Power Control-Based Multi-User Li-Fi Using a Compound Eye Transmitter

In visible light communications (VLC), the transmitted signal is non-negative and real valued, and these characteristics constrain the signal space and provide new challenges for waveform design in a multi-user system. In Light Fidelity (Li- Fi), a VLC technology, and similar to radio frequency (RF) systems, precoder designs can be used to serve multiple users. However, a signal shaping algorithm is required to address the non-negativity of the transmitted signal in Li-Fi. In this study, a power allocation algorithm is proposed to achieve a multi-user Li-Fi system. A compound eye transmitter consisting of several LEDs pointing in different directions is used. This means that the process of the obtaining the inverse of the channel matrix in precoder design is not required. Results show that when a 30° semi-angle is used at the transmitter and the system has 4 users, the proposed transmission model can achieve 10^-5 average bit error rate (BER) performance at 1 dBm average transmission power.