Multi-user Cooperative Diversity Based On Space-time Coding

It is well known that multiple-input multiple-output (MIMO) system using space-time coding (STC) technique can improve the reliability of the communication system over fading channels by combining antenna arrays with encoding theory. Therefore, STC technique has become one of the key techniques of future wireless communication systems. By allowing the single-antenna user to share each other's antenna, muti-user cooperative diversity system realizes a virtual MIMO system and therefore provides wider application range for MIMO technique. The recently proposed perfect space-time block codes (Perfect STBCs), which have full rate, full diversity-gain and achieve the optimal Diversity-Multiplexing (D-M) gain tradeoff, are one of the STCs with the best comprehensive performance. However, due to the high computational complexity of detection, Perfect STBCs are impractical for many applications.This paper mainly works on the low-complexity detection algorithm for Perfect STBCs and its application in cooperative diversity system.At first, MIMO system model and STC design criterion are briefly introduced in this paper. Then the optimal D-M tradeoff in MIMO system is provided. Based on the above theories, the performances of Alamouti Space-Time Code, Layered Space-Time (LST) scheme and Perfect STBC are analyzed and compared. After deep study of the existed detection algorithm, an efficient detection algorithm based on codes relation and lattice reduction aided Probabilistic Data Association (PDA) detection algorithm are proposed for Perfect STBCs. Simulation results demonstrate that while ensuring the decoding accuracy, the proposed two algorithms could reduce the computational complexity.In multi-user cooperative system, three basic transmission schemes——Amplify and Forward (AF), Decode and Forward (DF) and Coded Cooperation (CC) are briefly introduced at the beginning. After that, through bringing Perfect STBC into the cooperative system, a new cooperative transmission scheme based on AF and DF is proposed in this paper. Simulation results demonstrate that the proposed transmission scheme could ensure the transmission speed and transmission quality at the same time, and thus improve the overall performance of the system.