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An assessment of IoT via satellite: Technologies, Services and Possibilities

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The number of proposed satellite constellations for communication purposes has been steadily increasing in the past years. Currently, more than 18 constellations have been proposed and are in different stages of development, from early design to having already launched in-orbit-demonstration (IOD) satellites. The common feature among these different proposals is that all of them aim to provide connectivity to IoT sensor systems in areas outside coverage from terrestrial mobile networks. Despite the generalized use of IoT for several purposes, IoT via satellite systems typically target a few special use-cases, leaving other relevant applications and services behind. In this work, we study and discuss how such systems can be integrated and augment a broader range of terrestrial IoT and mobile systems. This includes an analysis of the technical properties of the constellations, their service philosophies, and how they are aligned with existing communication networks. Relevant cellular and non-cellular terrestrial technologies are considered, including LoRA, SigFox and 5G alternatives such as NB-IoT. The impact of mega constellations will also be taken into account, identifying existing technology and service gaps. These gaps in satellite-IoT systems and in mega constellations may result in an inadequate augmentation of terrestrial networks and fail to fulfill user requirements. Relevant end-user services are investigated, spanning from asset tracking, simple environmental and industrial sensors to more advanced sensor networks in remote areas. The different user requirements are compared and matched against available and upcoming IoT solutions. From this, different strategies for integration of IoT via satellite with terrestrial systems are proposed and evaluated.
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70th International Astronautical Congress (IAC), Washington, USA, 21-25 October 2019.
Copyright © 2019 by the Norwegian University of Science and Technology. Published by the IAF, with permission and
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IAC-19,B4,7,13,x51822
An assessment of IoT via satellite: Technologies, Services and Possibilities
Roger Birkelandaand David Palmab
aDepartment of Electronic Systems, Norwegian University of Science and Technology, Trondheim, Norway,
roger.birkeland@ntnu.no
bDepartment of Information Security and Communication Technology, Norwegian University of Science
and Technology, Trondheim, Norway, david.palma@ntnu.no
September 2019
Abstract
The number of proposed satellite constellations for communication purposes has been steadily
increasing in the past years. Currently, more than 18 constellations have been proposed and
are in dierent stages of development, from early design to having already launched in-orbit-
demonstration (IOD) satellites. The common feature among these dierent proposals is that
all of them aim to provide connectivity to IoT sensor systems in areas outside coverage from
terrestrial mobile networks.
Despite the generalized use of IoT for several purposes, IoT via satellite systems typically
target a few special use-cases, leaving other relevant applications and services behind. In this
work, we study and discuss how such systems can be integrated and augment a broader range of
terrestrial IoT and mobile systems. This includes an analysis of the technical properties of the
constellations, their service philosophies, and how they are aligned with existing communication
networks. Relevant cellular and non-cellular terrestrial technologies are considered, including
LoRA, SigFox and 5G alternatives such as NB-IoT.
The impact of mega constellations will also be taken into account, identifying existing tech-
nology and service gaps. These gaps in satellite-IoT systems and in mega constellations may
result in an inadequate augmentation of terrestrial networks and fail to fulll user requirements.
Relevant end-user services are investigated, spanning from asset tracking, simple environmental
and industrial sensors to more advanced sensor networks in remote areas. The dierent user
requirements are compared and matched against available and upcoming IoT solutions.
From this, dierent strategies for integration of IoT via satellite with terrestrial systems are
proposed and evaluated.
1 Introduction
Communication is crucial in our daily lives, and our
dependence on being online is only growing. It is im-
portant for our personal life and well-being, as well as
for our work, our research and our administration of
resources. In urban and well-developed parts of the
world, communication services are plentiful, but one
should not venture far outside a city before coverage
gaps are encountered. The situation in developing
parts of the world is even more challenging.
Satellites can be fundamental for enabling the United
Nations Sustainable Development Goals [1], in par-
ticular when considering innovative, responsible and
sustainable development in remote/unconnected re-
gions of the world. Challenges to future satellite so-
lutions encompass a careful allocation of specic ra-
dio frequencies for various applications, as well as de-
tailed technical provisions and regulatory procedures.
