Research On Space-Time Coding Technology In Mimo And Cooperative Relay Systems

With rapid development of Mobile Internet technology and multimedia services, it is an issue problem for next generation wireless communication to increase the effectiveness and reliability of wireless communication system. Multiple-Input Multiple-Output (MIMO) technology is able to extremely upgrade the spectral efficiency, without using more bandwidth or transmit power. And MIMO is recognized as a key technology for next generation wireless communication system. Every node in a Cooperative communication system can share its antenna with others, and a Virtual MIMO system is formed. The system can also achieve good performance in spatial diversity and spectral efficiency. Space-Time Coding technology can bring great performance improvement for MIMO and Virtual MIMO systems, and it has also been widely applied recently. This paper has made a deeply study of Space-Time Coding technology in MIMO and Cooperative communication systems.Under the support of National Significant Science and Technology Special (2009ZX03002-009-01), and The National Natural Science Foundation of China (60872149,60672132), this paper have made a research of Space-Time Coding technology in MIMO and Cooperative communication systems. The main works and innovations can be concluded as follows:(1)Extended Balanced Space-Time Block Coding (EBSTBC) is a special Space-Time Coding scheme considering channel state information available for transmitter. This scheme can guarantee full-diversity while achieving coding rate of1,what’s more, it is also suitable for the base station with any number of transmit antenna. But exhausting search method is applied to calculate the feedback information, which is of great complexity. In order to solve the problem, this paper proposed a low-complexity calculating scheme of feedback information for EBSTBC. First of all, the expression formula correlated to feedback information was investigated and analyzed, and the feedback information for this transmission can be decided due to two-step optimization scheme. Comparing to the former scheme, the proposed scheme can greatly decrease the complexity for calculating feedback information, at the cost of little loss in reliability of the system.(2) Full-Rate Full-Diversity Space-Time Block Coding (FRFD-STBC) has the property of full rate and full diversity, however, its decoding procedure is very complex, and the complexity order is proportional to the square of the modulation order. For the purpose of cutting down the complexity of decoding of FRFD-STBC system, a novel code-and-decode scheme based on limited feedback pre-coding technology is proposed. After carefully design of pre-coding parameter, the real part and the imaginary part of the signal can keep orthogonal during the transmission. And the real part and the imaginary part of the signal can be decoded separately. The complexity order of the proposed scheme is proportional to the linear of the modulation order. Comparing to FRFD-STBC scheme, the proposed scheme can greatly decrease the decoding complexity at the cost of a few bits feedback.(3) In the cooperative networks with several relay nodes, distributed space-time coding based on generalized ABBA (GABBA) codes can be applied to the scenes with more than2relay nodes, and this scheme can also guarantee coding rate. But interference is unavoidable for GABBA codes, and it may affect the system performance. For the purpose of further enhancing the reliability, channel state information is made full use of, an improved scheme with1-bit feedback is proposed, and the feedback information is extended to case of phase codebook. After deeply investigation and analysis of interference term expression, feedback information is design according to maximizing signal to interface plus noise ratio. Compared with the existing scheme, the proposed proposal can achieve a better bit error rate while using one-bit feedback information.(4) Aiming at the problem that only1/2transmit efficiency is achieved for conventional space-time coding in half-duplex multi-relay networks, we proposed an efficient distributed space-time coding scheme based on double-relay selection. Successive relaying mechanism is adopted, and every two available relays are selected to forward signal according to some kind of double-relay selection criterion. The forwarding strategy is amplify-and-forward based on Alamouti distributed space-time coding. To cancel the inter-relay interference brought by successive relaying and insure the reliability, a successive interference cancellation scheme, a signal detection procedure and several double-relay selection schemes are given. The analysis and simulations indicate that the transmit efficiency of the proposed scheme can reach nearly1without any loss in diversity order, and the proposed scheme is able to achieve lower bit-error rate comparing to conventional scheme. Meanwhile, the employ of double-relay selection make the proposed scheme more flexible and applicable for multi-relay networks.