Optimized nonuniform PSK for multiclass traffic and its application to space-time block codes

We construct nonuniform phase-shift keying (PSK) constellations that provide unequal error protection for multiclass traffic such as compressed voice and video data. Then closed-form expressions expression for the exact bit-error rate (BER) of the nonuniform PSK constellations is derived in multiple receive-antenna systems over Rayleigh fading channels. Based on this BER analysis, we optimize the nonuniform PSK constellations such that the BERs of all the bits of each class are equalized or such that the total transmission power is minimized subject to the average BER constraints. In particular, we demonstrate that even for transmitting single-class traffic, the optimized nonuniform PSK constellations can be better than the conventional uniform PSK. Finally, we extend the nonuniform PSK constellations to space-time coded communications systems with multiple transmit and multiple receive antennas.