This code implements QPSK and its improved OQPSK modulation
QPSK.m : It shows how I, Q signals multiply with high frequency carriers (cos(2pifct) and sin(2pifct)) After IQ mapping, binary sequences also need to go through the raised cosine roll off filter for pulse shaping.
OQPSK.m : Q signal is 0.5 seconds later than I signal. Therefore, the envelope of OQPSK signal changes smoothly, and the nonlinear power amplifier amplifies without much distortion