This includes with mobile networks, namely with the
fth generation cellular technology (5G) ecosystem.
Strategic integration avoids competing for frequen-
cies and instead helps to relieve congestion and over-
loaded networks, while also increasing connectivity
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when and where typical terrestrial networks (TNs)
are not available. With this in mind, ongoing on
3rd Generation Partnership Project (3GPP) speci-
cations include studies and requirements for 5G satel-
lite access and for the broadening the 5G technol-
ogy to non-terrestrial networks (NTNs) (e.g. satellites
and unmanned aerial systems) [2, 3, 4, 5].
5G promises to revolutionise terrestrial communica-
tions by enabling three dened main use-cases: en-
hanced Mobile Broadband (eMBB) access for high
data-rate applications; massive Machine Type Com-
munications (mMTC) for a large number of devices
with sporadic communication needs such as Inter-
net of Things (IoT) applications; Ultra-Reliable Low-
Latency Communications (URLLC) for mission crit-
ical applications. However, such scenarios will likely
only be available in urban areas, mostly ignoring rural
or underdeveloped areas due to their lower revenue
potential. In these neglected areas small and light
satellite terminals could provide reliable radio links,
or gateway ground-stations could be used as a back-
haul for aordable terrestrial solutions. Deploying
an ultra-secure and highly reliable optical backbone
in space is already envisaged, supported by lasers to
interconnect satellites and up to 1.5times faster than
ber backbones (LeoSat) [6].
Satellites can eectively provide coverage in remote
areas, support highly mobile users (e.g. aircraft and
ships, including rst responders) and are suited for
dierent applications, from IoT to search and res-
cue operations. Compared with terrestrial solutions,
satellite connectivity is becoming increasingly more
cost eective when considering remote areas or devel-
oping areas. The integration of satellite and terres-
trial solutions is the most sustainable approach due
to the complementarity between the two solutions,
simultaneously fostering economic growth, social in-
clusion and meeting consumer demand.
The importance of integrating terrestrial and non-
terrestrial networks has been the subject of several
research works, focusing on subjects such as vehic-
ular networks (air, space and ground) [7] or IoT
and maritime IoT [8, 9, 10, 11], and building on
the main features and development from both net-
works (4G/5G) [12, 13, 14, 15, 16]. The value of
this integration is also acknowledged by the Euro-
pean Space Agency (ESA) through several research
projects [17, 18] such as SATINET [19], SATis5 [20]
and M2MSAT [21]. Larger research projects funded
by the European Union’s Horizon 2020 research and
innovation programme such as SANSA [22], VI-
TAL [23] and SAT5G [24] have also addressed the
integration of terrestrial and satellite networks. Sim-
ilarly, 3GPP, the 5G Public Private Partnership
(5G PPP) and the International Telecommunica-
tion Union (ITU) have been following these devel-
opments and contributing not only to the awareness
but also to the specication of integrated terrestrial
and non-terrestrial networks for improved communi-
cations around the world [2, 3, 4, 5, 6, 25].
In this paper we analyse how satellites can support
IoT, augment terrestrial networks and bring connec-
tivity to areas where it is sparse or non-existent. Sec-
tion 2 provides an overview of ongoing or proposed
satellite networks, their characteristics, features and
how they may support IoT around the globe. This is
followed by an analysis of how cellular 5G networks
can be augmented by such satellite initiatives into
an integrated ecosystem, in Section 3. Section 4 re-
views possible services and use cases considering dif-
ferent possibilities for system and network architec-
tures. Finally, Section 5 provides avenues for further
discussion and some concluding thoughts.
2 Satellite IoT
Communication links to remote sensor systems have
been available through machine-to-machine (M2M)
communication over satellite for many years, before
IoT was coined as a term. The Argos tracking sys-
tem [26] and Iridium dial-up or Short Burst Data
(SBD) [27] are good examples of this. Depending
on denition, we may also include these in the IoT
family, since their systems provide access and infor-
mation about sensors in remote locations. IoT is here
dened as such [28]:
The internet of things, or IoT, is a system
of interrelated computing devices, me-
chanical and digital machines, objects,
animals or people that are provided with
unique identiers (UIDs) and the ability
to transfer data over a network without
requiring human-to-human or human-to-
computer interaction.
