Japan's telco operators make steady progress on satellite initiatives

Japanese telco operator KDDI last week signed an agreement with SpaceX to provide satellite-to-cellular service in Japan, starting with SMS text services as early as 2024.

The partnership will leverage SpaceX's Starlink low Earth orbit (LEO) satellites and KDDI national wireless spectrum to connect remote, uncovered areas of Japan that are hard to reach using traditional 4G and 5G networks.

The companies said almost all existing smartphones on KDDI's network will be compatible with the new direct-to-handset service, as it employs the device's existing radio services. After SMS text services, voice and data services will eventually be introduced at an unspecified time.

The satellite-to-cellular service comes eight months after KDDI's first mobile tower powered by Starlink's satellite broadband service went live in Japan.

The telco operator has selected SpaceX's Starlink for backhaul in remote locations across the country. KDDI launched its first satellite-based broadband internet service last December in Hatsushima, an island off the Atami coast in Sagami Bay.

To provide more reliable broadband Internet service to people living in remote locations via Starlink's satellites, reports suggest KDDI will eventually expand its network of remote towers to 1,200.

Bucking the trend

KDDI is not alone in exploring satellite opportunities. All three of its domestic rivals – NTT Docomo, Rakuten Mobile and SoftBank – have their respective satellite initiatives, which puts Japan in rather peculiar territory.

Analysts believe the extent of the opportunity for satellite-based services beyond emergency communications, such as two-way messaging and regular Internet connectivity, is uncertain, especially in advanced markets like Japan with strong mobile networks.

Furthermore, with the third-best "no signal" time globally, Japanese telco operators seem to be unlikely to seek satellite partnerships.

But with partnerships like those between KDDI and SpaceX, Japan is swimming against the tide when integrating satellite communication with mobile cellular networks.

"Across Japan, there remains a need for satellite connectivity to fill in gaps in mobile service," Ian Fogg, vice president for analysis at Opensignal, wrote in a blogpost in January.

"The mountainous and more remote parts of Japan are not the only locations where users may lack a mobile signal. Even in cities users may experience times where there is no cellular service available. In part, this reflects the geography of each urban area — some are compact while others are spread over a wider area encompassing hills or other obstacles," he added.

A slow burn

In recent months, Japanese telco operators have made steady progress on their satellite-to-cellular initiatives that have been in motion for some years.

SoftBank last June started preparations to deliver satellite-based communication service in Japan using OneWeb's constellation, with download data rates of up to 195 Mbit/s.

The planned service is an offshoot of the partnership between two companies that was announced in 2021 about deploying a collection of non-terrestrial network (NTN) connectivity systems worldwide. SoftBank is developing NTN systems using a multi-layered network combining terrestrial mobile networks with LEO, geostationary Earth orbit (GEO) satellites, and high-altitude platform stations (HAPS) in the stratosphere.

It has been reported that OneWeb recently completed its LEO constellation and is on track to deliver global coverage by the end of 2023.

Softbank also inked an agreement in 2021 with Skylo to develop and provide satellite narrowband IoT services in Japan.

From test calls to test flights

In April, Rakuten Mobile and AST SpaceMobile completed what were touted to be the first-ever two-way voice calls directly to unmodified smartphones using the BlueWalker 3 (BW3) satellite. The initial voice call was made from Midland, Texas, area to Rakuten in Japan over AT&T spectrum.

In addition to test calls, AST SpaceMobile engineers conducted compatibility tests on a variety of smartphones and devices. The phones successfully exchanged SIM and network information directly to BW3, which is crucial for delivering broadband connectivity from space to any phone or device. The engineers also measured the strength of smartphone uplink and downlink signal to confirm the ability to support cellular broadband speeds and 4G LTE/5G waveforms.

The test calls happened three years after Rakuten Group and AST SpaceMobile forged a strategic partnership in March 2020 to develop the technology to deliver a space-based mobile service using LEO satellites and Rakuten Mobile spectrum in Japan.

Around the time Rakuten and AST SpaceMobile were conducting their test calls, Space Compass and Airbus subsidiary Aalto HAP signed a contract for a proof of concept (PoC) demonstration flight of the latter's stratospheric drone platform.

Space Compass is a joint venture formed last year between NTT and SKY Perfect JSAT.

The company's contract with Aalto involves building a communications and earth observation service using HAPS starting in Japan as part of Space Compass' 'Space Integrated Computing Network.'

The HAPS element comes from Aalto, which has developed Zephyr, a solar-powered UAS (unmanned aerial system). The satellites come from SKY Perfect JSAT's extensive fleet and the terrestrial elements are provided by NTT Docomo.

The PoC demonstration flight is set for this year with Aalto flying its Zephyr Z8B aircraft equipped with mobile communications to provide a solar-powered tower in the sky. More PoC flights are planned for 2024, with a commercial launch expected at the end of the same year.

The Zephyr will be able to provide 4G/5G mobile connectivity to rural and underserved areas, or when connectivity is temporarily down.

Space Compass' Space Integrated Computing Network is composed of more than HAPS, it also includes a variety of space-based ICT infrastructure, using GEOstationary satellites, LEO satellites, Earth stations, and a data center in space.

Space Compass has teamed up with space communication infrastructure developer Skyloom with plans to launch a GEO data relay service over Asia in 2024, to be expanded globally by 2026. The system will use optical/laser communications terminals and enable GEO satellite direct-to-cloud transfers of data.

Opensignal's Fogg said Japan's telco operators should assess how to approach smartphone satellite services. "Whether they should partner with some of the players involved in announcements to date, expand on their existing relationships for RAN backhaul or IoT to launch their own offering. Or, even whether to seek to expand the reach of their cellular networks in rural areas through more site acquisition or further network sharing agreements. Real-world data on the extent of users' current challenges today can guide these decisions," said Fogg.

An $18 billion market

According to a recent report by ABI Research, the non-terrestrial networks (NTN) mobile market has the potential to reach a market value of at least $18 billion, with up to 200 million connections by 2031. The research firm pointed out that the growing convergence of satellite technology and cellular smartphones has been made possible by integrating NTN connectivity into the 5G cellular ecosystem, as introduced in 3GPP Release-17.

The emergence of satellite-enabled mobile devices from major consumer smartphone manufacturers and chipset makers like Apple, Qualcomm, Motorola, MediaTek, Huawei, and ZTE indicates the upcoming introduction of satellite communications into the mainstream consumer market," said Victor Xu, satellite communications research analyst at ABI Research.

He added that recently announced satellite services will initially prioritize low data rate communications through IoT-NTN technology.

Currently, satellite communication services have mainly focused on specialized emergency services and messaging with low data rates. Still, satellite networks are anticipated to eventually incorporate NR-NTN, a 5G-based, more advanced communication standard, in the next few years.
Integrating NR-NTN will increase capacity and network capabilities, enabling more concurrent users and applications with higher data rates. As a result, new possibilities and use cases for satellite connectivity will emerge.