Energy-Efficient Optical-Aided VLC-MIMO System With Centralised Optimal PI Strategy

As a pivotal technology for 6G and beyond, visible light communication (VLC) is capable of supporting high-speed indoor access networks, particularly when combined with spatial modulation (SM)-based multiple-input-multiple-output (MIMO) techniques. However, in order to facilitate massive-MIMO deployment, the SM-based MIMO system requires exceptionally power-consuming MIMO digital signal processing (DSP). In this paper, we propose to optically process SM signals through the implementation of energy-efficient radio-over-fiber (RoF) concept. This method allows for the optical control of an arbitrary number of SM-based LEDs without necessitating ultra-fast SM switches or extensive network updates. Then, we propose an all-optical centralised power-imbalance (PI) strategy in order to reduce the high correlation of VLC channel in an energy-efficient manner. As a result, our design achieves cost-reduction by eliminating SM DSP and circumventing digital-to-analog converter (DAC) and analog-to-digital converter (ADC) stages, while maintaining an acceptable bit error rate (BER) performance exploiting an energy-efficient all-optical PI scheme, with a maximum degradation of around 1.5dB compared to those without RoF.

I. Introduction

Benifiting from large bandwidth, electromagnetic interference free and easy-to-install, visible light communications (VLC) have been recognized as a strong candidate for supporting high-speed next-generation indoor access network [1], [2], [3], [4]. However, due to the bandwidth limitation of laser emitting diode (LED), improving the capacity of VLC remains a critical challenge, where the multiple-input-multiple-output (MIMO) is capable of mitigating [5], [6].