Towards practical high throughput laser-based indoor optical wireless communication systems

Includes bibliographical references,

PhD;2024;Electrical Communication Engineering.

Wireless communication has become an essential necessity in our day-to-day life with majority of these systems currently use radio frequency (RF) technology to transmit information. To meet the high end requirements, new electromagnetic spectrum windows such as millimeter-wave, terahertz, and optical frequency bands are currently being explored. The use of the wide optical spectral window spanning from near infrared to visible for wireless communication encompasses optical wireless communication (OWC) technology. Intensity modulation/direct detection (IM/DD) is largely used in OWC systems, where changes in light intensity are how information is encoded and decoded using a square-law detector, which is usually a photodiode (PD). In this thesis experimental demonstration of such laser-based OWC links with enhanced functionalities for high data throughput multi-node data communication either using hardware diversity or non-orthogonal resource access, with practical implementations of RF-visible light communication (RF-VLC) hand-over and high throughput multimedia information transmission are discussed. A system level demonstration of real-time, high-quality multimedia bidirectional data streaming over a laser-based indoor VLC link has been separately characterized and found to support bandwidth as high as 800 MHz. Streaming of 1280 x 720 HD video is successfully demonstrated over this VLC link with an overall link data rate of 200 Mbps around RF carrier frequency at 245 MHz. The experimental implementation of the RF-VLC hand-over and its performance characterization are discussed. An experimental demonstration dual carrier modulation (DCM) resulted with a net data-rate of 4.2 Gbps for 64-quadrature amplitude modulation/orthogonal frequency division multiplexing (QAM/OFDM) at an optimum sampling rate of 1.5 G-samples/second. High data throughput non-orthogonal multiple access (NOMA) in OWC link is implemented for ~1 to 1.2-m link length with aggregated data rate of 1.02 Gbps for two users, called near and far users placed along the optical axis and at the cell edge respectively.