Distributed power allocation for rate maximization in cognitive radio networks with horizontal spectrum sharing

Cognitive radio (CR) is an emerging concept that aims at enabling more efficient utilization of the frequency spectrum in future generations of wireless networks through the reuse of licensed frequency bands. Specifically, in CR networks, unlicensed transmitters are allowed to access licensed frequencies as secondary users (SU) if the primary users (PU) holding the spectrum license are not active. When multiple SUs with no central control or coordination are trying to access a band of licensed frequencies that is not actively used by PUs, the available spectrum is shared in a horizontal manner, where all SUs compete for spectrum access. In such a scenario, greedy approaches lead in general to increased interference in the system, which negatively affects the transmission rates for all users. To alleviate this problem, in this paper we propose a new approach for distributed allocation of SU transmit powers is based on avoiding interference while seeking to maximize SU transmission rates. The proposed approach is illustrated with numerical results obtained from simulation, which show that the resulting power allocation for SUs implies a more efficient use of the available spectrum than alternative approaches available in the literature.