Diversity with practical channel estimation

  • Authors:
  • W. M. Gifford;M. Z. Win;M. Chiani

  • Affiliations:
  • Lab. for Inf. & Decision Syst., Massachusetts Inst. of Technol., Cambridge, MA, USA;-;-

  • Venue:
  • IEEE Transactions on Wireless Communications
  • Year:
  • 2005

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Abstract

In this paper, we present a framework for evaluating the bit error probability of Nd-branch diversity combining in the presence of non-ideal channel estimates. The estimator structure presented is based on the maximum-likelihood (ML) estimate and arises naturally as the sample mean of Np pilot symbols. The framework presented requires only the evaluation of a single integral involving the moment generating function of the norm square of the channel-gain vector, and is applicable to channels with arbitrary distribution, including correlated fading. Our analytical results show that the practical ML channel estimator preserves the diversity order of an Nd-branch diversity system, contrary to conclusions in the literature based upon a model that assumes a fixed correlation between the channel and its estimate. Finally, we investigate the asymptotic signal-to-noise ratio penalty due to estimation error and reveal a surprising lack of dependence on the number of diversity branches.