Design of a Labeling Scheme for 32-QAM Delayed Bit-Interleaved Coded Modulation.

Zhe Zhang,Liang Zhou,Yue Zhao,Junyi Du

doi:10.3390/s20123528

Abstract

It is very challenging to design the capacity-approaching labeling schemes for large constellations, such as 32-QAM, in delayed bit-interleaved coded modulation (DBICM). In this paper, we investigate the labeling design for 32-QAM DBICM with various numbers of bits delayed by one time slot. In particular, we aim to obtain the labeling schemes with a high DBICM channel capacity by searching the possible labeling schemes. To reduce the search space of the candidate labeling schemes, we propose the criteria that are necessary for good labeling. Based on the proposed criteria, a three-step search algorithm is proposed to obtain the candidate labeling efficiently. Numerical results demonstrate that the DBICM with our proposed labeling scheme can approach the capacity of 32-QAM within 0.015 dB at an information rate greater than 2.5 bits/symbol.

Highlights

Bit-interleaved coded modulation (BICM) [1] has been widely used in practical systems for its simplicity
The delayed bit-interleaved coded modulation (DBICM) capacities of these labeling schemes are compared to the constellation capacity and that of the quasi-Gray labeling in [10]
We considered this SNR since the DBICM channel capacity was around 2.5, three bits/symbol or the code rate was around 0.5, 0.6 at this point, respectively, which is practical for high order coded modulation schemes

Summary

Introduction

Bit-interleaved coded modulation (BICM) [1] has been widely used in practical systems for its simplicity. It is a bandwidth efficient coded modulation scheme and has been well investigated in point-to-point communications [1,2,3,4,5,6,7]. In BICM, the dependence between transmitted bits is ignored by introducing the ideal bit-interleaver. This character is convenient for code design. Due to the loss of dependence between transmitted bits, the channel capacity of BICM is less than that of coded modulation (CM), which is the constellation capacity. For squared constellations that have Gray labeling schemes, the gap between BICM capacity and constellation capacity is negligible [1]. The other newer related works about the labeling focus on the BICM-iterative decoding (ID) [11,12,13,14] or the other constellation [15,16,17,18,19]

Objectives

Methods

Results

Conclusion