5G and Beyond for New Space: Vision and Research Challenges

Abstract

This paper creates a vision for 5G and beyond satellite connectivity and discusses use cases where development is needed. We define a layered architecture for future integrated terrestrial-nonterrestrial networks and discuss what the key communications technologies needed to make the operation reliable and efficient are. We outline research challenges including high frequency bands, spectrum sharing and interference management, optical communications, and network management using software-defined networking principles. Autonomous transport and autonomous satelllites are described both as key drivers behind the development as well as disruptive technologies to fulfil future needs.

Full text

1
5G and Beyond for New Space: Vision and Research
Challenges
Marko Höyhtyä1*, Marius Corici 2, Stefan Covaci3, and Maria Guta4
1VTT Technical Research Centre of Finland Ltd, Kaitoväylä 1, 90590 Oulu, Finland
2Fraunhofer FOKUS, Kaiserin-Allee 31, 10589 Berlin, Germany
3Technical University of Berlin, Strasse des 17 Juni 135, 10635 Berlin, Germany
4European Space Research and Technology Centre (ESTEC), Keplerlaan 1, 2201 AZ Noordwijk, The
Netherlands
*marko.hoyhtya@vtt.fi
Keywords: SOFTWARE-DEFINED SATELLITES, THREE-DIMENSIONAL NETWORKS, FORMATIONS,
AUTONOMOUS SYSTEMS, QUANTUM COMMUNICATIONS
Abstract
This paper creates a vision for 5G and beyond satellite
connectivity and discusses use cases where development is
needed. We define a layered architecture for future integrated
terrestrial-nonterrestrial networks and discuss what are the key
communications technologies needed to make the operation
reliable and efficient. We outline research challenges
including high frequency bands, spectrum sharing and
interference management, optical communications, and
network management using software-defined networking
principles. Autonomous transport and autonomous satellites
are described both as key drivers behind the development as
well as disruptive technologies to fulfil future needs.
1 Introduction
Satellite networks have specific capabilities to address 5G use
cases. The consensus and general agreement on what satellite
brings to achieving 5G requirements are:
∂Ubiquity: Satellite provides high-speed capacity
across the globe using the following enablers:
capacity in-fill inside geographic gaps; overspill to
satellite when terrestrial links are over capacity;
global coverage; and backup/resilience for network
fall-back, especially for communication during
emergencies.
∂Mobility: Satellite is the only technology capable of
providing connectivity anywhere at sea, on land or in
the air for moving platforms, aircraft, ships and trains,
while requiring a minimal terrestrial infrastructure for
support.
∂Broadcast (Simultaneity): Satellite can efficiently
deliver rich multimedia and other content across
multiple sites simultaneously, using
broadcast/multicast streams with an information
centric network and content caching for local
distribution.
Recent technological developments have led to a number of
initiatives in the Satellite Communications (SatCom) sector,
enabling the operation of High Throughput Geostationary
(GSO) as well as non-Geostationary (non-GSO) satellite
networks, based on hundreds to thousands of satellites that will
contribute to the delivery of 5G services. The initiatives
spawned recently range from High Altitude Platforms (HAPs),
to nano- and micro- satellite systems dedicated to M2M/IoT,
and to mega-constellations of small and medium size satellites
like those envisaged by OneWeb, LeoSAT and Telesat to
mention but few. Different organisations involved in these
initiatives include established satellite industry players, as well
as newcomers with an increasing presence of entrepreneurs,
hybrid public-private organizations, enthusiasts and crowd-
sourced projects [1]. Private companies and their innovations
mainly drive this emerging area, which is rapidly growing and
very competitive due to a huge number of potential players.
Recent examples of new space applications include space
tourism, CubeSats, high-end private imaging satellites using
e.g. hyper-spectral cameras and synthetic-aperture radars, and
the creation of very low orbiting mega-constellations for
reduced latency, high throughput communications.
In this paper, we focus on the “5G and beyond” connectivity
that is seen as a key enabler for different 5G verticals,
including maritime, transport and public safety. We underline
the advantages and the challenges of satellite networks in
providing the appropriate response to specific use case
requirements.
