Studies on Controlling the Message-Passing Decoding Algorithms and Constructing Error Correcting Codes Suitable for Such Algorithms

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Today's high-speed and ubiquitous network environments, error correcting and error controlling strategies are the important element of communications and storages. Turbo coding and LDPC coding are the most interested coding for practical use in recent development. Already there are practical examples such as mobile phone system, draft for wireless LAN system standards for next generation and so on. Those code have inferiority in following points, (1) The decoding algorithms are sub optimal, and repetitions are required to get better results. (2) Code is asymptotically good, but there are few idea for finding good code for limited code length.In this study, we propose several ways of controlling the feedback by ordering for message passing decoding such as sum-product decoding and Turbo decoding (1) sum-product decoding with control for burst-error channel, (2)Hard-in Soft-out decoding, and (3) evaluation look up table algorithm for ML and MAP decodingWe also construct new LDPC and Turbo code base codes, which are (4) new construction method of unequal LDPC code, (5) constructing LDPC code having random like check matrix from algebraic LDPC code, (6)asymmetric Turbo-Hadamard code(ATHC), and (7) concatenate coding scheme using ATHC and LDPC codes. Finally we study application of our proposed coding and decoding scheme to digital watermarking system.