Direct-to-Device (D2D)

Device-to-Device (D2D) communications: creating connectivity architecture directly between any device and satellite

Direct-to-Device (D2D) communications via satellite is rapidly transforming from a niche emergency capability into a mainstream enabler of global connectivity. With increasing momentum in the telecommunications and space sectors, D2D is set to become a cornerstone of both 5G and 6G architectures – they will bridge coverage gaps, enhance resilience, and unlock new services directly to everyday devices such as smartphones, wearables, and Internet of Things (IoT) sensors.

Features

• Global ubiquitous coverage with satellite constellations serving even remote areas where cellular connectivity is not feasible.
• Greater integration of terrestrial and non-terrestrial networks into a single comprehensive architecture.
• Wide range of use cases, including emergency messaging and remote broadband access, global roaming, direct-to-IoT communication, and mobility applications across maritime, aviation, and automotive sectors.

Why Direct-to-Device?

Despite significant investments in terrestrial infrastructure, an estimated 2.6 billion people still lack reliable mobile broadband coverage, particularly in rural, remote, and maritime regions. Traditional expansion models are increasingly constrained by cost, geography, and infrastructure availability. D2D over satellite offers an attractive alternative – leveraging space-based assets to extend mobile coverage directly to standard user equipment.

As the demand for ubiquitous, resilient, and cost-effective connectivity intensifies, D2D has emerged as a practical and scalable solution to reach users beyond the limits of terrestrial networks. At the same time, non-terrestrial connectivity architectures have evolved in a direction that favours convergence with ground networks – particularly the pivot to medium and low Earth orbit (LEO) and with less reliance on geostationary orbit as a base for telecommunications constellations. There is also the shift from a limited number of large satellites to many small satellites.

ESA’s role in Direct-to-Device

The European Space Agency (ESA) plays a pivotal role in enabling the emergence and acceleration of D2D satellite communications. With a mandate to support space-enabled innovation for both industry and society, ESA fosters the development, validation, and deployment of advanced non-terrestrial network technologies, particularly those that bridge the gap between the satellite and mobile sectors.

Through its Advanced Research in Telecommunications Systems (ARTES) programme, and specifically through the Space for 5G/6G and Sustainable Connectivity programme, ESA co-funds research and development activities with European industry to de-risk technical developments and accelerate time-to-market. We support technical innovation, industrial competitiveness, and the integration of non-terrestrial systems into next-generation networks. Our facilities, funding mechanisms, and strategic partnerships – including our 5G/6G Hub based at ESA’s European Centre for Space Applications and Telecommunications (ECSAT) on the Harwell Science and Innovation Campus – offer a platform for collaboration across sectors and across borders.

ESA supports the entire innovation value chain for non-terrestrial networks and D2D, from early-stage concepts to near-commercial pilots:

• System studies and architecture design
• Chipset and terminal development
• Payload and satellite system adaptation for direct handset communication
• End-to-end integration and testing with 5G/6G core and radio networks

ESA’s goal is to ensure that European capabilities remain at the forefront of D2D evolution – both technically and commercially. ESA is actively inviting:

• Satellite operators to define payload and beam requirements for D2D
• Chipset and device manufacturers to integrate and test D2D features
• Satellite Network Operators, Mobile Network Operators (MNOs) and infrastructure vendors to support hybrid terrestrial and non-terrestrial network integration
• Startups and Small and Medium-sized Enterprises to explore niche applications and rapid deployment use cases
• Regulatory bodies to participate in spectrum and safety alignment

D2D applications and use cases 

D2D connectivity via satellite unlocks a wide range of impactful applications, from lifesaving emergency communications to broadband access in remote regions, and industrial grade IoT services.s

These use cases reflect a growing need for ubiquity, mobility, and resilience – needs that cannot be fully met by terrestrial infrastructure alone, and include:

• Communications for emergencies and public safety
• Remote and rural broadband
• Connectivity for maritime, aviation, rail and automotive 
• IoT and machine-type communications
• Communications support for security and governmental use 

White paper