2 Use cases and some high-level requirements
2.1 Communications on the move
Communications on the move is a natural use case for future
satellite-terrestrial systems [2], [3]. 5G and beyond
technologies will need to provide robust high capacity
connections to the airplanes, trains, cars, working machines,
and maritime users across the globe. Support for mobility,
seamless handovers over different radio technologies, and high
uplink data rates e.g. in case of remote-controlled machines
and ships need to be provided. In addition, positioning both
indoor and outdoor needs integrated systems where satellite
and terrestrial components support each other, providing
reliable positioning and navigation services in all
environments.

2
Figure 1. Layered architecture of 5G and beyond network
2.2 Public safety
Public safety users have traditionally relied on dedicated
narrowband professional mobile radio systems and separate
satellite connections in their operations. Use of mobile
broadband networks is increasing due to demands for
broadband services, new multimedia applications and smart
devices. For example, border guards and military personnel
need rapidly deployable networks in remote locations. They
would like to use multi-radio networks, combining satellite
systems, long-range digital communications and broadband
solutions in the remote and isolated environments to different
services. Integrated 5G and beyond systems promise to
provide solutions to their needs.
In addition, future satellite systems may provide high-capacity
backhauling to small cell networks and IoT traffic from large
areas, provide high-speed direct connectivity to remote
locations, and provide low delay services to users with the use
of space and airborne platforms in low altitudes.
3 Network architecture
5G and beyond systems aim to enable seamless integration of
multiple radio and network technologies, and may use
advanced spectrum sharing for coexistence of several
satellite/non-terrestrial and terrestrial systems [4]. New work
items in 3GPP aim to integrate satellite and terrestrial systems
while developing tailored solutions e.g. for maritime and
railway services. The current standardization study items
develop architectures for direct and indirect access using Non-
Terrestrial-Networks (NTN), including GSO and non-GSO
with both bent-pipe and regenerative payloads [5], [6]. To
benefit most from these deployments, future NTN
architectures will be layered and 3-dimensional, including a
terrestrial component, drones, high-altitude platforms and
satellites in different orbits interconnected via high throughput
Inter Satellite Links (ISLs), enabling direct data packet routing
through space [7]-[11]. The different connectivity links in this
integrated airborne-terrestrial system will be generated by use
of radio frequency and/or optical technologies providing short
delay connectivity from Earth.
The high-level architecture is shown in Figure 1, including a
common 5G+ core network functionality. The combined use
of network slicing techniques, multi-layered architectures,
context awareness and advanced routing needs to be explored
in 3D NTN networks, in order to provision a perceived
integrated infrastructure with terrestrial networks. This will
need to accommodate requirements defined by the target
verticals and to properly utilize assets and infrastructure
owned by multiple stakeholders.

3
3.1 Terrestrial layer
Terrestrial network layer includes fixed and mobile users and
a number of radio access technologies (RAT) such as new 5G
radios, 4G, and WiFi. Car-to-car and ship-to-ship
communications may use also radios specifically developed
for those purposes. The user equipment (UE) consists of a
multi-radio terminal (any type of integrated communication
device) including the satellite access. The radio access network
(RAN) transport, including the satellite core, are assumed to
be software-defined networking (SDN) capable and support
multi-tenancy. 5G+ core supports seamless cooperation
between the terrestrial and satellite segments and enables QoS
management of data transmission e.g., by dedicating part of
the resources to applications with higher priority.
Multi-tenancy support is essential because in practice,
different RANs and transport networks are often managed by
separate network operators. Network virtualization and slicing
techniques enable different operators to share network
resources with other (virtual) operators and to provide end-to-
end connectivity across operator boundaries [12]. The whole
3D network could be controlled by a centralized entity, an
SDN controller, which has the control over the network
devices and global knowledge about the network state within
an administrative region.
Furthermore, multi-access edge computing (MEC) provides
localized computing and storage resources for applications as
well as real-time information of local network conditions. The
satellite can provide a reliable backhaul link for edge
computing since the service delivery delay is not affected by
the backhaul. Together, software networks permitting flexible
control of network traffic with fine granularity and MEC
enabling the provision of scalable distributed services and
network functions create a highly plastic integrated satellite-
airborne-terrestrial system.
