采用預(yù)判決信息的LDPC碼編碼調(diào)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: 低密度奇偶校驗(yàn)(LDPC)碼是Turbo碼以外另一種性能接近香農(nóng)限的好碼.本文將LDPC碼與比特交織編碼調(diào)制(BICM)相結(jié)合,首先給出了在不使用傳統(tǒng)解調(diào)器與譯碼器之間迭代的情況下8PSK調(diào)制方案在AWGN信道和Rayleigh衰落信道中的性能(簡稱為無迭代方案).然后提出了一種新的接收端解決方案:首先對接收符號進(jìn)行預(yù)判決,判決信息被用來調(diào)整解調(diào)器,從而在一定程度上彌補(bǔ)了不使用解調(diào)器與譯碼器之間迭代所造成的性能損失,并且相對于無迭代方案接收端復(fù)雜度幾乎沒有變化,但性能卻有所提高.這說明原有比特度量產(chǎn)生方法并不是最佳的,該文使用預(yù)判決信息的方案給出了一個改善的思路.通過仿真結(jié)果可以得到結(jié)論: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復(fù)雜度的情況下提高性能.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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