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Generalized quadratic receivers for unitary space-time constellations with orthogonal design over Rayleigh fading channels

Unitary space-time modulation is a transmit diversity technique for the nonselective Rayleigh fading channel. It was proposed for noncoherent detection without any channel state information (CSI) at the receiver. However, with perfect CSI at the receiver, the performance improvement is known to be approximately 2-4 dB. In order to exploit this improvement potential and keep the merit of not wasting bandwidth resources for additional training signals, we propose a generalized quadratic receiver (GQR) for a class of unitary space-time constellations with orthogonal design over the Rayleigh fading channel. As the channel memory span exploited by this GQR for channel estimation increases, the error probability of the GQR reduces from that of the conventional quadratic receiver to that of the coherent receiver. This performance improvement increases as the channel fade rate decreases. In addition, the complexity of the simplified GQR can be less than that of the noncoherent receiver.