Diversity receiver design and channel statistic estimation in fading channels
Jin, Jinghua (2006) Diversity receiver design and channel statistic estimation in fading channels. PhD thesis, Iowa State University.
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Wireless communication has experienced a tremendous evolution over the past few decades. In wireless communication systems, the channels exhibit phenomena such as fading, multipath, and time-variations. These phenomena often lead to performance degradations or data rate loss and hence present many challenges to the analysis and design of wireless communication systems compared with wired ones. To ensure reliable high-speed communications over insufficient channel bandwidth is one of the major challenges in harsh wireless environments. The main goal of this thesis is to provide an in-depth study of two important techniques that are effective in improving the performance, data rate, or bandwidth-efficiency in wireless communication systems. The two techniques are, first, diversity combining equipped with quadrature amplitude modulation (QAM), and second, the estimation of fading channel statistical properties. To effectively combat the adverse effect of fading and to improve the error rate performance, one of the major approaches is to employ diversity combining techniques. In the first part of this thesis, we focus on the equal gain combining (EGC) and hybrid-selection equal gain combining (HS/EGC) for bandwidth-efficient wireless systems (i.e. QAM systems). For EGC QAM systems, we propose the receiver structure and the corresponding decision variables, and then study the effects of imperfect channel estimation (ICE) and quantify the loss of the signal-to-noise ratio (SNR) gain caused by ICE. For HS/EGC QAM system, we develop a general approach to derive unified error rate and outage probability formulas over various types of fading channels based on the proposed HS/EGC receiver. The main contribution of this work lies in that it provides effective hybrid diversity schemes and new analytical approaches to enable thorough analysis and effective design of bandwidth efficient wireless communication systems which suffer from ICE and operate in realistic multipath channels. Channel side information is of fundamental significance in wireless communication systems, proven to be critical in determining the systems design, achievable data rate, and achievable performance. A relatively less costly form of side information is the fading channel statistical properties. It is widely assumed that these statistics are available for analysis/design, but little is known about how to obtain them effectively. In the second part of this thesis, we study the estimation of the fading channel statistics. We propose several iterative algorithms to estimate the first- and second-order statistics of general fading or composite fading-shadowing channels and derive the Cramer-Rao bounds (CRBs) for all the cases. We demonstrate that these iterative methods are efficient in the sense that they achieve their corresponding CRBs. The main contribution of this work is that it bridges the gap between the broad utilization of fading channel statistical properties and the lack of systematic study that makes such statistical properties available.
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