Writing about aerospace and electronic systems, particularly with defense applications. Areas of interest include radar, sonar, space, satellites, unmanned plaforms, hypersonic platforms, and artificial intelligence.
Low Earth orbit (LEO) satellite technology, led by Elon Musk's Starlink constellation, is transforming rail transportation by providing consistent high-speed internet connectivity even in remote areas where cellular coverage has traditionally been weak or nonexistent.
Recent deployments have demonstrated impressive results, with trains achieving throughput of 200-400 megabits per Starlink Terminal and latency under 40 milliseconds – performance comparable to urban 5G networks. One intercity rail operator implementing the technology in January 2024 reported 99.9% gateway performance, serving 169,000 passengers who collectively used more than 2 terabytes of data.
Unlike previous satellite solutions that relied on distant geostationary satellites, Starlink's LEO constellation orbits much closer to Earth at altitudes up to 2,000 km. This proximity enables faster data transmission and lower latency, making it practical for real-time applications like video surveillance and point-of-sale systems.
However, industry experts emphasize that LEO satellites are not meant to replace existing cellular networks entirely. Instead, they recommend integrating satellite technology into a comprehensive connectivity strategy that leverages the best available solution for each segment of a route, whether that's 5G, Wi-Fi 7, or satellite communications.
"By delivering strong connectivity everywhere along a route, rail leaders will be able to attract people out of their cars and off planes, and onto trains," says Gabriel Lopez-Bernal, President of Icomera's North America region. This advancement could mark a significant step forward in making rail travel more appealing to modern travelers while enabling new operational capabilities for railway companies.
In today’s trains, onboard connectivity means much more than
passenger Wi-Fi. Operators rely on connectivity for everything from
automatic passenger counting and digital video surveillance to real-time
monitoring and remote diagnostics. But the quality of on-train Internet
is highly dependent on the communications networks along the route—and
there are still vast areas where the capacity of those networks falls
short of the needs of a full passenger train.
To date, connectivity has primarily been delivered through cellular
networks. Densely populated cities and suburban areas saw a fast rollout
of the 4G and 5G cellular networks that are capable of handling
high-speed Internet and multimedia experiences. But building those
land-based networks along thin rail corridors that traverse rural areas
has long posed technical and financial challenges, creating “not-spots”
where connectivity was interrupted.
Thanks to satellites, “not-spots” are soon to become a thing of the
past. Recent developments in satellite technology and new commercial
models have finally made Low Earth orbit (LEO) satellite solutions
viable. Led by Elon Musk’s Starlink satellite constellation, the new
networks promise to make the inner-city 5G experience available
everywhere—helping transit operators achieve true digital trains across
every mile of their networks.
How Satellite Technology is Transforming Transit
While Starlink is new to the industry, this is not the first time
satellites have been tried for trains. More than 20 years ago,
geostationary satellites were a groundbreaking concept for on-train
connectivity, but the technology came with significant challenges: Costs
were exorbitant, throughput was limited and latency made many
applications impractical.
The industry shifted gears with the rise of 3G and later 4G cellular
technology. Cellular connectivity was faster, more cost-effective, and
better suited to the needs of rail operators. But now, with the advent
of LEO constellations like Starlink, the pendulum is swinging back. For
the first time, satellite connectivity offers both high performance and
affordable costs for transit.
Why does LEO technology work where geostationary fails? LEO
satellites orbit at altitudes up to 2,000 km (744 miles), much closer to
the Earth’s surface than geostationary satellites that reside at 35,786
km (22,187 miles) above the equator. Signals travel a shorter distance,
resulting in lower latency. LEO satellites can also transmit and
receive data faster—and the relatively affordable launches and mesh
network configurations for redundancy mean more reliable global
coverage.
The results for train connectivity have been impressive. The
technology delivers the equivalent of inner-city 5G capacity to trains
in rural environments, with throughput consistently in the range of
200-400 megabits per Starlink Terminal designed specifically for trains,
and latency of less than 40 milliseconds.
Since January 2024, one intercity rail operator has been leveraging a
multi-network connection among satellite, cellular and Wi-Fi. The
operator saw a gateway performance of 99.9%, connecting 169,000
passengers who collectively accessed more than 2 terabytes, proving the
viability and reliability of satellite Internet on the rails.
Why Satellites are Enabling True Digital Trains
As impressive as the results have been for riders scrolling social
media or working on their commute, this isn’t just about better Wi-Fi
for passengers. The same intercity rail operator is using Starlink’s
network to transform its onboard operations, from real-time video
surveillance—which can be used to detect lost luggage, violence or
weapons—to integrated point-of-sale systems for seamless transactions.
But while LEO technology is exciting, it is not a silver bullet.
Satellites will be beneficial in remote areas where cellular or
trackside networks take more time and cost to deploy. But in urban
environments where reliable cellular connectivity is already widely
available, it often won’t make sense to rely solely on satellites.
That’s why it’s vital to understand the connectivity along the entirety
of a route so operators can deploy the right connectivity in the right
way at the right points. LEO technology should form part of a wider
connectivity strategy.
The transit industry is currently in a sweet spot where new
technologies such as 5G, Wi-Fi 7 and LEO satellites are all becoming
widely available. Together, they’re creating a fully digital train
environment that is safer, smarter and more efficient for passengers and
operators. Even in crowded trains, we’re seeing optimal performance,
helped by further advancements in next-generation access points
leveraging Wi-Fi 7 and onboard routers with more processing power at the
network edge.
Passengers zipping through the countryside will soon be able to
screenshare with their remote team or have a family call with zero
interruptions. By delivering that strong connectivity everywhere along a
route, rail leaders will be able to attract people out of their cars
and off planes, and onto trains. It’s a vision worthy of the stars.
About the Author
Gabriel J. Lopez-Bernal, President of Icomera’s
North America region, brings 20 years of transportation engineering
experience with a focus on wireless communications in a mobile
environment. His dedication to advancing sustainable technology
investments positions him as a key advisor.Contact him at gabriel.lopez-bernal@icomera.com.
