Open Access

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

  • VanDuc Nguyen1Email author,
  • Hans-Peter Kuchenbecker2,
  • Harald Haas3,
  • Kyandoghere Kyamakya4 and
  • Guillaume Gelle5
EURASIP Journal on Wireless Communications and Networking20072007:024342

Received: 5 October 2005

Accepted: 14 November 2006

Published: 21 February 2007


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.


Authors’ Affiliations

Department of Communication Engineering, Faculty of Electronics and Telecommunications, Hanoi University of Technology
Institut für Allgemeine Nachrichtentechnik, Universität Hannover
School of Engineering and Science, International University Bremen
Department of Informatics-Systems, Alpen Adria University Klagenfurt
CReSTIC-DeCom, University of Reims Champagne-Ardenne


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© Van Duc Nguyen et al. 2007

This article is published under license to BioMed Central Ltd. 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.