Research On Precoding Of Multiple Antennas Systems

With the rise of the Internet and the increase of the mobile multimedia business types, the demand to the availability and reliability of wireless communication system put forward more and more. But the channel environment of wireless communication system is bad, and less restricted spectrum resources, so improving the validity and reliability of wireless communication system need revolutionary technology in the physical. Multiple antennas is the landmark technology from the1990s wireless communication, since it don’t take up other spectrum resource conditions, and then can increase the system capacity manifold. Multiple antennas have been the necessary technology for the future wireless communications network. In multiple antennas systems, the precoding technology can also increase their multiplex gain and diversity gain, improve the system efficiency and reliability, become a hotspot in recent research.Under the support of National Science and Technology Major Project of China (2009ZX03002-009-01) and National Science Foundation of China (60672132、60872149), precoding related technologies in Multiple Input Multiple Output(MIMO) broadcast system, virtual multiple antenna cooperation system, multiple antennas and multiple base stations system are deeply investigated in the dissertation.The main contributions of the dissertation are as follows:(1) In MIMO broadcast system nonlinear precoding study, through to the existing ZF-TH precoding problems that can’t support multi-stream data transmission, this paper and send and receive the combined processing, put forward a kind of fit for both the user scene low complexity, Zero Forcing Tomlinson-Harashima (ZF-TH) precoding method, this method in traditional ZF-TH basis, the nature of the generalized characteristic vectors, and further the sending and receiving ends joint eliminate interference between the data flow, so as to achieve system of the full reuse the gain. This method in and ZF-TH precoding complexity rather conditions and improves the system capacity, close to the system capacity.(2) In Multiple-In Multiple-Out (MIMO) Broadcast systems with limited feedback, when receivers are equipped with multiple antennas, the so-called quantization error of channel direction matrix was unavoidably introduced. This quantization error will result in the reduction of system capacity since it was referenced in the precoding design. In this paper, we proposed a robust precoding method based on MMSE, which considers the statistical characteristics of the quantization error for channel direction matrix. Simulation results show that the proposed method effectively enhanced system capacity, reduced bit error rate, as well as mitigated the Plateau Effect.(3) In the virtual multi-antenna cooperation multiuser broadcast systems, when the receivers are equipped with multiple antennas, we analyzed the statistics of quantization error about backward channel and proposed two precoding schemes which based on block diagonalization (BD) criterion and minimum mean square error (MMSE) criterion respectively. The BER performance of MMSE scheme is much better by comparing with each other. Based on that, a forward feedback scheme is added. By analyzing the impacts of two feedback channels to system capacity, we proposed an optimal bit allocation scheme under the limited total feedback bits. Simulation results demonstrate this scheme efficiently improve the capacity of limited feedback systems, and enhance the system multiplexing gain.(4) In the virtual multi-antenna cooperation two-way relaying systems, each node of which is equipped with multiple antennas, we analyzed the probability distribution function of Signal-to-Noise Ratio (SNR) in each node under Nakagami-m channel. Based on that, We induce the outrage probability and BER closed expressions of two source nodes. Simulation proves the correctness of analysis, and provides theoretical support to further optimize multi-antenna two-way relaying system.(5) Aiming at the joint zero-forcing precoding method in multi-antenna multi-basestation systems, we propose double codebooks feedback scheme in Wyner model with capacity loss due to limited feedback. We prove that the Channel Direction Information (CDI) scheme can’t achieve full multiplexing gain, while can achieve it by additionally feedback information on the phase between channel direction information and perfect channel information. Though the analysis of probability density function of phase, we design a non-uniform quantification codebook. Simulation results demonstrate the proposed method efficiently improves system’s capacity with same feedback bits.