Estimating Protection Distances in Spectrum Sharing Systems

In this paper, we analyze spectrum sharing on broadcast primary frequency bands. We employ protection regions (with size defined by protection distances) around the broadcast transmitter service contours for meeting the primary system outage constraints, hence implementing the Federal Communications Commission´s regulations. For the unlicensed nodes distributed in a Poisson Point Process, it is shown that exact protection distances cannot be analytically determined. In this paper, tools for estimating the protection distances are presented. Previously we have shown that combinations of lognormal and shifted-lognormal distributions always overestimate protection distances, hence guaranteeing primary system protection. In this paper, we show that combinations of gamma and shifted-lognormal distributions as well as the Edgeworth expansion also guarantee primary system protection. A comparative study of the three techniques and their comparison with the protection distances obtained from the Markov and Chebychev inequality is performed. It is shown that combinations of lognormal and shifted-lognormal distributions provide the most efficient spectrum utilization by the unlicensed system.