20 Gbps Mobile Indoor Visible Light Communication System Employing Beam Steering and Computer Generated Holograms

Visible light communication (VLC) systems have typically operated at data rates below 10 Gbps and operation at this data rate was shown to be feasible by using laser diodes (LDs), imaging receivers and delay adaptation techniques (DAT imaging LDs-VLC). However, higher data rates, beyond 10 Gbps, are challenging due to the low signal to noise ratio (SNR) and inter symbol interference (ISI). In this paper, for the first time, to the best of our knowledge, we propose, design and evaluate a VLC system that employs beam steering (of part of the VLC beam) using adaptive finite vocabulary of holograms in conjunction with an imaging receiver and a delay adaptation technique to enhance SNR and to mitigate the impact of ISI at high data rates (20 Gbps). An algorithm was used to estimate the receiver location, so that part of the white light can be directed towards a desired target (receiver) using beam steering to improve SNR. Simulation results of our location estimation algorithm (LEA) indicated that the required time to estimate the position of the VLC receiver is typically within 224 ms in our system and environment. A finite vocabulary of stored holograms is introduced to reduce the computation time required by LEA to identify the best location to steer the beam to the receiver location. The beamsteering approach improved the SNR of the fully adaptive VLC system by 15 dB at high data rates (20 Gbps) over the DAT imaging LDs-VLC system in the worst case scenario. In addition, we examined our new proposed system in a very harsh environment with mobility. The results showed that our proposed VLC system has strong robustness against shadowing, signal blockage and mobility.