3.2 Airborne layer
The next layer under the LEO includes high altitude platforms
between 10 km and 50 km, mostly concentrated around 20 km
altitude. Possible HAPs include 1) balloons 2) fixed-wing
aircraft, and 3) unmanned aerial vehicles (UAVs). There can
be WiFi, 4G, 5G type of payloads providing connectivity to
terrestrial users, and Earth observation (EO) sensors for remote
sensing purposes. Due to short distance there is no need to
make differences to the radio equipment and standardized
cellular equipment can be used to provide services from HAPs
to cellular users.
A major challenge for many operations is the ability of a HAP
to maintain stationary position due to windy conditions in the
high altitudes. An operating altitude between 17 and 22 km is
often chosen for platforms because in most regions of the
world this represents a layer of relatively mild wind and
turbulence above the jet stream. This altitude (> 17 km) is also
above commercial air-traffic heights, which would otherwise
prove a potentially prohibitive constraint.
Tethered aerostations and unmanned balloons are density
neutral, floating at the desired altitude. Propulsion is only
Figure 2. Geometry of LEO satellite links.
used to maintain the position. Tethered balloons are generally
operated with a few hundred of meters altitudes, thus called
also low altitude platforms (LAPs). Although tether limits the
achievable height of the balloon, it also offers means to feeding
electric power and communications cable to the platform.
Thus, they can be used for long-duration missions.
Majority of drones or UAVs operate at the low altitude. They
are versatile and easily deployable aerial platforms that are
increasingly used for different applications and purposes.
According to [10] the following attributes makes drones
desirable candidate to substitute or complement terrestrial
networks. 1) Higher probability for line-of-sight (LoS) links to
connect users in the ground and ability to adjust locations to
maintain high quality links. 2) Dynamic deployment capability
according to needs. No needs for site rental costs. 3) UAV-
based swarm networks for ubiquitous connectivity to recover
and expand communications in fast and effective ways.
3.3 Space layer
The space layer consists of several different satellite orbits that
are depicted in Figure 1. There are large satellites operating in
MEO, GEO and HEO orbits, mostly built, launched and
operated with the established space players. Small satellite
R&D efforts are growing rapidly with new players that focus
on lower orbits and integrating different parts to a functional
integrated system. Since 5G and beyond networks aim to
provide low-latency services the ability of space segment to
support that is essential. The propagation channel delay for
LEO satellites is dependent on the connectivity geometry
shown in Figure 2. The minimum delay is when the satellite is
exactly at the Zenith, i.e. the link length is exactly the satellite
orbit height. The maximum link length m is achieved when the
satellite is in the Horizon. It is defined geometrically from
+=(
+ ℎ) which yields to
=(e+)(1)
For example, for the orbit height of h = 400 km the mis 2300
km. Thus, the delay also varies. Horizon lengths and related
delays for LEO orbits are presented in Table 1. The satellite
link length r varies between h and m.

4
Table 1. Detailed look at the LEO system delays
Orbit (v)LEO
Typical orbit height (km) 160 – 1400
Horizon (km) 1440–4450
2-way latency at Zenith (ms) 1 – 10
2-way latency at Horizon (ms) 10 – 30
This means that if there is a strict delay requirement that needs
to be achieved with low Earth orbits, one needs to have a
constellation where satellite connection far from the Horizon
(and closer to the Zenith) is always available. The mega-
constellation initiatives are good examples of constellations
where many satellites are visible for the ground station and
possibility to select a shorter satellite link for low delay
services is high.
4 Research challenges
Realization of depicted 3D network requires research efforts
such as defining the most appropriate frequency bands to be
used for different services and links. Partly the work should
concentrate on creating solutions for higher frequency bands
such as Q/V and W bands, where significant radio frequency
(RF) antenna development work and channel measurements
are required. Partly it should concentrate on solving spectrum
sharing and interference management problems caused by the
complex architecture. There are also networking related
problems, e.g. how to create reliable end-to-end links while
there is constant mobility in the network. For deterministically
moving satellites, a natural option would be to pre-compute
routing tables. However, inclusion of other airborne platforms
such as drones and HAPs demands novel integrated solutions.
