| Summary: | 碩士 === 國立交通大學 === 電信工程系所 === 94 === In this thesis, we study signal detection and decoding of low-density parity-check (LDPC) codes for multi-input-multi-output (MIMO) orthogonal-frequency- division-multiplexing (OFDM) systems. Three types of LDPC codes decoders are investigated, the Normalized belief-propagation (BP) based algorithm, the Normalized a-posteriori probability (APP) based algorithm, and the Layered normalized BP based algorithms. These decoding algorithms are much simpler to implement than the standard LDPC codes decoding algorithm, namely the sum-product algorithm, and can achieve good tradeoff between decoding complexity and performance. For MIMO signal detection, we consider the minimum-mean-squared error (MMSE) and a maximum a-posteriori probability (MAP) detector. The MMSE detector is combined with a soft-bit demapper to obtain soft outputs, while the MAP detector is designed to have soft outputs directly. To redue the high computational inherent in the MAP detector, we apply an efficiency algorithm called the list sphere decoding. Simulations with IEEE 802.11n and IEEE 802.16e systems show that the LDPC codes decoder can effectively improve the system performance, particularly when it combined with the MAP detector.
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