Beam Domain Massive MIMO Optical Communications with Power Allocation and Movable Lens

Traditional visible light communication systems do not exploit narrow beams so their power efficiency is limited. Therefore, some recent works suggested using a lens and a light-emitting diode (LED) array to generate narrow beams towards the user terminal (UT). However, the generated beams have blind areas and are not optimized with respect to the coordinate of the UT. In this paper, we propose a simple solution by determining which LEDs should be lighted in the array and how to distribute the restricted transmit power based on the coordinate of UT to maximize the received power in different cases. The scheme can realize beam direction adjustment and maximize energy efficiency whether the LEDs have power constraints or not. Simulation results show that there is a close relationship between the channel gain and the power allocation scheme, and the LED-to-lens distance can also be optimized to improve the received power.