Energy-efficient full diversity unitary space-time block code designs using QR decomposition

A novel energy-efficient unitary space-time block code (STBC) design using the recently-developed uniquely-factorable constellation pair (UFCP) concept and the QR decomposition is proposed for a noncoherent wireless communication system equipped with two transmitter antennas and a single receiver antenna. It is proved that the proposed UFCP-STBC design assures that the unique identification of both channel coefficients and transmitted signals in a noise-free case and full diversity in a noisy case. To further improve error performance, an optimal unitary UFCP-STBC is designed to maximize the coding gain subject to a transmission bit rate constraint by appropriately and uniquely factorizing a pair of energy-efficient cross quadrature amplitude modulation (QAM) constellations as well as by carefully adjusting the energy scale.