Building networks in thin air

Mobile connectivity is ubiquitous, transforming the world around us. 3GPP network coverage now serves around 95 percent of the world’s population. However, this coverage is essentially 2D, built to support users and services at ground level.

The digital airspace is about connectivity in the air, be that unmanned aerial vehicles (UAV) like drones and air taxis or helicopters and commercial airplanes. These are all operational at various altitudes ranging from ground level to over 3,000 m. For a safer, smarter and more sustainable digital airspace, high-performance 3D radio networks with predictable coverage and capabilities offer the best solution for enabling use cases in both manned and unmanned aviation.

The need for transformative airspace connectivity

There are three prevalent conventional communications technologies in the aviation industry today, some of which have been in use for more than 50 years. These include very high frequency (VHF) radio for voice, automatic dependent surveillance broadcast (ADS-B) for positioning and satellite communication to bring basic data connectivity. Satellite comes at a very high cost in bandwidth and latency as well as service costs, although these dimensions have improved recently with the introduction of low Earth orbit (LEO) satellites.
 
To meet the requirement for predictable and reliable data communication, the industry has explored in recent years how 3GPP technology can bring these capabilities to the digital airspace. For example, secure connectivity and low latency mean it has the potential to unlock new possibilities for mission-critical communications, drone operations and management such as beyond visual line of sight (BVLOS) flights.

Large-scale drone utilization requires BVLOS. There are presently no air traffic management (ATM) communications where low-altitude drones operate, as ATM has a mandate to monitor controlled airspace and low altitude is mostly uncontrolled. However, drone operations are increasing, and are expected to be greater than manned aviation today, making airspace management essential. UAV traffic management (UTM) systems will need to be highly automated and built to handle large volumes of drone operations safely and provide a suite of services to drone operators, as well as to interwork with ATM systems.

Mobile networks are perfectly positioned to enable UTM systems toward large-scale BVLOS drone utilization –as well as many additional services, for example using SIM density data to plan routes that avoid highly populated areas.

Airspace is a scarce resource around airports and busy flight paths today, however the number of congested areas will grow as UAV operations increase. With sufficiently reliable data, automation and technical performance, airspace can be more efficiently utilized through shortening the intervals between passing aircraft, therefore increasing airspace capacity – for example, a two-minute interval compared with a three-minute interval increases capacity by one-third. 3GPP connectivity is a key enabler for the low-altitude unmanned segment as well as for mid-altitude air taxis and electric vertical take-off and landing (eVTOL), supporting the entire AAM field. 3GPP technologies shall not only provide secure and resilient connectivity to eVTOLs but also provide capabilities like precision landing at emerging vertiports where these eVTOLs will land.

Opening up the digital airspace for mission-critical use cases

From a communications perspective, the digital airspace can be split into three altitude levels that are each enabled and served in different ways. At a low altitude, below 300 m, applications will be for multiple drone use cases; the medium altitude, between 300–3,000 m, is predominantly for general aviation, defense and future applications for eVTOL and AAM; and high altitude, above 3,000 m, is predominantly for defense and commercial airlines. At low altitudes, below 300 m, industries are increasingly considering drones for a wide range of mission-critical operations and enterprise applications such as:

• Rail: Drones can conduct rail-line surveys, monitor project progress and inspect rail infrastructure, helping identify issues early on and reduce costly manual inspections.
• Utilities: Drones can inspect power lines, wind turbines and solar panels, as well as monitor oil and gas pipelines instead of costly helicopters, helping identify and fix problems more quickly with lower costs and reduced risk of accidents.
• Logistics: Automated delivery of packages and goods using drones can make delivery quicker, more efficient and more sustainable, contributing to CO2 reductions and increasing societal inclusions.
• Health care: Drones can help save lives in time-critical situations, such as by quickly delivering defibrillators or transporting blood to hospitals, labs or into the field.
• Public safety: First responders like police and firefighting personnel can use drones for better situational awareness and real-time decision making.
• Agriculture: Drones equipped with sensors and cameras can monitor crop health, helping farmers optimize their use of pesticides, fertilizers and water to increase crop yields and contribute to wildlife protection or control.

Learnings from Teracom’s 3GPP commercial AGA network

The Swedish mobile operator, Teracom, delivers an aerial, nationwide 3GPP network to private and public national critical infrastructure enterprises.

Teracom’s network design is based on an innovative design philosophy that utilizes existing high TV masts with varied heights of up to 300 m, and wide-area, high-capacity, 5G-ready 2.3 GHz spectrum, deployed across 160 sites nationwide.

