Moshi moshi? Space calling: Rakuten Mobile and AST SpaceMobile achieve Japan first satellite-to-mobile video call

Last week, Rakuten Mobile and AST SpaceMobile took a bold step towards realizing their shared mission of universal connectivity. The two companies conducted Japan’s first-ever mobile broadband video call between two regular smartphones through a low-Earth-orbit satellite.

The milestone signals the start of a new era in Japanese mobile telecommunications. One in which remote areas and disaster zones could stay connected without depending on traditional infrastructure.

A Japan-first phone call

The test demonstrated the first-ever mobile broadband two-way video call in Japan using unmodified smartphones connected directly to satellites. Radio signals were transmitted from Rakuten Mobile’s gateway Earth station in Fukushima Prefecture, north of Tokyo, to one of AST SpaceMobile’s newly launched BlueBird satellites.

From there, the satellite relayed the signal to a smartphone in Tokyo, using a standard calling app on a regular device – no hardware modifications, no special accessories, no satellite mode; just a phone, a satellite and space-age technology.

Rakuten Mobile tested system compatibility across a range of smartphones available in Japan. The company conducted the trial under a preliminary test license and is now seeking approval for a full experimental license for further testing in the near future.

“We are delighted to achieve the first-ever mobile broadband two-way voice call in Japan between a smartphone and satellite, proving this groundbreaking technology once again,” commented Rakuten Group Chairman and CEO Mickey Mikitani. Notably, the technology is compatible with close to all smartphones, regardless of the manufacturer and system, or if it is the latest model or not. “[With the Rakuten Saikyo Satellite Service], since it’s broadband, users can not only send text messages or do voice calls, but can even stream videos, go on social media platforms and make video calls on messenger apps.”

Commercial satellite-to-smartphone services using the system are expected to launch as early as Q4 2026 as the Rakuten Saikyo Satellite Service.

A fruitful partnership

The recent Japan trial is not an isolated achievement, but one item on a growing list of global firsts Rakuten Mobile and AST SpaceMobile have delivered.

The strategic partnership kicked off in March 2020, coinciding with the initial launch of Rakuten Mobile’s full-scale network. In the five years since, as Rakuten Mobile has rapidly expanded operations on the ground, AST SpaceMobile has been busy in the skies above.

In September 2022, the company launched BlueWalker 3, the largest communications array ever deployed to low Earth orbit. Two years later, the company launched its first five commercial BlueBird satellites from Cape Canaveral in Florida.

From zero to 100% geo-coverage

Since its full-scale launch just five years ago, Rakuten Mobile has rapidly expanded its network across Japan to join other local carriers in offering near total population coverage. But geographical coverage is another matter entirely.

“Rakuten Mobile has achieved a population coverage of 99.9%, including roaming services,” said Mikitani in 2024. “For the most part, Japan’s mobile carriers – even with this level of population coverage – only have a geographical coverage of around 70%. That means that 30% of the country does not have connectivity. With AST SpaceMobile, we want to achieve a geographical coverage of 100%.”

Such an achievement would be an incredible turnaround. From the network’s limited coverage in its infancy, Rakuten Mobile is set to become the first Japanese carrier to achieve 100% geographical coverage.

The service will switch automatically to satellite only when a terrestrial signal is unavailable, Mikitani explained: “When using Rakuten Mobile’s regular mobile network, it will of course default to our network on the ground and switch to the satellite network when needed. And we are planning for the switch to be seamless.”

Resilient connectivity in times of disaster

Japan’s difficult topography and vulnerability to natural disasters make a powerful case for pushing resilient connectivity tech forward.

“It can be challenging to extend coverage to remote and mountainous areas due to the difficulties in constructing base stations in these remote places,” Mikitani noted. “Japan is also a country prone to natural disasters and people’s awareness of the effects of climate change and increasingly severe disasters is increasing year by year.”

During emergencies, a resilient network could prove critical. Authorities could concentrate satellite bandwidth on disaster zones, ensuring immediate connectivity without needing to rely on ground towers.

Every corner of the globe

The recent trial marked a Japan first, but Abel Avellan’s ambitions extend far beyond a single country.

“AST SpaceMobile’s journey to connect the unconnected reaches new milestones thanks to the commitment and strength of our strategic partnerships,” he remarked. “These partners, including Rakuten Mobile, believe wholeheartedly in our mission to build the first and only space-based cellular broadband network to eliminate coverage gaps and bridge the digital divide.”

“SpaceMobile will be particularly transformative to the growing US$1 trillion annual global mobile market because it will eliminate the coverage gaps faced by today’s five billion mobile subscribers moving in and out of connectivity every day,” he told journalists at Rakuten Mobile’s launch event in 2020. “It will also help the world’s most under-served communities to access the latest mobile services much sooner than predicted, helping more people to access the digital economy.”

Eyes to the sky from 2026

Rakuten Mobile and AST SpaceMobile plan to commercialize satellite-to-mobile broadband services from 2026. By then, more BlueBird satellites will be in orbit, expanding coverage and improving service quality.

The vision is ambitious: global, seamless, direct-to-device mobile broadband. No new hardware, no coverage gaps, just space-enabled service for millions of customers.

It’s an important milestone in Rakuten’s mission to extend mobile coverage to people and devices across the planet, regardless of where they might be.

“We’re democratizing the mobile industry,” Mikitani declared. “Rakuten Mobile will continue to accelerate this project until we realize a future in which mobile communication is accessible to all.”