Performance Of Ldpc Coded Mimo Systems Analysis And Design Optimization

High-throughput reliable communications on bandwidth-limited and power-limited wireless channels has always been the focus in the communications research community. Since the 1990s, Shannon capacity approaching error correcting codes, such as turbo codes and LDPC codes are discovered. Not only do they become milestones in the coding theory, they also help establish standards in 3G, B3G, and 4G systems. MIMO techniques provide diversity gain and spatial multiplexing gain for communications systems, and thus save bandwidth, and combat fading in wireless communications channels. How to combine LDPC and MIMO together, and to design/optimize LDPC ensembles for MIMO systems are two important issues.Factor graphs, sum-product algorithms, and EXIT charts are significant tools to understand and design iterative decoding systems. We analyze, design and optimize an 2×2 MIMO system on flat Rayleigh fading channels via these tools.The thesis is organized as follows:(1) Present the principles of MIMO systems, derive the capacity of MIMO channels via channel factorization and mutual information maximization. Present the mainstream space-time coding systems, such as Space-Time Trellis Codes (STTC), Space-Time Block Codes (STBC), and Bell labs LAyered Space-Time (BLAST) systems. Summarize the current research and future directions of MIMO research.(2) Present the construction and Tanner graph presentation of LDPC codes, derive elaborately the message-passing decoding algorithms, discusses the density evolution, design and simulate regular and irregular LDPC codes.(3) Review the current research of LDPC-coded MIMO system and its competitors. Summarize the open questions. Propose the serial concatenation version of LDPC-coded MIMO systems. Discuss in-depthly via theory and simulations.(4) Present factor graphs and sum product algorithms, understand graph-based codes and iterative decoding algorithms thoroughly. Based on iterative decoding principle, propose dual iterative MIMO detector. Design sum product algorithm for message passing between MIMO detector and LDPC variable node decoder. Employ iterative message passing between decoders and detector to approximate optimum decoder/detector.(5) Introduce EXIT charts, discuss the LDPC ensemble design methods via EXIT charts in BEC and AWGN channels. Design maximum code rate LDPC ensembles in 2×2 MIMO systems via linear programming and curve fitting.(6) In view of tradeoff between decoding complexity and decoding accuracy, design suboptimum MIMO interference canceling detector, compare it with dual iterative MIMO detector.