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  • Research Article
  • Open Access

The Extended-Window Channel Estimator for Iterative Channel-and-Symbol Estimation

EURASIP Journal on Wireless Communications and Networking20052005:349390

  • Received: 29 April 2004
  • Published:


The application of the expectation-maximization (EM) algorithm to channel estimation results in a well-known iterative channel-and-symbol estimator (ICSE). The EM-ICSE iterates between a symbol estimator based on the forward-backward recursion (BCJR equalizer) and a channel estimator, and may provide approximate maximum-likelihood blind or semiblind channel estimates. Nevertheless, the EM-ICSE has high complexity, and it is prone to misconvergence. In this paper, we propose the extended-window (EW) estimator, a novel channel estimator for ICSE that can be used with any soft-output symbol estimator. Therefore, the symbol estimator may be chosen according to performance or complexity specifications. We show that the EW-ICSE, an ICSE that uses the EW estimator and the BCJR equalizer, is less complex and less susceptible to misconvergence than the EM-ICSE. Simulation results reveal that the EW-ICSE may converge faster than the EM-ICSE.


  • blind channel estimation
  • EM algorithm
  • maximum-likelihood estimation
  • iterative systems

Authors’ Affiliations

DSPCom, DECOM, FEEC, University of Campinas (UNICAMP), 400 Albert Einstein Avenue, Sao Paulo, 13083-970 Campinas, Brazil
School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, GA 30332-0250, USA