Simultaneously there is a need to ensure that security stays at
a high level. The main challenges are reviewed in following
sections.
4.1 Physical layer and MAC procedures
Timing advance (TA), random access, and hybrid automatic
repeat request have been found to be essential techniques in
realization of 5G satellite systems [7]. The TA is a negative
offset that informs the UE on the correct uplink transmission
timing so as to guarantee that all of the uplink frames received
by the basestation (gNB or Next Generation NodeB in 5G
terminology) from its users are aligned with the corresponding
downlink frames. How to guarantee proper timing over
variable LEO delays described in Table 1 is a challenge.
Rapidly moving satellites on a LEO orbit can have a Doppler
shift of tens of kilohertz relative to a ground station. If the
LEO system architecture does not include relay nodes the
impact of large Doppler shifts is a limiting factor [7]. Due to
varying link lengths and delays as well as fading effects caused
e.g. by rain in Ka band, adaptive power control and adaptive
modulation and coding (AMC) need to be used in the LEO
systems [6].
4.2 Software networks and mobile edge computing
With the decreasing cost of computing and with the
requirements to reduce the communication end-to-end delay
by localizing as much as possible the services, a new
opportunity appeared for the deployment of customized
networks. This includes the dynamic network deployments
and configuration [13], [14] across the multiple compute
resources available in the system in order to provide on-
demand low latency services. A complex architecture, as the
one described in this paper requires a careful attention into the
directions of compute nodes or edge nodes [3] placement, on
the specific customization and the deployment of the network
functions on top of the infrastructure as well as on the real time
management of the infrastructure-software combined system.
As the complexity of the overall system is drastically increased
through the softwarization of the network components, two
critical issues need to be fixed. 1) The easiness of the
deployment and the maintenance of the network (“zero-touch”
configuration) and 2) the customization of the system policies
towards the specific use case needs which can be implemented
using machine learning based insight into the large amount of
monitored management data.
4.3 Mobility and routing
The proposed architecture provides the means for a
comprehensive routing system enabling the exchange of the
data between two ground stations while using data paths
passing through a large number of space elements. From a
routing perspective, a new routing protocol has to be designed
taking into account the specific communication characteristics
within the different segments: 1) the predictable, albeit
continuously changing network topology within the in-space
segment, especially due to the placement of the low orbit
communication elements. 2) The variations in capacity and
availability of the links between the terrestrial and the in-space
segment especially due to weather. 3) The changes in the
terrestrial communication needs and the interoperability with
the existing routing system, 4) the HAPs’ capability to increase
the communication for a given duration of time and 5) the
accounting of the exceptional situations in which one or more
of the links are temporary not available for example due to
unscheduled changes of orbit.
Furthermore, as the cost of the uplink of data may be highly
costly and prone to interruption of the end-to-end
communication a comprehensive caching/buffering system
has to be considered either in a predictive manner [15] for the
service continuity as well as in a reactive manner for
broadcasting the same data content. The delivery of end-to-end
service requires various service functions described in [16].
4.4 High frequency bands
There is a clear trend to go to higher frequencies both in
terrestrial and satellite systems. It is mainly driven by
increased capacity and bandwidth needs that cannot be
fulfilled with currently used frequencies. Very high throughput
satellite systems aiming to achieve terabits per second
connectivity need to use large bandwidths that are only
available in Q/V band (30-50 GHz) and higher. The signal

5
Figure 3. W-Cube nanosatellite for channel characterization.
travelling through the atmosphere is subject to absorption and
dispersive effects in amplitude and phase that have to be
carefully characterized. A recently started W-Cube activity is
using nanosatellites equipped with a beacon transmitter to
measure and characterise wireless channel in the 70/80 GHz
band [17]. The soon-to-be launched satellite is depicted in
Figure 3. It includes an innovative concentric ring antenna for
W band signal transmission. Development of terahertz
communications [18] above 100 GHz is ongoing to use very
wide bandwidths. However, path losses in these frequencies
are very high, limiting the applicability of the band to long
range communications.
Antennas are the key technologies to cover new frequency
bands, to support high-speed links, and to be able to use
steerable transmissions at the space and airborne platforms as
well as the ground. Massive MIMO technology, beamforming
and phased array antennas are being developed for different
purposes, including communications on the move platforms.
