EPFD limits in Article 22 of the Radio Regualtions were established to enable protection of geostationary satellite networks (GSO) in Fixed-Satellite and Broadcasting-Satellite services from potential interference from non-geostationary satellite systems using different types orbits (LEO, MEO, HEO) operating in the same frequency bands in Fixed-Satellite service (non-GSO FSS).
These limits also referred to as hard limits allow enable non-GSO FSS systems to share frequencies with and protect GSO systems without requiring individual coordination with every GSO network worldwide.

Equivalent power-flux density (EPFD) takes into account the aggregate of the emissions from all non-GSO satellites in the direction of any GSO earth station, taking into account the GSO antenna directivity.

That is, when an antenna receives power, within its reference bandwidth, simultaneously from transmitters at various distances, in various directions and at various levels of incident pfd, the epfd is equivalent to the pfd which, if received from a single transmitter in the far field of the antenna in the direction of maximum gain, would produce the same power at the input of the receiver as is actually received from the aggregate of the various transmitters. This concept allows very limited knowledge of parameters of receiving systems. In fact, only reference antenna pattern, antenna size and associated maximum antenna gain are needed to characterize interference for the specific class of receiving system, i.e. Article 22 contains limit masks for a number receiving earth station configurations including antenna size ranging from 30 cm to 5 metres and up to 15 metres for the special case in the band 3 700-4 200 MHz.

Moreover, EPFD limits in Article 22 consider radiation of a non-GSO space system as a whole as compared to power-flux density limits (PFD) in Article 21 where PFD-level is calculated from a single space station and compared with an applicable limit.

Most of the non-GSO FSS systems have a large number of the satellites ranging from tens to several thousands. Even within one single satellite system several satellites could transmit simultaneously to one particular geographical area. This situation leads to a requirement to consider in calculating interference from non-GSO network to other fixed station on Earth or GSO that:

• We do not have any information in advance on the location of the interfering stations
• Due to the constant movement of the interfering source in relation to a fixed receiving station, the statistical properties of the interference should be considered
• There could be several interfering stations transmitting simultaneously thus increasing the aggregate interference level.

These factors require complex calculation methodology. Moreover, such methodology should be agreed by everyone to provide the confidence in the results.

This methodology is developed within Recommendation ITU-R S.1503. EPFD examination software implements this methodology.

A non-GSO system is subject to Article 22 limits if:

• It has the Earth as a reference body (e.g. orbiting Earth)
• It is to be operated in Fixed-Satellite service or associated space-operation functions in any of the frequency bands 3 700 – 4 200 MHz (space-to-Earth), 10.7-12.75 GHz (space-to-Earth), 17.8-18.6 GHz (space-to-Earth), 19.7-20.2 GHz (space-to-Earth), 5 925-6 725 MHz (Earth-to-space), 12.5-13.25 GHz (Earth-to-space), 13.75-14.5 GHz (Earth-to-space), 17.3-18.1 GHz (Earth-to-space), 27.5-28.6 GHz (Earth-to-space), 29.5-30 GHz (Earth-to-space).

Recommendation ITU-R S. 1503 provides a functional description of the software for use by the Radiocommunication Bureau of ITU to conduct examination of non-GSO FSS system submissions for their compliance with the “validation” limits specified in the Radio Regulations.

This recommendation contains detailed description of the input for calculating epfd limits and coordination triggers contained in Article 22 and Appendix 5 of the Radio Regulations.

Currently, there are 3 revisions of this Recommendation (S.1503-1, S.1503-2, S.1503-3).

Existing EPFD validation software implements Revision 2 of this Recommendation.

EPFD limits have been established by WRCs based on the systems under development at the Conference for the concerned bands.

In the frequency bands were no EPFD limits exists consultation process or coordination should be effected between GSO and non-GSO in application of Section I or Section II of Article 9 depending on the case. With respect to FSS and BSS GSO. 

EPFD limits in article 22 are applied to a non-GSO system which may contain a single satellite or many satellites forming constellation.

Administration can initiate coordination discussion whenever API or CR/C depending on the case is published. No. 22.2 applies between FSS/BSS GSO and non-GSO.

