Open Access

Rate and Power Allocation for Discrete-Rate Link Adaptation

  • Anders Gjendemsjø1Email author,
  • Geir E. Øien1,
  • Henrik Holm1, 2,
  • Mohamed-Slim Alouini3,
  • David Gesbert4,
  • Kjell Hole5 and
  • Pål Orten6, 7
EURASIP Journal on Wireless Communications and Networking20082008:394124

Received: 17 July 2007

Accepted: 25 December 2007

Published: 9 January 2008


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.

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Authors’ Affiliations

Department of Electronics and Telecommunications, Norwegian University of Science and Technology (NTNU)
Honeywell Laboratories
Department of Electrical and Computer Engineering, Texas A&M University at Qatar
Institut Eurécom
Department of Informatics, University of Bergen
Thrane & Thrane
University Graduate Center


© 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.