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  • Research Article
  • Open Access

Cognitive Cooperation for the Downlink of Frequency Reuse Small Cells

  • 1,
  • 2Email author,
  • 1 and
  • 3
EURASIP Journal on Advances in Signal Processing20102011:525271

  • Received: 1 June 2010
  • Accepted: 16 November 2010
  • Published:


We develop a cooperative diversity protocol coded over space, time, and frequency to achieve improved quality of service for mobile users in the downlink of small-cell frequency reuse networks. The proposed protocol, called cooperative frequency reuse (CFR), leverages the cellular frequency reuse concept to create space and frequency diversity among pairs of adjacent base stations. The CFR protocol is compatible with the half-duplex mode and is distributed in the sense that each base station acts in autonomy, without the need of a centralized entity. It is implemented in two phases. During the first phase, each base station independently serves its own users on its dedicated frequency band. It simultaneously listens to the symbols transmitted by neighboring base stations. Cognitive cooperation is introduced in the second phase, where each base station transmits on two frequency bands to the scheduled users in both base stations, by means of an appropriately chosen distributed space time code based on the Golden code. We analyze and discuss the performance of the proposed protocol in terms of bit error rate, probability of outage, and ergodic sum rate under different scenarios. Simulation results show that the proposed protocol yields considerable improvement over direct transmission frequency reuse strategies.


  • Space Time Code
  • Frequency Reuse
  • Cooperative Diversity
  • Distribute Space Time
  • Reuse Strategy

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Authors’ Affiliations

Wireless Networking and Communications Group, Department of Electrical and Computer Engineering, The University of Texas at Austin, 1 University Station C0803, Austin, TX 78712-0240, USA
IEMN/DOAE, UMR 8520, University Lille Nord de France, 59000 Lille, France
Ecole Superieure d'Electrecite (SUPELEC), Alcatel-Lucent Chair on Flexible Radios, 3 rue Joliot-Curie, 91192 Gif sur Yvette Cedex, France


© Salam Akoum et al. 2011

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.