Diffuse Optical Wireless Communication Research Articles

Propagation analysis and experiment of near-infrared VCSEL-based diffuse optical wireless communication.

Diffuse communication plays a more significant role than the usual point-to-point scenario in indoor optical wireless communication (OWC). We present, for the first time to our knowledge, a Monte Carlo simulation and experiment for a 922.39-nm vertical cavity surface-emitting laser array-based non-line-of-sight OWC system with three common reflective materials. The power distribution at the receiver of different reflectors is consistent with the numerical results, proving the validity by separating each reflection into specular and diffuse components. For gigabit Ethernet, all proposed diffuse systems can achieve around 1-GHz bandwidths, and more than 1.25-Gbps data rates over 1-m transmission distance with wide communication coverage. In addition, plastic film and iron plate diffused systems can achieve 2.125-Gbps data rates.

Multi-user indoor optical wireless communication system channel control using a genetic algorithm

A genetic algorithm controlled multispot transmitter is demonstrated that is capable of optimising the received power distribution for randomly aligned single element receivers in multiple fully diffuse optical wireless communications systems with multiple mobile users. Using a genetic algorithm to control the intensity of individual diffusion spots, system deployment environment changes, user movement and user alignment can be compensating for, with negligible impact on the bandwidth and root mean square delay spread. It is shown that the dynamic range, referenced against the peak received power, can be reduced up to 27% for empty environments and up to 26% when the users are moving. Furthermore, the effect of user movement, that can perturb the channel up to 8%, can be reduced to within 5% of the optimised case. Compared to alternative bespoke designs that are capable of mitigating optical wireless channel drawbacks, this method provides the possibility of cost-effectiveness for mass-produced receivers in applications where end-user friendliness and mobility are paramount.

Novel Techniques of Single-CarrierFrequency-Domain Equalization for Optical Wireless Communications

We investigate the use of single carrier frequency domain equalization (SCFDE) over a diffuse optical wireless (DOW) communications. Recently orthogonal frequency division multiplexing (OFDM) has been applied to DOW communications. However, due to high peak-to-average power ratio (PAPR), the performance of OFDM can severely be affected by the nonlinear characteristics of light emitting diodes (LED). To avoid a PAPR problem, we present in this paper a modified form of SCFDE for DOW communications. We propose three different ways of using SCFDE with DOW communications and show that they exhibit lower PAPR and provide better bit-error rate (BER) performance in the presence of the LED nonlinearity.

A feature extraction and pattern recognition receiver employing wavelet analysis and artificial intelligence for signal detection in diffuse optical wireless communications

Optical wireless diffuse indoor infrared communication systems have as yet large unrealized bandwidths that are not subject to the same regulatory control as radio frequency systems. Usually, well established RF techniques are used to combat channel imperfections for IR implementations. Here, we introduce a novel receiver system based on the multiresolution time-frequency feature extraction capabilities of wavelet analysis, coupled with the well recognized pattern recognition performance of artificial neural networks for mitigating the effects of bandwidth limiting channel-induced distortion.