In addition to the existing systems, there are several
initiatives that oer support for IoT-devices through
a satellite component. In this section we focus on
satellite systems independent from popular terrestrial
communication solutions, and initiatives related to
5G are discussed separately in Section 3.
A selection of eorts and developments on satellite
communications suitable for IoT-like applications are
summarized in Table 1. The table shows the main
features for each of the systems, namely: System
Type); Status; Frequency; Continuous coverage amd
Arctic coverage. The System Types are divided into:
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A– Asset Tracking, corresponding to track-
ing the location of objects as animals, vessels
or freight
B– Narrowband IoT, corresponding to systems
for generic two-way communication
C– Message-based IoT, corresponding to sys-
tems using one or two-way short messages
D– Broadband, corresponding to systems ca-
pable of high-bandwidth generic two-way com-
munication
Some systems may fall into more than one category.
Regarding the status of a system, it may be consid-
ered as Operational, in Testing or currently being
Planned. The considered frequency bands include
VHF, UHF, S-band and Ka/Ku. Not all systems
provide continuous coverage and this is shown in the
table as Yes or No (‘-’). Similarly, Arctic coverage
is not always provided and this will be noted with
Yes, No (‘-’) or partially (‘/’). ‘? denotes missing
or unknown information.
The table includes both generic services like Auto-
matic Identication System (AIS) [31] and Automatic
Dependent Surveillance – Broadcast (ADS-B) [32]
which are oered by several actors, or specialized pro-
prietary networks. Some of the systems are proposed
to cover a broad aspect of communication services,
and it can be assumed they will be linked to 5G in the
end. For example, the mega-constellations by Star-
Link and Oneweb for access and backhaul, whereas
Telesat is expected to only be used for backhaul.
The dierent communication systems oer a variety
of services. Many revolve around communication sys-
tems for asset tracking, while others focus on the
support of two-way communication. Asset tracking
means that the only information propagating through
the system is the position and other simple proper-
ties of an asset. Examples of this are GlobalStar [33],
Argos [26], AIS for tracking of ships and ADS-B for
tracking of airplanes. These are mostly one-way com-
munication, where the end-users have little control
over when the message should be sent, or the delivery
time. Systems supporting two-way communication to
small devices, such as Iridium dialup or SDB [27], Ke-
pler Kipp[39], VDES [41], and Astrocast [42] can be
used for a wide range of applications.
Some systems provide direct access to the user equip-
ment, like Iridium and Myriota [52], others provide
relay/gateway nodes to which smaller sensor nodes
(i.e. the UE) can connect to. Figures 2 and 3 show the
concept with and without the relay node. Similar ap-
proaches are expected by proposed satellite systems
that announce basing their services on LoRa, such
as Lacuna Space [53] and Fleet [48]. However this
is still an unknown detail for other systems. Several
satellite initiatives have launched test satellites dur-
ing the last 12 months, like Kepler [39], Lacuna [53],
Astrocast[42] and Helios Wire [44]. Apart from Ke-
pler’s Ka-band service in operation, little is known
about their status, both regarding technical results
and the nancial soundness of these companies.
3 5G Satellite and IoT
Satellite access should allow the delivery of 5G ser-
vices where terrestrial networks do not, and comple-
ment them where they do. 5G Satellite (5GSat) ac-
cess has the potential of serving remote areas, or ar-
eas prevented from service either due to economic
reasons (low revenue vs. protability) or to disasters
that lead to outages or damaged terrestrial network
infrastructures. Service continuity for verticals like
maritime communication, public safety, should also
be supported by 5GSat networks.
