Keep-out distance of the IEEE 802.11af system from digital TV broadcast contour

Congestion in the Industrial, Scientific, and Medical (ISM) frequency band limits the expansion of the IEEE 802.11 Wireless Local Area Network (WLAN). Recently, due to the `digital switchover' from analog to digital TV (DTV) broadcasting, a sizeable amount of bandwidth have been freed up in the conventional TV bands, resulting in the availability of TV white space (TVWS). The IEEE 802.11af is a standard for the WLAN technology that operates at the TVWS spectrum. TVWS operation must not cause harmful interference to the incumbent DTV service. This paper provides a method of computing the keep-out distance required between an IEEE 802.11af device and the DTV service contour, in order to keep the interference to a harmless level. The ITU-R P.1411-7 propagation model is used in the calculation. Four different DTV services are considered: Advanced Television Systems Committee (ATSC), Digital Video Broadcasting - Terrestrial (DVB-T), Integrated Services Digital Broadcasting - Terrestrial (ISDB-T), and Digital Terrestrial Multimedia Broadcasting (DTMB). The calculation results reveal that under many circumstances, allocating keep-out distance of 1 to 2.5 km is sufficient for the protection of DTV service.