Interference Assessment and Development of Interference Protection Criteria to Protect Public Safety Operations and Enable Spectrum Sharing with NTSC and DTV Broadcasting in TV Channels 60‑69 (746‑806 MHz)
Table of ContentsExecutive Summary
- Interference Scenarios
- Land Mobile and Television Parameters
- Co-frequency Sharing
- Adjacent Channel
Jean Edmonds Tower N, 19th Floor
300 Slater Street, Room 1912A
Lapp-Hancock Associates Limited
280 Albert Street, Suite 900
Ottawa, Ontario, Canada K1P 5G8
Points of view or opinions expressed in this document
are those of the authors and do not necessarily represent
the views of Industry Canada.
The objective of the study is to assess the potential for interference from television transmissions to mobile public safety radio systems operating in spectrum reallocated from TV.
In Canada Gazette Notice DGTP-004-01, Industry Canada proposed the introduction of the mobile service on a co-primary basis with the broadcasting service in the frequency band 746–806 MHz. This proposal also indicated that although the Transition Allotment Plan required use of allotments for DTV in channels 60–69, a modest amount of spectrum may still be made available to meet the pressing needs of public safety.
Subsequently, an engineering assessment on which portions of television channels 63–64 and 68–69 could be used for public safety has been completed, and channels 63 and 68 have been selected as the channels least impacted by the Transition Allotment Plan. Assessment of how such use could be effectively implemented is now required to enable mobile public safety services to share spectrum with broadcasting services without receiving harmful interference from NTSC (analogue) and DTV broadcasting facilities.
With the determination by Industry Canada that channels 63 and 68 would be selected for reallocation to land mobile, a number of scenarios require investigation:
- Co-channel interference
- Analogue NTSC to narrowband public safety
- Analogue NTSC to wideband public safety
- DTV to narrowband public safety
- DTV to wideband public safety
- Adjacent channel interference
- Analogue NTSC to mobile reception
- Analogue NTSC to base reception
- DTV to mobile reception
- DTV to base reception
Land mobile system parameters were derived from those of the closest bands (800 MHz) in Canada/United States border sharing arrangements and from Industry Canada Standard Radio System Plans, along with Telecommunications Executive Summary (Report. 001/03): Industry Canada: Interference Assessment Lapp-Hancock Associates Limited Industry Association standards. Similarly, television parameters were derived from Canada/U.S. border arrangements, Broadcasting Procedures and Rules, and documentation from the Advanced Television Systems Committee. Three specific television classes were selected for the study:
- NTSC Class C, ERP 1 Megawatt
- DTV Class VL, ERP 250 kW
- DTV Class C, ERP 15 kW.
It may be concluded that co-channel operation of television and public safety land mobile would require significant distance separations between TV and land mobile. These distances would be of the order of 200–260 km for NTSC base stations, however, assignment of land mobile frequencies near the vision and sound carriers should be avoided. For DTV, comparable base station separations would be of the order of 300 km for class VL and 230 km for class C. Since it is intended to clear channel 63 and 68 allotments from the TV Transition Allotment Plan, it would appear unnecessary to provide for co-channel protection, other than in the border area.
It is recommended that no provision be made for co-channel protection in the domestic rules.
For adjacent channel operation sufficient protection to mobile stations would be available through base station co-location for either NTSC or DTV. Further, mobile operation anywhere within the television service area would not be a problem for base station reception within the TV service area. Base station transmissions could, however, potentially create interference to reception of adjacent channel television within a radius of the base station site.
It is recommended that co-location of base stations with TV transmitters be considered in cities having channel 62 or 64 allotments, in order to minimize the potential of interference to either land mobile (mobile stations) or TV reception.
Should co-location not be possible, public safety operation would still be possible within the TV station's grade B service contour. Protection distance would be approximately 56 km with respect to an NTSC TV station, and 71 km and 47 km for DTV class VL and C. Use of the FCC tight mask would rapidly reduce the separation distance with increase in frequency separation. Again, base station transmissions could create interference to reception of adjacent channel television.
The mandatory use of the FCC tight mask is recommended.
- Date modified: