This document contains code for performing various digital signal processing and modulation techniques, including: - PCM and demodulation of sampled signals - Delta modulation and adaptive delta modulation of signals - Generation of ASK, FSK, and PSK modulated signals using a random binary sequence and adding AWGN noise - Calculation of the bit error rate for the three modulation schemes over varying SNR levels - Implementation of direct sequence spread spectrum modulation and demodulation using a pseudo-random sequence.