Even though 5G considers eMBB, mMTC and
URLLC as its main usage scenarios for terrestrial
cellular networks, their implementation in satellite
networks may face some challenges. While eMBB
and mMTC are interesting scenarios for 5GSat,
ultra-low latency (e.g. <1ms over the air) cannot
be achieved with satellite links [4]. Examples of
eMBB supported by 5GSat include providing broad-
band connectivity (to moving/static cells/relay nodes
and the core network), secondary backup connec-
tivity, an anchor point between two networks, mul-
ticast/broadcast, among other applications where
medium to large antennas and continuous power-
supply are typically available. Contrastingly, mMTC
supported by 5GSat should provide connectivity to
small/handheld, battery-operated IoT devices, where
continuity of service is desired, or instead provide
connectivity to a relay-node acting as a base station
a connecting to other IoT devices. In addition, due
to the wide service coverage capabilities and reduced
vulnerability of space systems (e.g. physical attacks
and natural disasters), 5GSat mMTC can be used
to broadcast/multicast resources to a large scale of
devices (e.g. Firmware/Software Over The Air Up-
grades).
Similar to past 4G Satellite initiatives [14], 5GSat
can provide service in un-served areas that cannot be
covered by TNs (e.g. isolated/remote areas, aircrafts,
vessels) and in underserved areas (e.g. sub-urban or
rural areas) where the performances of TNs is limited
terrestrial. However, critical infrastructures such as
energy grids and transport (e.g. railway, maritime,
aeronautical) increasingly rely on M2M/IoT devices,
where service availability must be ensured. If prop-
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Table 1: Overview of IoT-like satellite communication systems and initiatives
System Feature Status
T S F C A
OrbComm [29] A O V
Short, random messages, no Arctic coverage
Own set of satellites. Evolved from type A to also C
L-band through Inmarsat
ARGOS [26] A O U Y
Short, random messages. Receivers on National Oceanic
and Atmospheric Administration (NOAA) satellites.
New generation closer to type C
Iridium SBD [30] C O L Y Y Short messages only.
AIS [31] A O V Y Tracking vessels (and installations) only
ADS-B [32] A T V / Tracking airplanes only
Iridium [30] B O L Y Y Low-rate two-way, modem type communications
Iridium NeXT use large terminals, can be local gateways
Globalstar [33] B O L Y / Tracking services. Limited Arctic coverage
Inmarsat [34] B O L Y No Arctic service
Gonets [35] B P U Y Y Low rate system.
Thuraya [36] B O L No Arctic coverage
StarLink [37] D T K Y / First deployment in 53 deg orbit. Next phase
includes 81 deg, so no Arctic coverage the rst period
OneWeb [38] D T K Y Y No Inter Satellite Links (ISL), more Earth stations.
Indications of development for mobile equipment.
Kepler’s Kipp [39] D T K Y High-datarate service operational,
IoT-service planned
Telesat [40] D P K C Y Backhaul, not for single terminals
VDES [41] B T V Y Shared system, limited capacity, low rate, two way
OQ Technology C P ? ? ? Low rate system
Astrocast [42] C T L Y Two-way communication, very small messages
AISTECH [43] A P ? ? ? Asset tracking
Helios Wire [44] C T S Asset tracking, low-rate IoT + blockchain.
Status of testing unknown.
Sky and Space Global [45] C T S Voice + short messages. No polar coverage.
Hiber Global [46] C T ? Y Low rate
Aerial Maritime [47] A T V - Asset tracking (AIS & ADS-B) between 37 deg N/S
Fleet [48] B T U Y LoRaWAN [49] gateways. One terminal can cover 15 km
Spire [50] AIS & ADS-B.
Swarm technologies [51] C T U Y Small sensors
Myriota [52] B P ? ? ? IoT module/modem/egde computing device.
No extra gateway needed for users
Lacuna Space [53] B T ? ? ? Based on LoRaWAN
TSystem type: A: Asset tracking; B: Narrowband IoT; C: Message based IoT; D: Broadband
SStatus: O: Operational; T: Testing; P: Planned
FFrequency: V: VHF; U: UHF; S: S-band; K: Ka/Ku-band
CContinuous coverage: Y: Yes; ‘–’: No
AArctic coverage: Y: Yes; ‘–’: No; ’/’: Partially
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erly integrated with cellular 5G, 5GSat has the po-
tential of reinforcing the required service reliability
in a cost eective manner and including all the fea-
tures provided by 5G (e.g. condentiality, integrity,
roaming, QoS, billing, among others).
3.1 Cellular 5G and 5GSat Integration
From an architectural point of view, connecting to
a terrestrial network via Satellite access could be
transparent, using a bent-pipe satellite payload for
connecting to a ground station coupled with a Pub-
lic Land Mobile Network (PLMN) or core network.
