MATLAB Implementation of QPSK Modulation and Demodulation

This MATLAB-implemented QPSK modulation and demodulation program enables complete signal processing chain for QPSK systems. The code implements key algorithms including constellation mapping, pulse shaping using raised-cosine filters, carrier modulation/demodulation, and phase recovery techniques. The program processes input signals through modulation stages where binary data is mapped to QPSK symbols (phase shifts of 0°, 90°, 180°, 270°) and demodulation stages employing coherent detection with phase-locked loops for carrier recovery. The implementation includes error analysis modules calculating bit error rate (BER) and signal-to-noise ratio (SNR) performance metrics. Users can modify parameters like roll-off factors, sampling rates, and noise levels through configurable variables. The modular architecture allows easy extension to higher-order modulation schemes or integration with channel coding techniques, making it suitable for both educational purposes and practical communication system simulations.