Power Allocation Optimization Using Water-Filling Technique for MIMO-NOMA-Based Visible Light Communication Systems

This study investigates the use of Non-Orthogonal Multiple Access (NOMA) techniques to enhance the reachable sum bit rate in multi-user Visible Light Communication (VLC) systems that use Multiple Input Multiple Output (MIMO) technology. To optimize power allocation within indoor MIMO-NOMA-VLC systems, we propose a technique based on the Water-Filling Algorithm, which is compared to a Normalized Gain Difference Power Allocation (NGDPA) technique. Numerical simulations were conducted to assess the performance of a multi-user ($2 \times 2$) indoor MIMO-NOMA-VLC system. The obtained results showed that at higher offsets FWA starts to more significantly outperform NGDPA. The sum rate gain achieved with the FW technique is 3% higher, measured in megabits per second, compared to the NGPDA technique when using a normalized offset of 1. This indicates that the FW technique provides a more efficient use of available bandwidth, resulting in an increased data transfer rate. The main goal is to find an efficient and easy-to-implement power allocation method for indoor VLC MIMO-NOMA communication systems.