Research On Some Issues Of Multi-Input Multi-Output Wireless Communication Systems

The support of the multimedia service (including speech, image and video etc.) in the wireless channel is the trend of the communication system. There is an increasing capacity demand for high speed wireless data access system with continusly increasing of the amount of subscribers. It may not be efficient or even practicable to expand the channel capacity by purely increasing the bandwidth and transmit power due to the limitation of the spectral resources. The establishment and development of the multi-antenna information theory have revealed that the MIMO (Multi-Input Multi-Output) technique can provide extraordinarily high spectral efficiency gain over the traditional single antenna systems, which have also laid the theoretical foundation for the invention and applications of space-time codes.This dissertation focuses on several issues of wireless MIMO implementation. The main contributions consists the following aspects.In order to reduce the computational complexity of the maximum likelihood (ML) detection of unitary space-time codes, a tree-structured unitary space-time constellation is proposed. The minimum average distortion design criterion and relevant iterative design algorithm are also proposed. The exhaustive search used in ML is avoided in the tree search decoding (TSD) algorithm, and hence resulted in much lower decoding complexity. Basing on the tree-structured unitary space-time constellation, we proposed the concept of adjacent sub tree and the adjacent sub tree joint decoding (ASTJD) algorithm. Since it's still possible for the received signal to be correctly decoded with an error decision of the sub tree root, the ASTJD can remarkably improves the performance of purely tree search method. Those non-ASTs are excluded during the decoding search process, so that the complexity of ASTJD is still less than that of ML.The tree-structured unitary space-time constellation with overlapped sub trees is presented for the unitary space-time signal set with circulant correlation structure. The tree-structured constellation is constructed according to the relative position of the root and leaf nodes in only one sub tree. The decoding performance can be improved by increasing the amount of the overlapped leaf nodes between sub trees.Based on the multi-variate statistical analysis theory and a recursive analysis method, the error probability performance of the layered space-time detection algorithms with DFE structure is analyzed. Under the assumptions of uncorrelated flat Rayleigh fading and QPSK modulation, the nearly exact SEP (symbol error probability) performance of ZF-DFE (Zero Forcing-Decision Feedback Equalization) and MMSE-DFE (Minimum Mean Square Error-Decision Feedback Equalization) detection algorithms are given. The simulation results are also provided to demonstrate the...