AST SpaceMobile Achieves Major Milestone with First Satellite Video Call Using Standard Smartphones
In a significant breakthrough for global connectivity, AST SpaceMobile has successfully demonstrated the world's first video call between unmodified smartphones using its constellation of BlueBird satellites. The historic test, conducted in partnership with Vodafone in the UK, connected a standard smartphone from a remote location in Wales to Vodafone's CEO through a satellite acting as a cell tower in space.
"This achievement marks a fundamental shift in how we think about mobile coverage," said Abel Avellan, CEO of AST SpaceMobile. "We're proving that everyday smartphones can connect directly to satellites without any special hardware modifications."
The successful test utilized AST's BlueBird satellites, which are designed to deliver peak data transmission speeds of up to 120 Mbps. While the video quality in the demonstration appeared somewhat grainy, the ability to maintain a real-time video connection in a cellular dead zone represents a significant technical achievement.
How AST's Technology Compares to Other Satellite Systems
A recent technical analysis of satellite-to-phone systems reveals why AST SpaceMobile's approach stands out:
- **Superior Link Budget**: Among six major satellite systems analyzed (including Inmarsat, EchoStar, GLOBALSTAR-2, Iridium NEXT, and Lynk), AST SpaceMobile showed the strongest performance in both uplink and downlink capabilities. This is primarily due to its large antenna design and low orbit positioning.
- **Broadband Capability**: While most satellite-to-phone services are limited to text messaging or narrow bandwidth applications, AST's system is currently the only one capable of delivering true broadband speeds directly to standard smartphones.
- **User Equipment**: Unlike traditional satellite systems that require specialized phones or terminals, AST's technology works with any standard 4G/5G smartphone. This significantly reduces barriers to adoption.
- **Coverage Strategy**: The company's approach uses fewer but more capable satellites compared to competitors like Starlink's cellular service, which requires hundreds of satellites but currently only supports text messaging.
AST SpaceMobile plans to expand testing this spring, with commercial service rollout expected to begin in Europe later in 2025 and 2026. The company has secured partnerships with major carriers including Vodafone, AT&T, and Verizon, suggesting broad industry confidence in their technical approach.
AST SpaceMobile Satellites Successfully Power Video Call With Vodafone
Months after launching into orbit, AST SpaceMobile's first BlueBird satellites have successfully powered a video call between two unmodified smartphones on the ground.
US-based
AST tested the technology in the UK with Vodafone, one of its European
partners. Vodafone described it as a "historic first space mobile video
call" and published a video
showing a Vodafone engineer making the video call from a mountainous,
remote region of Wales that lacks traditional cell coverage.
The
call was made on an unmodified consumer smartphone, which connected to
AST's orbiting cluster of five BlueBird satellites, which are designed
to act as a cell tower in space.
The BlueBirds then sent the call
data to a phone belonging to Vodafone Group CEO Margherita Della Valle.
Although the video quality is a bit grainy, the satellites successfully
relayed the data in real-time despite the call coming from a phone in a
cellular dead zone.
Vodafone and AST didn’t reveal much else, like the exact speed of the
satellite internet connection. But the news underscores the growing
competition between AST and SpaceX, which is developing its own
satellite-to-phone technology through the cellular Starlink service.
SpaceX has received
FCC clearance to commercially operate the technology for consumers. The
system currently spans 400+ satellites, but the cellular Starlink
rollout is moving slowly, starting with T-Mobile subscribers who opt
into a free beta program.
In
contrast, AST still has to launch dozens of additional satellites
before it can offer continuous coverage for users on the ground. The
company also needs to secure full FCC approval to commercially operate
the satellite-to-phone service in the US. So far, AST has only received a temporary license to conduct testing with AT&T in the US and Vodafone in Turkiye and the UK.
But in a win for AST, the Vodafone testing shows that the BlueBirds are already capable of powering a video call. AST also demonstrated this feat with its earlier BlueWalker 3 prototype satellite starting back in 2023.
Recommended by Our Editors
SpaceX’s cellular Starlink system, on the other hand, is currently
restricted to SMS text messaging. However, the company plans on adding
support for voice and video calls, along with data downloads, pending regulatory approval. SpaceX’s earlier tests have also shown the technology work on iPhones, Samsung devices, and Pixel phones, achieving download rates of 17Mbps.
As
for AST, it's unclear when the company will start its first beta tests
in the US with AT&T and its other partner, Verizon. But in the
meantime, Vodafone is bullish: “Following further tests this Spring,
Vodafone aims to progressively introduce the direct-to-smartphone
broadband satellite service commercially in markets across Europe later
this year and during 2026 to close the last remaining coverage gaps," it
said.
The BlueBird satellites have been designed for peak data transmission speeds of up to 120Mbps, AST adds.
This is increasingly an area of rivalry between mobile network
operators and the owners of satellite constellations – but not likely to
drive stellar telecoms growth in Europe
Vodafone Group says it has “made the world’s first space video call using normal 4G/5G smartphones and satellites,” using one of AST SpaceMobile’s low-Earth orbit (LEO) satellites.
The video call was made by Rowan Chesmer, an engineer at Vodafone,
from a mountainous location in mid-Wales where there is no terrestrial
mobile network coverage. The call was routed via an AST Bluebird
satellite then sent back to Earth via a “space-to-land” gateway or dish
(pictured) which is connected to Vodafone’s mobile core.
The core platform routed the video call to the standard Pixel
smartphone owned by Vodafone Group’s CEO, Margherita Della Valle, in the
presence of British astronaut Tim Peake.
Vodafone has a 4.6% holding in SpaceMobile worth with a worth
estimated at €285 million last November. The operator group has invested
$60 million (€57.6 million) in total in AST, in three tranches, since
2018. In December 2024, the two entered into a definitive long-term commercial agreement that will run to the end of 2034
Surprising focus on Europe
In a press statement, Della Valle remarked, “Vodafone’s job is to get
everyone connected, no matter where they are. Our advanced European 5G
network will now be complemented with cutting-edge satellite technology.
We are bringing customers the best network and connecting people who
have never had access to mobile communications before.
“This will help to close the digital divide, supporting people from
all corners of Europe to keep in touch with family and friends, or work,
as well as ensuring reliable rural connectivity in an emergency.”
Somewhat curiously, she didn’t mention the potential of
direct-to-smartphone/cell/device services for Africa, where Vodafone has
a large footprint.
