UK fears Starlink and OneWeb could interfere with each other, plans new rules


Illustration of many satellites orbiting the Earth.
Enlarge / Artist’s impression of low-Earth orbit satellites such as those launched by SpaceX and OneWeb.

A UK government agency is concerned that OneWeb, SpaceX’s Starlink and similar Low Earth Orbit (LEO) satellite broadband systems could block each other’s signals.

Ofcom, the UK communications regulator, today proposed new rules in a report detailing your concerns about interference. Ofcom also said it intends to modify satellite licenses already issued to SpaceX and OneWeb to require coordination of frequency use. Without new requirements, the risk of interference could prevent competition by excluding new players from the market, Ofcom said.

Non-geostationary-satellite orbit systems (NGSOs) are more complex than traditional geostationary-type systems because they use hundreds or thousands of satellites, Ofcom noted. “Satellite dishes need to track these satellites as they move across the sky, unlike existing satellite networks, where the antennas are fixed pointing at a single satellite that is stationary in the sky,” the Ofcom report said. Because so many satellites are being launched into low Earth orbit, “there is a risk that the satellites of two different operators will appear to be in the same part of the sky,” causing interference known as “online events” in which various operators “The satellites are aligned in the sky,” Ofcom wrote.

This interference can affect uplink and downlink transmissions between satellites and user terminals serving individual households, according to the report. Interference can also affect the links between satellites and Gateway ground stations that connect to the Internet backbone.

“Since the NGSO satellites move relative to each other and relative to the ground, individual online events can be brief, perhaps a few seconds,” Ofcom wrote. “However, if an online event occurs and causes interference, it may take longer for the terminal to reconnect to the network. The interference could continue to recur over time, reappearing in a regular pattern depending on the orbits of the respective systems. “.

Interference interruptions

Users may lose service when there is interference at the user’s terminal or gateway earth stations, but interference at one gateway station would affect many more users. “[T]The impact of interference on the gateway links would be much greater than on individual user links, as each gateway provides connectivity for many users (perhaps hundreds or thousands of users depending on the system design), so the connection is lost due to interference at the Gateway will be experienced more widely throughout the network, “Ofcom wrote.

Gateway Earth stations operated by different companies are likely to “require large minimum separation distances” of tens of kilometers to avoid interference, Ofcom wrote. In contrast, “multiple GSOs [geostationary satellite orbit] Gateways can be located in one place “without causing harmful interference to each other.

The Ofcom report listed five NGSO constellations that are either planned or already in operation. The biggest example is SpaceX, which offers a beta service of 1,500 satellites already launched and has more than 4,400 satellites planned for its initial phase. Amazon’s Kuiper division has yet to launch a satellite, but it has 3,236 satellites planned in its initial phase, the report noted.

OneWeb, what is jointly owned by the UK government and Bharti Global-He has launched more than 200 satellites and has plans for 648 satellites in their initial phase. Telesat and Kepler round out the list, with plans for 298 and 140 satellites, respectively.

Here is the graphic from Ofcom listing the Low Earth Orbit satellite networks:

Difficult coordination

The US Federal Communications Commission in 2017 adopted rules, including power limits, to minimize the danger of interference in NGSO systems. The FCC adopted different rules for different spectrum segments. In the 17.8 to 18.3 GHz band, for example, the FCC said that “while the terrestrial use of this band is significant, there are areas, particularly rural areas, where the terrestrial deployment is less dense and through the use of mitigation techniques such as location considerations, off-axis rejection and shielding, we expect FSS [fixed-satellite service] earth stations will be able to operate successfully without receiving harmful interference … If interference occurs, earth stations can switch to other bands not shared with land users or use alternative mitigation techniques. “

The FCC also imposed specific conditions to prevent interference and space debris on the licenses granted to SpaceX, OneWeb, Amazon, and others.

Ofcom is concerned that the global satellite coordination system, overseen by the International Telecommunication Union [ITU], it is not good enough to prevent NGSO problems. “The potential for harmful interference between different satellite systems is generally handled by operators cooperating with each other under ITU satellite coordination procedures,” Ofcom wrote.

The agency added:

However, coordination between NGSO systems is proving to be more challenging due to the dynamic nature of these systems, combined with operators that have different implementation rates (some operators that have older registries will not implement their systems for a few years) and they will change their architecture. weather. Therefore, we are concerned that NGSO satellite services may be deployed before an adequate level of coordination with other operators has been possible.

Ofcom is also concerned about the coexistence of user terminals when two or more companies provide LEO satellite service in the same area:

Lack of agreement on how user terminals from different systems can coexist in the same area and band could restrict competition as a result of previously implemented systems hampering later ones. Once one operator begins to deploy user terminals, other operators wishing to launch services using the same band can expect to experience harmful interference from existing user terminals. In the worst case, this could mean that the quality of your broadband services would not be reliable enough to enter the market. However, the established actor may have an incentive to cooperate as the interference is likely to be mutual, that is, their services may also be degraded.

New rules, license changes

Ofcom said its goal in issuing new rules is to minimize interference while encouraging competition. The agency proposed, among other things, “an additional explicit license condition that requires NGSO licensees to cooperate so that they can coexist and operate within the UK without causing harmful radio interference to each other.” Ofcom said it also intends to “[i]n introduce controls when we issue new NGSO licenses so that these are only granted if all systems (existing and new) can coexist and provide services to end users “and implement new conditions that allow Ofcom” to take steps to resolve degradation of the services if this were to occur in a particular location or locations in the UK. “

To preserve competition, Ofcom said it will “introduce a competition check” in its licensing process to take into account “technical limitations that the gateway or user terminals could create on future licensees.” Ofcom said:

In particular, in a market that was concentrated, if there was a limited prospect that the licensee system and future systems (applicants) could technically coexist, this could constitute a barrier to future market entry. As a result, we propose that a key piece of information applicants must provide when applying for a network license is credible evidence about the technical ability of their system and future systems to coexist. This would include evidence about the flexibility of your system and / or what reasonable steps new licensees could take to protect them. This information would also be used when evaluating whether it is reasonable for new applications and existing services to coexist, to understand the reasonableness of mitigations being made by existing licensees.

Ofcom said it plans to review all NGSO licenses to determine which companies are using the same frequencies. The agency said it will also modify existing licenses for SpaceX Starlink, OneWeb and Kepler. The changes would require “NGSO licensees to cooperate with other NGSO licensees operating on the same frequencies so that they can coexist” and would allow Ofcom “to require operators to take action in cases of interference between NGSO systems affecting the provision of services to users in particular locations in the UK “.

Ofcom said it will accept comments on its proposals until September 20, 2021.

We reached out to SpaceX about Ofcom’s report and will update this article if the company provides a response.


arstechnica.com

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