A time spreaded quasi-orthogonal space-frequency coded scheme for OFDM systems

A space-frequency (SF) coded orthogonal frequency division multiplexing (OFDM) system performs well in fast fading channels. The Hadamard time spreading offers additional time diversity gain with low complexity to SF-OFDM systems. Since quasi-orthogonal codes give higher data rate as compared to the orthogonal codes, this paper proposes a time spreaded quasi-orthogonal SF-OFDM system (called T-QOSF-OFDM) to achieve higher data rates with robust performance in fast fading channels. The proposed system performance is analyzed for different maximum Doppler frequency (f
_d
) and time block spreading factor (M) via Monte-Carlo simulation. The T-QOSF-OFDM with 4 transmitter and 1 receiver antenna configuration offers 2 dB gain over orthogonal SF-OFDM system for f
_d
= 300 Hz and M = 64 at BER of 10
^-4
.