Entropy Loading Design for the MIMO-OFDM Visible Light Communication System Using the OCT Precoding Technique

Xinyue Guo,Haimeng Zhao,Wei Wang

doi:10.1155/2020/3403480

Abstract

In this paper, an orthogonal circulant matrix transform (OCT) precoding technique is proposed to combine with the entropy loading in the multiple-input multiple-output and orthogonal frequency division multiplexing (MIMO-OFDM) visible light communication (VLC) system where the space-time coding (STBC) is chosen for its robustness to the channel correlation. Benefitting from the OCT precoding technique, the uniform signal-to-noise ratio (SNR) among all the subchannels can be achieved. As a result, only one SNR value is required to be fed back, and the same distribution matcher is employed during probabilistic shaping (PS), which means much lower feedback overhead and system complexity than the conventional entropy loading scheme. Experimental results show that the OCT precoding does not cause the system performance loss where the achievable information rate (AIR) of the proposed system is comparable with the conventional system without precoding. With an available bandwidth of ∼25 MHz, the proposed scheme can realize the AIR of 50.75 Mb/s at the expense of 0.45% average forward error correction (FEC) overhead (OH).

Highlights

The emergence of “smart home” and the rapid spread of intelligent devices have made a great challenge to the conventional technology of the network. e world is experiencing a profound revolution of access technology called “Anywhere, Anytime” [1]
Different distribution matchers are required to generate signal sources with different probabilistic distribution for each subchannel when employing probabilistic shaping (PS). To deal with this problem, a precoding scheme based on orthogonal circulant matrix transform (OCT) [13, 14] is proposed to be combined with the entropy loading in the multiple-input multiple-output (MIMO)-orthogonal frequency division multiplexing (OFDM) visible light communication (VLC) systems in this paper. anks to the equalization effect of OCT, signal-to-noise ratio (SNR) are almost the same on all the subchannels, which means that only one SNR value is needed to be fed back
OCT precoding was first proposed [13, 14] where preequalization is realized without feeding back channel state information. erefore, we introduce OCT precoding in the entropy loading scheme to equalize the SNRs uniformly over all subchannels

Summary

Introduction

The emergence of “smart home” and the rapid spread of intelligent devices have made a great challenge to the conventional technology of the network. e world is experiencing a profound revolution of access technology called “Anywhere, Anytime” [1]. To improve the data rate of the VLC system, numerous techniques have been proposed, among which orthogonal frequency division multiplexing (OFDM) [5] and multiple-input multiple-output (MIMO) [6] are considered especially effective to increase the spectral efficiency for VLC systems. Adaptive modulation implemented by bit allocation has been proposed to improve the data rate close to the Shannon capacity in MIMO-OFDM VLC systems [9]. To deal with this problem, a precoding scheme based on orthogonal circulant matrix transform (OCT) [13, 14] is proposed to be combined with the entropy loading in the MIMO-OFDM VLC systems in this paper. With an available bandwidth of ∼25 MHz, the proposed scheme can realize the AIR of 50.75 Mb/s at the expense of 0.45% average forward error correction (FEC) overhead (OH)

Operation Principle

System Configuration and Results

Conclusion