Capacity Variation of an Indoor MIMO VLC System for a Pyramid Receiver

In an indoor MIMO visible light communication (VLC) system, LoS links are present between transmitter and receiver. As no fading components are present in an indoor environment, MIMO channels can be highly correlated and a mechanism to reduce channel correlation is essential to enjoy the benefits of the MIMO system. In order to get high multiplexing gain a MIMO system may employ an angle diversity receiver (ADR) in which normal vectors of photodetectors (PDs) point in different directions resulting in an uncorrelated channel matrix. This paper expands the work of a special type of ADR called pyramid receiver (PR) and tries to explore the effect of elevation angles on the capacity of MIMO VLC system. Channel capacity for different field-of-view (FOV) environments is calculated across the entire room using different combinations of PDs elevation angles for a 4x4 MIMO VLC system. Optimum elevation angles resulting in maximum capacity are recorded. Results show that system performance at FOV angle 60° is better as compared to 90°. Results also show that system performance can be improved by allowing each PD to have its own optimum elevation angle but, this comes at a cost of receiver design complexity.