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 (fd) 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 fd = 300 Hz and M = 64 at BER of 10-4.

[1]  Xiang-Gen Xia,et al.  Space-Time/Frequency Coding for MIMO-OFDM in Next Generation Broadband Wireless Systems , 2007, IEEE Wireless Communications.

[2]  Douglas B. Williams,et al.  A space-frequency transmitter diversity technique for OFDM systems , 2000, Globecom '00 - IEEE. Global Telecommunications Conference. Conference Record (Cat. No.00CH37137).

[3]  Abbas Jamalipour,et al.  Wireless communications , 2005, GLOBECOM '05. IEEE Global Telecommunications Conference, 2005..

[4]  Theodore S. Rappaport,et al.  Wireless communications - principles and practice , 1996 .

[5]  Siavash M. Alamouti,et al.  A simple transmit diversity technique for wireless communications , 1998, IEEE J. Sel. Areas Commun..

[6]  Joonhyuk Kang,et al.  Quasi-orthogonal space-frequency block code , 2004, IEEE International Symposium on Communications and Information Technology, 2004. ISCIT 2004..

[7]  Hamid Jafarkhani.  A quasi-orthogonal space-time block code , 2001, IEEE Trans. Commun..

[8]  Sang-Soon Park,et al.  A simple STF-OFDM transmission scheme for fast fading channels , 2004, IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall. 2004.

[9]  Douglas B. Williams,et al.  A space-time coded transmitter diversity technique for frequency selective fading channels , 2000, Proceedings of the 2000 IEEE Sensor Array and Multichannel Signal Processing Workshop. SAM 2000 (Cat. No.00EX410).

[10]  H. Bölcskei,et al.  MIMO-OFDM wireless systems: basics, perspectives, and challenges , 2006, IEEE Wireless Communications.

[11]  A. Robert Calderbank,et al.  Space-Time block codes from orthogonal designs , 1999, IEEE Trans. Inf. Theory.

[12]  Constantinos B. Papadias,et al.  A space-time coding approach for systems employing four transmit antennas , 2001, 2001 IEEE International Conference on Acoustics, Speech, and Signal Processing. Proceedings (Cat. No.01CH37221).