Industry analyst Kester Mann, Director of Consumer and Connectivity
at research firm CCS Insight, commented, “Although exciting, the
opportunity for satellite services in Europe is less clear-cut than in
other regions. This is main due to the already strong mobile and fibre
coverage, meaning that the technology will likely only ever fulfil a
complementary role for operators. Places like Africa, Australia, and
India offer greater potential, either in connecting people for the first
time or for people travelling through or into their vast areas that
lack terrestrial coverage.”
Still, Mann acknowledged, “This is a significant milestone for the
burgeoning and increasingly competitive satellite communications sector
which has so far mostly focused on person-to-person and emergency
messaging. Using ‘normal’ smartphones has a clear advantage in
that there is a large existing market for operators like Vodafone to go
after. CCS Insight’s research shows that there are more than 1 billion
smartphones in use in the region that could already work with the
technology.“
Pricing will be the key
Vodafone said it plans to offer “the first commercial
direct-to-smartphone broadband satellite service in Europe from later in
2025 and 2026″. Mann noted, “Offering a commercial service as soon as
later this year is ahead of many people’s expectations. However, no
details have been shared about pricing, which will be the main driver of
take-up. Encouragingly, recent research from CCS Insight shows that
almost half of UK consumers could be willing to pay to make and receive
voice calls or access the Internet over satellite.“
Vodafone makes world’s first space
video call from an area of no coverage using a standard mobile phone and
commercial satellites built to offer a full mobile broadband experience
Rowan
Chesmer, Vodafone engineer, makes historic first space mobile video
call from a remote area of Wales to Margherita Della Valle, Vodafone
Group Chief Executive, using satellites built to offer a full mobile
broadband experience.
Astronaut Tim Peake joined Margherita in
Newbury, UK, for unveiling of first space to land gateway in Europe
which seamlessly connects the satellites with Vodafone’s terrestrial
network.
Only satellite service in the world today that offers mobile broadband directly to multiple normal 4G or 5G smartphones.
Vodafone
aims to offer the first commercial direct-to-smartphone broadband
satellite service in Europe from later in 2025 and 2026
Vodafone
has successfully made the world’s first space video call using normal
4G/5G smartphones and satellites that will allow multiple users in areas
of no mobile coverage to make and receive video calls, access the
Internet and use online messaging services. It is the only satellite
technology of its kind built to offer a full mobile broadband experience
and paves the way for universal digital connectivity and the closure of
mobile coverage gaps.
Unlike today’s satellite-based services,
users do not need a special dish, terminal or expensive satellite phone
to benefit from full mobile broadband connectivity. The service they
will receive mirrors the experience of existing 4G and 5G mobile
networks, enabling them to use everyday smartphones to switch between
space and ground-based networks automatically.
Astronaut Tim Peake
and Margherita Della Valle, Vodafone Group Chief Executive, marked this
significant milestone at Vodafone’s new space-to-land gateway, which
receives and channels all the signals sent from a user’s smartphone via
the BlueBird satellites of Vodafone’s partner, AST SpaceMobile. Vodafone
engineer Rowan Chesmer put it to the test when he made the historic
space-based video call to Margherita from a remote mountainous location
in mid-Wales – where there has never been mobile broadband before.
Rowan, who joined Vodafone’s graduate scheme in 2017, is now developing
cutting-edge satellite technologies that will improve global
connectivity.
Margherita Della Valle said: “Vodafone’s job
is to get everyone connected, no matter where they are. Our advanced
European 5G network will now be complemented with cutting-edge satellite
technology. We are bringing customers the best network and connecting
people who have never had access to mobile communications before. This
will help to close the digital divide, supporting people from all
corners of Europe to keep in touch with family and friends, or work, as
well as ensuring reliable rural connectivity in an emergency.”
Tim
Peake, who in 2015 became the first British astronaut to visit the
International Space Station and conduct a spacewalk, added: “Having
spent six months on the International Space Station, I can fully
appreciate the value in being able to communicate with family and
friends from remote and isolated locations. I am delighted to join
Vodafone and AST SpaceMobile in this significant breakthrough.”
Telecoms Minister, Sir Chris Bryant, said:“Since
coming into office, I have put digital growth and inclusion at the top
of my political agenda, harnessing the power of tech innovation to
connect the most hard-to-reach parts of Britain. I am thrilled to see
Vodafone leveraging satellite connectivity and 5G to help us plug
coverage gaps and improve lives across the country.”
Abel Avellan, Founder, Chairman, and CEO of AST SpaceMobile, said: “This
historic milestone marks another significant step forward in our
partnership with Vodafone, a long-time investor in AST SpaceMobile and a
key technology partner. Together, we have achieved several world firsts
in space-based broadband connectivity, including the first-ever
space-based voice call, the first-ever 4G download speed above 10 Mbps,
and the first-ever 5G voice call. This latest achievement using our
BlueBird satellites, takes us one step closer to our mission to
eliminate connectivity gaps and make cellular broadband accessible to
all.”
Operating from low Earth orbit, it is the only satellite
service in the world today that offers mobile broadband directly to
multiple 4G or 5G smartphones by working seamlessly as an extension of
Vodafone’s leading land-based networks. Satellite is a complementary,
bolt-on technology providing valuable coverage where no feasible mobile
or fixed alternative exists at present. Together, the satellite service
and terrestrial network will give Europe a communications infrastructure
for use in any location, including mountains, or out at sea, at any
time, as well as boosting overall resilience.
Today’s call is a
landmark achievement for Europe in this exciting next technology
frontier. It comes 40 years after Vodafone made the UK’s very first
mobile phone call, when Michael Harrison called his father – Sir Ernest
Harrison, Vodafone’s founder and first chairman – just after midnight on
1 January 1985 from Parliament Square, London.
NOTE TO EDITORS
Rollout plans
Following
further tests this Spring, Vodafone aims to progressively introduce the
direct-to-smartphone broadband satellite service commercially in
markets across Europe later this year and during 2026 to close the last
remaining coverage gaps.
