Technology Assessment and Experimentation Plan

An assessment is given of the critical and enhancing technologies necessary to build the basic personal terminal (BPT), the supplier, and the Network Management Center (NMC). The experimentation plan for testing the Personal Access Satellite System (PASS) utilizing ACTS is detailed. The experiment plan gives a list of candidate experiments and describes the proposed experimental set-up. ACTS will be used in the Microwave Switch Matrix (MSM) mode. The Microwave Switch Matrix - Link Evaluation Terminal (MSM-LET) at the NASA Lewis Research Center will serve as the microwave front-end for the PASS supplier and the NMC. Link budgets are given for both the forward and return links between the supplier and the basic personal terminal. The equipment required for the experiments is identified

On-board beam generation for multibeam satellite systems

This paper aims at designing an onboard beam generation process for a hybrid onboard on-ground multibeam satellite architecture. The proposed method offers a good tradeoff between total throughput and feeder link bandwidth requirements compared with pure on-ground systems. Full frequency reuse among beams is considered, and the beamforming at the satellite is designed for supporting interference mitigation techniques. In addition, in order to reduce the payload cost and complexity, this onboard beamforming is assumed to be constant and the same for forward and return link transmissions so that the same array-fed reflector can be used for forward and return links, leading to a substantial reduction of the payload mass. To meet all these requirements, a novel robust minimum mean square error optimization is conceived. The benefits of the considered scheme are evaluated with respect to the current approaches both analytically and numerically. Indeed, we show that with the DVB-RCS and DVB-S2 standards, our proposal allows increasing the total throughput within a range between 6% and 15% with respect to other onboard processing techniques in the return and forward link, respectively.Peer ReviewedPostprint (author's final draft

Generalized multicast multibeam precoding for satellite communications

This paper deals with the problem of precoding in multibeam satellite systems. In contrast to general multiuser multiple-input-multiple-output cellular schemes, multibeam satellite architectures suffer from different challenges. First, satellite communications standards embed more than one user in each frame in order to increase the channel coding gain. This leads to the different so-called multigroup multicast models, whose optimization requires computationally complex operations. Second, when the data traffic is generated by several Earth stations (gateways), the precoding matrix must be distributively computed and meet additional payload restrictions. Third, since the feedback channel is adverse (large delay and quantization errors), the precoding must be able to deal with such uncertainties. In order to solve the aforementioned problems, we propose a two-stage precoding design in order to both limit the multibeam interference and to enhance the intra-beam minimum user signal power (i.e., the one that dictates the rate allocation per beam). A robust version of the proposed precoder based on a first perturbation model is presented. This mechanism behaves well when the channel state information is corrupted. Furthermore, we propose a per beam user grouping mechanism together with its robust version in order to increase the precoding gain. Finally, a method for dealing with the multiple gateway architecture is presented, which offers high throughputs with a low inter-gateway communication. The conceived designs are evaluated with a close-to-real beam pattern and the latest broadband communication standard for satellite communications.Peer ReviewedPostprint (updated version

Energy-Efficient On-Board Radio Resource Management for Satellite Communications via Neuromorphic Computing

The latest satellite communication (SatCom) missions are characterized by a fully reconfigurable on-board software-defined payload, capable of adapting radio resources to the temporal and spatial variations of the system traffic. As pure optimization-based solutions have shown to be computationally tedious and to lack flexibility, machine learning (ML)-based methods have emerged as promising alternatives. We investigate the application of energy-efficient brain-inspired ML models for on-board radio resource management. Apart from software simulation, we report extensive experimental results leveraging the recently released Intel Loihi 2 chip. To benchmark the performance of the proposed model, we implement conventional convolutional neural networks (CNN) on a Xilinx Versal VCK5000, and provide a detailed comparison of accuracy, precision, recall, and energy efficiency for different traffic demands. Most notably, for relevant workloads, spiking neural networks (SNNs) implemented on Loihi 2 yield higher accuracy, while reducing power consumption by more than 100$\times$ as compared to the CNN-based reference platform. Our findings point to the significant potential of neuromorphic computing and SNNs in supporting on-board SatCom operations, paving the way for enhanced efficiency and sustainability in future SatCom systems.Comment: currently under review at IEEE Transactions on Machine Learning in Communications and Networkin

Chapter Antennas for Space Applications: A Review

It is well known that antennas are inevitable for wireless communication systems. After the launch of Sputnik-1 which was the first artificial satellite developed by USSR (Union of Soviet Socialist Republics), telecommunication technologies started to develop for space excessively. However, significance of the antennas as first or final RF-front end element has not been altered for the space communication systems. In this chapter, after introducing telecommunication and antenna technologies for space, which space environmental conditions are to be faced by these antennas are summarized. Then, frequency allocation that is a crucial design factor for antennas is explained and tabulated. And finally at the last part, different types of antennas used in different space missions are presented with their functional parameters and tasks

Future benefits and applications of intelligent on-board processing to VSAT services

The trends and roles of VSAT services in the year 2010 time frame are examined based on an overall network and service model for that period. An estimate of the VSAT traffic is then made and the service and general network requirements are identified. In order to accommodate these traffic needs, four satellite VSAT architectures based on the use of fixed or scanning multibeam antennas in conjunction with IF switching or onboard regeneration and baseband processing are suggested. The performance of each of these architectures is assessed and the key enabling technologies are identified

Joint optimization of beam-hopping design and NOMA-assisted transmission for flexible satellite systems

Next-generation satellite systems require more flexibility in resource management such that available radio resources can be dynamically allocated to meet time-varying and non-uniform traffic demands. Considering potential benefits of beam hopping (BH) and non-orthogonal multiple access (NOMA), we exploit the time-domain flexibility in multi-beam satellite systems by optimizing BH design, and enhance the power-domain flexibility via NOMA. In this paper, we investigate the synergy and mutual influence of beam hopping and NOMA. We jointly optimize power allocation, beam scheduling, and terminal-timeslot assignment to minimize the gap between requested traffic demand and offered capacity. In the solution development, we formally prove the NP-hardness of the optimization problem. Next, we develop a bounding scheme to tightly gauge the global optimum and propose a suboptimal algorithm to enable efficient resource assignment. Numerical results demonstrate the benefits of combining NOMA and BH, and validate the superiority of the proposed BH-NOMA schemes over benchmarks.This work was supported in part by the Luxembourg National Research Fund (FNR) CORE projects ROSETTA (under grant C17/IS/11632107) and FlexSAT (under grant C19/IS/13696663).Peer ReviewedPostprint (published version

Technology for large space systems: A special bibliography with indexes (supplement 06)

This bibliography lists 220 reports, articles and other documents introduced into the NASA scientific and technical information system between July 1, 1981 and December 31, 1981. Its purpose is to provide helpful information to the researcher, manager, and designer in technology development and mission design in the area of the Large Space Systems Technology (LSST) Program. Subject matter is grouped according to systems, interactive analysis and design, structural concepts, control systems, electronics, advanced materials, assembly concepts, propulsion, solar power satellite systems, and flight experiments