In the small satellites the cost and power consumption are
clearly limiting factors. Ground stations will use electronically
steerable multi-beam antennas, able to communicate with
multiple LEO satellites simultaneously. Miniaturization and
creation of efficient antennas to small satellites is an important
topic and e.g. planar patch antennas are being developed
actively. It is essential to develop antenna systems that can
sustain wireless links or remote sensing requirements in a
small, stowable package [19].
4.5 Spectrum sharing and interference management
In addition to use of higher frequencies it is possible to
increase bandwidth and enable more services by use of
spectrum sharing. Potential spectrum sharing scenarios were
classified in [4] as: a) secondary use of the satellite spectrum
by terrestrial systems, b) satellite system as a secondary user
of spectrum, c) extension of a terrestrial network by using the
satellite network, and d) two satellite systems sharing the same
spectrum. Licensed spectrum sharing [4] is a coordinated way
to share spectrum with guaranteed QoS while using a database
to share information between sharing parties. When using
carrier aggregation, the licensed shared access (LSA) system
can use a licensed carrier and the shared band carrier together
to enhance capacity.
There are many possibilities and research challenges from the
spectrum sharing viewpoint in the depicted architecture.
Figure 4. Artistic impression of HydRON vision [24].
Sharing the same frequencies in different layers could be
possible especially with directional transmissions. Inter
satellite links could use same frequencies as satellite-to-
ground links. New scenarios and use cases for satellite systems
and terrestrial systems will appear in high frequencies,
including airborne component. Complex co-channel and
adjacent channel interference cases need to be studied between
different layers and for that purpose channel characterization
studies are also essential.
Current human-controlled approaches and timescales for
spectrum management are not efficient enough for growing
future needs. Artificial intelligence (AI) techniques have
potential to make decisions in seconds and milliseconds
timescales in order to meet the full potential of the 3D layered
network. There are ambitious programs such as [20]
developing AI methods for 5G and beyond spectrum sharing,
mostly for terrestrial domain and a number of predictive
approaches have been considered in [21] and [22]. However,
new methods are needed to take into account both
deterministic movement of satellites as well as the general high
dynamics of the depicted 3D system. In the public safety use
case the capability to learn the environment, detect and avoid
jamming and ability to switch rapidly to a usable frequency are
seen as clear goals for the AI research.
Beam hopping technology provides an ability to switch the
transmitting power from beam to beam as a function of time
[23]. Subset of the satellite beams is adaptively activated and
deactivated according to the actual traffic demands through an
appropriately designed beam illumination pattern. Since the
satellite only illuminates a small fraction of beams out of a
large number of beams deployed under beam hopping systems,
the rest of the beams remain idle, providing sharing
opportunities to other satellite, airborne, and terrestrial system.
4.6 Optical communications
Optical communication is a disruptive technology that will
enable inter satellite links and satellite formations, and can
lead to significant power savings compared to RF
communications. According to [24] it can provide safe and
cyber secure way to serve scalable 3D networks, enabling a

6
GEO
LEO
Airborne
Vertical
handover
5G
Ground
segment
Horizontal
handover
Vertical
handover
Figure 5. Handover scenarios in a layered network.
shift from partitioned ground and space segments into a fully
integrated system. That may lead to drastic reduction in
ownership costs of satellite communications solutions. Still
significant advances are needed to implement reliable space
to/from ground optical links (i.e., optical feeder links), intra-
and inter satellite laser links and optical routing (i.e., optical
cross-connects, reconfigurable optical add-drop multiplexer).
The Hydron vision is depicted in Figure 4 and the aim is to
have the mission operational by 2022.
Optical communications is limited in many areas due to
clouds. There is actually an “optical belt” across Sahara and
middle East where satellite-to-ground connections are possible
due to cloud-free availability [11].
4.7 Quantum communications
Quantum communication provides means to make satellite
systems more secure. For example, in the Qritical project the
aim is to identify how space-based optical communication
technologies, in particular quantum key distribution, can be
designed, deployed and used to protect European critical
infrastructure [25]. The project is developing a
communications security architecture and corresponding
technical, operational and mission requirements. Quantum
communications with single photons and employing satellites
as nodes of the network to allow coverage for the whole globe
is discussed in [26].