Complementary Technology
Direct-to-mobile
broadband satellite is a fully integrated extension of Vodafone’s
existing land-based fibre and mobile networks, providing reliable
digital connectivity in rural coverage not spots, including vast
stretches of surrounding sea. As a combined package, customers will
benefit from a truly ubiquitous, seamless experience without the need
for physically switching between different technologies or services.
Vodafone investor in AST SpaceMobile
Vodafone
became a lead investor in AST SpaceMobile in 2019 and pioneered
successful trials using its test satellite, including completing the
world’s first space-based 5G voice call.
Now five AST SpaceMobile
satellites, called Bluebird 1 – 5, allow Vodafone to test mobile
broadband connectivity directly to existing smartphones at peak data
transmission speeds of up to 120 Mbps. AST SpaceMobile operates the
first and only mobile broadband network in space that works directly
with standard, unmodified smartphones for multiple users. This goes
beyond other low Earth orbit satellite constellations which have so far
only facilitated text messaging.
For more information on Vodafone space-based mobile networks, please visit our satellite page
About Vodafone Group
Vodafone
is a leading European and African telecoms company. We provide mobile
and fixed services to over 330 million customers in 15 countries,
partner with mobile networks in 47 more and have one of the world’s
largest IoT platforms. In Africa, our financial technology businesses
serve almost 83 million customers across seven countries – managing more
transactions than any other provider.
Our purpose is to connect
for a better future by using technology to improve lives, businesses and
help progress inclusive sustainable societies. We are committed to
reducing our environmental impact to reach net zero emissions by 2040.
AST
SpaceMobile is building the first and only global cellular broadband
network in space to operate directly with standard, unmodified mobile
devices based on our extensive IP and patent portfolio, and designed for
both commercial and government applications. Our engineers and space
scientists are on a mission to eliminate the connectivity gaps faced by
today’s five billion mobile subscribers and finally bring broadband to
the billions who remain unconnected. For more information, follow AST
SpaceMobile on YouTube, X (Formerly Twitter), LinkedIn and Facebook. Watch this video for an overview of the SpaceMobile mission.
AST SpaceMobile and Vodafone sign long-term deal - Mobile Europe
The long-term partners entered into a definitive long-term commercial agreement through 2034
Space-based cellular broadband network builder AST SpaceMobile has
entered into a definitive long-term commercial agreement with Vodafone
Group that runs through to 2034. Since 2018, Vodafone has been a
three-time investor in AST SpaceMobile, and is a key technology partner
in AST SpaceMobile’s development, including several world’s firsts in
direct-to-device connectivity with everyday smartphones that confirmed
2G, 4G and 5G capabilities.
This agreement establishes the framework for Vodafone to offer
space-based cellular broadband connectivity in its home markets, as well
as to other operators via its Partner Markets program.
AST SpaceMobile’s tie-up with Vodafone follows a six-year deal in
June with AT&T to provide space-based broadband services, which was
quickly followed by a strategic partnership with Verizon. With the size
of the backers, it helps the satellite company push through with its
crazy-large array BlueBird satellites which would otherwise be deemed a
fairly risky approach to building a space-based mobile network. On the
other hand, the attractiveness of the subsequent service it will provide
is centred on the fact you can use unmodified mobile handsets.
In April 2023, AST SpaceMobile and its partners completed the
first-ever space-based voice call to an unmodified phone. That was
followed a 4G download speed above 10 Mbps in June 2023 and a 5G voice
call in September 2023. Ultimately, the company and its partners have
demonstrated over 20 Mbps download speeds to unmodified phones on a 5
MHz channel.
Vodafone has placed an order for its first Block 1 BlueBird gateway,
marking a milestone in the deployment of AST SpaceMobile’s global
network infrastructure. Users outside traditional cellular coverage will
be able to connect their smartphones directly to AST SpaceMobile’s
satellites in low Earth orbit, which in turn will route the data to the
gateway. These gateways will then connect to Vodafone’s existing network
infrastructure to route the broadband data to users’ devices, as well
as to access third-party apps and the internet.
AST SpaceMobile’s next-generation Block 2 BlueBirds featuring up to
2,400 square foot communications arrays, are designed to deliver up to
ten times the bandwidth capacity of the BlueBird satellites in orbit
today, enabling peak data transmission speeds up to 120 Mbps, supporting
voice, full data, and video applications.
During 2024, AST SpaceMobile said it had secured additional strategic
investment from AT&T, Verizon, Google and Vodafone, and new
contract awards with the United States Government, directly and through
prime contractors.
The company has agreements with more than 45 mobile network operators
globally, which have over approximately 2.8 billion existing
subscribers total, including Vodafone Group, AT&T, Verizon, Rakuten
Mobile, Bell Canada, Orange, Telefonica, TIM, Saudi Telecom Company,
Zain KSA, Etisalat, Indosat Ooredoo Hutchison, Telkomsel, Smart
Communications, Globe Telecom, Millicom, Smartfren, Telecom Argentina,
MTN, Telstra, Africell, Liberty Latin America and others. AT&T,
Verizon, Vodafone, Google, Rakuten, American Tower, Cisneros Group and
Bell Canada are also existing investors in AST SpaceMobile.
A video call to space may change mobile coverage forever
By
Bryan M. Wolfe
Published January 30, 2025 9:01 AM
Global telecommunications company Vodafone has successfully tested a
“space video call” using a standard mobile phone and commercial
satellites. It’s an important step towards eliminating mobile coverage
black spots, and the carrier hopes to offer the first commercial
direct-to-smartphone broadband satellite service in the U.K. later this
year, and elsewhere in Europe sometime in 2026. To get here, however,
various obstacles must be overcome.
Why is this new?
In recent years, companies like Apple, Samsung, and T-Mobile
have begun offering satellite communication capabilities for
smartphones and smartwatches. However, this feature is limited to
specific devices and is intended for emergency use only. More
importantly, it only allows users to send text messages to emergency
services in areas without cellular or Wi-Fi coverage.
Vodafone is working to offer a complete mobile broadband experience
for anyone without cellular or Wi-Fi coverage. Its first successful test
came through a video call from a mountain in Ceredigion, west Wales.
The team didn’t call the International Space Station though. Instead,
Vodafone’s call, made in an area without any coverage, connected to a
satellite which then sent it down to the terrestrial network, ready to
connect to another device. The video below shows the call itself.
