Reliable power control for secondary users based on distributed measurements

An important aspect of spectrum sharing is reliable protection of licensed, primary, users from interference by unlicensed, secondary, users. In this paper we investigate the reliability of the iterative power adjustment algorithm proposed by Pollin, Adams and Bahai (2008). The goal of this transmission power control algorithm is to allow a static secondary transmitter to maximize its power without interfering with primary users. A distributed flooding algorithm is used to detect primary users and estimate the distance to the primary propagation contour. The secondary transmitter makes a local channel estimation with a moving least squares algorithm to average out noise. The metric used to estimate interference is the propagation contour-contour distance between the secondary and primary transmitters. In our first contribution we investigate the reliability of this metric by computing the location probability, a new FCC proposed metric for configuring Digital Terrestrial Television networks. We show that the propagation contour-contour distance is correlated with the location probability. In a second contribution we make the flooding algorithm more cost efficient by reducing communication. We then study the influence of the number of flooding messages on the performance of the iterative power adjustment algorithm in terms of location probability and number of iterations.