Adaptive Joint Power and Bandwidth Control for Spectrum Sharing Systems

Two adaptive joint power and bandwidth control schemes are proposed for multiple secondary user (SU) transmitters to optimize the spectral efficiency in cognitive radio transmission through spectrum sharing. By exploiting agile bandwidth transmission strategy for cognitive radio users, we present a unified solution to two problems of joint power/rate control and joint power/bandwidth control in dynamic spectrum allocation. Our main objective is to maximize the average spectral efficiency of the commonly in-used portion of the frequency band, subject to the tolerable interference limit at the primary user (PU) that is present. The proposed schemes are applicable to many scenarios, for examples, where two or more SUs are accessing the same frequency band with equal right, or where two or more SUs are accessing the frequency spectrum used by a PU who has a higher priority. Simulations results are presented to show that the proposed suboptimal algorithm also achieves near optimal spectral efficiency.