1,863 research outputs found
Applying autonomy to distributed satellite systems: Trends, challenges, and future prospects
While monolithic satellite missions still pose significant advantages in terms of accuracy and
operations, novel distributed architectures are promising improved flexibility, responsiveness,
and adaptability to structural and functional changes. Large satellite swarms, opportunistic satellite
networks or heterogeneous constellations hybridizing small-spacecraft nodes with highperformance
satellites are becoming feasible and advantageous alternatives requiring the adoption
of new operation paradigms that enhance their autonomy. While autonomy is a notion that
is gaining acceptance in monolithic satellite missions, it can also be deemed an integral characteristic
in Distributed Satellite Systems (DSS). In this context, this paper focuses on the motivations
for system-level autonomy in DSS and justifies its need as an enabler of system qualities. Autonomy
is also presented as a necessary feature to bring new distributed Earth observation functions
(which require coordination and collaboration mechanisms) and to allow for novel structural
functions (e.g., opportunistic coalitions, exchange of resources, or in-orbit data services). Mission
Planning and Scheduling (MPS) frameworks are then presented as a key component to implement
autonomous operations in satellite missions. An exhaustive knowledge classification explores the
design aspects of MPS for DSS, and conceptually groups them into: components and organizational
paradigms; problem modeling and representation; optimization techniques and metaheuristics;
execution and runtime characteristics and the notions of tasks, resources, and constraints.
This paper concludes by proposing future strands of work devoted to study the trade-offs of
autonomy in large-scale, highly dynamic and heterogeneous networks through frameworks that
consider some of the limitations of small spacecraft technologies.Postprint (author's final draft
Stochastic Analysis of Satellite Broadband by Mega-Constellations with Inclined LEOs
As emerging massive constellations are intended to provide seamless
connectivity for remote areas using hundreds of small low Earth orbit (LEO)
satellites, new methodologies have great importance to study the performance of
these networks. In this paper, we derive both downlink and uplink analytical
expressions for coverage probability and data rate of an inclined LEO
constellation under general fading, regardless of exact satellites' positions.
Our solution involves two phases as we, first, abstract the network into a
uniformly distributed network. Secondly, we obtain a new parameter, effective
number of satellites, for every user's latitude which compensates for the
performance mismatch between the actual and uniform constellations. In addition
to exact derivation of the network performance metrics, this study provides
insight into selecting the constellation parameters, e.g., the total number of
satellites, altitude, and inclination angle.Comment: Accepted in the 31st International Symposium on Personal, Indoor and
Mobile Radio Communications (PIMRC) 202
Availability, outage, and capacity of spatially correlated, Australasian free-space optical networks
Network capacity and reliability for free space optical communication (FSOC)
is strongly driven by ground station availability, dominated by local cloud
cover causing an outage, and how availability relations between stations
produce network diversity. We combine remote sensing data and novel methods to
provide a generalised framework for assessing and optimising optical ground
station networks. This work is guided by an example network of eight Australian
and New Zealand optical communication ground stations which would span
approximately in longitude and in latitude. Utilising
time-dependent cloud cover data from five satellites, we present a detailed
analysis determining the availability and diversity of the network, finding the
Australasian region is well-suited for an optical network with a 69% average
site availability and low spatial cloud cover correlations. Employing methods
from computational neuroscience, we provide a Monte Carlo method for sampling
the joint probability distribution of site availabilities for an arbitrarily
sized and point-wise correlated network of ground stations. Furthermore, we
develop a general heuristic for site selection under availability and
correlation optimisations, and combine this with orbital propagation
simulations to compare the data capacity between optimised networks and the
example network. We show that the example network may be capable of providing
tens of terabits per day to a LEO satellite, and up to 99.97% reliability to
GEO satellites. We therefore use the Australasian region to demonstrate novel,
generalised tools for assessing and optimising FSOC ground station networks,
and additionally, the suitability of the region for hosting such a network.Comment: Accepted in Journal of Optical Communications and Networking. 16
pages, 16 figure
ESA personal communications and digital audio broadcasting systems based on non-geostationary satellites
Personal Communications and Digital Audio Broadcasting are two new services that the European Space Agency (ESA) is investigating for future European and Global Mobile Satellite systems. ESA is active in promoting these services in their various mission options including non-geostationary and geostationary satellite systems. A Medium Altitude Global Satellite System (MAGSS) for global personal communications at L and S-band, and a Multiregional Highly inclined Elliptical Orbit (M-HEO) system for multiregional digital audio broadcasting at L-band are described. Both systems are being investigated by ESA in the context of future programs, such as Archimedes, which are intended to demonstrate the new services and to develop the technology for future non-geostationary mobile communication and broadcasting satellites
Interference analysis of broadband space and terrestrial fixed radio communications systems in the frequency range 12 to 30 GHz
This thesis presents research into the principles of spectrum sharing analysis
methods developed for investigating implications of interference from
Nongeostationary Fixed Satellite Service (NGSO FSS) systems into Geostationary
Fixed Satellite Service (GSO FSS) systems and Fixed Service (FS) terrestrial radio
systems operating or planned for operation in the 12 to 30 GHz frequency range.
