Potential Risk of Interference of 5G Signals on Aircraft Radio Altimeter

In Canada, 5G networks rely on the 3500 MHz bands (3450-3650 MHz) to deliver high-speed service. Some countries in Europe, Asia, and the United States have already deployed 5G using the 3500 MHz bands. For 5G to offer a noticeably better experience than 4G, it needs broad, dedicated channels, ideally 50MHz or wider. In addition, it needs to be below 6000 MHz to get a decent coverage range.

These 5G 3500 MHz bands are too close to the 4200-4400 MHz bands used by aircraft radio altimeters, the instrument used by aircraft to measure their altitude. Several studies completed by international organizations concluded a likelihood of interference with specific radio altimeter models by the 5G radio waves in numerous operational scenarios and most notably at low altitudes. The most undesirable outcome of interference is the indication of undetected erroneous height information given by the radio altimeter.

Given that radio altimeters are critical in aeronautical services, Innovation, Science and Economic Development (ISED) proposed amendments to the technical requirement for fixed and mobile systems using the 3500 MHz bands. Said amendments were set in place to protect aircraft safety while still allowing the deployment of 5G operations. The main protection measures include:

  • Exclusion and protection zones to mitigate interference around certain airport runways where automated landing is authorized.

  • A national antenna down-tilt requirement to protect aircraft used in low altitude military operations, search and rescue operations and medical evacuations all over the country.

Several cellular companies and industry organizations commented that the publicly available reports, including ISED's calculations, do not prove that flexible use operation in the 3500 MHz bands will cause harmful interference to radio altimeters. Therefore, the proposed amendments to the technical requirement for fixed and mobile systems are not justified and would significantly impact 5G deployments in Canada.

Currently, determining whether mitigations measures are required, ISED anticipates that additional evidence from domestic and international studies, such as the European Union Aviation Safety Agency report, will be available throughout the balance of this year and into 2022. Also, ISED will continue its internal studies, lab testing of radio altimeters, and discussions with other regulators. Furthermore, work is underway in the United States to assess potential interference from future 5G operations in the 3800 MHz bands (3650-3980 MHz to be auctioned in Canada in the future).