Abstract—We compare four open-loop transmit diversityschemes in a coded Orthogonal Frequency DivisionMultiplexing (OFDM) system with four transmit antennas,namely cyclic shift diversity (CSD), Space-Time Block Code(STBC, Alamouti code is used) with CSD, Quasi-OrthogonalSTBC (QO-STBC) and Minimum-Decoding-ComplexityQOSTBC (MDC-QOSTBC). We show that in a codedsystem with low code rate, a scheme with spatial transmitdiversity of second order can achieve similar performance tothat with spatial transmit diversity of fourth order due tothe additional diversity provided by the phase shift diversitywith channel coding. In addition, we also compare thedecoding complexity and other features of the above fourmentioned schemes, such as the requirement for the trainingsignals, hybrid automatic retransmission request (HARQ),etc. The discussions in this paper can be readily applied tomany modern wireless communication systems, such asmobile systems beyond 3G, IEEE 802.11 wireless LAN, orIEEE 802.16 WiMAX, that employ more than two transmitantennas and OFDM.
 
Index Terms—open loop transmit diversity, coded OFDM,low decoding complexity, quasi-orthogonal design, cyclicshift diversity, cyclic delay diversity, space-time block code

Cite: C. Yuen, Y. Wu, S. Sun, "Four Transmit Diversity Schemes for Coded OFDM Systems with Four Transmit Antennas," Journal of Communications, vol. 3, no.4, September, pp. 1-7, 2008.