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Wavelength division multiple access in LiFi networks

  • Giovanni Luca Martena

Student thesis: Doctoral Thesis

Abstract

This thesis is focused on an indoor Light Fidelity (LiFi) network with a high amount of closely deployed Red-Green-Blue-Amber (RGBA) Access Point (AP)s and mobile users. The contributions made are threefold. Firstly, the impact of the Passband Shift (PS) effect is discussed in such a context, along with the challenges it entails. A generic system model is presented, including geometrical details, and the Probability Density Function (PDF) of the central wavelength of a shifted optical fi�lter spectrum is presented, which is dependent on user mobility behaviour. Based on this, a new parameter (the Spectral Overlap (SO)) that can facilitate system design choices is formally introduced, and an investigation on the bene�ts of optimising the Optical Front-End (OFE) for networked Visible Light Communication (VLC) with RGBA densely deployed APs is carried out. Secondly, a novel resource allocation scheme based on WD! (WD!) that can be used in the context of LiFi, called adaptive Wavelength Division Multiple Access (WDMA), is proposed. It allocates resources in a way that adapts to users' mobility behaviours by leveraging the PS effect and spatial separation while maintaining underlying compatibility with smart lighting solutions. By means of custom-written simulations, this scheme is tested against a �fixed benchmark, showing improved fairness in the allocation as well as lower Connection Loss (CL) probability. Thirdly, this scheme is evolved into its "adaptive Wavelength Division Multiple Access-Multiple Input Multiple Output (WDMA-MIMO)" version to achieve better utilisation of available network resources even in lowly crowded scenarios. It is then tested against �fixed benchmark in the context of increasing network crowdedness and considered in terms of handover rate. In terms of achievable data rate (both network and per-user), average Signal-to Interference-plus-Noise Ratio (SINR) in active channels, and CL, the �fixed benchmark is always outperformed by the proposed scheme.
Date of Award5 Feb 2025
Original languageEnglish
Awarding Institution
  • University Of Strathclyde
SupervisorIvan Andonovic (Supervisor) & Craig Michie (Supervisor)

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