D2D (Direct-to-Device) Satellite Programs

Direct-to-Device (D2D) satellite programmes refer to technologies that allow end-user devices, such as ordinary mobile phones, Internet of Things (IoT) sensors, or connected automotive systems, to communicate directly with satellites. Unlike traditional satellite systems, which require ground-based gateways or special equipment, D2D aims to enable communication with unmodified or minimally modified devices by turning satellites into “cell towers in space.” This approach is designed to extend connectivity into regions where terrestrial infrastructure is unavailable, unreliable, or impractical to deploy.

Background and Motivation

Conventional satellite communication has relied on dedicated terminals or large ground stations to relay data. With D2D, the goal is to bypass these intermediate systems, making everyday devices capable of connecting to satellites.
The motivations for D2D programmes include:

• Universal coverage: Providing network access to remote areas, oceans, deserts, and mountain regions.
• Disaster resilience: Maintaining communication during natural disasters or infrastructure failures.
• IoT support: Enabling low-power sensors in agriculture, logistics, and environmental monitoring to connect without local gateways.
• Cost efficiency: Reducing the need for expensive terrestrial infrastructure in sparsely populated regions.
• Commercial potential: Opening new markets for operators, equipment manufacturers, and service providers.

Technical Approaches

Implementing D2D requires overcoming significant technical challenges, as ordinary mobile devices are not designed to communicate with satellites. Several approaches have been developed:

• Use of familiar spectrum bands: Leveraging terrestrial mobile frequency bands or mobile satellite service allocations to ensure compatibility with standard radios.
• Low Earth Orbit (LEO) satellites: Operating at low altitudes reduces latency and path loss, allowing weaker signals from handheld devices to be detected.
• Advanced payloads and beamforming: Satellites use powerful antennas and beam-shaping techniques to optimise connectivity for mobile devices.
• 3GPP Non-Terrestrial Network (NTN) standards: Integration of satellite links into existing 4G/5G protocols ensures interoperability.
• Automatic handover: Devices may switch between terrestrial and satellite networks depending on availability.

Current Programmes and Developments

Several leading programmes have already begun offering or testing D2D services:

• T-Mobile and Starlink (United States): A nationwide service has been launched providing text messaging, location sharing, and emergency fallback features over hundreds of LEO satellites.
• Rogers (Canada): Introduced a beta D2D service using Starlink, with plans to expand through partnerships with multiple satellite operators.
• Lacuna Space: Focused on IoT applications, deploying satellites that connect with low-power devices and sensors for remote monitoring.
• Viasat: Demonstrated D2D technology for the automotive sector, showing applications in connected vehicles.
• Lynk Global: Building a constellation aimed at enabling direct connectivity between standard mobile phones and satellites.

In parallel, regulators are updating spectrum policies and licensing frameworks to accommodate D2D services while ensuring coexistence with terrestrial networks.

Benefits

D2D satellite programmes provide several key benefits:

• Extended global coverage beyond terrestrial networks.
• Continuity of service in emergencies or during network outages.
• Support for IoT and machine-to-machine (M2M) applications in remote industries.
• Reduced infrastructure costs in rural and sparsely populated areas.
• Seamless experience for users, with devices automatically switching between ground and satellite signals.

Challenges and Limitations

Despite their potential, D2D programmes face several constraints:

• Limited capacity due to spectrum availability and shared beams across wide areas.
• Device compatibility issues, as many phones and sensors may require firmware or chipset updates.
• Battery and power constraints, as satellite links demand higher energy use than terrestrial networks.
• Signal obstruction from terrain, foliage, or buildings that block line-of-sight connections.
• Regulatory complexity, since global deployment requires international coordination on frequency usage.
• Economic viability, as early services such as text-only fallback may generate limited revenue.

Outlook and Significance

Direct-to-Device satellite communication represents a transformative development in global connectivity. It complements terrestrial 5G and future 6G networks, ensuring coverage in areas traditionally left unserved. Its applications span disaster management, maritime and aeronautical communication, automotive safety, and remote IoT deployments.