The overall system concept foresees a common gateway uplink as a basis with the joint transmission of typically 4 carriers per transponder. This transmission scenario is considered in the context of HTS systems, where a multi-carrier per transponder uplink is performed from a single gateway. A fully functional demonstrator transmitting 4 carriers is also implemented and tested in the lab as well as over satellite in the context of this project.
For this demonstrator implementation, different approaches to the pre-distortion of multi-carrier signals are considered. These include data symbol based as well as signal based pre-distortion approaches. Preceding ESA ARTES studies (e.g., APEXX and BEAMSAT) conducted for both approaches showed promising results for non-linear satellite channels. However, the performance over linearized satellite channels was poor. From these different approaches to the multi-carrier pre-distortion, the MCPRED project evaluates and improves the most efficient techniques for the practical usage in a multi-carrier pre-distortion environment considering both data and signal pre-distortion techniques on the transmitter side.
On the reception side, the overall system gain is evaluated in the context of simple and advanced receivers. We implement here a reference receiver based on symbol based equalization as a current reference receiver and evaluate in a second receiver model the possibility to introduce a fractionally spaced equalization (FSE) as well as non-linear post compensation (NLPC) at the reception side as well. The aim is to evaluate the pre-distortion techniques under different receiver models and to evaluate to which extent the pre-distortion gains can be achieved as well with receiver side techniques.
In the following figures, the basic building blocks of the transmitter side and receiver side considered pre-distortion techniques are outlined. The specific building blocks implemented in this project for data and signal based digital pre-distortion (DPD) on the transmitter side as well as nonlinear post compensation (NLPC) and fractionally spaced equalization (FSE) on the receiver side are highlighted in the block diagrams.
A thorough evaluation of the considered pre-distortion and equalization techniques is performed over different transponder models, linearized and non-linearized TWTA models and different IMUX and OMUX filter types. The aim is to evaluate in a comprehensive and practical manner the potential techniques that can be used with a robust manner.
The laboratory validation testbed architecture and setup are illustrated in the figures below:
The field validation testbed architecture and setup are illustrated in the figures below:
In particular, the field validation campaign was successfully conducted at SES’s premises in Betzdorf, Luxembourg, using the linearized SES’s ASTRA 3B in-orbit transponder “3.011” (GEO, 23.5º East, L-TWTA, Ku-band, 36 MHz, FSS) and the RF uplink and downlink ground stations located into the SES’s teleport in Betzdorf, Luxembourg.