Estimation of Interference-Free Transmit Power for Opportunistic Spectrum Access

We consider a scenario in which frequency agile radios opportunistically share a fixed spectrum resource with a set of primary nodes. We develop a collaborative scheme for frequency agile radios to estimate the maximum power at which they can transmit, without causing harmful interference to the primary receivers. The proposed scheme relies on signal strength measurements, which are used to localize primary transmitters. An approximation to the maximum interference-free transmit power is derived using the Cramer-Rao lower bound on localization accuracy. We present numerical results to demonstrate the effectiveness of the proposed scheme under a variety of scenarios.