A Simple Carrier Frequency Offset Synchronization Strategy for Multiple Relay Cooperative Diversity OFDM System

Mudassar I. Cheema, Shoab A. Khan


Cooperative Diversity Orthogonal Frequency Division Modulation (CD-OFDM) systems are very sensitive to synchronization errors. In CD-OFDM, synchronization is more complex because all cooperative nodes (CNs) have their own frequency oscillator and different channel path which results in different timing and carrier frequency offset (CFO) for each node. Consequently, each node has to be synchronized separately without affecting the synchronization process of other nodes. All CNs transmit simultaneously during cooperation phase (C-phase) and their aggregate signal is received at the destination node. A unique frequency domain (FD) preamble is proposed for each CN during Cphase that will allow simple separation of cooperative nodes. These FD multiplexed preambles make the synchronization problem identical to OFDMA uplink. OFDMA system typically uses highly complex iterative CFO estimators for uplink synchronization. However, a simple one-shot CFO estimator is proposed that uses repeated preamble of two OFDM symbol duration. The proposed method is computationally efficient because it relies on FFT operation for user separation and interference mitigation. Subsequently, time domain (TD) multiplication is used for CFO correction of each CN. Furthermore, a CD-OFDM protocol for data transmission is presented that suites the proposed estimator and harnesses spatial diversity. The proposed estimator shows good statistical results during simulations in AWGN and Rayleigh environments. During evaluation, estimator variance, mean square error and symbol error rate are used as performance measure.

Full Text:



M. I. Cheema and S. A. Khan, "A Robust Coarse Timing Synchronizer Design for Cooperative Diversity OFDM System," International Journal of Information and Electronics Engineering (IJIEE), Accepted for publication, 2013.

Y. Li and G. Stüber, Orthogonal Frequency Division Multiplexing for Wireless Communications, Boston, MA: SpringerVerlag, 2006.

E. Biglieri, R. Calderbank, A. Constantinides, A. Goldsmith, A. Paulraj and V. H. Poor, MIMO Wireless Communications, Cambridge, U.K: Cambridge Univ. Press, 2007.

A. Nosratinia, T. E. Hunter and A. Hedayat, "Cooperative communication in wireless networks," IEEE Commun. Mag, vol. 42, no. 10, p. pp. 74–80, Oct. 2004.

Part 16: Air Interface for Broadband Wireless Access Systems, Ammendment 1: Multihop Relay specification, IEEE LAN/MAN standard 802.16j, 2009.

P. H. Moose, "A technique for orthogonal frequency division multiplexing frequency offset correction," IEEE Trans. Commun, vol. 42, no. 10, p. 2908–2914, Oct. 1994.

S. Barbarossa, M. Pompili and G. B. Giannakis, "Channel-independent synchronization of orthogonal frequency division multiple access systems," vol. 20, no. 2, p. 474–486, Feb. 2002.

M. O. Pun, M. Morelli and C. J. Kuo, "Maximum-likelihood synchronization and channel estimation for OFDMA uplink transmissions," IEEE Transactions on Communications, vol. 54, no. 4, p. 726–736, April 2006.

M. O. Pun, M. Morelli and C. C. J. Kuo, "Iterative detection and frequency synchronization for OFDMA uplink transmissions," IEEE Trans. Wireless Commun., vol. 6, no. 2, p. 629–639, Feb. 2007.

Q. Huang, M. Ghogho and J. Wei, "Data detection in cooperative STBCOFDM systems with multiple frequency offsets," IEEE Signal Processing Letters, vol. 16, no. 7, pp. 600-603, 2009.

J. Choi, C. Lee, H. W. Jung and Y. H. Lee, "Carrier frequency offset compensation for uplink of OFDM-FDMA systems," IEEE Communications Letters, vol. 4, no. 12, p. 414– 416, December 2000.

D. Huang and K. B. Letaief, "An interferencecancellation scheme for carrier frequency offsets correction in OFDMA systems," IEEE Transactions on Communications, vol. 53, no. 7, p. 1155–1165, July 2005.

X. Li, F. Ng and T. Han, "Carrier frequency offset mitigation in asynchronous cooperative OFDM transmissions," IEEE Transactions on Signal Processing, vol. 56, no. 2, pp. 675-685, 2008.

Q. Huang, M. Ghogho, J. W. a and P. Ciblat, "Practical timing and frequency synchronization for OFDM based Cooperative systems," IEEE Trans. on Signal Processing, vol. 58, no. 7, p. 3706–3716, July 2010.

P. Murphy and A. Sabharwa, "Design, Implementation, and Characterization of a Cooperative Communications System," IEEE TRANSACTIONS ON VEHICULAR TECHNOLOGY, vol. 60, no. 6, July 2011.

M. I. Cheema and S. A. Khan, "A Low Complexity Fine Timing Offset and Channel Estimation Algorithm for Cooperative Diversity OFDM System," March 2011.

O.-S. Shin and V. Tarokh, "Design of an OFDM Cooperative Space-Time Diversity System," IEEE Transactions on Vehicular Technology, vol. 56, no. 4, pp. 2203-2215, July 2007.

Copyright (c) 2016 Mudassar I. Cheema

Powered By KICS