4.8 End-to-end cybersecurity
Both payload and control communication need to be tested
before launching the satellites into orbit. It is important to
cover whole end-to-end path when creating reliable, secure
communications. An example of a security challenge is the
handover situation that can happen quite frequently in dynamic
3D networks. Key management during the handover situations
described in Figure 5 is challenging [27]. For example, when
a police officer is changing his connection from the tesrrestrial
5G to a LEO satellite, handover information includes both
previously accessed networks and newly accessed satellites.
Signalling is exchanged between different entities and might
be eavesdropped, falsified, or fabricated.
A specific cybersecurity testing facility could be developed in
order to create hardened small satellite systems. Testing should
Figure 6. Examples of autonomous systems needing integrated
satellite-terrestrial systems; Road transport, UAVs, working
machines, and autonomous ships.
identify critical interfaces and risks in the system and cover
platforms, ground, and space segments. The testbed could
cover physical infrastructure and virtualized network functions
enabling the establishment of the end-to-end virtual satellite-
terrestrial network as infrastructure as a service (IaaS) [28].
5 Autonomous systems as future disruption
There are several disruptive technologies and application areas
advancing the space “5G and beyond” research. After defining
the general technical challenges we focus here on
softwarization of satellites, autonomous transport, and
autonomous satellites themselves.
5.1 Software-defined satellites
Satellite operators aim to reduce costs of future satellite
connectivity by using software-defined satellites that enable
radio updates with the latest standard features, such as on-the-
fly and 3D layered architecture control and management based
on extensions of software defined networks concepts that are
already used for the terrestrial components [13], [14]. The
ability to change coverage areas, power and frequency
allocations, and architecture on-demand would mean that a
satellite can be manufactured first and tailored to the operator
needs later. This system can be further augmented by machine
learning and automated configurability towards the specific
characteristics of the communication (i.e. going from “white-
boxes” models towards more customized systems.
5.2 Autonomous transport
Autonomous and remote-controlled systems is one disruption
in modern society, driving the development of space airborne
communications systems. For example, autonomous vessels’
demand for high throughput uplink, whilst their downlink
requirement is significantly lower [12], [29]. The same is true
for many Internet-of-Things (IoT) applications [31]. This is
opposite to the traditional way of designing satellite systems.
Integrated satellite-terrestrial systems are needed to support
operation of autonomous cars, machines, and ships globally.
These autonomous systems can be classified to four main
categories shown in Figure 6. Integrated layered systems can
provide robustness for data transmission and positioning.

7
5.3 Autonomous satellites
Satellites themselves can be also seen as autonomous systems
requiring e.g. autonomous navigation capabilities. Software-
defined satellites enable development of “satellites as
autonomous agents” performing their missions autonomously
over extended periods of time even in deep space
environments. Formations and inter satellite links are needed
to create autonomous satellite systems consisting of multiple
satellites.
Autonomous satellites can use deep learning, expert systems
and intelligent agents to process spacecraft data (telemetry,
payload) and to take decisions autonomously during the
mission [30]. Artificial intelligence enables autonomous
replanning, detection of internal and external events, and
reaction accordingly, ensuring fulfilment of mission objectives
without the delays introduced by the decision-making loops on
ground.
6 Innovative, ambitious missions
Let us discuss couple of ambitious missions, in addition to
already described HydRON mission, to spark thoughts for
future development needs. First, the planned HERA mission
will use deep-space cubesats launched by the larger satellite
when in the vicinity of the Didymos asteroid to be studied in
detail [32]. Also deep-space intersatellite links will be tested
between the large and small satellites. Hera will also
demonstrate autonomous navigation around the asteroid
similar to modern autonomous cars or ships on Earth, and
gather crucial scientific data, to help scientists and future
mission planners better understand asteroid compositions and
structures. In addition, jointly with the DART mission [33] the
aim is to study planetary defence mechanisms and possibility
to shift the asteroid orbit with a kinetic impact.
