Field trials of DVB-T sensing for TV White Spaces

The use of TV White Spaces on a secondary, unlicensed basis has been of great interest recently in academia, industry and regulatory bodies worldwide. Central to this is the ability to sense incumbent TV signals (ATSC and DVB-T) at extremely low signal levels (-114 dBm to -120 dBm). These levels have been determined primarily through theoretical means, where worst-case interference situations have been considered with little or no probabilistic or measurement studies. While limited field measurements of ATSC sensing prototypes was part of the FCC rulemaking process, these tests were not used to determine appropriate sensing levels. No field testing of DVB-T sensing prototypes was done in Europe. In this paper we extend earlier work on algorithm development and laboratory testing for DVB-T sensing and present results obtained from field testing a prototype DVB-T sensor test bed using a hardware front-end followed by signal processing in software to show that the proposed level of -120 dBm may be too pessimistic: the sensor calibrated in a laboratory at about -115 dBm provided 100% detection of the main DVB-T transmitter for the area at all points in all test sites.