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

Authors

  • Mudassar I. Cheema
  • Shoab A. Khan

Abstract

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.

References

William H. Press, Saul A. Teukolsky, William T. Veltering, Brian P. Flannery. (2007). Numerical Recipes.3rd ed. Cambridge University Press.

Gerald C. F. & Wheatly P. O. (2005). Applied Numerical Analysis. 6th ed. Pearson Education Inc.

Julien Diaz, Marcus J. Grote. (2009). Energy Conserving Explicit Local Time Stepping for Second Order Wave Equations. SIAM J. Sci. Comput Vol.31 No 3 pp.1985-2014.

H-.Kries, N.A. Peterson, J. Ystrom. (2002). Difference Approximations for the Second Order Wave Equation. SAIM J. Numer.Anal.,40 pp1940-1967.

Burden, R.L. & Faires, J.D. (2001) Numerical Analysis, 7th ed., Thomson Brooks/Cole.

J. D. (2006). Hoffman. Numerical Methods for Engineers and Scientists.2nd ed. Marcel Dekker, inc.

Reddy J.N. (2006). An Introduction to the Finite Element Method. 3rd ed., McGraw Hill International Ed.

Sastry S.S. (2005). Introductory Method of Numerical Analy sis. 4th ed. Prentice-Hall of India Private Ltd.

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Published

2016-06-22

Issue

Section

Electrical Engineering and Computer Science