Abstract
In this paper, we introduce an adaptive optical wireless system that employs a finite vocabulary of stored holograms. We propose a fast adaptation approach based on a divide and conquer methodology resulting in a number of adaptation algorithms: fast angle adaptive holograms (FAA-Holograms), fast power adaptive holograms (FPA-Holograms), and fast angle and power adaptive holograms (FAPA-Holograms) and evaluate these in mobile optical wireless (OW) systems in conjugation with imaging reception. The ultimate goal is to improve the signal-to-noise ratio (SNR), to reduce the effect of intersymbol-interference (ISI), to speed up the adaptation process, and to eliminate the need to calculate the hologram in real-time at each transmitter and receiver location. The system operates at high data rates under the impact of multipath dispersion, background noise and mobility. At a data rate of 2.5 Gb/s and under eye safety regulations, the proposed FAPA-Holograms offers around 20 dB SNR in the presence of background shot noise, receiver noise, multipath dispersion, and mobility. Simulation results show that the proposed system, FAPA-Holograms, can reduce the time required to identify the optimum hologram position from 80 ms in the original beam angle and power adaptive line strip multibeam system (APA-LSMS) to about 13 ms.