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  • Research Article
  • Open Access

Rate and Power Allocation for Discrete-Rate Link Adaptation

  • 1Email author,
  • 1,
  • 1, 2,
  • 3,
  • 4,
  • 5 and
  • 6, 7
EURASIP Journal on Wireless Communications and Networking20082008:394124

  • Received: 17 July 2007
  • Accepted: 25 December 2007
  • Published:


Link adaptation, in particular adaptive coded modulation (ACM), is a promising tool for bandwidth-efficient transmission in a fading environment. The main motivation behind employing ACM schemes is to improve the spectral efficiency of wireless communication systems. In this paper, using a finite number of capacity achieving component codes, we propose new transmission schemes employing constant power transmission, as well as discrete- and continuous-power adaptation, for slowly varying flat-fading channels. We show that the proposed transmission schemes can achieve throughputs close to the Shannon limits of flat-fading channels using only a small number of codes. Specifically, using a fully discrete scheme with just four codes, each associated with four power levels, we achieve a spectral efficiency within 1 dB of the continuous-rate continuous-power Shannon capacity. Furthermore, when restricted to a fixed number of codes, the introduction of power adaptation has significant gains with respect to average spectral efficiency and probability of no transmission compared to a constant power scheme.


  • Power Transmission
  • Power Allocation
  • Spectral Efficiency
  • Transmission Scheme
  • Wireless Communication System

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Authors’ Affiliations

Department of Electronics and Telecommunications, Norwegian University of Science and Technology (NTNU), 7491 Trondheim, Norway
Honeywell Laboratories, Minneapolis, MN 55418, USA
Department of Electrical and Computer Engineering, Texas A&M University at Qatar, P.O. Box 23874, Doha, Qatar
Institut Eurécom, 06904 Sophia-Antipolis, France
Department of Informatics, University of Bergen, 5020 Bergen, Norway
Thrane & Thrane, 1375 Billingstad, Norway
University Graduate Center, 2027 Oslo, Norway


© Anders Gjendemsjø et al. 2008

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.