Optimised Energy Efficiency of Various Cell Sizes in Laser-based Optical Wireless Communications

Optical Wireless Communication (OWC) networks have emerged as a solution to compliment traditional Radio Frequency (RF) networks due to limitations inherent in the latter. While Light Emitting Diodes (LEDs) were initially popular in OWC systems, their bandwidth limitations have prompted a shift towards Vertical-Cavity Surface-Emitting Lasers (VCSELs) for enhanced, reliable indoor communication. In this study, we investigate the deployment of VCSELs as Access Points (APs) within indoor environments, addressing the critical need for comprehensive spatial coverage across the communication plane. The extensive deployment of VCSELs required to achieve such coverage, however, introduces significant challenges, including inter-cell interference due to the proximity of multiple APs in overlapping operational zones and increased energy consumption due to the high number of APs. We study the performance of various AP cell structures, investigating the integration of multiple adjacent APs into a unified multi-AP cell using Zero Forcing (ZF) techniques to effectively manage overlap regions. Moreover, a power allocation optimisation problem is formulated to enhance the Data Rate (DR) and Energy Efficiency (EE) within the coverage area of the cell. Through comparing different ZF-based multi-AP configurations with and without the application of micro lenses to VCSEL arrays our findings reveal that a rise in the number of APs within cells boosts DR and EE at the cost of increased computational complexity. This complexity underscores a critical trade-off that demands careful consideration in the architectural design of future OWC systems.