The main deployment scenario is to enable maximum cell range for the air coverage, which has been verified successfully for data connectivity at a maximum range of 90 km in flying vehicles such as helicopters, airplanes and drones. Use cases tested ranged from blue-light missions and healthcare transport to various forms of situational awareness for critical communications, such as remote search and rescue using high-definition, real-time video and infrared heat cameras, as well as the continual monitoring of air quality, fire, smoke and weather developments based on live data feeds.

Actual flight tests have been conducted in the mid- to high-altitude segment, shown in Figure 29. The benchmark ground network showed poor coverage, resulting from the fact that it was built for ground coverage and is therefore likely to experience poor cell edge-like performance at higher altitudes. However, the AGA network shows good coverage based on the Teracom network. A key difference that impacted performance was the number of handovers. These comprised 15 in 15 minutes, compared to just 3 handovers in the AGA network, indicating a more consistent set of performance characteristics.

The tests demonstrated that 3GPP technology, when dimensioned for the skies, can provide the required reliable and predictable connectivity in the mid- to high-altitude segment, putting them on a path toward future innovation and opening up a gateway for future UAV and AAM development.

In medium-altitude segments, where helicopters operate, digital connectivity brings new possibilities in mission-critical cases like air ambulances. At ground-level today, the emergence of connected ambulances is enabling real-time communication between patients, ambulance workers and remote medical experts – not only through voice, but through high-definition video and data sharing in emergency situations. By addressing this segment, the same level of connectivity and service can be brought to the most critical patients.

Advancements in electrification are revolutionizing design and enabling eVTOL aircraft to gain momentum. Analysis of industry trends suggests that piloted air taxis are likely to emerge in the next two to three years, with early trials having already begun.

The high-altitude segment is predominantly for commercial passenger aircraft and defense aviation. This segment can benefit from non-terrestrial networks (NTN), with 5G 3GPP technology integrated in satellites, which complement AGA 3GPP networks to drive a common solution and economies of scale through utilizing devices with the same chipsets. Transformation in this segment is evolving and new technologies are being adopted, while areas like in-flight entertainment and passenger connectivity will advance more quickly.

Building a 3GPP network in thin air

How mission-critical mobile broadband solutions for the digital airspace are built will depend on the altitude above ground at which coverage is needed, as well as the industry use cases. It is important to consider horizontal and vertical aspects in relation to cell handovers and interference from neighboring cells.
 
Use-case requirements on latency, data throughput and positioning accuracy must also be considered, as well as Doppler-effect compensation for air vehicles with relatively high speeds, such as commercial airlines. At low altitudes, communications service providers can generally leverage existing network infrastructure with some enhancements such as 5G massive multiple input, multiple output (M-MIMO) and beam forming to address interference. However, at altitudes above 300 m, interference issues and handover challenges become more of an issue, especially for high-speed use cases. This will require a dedicated 3GPP aerial network covering the skies.

The availability of radio-frequency spectrum resources is vital in enabling reliable communication with UAVs. Most drones today use unlicensed spectrum, which will not be sufficient going forward as new use cases emerge and the volume of drones increases. It is also important to note that the spectrum situation differs from country to country. Often, spectrum issues can be managed by utilizing communications service providers’ existing spectrum, with their networks dimensioned to support UAVs.

Emerging innovation within the low altitude segment

With the broad range of UAV use cases being explored within the AAM and eVTOL areas, the low- to mid-altitude segment is a hive of activity and innovation. 3GPP connectivity offers a wide range of benefits that are not possible with existing communications technologies, not least of which is enabling real-time data sharing and constant connectivity.
 
This can be enhanced through network APIs that will enable dynamic control of quality of service, drone identification, drone location tracking, 3D-coverage maps and geographic SIM density, all of which will result in improved safety, efficiency and cost savings for the aviation industry. Positioning is a key area for ensuring UAV safety. 3D satellite positioning is subject to spoofing and blocking, so the network can play a key role here in validating the positions and, in case of issues, perform as a fallback solution. A ground-level-specific solution can provide positioning within 1 m accuracy, important for eVTOL aircraft take-off and landing zones. The macro network provides accuracy of around 10 m.

Standardized APIs aligned with CAMARA and GSMA Open gateway will create new opportunities for innovation and collaboration between the aviation and mobile network industries, as illustrated in Figure 30. This will lead to the development of new products and services that can further enhance the digital airspace ecosystem.

Future of digital airspace

High-performing 3D radio networks with predictable coverage and capabilities will enable advanced automated drone applications and innovative advanced air mobility for a safer and more sustainable digital airspace.

With the continued developments of 5G Advanced, NTN and the introduction of 6G, the possibilities in the digital airspace will continue to expand. This will include the application of new capabilities like integrated sensing and communications, which will support immersive and awareness applications in the digital airspace. This capability will make it possible to perform RADAR-like functionality with the ability to detect objects without a SIM in the sky.