ITU-R REPORT M.2147 PDF

Introduction

At the ITU World Radiocommunication Conference 2007 (WRC-07) amendments to the ITU Radio Regulations included revised provisions for the use of the band 108-117.975 MHz. The Radio Regulations as adopted at this conference stipulate:

"5.197A Additional allocation: the band 108-117.975 MHz is also allocated on a primary basis to the aeronautical mobile (R) service, limited to systems operating in accordance with recognized international aeronautical standards. Such use shall be in accordance with Resolution 413 (Rev.WRC-07). The use of the band 108-112 MHz by the aeronautical mobile (R) service shall be limited to systems composed of ground-based transmitters and associated receivers that provide navigational information in support of air navigation functions in accordance with recognized international aeronautical standards. (WRC-07)"

Although prior to WRC-07 all systems in the aeronautical mobile (R) service could use the band 108-112 MHz, detailed criteria that would in particular address the potential of interference from the AM(R)S into FM broadcasting receivers, had only been implemented for the ICAO-standard ground based augmentation system (GBAS) and as such would need to be developed. In addition, ICAO had expressed its concerns about airborne AM(R)S transmitters using the band 108-112 MHz because of the potential interference into the ILS-Localizer. With the view to avoid unnecessary compatibility issues between such AM(R)S and FM broadcasting, the band available for airborne AM(R)S transmitters was reduced to 112-117.975 MHz, thus creating a "guardband" of 4 MHz between the two services.

In ITU-R criteria have been established on the compatibility between FM broadcasting stations operating in the band around 87-108 MHz and aeronautical radionavigation systems (the instrument landing system (ILS), the VHF omnidirectional radio range (VOR) and the ICAO ground-based augmentation system (GBAS)) operating in the band 108-117.975 MHz. These criteria are contained in Recommendations ITU-R SM.1009-1 (ILS and VOR) and ITU-R M.1841¹ (GBAS).

Plans have been established to start using the band 112-117.975 MHz for VDL Mode 4 operating under the AM(R)S allocation. ICAO Standards and Recommended Practices have been approved in 2001. This Report addresses compatibility issues between FM broadcasting stations and the VDL Mode 4 system. This Report follows closely the principles described in Recommendation ITU-R M.1841 because the FM immunity criteria that have been developed for VDL Mode 4 are identical to those for GBAS. Definitions, references and methodologies used in this Report are as contained in Recommendation ITU-R M.1841.

Resolution 413 (Rev.WRC-07) stipulates, inter alia, that AM(R)S systems operating in the band 108-117.975 MHz shall ".... not cause harmful interference to stations operating in the bands allocated to the broadcasting service in the band 87-108 MHz ...". Furthermore, the ITU-R was invited to study any compatibility issues between the broadcasting service and the AM(R)S that may arise from the introduction of AM(R)S systems in the band 112-117.975 MHz.

The analysis below examines the interference mechanisms for type A1, A2, B1 and B2 interference, as detailed in Recommendation ITU-R M.1841.

¹ 2007 version of Recommendation ITU-R M.1841 is used as a reference for purpose of this Report.