Unitary nonuniform space-time constellations for the broadcast channel

We propose a new class of unitary space-time matrix constellations that have nonuniform error performance. Such codes are important for transmission over a broadcast, or point-to-multipoint, communication channel and when scalable source coding is used. Our new codes can be encoded differentially and are based entirely on phase-shift keying. Analytical design criteria are discussed and a simulation result is presented to exemplify the designs.