【作者】 王加庆；

【导师】 吴乐南；

【作者基本信息】 东南大学 ， 信号与信息处理， 2006， 博士

【摘要】 最近的研究表明低密度奇偶校验(LDPC)码能以较低的译码复杂度,取得逼近Shannon限的性能,引起了纠错编码领域极大的关注。本文针对无线信道的编码数据传输,研究了LDPC码在数字调幅广播(DAMB)和最小波形差键控(VWDK:Very-minimum Waveform Difference Keying)系统中的应用。DAMB带宽只有9/10 kHz且信道极恶劣,欲获得优良音质和高速传输,需要高效的信道编码调制方案。本文在深入研究DRM(Digital Radio Mondiale)标准中的编码调制方案的基础上,提出了基于非正则LDPC码的一系列编码调制技术。首先,深入研究了DRM标准的编码调制技术,提出3种基于软判决的译码方案;接着,针对DAMB系统提出了基于LDPC码的比特交织编码调制方案、多层编码方案和迭代解调译码方案;最后,设计了适合DAMB系统的非正则LDPC码。与国际标准相比,本文所提出的方案不仅性能优异而且具有更低的译码复杂度,同时经过精心设计的LDPC码性能优于采用Turbo码的方案。LDPC码极有可能成为下一代通信系统的首选,因此本文的研究可为我国的数字广播系统提供参考。VWDK用二进制码元直接控制两个差别很小的类正弦载波而实现调制,虽使超窄带传输成为可能,但接收端的相关检测却变得困难。因此,高效信道编码方案的引入,对于采用VWDK调制的通信系统至关重要。本文针对VWDK系统对非正则LDPC码的性能进行分析与仿真,推导了VWDK系统的信道容量,修正了置信传播译码算法,证明了在VWDK调制下信道输出信号仍满足对称性,给出了译码稳定性条件,最后利用外部信息图技巧设计了适合VWDK系统的非正则LDPC码。更多还原

【Abstract】 Recent advances in error correcting codes have shown that irregular low density parity-check (LDPC) codes attracted considerable attentions owing to their capacity- approaching performance and low complexity iterative decoding. To improve the efficiency of transmitting encoded data in wireless channel, in this dissertation, we propose LDPC codes for implementation of the Digital Amplitude Modulation Broadcasting (DAMB) and the Very-minimum Waveform Difference Keying (VWDK) systems.In DAMB systems, achieving good audio quality becomes a challenge due to its limited band-width of 9 or 10 KHz and the very bad fading channels. Therefore, DAMB needs highly efficient channel coding schemes. In this thesis, a series of coded modulation schemes based on irregular LDPC codes are employed, after exploration of international standard proposed by Digital Radio Mondiale (DRM). Firstly, three decoding strategies using soft decision are provided for Multilevel Coding (MLC) schemes based on Rate Compatible Punctured Convolutional (RCPC) codes. And then, Bit-Interleaved Coded Modulation, MLC and iterative demapping and decoding schemes based on irregular LDPC codes are investigated for DAMB systems. Finally, using Extrinsic Information Transfer (EXIT) chart technique, we optimize the irregular LDPC codes for DAMB systems and achieve satisfactory results. Simulation results show that our schemes are more efficient than the RCPC coded DRM system on various broadcast channels. The optimized irregular LDPC codes can outperform Turbo codes, especially in short wave channel.The pivotal thinking of VWDK is to make the difference of two modulation waves minimum, which makes coherent detection more difficult, then results in poor SNR performance. Therefore, powerful channel coding schemes are essential for VWDK modulation. The paper investigates the application of LDPC codes for VWDK modulation. We modify Belief Propagation (BP) decoding algorithm, and prove symmetry on AWGN更多还原