Wireless Collaborative Communication Systems In The Detection Technology

Multi-Input Multi-Output (MIMO) technology could achieve high diversity gain and spectral efficiency without considering additional bandwith and transmission power. However, MIMO brings considerable advantage factors as well as high detection complexity at the receiver. How to find low-complexity but high-performance detection algorithms has been a hot topic in the wireless communication researching area.Because of the limits of the power, size, and hardware complexity, it is difficult to collocate many antennas at the mobile terminals. Cooperative communications was proposed, which enables single-antena terminals in multiple users or relays environment to share their antennas and generates a virtual MIMO system. At the same time, it can extend the cell coverage and improve the cell edge performance.Independent Component Analysis (ICA) is a computational method for separating a multivariate signal. Its application in blind signal separation of wireless communications has begun to be attached importance.Single-carrier Frequency-Division Multiple Access (SC-FDMA) is a new multiple access scheme that has been adopted in Long Term Evolution (LTE) uplink. It is preferred for uplink communications because of its low peak-to-average power ratio (PAPR), and with the same merits as multi-carrier communication systems, such as simple structure and flexible resource scheduling. How to design reasonable muti-user cooperative transmission schemes is worthy of researching.In this dissertation, considering the detection technology in wireless communication systems, we research on the low-complexity detection algorithms in MIMO systems, use ICA algorithms in cooperative communication systems for bind signal separation, and propose two cooperative transmission schemes with low-complexity equalization in SC-FDMA systems.This dissertation consists of five chapters. In chapter one, the background and current situation of the reasearching area are introduced. Moreover, the main works and contributes of this dissertation are summarized. In chapter two, three low-complexity detection algorithms for MIMO systems are studied, such as sphere decoding (SD), Chase detection, and QRD-M detection algorithms. Based on Vertical-Bell Laboratories-Layered-Space-Time (V-BLAST) systems, a simple method to measure the computational complexity of QRD-M detection algorithm is proposed. And then we discuss and compare the performance of these algorithms through system simulations.In chapter three, two kinds of cooperative transmission schemes with low-complexity equalization in SC-FDMA systems are proposed. First of all, the conception of cooperative communications and SC-FDMA are introduced. Secondly, a two-user cooperative transmission scheme in Single-carrier Frequency-domain Equalization (SC-FDE) systems is proposed. Thirdly, based on Localized Frequency Division Multiple Access (LFDMA) and Distributed Frequency Division Multiple Access (DFDMA) systems, we proposed a cooperative transmission schemes with low-complexity equalization, respectively. Finally, through system simulations, we analyze the characteristics and compare with the performance of these schemes.In chapter four, Using blind signal separation technology ICA in cooperative communication systems is studied. Firstly, we introduce three ICA algorithms: Joint Appmximate Diaginalization of Eigenmatrixes (JADE), Equivariant Adaptive Separation via Independence (EASI), Median-Equivariant Adaptive Separation via Independence (M-EASI), and Fast-ICA algorithms. Then, two kinds of distributed space time block code (D-STBC) systems are introduced. Finally, based on these schemes, These ICA algorithms are used in cooperative communication systems for blind signal separation.Finally, some conclusions of the dissertation are drawn, and the further research issues are pointed out.