However, this view is too simplistic and would result
in the loss of features and mechanisms provided and
used by 5G. For example, due to longer propagation
delays in satellite systems, timers used by protocols
and mechanisms such as Hybrid Automatic Repeat
Request (HARQ) would have to be extended in or-
der to maintain functionality.
In order to include satellite links between 5G’s New
Radio (NR) access network and the Next Generation
Core (NGC) the 3GPP system must to be enhanced
not only to handle the latencies introduced by the
satellite backhaul, but also to support service con-
tinuity between land-based 5G access and satellite-
based access networks [2]. This implies not only pro-
viding services using satellite access but also ensuring
handover (HO) and roaming support. Such services
may be directly accessed by the UE, through a re-
lay UE or through a Next Generation Node B (gNB)
backhauled by a satellite link.
Compared to previous approaches to the Integration
of terrestrial and non-terrestrial networks, the use
of new non-geosynchronous orbit (NGSO) constella-
tions and the softwarisation of 5G into Virtualised
Network Functions (VNFs) creates both challenges
and opportunities. For example, while NGSO sys-
tems are enablers for massive IoT access at a lower
cost and with smaller energy requirements, the mo-
bility of the infrastructure’s transmission equipment,
such gNBs and Remote Radio Heads (RRHs) may
lead to Inter Carrier Interference (ICI) and increased
HO signalling [4]. On the other hand, VNF al-
lows the delocalization of network functions, which
could be used to improve the overall QoS scenarios
where, for example, in areas where user density is ex-
pected to increase (e.g. Access and Mobility/Session
Management Functions (AMF/SMF) delocalization
to improve/enhance local communications). This re-
quires further investigation of services, their require-
ments, of conguration/maintenance and of regula-
tory frameworks between satellite and terrestrial net-
works, addressing service continuity, ubiquity and
the scalability of these networks.
Important aspects in 5GSat include roaming between
terrestrial and non-terrestrial networks, guaranteeing
satellite trans-border service continuity as well as op-
timal routing over satellite for enabling a global 5G
satellite overlay [2]. This would build on, for exam-
ple, constellations of LEO satellites providing access
to UEs, where each spacecraft is equipped with a
gNB and Inter-Satellite links for connecting to other
spacecrafts. In addition, 5GSat access should also
be aligned with 5G’s orchestration mechanisms, not
only for edge delivery, content ooad and multi-
access edge computing (MEC) VNF software, but
also for including satellite resources as Physical Net-
work Functions (PNFs) in the 5G ecosystem.
Overall, 5GSat should enable indirect connection
through a 5G satellite access network, which could
be used for example to enable communication in O-
shore Wind Farms. The possible satellite access ap-
proaches can be dened as: 1) UE direct access to 5G
satellite, 2) UE relayed access to 5G satellite RAN
and 3) gNB supported by a satellite backhaul.
Figure 1: Traditional backhaul architecture
Direct access can be provided by a 5G-enabled satel-
lite that connects directly to the Core Network or
through an overlay of satellites. Alternatively, di-
rect access may also result from a bent-pipe satellite
(transparent, with no on-board processing capabili-
ties) used to connect to a 5G Satellite RAN. Relayed
access occurs when a UE connects, using the 5G NR
interface, to a relay UE which in turn has capabilities
to connect to the satellite network. This connection
again results either from a satellite directly providing
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a 5GSat RAN or using a bent-pipe approach. These
approaches are further discussed in Section 4.
A more traditional approach considers access through
cell towers (gNBs) supported by a satellite backhaul,
where UE’s shall operate normally as with 100% ter-
restrial networks. This solution is particularly inter-
esting for expanding a 5G mobile platform (e.g. a
train with installed gNBs) or for recovering access
after disaster scenarios. In this case NR-capable de-
ployed towers would have their interfaces to the 5G
Core directly transported over the satellite link, as
seen in Figure 1.
