| Summary: | In this Letter, the authors propose a technique that allows a secondary user (SU) to reuse the spectrum allocated to TV broadcast system. The approach is based on protection view point and an SU is allowed to transmit outside the noise limited contour (grade B contour) with additional protection margin. An algorithm was developed that predicts the grade B contour and makes a decision on the availability of the spectrum. The keep-out distance was obtained using the existing path loss models and a model developed based on field strength measurements conducted in the very high frequency (VHF) and ultra high frequency (UHF) broadcast frequencies. Results of simulation indicate that the extra margin does not follow a linear curve as expected, but strongly depends on the operating frequency and terrain profile of the area. In addition, the measured model's prediction deviates significantly from the other models' prediction.
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