Tag: International Telecommunications Union

UN agencies denounce GNSS interference
The International Telecommunications Union (ITU), International Maritime Organization (IMO) and International Civil Aviation Organization (ICAO) recently issued a joint statement urging “Protection of the Radio Navigation Satellite Service from Harmful Interference.”

All three organizations are United Nations agencies and have previously issued similar statements independently. This is the first time they have spoken on this in one voice.

In 2020, ICAO issued a letter to all member states urging them to “strengthen CNS systems resilience and mitigate interference to GNSS.” It contained 13 recommendations resulting from three different work streams within the organization. The last of the recommendations was “… to support the multi-disciplinary development of alternative positioning, navigation and timing (APNT) strategy and solutions to complement the use of GNSS in aviation in coordination with ICAO and airspace users.”

In 201, IMO issued a circular on deliberate GNSS interference.. It called on nations to prevent interfering transmissions coming from their territories, issue warnings about known interference, and consider taking actions to prevent unauthorized interfering transmissions.

ITU issued a circular on “Prevention of harmful interference to Radio Navigation Satellite Service Receivers in the 1559 – 1610 MHz frequency band” in 2022. It emphasized that, according to ITU Radio Regulations, “All stations are forbidden to carry out unnecessary transmissions, or the transmission of superfluous signals, or the transmission of false or misleading signals…”

This ITU circular urged nations to “address the critical issue” by:
- Reinforcing navigation systems’ resilience to interference.
- Increasing collaboration between radio regulatory and enforcement authorities.
- Reinforcing civil-military coordination to address interference risks associated with RNSS testing and conflict zones.
- Increase coordination between aviation, military and radio-regulatory authorities.
- Retain essential conventional navigation infrastructure for contingency support in case of RNSS outages and develop mitigation techniques for service loss.
A resolution by ITU’s 2023 World Radiocommunications Conference echoed similar themes. Still, it was criticized because its cautions and prohibitions came with the caveat, stating “…without prejudice to the right of administrations to deny access to the RNSS, for security or defense purposes.”

Many observers opined that there are few reasons for nations to interfere with GNSS other than security or defense concerns, which allows malicious actors to have carte blanche. Furthermore, it was suggested that the resolution might have included language to ensure that security and defense-related disruptions do not extend beyond a nation’s borders or similar provisions.

While no specific events are cited in the statement as motivating its publication, the death on Christmas Day of thirty-nine people aboard an Azerbaijan Airlines flight could have been the reason. The aircraft was approaching a Russian airport during an intentional interference event and was apparently misidentified by Russian forces. It was subsequently damaged by ground fire and crash-landed in Kazakhstan.

The recent joint statement cites, among other international agreements and actions, the ITU Constitution, which says, “All stations, whatever their purpose, must be established and operated in such a manner as not to cause harmful interference to the radio services or communications of other Member States.”

The joint statement concludes with:

Therefore, ITU, ICAO and IMO jointly and urgently call on their respective Member States to:
- Protect the RNSS from transmissions that can adversely cause harmful interference, degrading, interrupting, or misleading signals used for civilian and humanitarian purposes.
- Reinforce the resilience of the systems that rely on RNSS for navigation, positioning, and timing in relation to this type of interference.
- Retain sufficient conventional navigation infrastructure for contingency support in case of RNSS outages and misleading signals, and develop mitigation techniques for loss of services.
- Increase collaboration between radio regulatory, civil aviation, maritime, defense and enforcement authorities.
- Report cases of harmful interference affecting RNSS to the appropriate telecommunication, aeronautical, and maritime authorities and the ITU Radiocommunications Bureau to enable the monitoring of the situation.
The United Nations and its agencies are collaborative bodies that operate by consensus and through the cooperation of members. As such, they have no ability to enforce standards or compel compliance with recommendations.

Read the joint statement here.
March 26, 2025
With 10,000+ aviation events in 2021, ITU issues GNSS interference warning

By Dana A. Goward

Earlier this month, the International Telecommunication Union (ITU) issued a circular urging its member states to prevent interference with GNSS signals and receivers.

ITU is the latest United Nations body to express such concerns and issue an advisory. The International Maritime Organization issued a similar document in 2021, as did the International Civil Aviation Organization in 2020.

ITU is the United Nations agency that deals with information and communications technology. Its remit includes coordinating spectrum use and satellite orbits.

ITU’s Radio Communications Bureau sponsors the World Radiocommunication Conference every three to four years. The issue of interference with GNSS signals was reported at the 2019 conference.