3.2 Challenges and Possible Solutions
Typical cellular networks, and 5G, were not designed
to handle large coverage areas such as those given
by satellite nodes, particularly geosynchronous or-
bit (GSO) satellites. This raises questions regard-
ing connection management, node accessibility (pag-
ing) and overall mobility. Dierent PLMNs may
be overlapped by a single satellite, cell selection
mechanisms are open, roaming, authentication and
billing/charging must also be taken into account.
3.2.1 Mobility Issues
In order to ensure service continuity handover (HO)
signalling must be extended, supporting HO trigger-
ing whenever a UE leaves or enters cellular cover-
age. This HO can happen between terrestrial and
non-terrestrial networks, based on dierent handover
triggering policies. For example, a UE may leave a
5GSat network as soon as enough cellular coverage
is available but only only chose to leave a cellular
network when the signal is too poor.
The HO process should be lossless and consider mea-
surement report from both access technologies (ter-
restrial and non-terrestrial), while also supporting
dierent possible NTN architectures (e.g. using re-
generative or bent-pipe payloads). For this purpose,
common mobility management techniques such as
dening Tracking Areas (TAs) and Registration Ar-
eas (RAs) must be used by both TNs and NTNs.
Regarding the denition of TAs, xed beam spots of
a GSO satellite can be associated to a specic TA,
as dened by the Satellite Operator. With NGSO
satellites a dierent approach must be used, with
Earth-xed TAs (based on latitude and longitude co-
ordinates), which remain independent from moving
beams spots.
A mobility aspect to be considered specically NGSO
satellites is the mobility of satellite gNBs, even when
the UE is stationary. This will require the UE to
perform a cell re-selection between the disappearing
serving cell and a new one, possibly emerging in quick
succession above the horizon. However, it is not clear
how eventual coverage gaps between satellites can be
handled, for example with delay-tolerant networking
techniques [54].
Grouping the satellites of a constellation in a single
TA, or groups of TAs, of which a Tracking Area Iden-
tity (TAI) List can be composed by the Access and
Mobility Management Function (AMF) to send to
the UE, is an already existing solution. However, the
drawback is that by using the same TA the UE does
not need perform Mobility Registration Updates and,
therefore, the network will be unaware of the UE’s lo-
cation, which will require it to page over large areas.
If each non-geostationary gNB is assigned a dierent
TAI then the network awareness of UE location is
improved and so is the paging procedure, at the ex-
pense of additional Mobility Registration Update sig-
nalling. Currently, a new paging procedure with min-
imum update signalling is being proposed by 3GPP
as an alternative [55], where the AMF provides the
UE with a list of Registration Areas that should fol-
low each other, in a pre-dened order, as expected in
NGSO satellite constellations.
3.2.2 Access Issues
Radio Access in 5G (NR), was not designed for
NTNs and therefore issues may arise when consider-
ing Satellite links. These issues arise from the speci-
city of propagation channels, with dierent multi-
path delay and Doppler spectrum models, from the
chosen frequency plan and channel bandwidth, from
power limited link budgets, among other aspects.
The Physical Layer of NR needs to be adapted
(e.g. reference signals, preamble sequences, slot ag-
gregation, Physical Resource Blocks, HARQ, among
others), as well as MAC and network layers, in or-
der to support the pairing between UL/DL bands
for Satellite communications (e.g. S and Ka bands).
In particular, appropriate modulation and coding
schemes for low Peak to Average Power Ratio
(PAPR) should be considered in order to guarantee
power savings in the UL [4], which is particularly rel-
evant when considering direct access of IoT devices
in remote locations.
The possible range of maximum one-way delay val-
ues found in satellite access (from 30 ms to 280 ms
depending on altitude) raises questions on the im-
pact on the 5G system, including in the Non-Access
Stratum (NAS), where Session Management and Mo-
bility Management procedures are handled. This de-
lay aects the link between the UE and gNB, as well
as the link between the gNB and the Core Network.
Architectural assumptions to minimise the impact on
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the 5G NAS must be made and certain satellite re-
quirements may also be needed for minimising this
impact.
