In this article, the proposal to establish a simultaneous cognitive radio communication based on a subdistribution of power made over discovered unselected subchannels identified by an initially optimal power allotment for a primary user is shown. The aim of this work is to show the possibility of introducing a low priority (secondary) communication into a single user (licensed) transmission where the total power constraint is shared. The analysis of the proposed transmission scheme was performed by considering eight independent subchannels affected by Rayleigh fading, over 2000 channel realizations, and three different signal-to-noise ratios (4dB, 8dB, and 15dB). 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 of the total capacities and their averages were obtained as a complementary result.

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