On the Performance of Mixed RF-VLC Relaying Systems for HST Communication

The emerging fifth generation (5G) wireless communication systems are a promising solution to support the high data rate for high-speed trains (HSTs). In this article, we propose a cooperative mixed radio frequency (RF)-visible light communication (VLC) system to avoid the high penetration loss of the direct link between the end-users (UE) and the base station (BS). Our motivation is mainly based on the suitability of VLC technologies for indoor systems and their advantages to tackle forthcoming spectrum crunch, wide spectral availability, and easy bandwidth reuse. In the proposed system setup, the outdoor BS-relay is served by the backhaul RF links subject to double shadowing due to slow moving obstacles and pedestrian, while the data traffic inside the HST is conveyed by an indoor VLC system. Moreover, it is assumed that the relay node has imperfect channel state information (CSI) due to the mobility of the HST. We first statistically characterize the end-to-end signal-to-noise ratios (SNRs). Then, the performance is analyzed by deriving the exact closed-form expressions for key metrics such as outage probability and average bit error rate (BER).