Near-optimal input distributions in fading channels with large coherent dimension

Xinzhou Wu, R. Srikant

Research output: Contribution to journalConference articlepeer-review


In an earlier paper, we investigated the fundamental tradeoff between bandwidth and rate for wideband additive Gaussian channels, when there is a constraint in the error exponent. In this paper, we extend these results to fading channels. Specifically, we consider fading channels with large coherent dimension D, which is the defined to be the product of coherent time and coherent bandwidth. We consider the behavior of Rz-(1/D) which is the maximum rate at which one can communicate when the coherent dimension is D and the error exponent is constrained to be at least equal to z. We calculate two quantities: Rz(0) and Rz(0), which together partially characterize the behavior of RZ(1/D) when D is large. We show that QPSK is near-optimal for fading channels with large coherent dimension, in the sense that both Rz (0) and Rz (0) can be achieved.

Original languageEnglish (US)
Pages (from-to)557-561
Number of pages5
JournalIEEE International Conference on Communications
StatePublished - 2004
Event2004 IEEE International Conference on Communications - Paris, France
Duration: Jun 20 2004Jun 24 2004

ASJC Scopus subject areas

  • Computer Networks and Communications
  • Electrical and Electronic Engineering


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