Determining how to close the urban/rural digital divide has confounded the communications industry ever since its inception, with the way lined with corpses of failures, of which Google’s Project Loon is one of the most recent. But new efforts keep emerging and many, in recent years, have centered on High Altitude Platforms (HAPs), which can be regarded as hybrids between balloons and aircraft, launched into the stratosphere at heights between 20 and 50 kilometers (12-30 miles), drawing small amounts of power from solar cells to maintain a fixed position.
A significant development is that HAPs are starting to deliver cellular services, either 4G or 5G, as in a Swiss HAP recently tested for covering rural and tribal areas at speeds close to 100Mbps. This was in the semi-autonomous Indian reservation of Navajo that includes parts of the US states of Arizona, New Mexico and Utah.
This has garnered extra interest because of its use of Open RAN LTE in the hope of being independent of equipment suppliers in the future. The HAP units themselves resemble the airships of yesteryear, although with the important difference that they rely on some inert lifting gas such as helium to achieve atmospheric buoyancy, rather than hydrogen, as was sometimes used fatefully.
The Navajo trial used platforms made by Swiss materials company Sceye, selected because of its promise to endure longest in the field through use of a durable skin designed to withstand the low and widely fluctuating temperatures at the operating altitude of 65,000 feet (20km). The light skin and low weight lithium-sulfur batteries helped keep costs down and avoid use of additional forms of propulsion such as rocket motors that satellites require. Another key requirement was low permeability to the lifting gas, to minimize leakage so that the platform could stay in the air as long as possible before coming down for maintenance or replacement.
The firm went for the airship form rather than balloons or fixed wing aircraft because this made it easier to main geo-stasis while carrying a greater payload than other contenders to date. A key point here is that at the operating height of 20km, the rarefied air has a density only 7% of that at sea level. Since lift is directly proportional to air density, the wing area for airplanes, or volume for airships and balloons, must be about 14 times greater than it would have to be for operation close to ground under the same working parameters such as speed. This imposes the severe constraints over weight of materials used and shape of the structure.
One advantage of this operating height is radio range, with Sceye claiming to have achieved 140km to set a record for LTE Open RAN, 40km further than possible with standard LTE. “We view the successful flight and the record setting data connection as a significant milestone for our technology, one that could dissolve the rural broadband barrier,” said Sceye CEO Mikkel Vestergaard Frandsen.
Such promises to end that barrier have been made many times before, so judgement will have to be reserved, but this platform has made a promising start. Sceye was founded in 2014 by Frandsen to work specifically on application of solar-powered HAPS for providing broadband service, as well as improving environmental and disaster monitoring.
The company has now joined a consortium of New Mexico-based telcos and tribal organizations for pilots aiming to deliver universal broadband access to the Navajo Nation, with financial support from New Mexico. Other members of the consortium include Sacred Wind Communications, CellularOne, PVT Networks/Penasco Valley Telecommunications Cooperative, the Santa Fe Indian School, and Navajo Technical University. Currently 60% of the Navajo Nation’s 300,000-plus residents lack fixed Internet access, which Sceye aims to provide.
Among previous failed projects to dissolve that broadband divide, the highest profile and recipient of most investment was probably Google’s balloon-based Loon. With so much capital, both financial and intellectual, invested in it, it is not surprising that Google, or strictly speaking Alphabet as the parent holding company, has refused to dismiss Loon as a failure despite finally closing it down in January 2021.
Loon’s idea of balloon-based FWA (fixed wireless access) dates back to 2005 at least, and hopes soared after Project Loon was launched as an R&D project in 2011. The high watermark came around 2017 when Project Loon played a role in the response to Hurricane Maria, as regulator FCC granted the company a temporary license to provide wireless service in Puerto Rico when it was devastated by that storm in September that year. This demonstrated one of the principal use cases for FWA in general, the ability to establish communications rapidly in response to an emergency, or over a somewhat longer scale for construction and engineering sites.
This led to Project Loon being spun out of Alphabet in 2018, but thereafter it deflated as it proved impossible to make it economically viable on any scale. It was an example of a project that ultimately failed to make the third grade of any technological project. The first step is theoretical scientific feasibility, while the second is technological or engineering achievability. The final stage is then commercial viability. Nuclear fusion is still stuck in the first phase after almost half a century, while quantum computing is entering the second stage.
Google successfully propelled Project Loon from stage one to two through huge backing, with the result that analysts raised its probability of ultimate commercial success from just 1% to 2% at the outset to 50% shortly after the success in that hurricane response. Whether that 50% figure represented an accurate assessment of prospects may be doubtful, but does reflect the technological advances made.
In the event there was great disappointment among Loon advocates when the project did close. But there is some justification to the claim it was not a failure because one pillar of the technology lives on in a project called Taara, also backed by Alphabet but in partnership with South African based telco Econet to provide Internet service across sub-Saharan Africa.
This dispenses with balloons but uses Loon’s free space optical technology for linking terminals on the ground at distances up to 20km and speeds up to 20Gbps. This technology had been developed for linking balloons at distances up to 100km apart in the stratosphere, where with barely any water vapor there is less signal attenuation and so longer range. It has been dubbed “optical fiber without the wires” because of its use of narrow focused beams of light to transmit signals.
Line of sight is required so the terminals have to be located on masts or rooftops, making Taara best suited to relatively flat areas such as much of the southern African Veld. There have been small pilots in Kenya, followed by deployment to serve Econet’s Liquid Telecom broadband customers in Kenya. Taara then is yet another attempt to extend broadband reach in areas previously unserved by high-speed connections.