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StatusCompleted
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Status date2025-11-25
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Activity Code6B.047
Precoding techniques have demonstrated a significant increase in the throughput of VHTS. The best performance can be obtained when there is only one central entity in the network in charge of precoding all user carriers. This architecture fits particularly well within a centralised gateway concept, where all digital baseband processes are implemented in a remote server connected via high-speed fibres to the distributed remote gateways responsible for the downlink and uplink of the satellite radio frequency signals. In this project, a centralised gateway for a broadband satellite network is prototyped to validate the concept and identify the main technical challenges of such multi-GW environment.
The central GW is connected via high-speed fibres to the distributed remote gateways responsible for the downlink and uplink of the satellite radio frequency. This architecture faces a number of technical issues: (i) differential propagation delay caused by the fact that the propagation distance between the different GW may differ; (ii) differential Doppler caused by the small movements of the geostationary satellite when seen from different GWs; and (iii) the phase noise introduced by different local oscillators operating on each remote GW. These multi-GW impairments are illustrated in the figure below.
The activity demonstrated the feasibility of the centralised broadband GW concept, which is known to provide the best achievable performance within a precoded VHTS system. To achieve this, is important to compensate any time misalignment caused by the differential propagation delay across the multiple remote GWs. Furthermore, differential phase shifts caused by satellite movement (differential Doppler) can have an impact into the precoding performance (mainly due to the outdated CSI used in the precoding calculation). A good compensation loop is needed to tackle the phase issue.
The main outcomes of the activity are two software simulators (a system-level with physical layer abstracted, and a physical-layer focused) as well as a Lab prototype of the so-called centralised GW architecture, suitable for a VHTS networks supporting precoding technique. The system-level simulator has been designed to test different precoding and user scheduling techniques, while the other software simulator and the Lab prototype focused mainly on the study of synchronisation and multi-GW impairments.
The centralised GW concept is illustrated in the figure below for a simple scenario with two remove GWs controlled by a centralized GW.
The project steps have been as follows:
- System scenario definition and requirements
- Multicast precoding and user scheduling design and testing
- Simulator and Prototype design (considering the multi-GW impairments and their mitigation plan).
- Simulator and Prototype development and validation.
- Experimental Campaign.
Project concluded in November 2025.
