Bandwidth-efficient Coded Modulation Scheme Research Articles

Proposal for Beyond 100-Gb/s Optical Transmission Based on Bit-Interleaved LDPC-Coded Modulation

An iterative bandwidth-efficient coded modulation scheme based on bit-interleaving low-density parity-check (LDPC) codes, and M-ary differential phase-shift keying is proposed. A bit-interleaved LDPC-coded scheme, carrying 3 bits/symbol, provides the coding gain of 8.3 dB at a bit-error rate (BER) of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-7</sup> . The expected coding gain at BER of 10 <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-12</sup> is 12.8 dB. Possible applications include 100G Ethernet, and high-speed (>100 Gb/s) long-haul transmission

Low-complexity concatenated two-state TCM schemes with near-capacity performance

This paper presents a family of concatenated two-state trellis-coded modulation (CT-TCM) schemes. Compared with the existing turbo-type bandwidth-efficient coded modulation schemes, the proposed codes have significantly reduced complexity without sacrificing performance. A joint design strategy for all component codes is established. This leads to so-called asymmetrical and time-varying trellis structures, which possess good Hamming and Euclidean distance distributions. The performance of the proposed codes is demonstrated by simulation results.

Capacity-approaching bandwidth-efficient coded modulation schemes based on low-density parity-check codes

We design multilevel coding (MLC) and bit-interleaved coded modulation (BICM) schemes based on low-density parity-check (LDPC) codes. The analysis and optimization of the LDPC component codes for the MLC and BICM schemes are complicated because, in general, the equivalent binary-input component channels are not necessarily symmetric. To overcome this obstacle, we deploy two different approaches: one based on independent and identically distributed (i.i.d.) channel adapters and the other based on coset codes. By incorporating i.i.d. channel adapters, we can force the symmetry of each binary-input component channel. By considering coset codes, we extend the concentration theorem based on previous work by Richardson et al. ( see ibid., vol.47, p.599-618, Feb. 2001) and Kavc/spl caron/ic/spl acute/ et al.(see ibid., vol.49, p.1636-52, July 2003) We also discuss the relation between the systems based on the two approaches and show that they indeed have the same expected decoder behavior. Next, we jointly optimize the code rates and degree distribution pairs of the LDPC component codes for the MLC scheme. The optimized irregular LDPC codes at each level of MLC with multistage decoding (MSD) are able to perform well at signal-to-noise ratios (SNR) very close to the capacity of the additive white Gaussian noise (AWGN) channel. We also show that the optimized BICM scheme can approach the parallel independent decoding (PID) capacity as closely as does the MLC/PID scheme. Simulations with very large codeword length verify the accuracy of the analytical results. Finally, we compare the simulated performance of these coded modulation schemes at finite codeword lengths, and consider the results from the perspective of a random coding exponent analysis.

Visual communication via trellis coding and transmission energy allocation

An unequal error protection approach for the reliable communication of visual information over additive white Gaussian noise channels is proposed and studied. This method relies on a bandwidth-efficient coded modulation scheme that employs selective channel coding and transmission energy allocation in conjunction with sequence maximum a posteriori soft-decision detection. Experimental results indicate that this scheme exhibits graceful performance degradation as the channel conditions deteriorate and provides substantial objective and subjective improvements over uncoded and equal-error protection systems. Coding gains of up to 4 dB in E/sub b//N/sub o/ are achieved.

Reduced complexity sequence detection for nonminimum phase intersymbol interference channels

Controlled intersymbol interference may be used to design bandwidth efficient coded modulation schemes. The performance of the optimum receiver depends only on the free distance of the code and is independent of its phase. Large reductions in receiver complexity are obtained by using reduced search detection techniques like the M-algorithm (MA). However, we show that MA detector performance depends critically on phase, and is characterized by the partial energy of the encoder or channel. The minimum phase encoder needs by far the least detector searching. We propose modifications to the receiver, so that the reduced search can operate on all nonminimum phase channels at this same low complexity.