Performance of CR-QOSTBC for Multiple Receive Antennas in MIMO Systems

Multipath fading is inherent in wireless communication systems. Diversity is the techniques which takes the advantage of multipath and mitigate the effect of fading and increase signal strength. Space Time Block codes (STBC) are used in MIMO systems to improve the performance by maximizing transmit and/or receive diversity. Among different schemes based on STBC, Quasi orthogonal space time block code (QOSTBC) is able to achieve full rate transmission for more than two transmit antennas. Constellation rotation quasi orthogonal space time block code (CR-QOSTBC), a modified QOSTBC improves performance further and gets full diversity along with full rate, to overcome the limitation of QOSTBC, which is unable to maintain orthogonality amongst the codes transmitted by different antennas. Objective of this paper is to observe improvement in BER with reference to number of receive antennas, as higher diversity can be achieved by increasing uncorrelated paths between transmitter and receivers using higher number of receive antennas. Simulations were carried out under ideal as well as realistic environment using least square technique with four antennas at transmitter side and variable receive antennas. Results of simulations presented in this paper indicate performance improvement of CR-QOSTBC over QOSTBC in flat fading channel environment. Simulation results also shows performance degradation in BER when channel is estimated at the receiver.

[1]  Jean-François Hélard,et al.  Performance of STBC MC-CDMA systems over outdoor realistic MIMO channels , 2004, IEEE 60th Vehicular Technology Conference, 2004. VTC2004-Fall. 2004.

[2]  Ran Gozali,et al.  Space-Time Codes for High Data Rate Wireless Communications , 2002 .

[3]  Lizhong Zheng,et al.  Diversity and multiplexing: a fundamental tradeoff in multiple-antenna channels , 2003, IEEE Trans. Inf. Theory.

[4]  Stephan Sand,et al.  Iterative channel estimation for high mobility broadband MC-CDMA systems , 2005, IEEE International Conference on Communications, 2005. ICC 2005. 2005.

[5]  Constantinos B. Papadias,et al.  Improved quasi-orthogonal codes through constellation rotation , 2002, 2002 IEEE International Conference on Acoustics, Speech, and Signal Processing.

[6]  Xiang-Gen Xia,et al.  Closed form designs of complex orthogonal space-time block codes of rates (k+1)/(2k) for 2k-1 or 2k transmit antennas , 2004, ISIT.

[7]  Ari Hottinen,et al.  Minimal non-orthogonality rate 1 space-time block code for 3+ Tx antennas , 2000, 2000 IEEE Sixth International Symposium on Spread Spectrum Techniques and Applications. ISSTA 2000. Proceedings (Cat. No.00TH8536).

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

[9]  B. Badic.  Space-Time Block Coding for Multiple Antenna Systems , 2009 .

[10]  Costas N. Georghiades,et al.  A full-rate, full-diversity four-antenna quasi-orthogonal space-time block code , 2005, IEEE Transactions on Wireless Communications.

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

[12]  Petre Stoica,et al.  Space-Time block codes: A maximum SNR approach , 2001, IEEE Trans. Inf. Theory.

[13]  Liang Xian,et al.  Optimal rotation angles for quasi-orthogonal space-time codes with PSK modulation , 2005, IEEE Communications Letters.

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

[15]  F. Zheng,et al.  Space-time block coding for four transmit antennas over time-selective fading channels: orthogonal or non-orthogonal design? , 2003, 2003 IEEE 58th Vehicular Technology Conference. VTC 2003-Fall (IEEE Cat. No.03CH37484).

[16]  Ning Yang.  A family of space-time block codes for wireless communications , 2008 .

[17]  J. Guey,et al.  Signal design for transmitter diversity wireless communication systems over Rayleigh fading channels , 1996, Proceedings of Vehicular Technology Conference - VTC.

[18]  Helmut Bölcskei,et al.  An overview of MIMO communications - a key to gigabit wireless , 2004, Proceedings of the IEEE.