We demonstrate that the information theoretic capacity of multiple-transmit antenna systems is not reduced by using space-time orthogonal transmit schemes as means of exploiting the transmit diversity. Then, we consider concatenation of a channel code with space-time orthogonal transmit scheme, where data stream is first encoded with the channel code, and then transmitted using orthogonal space-time transmit scheme. Using this orthogonal space time transmit scheme the elements in the rpoduct criterion for code construction are made more uniform and hence better gain is achieved. We dreive code construction criterion for designing the channel code, taking into consideration coherence time of the channel.