# Distributed Precoding Systems in Multi-Gateway Multibeam Satellites: Regularization and Coarse Beamforming

## TL;DR

This paper proposes a distributed beamforming design for multibeam satellites that uses regularization and channel statistics to optimize precoding across multiple gateways, reducing interference and backhaul communication.

## Contribution

It introduces a regularized MMSE precoding method for multibeam satellites that leverages channel statistics, enabling distributed implementation without extensive backhaul exchange.

## Key findings

- Regularized MMSE precoding improves interference management.
- Channel statistics suffice for effective beamforming design.
- Coarse beamforming network offers practical implementation benefits.

## Abstract

This paper deals with the problem of beamforming design in a multibeam satellite, which is shared by different groups of terminals -clusters-, each served by an Earth station or gateway. Each gateway precodes the symbols addressed to its respective users; the design follows an MMSE criterion, and a regularization factor judiciously chosen allows to account for the presence of mutually interfering clusters, extending more classical results applicable to one centralized station. More importantly, channel statistics can be used instead of instantaneous channel state information, avoiding the exchange of information among gateways through backhaul links. The on-board satellite beamforming weights are designed to exploit the degrees of freedom of the satellite antennas to minimize the noise impact and the interference to some specific users. On-ground beamforming results are provided as a reference to compare the joint performance of MMSE precoders and on-board beamforming network. A non-adaptive design complements the results and makes them more amenable to practical use by designing a coarse beamforming network.