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Joint Frequency Ambiguity Resolution and Accurate Timing Estimation in OFDM Systems with Multipath Fading


A serious disadvantage of orthogonal frequency-division multiplexing (OFDM) is its sensitivity to carrier frequency offset (CFO) and timing offset (TO). For many low-complexity algorithms, the estimation ambiguity exists when the CFO is greater than one or two subcarrier spacing, and the estimated TO is also prone to exceeding the ISI-free interval within the cyclic prefix (CP). This paper presents a method for joint CFO ambiguity resolution and accurate TO estimation in multipath fading. Maximum-likelihood (ML) principle is employed and only one pilot symbol is needed. Frequency ambiguity is resolved and accurate TO can be obtained simultaneously by using the fast Fourier transform (FFT) and one-dimensional (1D) search. Both known and unknown channel order cases are considered. Computer simulations show that the proposed algorithm outperforms some others in the multipath fading channels.



  1. 1.

    Bingham JAC: Multicarrier modulation for data transmission: an idea whose time has come. IEEE Communications Magazine 1990,28(5):5–14. 10.1109/35.54342

  2. 2.

    Pollet T, Moeneclaey M: Synchronizability of OFDM signals. Proceedings of IEEE Global Telecommunications Conference (GLOBECOM '95), November 1995, Singapore 3: 2054–2058.

  3. 3.

    Pollet T, Van Bladel M, Moeneclaey M: BER sensitivity of OFDM systems to carrier frequency offset and Wiener phase noise. IEEE Transactions on Communications 1995,43(2/3/4, part 1):191–193.

  4. 4.

    Moose PH: A technique for orthogonal frequency division multiplexing frequency offset correction. IEEE Transactions on Communications 1994,42(10):2908–2914. 10.1109/26.328961

  5. 5.

    van de Beek J-J, Sandell M, Börjesson PO: ML estimation of time and frequency offset in OFDM systems. IEEE Transactions on Signal Processing 1997,45(7):1800–1805. 10.1109/78.599949

  6. 6.

    Chen B, Wang H: Blind estimation of OFDM carrier frequency offset via oversampling. IEEE Transactions on Signal Processing 2004,52(7):2047–2057. 10.1109/TSP.2004.828899

  7. 7.

    Schmidl TM, Cox DC: Robust frequency and timing synchronization for OFDM. IEEE Transactions on Communications 1997,45(12):1613–1621. 10.1109/26.650240

  8. 8.

    Morelli M, D'Andrea AN, Mengali U: Frequency ambiguity resolution in OFDM systems. IEEE Communications Letters 2000,4(4):134–136. 10.1109/4234.841321

  9. 9.

    Chen C, Li J: Maximum likelihood method for integer frequency offset estimation of OFDM systems. Electronics Letters 2004,40(13):813–814. 10.1049/el:20040562

  10. 10.

    Park M, Cho N, Cho J, Hong D: Robust integer frequency offset estimator with ambiguity of symbol timing offset for OFDM systems. Proceedings of 56th IEEE Vehicular Technology Conference (VTC '02), September 2002, Vancouver, BC, Canada 4: 2116–2120.

  11. 11.

    Minn H, Zeng M, Bhargava VK: On timing offset estimation for OFDM systems. IEEE Communications Letters 2000,4(7):242–244. 10.1109/4234.852929

  12. 12.

    Minn H, Bhargava VK, Letaief KB: A robust timing and frequency synchronization for OFDM systems. IEEE Transactions on Wireless Communications 2003,2(4):822–839.

  13. 13.

    Morelli M, Mengali U: Carrier-frequency estimation for transmissions over selective channels. IEEE Transactions on Communications 2000,48(9):1580–1589. 10.1109/26.870025

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Correspondence to Jun Li.

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Li, J., Liao, G. & Ouyang, S. Joint Frequency Ambiguity Resolution and Accurate Timing Estimation in OFDM Systems with Multipath Fading. J Wireless Com Network 2006, 062173 (2006).

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  • Fast Fourier Transform
  • Fading Channel
  • Ambiguity Resolution
  • Carrier Frequency Offset
  • Cyclic Prefix