scope:

The present document provides a characterization of antenna performances for earth stations on mobile platforms. It identifies the technologies and antenna types used in such systems, which may not have the same performance characteristics considered when developing the existing ETSI standards for VSATs.

Antennas used on mobile platforms are typically smaller and have radiation patterns that may have variable symmetry and/or variable geographic skew angles toward the satellite. These types of antennas are typically used in low profile antennas or other special applications. Their radiating patterns may show non-conformances with regard to the ETSI off-axis EIRP density mask. 

The present document proposes a method to cope with this non-conformances issue, called the "non-conformance-area" (NCA) method. The method relies on a geometrical mathematical object, called a NCA, defined as follows:

• A "non-conformance-area" (NCA) is an area of preferably simple geometric shape defined on the antenna radiating pattern that identifies the set of directions where the ETSI mask is exceeded, associated with an indicative level of severity in the perspective of a further interference analysis.

As far as 3D geometry in space is concerned, the NCA method is an extension of the ETSI TR 102 375 [i.6] report that "provides guidelines for determining the parts of the satellite earth station antenna radiation patterns concerned by the geostationary satellite orbit protection".

The rationale underlying the NCA method is:

1) As long as there is no victim system in the directions of a NCA, there is no possible harmful interference occurrence for that directions.

2) When a victim system happens to be in the directions of a NCA, a possible interference event occurs in the scope of a non-conformance to the ETSI mask. This event is called a "hit".

3) A coarse level of severity is associated by analysis to each "hit".

4) Statistics are performed about the occurences of "hits" during operations, providing with a comprehensive assessment of the hit occurences issue.

The NCA method may support a rationale as suggested by FCC 47 CFR 25.138 (b) [i.1] as stated hereafter:

• "(b) Each applicant for earth station license(s) that proposes levels in excess of those defined in paragraph (a) of this section shall submit link budget analyses of the operations proposed along with a detailed written explanation of how each uplink and each transmitted satellite carrier density figure is derived. Applicants shall also submit a narrative summary which must indicate whether there are margin shortfalls in any of the current baseline services as a result of the addition of the applicant's higher power service, and if so, how the applicant intends to resolve those margin short falls. Applicants shall certify that all potentially affected parties (i.e. those GSO FSS satellite networks that are 2, 4, and 6° apart) acknowledge and do not object to the use of the applicant's higher power densities."

The NCA method may also support a rationale as suggested by FCC 47 CFR 25.227 (b)(2) [i.2].