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International Journal of Digital Multimedia Broadcasting
Volume 2010, Article ID 823494, 9 pages
Research Article

Opportunistic Communication (Cognitive Radio) over Primary Discarded Subchannels by Applying a Double Power Distribution

Signal Theory and Communications Department, Technical University of Catalonia, Building D4 Campus Nord, Jordi Girona, 1-3, 08034 Barcelona, Spain

Received 31 October 2009; Revised 2 February 2010; Accepted 12 May 2010

Academic Editor: Fred Daneshgaran

Copyright © 2010 G. A. Medina-Acosta and José A. Delgado-Penín. 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.


This paper proposes the establishment of a simultaneous cognitive radio communication based on a subdistribution of power made over unselected subchannels which were discarded by the primary user through an initial optimal power allotment. The aim of this work is to show the possibility of introducing an opportunistic communication into a licensed transmission where the total power constraint is shared. The analysis of the proposed transmission scheme was performed by considering 128 and 2048 independent subchannels affected by Rayleigh fading, over 10,000 channel realizations, and three different signal-to-noise ratios (8  d B , 16  d B , and 24  d B ). From the system evaluation it was possible to find the optimal power allotment for the primary user, the subdistribution of power for the secondary user, as well as the attenuation and the capacity per subchannel for every channel realization. Moreover, the PDF and CDF of the total obtained capacities, as well as the generation of empirical capacity regions, were estimated as complementary results.