Comparative Analysis of Fixed-Gain, PID, and Adaptive PID Controllers for AGC in VLC Receivers

Abstract

The Visible light communication represents a promising technology for high-speed, secure and low-cost wireless communications. However, the variability of the optical channel, the presence of noise and the positioning of the receiver affect the quality of the signal received through this medium. This article presents a comparative analysis of the performance of an AGC gain block incorporated after the Photodiode and the Trans Impedance Amplifier, for three configurations: the first with fixed gain and without control, the second with classic PID control with fixed gains, and the third with adaptive PID control based on fuzzy logic. The system was implemented in a MATLAB simulation environment, considering a realistic model that includes the optical signal, Gaussian noise, and variable distance between the transmitter and receiver. The diffuse adaptive PID controller improves reference tracking and reduces error compared to conventional methods but increases computational load and processing delays. In contrast, the fixed-gain PID controller is simpler and allows overshoot to enhance transient performance and the $e_{s s}$, which may cause increased physical stress or wear during implementation.