Holograms in Optical Wireless Communications

Adaptive beam steering in optical wireless communication (OWC) system has been shown to offer performance enhancements over traditional OWC systems. However, an increase in the computational cost is incurred. In this chapter, we introduce a fast hologram selection technique to speed up the adaptation process. We propose a fast delay, angle and power adaptive holograms (FDAPA-Holograms) approach based on a divide and conquer methodology and evaluate it with angle diversity receivers in a mobile optical wireless (OW) system. The fast and efficient fully adaptive FDAPA-Holograms system can improve the receiver signal to noise ratio (SNR) and reduce the required time to estimate the position of the receiver. The adaptation techniques (angle, power and delay) offer a degree of freedom in the system design. The proposed system FDAPA-Holograms is able to achieve high data rate of 5 Gb/s with full mobility. Simulation results show that the proposed 5 Gb/s FDAPA-Holograms achieves around 13 dB SNR under mobility and under eye safety regulations. Furthermore, a fast divide and conquer search algorithm is introduced to find the optimum hologram as well as to reduce the computation time. The proposed system (FDAPA-Holograms) reduces the computation time required to find the best hologram location from 64 ms using conventional adaptive system to around 14 ms

Uplink Design in VLC Systems with IR Sources and Beam Steering

The need for high-speed local area networks to meet the recent developments in multimedia and video transmission applications has recently focused interest on visible light communication (VLC) systems. Although VLC systems provide lighting and communications simultaneously from light emitting diodes, LEDs, the uplink channel design in such a system is a challenging task. In this paper, we propose a solution in which the uplink challenge in indoor VLC is resolved by the use of an Infrared (IR) link. We introduce a novel fast adaptive beam steering IR system (FABS-IR) to improve the uplink performance at high data rates while providing security for applications. The goal of our proposed system is to enhance the received optical power signal, speed up the adaptation process and mitigate the channel delay spread when the system operates at a high transmission rate. The channel delay spread is minimised from 0.22 ns given by hybrid diffuse IR link to almost 0.07 ns. At 2.5 Gb/s, our results show that the imaging FABS-IR system accomplished about 11.7 dB signal to noise ratio (SNR) in the presence of multipath dispersion, receiver noise and transmitter mobility

Collaborative VLC/IROW Systems

Dimming is an important feature of an indoor lighting system where the illumination level can be controlled by the user. Therefore, integrating a visible light communication (VLC) system with an illumination system poses some challenges. One of the main issues is that the light unit should be “ON” all the time to ensure continuous communication. To ensure acceptance and adoption of VLC systems, an important issue should be addressed: how to communicate when the lights are “OFF” or partially dimmed. In this chapter, we propose five new infrared optical wireless (IROW) systems to support VLC systems when the light is totally turned off or significantly dimmed. To take advantage of both VLC and IROW, we introduce and implement the concept of a collaborative VLC/IROW system. In addition, we investigate the impact of partial dimming on the VLC system’s performance, and we propose an adaptive rate technique (ART) to mitigate the impact of light dimming. Moreover, in the case of no dimming, the VLC and IROW systems can collaborate to increase the data rate so it is higher than that in the pure VLC system. We have achieved 10 Gbps in an indoor environment, which is a 2× increase in the data rate compared with a pure VLC system