“It’s a satellite terminal that behaves like a mobile phone.”
This is how Robert Bell, executive director of the World Teleport Association (WTA) describes a successful modern-day Earth Station in Motion, or ESIM. “Nobody has to think about where a cell tower is in relationship to their phone, or about its changing relative position when you drive past it in your car,” says Bell.
The term ESIM can be applied generally to any type of vehicle- or vessel-mounted Earth station, now that the rules and regulations for various interpretations of mobile Earth stations have been consolidated under one name. The ESIM now symbolizes the key to continuous and consistent mobile satellite broadband services.
This importance of this consolidation goes beyond just the convenience of defining an ESIM. The world’s leading regulatory agencies have only just recently acknowledged the advancement of satellite antennas and ground systems to a point where changes to Ku- and Ka-band regulations needed to be made.
At its May 2020 open meeting, the FCC further expanded the Ku- and Ka- frequency bands available to ESIMs working with both Geostationary (GEO) and Non-Geostationary (NGSO) satellites that provide communications to ships, vehicles, trains, and aircraft. The Commission also adopted a regulatory framework for ESIMs to communicate with NGSO Fixed-Satellite Service (FSS) satellites in the Ku- and Ka-bands that takes a blanket approach to Earth station licensing instead of an individualized process.
With this second of two draft orders, the FCC was following the ITU’s lead in a similar decision made at the WRC-19 conference. New ESIM rules now more accurately reflect the reality of the situation on the ground, and the technological innovation brought to market by the satellite industry. The previous Ku- and Ka-band regulations that were in place for Earth stations were based on the limits of decades-old mobile satellite ground technology, Ball Aerospace Tactical Solutions Vice President and General Manager Jake Sauer, explains.
“We were once very limited in our ability to communicate with satellites in GEO and our ability to do signal processing and for mobile platforms to receive signals on Earth,” says Sauer. “GEO satellites are tens of thousands of kilometers away from Earth. By the time the GEO signal reaches Earth, you wouldn’t be able to detect unless your ground system knew exactly what kind of signal it was looking for. On top of that, the end-user operating next to you may be radiating a lot of emissions in the same band and jamming you. There had to be a new approach for mobile users to be able to talk to each other.”
Cristi Damian, vice president of business development at Advantech Wireless, explains that GEO satellites can also be less than ideal for constant connectivity when the vehicle covers a broad range of travel. “Ships and planes may require hand-offs between satellites as they move from beam to beam. Presumably, with the proliferation of LEO satellites, ubiquity will be taken up a notch, and seamless transitions between satellites will be less problematic.”
Satellite ground systems have dramatically evolved and advanced in recent years. These systems can now point Radio Frequency (RF) beams up in the sky and utilize digital processing techniques to allow simultaneous beams. There have also been tremendous improvements on the physical form of each component of the ground terminal user equipment.
Advances in modem technology have allowed the maximization of data throughput-efficiency. Amplifier technology has evolved from legacy tube-based products that require fragile tubes and high-voltage power supplies towards much more resilient solid state amplifiers that operate with low-voltage power supplies and are more resistant to damage. Finally, the industry’s gravitation toward higher frequency bands, spot beams, and powerful onboard transmitters allows the transmission of higher volumes of data with smaller antennas.
Damian explains that though antenna technology has evolved, it still remains the biggest challenge that ESIM terminals face. “The difference between fixed ground stations and Earth Stations in Motion lies primarily in the antenna system,” he says. “Though fixed Earth station antennas may be equipped with motorized mounts to track a satellite’s movements, the speed, or slew rate, and range of motion are relatively low. But when the Earth station terminal is moving, the drives on the mount have to be fast and precise for the antenna to stay pointed to a satellite, whether it be operating in GEO or NGSO orbit. The good news is that mobile antennas are typically designed with small, lightweight reflectors so that making them agile is less of a challenge. The bad news is that a small reflector means low gain.”
In addition to reducing or eliminating mechanical systems, Kymeta Chief Scientist Ryan Stevenson adds that today’s advanced ESIMs offer increased reliability and zero maintenance because of all-electronic beam steering antennas and their flat, thin physical profile. “At Kymeta, we’re taking a metamaterials approach to further advance ESIMs by dramatically reducing power consumption and cost compared to other all-electronic approaches, like phased arrays,” he says.
From Sauer’s perspective at Ball Aerospace, the changes that antenna manufacturers are noticing with ESIMs is simply that they enable both military and commercial mobile end users to do things that the mobile satellite market originally set out to do – to maintain a high data-rate link to mobile users with high data-rate demands and create a reliable experience. Sauer adds that ESIMs also push innovation in terminal form factor, with cutting edge antenna systems housed in zero-profile units that become a seamless part of a structure or vessel. “You will mount it on a sun roof and not even notice it’s there,” he says.
What do these technological innovations combined with eased regulatory bandwidth restrictions mean for ESIMs, the mobile market, and the satellite industry as a whole? Stevenson believes that ESIM technology opens up new possibilities for GEO and NGSO satellites by enabling large-volume market opportunities where satellite connectivity typically has not been widely adopted. “A prime example is land-mobile, where both GEO and NGSO satellite constellations will play a key role in the 5G vision of ubiquitous connectivity,” he says.
For the GEO satellite market, Robert Bell believes the highest-priority ESIM applications involve platforms moving across the Earth’s surface while the satellite appears to remain motionless in the sky, where space and form factor are at a premium.
