As the transition toward 6G accelerates, the industry is confronting a structural challenge: how to extend connectivity to truly global scale, across rural regions, oceans, and airspace, without exponentially increasing energy consumption and infrastructure costs. Conventional approaches based on densifying terrestrial networks are reaching their limits. Covering the remaining 55% of the Earth’s landmass with ground infrastructure alone is not only economically prohibitive but also environmentally unsustainable. The ETHER project addresses this challenge by rethinking network design from first principles, placing sustainability at the core of a 3D integrated terrestrial–non-terrestrial (TN–NTN) architecture.
Rather than treating satellites as a complementary overlay, as is largely the case in current 5G and early 6G research, ETHER advances the state of the art by modelling connectivity as a fully integrated, multi-layered system spanning ground, aerial, and space segments, orchestrated dynamically based on service requirements. Techno-economic analysis, performed by Aristotle University of Thessaloniki (AUTH), has demonstrated that optimal deployment strategies are inherently heterogeneous: terrestrial networks remain efficient for high-capacity urban demand, while Low Earth Orbit (LEO) constellations provide superior cost- and energy-efficiency for wide-area and delay-tolerant services. This hybridisation not only improves performance but enables a system-level optimisation of energy and cost that goes beyond current single-domain network planning approaches.
A key innovation underpinning this efficiency is ETHER’s semantics-aware communication framework, developed through collaboration between i2CAT, Ubiwhere, and Linköping University. While traditional networks optimise throughput and latency at the bit level, ETHER introduces a shift toward information-centric communication, where only contextually relevant data is transmitted. This goes beyond the state of the art in IoT networking by embedding intelligence directly into the communication process, reducing both the unnecessary generation and transmissions of packets and significantly lowering device and network energy consumption, particularly in massive Machine-Type Communication (mMTC) scenarios.
On the infrastructure side, ETHER introduces software-defined, FPGA-based flexible payloads for LEO satellites, with contributions from i2CAT, NCSRD Demokritos, and Sateliot. Unlike conventional satellite systems with fixed functionality, these payloads enable in-orbit reconfiguration and service-aware resource allocation, allowing satellites to dynamically adapt to changing network conditions. This represents a clear step beyond current NTN architectures, where flexibility is limited and services are largely pre-configured. Combined with dynamic spectrum management and power optimisation mechanisms, the system ensures efficient utilisation of both spectral and energy resources across all network layers
Crucially, these capabilities are coordinated through an AI-driven, zero-touch management and orchestration (MANO) framework, with significant contributions from Nearby Computing, AUTH and Net AI. While automation exists in today’s networks, ETHER moves toward fully autonomous, predictive orchestration across heterogeneous domains, integrating terrestrial and non-terrestrial resources into a unified control loop. By leveraging real-time telemetry and AI-based forecasting, the system proactively allocates compute and connectivity resources, avoiding overprovisioning and minimising idle energy consumption. This level of cross-domain intelligence represents a significant advancement over current network management paradigms.
Mobility across TN–NTN environments, historically a source of inefficiency, is also redefined. Through energy-aware vertical and horizontal handover mechanisms, developed by AUTH and i2CAT, and further implemented and validated using NTN channel emulation capabilities by University of Luxembourg, ETHER enables seamless transitions between terrestrial base stations and satellite links. Unlike conventional handover strategies focused primarily on signal strength, ETHER incorporates energy and service-awareness into the decision process, reducing retransmissions, improving reliability, and optimising overall network efficiency.
These innovations have been validated through integrated demonstrations covering delay-tolerant IoT services, direct-to-device satellite connectivity, and safety-critical airspace operations led by Collins Aerospace. The validation activities have been further strengthened through the active involvement of industry partners such as Orange and Avanti Communications, ensuring alignment with real-world deployment scenarios and operational requirements. In each case, ETHER demonstrates that combining AI-driven orchestration, semantic data handling, and flexible infrastructure can deliver high-performance connectivity with significantly improved energy efficiency.
From a policy perspective, ETHER provides a concrete pathway toward achieving ambitious targets such as universal coverage, ultra-high reliability, and reduced carbon footprint. More importantly, it demonstrates that sustainability is not achieved through incremental improvements, but through system-level innovation that goes beyond the current state of the art. In this sense, ETHER does more than advance 6G technologies. It redefines how future networks can be designed to scale responsibly in a resource-constrained world.