Why WRC-23 will be pivotal for terrestrial services

By Martin Fenton, Chairman, ITU-R Study Group 5

Since 2019, working parties of Study Group 5 in the ITU Radiocommunication Sector (ITU-R – one of three Sectors of the International Telecommunication Union) have been leading the preparatory work on ten agenda items, plus Issues b) and c) of agenda item 9.1, for the next World Radiocommunication Conference, WRC-23.

This work falls into two broad areas:

• Spectrum for mobile/wireless broadband connectivity.
• Aeronautical and maritime spectrum issues.

Mobile/wireless broadband connectivity

Several WRC-23 agenda items address spectrum for new, upgraded or additional identifications for International Mobile Telecommunications (IMT).

Agenda item 1.1: Various countries are interested inthe 4.8-4.99 (GHz) band for expanding their IMT services.

The band was first identified for IMT use in 2015, with a set of technical conditions including a power flux density (pfd) limit to protect the aeronautical mobile service (AMS).

At the next World Radiocommunication Conference, in 2019, this IMT identification was extended to 40 countries worldwide, but with diverging views on the pfd limit, which was not applied in 11 countries. WRC-23, therefore, will consider measures to protect AMS stations in international airspace and waters from stations located in national territories, as well as reviewing the pfd limit.

Agenda item 1.2: With increasing demand for IMT applications, additional spectrum identifications in the mid-band frequencies are being considered to help support IMT services that might be difficult to implement using lower or higher frequency bands. Several bands are being considered between 3.3 GHz and 10.5 GHz (see list in the margin).

Identifying spectrum for IMT at the global and regional levels is important to ensure mobile networks can meet the world’s growing demand for mobile data and provide coverage for anyone, anywhere, at any time.

Agenda item 1.3: The band 3 600-3 800 megahertz (MHz) supports various wide-area mobile services (including for wireless broadband connectivity) in several countries. In Region 1 (see map of regions under “Regional perspectives”), the band is allocated to the mobile service on a secondary basis. An upgrade to primary could provide greater regulatory certainty for countries wishing to use the band to develop their mobile services.

Agenda item 1.4: Mobile broadband services can be a challenge to provide in large, sparsely populated areas where the use of ground-based infrastructure is difficult.

The use of high-altitude platform stations as IMT base stations (HIBS), typically flying in the stratosphere at altitudes between 20 and 50 kilometres, can provide cost-effective mobile coverage over wide areas. However, these airborne base stations can cause interference to systems in neighbouring countries.

To address this risk, the conference will look at HIBS in bands below 2.7 GHz that are already identified for IMT.

Agenda item 9.1 b): Some countries have reported harmful interference from amateur radio use in the 1 240-1 300 MHz band to certain radionavigation satellite service (RNSS) ground receivers. Additional measures will be considered to protect the radionavigation-satellite service in the same band, with a possible new ITU-R Recommendation to provide guidelines for avoiding harmful interference to RNSS receivers in future.

Agenda item 9.1 c): Several countries are interested in using IMT for fixed wireless broadband in bands allocated to the fixed service. The International Telecommunication Union (ITU) is studying such uses on a primary basis, taking relevant ITU-R studies, handbooks, recommendations, and reports into account.

Aeronautical and maritime

Aeronautical and maritime spectrum are crucial for safety of life and the operation of global navigation systems. Six agenda items for WRC-23 are especially important in this regard.

Agenda item 1.6: Sub-orbital vehicles can support scientific research, passenger transport, and potentially satellite launches. Operating at higher altitudes than traditional aircraft, they may enter space but are not intended to complete a full orbit before returning to Earth.

The conference will consider the regulatory provisions needed for these vehicles to operate safely and communicate reliably with air traffic management systems and ground control facilities.

Agenda item 1.7: Growing interest in non-geostationary satellites is opening up new opportunities for their use, including very high-frequency (VHF) aeronautical communications over large oceanic and other remote areas where terrestrial systems cannot reach. VHF communications via non-geostationary satellites would complement existing terrestrial VHF systems by facilitating satellite communication with the standard VHF radios already installed on aircraft.

WRC-23 will consider a possible new allocation to the aeronautical mobile-satellite (R) service, AMS(R)S, for such communications in all or part of the 117.975-137 MHz band, provided this would not interfere with or constrain existing aeronautical VHS systems.

Agenda item 1.8: Interest is growing in the use of unmanned aircraft systems, which are piloted remotely, in international airspace.

The WRCs in 2012 and 2015 considered how unmanned aircraft could operate safely using fixed satellite service (FSS) networks and frequency allocations. WRC-23 will now consider regulatory actions to accommodate FSS network use for the control and non-payload communications (CNPC) by unmanned aircraft. Payload applications are unrelated to aircraft control.

A key question is whether FSS allocations that are not designated as “safety” allocations in the Radio Regulations can be used to control unmanned aircraft.

Other safety considerations, such as redundancy, may also come into play. Defining how to ensure safe CNPC operation for unmanned aircraft systems is a responsibility of the International Civil Aviation Organization (ICAO), as specified in relevant standards and recommended practices.

Agenda item 1.9: Spectrum in the high-frequency (HF) range, between 2.85 MHz and 22 MHz, has supported long-range communications to aircraft that are beyond the range of VHF terrestrial systems (noting that satellite communication is also used). WRC-23 will consider changes to the Radio Regulations that would allow the use of existing HF bands by digital technologies in safety-of-life applications for commercial aircraft.

Agenda item1.10: The conference will also look at potential new spectrum allocations for “non-safety” applications within the aeronautical mobile service in the 15.4-15.7 GHz and 22-22.21 GHz bands for wideband line-of-sight data links. This would allow the exchange of data between aircraft, and from aircraft to the ground, to support observation missions, search and rescue, earth science, and land management.

Agenda item 1.11: Three issues relate to the Global Maritime Distress and Safety System (GMDSS).

WRC-23 will continue the work of previous WRCs on modernization and e-navigation. Recent changes by the International Maritime Organization (IMO) to the International Convention for the Safety of Life at Sea (SOLAS), 1974 need to be considered in relation to GMDSS. These include changes to the frequencies used for emergency position-indicating radio beacons (EPIRBs) and the resulting potential to use, for example, the 1 645.5-1 646.5 MHz frequency band for general maritime radiocommunication.

Two geostationary MSS (mobile satellite service) systems currently provide safety communication in the GMDSS, the latter of which was introduced at WRC-19. The IMO is considering introducing additional satellite systems for GMDSS. These may require new or modified provisions in the Radio Regulations based on the results of ITU-R studies.

These are frequency bands considered for IMT:

• 3 600-3 800 MHz and 3 300-3 400 MHz (Region 2)
• 3 300-3 400 MHz (amend footnote in Region 1)
• 7 025-7 125 MHz (globally)
• 6 425-7 025 MHz (Region 1)
• 10 000-10 500 MHz (Region 2)

This article first appeared in the ITU News Magazine, which outlines key technical and regional perspectives on topics to be discussed at the World Radiocommunication Conference (WRC-23) taking place in Dubai, UAE, between 20 November and 15 December 2023.

Header image credit: Arif Mehmood