usually adopted in the research on cooperative diversity. First of all, this paper made an introduction to the model and transmission protocol in cooperative diversity system. Secondly, this paper analyzed and simulated the performance of bit-error-rate of the conventional Distributed Space-Time Cooperative system with single relay. Finally, this paper accomplished theoretical analysis and simulation about two issues in single relay distributed Space-Time cooperative field. One issue was how to improve the performance of bit-error-rate of the system when the channel in the system was frequency-selective fading. The scheme in this paper was a joint design which included the coding method, time structure of the transmission and the measure of signal processing at the destination. The other issue was how to resolve the problem of delay synchronization in the system. The solution in this paper was applying front end prefilter which resolved the problem in energy perspective implicitly.