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  • Research Article
  • Open Access

Practical Approaches to Adaptive Resource Allocation in OFDM Systems

EURASIP Journal on Wireless Communications and Networking20072008:160307

  • Received: 30 April 2007
  • Accepted: 28 September 2007
  • Published:


Whenever a communication system operates in a time-frequency dispersive radio channel, the link adaptation provides a benefit in terms of any system performance metric by employing time, frequency, and, in case of multiple users, multiuser diversities. With respect to an orthogonal frequency division multiplexing (OFDM) system, link adaptation includes bit, power, and subcarrier allocations. While the well-known water-filling principle provides the optimal solution for both margin-maximization and rate-maximization problems, implementation complexity often makes difficult its application in practical systems. This paper presents a few suboptimal (low-complexity) adaptive loading algorithms for both single- and multiuser OFDM systems. We show that the single-user system performance can be improved by suitable power loading and an algorithm based on the incomplete channel state information is derived. At the same time, the power loading in a multiuser system only slightly affects performance while the initial subcarrier allocation has a rather big impact. A number of subcarrier allocation algorithms are discussed and the best one is derived on the basis of the order statistics theory.


  • Orthogonal Frequency Division Multiplex
  • Channel State Information
  • Orthogonal Frequency Division Multiplex System
  • Allocation Algorithm
  • Power Loading

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Authors’ Affiliations

Department of Electrical and Communications Engineering, Helsinki University of Technology, P.O. Box 3000, TKK, 02015, Finland


© N. Y. Ermolova and B. Makarevitch. 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.