Research On MIMO And Its Related Technologies

As the rapid growth of user demand on mobile multimedia services, to increase the data rate of wireless link remarkably has become one of the crucial problems to be resolved Multiple Input Multiple Output (MIMO), which has the features of spatial multiplexing and spatial diversity, can increase the transmission efficiency of wireless communication highly without occupying more bandwidth and transmit power. Therefore, it becomes the mandatory technique for the next generation wireless communication systems. Small terminals in cooperative communication has been proposed to share their antennas, which forms virtual MIMO system and provides a solution for the application of MIMO in small mobile terminals The relay node in network code, having the spatial multiplexing feature of MIMO, retransmits the signals of multiple source and the network throughput is greatly increased. MIMO cooperative communication and network coding are investigated mainly in this paper.Under the support of National Science and Technology Major Project of China (2009ZX03002-009-01) and National Science Foundation of China (60672132?60872149), MIMO and its related technologies are investigated. The main contributions of the dissertation are as follows:(1) The performance of Orthogonalized Spatial Multiplexing (OSM) scheme in MIMO system can be significantly improved by traditional power allocation precoding. However, additional feedback information is needed and the computational complexity of feedback information is increased with the increase of modulation order. For these problems, a novel phase rotation precoding is proposed for OSM system in this paper, in which a proper rotation is set at the imaginary part of modulated signals. Compared to the power allocation precoding of OSM scheme, the feedback information is reduced and the computational complexity of feedback information is decreased in the proposed scheme with the same performance. In order to enhance the performance of the extending orthogonal space-time block code in MIMO system, an improved extending orthogonal space-time block code is proposed in this paper. Each signal of branches of some OSTBCs are rotated certain angles in the proposed scheme to maximize the effective channel gain. The effective channel gain is increased and the system performance is enhanced. Moreover, as the feedback information is directly calculated in the proposed scheme and there is no need to search all possible feedback vectors, the computational complexity of feedback information is greatly reduced. Semiorthogonal Algebraic Space-Time (SAST) code extends the space time code of full rate and 1 rate coding to MIMO system with arbitrary even number transmit antennas. Research shows that, for 4 X 4 SAST code, the real part and the imaginary part of the first half and the second half of the transmitted signal vectors are mutually orthogonal when Quadrature Amplitude Modulation (QAM) is adopted. Using this orthogonal property, a new decoding scheme is proposed for 4 X 4 SAST code with QAM modulated signals, in which the real part and the imaginary part of the first half and the second half of the transmitted signal vector are decoded respectively. Analysis shows that the decoding complexity is reduced proportionally to the modulation order. The full rate and full diversity could be achieved by Rate-2 Space-Time Block Code (R2-STBC), whereas the decoding complexity is proportional to the square of the modulation order. A Rate-2 Space-Time Block Code with Phase Rotation (PR-R2-STBC) is proposed which can reduce the decoding complexity to be proportional to the modulation order. Part of the transmitted signals is rotated by a certain angle according to the feedback information, and the pairwise orthogonal between the transmitted signals is realized in the proposed scheme, so that the decoding complexity is proportional to the modulation order. Simulation results have demonstrated that, compared to R2-STBC, the decoding complexity is reduced greatly in proposed code only with several bit feedback while maintaining the same performance. (2) Cooperative communication is a virtual MIMO technology. In order to improve the performance of Co-ordinate Interleaved Distributed Space-Time Code (CIDSTC) in cooperative communication, Co-ordinate Interleaved Distributed Space-Time Code based on Phase Rotation (PR-CIDSTC) is proposed, in which relays rotate their transmitted signals with certain angles to minimize Pair Error Probability (PEP) according to the Channel State Information (CSI) at the transmitter. The PEP of the proposed scheme is decreased and the performance is enhanced. The CSI is not taken into account in Multi-Hop Alamouti Amplify and Forward (AAF-MH) cooperation protocol. For this problem, Multi-hop Alamouti Amplify and Forward with Phase Rotation (AAF-MH-PR) cooperative scheme is proposed in this paper. The transmited signals of one relay node are rotated certain angles, which are designed to maximize the PEP and feedback back to transmitter. So, the PEP of AAF-MH-PR is decreased and the reliability is enhanced.(3) Theoretical maximun capacity can be reached in network coding, which combines the concept of coding and routing. Amplify-and-Forward protocol is adopted in Overlapped Transmission scheme for Analog Network Coding (ANC-OT), and the propagation of noises can't be avoided at relay node. For this problem, overlapped transmission scheme for network coding with decode-and-forward protocol is proposed in this paper in order to improve the spatial multiplexing gain of virtual MIMO. Whether to forward the source signals is determined by the decoding results at the relay node in the proposed scheme Theoretical analysis show that the proposed scheme outperforms ANC-OT in the average mutual information and reliability.