Seamless rate adaptation for indoor visible light communication without CSI at the transmitter

Abstract

Visible light communication (VLC), which uses LEDs for both lighting and communication purposes, has recently emerged as an alternative or support system to radio frequency (RF) communication. VLC channel between LEDs and photo-diodes is highly variable and pretty much depends on optical line of sight (LOS) and field of view (FOV). Therefore, received signal strength may vary dramatically, especially for mobile receivers. To ensure spectral efficient communication, it is essential to use rate adaptation methods. In this study, we propose rateless codes based rate adaptation method that adjusts transmission rate at receiver side and does not require channel state information (CSI) at the transmitter side. The spectral efficiency of the proposed method is analyzed and compared with adaptive modulation and coding (AMC) rate adaptation method widely used in literature. For analyses, we consider a realistic communication system model by using commercially available LEDs and also fulfilling illumination requirements. In order to minimize the multi-path effects, optical orthogonal frequency-division multiplexing (OFDM) is utilized. Numerical results indicate that proposed rate adaptive method can achieve seamless rate adaptation and has higher spectral efficiency compared to AMC in the presence of significant signal quality variations caused by mobility.