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 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.
Vodafone claims first video call between LEO satellite and smart phone - Mobile Europe
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.
For more information, please visit www.vodafone.com follow us on X at @VodafoneGroup or connect with us on LinkedIn at www.linkedin.com/company/vodafone.
About AST SpaceMobile
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.
Don’t forget Kuiper
Vodafone is not putting all of its eggs in the AST SpaceMobile basket having signed Amazon’s Project Kuiper as LEO partner in September 2023 with Vodacom. Vodafone was Amazon’s second big telco partner after Verizon went early, signing a deal in 2021. But the ties to AST run deep given Vodafone Group’s former CTO Johan Wibergh has joined AST SpaceMobile’s board of directors in June and Kuiper is still a long way off.
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
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
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
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.
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).
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].
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
The uplink (UL) and downlink (DL) carrier-to-noise
where Spectral efficiency is estimated by using modulation and coding scheme (MCS) specific block error rate vs.
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,
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.
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
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
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.
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
where 
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.
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.
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