Performance Analysis Of Cooperative Diversity Techniques In Cooperative And Relay Communications

Cooperative transmissions in cooperative communications mostly base on relay transmissions, and have an obvious advantage of cooperative diversity, comparing with traditional communications. Especially, the cooperative diversity gains of physical layer (PHY) could help enhance the stability of system performances. How to explore the cooperative diversity gains in cooperative and relay communications is the object in mind through the whole dissertation. Considering that the multiple input multiple output (MIMO) techniques have been widely applied in future mobile communications, we propose and analyze some cooperative diversity transmission schemes in several MIMO relay scenes.The research approach taken in the dissertation is as follows:proposing the cooperative diversity transmission scheme, deriving the random variable's statistical characteristics, applying the mathematical theory to derive the outage probability and symbol error rate, and analyzing the performance.The main research content is that proposing several cooperative diversity transmission schemes, which include the new transmit antenna selection strategies (TAS), the transmission scheme combining with TAS and relay selection, and the novel transmission scheme with orthogonal space-time block codes (OSTBC), the analyzing their performances. The research content mainly covers the following topics:Research on transmit antenna selection in two-hop single MIMO relaying. In the two-hop single MIMO relaying, we propose the new TAS strategies, and apply them to the nonregenerative relay and regenerative relay, analyzing their performances. The transmission schemes combining proposed TAS strategies and nonregenerative relay protocol or regenerative relay protocol are designed in two-hop single MIMO relaying with direct link. Comparing with the TAS strategies in reference papers, our proposed schemes take restricts in the practical systems into account, and have a tradeoff between the transmission performance and the implementation complexity. As a result, our scheme could achieve the full diversity order in some antenna configurations. To further analyze our TAS strategies, we then apply the TAS strategy in the two-hop single MIMO relaying without direct link, the performance analysis shows that the transmission scheme can achieve the full diversity order; According to the goal of minimizing the symbol error rate, the optimal relay selection, expecting to improve the end-to-end performance, has been solved and the resulting selection rule refers to the antenna configurations among the communication nodes. Specifically, when antenna configurations between two-hop links are not balanced, the selected relay should be closer to the node with fewer antennas, and when antenna configurations between two-hop links are balanced, the selected relay should be near the middle of the line between source node and destination node.Research on transmit antenna selection and relay selection in two-hop multiple MIMO relaying. We propose the new transmission scheme combining with TAS and relay selection, and analyze its performance. In the process of analysis in high signal noise ratio (SNR) regime, we approach the practical symbol error rate by the upper bound and lower bound on the symbol error rate, focusing on the accuracy of exponent of average SNR in the expression. As a result, the consistency on the exponent leads to the conclusion that our proposed scheme can achieve the full diversity order. The result shows that the achieved diversity order depends on the total number of all relays' antennas rather than the individual number of each relay's antennas.Research on orthogonal space-time block codes transmissions in two-hop single MIMO relaying. We propose a novel OSTBC transmission scheme and analyze its asymptotic performance. Our proposed scheme explores the instantaneous channel state information (CSI) of source-to-relay channel, and reconstructs the compound source-relay-destination channel, making the transmitted symbols in OSTBC code words travel in the equivalent parallel non-interacting subchannels. This kind of design make the proposed scheme can achieve the full diversity order, and its performance better than that of the existing OSTBC transmission scheme.