Latency may also have an impact on 5GSat’s Quality
of Service (QoS) and thus adding a new Radio Access
Technology (RAT) type identier for satellite access
has been proposed. This allows the AMF to deter-
mine the RAT Type so that the Session Management
Function (SMF) is able to impose restrictions on
which QoS proles can be used for Packet/Protocol
Data Unit (PDU) sessions going via the selected
RAT. Similar QoS concerns need to be considered
in 5GSat not only for direct UE-satellite access but
also when using a satellite-based backhaul, where for
example ultra-low latency (e.g. packet delay 5ms)
cannot by supported by GSO satellites.
4 Services and Possibilities
Novel satellite communication systems currently be-
ing planned will ll many of the existing commu-
nication gaps, if deployed. The impact of lling
these gaps spans from cutting Internet-connection
costs for regular households to bringing connectiv-
ity to new areas of the globe. For example, a study
from BroadbandNow, released earlier in 2019, pre-
dicts that households in the US may save up to $30
billion USD due to the entry of one or more alterna-
tive suppliers of broadband. The cost for households
with only one provider is 15% higher than for house-
holds that have access to two providers [56]. Con-
versely, in several remote areas without Internet con-
nectivity – both on land, at sea, and in less-populated
areas as the Arctic and Antarctica – service coverage
would be the main added value.
4.1 Network Architecture Possibilities
Generically, network architectures supported by
satellite systems use satellite link as a backhaul be-
tween the core network, or the Internet, and gateway
nodes compatible with this link. In cellular networks
these nodes correspond base stations (e.g. gNB) for
other nodes to connect. This allows for nodes con-
strained by power or size, among other limitations, to
use dierent radio technologies and remain connected
(e.g. LoRaWAN). As discussed in Section 3, and
illustrated by Figure 1, such backhaul architecture
can be used to enhance 5G coverage. However, there
are alternatives to this solution, which requires pre-
existing gNBs or the deployment of new ones (e.g. in
remote locations or disaster areas).
Figure 2: Transparent architecture
Figures 2 and 3 show the foreseen architecture alter-
natives for satellites as part of 5G networks. The
gures follow 5G nomenclature as dened by 3GPP,
seeking to provide an integration between terrestrial
and non-terrestrial networks, but similar concepts
can be valid for dierent systems as well. In addition,
while the gures depict only one satellite node, the
space segment could correspond to a network or con-
stellation of satellites with or without inter-satellite-
links.
Figure 2 illustrates a bent-pipe satellite architecture,
or transparent architecture, and can be seen as a
generic communication link between a user termi-
nal and a terrestrial 5G base-station (gNB). With
a transparent payload, the satellite is seen as Remote
Radio Head (RRH), which is simpler from the space
segment point-of-view, however it requires an NR-
based interface between the gNB and the RRH. This
NR interface requires additional care since it will be
used in conditions dierent than those for what it was
designed (e.g. longer delays or Doppler shifts). In this
approach, the gNB is connected to the satellite link
via a ground station and the UEs can either directly
connect using the satellite link (Direct Access) or via
a Relay Node (RN). The RN may either be seen as
5G-compatible node that provides a standard 5G in-
terface, or as a gateway for non-5G nodes/sensors.
Using an RN, in both transparent and regenerative
architectures, may reduce some of the dierences be-
tween the two payload options. In particular, an RN
can terminate procedures and air interfaces (up to
Layer 3) and it may also allow for the use of standard
satellite communication links, or an adapted more
suitable NR link for the backhaul (between RN and
a [Donor]gNB), while keeping a standard NR inter-
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face with the UEs. This would limit the impact of
typical satellite channel impairment to this link only
and allow for simpler and more energy-ecient 5G
communication with the UEs.
Figure 3 shows a regenerative satellite architecture
where the satellite acts a 5G base station (gNB).
A regenerative payload typically increases satellite
complexity but it also allows for lower delays since
PHY/MAC procedures (e.g. error correction) can be
locally terminated at the onboard gNB. In addi-
tion, a regenerative payload allows using standardised
satellite-communication technologies for connecting
the satellite with the terrestrial gateway/NGC. Op-
tionally, to simplify the payload, a satellite may only
implement a gNB’s lower-layers, known as a gNB Dis-
tributed Unit (gNB-DU, up to layer 3), and connect
to the corresponding gNB Centralised Unit (gNB-
CU), typically hosted by the gateway.
