An effective technique to improve wireless communication performance is transmit diversity. In this work, transmitter diversity using a new combination of space-time block codes (STBCs) concatenated with orthogonal frequency division multiplexing (OFDM) system in high-speed wireless data communication is investigated. Simulation results demonstrate that this scheme can achieve a significant performance increase for efficient data transmission over slow and fast fading environments, compared to conventional OFDM. Performance of proposed scheme has been compared to an STBC-OFDM scheme and it is evident that SFBC is more robust than STBC- OFDM system in a fast fading environment. © 2004IEEE.