QPSK Modulation and Demodulation in Rayleigh Fading Channels with BER Analysis

This study implements QPSK modulation and demodulation under Rayleigh fading channel conditions. The simulation calculates Bit Error Rate (BER) using Monte Carlo methods with large-scale random trials to ensure statistical significance. Key implementation details include generating Rayleigh fading coefficients using random Gaussian variables and applying coherent detection with maximum likelihood decision criteria. Performance evaluation compares simulated BER results against theoretical values derived from closed-form expressions for Rayleigh channels. Additional analysis examines BER trends across varying Signal-to-Noise Ratio (SNR) conditions, implemented through additive white Gaussian noise (AWGN) injection with power scaling. The experimental framework involves systematic SNR sweeping and averaging over multiple channel realizations to mitigate random fading effects. Results demonstrate strong alignment between simulated and theoretical BER curves, confirming QPSK's robust performance in Rayleigh fading environments. The MATLAB-based implementation utilizes built-in functions for QPSK constellation mapping/demapping and custom scripts for fading channel emulation and error counting mechanisms.