Initial spectrum access control with QoS protection for active users in cognitive wireless networks

In this paper, an initial spectrum access control algorithm for cognitive wireless networks was studied. The objective was to maximize the number of admitted secondary users (SUs) under the constraints of interference temperature at multiple measurement points (MPs), while providing active SUs' QoS protection (AQP). Here, AQP means that the signal-to-interference-plus-noise ratios (SINRs) of all active SUs will not fluctuate below some predefined thresholds during a new SU's initial spectrum access process. To this end, we proposed a new distributive power control algorithm in conjunction with a simple alarm mechanism that ensures the interference temperatures at multiple MPs to be always below their thresholds during the initial spectrum access process. Then, two realizations of the spectrum access algorithms, namely, D-AQP and C-AQP, according to whether the MPs can act as local controllers or not, were presented. In the D-AQP algorithm, each SU updates its transmit power distributively based on the local information including the current SINR, the QoS requirement, and the indicator from the MPs so that the resultant SINRs of the active SUs are able to stay above the predefined thresholds. Whereas in the C-AQP algorithm, apart from the same procedure as mentioned, each MP is supposed to be able to decide which new SU should quit the initial spectrum access process so as to protect the communication quality of the primary system. Finally, the performances of the proposed algorithms were validated by extensive simulations. Copyright (C) 2011 John Wiley & Sons, Ltd.