As Vodafone CEO Margherita Della Valle explains, this service could
eliminate “not spots,” sometimes called “blackspots,” where there’s
currently no coverage.
“It’s a really important moment because we are opening the door to
universal connectivity, to connecting people in the U.K., wherever they
are,” she said.
The British-based Vodafone partnered with satellite company AST SpaceMobile to do the test.
Can this happen?
Despite the company’s claims, Vodafone’s successful test doesn’t necessarily mean it will be available to consumers this year.
As the BBC explains,
Vodafone must overcome key regulatory issues before it can proceed.
Additionally, astronomers warn the increasing number of satellites in
orbit that might be required for direct-to-smartphone broadband
satellite service could make it harder to study space.
There’s also the question of price. To date, Vodafone has not
mentioned what this type of service will cost. Typically, satellite
communication can be expensive, making it cost-prohibitive to some
users.
Other obstacles have less to do with regulations and costs. For
example, satellite connections typically have higher latency and lower
bandwidth than terrestrial networks, affecting video call quality.
Additionally, weather conditions can affect satellite signals,
potentially disrupting video calls.
Why this could be a big deal
Grok
Satellite-enabled smartphone video calls have immense potential to
revolutionize communication, provided that any existing obstacles can be
addressed. One of the most significant advantages is the ability to
bridge the digital divide, ultimately giving everyone access to the
internet. This increased connectivity could promote social inclusion,
stimulate economic development, and improve access to essential services
such as education and healthcare.
Additionally, these capabilities would enable travelers, explorers,
and researchers in remote areas to stay connected with family,
colleagues, and emergency services, enhancing their safety and peace of
mind. Satellite-enabled smartphone video calls could facilitate better
real-time communication in emergencies or disasters. They would allow
for the transmission of visual information about the situation on the
ground, helping emergency responders make informed decisions and
allocate resources effectively.
Vodafone isn’t the only company trying to perfect satellite video communication. In the U.S. T-Mobile is testing a satellite service along the same lines as Vodafone’s, while Apple introduced a satellite messaging feature with the iPhone 14, and MediaTek parterned with Motorola and the (now defunct) Bullitt Group to make the Defy Satellite Link dongle designed for emergency use.
A Technical Comparison of Six Satellite Systems: Suitability for Direct-to-Device Satellite Access
S. Boumard, I. Moilanen, M. Lasanen, T. Suihko and M. Höyhtyä, "A Technical Comparison of Six Satellite Systems: Suitability for Direct-to-Device Satellite Access," 2023 IEEE 9th World Forum on Internet of Things (WF-IoT), Aveiro, Portugal, 2023, pp. 01-06, doi: 10.1109/WF-IoT58464.2023.10539458.
Abstract: This paper analyses the suitability of several satellite systems for direct-to-device connectivity using the 5G New Radio air interface. The selected geostationary satellites and low Earth orbit satellite constellations cover a wide range of systems, namely Inmarsat, EchoStar, GLOBALSTAR-2, Iridium NEXT, Lynk, and AST SpaceMobile. The conducted link power budget assessment shows that depending on the targeted application, several systems are able to achieve adequate performance, especially in the downlink direction, from satellite to terminal. The analysed use cases cover both narrowband use cases such as voice and Internet-of-Things as well as broadband connections. However, direct 5G satellite services are not yet a commercial reality and therefore required technological and regulatory advancements for future developments are discussed. keywords: {Satellite constellations;Satellite antennas;Satellite broadcasting;Low earth orbit satellites;Interference;Downlink;Orbits;Satellite Communications;Direct Satellite-to-Device;handheld devices}, URL: https://ieeexplore.ieee.org/stamp/stamp.jsp?tp=&arnumber=10539458&isnumber=10539375
SECTION I.
Introduction
Direct
satellite-to-device (DS2D) connectivity is the largest market
opportunity in the satellite communications (SatCom) history [1].
Direct connection can make mass use of satellites possible and will
enable the use of satellite connections with regular handheld terminals.
It has been estimated that the number of subscribers could reach 350
million by 2030, contributing to annual revenue above 60B. Companies
such as Apple and Huawei are already providing satellite-based emergency
services on their latest smartphones. Commercial satellite connectivity
for Narrowband Internet-of-Things (NB-IoT) are starting to be
commercially available, e.g. Skylo, using Inmarsat geostationary
satellites, or Sateliot, using low-Earth orbit (LEO) satellites.
Users of existing smartphones are targeted by companies such as AST SpaceMobile and Lynk [2].
In addition, the 3GPP non-terrestrial networking (NTN) specifications
consider direct satellite connectivity feature starting from 3GPP
Release 17. This feature will be specified more in detail in the coming
releases. The NTN evolution in 3GPP has been discussed thoroughly in [3]–[5].
However, careful analysis is needed to find the most cost-efficient
solutions for the satellites to provide the required performance for a
variety of applications. This includes not only studying theoretical
models but also analysing existing satellite system designs for direct
connec-tivity to a wide variety of use cases.
The topic has lately
attracted a lot of interest and there are a few recent related studies
available. A review and comparison of three LEO satellite systems is
presented in [6]
for Telesat's, OneWeb's, and SpaceX's SatCom systems. The systems have
different characteristics and the link power budget analysis presented
in [6]
assumes, e.g., the use of the DVB-S2X standard. However, the comparison
did not consider handheld terminals. Of these systems, SpaceX has
recently taken direct handheld connectivity as a new target [1]. DS2D 5G satellite access was analysed for 5G New Radio (NR) User Equipment (UE) in millimeter waves in [7].
It was identified that with those high frequencies the link power
budgets are very weak and therefore the most potential bands remain
below 6 GHz, frequency range 1 (FR1), due to more favourable propagation
conditions. Besides link power budgets, physical layer enhancements and
adaptations for 5G NR NTN connections are considered in [8],
covering the work done in 3GPP standardization up to Rel. 17. The study
covers issues related to long propagation delays, large Doppler
effects, and moving cells. 5G NR NTN requires, inter alia, updated
synchronization mechanisms compared to legacy 5G NR TN. However, there
are no existing studies that compare the suitability of existing or
planned satellite systems to support DS2D connections apart from [6]. Compared to [6],
we focus on 3GPP based DS2D access and on sub-6 GHz carrier
frequencies, which have different propagation properties, available
bandwidths (BWs), and different regulations. A thorough investigation of
AST SpaceMobile business model, choice of frequency bands, licensing,
and technologies are investigated in [2].
