Keqian Yan

EXIT-Aided Bit Mapping Design for LDPC Coded Modulation with APSK Constellations

In this paper, the bit mapping technique is applied to the low-density parity-check (LDPC) coded modulation system with Gray-APSK constellations for the first time. A multi-grid searching algorithm (MGSA) based on extrinsic information transfer (EXIT) chart analysis is first proposed to optimize the bit mapping distribution, after which a low-complexity bit mapper consisting of a structural bit interleaver and a demultiplexer (DEMUX) is devised. Compared to the LDPC coded QAM system specified in DVB-T2, the proposed APSK system with the optimized DEMUX can achieve up to 0.83dB gain under additive white Gaussian noise (AWGN) channel.

Non-Equiprobable APSK Constellation Labeling Design for BICM Systems

The previously proposed amplitude phase shift keying (APSK) with Gray labeling achieves a considerable shaping gain in comparison with conventional square quadrature amplitude modulation. In this letter, by reducing the number of points on the inner rings of Gray-APSK and introducing a non-equiprobable (NE) bit-to-symbol labeling, a novel NE-APSK constellation labeling is proposed. NE-APSK provides additional 0.1 dB shaping gain over Gray-APSK without any complexity increase, as illustrated by the mutual information analysis and verified by the bit error rate simulation.

Improved design of bit mapping based on EXIT-chart analysis for DVB-T2 system

In this paper, we focus on the design of bit mapping scheme to improve the error-control performance for the second generation digital video broadcasting-terrestrial (DVB-T2) standard. Generally in the case of low-density parity-check (LDPC)-coded modulation system, the nonuniform bit reliabilities inherent to the high-order modulation and irregular LDPC code imply the mismatch between the decoder and the demodulator. Hence, the bit mapping is plugged between the two modules to match the unequal error protections (UEPs) of different coded bits to different modulation levels. This scheme gives a remarkable performance improvement with no added complexity in the bit-interleaved coded modulation (BICM) system. By performing the curve-fitting on the extrinsic information transfer (EXIT) chart, we propose a DEMUX design methodology to improve the bit mapping scheme. Design examples are given for the DVB-T2 system under the AWGN channel as well as the Rayleigh channel. Simulation results indicate that the proposed DEMUX schemes can even surpass the performance of the DEMUX operation specified in the DVB-T2 standard.

Reception Quality Prediction in a Single Frequency Network for the DTMB Standard

Single frequency network (SFN) is an attractive scheme for the digital television terrestrial broadcasting (DTTB) coverage with efficient utilization of the spectral resources. In this paper, a method featuring low complexity and low workload is proposed to estimate the reception quality under the SFN environment with the maximum delay spread of the artificial multipath no longer than the guard interval. Based on the analysis of error probability and channel capacity, this method supports an unambiguous prediction of the signal-to-noise ratio (SNR) threshold according to the parameters of received signals, which is thus meaningful for system evaluation. We applied this method to the digital television/terrestrial multimedia broadcasting (DTMB) systems, and carried out the laboratory measurements for performance verification. The predicted results show a satisfactory match with the measured results, validating the accuracy and effectiveness of the proposed method.

Genetic algorithm aided gray-APSK constellation optimization

The amplitude phase shift keying (APSK) constellation with Gray labeling (Gray-APSK) is able to achieve considerable shaping gains in comparison with the quadrature amplitude modulation (QAM) counterpart under both iterative and non-iterative scenarios. Nevertheless, the Gray-APSK constellation with the fixed radius cannot provide the optimal performance for every code rate of practical usage. In this paper, we propose a method based on the genetic algorithm to optimize the parameters of Gray-APSK constellations by maximizing the mutual information for the targeted code rate. Certain performance gains can be achieved via optimizing the radius of the Gray-APSK, as verified by both the average mutual information (AMI) analysis and the error performance evaluation.

Performance improvement of G.hn system based on bit mapping technique

A new specification for power line communication (PLC), named G.hn, has been developed recently for the existing-wire home networking. G.hn system specifies a coded modulation scheme based on quasi-cyclic low-density parity-check (QC-LDPC) codes and quadrature amplitude modulations (QAMs). In this paper, we present a bit mapping strategy to exploit the unequal error protection (UEP) property inherent in the irregular LDPC codes and high-order constellations, which can effectively improve the reliability of the whole coded modulation system with no penalty. The method to design the bit mapping scheme is also investigated via the analysis of extrinsic information transfer (EXIT) charts. Simulation results reveal that the appropriate bit mapping scheme can achieve considerable gains in the G.hn system.

A framework of APSK constellation labeling design for satellite transmission

In this paper, the framework of amplitude phase shift keying (APSK) constellation labeling design for satellite transmission is proposed. It consists of two steps, the constellation design and the joint phase-labeling optimization. Both iterative and non-iterative demapping scenarios are considered in the design framework. The proposed APSK constellation labeling exhibits a low peak-to-average power ratio and achieves a considerable performance gain compared with its counterpart approved by the consultative committee for space data systems, as verified by both the mutual information analysis and bit error rate simulation.

Coded modulation with APSK constellations for power line communication

This paper proposes a novel coded-modulation scheme using amplitude phase shift keying (APSK) constellations with Gray mapping for the broadband power line communication systems for the first time. In this scheme, three key techniques including the Gray-APSK constellation design, the bit mapping technique, and the method of simplified soft APSK demapper are jointly employed to enhance the error-control performance while ensuring low complexity. Simulation results over AWGN and power line channels show that the proposed scheme provides a remarkable receiving performance gain, compared to its counterpart specified in the G.hn standard.

Non-uniform APSK optimization for BICM systems

Traditional Amplitude Phase Shift Keying (APSK) consists of rings with points uniformly spaced. By giving up this uniform-spacing feature, we propose an APSK optimization method based on the uniform APSK with Gray labeling (Gray-APSK). The aim of the optimization is to maximize the Generalized Mutual Information (GMI) of Bit-Interleaved Coded Modulation (BICM) for the targeted code rate and channel. We show that our optimized non-uniform APSK could offer further performance gain compared with the conventional uniform Gray-APSK and considerably outperforms the traditional quadrature amplitude modulation at the targeted SNR and channel.

An EXIT-chart aided optimization of bit mapping for DVB-C2 system

Due to the unequal error protection (UEP) property of both the irregular low-density parity-check (LDPC) code and the higher-order modulation, bit mapping is proposed as a joint optimization of the LDPC coded-modulation scheme. In this paper, we discuss the bit mapping optimization performed by employing an additional DEMUX following the given bit interleaver, and then apply it to the second generation digital video broadcasting system for cable (DVB-C2). The extrinsic information transfer (EXIT) chart technique is adopted to analyze the influence of bit mapping on the iterative decoding process. Based on the EXIT-chart analysis, an optimization method is proposed to design the DEMUX for performance improvement. As an example, we re-design the DEMUX for the DVB-C2 system with reduced DEMUX width. The superior performance of the optimized DEMUX is verified by the bit error rate (BER) simulation.