Analog Modulation and Demodulation under AWGN Channel Model

The AWGN channel (Additive White Gaussian Noise channel) serves as a fundamental channel model in communication system simulations, commonly used to emulate noise interference encountered during signal transmission in real-world environments. Under this channel model, signals are affected by additive Gaussian white noise, which impacts demodulation performance at the receiver side.

Analog modulation techniques represent classical methods in communications that carry information by altering the amplitude, frequency, or phase of carrier signals. Common analog modulation schemes include Amplitude Modulation (AM), Frequency Modulation (FM), and Phase Modulation (PM). Under AWGN conditions, modulated signals become contaminated with noise, requiring the demodulator to employ appropriate algorithms to recover the original information.

On the MATLAB platform, we can conveniently implement the complete workflow of modulation, AWGN addition, and demodulation. The implementation typically involves generating baseband signals (such as voice or data signals) using functions like chirp or sawtooth, followed by modulation through dedicated functions like ammod for AM or fmmod for FM. The AWGN channel is simulated using MATLAB's awgn function, which adds random Gaussian noise to the transmitted signal with specified SNR parameters. For demodulation, corresponding functions like amdemod and fmdemod are employed, often incorporating filtering techniques using fir1 or coherence detection algorithms to recover the baseband information from noise-corrupted signals.

By adjusting the Signal-to-Noise Ratio (SNR) parameter, system performance metrics like Bit Error Rate (BER) or SNR degradation can be analyzed under different noise intensities, enabling evaluation of modulation schemes' noise resistance capabilities. This simulation process provides crucial references for communication system optimization and algorithm improvement, where MATLAB's berawgn function can be utilized for theoretical BER calculations and performance comparisons.