By contrast, we compare several other satellites through link power
budget analysis and discuss possible enhancements to improve them.
Our
goal is to understand what it will take to provide 5G NR DS2D links
using existing or planned satellite systems in FR1, while minimizing the
impact to the devices themselves, meaning minimizing the effect on the
bill of materials (BOM). The targeted devices are handheld 5G NR
devices, for a wide range of potential use cases, including IoT and more
generally Machine-Type Communications (MTC). The link power budgets are
calculated using available public information for the analysed systems.
Aspects related to system design and regulations are also investigated
to provide a wider view on the trade-offs for such systems. The focus is
on sub 6 GHz frequencies and 5G technology but can be extended to any
communication system. The novelty of our paper can be summarized as
follows:
A survey and selection of existing and upcoming potential satellite systems.
Link power budget comparison for selected 6 satellite systems and DS2D connectivity at FR1.
A review of aspects influencing design parameters and possible enhancements of existing systems.
A view on possible developments in this area.
The paper is structured as follows. Section II provides a short survey of existing systems and the selection logic for the satellite systems used for analysis. Section III describes the system model and the link power budget model used for the technical analysis. Section IV is the actual link power budget assessment covering the six selected systems. Section V is the discussion on implications of the results for practical NTN systems and recommendations for future work. Section VI concludes this study.
SECTION II.
Evaluation of Satellite Systems
Current
and upcoming satellite systems are examined to assess the capability of
those systems to provide various services to 5G smartphones or similar
devices. A review of existing or planned satellite systems is first
provided, including Geostationary orbit (GEO) and LEO satellites. Then
six satellite systems are selected for link power budget assessment.
A. Review of Existing Systems
We
first review the frequency allocations to see what limits and rules
exist and which bands are the most interesting when considering
satellite links in 5G FR1. FR1 is defined as the 410 MHz - 7125 MHz
frequency range [9]
but we focus here on the bands below 6 GHz. Some frequency bands
allocated to satellite communications within FR1 have coordination power
flux density (pfd) limits for space stations [10].
These thresholds are soft bounds and the final pfd value can be higher,
depending on the country and the other services needing protection.
These limits can be used to determine if coordination is needed. Some
bands are allocated to Mobile Satellite Services (MSS), between mobile
terrestrial stations and satellites. Most commercial MSS are using
spectrum in the L-band and S-band, between 1.5 and 2.5 GHz.
Specific frequency bands have been selected for the harmonization of MSS around 2 GHz in Europe [11], [12] and in the USA [13]
with complementary ground components (CGCs), called ancillary
terrestrial component (ATC) by the Federal Communications Commission
(FCC) in the USA. Those bands correspond to the 5G NR NTN bands n256
(European MSS-CGC) and n255 (one of the American MSS-ATC bands) [9].
We
have investigated current or planned satellite systems for MSS in 5G
FR1 frequencies, using available public information sources [3], [14]–[16].
Planned satellite systems are included as they give insight into what
the most promising technologies are. There has been a lot of interest
lately to design and test LEO systems to provide direct connectivity
from satellite to smartphones, out of which Lynk and AST SpaceMobile are
the most evolved examples. Due to the page limitation we present only
the selected systems and their characteristics in the following
subsection.
B. Selected Systems
We
selected the most appropriate satellite systems to provide data
communications to and from a 5G handheld terminal. We looked at the age
of the system (discarding too old systems), frequency bands in use
(allocated to MSS or other services), and targeted services for the
selection. Six satellite systems were selected, representing a wide
range of parameters and setups to study different combinations in the
link power budget assessment. Parameters of the systems are presented in
Table I.
Compared to LEO satellites, GEO satellites have longer life, limited
collision risks, and less handovers are needed. On the flip side, LEO
satellites offer better propagation conditions' smaller delays, and
larger throughput, even more so with decreasing altitude and increasing
constellation sizes (number of satellites in the constellation). LEO
satellites are also capable of providing better coverage compared to GEO
satellites (no polar regions). Besides those general aspects, the
selected satellite systems and their specific advantages (+) and
disadvantages (-) are as follows:
1) Inmarsat-6 f2
3GPP n255 band, 3GPP 5G TN bands (n24, n99).
2) Echostar Xxi
Authorized operator for MSS-CGC in Europe, 3GPP n256 band, some partial 3GPP 5G TN bands (n70, n65, n66).
3) Globalstar-2
Big LEO band MSS-ATC (USA), 3GPP 5G TN n53 band. -
Higher altitude w.r.t. other LEO satellites.
4) Iridium Next
Big LEO band MSS-ATC (USA).
TDD and limited overall bandwidth, no 3GPP NR band.
5) Lynk
Designed
for DS2D connectivity, roaming 3GPP NR TN bands from space, satellite
diversity (large constellation planned), close to Earth. -
The band is not for satellite communications (other primary services).
6) Ast Spacemobile
Designed for DS2D connectivity, roaming 3GPP NR TN bands from space. -
The lower band is not for satellite communications (other primary services).
SECTION III.
System Model
The
study focuses on the connection between typical hand-held terminals and
satellites. The links between satellites and between the satellites and
the gateway on the ground are out of scope. Those connections can use
dedicated frequencies and do not suffer from the limitations of handheld
terminals. A basic diagram of the system model is shown in Fig. 1.
Interference between links is not accounted for as it can be mitigated
through, e.g., time-frequency-space resource allocation, and is
out-of-scope of this study. Both narrowband and wideband options are
considered for use cases. The focus is on 5G NR radio interface. The
narrowband case assumes a target data rate of 16 kbits/s. This is a
realistic assumption for e.g. IoT services and voice over NR. For the
wideband case, a data rate of 3.5 Mbits/s is targeted, following public
safety requirements [22].
Fig. 1.
Description of the scenario and the link power budget model.
