Determination of Detection Thresholds to Allow Safe Operation of Television Band "White Space" Devices

The purpose of this study is to determine a range of detection thresholds at which new dynamic spectrum access (DSA) devices can safely operate in unoccupied spectrum allocated to terrestrial television (TV) broadcasting and other services (i.e., the TV "white spaces"), without causing harmful interference to other authorized operations, which include digital and analog TV stations, wireless microphones and other services. Spectrum sensing data were collected at six different locations in Northern Virginia that were strategically chosen because they were within, outside and near the edges of the predicted service contours of digital TV stations serving the Washington, D.C. and Baltimore, MD metropolitan areas. We used a pair of DSA devices that jointly decide if a channel can be used or not. This emulates how SSC's and other DSA devices operate. The joint decision logic mitigates the propagation shadowing and hidden node problem. The separation between the DSA devices was less than approximately 10 km, which corresponds to the link range of a 10 W 802.16-based transmitter. The DSA detectors used a high sensitivity detector that is able to detect the ATSC pilot down to a -140 dBm level (ATSC signal power level of -128 dBm). The detector is not noise limited. "False alarms" are caused by detection of distant TV transmitters when the DSA system is located outside the Grade B contour. Based on analysis results from data recorded from six independent locations in Northern Virginia and 13 ATSC channels.