AST SpaceMobile says it makes first satellite-direct-to-phone voice calls

AST SpaceMobile today announced that it completed the first two-way voice calls via satellite-direct-to-phone connections during tests to unmodified cellular devices—a breakthrough claim in the nascent satellite-direct-to-phone arena, which previously has been limited to text-based applications.

Using its BlueWalker 3 low-earth-orbit (LEO) satellite, AST SpaceMobile completed the first satellite-direct-to-phone voice call from Midland, Texas, area—the company is headquartered in Midland—to users of the Rakuten cellular system in Japan, according to an AST SpaceMobile press release. The initial voice call was made using a Samsung Galaxy S22 smartphone, and subsequent voice calls were made using other unmodified smart devices, according to the press release.

This call was executed using 850 MHz Band 5 spectrum licensed to AT&T, which has been supporting AST SpaceMobile’s testing efforts. AST SpaceMobile is conducting tests that leverage the 700 MHz Band 14 spectrum licensed to the FirstNet Authority, but those airwaves were not used in these initial voice-call test, according to information provided to IWCE’s Urgent Communications by an AT&T spokesperson.

Satellite-direct-to-phone technology rapidly has gained momentum in recent years, with several companies declaring their intentions to offer such service commercially. However, the initial tests and offerings—for instance, the emergency service provided by Apple and Globalstar, and the initial commercial service from Lynk Global—have been text-based applications.

Proving that satellite-direct-to-phone technology can support voice communications is a significant technological step, according to AST SpaceMobile Chairman and CEO Abel Avellan (pictured above, making a call).

“Achieving what many once considered impossible, we have reached the most significant milestone to date in our quest to deliver global cellular broadband from space,” Avellan said in a prepared statement.

“While we take a moment to celebrate this tremendous accomplishment, we remain focused on the path ahead and pivotal next steps that get us closer to our goal of transforming the way the world connects. I am immensely proud of our team and our incredible partners, whose unwavering dedication and tireless efforts have brought us to this pivotal moment.”

Indeed, engineers from three of AST SpaceMobile’s key carrier partners—Vodafone, Rakuten and AT&T—participated in the preparation and testing of the first voice calls using the BlueWalker 3 satellite, according to the AST SpaceMobile press release.

“Today, we have taken another major step in mobile communications,” Vodafone Group CEO Margherita Della Valle said in a prepared statement. “30 years after Vodafone sent the world’s first text message, we supported AST SpaceMobile in successfully making the first ever direct-to-smartphone test call using satellite communications.

“This is just the start. As a lead investor in AST SpaceMobile, we will continue to break technological boundaries by connecting many more millions of people across the planet when the service becomes commercially available.”

Rakuten Chairman & CEO Mickey Mikitani echoed this sentiment.

“It was a unique thrill and honor to have the Rakuten team talk with Abel in a world-first direct-to-satellite experience,” Mikitani said in a prepared statement. “Congratulations to AST SpaceMobile and all of its strategic collaborators on this groundbreaking event. As technological advancements like space connectivity become possible with pioneers like AST SpaceMobile, Rakuten will also progress even further along the road to democratizing connectivity for all.”

Chris Sambar, head of AT&T Network, also provided historical context to AST SpaceMobile’s tests of the satellite-direct-to-phone voice calling.

“AT&T’s heritage began with the birth of the telephone 147 years ago and has continued with many other firsts including: trans-continental call, overseas call, call from the moon, and partnering to deliver the only network built with and for America’s first responders,” Sambar said. “We connect people to greater possibility, and this important milestone with AST SpaceMobile is a big step, and we can’t wait to see what’s next in our space-based journey.”

In addition to voice-call tests, AST SpaceMobile engineers conducted initial compatibility tests on a variety of smartphones and devices, according to the company’s press release. The phones successfully exchanged Subscriber Identification Module (“SIM”) and network information directly to BlueWalker 3, which the company claims is “crucial for delivering broadband connectivity from space to any phone or device.”

Other signal-strength tests “confirm the ability to support cellular broadband speeds and 4G LTE / 5G waveforms,” according to the AST SpaceMobile press release.

LEO satellite service is not new to the commercial or critical-communications sectors, as companies like Starlink and OneWeb has been operating for years under a traditional satellite model that requires a special satellite receiver on the ground to access the connectivity offering.

In contrast, satellite-direct-to-phone providers like AST SpaceMobile promise to offer connectivity that is accessible to users via their unmodified cellular devices, with the LEO satellite effectively acting as a “cell tower in space” and the providers of the service acting as a roaming partner to existing carriers.

As a result, AST SpaceMobile does not plan to compete with terrestrial wireless carriers; instead, the company plans to partner with these terrestrial cellular carriers, leveraging their sub-1 GHz spectrum to fill coverage gaps in the carriers’ terrestrial networks.

Of course, AST SpaceMobile is not the only company attempting to provide satellite-direct-to-cell-phone services.

Lynk Global has a similar business model but a different system architecture. While AST SpaceMobile plans to provide cellular broadband service globally with 168 LEO satellites, Lynk plans to deploy thousands of smaller LEO satellites to support eventual broadband connectivity, although its initial offerings will be text-only services.

Lynk also is the first satellite-direct-to-cell-phone company to receive an FCC license for commercial operations, although the license only applies to 10 satellites.

Both Lynk and AST SpaceMobile eventually plan to offer broadband services to users, while many other satellite-direct-to-phone providers are focused on lower-bandwidth applications.

Other significant developments in the satellite-direct-to-cell-phone arena include T-Mobile and SpaceX announcing plans last August to provide connectivity leveraging 1.9 GHz spectrum. Last September, Apple announced that it has teamed with Globalstar to provide an emergency text service—known as Emergency SOS—via satellite that launch in November on 2.4 GHz spectrum for iPhone 14 users.

For the critical-communications industry, satellite-direct-to-phone technology has the potential to address some of the greatest remaining concerns associated with making LTE and 5G “mission-critical-grade” technologies.

Most agree that broadband connectivity via LTE and 5G delivers better performance when connected to a terrestrial network than traditional land-mobile-radio (LMR) systems, but LMR technology has been perceived as superior when terrestrial towers are not available.

This is because LMR systems allow for “graceful degradation” in functionality as terrestrial towers lose their backhaul connections or are unavailable entirely. Even if no LMR network infrastructure is available, LMR users can switch to simplex mode—also known as “direct mode”—and communicate with others within a range of miles in an outdoor setting, depending on the power level of the radio and radio-frequency (RF) propagation environment.

LTE has a direct-mode 3GPP standard known as Proximity Services (ProSe), but it has not gained industry acceptance—no devices being manufactured today offer the capability. While Samsung has proven that ProSe works, the range of the direct-mode technology is not what public-safety users have grown to expect in the LMR world, largely because of the physics associated with using low-power (200 milliwatt) devices and internal antennas.

In contrast, the satellite-direct-to-phone technology—if it works as designed—would allow users to maintain at least a roaming-like experience with their smart devices. This would provide greater system reliability, allow for minimal degradation without user interaction, and support “off-network” communications with infinite range, at least when the user is outdoors.