A study of some space-time codes with rates beyond one symbol per channel use

Space-time coding is an established technique for combating the impairments of wireless channels by means of the transmit diversity which is obtained by coding the information symbols over M transmit antennas and T symbol periods. Many existing space-time codes have good performance over the wireless channel, however, they offer small data rates compared to the actual capacity of the multi-antenna system. We study some M×T space-time block codes, for M=2,3,4 and T=2,4, with a rate of M symbols per channel use and a transmit diversity of T over a quasi-static or fast fading channel when using rotated versions of a multidimensional quadratic amplitude modulation with spectral efficiency of 2 bits per symbol. An extension to constellations with a higher spectral efficiency is also considered. We generalize the proposed codes to any number of transmit antennae M and any number of symbol periods T, such that we transmit at a rate of M symbols per channel use, and achieve a transmit diversity of T in fast fading