Research On Optimal Transmission And Receive For MIMO Wireless Communication Systems

Mmulti-in and multi-output (MIMO) technology, which applies space-time processing technology and employs multi-element antenna arrays (MEA) at both transmit and receive sites, can can be used to increase channel capacity and to improve reliability significantly in high-scattering wireless propagation environments. In recent years, MIMO technology has been well-documented on the assumption that the channel is independent and identically distributed Rayleigh flat fading channel. But the channels between different transmit and receive antennas are always correlative in realistic propagation environments, which would decrease system performance. Based on the above analysis, this dissertation undertakes some research work on optimal space-time transmissions and receives under MIMO spatial fading correlation channels, with the support from the National Natural Science of China under Grant No. 60496315 and the National High Technology Program of China under Grant No. 2003AA12331005.Firstly, two MIMO spatial fading correlation channel models are discussed. One is the ray-tracking METRA model, also called as Kronecker model.The other is the virtual channel representation (VCR) model based on the scattering descriptions.The features, numbers of model parameter and degree of approximation are compared. These models quantify the effects of fading correlation by capturing the second order statistical characterization. Furthermore, the capability of achieving spatial multiplexing and spatial diversity gains in spatial correlation channels is analytically investigated based on mutual information and PEP criterions respectly. The analysis provided the foundation for subsequent researchs.Based on covariance feedback or bandwidth-constrainted feedback, an adaptive modulation code (AMC) scheme combing 2D eigen-beamforming and OSTBC is presented to increase reliability and throughput. The optimal beamforming and power allocation across eigen-beams is derived to minimize the PEP. The power allocation obeys to water-filling principles. A switch scheme in power allocation is applied to avoid power waste in the invalid beam when the correlation is serious. An intitute relation between constellation levels and the correlation degrees is constructed where the correlation degrees are quantified by the two strongest eigenvalues of correlation matrix. Through the transformation effects of 2D-EBF, the system achieves full-rate with any numbers of transmit antenna. With the orthogonal structures of STC and the orthogonality berween the eigen-beams, the decoder complexity is just linear. The scheme is attractive in practice.A MIMO-OFDM system, which concatenates TCM and OSTBC with time-domain EBF which juse requires one IFFT, is presented in frepuency selectivity correlation fading channel. TCM is the outer code to achieve code gain. And the OSTBC is used as the intter code to achieve diversity gain and provide low complexity. Two cases with or without interleaving are considered. And power allocation algorithms and TCM design criteria are derived respectively to minimize error probility. The two cases with or without interleaving achieves code gains from free distance or product-sum distance respectively.At high SNR, two order beamforming diversity and full receive diversity are achieved, and the case with interleaving still achieves build-in-time diversity. Furthermore, the code distance is used in power allocation algorithms to lower the SNR threshold of achieving beamforming diversity. Compared with the scheme withput interleaving, this scheme with interleaving is more available to quick-changing fading and has better performance. A spectrum-efficient block-ordered joint beamforming linear disperson code (BO-JBLDC) is presented to explore spatial multiplexing gain. The transmit antennas are partitioned into some blocks, which can decrease decode complexity and increase code gain. Then LDC is applied on each block independently. To enhance the order of spatial diversity in the presence of deteriorative fading correlation as well as inter-substream interference, the proposed BO-JBLDC employs joinlty transmit and receive EBF together with post-ordered iterative decoding scheme. Interference suppression and canceling are used to extract out the inter-substream interference. Then, sphere decoder is used to decode each ordered block. Furthermore, iterative decoding is applied to achieve full receive diversity for each group. The results show that BO-JBLDC can lower complexity and improve spectral efficiency and reliability significantly.A spectrum-efficient noncoherent Cayley-DUSTM virtual transmission scheme is presented based on VCR. Differential schemes are more desirable for use on wireless links where channel tracking is undesirable or infeasible, either because of rapid changes in the channel characteristics or because of limited system resources. Cayley transformation maps the highly nonlinear Stiefel manifold of unitary matrices to the linear space of skew-Hermitian matrices. This transformation leads to a simple linear constellation structure in the Cayley transform domain and to an information-theoretic design criterion based on emulating a Cauchy random matrix. And a modulation scheme like LDC is empolyed. The design critria and method of base-matrixs and modulation symbols set are also gived. The results shows high spectrum efficience and polynomial-time near-maximum-likelihood decoding based on linear equations representation.