Dynamic iteration stopping algorithm for non-binary LDPC-coded high-order PRCPM in the Rayleigh fading channel

Rui Xue,Yanbo Sun,Qiang Wei

doi:10.1186/s13638-016-0562-z

Abstract

This paper mainly studies the association between non-binary low-density parity-check codes and high-order partial response continuous phase modulation, which prevents information loss in the mutual conversion of bit and symbol probabilities. Although the iterative detection and decoding technique applied in this system can obtain good performance/complexity tradeoff, the iterative process still encounters the problems of positive feedback and relatively large decoding delay, similar to other iterative coded modulation systems. The inhibitory effects of different extrinsic information exchange methods on positive feedback under different signal-to-noise ratio (SNR) conditions are investigated in this work to address this issue. Two dynamic iterative stopping algorithms, namely, cross entropy and hard decision aided combined with weighted extrinsic information exchange for cases with medium and high SNRs, are then proposed. Extrinsic information exchange between the demodulator and the decoder is conducted in the two algorithms through weighted processing. Iterative detection is subsequently performed based on two stopping criteria of dynamic iterative decoding. Theoretic analysis and simulation results for the Rayleigh fading channel show that the combination of weighted extrinsic information exchange and the two dynamic iterative stopping algorithms effectively resists positive feedback and improves the convergence of iterative detection and bit error rate performance. Such a combination also reduces the average iteration number to improve the real-time performance of iterative detection and decoding.

Highlights

The two important design criteria in a wireless communication system include power and bandwidth efficiency
Among the most attractive options emerged till a prominent role is played by convolutional codes (CC), short binary low-density parity-check (LDPC) codes, parallel turbo codes (PTCs) and extended Bose-Chaudhuri-Hocquenghem code with soft-decision decoding [9]
7 Conclusions To avoid information loss in the mutual conversion of bit and symbol probabilities when binary LDPC codes are combined with high-order Continuous phase modulation (CPM), the combination of non-binary low-density parity-check (NB-LDPC) codes and high-order partial response continuous phase modulation (PRCPM) with the same number of levels is considered a possible candidate for the uplink of satellite communications

Summary

Introduction

The two important design criteria in a wireless communication system include power and bandwidth efficiency. Continuous phase modulation (CPM) is a general class of constant envelope modulation that achieves high spectral efficiency with low spectral sidelobes by requiring a smooth phase transition between adjacent symbols [1] These characteristics make CPM an ideal choice, with applications in different stringent communication systems employing nonlinear power amplifiers, such as satellite communication [2, 3], satellite mesh networks [4, 5] and satellite navigation [6, 7]. The scheme with iterative detection and decoding technique exhibits positive feedback and relatively large decoding delay during iterative detection, similar to other iterative coded modulation systems To address these problems, two dynamic iterative stopping algorithms, namely, cross entropy (CE) and hard decision aided (HDA) based on weighted extrinsic information exchange, are proposed in this paper for cases with medium and high SNRs. The rest of the paper is organized as follows.

System description

Modified MAP algorithm for CPM in the Rayleigh fading channel

Analysis of the iterative detection process

Weighted exchange method of extrinsic information

Conclusions