This paper investigates analysis and design of Low-Density Parity-Check （LDPC） coded Bit Interleaved Coded Modulation （BICM） over Additive White Gaussian Noise （AWGN） channel. It focuses on Gray-labeled 8-ary Ph...This paper investigates analysis and design of Low-Density Parity-Check （LDPC） coded Bit Interleaved Coded Modulation （BICM） over Additive White Gaussian Noise （AWGN） channel. It focuses on Gray-labeled 8-ary Phase-Shift-Keying （8PSK） modulation and employs a Maximum A Posteriori （MAP） symbol-to-bit metric calculator at the receiver. An equivalent model of a BICM communication channel with ideal interleaving is presented. The probability distribution function of log-likelihood ratio messages from the MAP receiver can be approximated by a mixture of symmetric Gaussian densities. As a result semi-Gaussian approximation can be used to analyze the decoder. Extrinsic information transfer charts are employed to describe the convergence behavior of LDPC decoder. The design of irregular LDPC codes reduces to a linear programming problem on two-dimensional variable edge-degree distribution. This method allows irregular code design in a wider range of rates without any limit on the maximum node degree and can be used to design irregular codes having rates varying from 0.5275 to 0.9099. The designed convergence thresholds are only a few tenths, even a few hundredths of a decibel from the capacity limits. It is shown by Monte Carlo simulations that, when the block length is 30,000, these codes operate about 0.62-0.75 dB from the capacity limit at a bit error rate of 10s.展开更多
We consider an iterative phase synchronization scheme based on maximum a posteriori probability algorithm.In classical approaches,the phase noise estimation model considers one sample per symbol at the channel and rec...We consider an iterative phase synchronization scheme based on maximum a posteriori probability algorithm.In classical approaches,the phase noise estimation model considers one sample per symbol at the channel and receiver.However,information theoretic studies suggested use of more than one sample per symbol at the channel and receiver for achieving higher performance.In this article,a soft-information aided iterative receiver is derived,which uses off-the-shelf blocks for detection and demodulation by keeping the complexity of the receiver acceptable.We consider here two samples per symbols at the channel and receiver in a pragmatic paradigm.It is shown that phase noise estimation can be significantly improved at the expense of modest processing overhead.Simulation results are presented for low-density parity check coded quadrature amplitude modulations.Our results show a significant performance improvement for strong phase noise values compared to classical receiver approaches.展开更多
A new log-likelihood ratio(LLR) message estimation method is proposed for polarization-division multiplexing eight quadrature amplitude modulation(PDM-8QAM) bit-interleaved coded modulation(BICM) optical communication...A new log-likelihood ratio(LLR) message estimation method is proposed for polarization-division multiplexing eight quadrature amplitude modulation(PDM-8QAM) bit-interleaved coded modulation(BICM) optical communication system.The formulation of the posterior probability is theoretically analyzed,and the way to reduce the pre-decoding bit error rate(BER) of the low density parity check(LDPC) decoder for PDM-8QAM constellations is presented.Simulation results show that it outperforms the traditional scheme,i.e.,the new post-decoding BER is decreased down to 50%of that of the traditional post-decoding algorithm.展开更多
文摘This paper investigates analysis and design of Low-Density Parity-Check （LDPC） coded Bit Interleaved Coded Modulation （BICM） over Additive White Gaussian Noise （AWGN） channel. It focuses on Gray-labeled 8-ary Phase-Shift-Keying （8PSK） modulation and employs a Maximum A Posteriori （MAP） symbol-to-bit metric calculator at the receiver. An equivalent model of a BICM communication channel with ideal interleaving is presented. The probability distribution function of log-likelihood ratio messages from the MAP receiver can be approximated by a mixture of symmetric Gaussian densities. As a result semi-Gaussian approximation can be used to analyze the decoder. Extrinsic information transfer charts are employed to describe the convergence behavior of LDPC decoder. The design of irregular LDPC codes reduces to a linear programming problem on two-dimensional variable edge-degree distribution. This method allows irregular code design in a wider range of rates without any limit on the maximum node degree and can be used to design irregular codes having rates varying from 0.5275 to 0.9099. The designed convergence thresholds are only a few tenths, even a few hundredths of a decibel from the capacity limits. It is shown by Monte Carlo simulations that, when the block length is 30,000, these codes operate about 0.62-0.75 dB from the capacity limit at a bit error rate of 10s.
文摘We consider an iterative phase synchronization scheme based on maximum a posteriori probability algorithm.In classical approaches,the phase noise estimation model considers one sample per symbol at the channel and receiver.However,information theoretic studies suggested use of more than one sample per symbol at the channel and receiver for achieving higher performance.In this article,a soft-information aided iterative receiver is derived,which uses off-the-shelf blocks for detection and demodulation by keeping the complexity of the receiver acceptable.We consider here two samples per symbols at the channel and receiver in a pragmatic paradigm.It is shown that phase noise estimation can be significantly improved at the expense of modest processing overhead.Simulation results are presented for low-density parity check coded quadrature amplitude modulations.Our results show a significant performance improvement for strong phase noise values compared to classical receiver approaches.
基金supported by the National Natural Science Foundation of China(No.61205065)the Fund of State Key Laboratory of Information Photonics and Optical Communicationsthe Fundamental Research Funds for the Central Universities in China(No.2014RC1201)
文摘A new log-likelihood ratio(LLR) message estimation method is proposed for polarization-division multiplexing eight quadrature amplitude modulation(PDM-8QAM) bit-interleaved coded modulation(BICM) optical communication system.The formulation of the posterior probability is theoretically analyzed,and the way to reduce the pre-decoding bit error rate(BER) of the low density parity check(LDPC) decoder for PDM-8QAM constellations is presented.Simulation results show that it outperforms the traditional scheme,i.e.,the new post-decoding BER is decreased down to 50%of that of the traditional post-decoding algorithm.
