Analysis of turbo coded OFDM systems employing space-frequency block code in double selective fading channels

Transmit diversity can be applied to orthogonal frequency division multiplexing (OFDM) systems by adopting space-frequency block coding (SFBC). To carry out simple linear decoding, it is usually assumed that the channel remains constant within an OFDM symbol. However, this assumption becomes unreliable when the system operates in a severe multipath environment presenting time and frequency selective fading. Due to this fact and that the received signal is composed by overlapped signals transmitted from different transmit antennas, channel estimation is rather challenging in SFBC-OFDM systems. In this paper, we analyze the performance of a SFBC- OFDM system employing turbo coding and a channel estimation scheme based on frequency domain comb-type pilot insertion and linear and spline interpolation to improve the performance of conventional SFBC-OFDM systems in double selective fading channels. Simulation results show that linear interpolation is more adequate for turbo SFBC-OFDM systems.