There is no contradiction. The right of administration is conditioned by the provisions of the RR and the status of its assignment is derived from the application of the procedure in the RR No. 22.2 is an additional measure to provide protection to GSO.
RR No. 22.2 deals with unacceptable level of interference. Such a level is subject to an agreement between the administrations concerned. Since the level of unacceptable interference is unknown to the Bureau, the Bureau is not dealing with its verification. However, there are cases of operational EPFD limits in Article 22 which indicate conditions of compliance with No.22.2 (see No. 22.5I), but this is verified by administrations concerned at operational stage of non-GSO.

When submitting the data required for Article 22 EPFD-limits validation to ITU it is important to:

1. Make sure the data is complete and all required elements are present.
2. Data is validated before submission to ITU. Please use both tools EPFD-T and EPFD-A and make sure that all results are ‘PASS’.

In case you need any assistance please don’t hesitate to contact BR

Radio Regulations Appendix 4 contains the list of mandatory data elements required for submission of information (either for advance publication, for coordination or for notification). In case a reference is made in Appendix 4 that a data element is required in case the space station is subject to provisions of Article 22 (Nos. 22.5C, 22.5D, 22.5F), such data element is mandatory for submission.

These additional data elements will be used in EPFD validation software to define non-GSO operating scenario. Because of the complex configurations of different non-GSO constellations it is difficult to simulate exact traffic configurations and transmitting parameters of the systems without providing excessive number of additional information. For that purpose, Recommendation ITU-R S.1503-2 establishes a concept of a mask for pfd/e.i.r.p. produced by interfering non-GSO network stations. The mask would account for all the features of specific non-GSO systems arrangements.

PFD masks define an envelope of the power radiated by the non‑GSO space stations taking into account different beam steering and/or switching strategy, power control due to specific service latitude or decrease sidelobe radiation towards any potential GSO victim receiver communicating with GSO space station located anywhere on GSO visible arc.

Similarly, EIRP-mask define an envelope of radiation of non-GSO earth station which would basically correspond to earth station antenna pattern and transmitted power which may be changing with the latitude of earth station.

There is also an additional type of EIRP-mask defining an envelope of transmission from non-GSO space station towards GSO-arc which required in the frequency bands where potential victim GSO link may operate in Earth-to-space direction (such as 17.8-18.4 GHz where non-GSO and GSO links may operate in opposite direction).

These masks may contain very large amount of data. In order for administrations to submit the mask data electronically and for the EPFD software tool to use the submitted data directly the Bureau has developed an XML-format for the pfd and e.i.r.p. masks (link).

Recommendation ITU-R S. 1503 (Part C) provides details on procedure to create these masks.

These masks may contain very large amount of data. In order for administrations to submit the mask data electronically and for the EPFD software tool to use the submitted data directly the Bureau has developed an XML-format for the pfd and e.i.r.p. masks.

It should be noted that EPFD validation software does not contain functionality to create these masks. It is a sole responsibility of a notifying administration to create masks. Administration may use its own proprietary software (such as interference simulation software) to create masks.

No, only one pfd (or e.i.r.p.) mask shall be provided for specific orbital plane(s) (or satellites) per frequency band.

In accordance with No. 22.5C and No. 22.5D:

 –            a single EIRP mask shall be provided for a frequency range considering the emissions from all earth stations (various antenna sizes, antenna patterns, tracking strategies, etc.) and

–             a single PFD mask shall be provided defining maximum power flux-density generated by any space station for all conditions and for all methods of modulation.  

Multiple EIRP and/or PFD masks for the same frequency range are receivable only if they apply to different orbital configurations or different satellite orbits and satellites.

The current EPFD validation software is based on Recommendation ITU-R S.1503-2.

The methodology is complex and in order to increase the confidence in any software tool, the Bureau felt that at least two independent implementations of Recommendation ITU-R S.1503 would be necessary. Accordingly, two commercial software development companies have developed EPFD tools for checking compliance under Article 22 or coordination requirements under 9.7A and 9.7B (EPFD-A and EPFD-T).

In 2016 the Bureau finalized the software tools in accordance with Recommendation ITU-R S.1503-2.