Second, deep space communication network providing
connectivity anywhere in the space is an ambitious mission. It
is described in [34] as “The deep space exploration missions
require high quality of communication performance between
the Earth stations and various deep space explorers, such as
Mars orbiters and rovers.” The paper describes a structured
solar system satellite constellation network where several
relays are used to create a topology that can support deep space
operations and connect objects from the deep space to each
other and to the Earth.
Many other missions are developed annually and it is foreseen
that the development of the visionary 3D network around the
globe and the deep space communication network would
enable unforeseen growth in New Space missions. When the
connectivity is robust and working anywhere the innovative
missions also for science and remote sensing can be served at
the unprecedented level.
7 Conclusion
The paper provides a vision for future satellite
communications from the integrated networks perspective. We
defined a layered three-dimensional architecture for future
space networks and defined key techniques and research
challenges to enable efficient operations. Identified topics
include e.g. software-defined networking, end-to-end
cybersecurity, optical inter satellite links, and spectrum
sharing to be able to keep interference at the acceptable level.
Finally, we discussed key disruptive technologies for future
space systems describing software-defined satellites,
autonomous transport and autonomous satellite systems. We
hope that the paper can serve as a fruitful source when defining
research directions and development goals for connectivity
research.
Acknowledgements
The work was supported partly by VTT New Space program.
The views expressed herein can in no way be taken to reflect
the official opinion of the European Space Agency.
References
[1] Pomeroy C., Diaz A. C., and Bielicki D., “Fund me to the Moon:
Crowdfunding and the New Space Economy,” Space Policy, vol. 47,
pp. 44-50, Feb. 2019.
[2] Sharma S. K., Chatzinotas S., and Arapoglou P. D. (eds.),
Satellite Communications in the 5G Era, The Institution of
Engineering and Technology, 2018.
[3] Völk F. et al., “Satellite integration into 5G: Accent on first
over-the-air tests of an edge node concept with integrated satellite
backhaul,” Future Internet, vol. 11, 17 pp, Sept. 2019.
[4] Höyhtyä M. et al., “Database-assisted spectrum sharing in
satellite communications: A survey,” IEEE Access, vol. 5, pp.
25322-25341, Dec. 2017.
[5] 3GPP, “3rd Generation Partnership Project; Technical
Specification Group Services and System Aspects; Study on
architecture aspects for using satellite access in 5G,” TR 23.737
V0.3.0, Technical Report, Oct. 2018.
[6] 3GPP “3rd Generation Partnership Project; Technical
Specification Group Radio Access Network; Study on New Radio
(NR) to support non terrestrial networks,” TR 38.811 V15.0.0,
Technical Report, June 2018.
[7] Guidotti A. et al., “Architectures and key technical challenges
for 5G systems incorporating satellites,” IEEE Transactions on
Vehicular Technology, vol. 68, pp. 2624-2639, Mar. 2019.
[8] ‘IEEE 5G and Beyond technology roadmap white paper’,
https://futurenetworks.ieee.org/images/files/pdf/ieee-5g-roadmap-
white-paper.pdf, accessed 24 September 2019.
[9] Radhakrishnan R. et al., “Survey of inter-satellite
communication for small satellite systems: Physical layer to network
layer view,” IEEE Communications Surveys & Tutorials, vol. 18,
pp. 2442-2473, Oct. 2016.
[10] Li B., Fei Z., and Zhang Y., “UAV communications for 5G and
beyond: Recent advances and future trends,” IEEE Internet of
Things Journal, vol. 6, pp. 2241-2263, Apr. 2019.
[11] Israel D. J. and Shaw H., “Next-generation NASA Earth-
orbiting relay satellites: Fusing optical and microwave
communications,” in Proc. IEEE Aerospace Conference, Mar. 2018.

8
[12] Höyhtyä M. et al., “Integrated 5G satellite-terrestrial systems:
Use cases for road safety and autonomous ships,” in Proc. KaConf,
Oct. 2017.
[13] Kreutz D. et al., “Software-defined networking: A
comprehensive survey,” Proceedings of IEEE, vol. 103, pp. 14-76,
Jan. 2015.
[14] Xu S., Wang X.-W., and Huang M., “Software-defined next-
generation satellite networks: Architecture, challenges, and
solutions,” IEEE Access, vol. 6, pp. 4027-4041, Jan. 2018.