Since that time, according to this month’s circular, the group “has been informed of a significant number of cases of harmful interference to the radionavigation-satellite service…”

Despite concerns expressed by maritime and other interests, the circular focuses entirely on aviation interference. It says the reports it has received have been about “receivers onboard aircrafts and causing degradation or total loss of the service for passenger, cargo and humanitarian flights…” These have included “misleading information provided by RNSS [radionavigation satellite service] receivers to pilots.” An often cited example of this is a well-publicized 2019 incident in Sun Valley, Idaho. In that case a passenger aircraft nearly hit a mountain.

Describing interference with GNSS as a global and recurrent problem, the circular cites data collected by a major aircraft manufacturer. The company found “10,843 radio-frequency interference events … globally in 2021. The majority of these events occurred in the Middle East region, but several events were also detected in the European, North American and Asian regions.”

This year’s uptick in GNSS interference in Scandinavia, the Baltics, and around Ukraine since Russia’s February invasion of Ukraine is not mentioned. This is likely due, in part, to timing. ITU’s Radio Regulations Board met in March 2022 and directed the circular be issued.

Many within the positioning, navigation, and timing community have long asserted that interference with GNSS signals, whether deliberate or accidental, constitutes a violation of ITU rules and regulations. This month’s circular affirms this and cites several applicable provisions.

These include prohibitions on harmful interference with any authorized radio frequency transmission, requirements for users to transmit only in bands for which they have authorization, and for all to generally safeguard aviation operations.

The circular highlights provision 15.1 of ITU’s Radio Regulations as particularly applicable. It states:

“All stations are forbidden to carry out unnecessary transmissions, or the transmission of superfluous signals, or the transmission of false or misleading signals, or the transmission of signals without identification…”

As is the case with almost all international agreements, enforcement of ITU rules is the responsibility of its member states.

While most expect the advisory to have little immediate impact on reducing global interference with GNSS signals, it does help reinforce the issue as one of international concern.

According to a retired government official, “Member states that fail to comply with international rules to which they have agreed lose credibility and standing in the community of nations. Even when they have little credibility or standing to begin with, the behavior adds to their marginalization and life is just a little more difficult for them. This can, in the long run, nudge them toward being more responsible players.”

Photo: jpgfactory/iStock/Getty Images Plus/Getty Images

July 25, 2022
Maintaining the 1-dB standard

How do we ensure that GPS is protected from harmful interference?

By J. David Grossman, guest columnist

J. David Grossman

Debates in Washington over harmful interference and the coexistence of divergent services are raging. Nowhere are the differences more apparent than when comparing radio navigation services such as GPS to radio communications systems used in wireless communications networks.

How do we ensure that a satellite-based radionavigation service like GPS, which by design operates below the ambient noise floor, is protected from harmful interference? The International Telecommunications Union’s (ITU) definition of harmful interference provides a starting point, by defining harmful interference as a level that “endangers the functioning of a radionavigation service.”

With this foundational definition, the internationally established criterion of a 1-decibel (dB) increase in the noise floor, otherwise known as the 1-dB standard, provides the answer, offering a readily identifiable, objective and predictable metric.

The 1-dB standard uses a 1-dB increase in the noise floor as the distinction between the onset of interference that can be detected by a GPS receiver and harmful interference. (This can be reliably measured by a 1-dB decrease in the carrier-to-noise ratio, C/N₀, reported by the receiver). Thus, the 1-dB standard provides a definitive way to protect GPS receivers from harmful interference. Adherence to this standard helps ensure that systems operating in an adjacent spectrum band do not interfere with GPS.

Why use the 1-dB standard instead of other metrics? The 1-dB standard is based upon well-understood GNSS engineering considerations and is associated with quantifiable changes in the overall noise to which GNSS receivers are subject, with equally well-understood effects on receiver operation. (The 1-dB standard enables system designers and spectrum regulators to carefully assess interference from various sources and analyze their net effect on GNSS receivers).

It also has been adopted internationally and has a long and well-established proven history of protecting GPS operations from harmful interference in both international and domestic regulatory proceedings.

So-called “alternatives” to 1 dB, which may be appropriate in the context of radio communications systems, fail to recognize that the accuracy, integrity and reception (availability) of GPS signals used by a receiver can be degraded by interfering noise in ways not immediately apparent to an end user. This means that the effects of degraded service of GPS signals can still be detrimental well before the user loses position accuracy or experiences complete loss of position.

Additionally, C/N₀ is computed at the entry point of a GPS receiver, such that a 1-dB decrease serves as an early warning of interference potentially becoming harmful. Other metrics, computed further downstream, may be indicative of harmful interference already occurring.

GPS has become a fundamental part of our lives and is an integral engine of the U.S. economy, creating new jobs, and unlocking innovation. Maintaining the 1-dB standard ensures that the GPS success story and American innovation will continue for decades to come.

J. David Grossman is executive director of the GPS Innovation Alliance.

February 4, 2020