High rate quasi-orthogonal space-time block code designs for four transmit antennas

This paper addresses the design of high rate quasi-orthogonal space-time block codes, with rates of 1.5 and 13/8, to give improved performance. Three different quasi-orthogonal designs are presented which are variants of previous quasi-orthogonal designs to give higher code rates. The first two variants transform rate I designs to rate 1.5 designs, the third variant transforms a rate 9/8 design to a rate 13/8 design. The designs presented are shown to be particularly attractive in terms of greater effective throughput for medium-to-high signal-to-noise ratio with a 4-ary input constellation.