“Those market niches have enormous room to grow,” says Bell. “The more profound question is whether the investment and effort going into realizing the potential of ESIMs – which have significantly underperformed parabolics on a price-performance basis so far – will eventually produce products that out-compete traditional antennas, as smaller disk drives repeatedly out-competed larger ones in Clayton Christensen’s famous ‘Innovators Dilemma’ analysis. It will be a long time coming if it happens, but the impact would be very large, helping to integrate satellite into many more applications.”
Advantech’s Damian says that travelers and mobile end-users’ desire to remain connected can now be met, regardless of the mode of transportation, thanks to the ubiquity of services that satellites offer and to ESIMs ability to communicate with GEO and NSGO spacecraft.
“Well-defined rules and protocols remove ambiguity for manufacturers and help level the playing field,” says Damian. “Once we know the frequency bands, the EIRP [Equivalent Isotropically Radiated Power] levels, the restrictions on interference levels and coverage areas, we can focus on designing these new terminals and networks. However, the task will not be easy, as the ESIM terminals will need to allow control from a centralized NMS [Network Management System] to allow deactivation when interference occurs. We expect that there will be restrictions on mass manufacturing, as legislation will differ from country to country.”
Regardless of the physical and practical improvements that ESIMs represent in mitigating interference, they do not completely eliminate the threat. In fact, ESIMs create new and unique interference issues, and the same regulatory bodies that expanded bandwidth for ESIMs also want to know how developers are addressing these challenges.
Ball Aerospace’s Sauer, however, believes that active arrays help solve some of the most critical and simple interference challenges for ESIMs, “We can now completely, actively control where and how we radiate a signal with an active array,” he says. “With the classic satellite dish design, there was also some signal that would leak out the back and squirt over the sides. With an array that is actively controlled, we can set a requirement that it not radiate emissions, and so mobile users can play better together and not interfere with one another.”
Kymeta’s Stevenson said that ESIMs could create interference when working with GEO signals because they operate in environments where beam-pointing and power spectral density must be carefully controlled. “One challenge that electronically scanned ESIMs present is beam broadening, which is a physical phenomenon associated with all flat-panel, electronically scanned arrays,” he explains. “As the array scans further away from the broadside, the effective aperture area is reduced, resulting in the main beam broadening. At some point in the scan volume of the antenna, the main beam will push up against regulatory limits.”
Kymeta claims it has solved this issue with a proprietary algorithm that controls transmit power within the ESIM terminal. “This ensures that the terminal is always operating within regulatory limits,” says Stevenson. “We have also developed proprietary pointing and tracking algorithms, leveraging cheap, cell-phone grade sensors, to keep the antenna beam pointed to within the required accuracy. For the NGSO environment, our chief concern is Equivalent Power Flux Density [EPFD]. This is not an ESIM concern, per say, but an NGSO and Satellite System Operators concern, which takes into account the aggregate power from a group of terminals in a region.”
Damian and his colleagues at Advantech believe that electronic beam forming should solve ESIM’s interference issues. “So far, limiting the power is the only way to limit interference from ESIM, but that will have a negative effect on the maximum rate of data that can be transmitted, which may have a negative impact on the business case,” says Damian. “A network NMS will be required to monitor a particular group of ESIMs, and to turn them OFF when they enter a protected area, or when they interfere. This will require accurate GPS location, and immunity against GPS jammers for acceptable network security.”
That said, Damian explains that the actual location of ESIM-related assets to be protected from interference is not always in the public domain. “Hence, we could see a lot of customization from country to country, or region to region. Traditional GEO teleports of uplink use CID, so they are fixed, and clearly located. This is not viable for ESIM networks.”
All of the companies mentioned in this feature are working on ESIM solutions for their target markets and planning to roll out next generation systems that take advantage of the new bandwidth regulations.
Ball Aerospace’s Tactical Solutions division has been developing ESIM technology that is government- and military focused, but according to Sauer, the company has played a big role in making that same technology available to the commercial market. “We’re excited about ESIMs. We’ve invested in the technology with our partners in order to drive down the cost of producing ESIMs. That’s our main contribution. It’s a cycle between these two markets. The government and military end-user requirements drive the innovation. For commercial end users, we’ll continue to improve the manufacturing process and enhance capabilities to get ESIMs to the point where it becomes viable for everyone. Right now, we’re integrating our second generation Ku- and Ka- antennas into ESIM terminal solutions. We have already successfully completed demonstrations for these systems in extreme military conditions and environments and have many more demos scheduled over the next few months.”
Kymeta will release the follow-up to its first-generation u7 ESIM, the u8, in the fourth quarter of 2020. “The u8 will extend the bandwidth and efficiency of our ESIM technology while offering hybrid connectivity between satellite and cellular networks. The user now gets the best possible throughput, depending on which network is available,” says Stevenson.
Advantech Wireless already has a range of Solid State Power Amplifiers that are optimized for ESIM applications. “In addition, we have a dedicated research and development team focused on beam forming antennas for integration into ESIM terminals,” Damian adds.
At WTA, Robert Bell represents nearly all of the major manufacturers in the ESIM market. He believes that the actions taken by regulatory organizations to help accelerate the development of ESIMs will also inspire innovation throughout the entire mobile wireless world.
“Any effort to align mobile and satellite standards and regulations is a big step in the right direction for our industry,” says Bell. “In my opinion, the ideal solution that emerges from this is an integrated 4G/5G/ESIM antenna, and a modem that natively supports 4G, 5G, and satellite. Such technology convergence faces a major chicken-or-egg dilemma: Will manufacturers invest in creating such technology before there is demonstrable demand for it? Regulatory action can potentially tilt the decision in favor of such innovation.” VS