A Novel Quasi-Orthogonal Space-Frequency Block Code for Single-Carrier FDMA

Single-carrier frequency division multiple access (SC-FDMA) is a recent modulation technique combining most of the advantages of orthogonal frequency division multiple access (OFDMA) with the low peak-to-average power ratio (PAPR) of single-carrier transmission. For these reasons, it has been adopted as a possible air interface on the uplink of future wireless networks. It is also suitable for any other system in which a low PAPR is desired. In this paper, we highlight the severe limitations of existing space-time and space-frequency block codes when combined with SC-FDMA, and we propose a novel quasi-orthogonal space-frequency block code compatible with a SC-FDMA system with four transmit antennas. We show that our proposed preceding keeps the single-carrier property of the signal on all of the four transmit antennas and we also prove the good performance of our scheme on frequency selective channels with spatial correlation.