| Summary: | 博士 === 國立交通大學 === 電子研究所 === 101 === This dissertation conducts a thorough investigation on various technology aspects of low-density parity check (LDPC) codes, and then proposes corresponding efficient techniques for effective decoding and realization of LDPC codes. The investigated issues include decoding algorithms, hardware architectures of LDPC codes, and application of LDPC codes to cooperative coding and decoding. Furthermore, new coding schemes based on the joint concepts of LDPC and Turbo codes have been proposed in the end of the dissertation.
Bit-flipping (BF) LDPC decoding algorithms have lower complexity compared with message passing (MP) algorithms, but have the drawbacks of lower decoding performances and higher iteration counts. In order to significantly enhance BF algorithms, a performance-boosting algorithm, called low-correlation culprit-bit-test multi-bit flipping (LCCBT-MBF) algorithm, has been proposed and integrated with BF algorithms. Besides, this work proposes a genet¬ics-aided message passing (GA-MP) algorithm by applying a new genetic algorithm to further improve the decoding performance of MP algorithm.
Long delay time of the check node units are usually the major bottleneck in LDPC decoders for high-speed applications. Hence, this dissertation proposes several improved comparison algorithms for self-message-excluded CNU (SME-CNU) and two-minimum CNU (TM-CNU) architectures. Next, in order to eliminate the idling time and hardware complexity in conventional partially-parallel decoders, this work proposes a decoder architecture which can handle two different codewords simultaneously with 100% hardware utilization. Since LDPC decoding operations can be conducted very effectively with layered decoding schemes (LDS), a decoder architecture with an optimized execution reordering scheme for LDS is also proposed. In the final part of decoder designs, we implement the corresponding LDPC decoders for all the proposed decoding algorithms.
Next, we propose an efficient coding scheme, called Turbo-LDPC code, which combines the merits of both the turbo code and LDPC code. The decoding performance is significantly improved by utilizing turbo decoding process, while the major part of the decoder is basically the same as a conventional LDPC decoder. Compared to combined block turbo code and BCH codes, the proposed Turbo-LDPC code also has much better decoding performance as well as lower computational complexity. Due to the significant improvements of the proposed Turbo-LDPC codes in decoding performance, the 2D coding scheme is extended to a new 3D codes, named Triple-LDPC codes. Finally, both proposed coding schemes are applied to cooperative coding in relay networks. Some cooperative coding and decoding schemes are devised based on these two codes. From analysis and simulations, the new cooperative coding/decoding techniques can significantly reduce the hardware complexity in relay stations, while obtain better error-correction capabilities.
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