Objectives
The objective of the SATIABLE project is to study the impact of the satellite (GEO, MEO, and LEO), and in general NTNs, in an IAB scenario, envisaging a new topology in which the satellite can be integrated as an IAB-node or an IAB-donor. The study considers the low-level protocols of the 3GPP-NR stack for the access (PHY, MAC, RLC) and for the backhaul (BAP), compliant with 3GPP Rel-17. Furthermore, aspects of the RF component are analysed, taking into account the current specification for the satellite transmissions (i.e., frequency, multiplexing scheme, etc).
Accordingly, new IAB NTN scenarios are proposed, discussed, and finally validated by system-level simulations. An analytical approach is adopted to understand O-RAN required modifications to support satellite-based IAB, supported by formal validation by e.g., UML, sequence diagrams and/or Open Interfaces definition (Swagger/YAML).
Challenges
The integration of the current IAB topology with satellite systems shall face spectrum regulatory aspects with respect to in-band/out-of-band IAB configuration, i.e., the selection of Mobile Satellite Service frequencies matching the New Radio IAB operating bands defined by 3GPP. Accordingly, the interference between satellite transmission and terrestrial infrastructure shall be addressed. A further possible issue is identified in the latency constraints for CU/DU splitting architecture in case of satellite deployments.
Benefits
The satellite can extend the coverage of an NG-RAN to areas not covered by 5G for various reasons (i.e., environmental, economic, emergencies). Due to its wide coverage, it can also reach an IAB-donor more easily by operating in a redundant topology during congestion or link failures in the terrestrial path.
Features
The 5G-Air-Simulator is an open-source project available on the GitHub platform and consists of a C++ code to be executed on a single host machine. The 5G-Air-Simulator functionalities are extended and adapted to simulate an IAB scenario: support to the relaying and BAP layer, TDD and FDD transmissions. The simulation results can be used to reveal whether the satellite can be integrated into the IAB topology and what are the impact on terrestrial communications of neighbouring cells. Furthermore, the adapted simulator can be used for future activities.
System Architecture
The scenario definition and selection activities are critical and shall consider the current state-of-the-art IAB technology and standards, reviewed in the first phase of the project. Figure 1 represents two possible configurations for an “hybrid” NTN-IAB scenario, including the satellite as IAB node (top) or IAB donor (bottom).
The IAB-topology can be modelled in the 5G-Air-Simulation tool, including the satellite link. The simulations are focused on the wireless transmission between:
• UE 🡨🡪 Satellite-node (RLC connectivity)
• Satellite-node 🡨🡪 Donor (BAP/RLC connectivity)
• UE 🡨🡪 Satellite-donor (PDCP connectivity).
Current Status
The project has successfully kicked off in February 2023 and it was completed in September 2024.
Definitively, SATIABLE project has first investigated the state-of-the-art of both the IAB technology and the 5G NTN. Then possible technological adaptations are evaluated both at the protocol stack level (i.e., frequency selection, transmission and interference management, timers extension, etc.) and at the system level (i.e., orbital plane selection, IAB network topology, design of the on-board payload, duplexing scheme, routing, architecture definition).
The study was validated by system- and link-level simulations developing a simulator which implements the various functional blocks of the IAB system, mapped to a satellite scenario.
Up-to-date as of 18/11/2024.
