02.10.2024

ANCOM, the Ministry of National Defence of Romania and SpaceX have conducted the first real-world test to demonstrate that non-geostationary satellite (NGSO) systems of Starlink network can operate without interfering with geostationary satellite (GSO) networks, even with relaxed power flux density (epfd) limits. Data collected from the test will be shared with relevant European and international bodies to contribute to ongoing epfd studies and ultimately improve the current spectrum regulations.

ANCOM actively participates and contributes to the work of the International Telecommunication Union (ITU). ITU is the UN body that through its World Radio Conference (WRC) is responsible for reviewing, and, if necessary, revising the Radio Regulations (RR), the international treaty governing the use of the radio-frequency spectrum and the geostationary-satellite (GSO) and non-geostationary-satellite orbits (NGSO).

The last WRC was held in Dubai at the end of 2023. Among many important decisions, WRC-23 invited the “ITU-R to conduct technical studies on the epfd limits in RR Article 22, including epfd limits referred to in RR No. 22.5K, in order to ensure the continued protection of GSO FSS and BSS networks, and to inform WRC-27 of the results of the studies, without any regulatory consequences.”

Single-entry and aggregate equivalent power flux-density (epfd) limits were developed and agreed more than 25 years ago. Non-GSO FSS systems operating in certain frequency bands must meet the epfd limits to ensure they do not cause unacceptable interference to GSO FSS and BSS networks.

In light of the invitation of WRC-23, epfd studies are now on-going at the ITU and Romania is actively following the developments. Romania considers that bridging the digital divide and providing much-needed connectivity in Romania (as well as around the world) require a combination of GSO and non-GSO services. Given the importance of both GSO networks and non-GSO systems for FSS delivery of high-speed broadband services, it is important to ascertain whether existing RR Article 22 epfd limits are appropriate when balancing the need for efficient use of the orbit and spectrum resources. Moreover, it is equally important to understand whether it is possible to adopt more efficient frameworks to ensure continued protection of GSO networks while allowing non-GSO to unleash their full potential, thus with a direct benefit on Romanian end-users.

With this in mind, ANCOM, in collaboration with the Ministry of Defence and SpaceX’s Starlink, decided to offer its contribution to the on-going epfd studies by means of a real-world test campaign to demonstrate protection of GSO networks with potential new limits for NGSOs. In order to best prepare for the test, Romania has looked into the history of how epfd limits were derived 25 years ago. Administrations at the time agreed on a 10% aggregate “unavailability increase” protection criterion for GSO links. Eventually they introduced the concept of artificial “epfd masks”. These masks are specific limits (in place today) that introduce spectrum inefficiencies, as they are, in fact, not needed and they were agreed based on compromises to ensure they would work for the theoretical non-GSO systems being studied at the time, which never became operational. ANCOM is of the view that an appropriate protection framework for GSO networks includes:

• A complete set of GSO reference links representing modern GSO operations
• Agreed protection criteria

With these two fundamental elements, it is possible to test any non-GSO system and verify protection of GSO links.

With this spirit, ANCOM has installed a real-world “epfd test” in Romania on 23-24 July, 2024, the first of its kind in the world. The Ministry of Defence provided link budget characteristics and C/N unavailability threshold of some of their most sensitive links in the country in the Ku band. The selected protection criterion to ensure protection is the same as the one agreed 25 years ago, i.e. 10% aggregate unavailability increase. Additionally, a 3% single-entry unavailability increase will also be tested. Starlink performed accurate computer simulations to extract the operational parameters needed to hit the 10% and 3% protection margins:

• N_co: number of co-frequency beams simultaneously transmitting to the test site
• GSO avoidance angle
• Power Flux Density at the victim receiver

Upon agreement of ANCOM and the Ministry of Defence, Starlink was authorised to exceed current epfd limits and operate according to the agreed operational parameters over a small area around the test site for a duration of at least six months. Data on signal, interference and noise is being collected via a spectrum analyser and will be shared in a transparent manner among the contributing parties, ANCOM, Starlink and the Ministry of Defence. The goal is to demonstrate that Starlink can meet the 10% and 3% protection criteria for these sensitive Ministry of Defence links and therefore protect them while exceeding current epfd limits.

The test will demonstrate a potential Starlink increase in capacity over the test area of about 8 times with respect to what is possible with today’s limits. With more efficient limits, all non-GSO systems will be able to provide a better service to Romanian citizens in the future while still protecting the important GSO services.

Lastly, ANCOM is planning to share the results of the test at relevant European and International ITU meetings as part of Romania’s contribution to on-going epfd studies. We hope that this work will be useful for all administrations involved in this important work, and we also hope to see many more similar tests around the world.