Table I Selected satellite systems’ parameters for link power budget assessment. e-s stands for earth-to-space and s-e space-to-earth
A. Link Power Budget Model and Assumptions
In
this section, a detailed description of the link power budget analysis
is given. The link power budget assessment evaluates the capabilities of
selected systems to provide direct 5G satellite access for handheld
terminals. Limited transmission power and antenna gain of terminals pose
challenges for reliable communication. For the link power budgets of
all systems, the achievable elevation angle specific carrier-to-noise
ratio CN
values are first calculated. Then the achievable data rates are
estimated. A system is usually designed to provide service for a minimum
elevation angle above which the CN
is large enough. We here choose a minimum elevation angle of 40°, for
which the shadowing effect from the environment is not too severe while
still allowing a reasonable footprint for each satellite. Reducing the
footprint would, e.g., increase the number of needed LEO satellites for
the same service availability.
The uplink (UL) and downlink (DL) carrier-to-noise (CN) ratios in decibels can be expressed as
View Source
where EIRPUE,Ltot,(GT)sat ,K,Bn,EIRPsat,GUE,Pn,UE and NFUE
are the effective isotropic radiated power of UE, total loss in the
signal path, satellite antenna power gain-to-system noise temperature
ratio, Boltzmann constant, noise bandwidth, effective isotropic radiated
power of the satellite, UE antenna gain, UE noise spectral density in a
room temperature, and UE noise figure, respectively.
Spectral efficiency is estimated by using modulation and coding scheme (MCS) specific block error rate vs. CN simulation results for single-input single-output additive white Gaussian noise channel from [18] and Tables 5.1.3.1-1 and 5.1.3.1-2 in [19].
The data rate is calculated for a selected bandwidth. The bandwidths
are multiples of physical resource blocks (PRBs), i.e. 180 kHz. For
instance, data rate of 16 kbits/s can be achieved with a bandwidth of
360 kHz (2 PRBs) when CN≥−6dB, and 3.5 Mbits/s with a bandwidth of 2520 kHz (14 PRBs) when CN≥4dB, respectively. These limits correspond to MCS index 0 and 11 in [19].
Table II Used uplink and downlink loss models for the link power budget assessment.
Table III Terminal characteristics for link power budget assessment.
B. Parameters
The
evaluation requires appropriate loss models and satellites and
terminals specific characteristics, selected based on publicly available
information. The loss models used for UL and DL analysis are listed in Table II. Assumptions for atmospheric loss is based on information found in [20]. In Table II, the loss caused by rain and clouds, which at 6 GHz is quite small, is also included in the atmospheric loss value.
The scanning loss follows cosine characteristics and can be expressed as
Terrestrial
systems typically use linear polarization, while in satellite systems
circular polarization is used. The link power budget assumes that
polarization loss cannot be compensated, neither on the UE nor on the
satellite side. If combining is used in the receiver, CN will increase by a maximum of 3 dB.
The satellite and handheld terminal specific characteristics are shown in Table I and Table III,
respectively. When calculating the free-space loss for satellite links,
the center frequency is determined by adding half of the required
bandwidth to the starting frequency of the band in Table I. The DL transmitted power levels are restricted to comply with the pfd masks in Table I, when available. The impact of the satellite and handheld specific parameters on the results are discussed in Section IV.
SECTION IV.
Link Power Budget Assessment Results for Selected Systems
The link margins for each evaluated satellite system for selected services are shown in Table IV for an elevation angle of 40°. A positive margin indicates how many decibels the calculated CN is above the minimum CN required for the selected service, and a negative margin describes how many decibels CN is below the required CN.
GEU
satellites require high power and antenna gain. The transmitted power
of handheld terminals is limited and the link distance is very long. In
general, the evaluated GEO satellite systems will not reach the positive
link margins for 5G NR UL communication without improvements. However,
it is observed that if the frequency band is narrow enough, positive DL
link margins can be achieved for both GEO satellites. As can be seen
from Table I, Inmarsat operates at lower frequencies than EchoStar, which reduces free space loss. This results in slightly better CN margins in DL, even though Inmarsat's transmission power is slightly lower than EchoStar's. EchoStar XXI has a larger GT value than Inmarsat-6 F2, so its UL CN is greater.
LEO
satellites with large antennas, such as AST Space-Mobile, are promising
candidates for the direct 5G satellite access in both UL and DL
directions. As can be seen from Table IV,
AST SpaceMobile has the highest link margins for UL and DL at both 900
MHz and 2 GHz bands. Based on the link power budget analysis, AST
SpaceMobile is the most promising LEO satellite concept for DS2D
connectivity. Lynk does not have as large an antenna as AST, which is
clearly reflected in lower performance. Lynk's UL margins are negative
for the 3.5 Mbits/s data rate service. Its pfd mask does not allow as
much power as used in AST resulting in lower DL performance. Iridium has
positive UL and DL link margins for all selected scenarios, except for
UL in the wider bands, but the link margins are much lower compared to
AST and Lynk. GLOBALSTAR's UL and DL performance is not sufficient
without improvements.
SECTION V.
Discussions
As
shown in the previous sections, no commercial satellite is currently
able to allow 5G NR broadband services directly to handheld terminals.
AST SpaceMobile is the closest one and successful tests with 4G
connectivity have been conducted. In order to close the CN margins gap, technological enhancements and regulatory changes are needed. Both aspects are discussed in the next subsections.
Lscan(θ)=10log(cos(Nθ)),(3)
View Source
where θ is the scan angle off boresight and N
is a numeric value, typically 1.3, which accounts for the non-ideal
isotropic behaviour embedded element gain. Smaller values of N are used for more ideal antenna patterns. The shadowing model is based on the roadside-tree shadowing model described in [21]. For the frequencies of interest and at an elevation angle of 40°, it varies from 1 to 2 dB.
Table IV CN margins of the evaluated satellite systems for the selected services (elevation angle of 40°, EIRPUE=23DBM shadowing enabled).
A. Technologies
We
argue that there are no major technological hurdles but mostly
regulatory and OPEX/CAPEX stumbling blocks to provide DS2D connectivity.
Large antennas have already been designed and tested in space. Their
costs are also constantly decreasing. Solar panels costs have dropped by
a factor of 5 since 2010 [2].
