A new data rotation based CP synchronization scheme for OFDM systems

In this paper, a new data rotation scheme for improving the symbol timing and carrier frequency offset (CFO) estimation of orthogonal frequency-division multiplexing (OFDM) systems is proposed. The new data rotation scheme intentionally introduces a cyclic shift after the inverse fast Fourier transform (IFFT) in the transmitter so that a higher energy cyclic prefix (CP) is obtained. This cyclic shift will not impair the orthogonality among the subcarriers and will only results in phase shift in the demodulated signal at the receiver. To recover the cyclic shift and for data detection, the scheme makes use of double differential encoding and decoding at the transmitter and the receiver. We analyze the performance of the new data rotation scheme by using order statistics theory. Our results show that the new scheme can provide a 1.6 dB gain in the performance of the CFO estimator and a 6 dB gain for the timing estimator at 15 dB SNR over AWGN channel, as well as a 6 dB gain in lock-in probability and a 4 dB gain in CFO performance at 5 dB SNR over frequency selective fading channel.

[1]  Sayfe Kiaei,et al.  Class of cyclic-based estimators for frequency-offset estimation of OFDM systems , 2000, IEEE Trans. Commun..

[2]  Donghoon Lee,et al.  Coarse symbol synchronization algorithms for OFDM systems in multipath channels , 2002, IEEE Commun. Lett..

[3]  John M. Cioffi,et al.  Blind OFDM symbol synchronization in ISI channels , 1998, IEEE GLOBECOM 1998 (Cat. NO. 98CH36250).

[4]  Hui Liu,et al.  A high efficiency carrier estimator for OFDM communications , 1998, Conference Record of the Thirty-First Asilomar Conference on Signals, Systems and Computers (Cat. No.97CB36136).

[5]  Donald C. Cox,et al.  Robust frequency and timing synchronization for OFDM , 1997, IEEE Trans. Commun..

[6]  H. A. David,et al.  Order Statistics (2nd ed). , 1981 .

[7]  Per Ola Börjesson,et al.  ML estimation of time and frequency offset in OFDM systems , 1997, IEEE Trans. Signal Process..

[8]  Jian Sun,et al.  Frequency and timing synchronization and channel estimation in preamble based OFDM system , 2002, IEEE 2002 International Conference on Communications, Circuits and Systems and West Sino Expositions.

[9]  Hikmet Sari,et al.  Transmission techniques for digital terrestrial TV broadcasting , 1995, IEEE Commun. Mag..

[10]  U. Tureli,et al.  A high-efficiency carrier estimator for OFDM communications , 1997, IEEE Communications Letters.

[11]  Helmut Bölcskei,et al.  Blind estimation of symbol timing and carrier frequency offset in wireless OFDM systems , 2001, IEEE Trans. Commun..

[12]  Didem Kivanc-Tureli,et al.  Experimental and analytical studies on a high-resolution OFDM carrier frequency offset estimator , 2001, IEEE Trans. Veh. Technol..

[13]  Damien Castelain,et al.  Digital sound broadcasting to mobile receivers , 1989 .

[14]  Heinrich Meyr,et al.  Frame synchronization of OFDM systems in frequency selective fading channels , 1997, 1997 IEEE 47th Vehicular Technology Conference. Technology in Motion.

[15]  Elvino S. Sousa,et al.  Coded OFDM for broadband indoor wireless systems , 1997, Proceedings of ICC'97 - International Conference on Communications.