Rate-splitting multiple access for indoor visible light communication networks

Visible light communication (VLC) has been emerged as a technology that can increase the channel capacity in the next generations of wireless technologies by exploiting the largely unutilized, licence-free and huge visible light portion of the electromagnetic spectrum. In order to enable high-speed short-range wireless communications, VLC utilizes the installed high-switching rate light emitting diodes (LEDs) in the ceilings of indoor environments, which are primarily used for illumination, to modulate the signals into visible light intensity. However, VLC suffers from several limitations, such as the limited modulation bandwidth and the coverage area of LEDs that degrade the overall system spectral efficiency (SE). In this respect, the present contribution proposes rate splitting multiple access (RSMA) for multi-cell indoor VLC systems as a mean to enhance the overall system SE and energy efficiency (EE) as well as to provide ubiquitous indoor coverage and to address user mobility issues. Moreover, we utilize coordinated beamforming to design the precoders of the common and the private streams in each cell aiming to enhance the performance of cell-edge users. Finally, the formulated sum of the mean squared error optimization problem is solved sub-optimally using an alternating optimization approach. Extensive computer simulations demonstrate that RSMA improves the overall system performance in terms of the SE and EE compared to the recently used multiple access techniques, such as space division multiple access with coordinated beamforming which constitutes a special case of it.