Space-time block codes: A capacity perspective

Space-time block codes are a remarkable modulation scheme discovered recent ly for the multiple antenna wireless channel. They have an elegant mathemat ical solution for providing full diversity over the coherent, flat-fading c hannel, In addition, they require extremely simple encoding add decoding. A lthough these codes provide full diversity at low computational costs, we s how that they incur a loss in capacity because they convert the matrix chan nel into a scalar AWGN channel whose capacity is smaller than the true chan nel capacity. In this letter the loss in capacity is quantified as a functi on of channel rank, code rate, and number of receive antennas.