Generalized Quadratic Receivers for Orthogonal and Nonorthogonal Unitary Space-Time Constellations over Rayleigh Fading Channels

We propose the generalized quadratic receivers (GQRs) for orthogonal and general nonorthogonal unitary space-time constellations, respectively, over the flat Rayleigh fading channel. The GQRs exploit the performance improvement potential, known to be approximately 2¿4 dB, between the noncoherent quadratic receiver (QR) and the coherent receiver (CR), without wasting bandwidth resources for additional training signals. For both the cases of orthogonal and nonorthogonal unitary space-time constellations, as the channel memory span exploited for channel estimation increases, the error probabilities of the GQRs reduce from that of the QR and approach that of the CR. The GQRs are shown to be effective for both slow and fast fading channels, and the performance improvements increase as the channel fade rate decreases.