[15] Bastug E., Bennis M., and Debbah M., “Living on the edge:
The role of proactive caching in 5G wireless networks,” IEEE
Communications Magazine, vol. 52, pp. 82–89, Aug. 2014.
[16] Medhat A. M. et al., “Service function chaining in next
generation networks: State of the art and research challenges,” IEEE
Communications Magazine, vol. 55, pp. 216–223, Feb. 2017.
[17] ‘W-Cube – cubesat based W-band channel measurements’,
https://artes.esa.int/projects/w-cube, accessed 24 Sept. 2019.
[18] Akyildiz I. F, Jornet J. M. and Han C., “Terahertz band: Next
frontier for wireless communications,” Physical Communications,
vol. 12, pp. 16-32, Sep. 2014.
[19] Rahmat-Samii Y., Manogar V. and Kovitz J. M., “For satellites,
think small, dream big – A review of recent antenna developments
for CubeSats,” IEEE Antennas & Propagation Magazine, vol. 59,
pp. 22-30, Feb. 2017.
[20] ‘DARPA spectrum challenge,’
https://www.darpa.mil/program/spectrum-collaboration-challenge,
accessed 24 Sept. 2019.
[21] Höyhtyä M. et al., “Database-assisted spectrum prediction in
5G networks and beyond: A review and future challenges,” IEEE
Circuits & Systems Magazine, vol. 19, pp. 34–45, Third Quarter
2019.
[22] Bui N., et al., “A survey of anticipatory mobile networking:
Context-based classification, prediction methodologies, and
optimization techniques,” IEEE Communication Surveys &
Tutorials, vol. 19, pp. 1790–1821, Third Quarter 2017.
[23] Sharma S. K., Chatzinotas S., and Ottersten B., “Cognitive
beamhopping for spectral coexistence of multibeam satellites,”
International Journal of Satellite Communications, vol. 33, pp. 69–
91, Jan./Feb. 2015.
[24] Hauschildt H., Elia C., Moeller H. L., and Armengol J. M. P.,
“HydRON: High throughput optical network,” in Proc. SPIE Free-
Space Laser Communications XXXI, Mar. 2019.
[25] Truyens N. and Crowcombe W., “Advancements in optical
satcom at TNO,” Scylight Workshop, June 2019.
[26] Flamini F., Spagnolo N., and Sciarrino F., “Photonic quantum
information processing: A review,” Reports on Progress in Physics,
vol. 82, pp. 1–32, Jan. 2019.
[27] Jiang C., Wang X., Wang J., Chen H.-H., and Ren Y., “Security
in space information networks,” IEEE Communications Magazine,
vol. 53, pp. 82-88, Aug. 2015.
[28] Manvi S. S. and Shyam G. K., “Resource management for
Infrastructure as a service (IaaS) in cloud computing: A survey,”
Journal of Network and Computer Applications, vol. 41, pp. 424–
440, May 2014.
[29] Höyhtyä M., “Connectivity manager: Ensuring robust
connections for autonomous ships,” in Proc. ICoIAS, Feb.-Mar.
2019.
[30] ‘AIKO: Autonomous operations thanks to artificial
intelligence,’ https://www.esa.int/Our_Activities/
Telecommunications_Integrated_Applications/TTP2/AIKO_Autono
mous_satellite_operations_thanks_to_Artificial_Intelligence,
accessed 26 Sept. 2019.
[31] DeSanctis M. et al., “Satellite communications supporting
Internet of remote things,” IEEE Internet of Things Journal, vol. 3,
pp. 113-123, Feb. 2016.
[32] ‘HERA mission’, https://www.esa.int/Our_Activities/
Space_Safety/Hera/Hera, accessed 24 Sept. 2019.
[33] ‘Double Asteroid Redirection Test (DART) mission’,
https://www.nasa.gov/planetarydefense/dart, accessed 26 Sept.
2019.
[34] Wan P. and Zhan Y., “A structured Solar System satellite relay
constellation network topology design for Earth-Mars deep space
communications,” International Journal of Satellite Systems and
Networking, vol. 37, pp. 292-313, May/June 2019.