By Subhankar Pal, Global Research & Innovation Leader for Future of Networks, Capgemini Engineering

The mobile industry has done an impressive job of extending service to all corners of the globe, yet many people still live and work in places with untouched by cellular: roughly 390 million in 2021. That’s more than the entire population of the U.S., the world’s third largest country.

The shortfall looks even more dismal when you dig into the types of coverage. With peak speeds in the tens of megabits, LTE can support bandwidth-intensive applications such as video telehealth. But a dozen years after its commercial launch, LTE still doesn’t serve nearly 1.1 billion people. And by 2026, 40 percent of the world’s population still won’t have 5G service, while 4G will still fall short by about 1 billion people.

Many of those people live in places where wired internet services are too slow, too expensive or simply unavailable. So they pin their hopes on the arrival of 4G and 5G for access to services that require broadband speeds, including telemedicine, education, e-commerce and streaming entertainment. As the U.S. shows, this digital divide isn’t limited to developing countries, either.

“Approximately 19 million Americans — 6 percent of the population — still lack access to fixed broadband service at threshold speeds,” the FCC says. “In rural areas, nearly one-fourth of the population — 14.5 million people — lack access to this service. In tribal areas, nearly one-third of the population lacks access.”

For both the unserved and underserved, spaceborne and airborne networks offer hope — and not just in the form of traditional satellite internet services. The key to finally bringing true broadband services to every person everywhere is putting 6G cellular technology aboard LEO, MEO and GEO satellites and high-altitude platform systems (HAPS), transforming them into base stations capable of serving even the most remote places, such as the middle of the ocean.

Look Beyond 5G

Why not put 5G on those spaceborne vehicles? After all, 5G technology is commercially available and is descending down the cost curve. Meanwhile, preliminary work on 6G is barely underway, meaning the initial 3GPP standards probably won’t be finalized until late this decade.

5G’s main drawback is that it’s designed exclusively for terrestrial use. It can’t provide connectivity to users in places where it’s difficult, cost-prohibitive or impossible to install base stations, such as in the middle of the ocean, a sparsely populated desert or miles above the Earth.

Although Beyond 5G (B5G) standards work on non-terrestrial network integration is underway, the full specification will go beyond the B5G timeline. 6G is a clean slate, so it avoids the shortcomings and challenges that inevitably come with trying to make an existing technology work where it was never intended.

Non-terrestrial 6G network also would enable new applications and extend existing ones to places where they’re not currently viable because of coverage or cost. Some potential examples:

• Seamless, global connectivity for monitoring shipping containers full of high-value products, such as seafood that must maintain a strict temperature zone during the entire voyage.

• Reliable voice, video and broadband data services for first responders in places where a major disaster has disabled terrestrial networks.

• Providing service to drones and commercial aircraft, including the emerging urban air taxi services.

• Seamless connectivity in trains, hyperloops and other vehicles operating at very high speeds i.e. over 1,000 km/h.

Work also is underway to ensure that 6G satellites and HAPS can complement terrestrial networks.

For example, ITU-R published a report on key elements for integration of satellite systems into next generation access technologies.

3GPP’s Non-Terrestrial Network (NTN) integration initiative is expanding the reach of cellular networks through satellite connectivity and other airborne and spaceborne vehicles. With NTN, cellular networks will be able to leverage spaceborne infrastructure for the first time, which will drive explosive growth for the satellite industry.

The Telecom Infra Project (TIP) recently formed the Non-Terrestrial Connectivity Solutions (NTCS) Project Group to foster a hardware and software ecosystem that supports emerging standards, allowing 5G to be used natively on satellites or other non-terrestrial platforms, including HAPS. The expected impact of the NTCS deliverables is to dramatically lower the total cost of ownership and barriers to entry for non-terrestrial systems (especially satellite and direct-to-handset connectivity) by aligning value and supply-chains with the much larger global cellular ecosystem.

All of this work, along with the recent commercialization of the space sector, is already attracting billions of dollars of investment from government entities and the private sector. SpaceX, United Launch Alliance (a joint effort by Boeing and Lockheed Martin), Northrop Grumman and Blue Origin are few big names in this industry. SpaceX alone has around 1,800 Starlink satellites in orbit so far. In April 2021, Amazon secured nine ULA Atlas V launch vehicles for its ambitious Project Kuiper.

Aim High to Avoid Falling Short

Telecom companies increasingly recognise these benefits and market opportunities, which is why they’re partnering with these space companies. The first use case that telcos are targeting is satellite backhaul for rural 5G. For example, KIDDI recently selected SpaceX’s Starlink for backhaul in remote Japan.

Recently, the American satellite company Ligado partnered with Mavenir to develop base stations for beyond-5G mobile satellite networks by 2022. SoftBank’s subsidiary HAPSMobile is accelerating HAPS R&D to provide stable, high-quality connectivity for future commercial services. HAPSMobile also is developing Sunglider, a solar-powered UAV to provide connectivity from the stratosphere to the ground while flying in a circle.

Even so, more work needs to be done to make non-terrestrial 6G a commercial reality. For example, integration of non-terrestrial infrastructure poses several challenges that needs to be addressed to provide high-quality service. With satellites, the main integration challenges are high latency, spectrum scarcity, handover issues (LEO or MEO vehicles will be moving faster than the devices they serve on the ground), doppler effect and more. Latency isn’t a problem with HAPS, but it has other challenges, such as like lightweight structures, energy storage and power delivery, thermal management, system reliability, navigation, endurance and safe operations at lower altitude.

Integrating satellite and airborne networks with terrestrial wireless infrastructure is key for providing ubiquitous communication services. Early trials and implementations never took off successfully due to commercial factors. But the marketplace and technologies have evolved, paving the way for spaceborne and airborne 6G to live up to its potential.