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ACP-WGF24/WP-xx
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International Civil Aviation Organization
WORKING PAPER / ACP-WGW24/WP-07
21 March 2011

AERONAUTICAL COMMUNICATIONS PANEL (ACP)

24th MEETING OF WORKING GROUP F

Paris,France 21 March - 25 March 2011

Agenda Item x:

Radio Altimeter band issue

(Presented by Eric Allaix)

SUMMARY
At the last WGF in Cairo, it was mentioned that portions of the band 4200-4400MHz has been identified as a potential candidate band for accommodation wireless broadband applications. This working paper provides measurement of one of a broadly deployed radio altimeter.
ACTION
To take into account the material given in this working paper in the future studies related to this issue.

1Introduction

During last WGF meeting in Cairo, an information paper informed WG-F members that the National Telecommunication and Information Administration (NTIA) will collaborate with the Federal Communications Commission (FCC) to “make available a total of 500 MHz of Federal and non-federal spectrum over the next 10 years, suitable for both mobile and fixed wireless broadband use.

In order to satisfy this directive, a number of frequency bands are being studied. These studies will determine current use of those bands in the U.S. and whether portions (or all) of them can be re-allocated to support wireless broadband applications.

Of particular interest to aviation is consideration of whether portions of the 4200-4400 MHz band (currently allocated to the aeronautical radionavigation service and, according to footnote RR N° 5.438, exclusively reserved for radio altimeters installed on board aircraft and associated transponders on the ground), can be used. NTIA has initially identified the 4 200-4 220 MHz and 4 380-4 400 MHz bands, the upper and lower 20 MHz segments of the current 4 200-4 400 MHz aeronautical radionavigation service (ARNS) band reserved on a worldwide basis “exclusively for radio altimeters based on board aircraft and for the associated transponders on the ground”.

2 Radio altimeter characteristics

Figure 1 below gives an example of measured emission frequency response. It corresponds to a broadly deployed radio altimeter taking into account all operating conditions (temperature, vibrations …).

It is also indicated in figure 1 the spurious domain emission limits determined by ITU-R Recommendation SM.329– Category A for low power device radio equipment. It is then clearly shown that the emission characteristics for radio altimeters comply with this recommendation.

Figure 1

Example of radio altimeter emission frequency response

This figure also shows that the radio altimeter occupied bandwidth is not only the 4220 to 4380 MHz frequency band but covers practically all the allocated 4200-4400 MHz band.

3 ACTION BY THE MEETING

The ACP WGF members are invited to take into accounttheinformationprovidedinthispaperanduse itinfuture studiestoassessthelevelof interference aspotential newusers ofthe band4200-4400MHzcouldcausetothe radio altimeter systems.