Primary Contour Prediction Based on Detailed Topographic Data and Its Impact on TV White Space Availability

摘要

Following the standard approach envisioned by the Federal Communication Commission (FCC), we consider database as a tool to plan the utilization of very high frequency/UHF spectrum by white space (WS) radios. Our approach, however, differs from the FCC one in the sense that the proposed geolocation database is not limited to process terrain information based on antenna height above average terrain (HAAT). Our primary contour prediction (PCP) algorithm processes detailed regional topographic data with the Fresnel diffraction theory while allowing flexibility in conservativeness to accommodate local regulations. This renders more realistic contour predictions in regions of rough terrain. Moreover, due to the current broadcast antenna height limitation of 200 m in existing propagation models, we revisit the work of Okumura et al. and derive a new model applicable to a broader antenna height range. Specifically, we utilize th order polynomials to fit Okumura curves in the least-square sense and obtain remarkable accuracy with low orders, i.e., . As a result, contours of broadcasters as high as 1000 m are easily predicted in regions ranging from quasi-flat to mountainous with the proposed geolocation database, which is composed of the novel yet simple propagation model and the PCP algorithm based on the diffraction theory. Finally, we perform an extensive analysis of TV WS (TVWS) spectrum availability in Japan based on NASA topography data, demographic information from the Statistic Bureau of Japan, and broadcaster-related information obtained from the Japanese Ministry of Communications. This analysis suggests that HAAT-based techniques should not be utilized in countries with rough terrain due to HAAT inherent lack of sensitivity to detailed topography, which hinde- s the potential of TVWS technology. We also computed the TVWS availability considering all (more than 2000!) transmitters, translators, and boosters across Japan and adjacent channel restrictions as required per regulations. We found that processing detailed topographic data by diffraction-based algorithms almost triple the expected TVWS bandwidth compared with HAAT-based techniques in this country.