Description
The objective of the activity is to design, implement and validate signalling and control techniques for satellite user terminals in a non-geostationary satellite network where the user terminals can login and function in the network without necessarily relying on the assistance from global navigation satellite services. Targeted Improvements: Enable autonomous commissioning, login and operation of satellite user terminals within a non-geostationary satellite network without the assistance from GNSS not existing today in ESA member states. Description: The dynamic nature of Non-Geostationary Orbits (NGSO) satellite networks adds a variety of challenges to network operations ranging from user terminal commissioning, terminal login procedure as well as signal tracking and network synchronization. In NGSO satellite networks, it is often assumed that the user terminal is equipped with a Global Navigation Satellite System (GNSS) receiver to maintain an accurate time and frequency reference and remain aware of the user terminal location. While this assumption is valid in some cases, there are several system scenarios that such assumption may not be valid, as described in the following examples. For user terminals with power or energy constraints, the use of always-on GNSS receiver could lead to excessive energy consumption. In other scenarios, the accommodation of additional hardware in particular outdoor antenna for the GNSS receiver may not be possible. The GNSS service may be intentionally or unintentionally jammed by interference. The service may also be partially blocked due to the environment obstacles. In some satellite networks reliance on the third-party services, such as GNSS, may be prohibited or discouraged. This activity aims to investigate GNSS-Independent solutions to perform required signalling steps for satellite user terminal commissioning, login-process and network synchronization. In particular, the following aspects will be investigated: Geo-localize the user terminal based on known identification signature to be transmitted on the uplink and to be received by one or multiple NGSO satellite. Establish means to disseminate NGSO satellite orbital information to user terminals for login process and wake-up procedure. Use precompensation techniques to take into account Doppler shift and Doppler Rates and assists synchronization. Perform time and frequency synchronization at the user terminal based on information received from the satellites.Time delay estimation and precompensation for symbol synchronous access scheme protocols.User terminal signalling and control techniques will be developed, implemented and evaluated in a testbed.