The objective of the activity is to develop precoding techniques for the forward link of multi-beam LEO satellite systems operatingin full frequency reuse. The activity will target the conventional single-satellite precoding, as well as precoding across adjacentsatellites having beams with overlapping footprints. The developed techniques will be implemented and tested in a software simulator able to assess the performance at both link level and system level. Targeted Improvements: 50% throughput increase compared to a 4-colour reuse scheme. Description: Precoding is nowadays a well-investigated signal processing technique whose benefits have been demonstrated over GEO satellites. It allows a significant increase of the system throughput by reducing the amount of interference between adjacent beams and implementing a full frequency reuse scheme. Real precoding implementations suffer from non-idealities related to imperfect and outdated channel estimation, synchronisation errors, and hardware impairments. However, even under non-ideal conditions, the gain provided by precoding justifies the increasing interest in this technique shown by the satellite industry. Beyond the GEO systems, precoding may also provide gains in some specific LEO scenarios, in particular, when the satellite generates a fixednon-reconfigurable grid of adjacent beams. Under these assumptions, a proper user scheduling becomes fundamental to achieve significant gains in terms of throughput and to limit the waste of resources. Synchronisation and time alignment problems related to LEO constellations are well known, and several solutions have been proposed in the literature. However, these solutions require further refinements to accommodate precoding and scheduling functionalities. Moreover, precoding across adjacent satellites having beams with overlapping footprints also requires coordination between gateways.To address the issues caused by the non-stationary dynamics of LEO satellites, the activity will develop precoding techniques specific for this kind of networks. The selected solutions will be implemented in a software test bed, and their performance assessed and benchmarked against a 4-colour reuse scheme. The simulator will implement all the functionalities of a precoding-based system: synchronisation and collection of the estimated channel state information, precoding-specific smart user-scheduling techniques and modulation-and-coding allocation, computationally efficient calculation of the precoder, and application of the resulting precoder to the vectors of symbol streams to be transmitted by the gateway. Footnote: On Delegation Request activities will only be initiated on the explicit request of at least one National Delegation.

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