Design of space-time block coded unique word OFDM systems

In this paper we develop space-time block codes for unique word - orthogonal frequency division multiplexing (UW-OFDM) systems to fully exploit the diversity gain when the channel state information is not available at the transmitter. To this end, we propose two novel space-time block codes (STBCs) for UW-OFDM systems, namely a frequency domain space-time block code and a time-reversal space-time code (TR-STC). The former one is an extension of the traditional space-frequency block codes (SFBCs) for CP-OFDM systems to UW-OFDM systems while the latter one makes use of the frame structure of the UW-OFDM symbols and has a low complexity decoder. Simulation results show that both of the proposed space-time block codes achieve a significant gain compared to the SFBC based CP-OFDM. Moreover, the frequency domain STBC yields a slightly better performance as compared to the TR-STC but has a higher computational complexity.