Spectrum sharing is an effective way of allowing new services to operate without
cancelling the existing allocations in the same part of the spectrum. The use of
spectrum sharing results in re-use of the available spectrum among different services
and, therefore, increases the efficient use of the radio frequencies. However, it is
necessary to carry out extensive feasibility studies into technical or operational
compatibility between the services involved. Often, sharing constraints are placed
on systems, such as the power of emissions and the transmitter and receiver antenna
pointings to reduce the interference into negligible levels.
Traditionally, radio spectrum allocated to GSO FSS has been shared with FS. In
recent years, there has been a growing interest in the use of low Earth orbits and a
number of NGSO FSS constellations has been designed to provide broadband data
services. This has led to the allocation of certain bands used by the FS and GSO
FSS systems to NGSO FSS.
In line with the new allocations, NGSO FSS, GSO FSS and FS systems are required
to co-exist in parts of the 12 to 30 GHz frequency range. The primary objectives of
this research were to identify principal factors affecting the feasibility of spectrum
sharing and to develop spectrum sharing analysis methodologies to examine the
implications of these factors with a view to identifying sharing constraints that
would give rise to an acceptable sharing environment
A Comprehensive Survey on Orbital Edge Computing: Systems, Applications, and Algorithms
The number of satellites, especially those operating in low-earth orbit
(LEO), is exploding in recent years. Additionally, the use of COTS hardware
into those satellites enables a new paradigm of computing: orbital edge
computing (OEC). OEC entails more technically advanced steps compared to
single-satellite computing. This feature allows for vast design spaces with
multiple parameters, rendering several novel approaches feasible. The mobility
of LEO satellites in the network and limited resources of communication,
computation, and storage make it challenging to design an appropriate
scheduling algorithm for specific tasks in comparison to traditional
ground-based edge computing. This article comprehensively surveys the
significant areas of focus in orbital edge computing, which include protocol
optimization, mobility management, and resource allocation. This article
provides the first comprehensive survey of OEC. Previous survey papers have
only concentrated on ground-based edge computing or the integration of space
and ground technologies. This article presents a review of recent research from
2000 to 2023 on orbital edge computing that covers network design, computation
offloading, resource allocation, performance analysis, and optimization.
Moreover, having discussed several related works, both technological challenges
and future directions are highlighted in the field.Comment: 18 pages, 9 figures and 5 table
Network Characteristics of LEO Satellite Constellations: A Starlink-Based Measurement from End Users
Low Earth orbit Satellite Networks (LSNs) have been advocated as a key
infrastructure for truly global coverage in the forthcoming 6G. This paper
presents our initial measurement results and observations on the end-to-end
network characteristics of Starlink, arguably the largest LSN constellation to
date. Our findings confirm that LSNs are a promising solution towards
ubiquitous Internet coverage over the Earth; yet, we also find that the users
of Starlink experience much more dynamics in throughput and latency than
terrestrial network users, and even frequent outages. Its user experiences are
heavily affected by environmental factors such as terrain, solar storms, rain,
clouds, and temperature, so is the power consumption. We further analyze
Starlink's current bent-pipe relay strategy and its limits, particularly for
cross-ocean routes. We have also explored its mobility and portability
potentials, and extended our experiments from urban cities to wild remote areas
that are facing distinct practical and cultural challenges.Comment: 12 pages, 20 figures, to be published in IEEE INFOCOM 202
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