采用预判决信息的LDPC码编码调制方案性能研究
Research on Performance of LDPC Coded BICM Schemes Using Pre-decision Message
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摘要: 低密度奇偶校验(LDPC)码是Turbo码以外另一种性能接近香农限的好码.本文将LDPC码与比特交织编码调制(BICM)相结合,首先给出了在不使用传统解调器与译码器之间迭代的情况下8PSK调制方案在AWGN信道和Rayleigh衰落信道中的性能(简称为无迭代方案).然后提出了一种新的接收端解决方案:首先对接收符号进行预判决,判决信息被用来调整解调器,从而在一定程度上弥补了不使用解调器与译码器之间迭代所造成的性能损失,并且相对于无迭代方案接收端复杂度几乎没有变化,但性能却有所提高.这说明原有比特度量产生方法并不是最佳的,该文使用预判决信息的方案给出了一个改善的思路.通过仿真结果可以得到结论:使用本文所提出的方案在AWGN信道和Rayleigh衰落信道中都可以在不增加复杂度的情况下提高性能.Abstract: Low-Density Parity Check(LDPC) coded Bit-Interleaved Coded Modulation (BICM) schemes are analyzed in this paper. The schemes using decoding method without iteration between demodulator and decoder are first simulated. Then a novel method using pre-hard-decision message is proposed. And the performance over Additive White Gaussian Noise (AWGN) and Rayieigh fading channels is analyzed. The decoding complexity is also considered. The new method proves that the conventional bit-metrics generation method is not optimal. Through the simulation results there is conclusion that the proposed schemes have better performance than the scheme without pre-decision message both over AWGN and Rayieigh fading channels with nearly same complexity.
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Gallager R G. Low-Density Parity-Check Codes, Cambridge, MA:MIT Press, 1963.[2]MacKay D J C. Good error-correcting codes based on very sparse matrices[J].IEEE Trans. on IT.1999, 45(3):399-[3]Zehavi E. 8-PSK trellis codes for a Rayleigh fading channel[J].IEEE Trans. on Communications.1992, 40(5):873-[4]Li Xiaodong, Ritcey J A. Bit-interleaved coded modulation with iterative decoding[J].IEEE Communications Letters.1997, 1(6):169-[5]Li Xiaodong, Ritcey J A. Bit-interleaved coded modulation with iteratively decoding using soft feedback[J].Electronics Letters.1998,34(10):942- -
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