Open Access Open Badges Research Article

Channel Impulse Response Length and Noise Variance Estimation for OFDM Systems with Adaptive Guard Interval

VanDuc Nguyen1*, Hans-Peter Kuchenbecker2, Harald Haas3, Kyandoghere Kyamakya4 and Guillaume Gelle5

Author Affiliations

1 Department of Communication Engineering, Faculty of Electronics and Telecommunications, Hanoi University of Technology, 1 Dai Co Viet Street, Hanoi, Vietnam

2 Institut für Allgemeine Nachrichtentechnik, Universität Hannover, Appelstrasse 9A, Hannover 30167, Germany

3 School of Engineering and Science, International University Bremen, Campus Ring 12, Bremen 28759, Germany

4 Department of Informatics-Systems, Alpen Adria University Klagenfurt, Universitätsstrasse 65-67, Klagenfurt 9020, Austria

5 CReSTIC-DeCom, University of Reims Champagne-Ardenne, Moulin de la Housse, BP 1039, Reims Cedex 2 51687, France

For all author emails, please log on.

EURASIP Journal on Wireless Communications and Networking 2007, 2007:024342  doi:10.1155/2007/24342

The electronic version of this article is the complete one and can be found online at:

Received:5 October 2005
Revisions received:16 August 2006
Accepted:14 November 2006
Published:21 February 2007

© 2007 Nguyen et al.

This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

A new algorithm estimating channel impulse response (CIR) length and noise variance for orthogonal frequency-division multiplexing (OFDM) systems with adaptive guard interval (GI) length is proposed. To estimate the CIR length and the noise variance, the different statistical characteristics of the additive noise and the mobile radio channels are exploited. This difference is due to the fact that the variance of the channel coefficients depends on the position within the CIR, whereas the noise variance of each estimated channel tap is equal. Moreover, the channel can vary rapidly, but its length changes more slowly than its coefficients. An auxiliary function is established to distinguish these characteristics. The CIR length and the noise variance are estimated by varying the parameters of this function. The proposed method provides reliable information of the estimated CIR length and the noise variance even at signal-to-noise ratio (SNR) of 0 dB. This information can be applied to an OFDM system with adaptive GI length, where the length of the GI is adapted to the current length of the CIR. The length of the GI can therefore be optimized. Consequently, the spectral efficiency of the system is increased.

Research Article


  1. GE Bottomley, J-C Chen, D Koilpillai, System and methods for selecting an appropriate detection technique in a radiocommunication system US patent 6333953B1, December 200

  2. JE Hudson, Communication system and methods of estimating channel impulse responses therein US patent 0043887 A1, March 200

  3. EG Larsson, G Liu, J Li, GB Giannakis, Joint symbol timing and channel estimation for OFDM based WLANs. IEEE Communications Letters 5(8), 325–327 (2001). Publisher Full Text OpenURL

  4. J-H Chen, Y Lee, Joint synchronization, channel length estimation, and channel estimation for the maximum likelihood sequence estimator for high speed wireless communications. Proceedings of the 56th IEEE Vehicular Technology Conference (VTC '02), September 2002, Vancouver, BC, Canada 3, 1535–1539

  5. PP Moghaddam, H Amindavar, RL Kirlin, A new time-delay estimation in multipath. IEEE Transactions on Signal Processing 51(5), 1129–1142 (2003). Publisher Full Text OpenURL

  6. Y Zhao, A Huang, A novel channel estimation method for OFDM mobile communication systems based on pilot signals and transform-domain processing. Proceedings of the 47th IEEE Vehicular Technology Conference (VTC '97), May 1997, Phoenix, Ariz, USA 3, 2089–2093

  7. H Akaike, A new look at the statistical model identification. IEEE Transactions on Automatic Control 19(6), 716–723 (1974). Publisher Full Text OpenURL

  8. P Höher, TCM on frequency-selective land-mobile fading channels. Proceedings of the 5th Tirrenia International Workshop on Digital Communications, September 1991, Tirrenia, Italy, 317–328

  9. C-S Yeh, Y Lin, Channel estimation using pilot tones in OFDM systems. IEEE Transactions on Broadcasting 45(4), 400–409 (1999). Publisher Full Text OpenURL

  10. J Medbo, P Schramm, Channel Model for HiperLAN/2 in Different Indoor Scenarios ETSIEPBRAN3ERI085B, March 199

  11. ETSI Technical Specification TS 101 475 V1.1.1 (2000-04) HIPERLAN Type 2; Physical (PHY) layer. 200

  12. A Papoulis, Probability, 3rd edn. (McGraw-Hill, New York, NY, USA, 1991)