This is a technique to compress data transmitted by modems and other networks.

System of modulating a satellite signal. In the QPSK-modulation four phases of the radio frequency carrier, each differing each other by 90° degrees, are employed to represent two bits of the data stream.

Abbreviation for uadrature hase hift eying.Phase-shift keying in which four different phase angles are used. Each of the angles is usually 90° out of phase.