Research On Signal Detection Technique Of Space-Time Layered Structure Over MIMO System

Wireless multiple-input multiple-output (MIMO) antenna systems offer significant improvements in performance and capacity when used in wireless communications and have received much attention recently. The MIMO exploits the space resource to improve the channel capacity effectively without additional frequency spectrum and transmission power. A typical MIMO multiplexing technique is Bell laboratories layered space-time (BLAST) architecture. This dissertation makes researches on signal detection techniques for MIMO systems over independent flat fading channels and frequency-selective fading channels aiming at improving the performance of detecting algorithm, ameliorating the Bit Error Rate (BER) performance, and decreasing the computational complexity, without loss in spectrum efficiency. The study focused on some key signal detection technologies of MIMO system with space-time layered structure, such as GOLDEN detection technique, sorted QR decomposition detection technique, adaptive RLS ordered decision feedback equalization detection technique. The thesis work can be summarized as follows.An improved MMSE V-BLAST algorithm based on iterative QR decomposition is proposed to overcome the shortcoming of increasing system detection complexity caused by a lot of pseudo-inverses operations when detecting using MMSE detection algorithm in MIMO system receiver. The complexity is reduced and the performance is improved. The MMSE V-BLAST algorithm extended the system's adaptability, because of avoiding the pseudo-inverse operations and the system needn't satisfy the requirements that the number of transmitted antennas must less then that of received antennas.A fast square-root detection algorithm for V-BLAST was proposed. The algorithm aimed at the question of high complexity when traditional square-root detection algorithm detecting in MIMO receivers. It simplified the computing process of traditional square-root detection algorithm and proposed a parallel processing algorithm of judged signal's feedback and received signal's interference cancellation. The detection complexity of the algorithm was reduced, while the detection performances retain. It has good adaptability for the system with response in time.In view of the fact that the sorted QR decomposition (SQRD) algorithm for multiple input multiple output (MIMO) communication detection has a higher bit error rate when working in multi-path Rayleigh slow fading channels, the paper proposes a serial interference cancellation (SIC) algorithm for MIMO detection based on column orthogonal (CO) transform named COSIC. The COSIC algorithm transforms the channel matrix column orthogonally to avoid solving the upper triangular matrix. In the processing of judging signals, it takes the output of the judged signals which are transmitted by the channel matrix as interference to cancel and the detection performance is improved distinctly on the basis of increasing system time complexity a little.Theory proving, the complexity of the modified Gram-Schmidt method to decompose the channel matrix is high. The complexity of Householder transformation is as 2/3 times as it compared to the modified Gram-Schmidt method. An improved parallel detection algorithm based on Householder transform (HIP) is proposed. The HIP algorithm transforms the channel matrix column orthogonally based on Householder transform to avoid the operation of upper triangular matrix and sorted the channel matrix only once. In the processing of judging signals, it proposes a parallel processing algorithm of judged signals' feedback and received signals' interference cancellation and the complexity is reduced distinctly.We present a new receiver structure able to deliver high data rates in a multi-input-multi-output (MIMO) frequency selective wireless environment. The ordered successive interference cancellation MIMO decision feedback equalization based on recursive least square algorithm (RLS-OSIC-DFE) is obtained by canceling decided symbols from the received symbols successively with the decision feed-forward equalizer solution as a well known expression encountered in fast recursive least squares adaptive algorithms, and the decision feedback equalizer as a convolution of the decision feed-forward equalizer with the channel. The RLS-OSIC-DFE algorithm avoids the the interference of the decided symbols and improves the detection performance and the detection performance of proposed algorithm is improved dramatically.On the basis of the RLS-OSIC-DFE, We present a parallel interference cancellation MIMO decision feedback equalization based on recursive least square algorithm (RLS-PIC-DFE) by using the parallel processing. It is obtained by canceling decided symbols from the received symbols parallelly with the decision feed-forward equalizer solution as a well known expression encountered in fast recursive least squares adaptive algorithms, and the decision feedback equalizer as a convolution of the decision feed-forward equalizer with the channel. The RLS-PIC-DFE algorithm avoided sorting the channel matrix and reduced the complexity. While with low SNR, it avoided the interference caused by the signal of high power. It is suitable for the bad channel condition.The error curves of LSCMA have no symmetry and it is the main cause of slow convergence and large mean square error. Then we proposed the LSCMA and defined the error curves as a novel lognormal error function and added a decision condition. It is obtained by canceling decided symbols from the received symbols successively with the decision feed-forward equalizer solution as a well known expression encountered in improved log-normal error function based on CMA (ILNCMA-OSIC-DFE) adaptive algorithms. The decision feedback equalizer replaces a convolution of the decision feed-forward equalizer with the channel. The ILNCMA-OSIC-DFE algorithm avoids the interference of the decided symbols and improves the detection performance. Because the LSCMA used the constant modulus property, it is suitable for fast fading channel.