The use of equipment suppliers for various parts of the systems has
also the potential to reduce costs through increased interoperability
and mass production. AST SpaceMobile, e.g., is using Nokia's products
for ground components and NanoAvionics for its first satellites.
Software-defined payloads are also becoming a reality. Besides the link
power budget improvement, on-board processing in satellites can also
help, e.g., in reducing delay effects due to feed-back loops and
retransmissions. Regenerative payloads will also help integrating
satellite communications with terrestrial networks. Unified jointly
optimized networks is an important goal for 6G [3][4].
These developments may help coordinate the use of frequencies and avoid
possibly harmful interference between terrestrial and non-terrestrial
systems. Modularity trends can also be seen in the phased array antenna
design, made of many identical components. This allows economies of
scale and robustness as the satellite can handle possible damage [2].
An alternative to the large physical antennas, needed to close the link
power budget, is the possible use of formation flying satellites, which
brings cost effectiveness by allowing smaller satellites to form a
large antenna. However, this requires some fine close control of
satellites, which seems still many years away. Very low Earth orbit
satellites (vLEO) are another longer term technology that can help the
link power budget challenge at the cost of larger constellations.
Different use cases may be served by satellite systems as can be seen
from our link power budget analysis results.
At the UE side, the
main technical obstacle for direct satellite access is the poor antenna
performance. Unfortunately, the size and positioning of antennas may be
heavily constrained by the small form factors of the devices. Still,
multi-antenna techniques such as diversity combining, or array
beamforming could improve the received ato some extent even in sub-6 GHz
frequencies. Compensation for polarization loss alone using antenna
diversity or circularly polarized antennas could give up to 3 dB
improvement in the link power budget. Moreover, a 4-element planar
antenna array could theoretically give 6 dB of additional array gain.
Further, Power Class 2 (PC2) would enable 26 dBm output power for
transmission, which may become applicable on the n256 band. The
resulting up to 3 dB improvement in the UL comes with the cost of
increased power consumption and the need for more powerful and
better-quality RF components. If a human is in the loop, auditory and/or
haptic feedback to the user could help in finding an optimized antenna
position and orientation. Anyway, DS2D access can make use of
3GPP-proposed solutions for 5G TN coverage enhancement that play with
waveforms on the time/frequency resource grid [23], and which have been adopted in 3GPP's 5G NR NTN coverage enhancement work.
B. Regulations
Another
aspect to providing DS2D connectivity is allowing MSS satellites to use
larger transmitted power as well as extending the allocation to other
bands. The satellite component of the IMT is recognized as a key element
of IMT [17].
The extension of MSS to other bands in FR1 has also been considered at
the World Radiocommunication Conference (WRC) in 2023, with follow-up
items scheduled for WRC-27.
As NTN systems will start to be
implemented, if the market responds well and more capacity is needed,
rules and regulations will have to adapt. Pfd limits and coexistence
rules may need to be changed. Interference assessment methods between
non-Geosynchronous (NGSO) and other systems are not yet settled in the
ITU-R and are anyway bound to evolve. The efficient use of spectrum
being a goal of the ITU-R, it would make sense to allow satellites to
use terrestrial bands when and where they are underutilized, for example
in rural areas. If the satellite coverage can be controlled e.g.
through beamforming and small cell sizes, co-existence can be realized
in areas where terrestrial bands are underused. Since interference
between systems with moving parts, such as NGSO satellites, are
difficult to assess and regulate, the coordination between terrestrial
and satellite systems within a service should be shifted from regulators
towards the operators who will be integrating those components and then
handling the coexistence by themselves. Letting the operators manage
the coordination between terrestrial and satellite components would be
the most efficient way to use the spectrum. This is what is being done
in the USA with MSS-ATC and in Europe in MSS-CGC in specific bands. This
aspect is also part of the “universal licence” or “unified licence”
concept that has been applied in many countries, e.g. Kenya, Nigeria,
and India. The concept is such that the licence is technology agnostic
and can thus also include satellite connectivity.
SECTION VI.
Conclusions
Direct
satellite connection to handheld terminals using the same radio
interface for both non-terrestrial and terrestrial components is a
promising mass market opportunity. We selected six satellite systems,
designated as Inmarsat, EchoStar, GLOBALSTAR-2, Iridium NEXT, Lynk, and
AST Space-Mobile, and assessed link power budgets to handheld UE
terminals to understand their feasibility in supporting direct
connections for both narrowband and wideband use cases. Most of the
analysed systems are able to support narrowband IoT services both from
LEO and GEO orbits in downlink, from satellite to terminal. The uplink
is more challenging. Limited antenna gain of the device requires
powerful antennas at the satellite side and higher allowed pfd. The only
system capable of providing broadband connection currently is AST
SpaceMobile due to its low orbit and high EIRP.
We have also
discussed the technological and regulatory aspects in relation to the
direct satellite to terminal connec-tivity. Technology is available and
becoming more and more affordable through modularity. Local regulations
are also starting to allow terrestrial and non-terrestrial networks to
co-exist and be managed by operators, which will facilitate interference
management and thus increase spectral efficiency. Interference and
network management are thus very important research topics to realize
direct satellite to handheld connectivity and more generally seamless
connectivity.
The conducted work provides good insights for the
applicability of different types of satellite systems for DS2D
connectivity. However, due to space limitations, the comparative
analysis cannot be comprehensive. Possible extensions include
calculations for a wider range of elevation angles and potential
implications of physical obstacles in the signal path vs. the size of
the satellites constellation.
ACKNOWLEDGMENT
The authors of this paper want to acknowledge
funding from the European Space Agency (ESA), Contract No.:
4000137395/22/UKlND, and support from Stefano Cioni and Damien Roques
for the ESA 5G-COSMO project. We also acknowledge the co-operation with
the project advisory board, with participants from the following
companies: Airbus Defence and Space GmbH (Germany), Airbus Defence and
Space Oy (Finland), Bittium Wireless Ltd (Finland), Inmarsat (UK), Nokia
Solutions and Networks Oy (Finland), Reaktor Innovations Oy (Finland),
Telia Finland Oyj.
