Multilevel Protection to Broadcaster Contour and Its Impact on TV White Space Availability

In light of recent regulations from the Federal Communications Commission (FCC) governing the very-high-frequency/ultrahigh-frequency band sharing, we consider the database as a tool to plan the utilization of this spectrum by unlicensed wireless devices. Our approach, however, differs from that adopted by the FCC in the sense that it exploits the ability that white space (WS) devices have in controlling their effective isotropic radiated power through the transmit power control technique when concomitantly operating in a cochannel or in an adjacent channel to a TV station. We derive equations for the expected interference level generated by WS devices with antenna heights ranging from a few meters (portable devices) up to a 1000 m (fixed devices) based on very recent TV white space (TVWS) propagation literature and regulatory requirements. Additionally, we also provide exact and numerical methods to calculate the critical distance that prevents interference to primary contours, thus enabling fast identification of regions where operation is harmless to incumbents in the presence of shadowing and multipath fading. These equations reveal the intrinsic relationship between system design parameters, environmental parameters, and country regulations with TVWS availability. Finally, we provide an analysis that indicates notable enhancements in the expected TVWS availability through the use of a multilevel method while obtaining the same desirable degree of protection required by the current FCC regulation based on the single-level methodology. The analysis is divided in two parts: theoretical evaluations to obtain insights into the potential of multilevel protection in recovering TVWS-less regions from a single exclusion zone and extensive computations to obtain the expected TVWS availability yielded by both protection methodologies and primary-contour determination techniques across the Japanese territory. Specifically, multilevel protection is found to have the effect of doubling the TVWS bandwidth, as compared with single-level protection. On the other hand, diffraction methods used to determine the primary contour nearly triples the bandwidth, as compared with the height above average terrain (HAAT) technique. The combined effect of multilevel protection and diffraction-based primary contours is TVWS availability on 98.76% of the Japanese territory with a bandwidth expansion six times of that inherent to single-level protection and HAAT-based contours.