Figure 3: Regenerative architecture
4.2 Satellite System Architecture
An important focus from 5GSat is the ability to sup-
port mobility and handovers in order to maintain
continuous a link between the UE and the 5G core.
On the other hand, most of the existing or foreseen
IoT Satellite systems typically provide a store-and-
forward type of services, or possible intermittent two-
way communication. Each of these approaches has its
benets and drawbacks, which means that dierent
use-cases may t better or worse.
There are generally two ways of ensuring a contin-
uous link between the user and the core network.
One method is to make use of many ground sta-
tions around the world, so that satellites are able
to directly relay trac between a UE and the net-
work core. This method is used for example by
OneWeb [57]. The second method is to make use of
inter-satellite links (ISL) such that trac is routed
through various satellites until a ground station is
reachable. Iridium and Starlink are examples of such
approach, requiring a lower number of ground sta-
tions. However, satellites supporting ISLs demands
a larger and more capable platform with higher power
and maneuvering/pointing capabilities. This leads to
a complex system design, both for the satellite bus
and operations [57].
As an alternative to ISLs between similar satellites
in one system or constellation, it is also possible to
consider a backhaul network provided by satellites in
a dierent orbit. These can be larger and more com-
plex satellites in orbital planes that will be visible for
a longer period, such as GEO or HEO. Ultimately,
dierent communication possibilities, and satellites
with varied size, cost and complexity, can be com-
bined to address dierent purposes.
Figure 4: Layered satellite architecture
Figure 4 illustrates dierent satellite overlay possi-
bilities, ISL and backhaul, which can be combined
for creating alternative routing paths. This may con-
tribute not only to add robustness to the overlay net-
work but also to explore dierent access options for
UEs. As shown in the gure, in addition to UEs
directly connecting to NGSO satellites (e.g. LEO),
terrestrial gateways (static or mobile) may also sup-
port them by connecting directly to a GSO satellite
backhaul.
Satellites in GEO orbit may be suited for provid-
ing backhaul connectivity since they are perceived
as being stationary and support powerful links, due
to their increased size and capabilities. Elliptical or-
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bits as Highly Elliptical Orbits (HEO) or eccentric
Medium Earth Orbit (eMEO) can also be used, as
they provide coverage over a larger area with only
a few satellites. For example, the Arctic area can
be continuously covered by only two or three HEO
(for example, Molyna or Tundra orbits [58]) or eMEO
satellites. However, the use of GEO satellites may
impose a higher latency than LEO/ISL, depending
on the desired destination. A typical HEO system
will inict a propagation latency similar to, or larger
than, GEO satellites. eMEO-satellites, for example
in a 4-hour orbit, will cause a delay on the order of
30 to 40 ms one way, compared to over 100 ms with
GEO.
4.3 Services and Use Cases
Table 2 shows combinations of use cases that include
a satellite component. The dierent architectures
that we consider are 5G backhaul, 5G/IoT direct ac-
cess to UE and 5G/IoT relayed access to UE. As ear-
lier specied, IoT satellite corresponds to satellite so-
lutions proposed before 5G. On the other hand, while
also support IoT, 5G satellite focuses on the integra-
tion between terrestrial and non-terrestrial networks.
Table 2: Use cases and architectures
5G 5G 5G IoT IoT
backhaul access relay access relay
Two-way Y Y Y / /
comms.
Continuous Y Y Y – –
coverage
Powerful Y Y Y Y
UE
Low-energy / Y / Y
UE
Constrained / Y Y Y
UE
Tracking of Y –
small animals
Sparse / Y –
deployments
Emergency Y / Y – –
deployments
In Table 2 a cell marked with ‘Y’ means that the ar-
chitectural component in the respective column can
support the use case and requirement in the corre-
sponding row. A cell marked with ‘/’ indicates par-
tial support, whereas a cell marked with ‘’ indicates
a poor t.
Dierent scenarios and UE properties are listed in
the table, such as two-way communications (two-
way comms.), continuous coverage,Powerful UEs like
semi-mobile terminals on vehicles or larger sensor sys-
tems, low-energy UEs which can be small sensors de-
ployed around a farm or a facility, constrained UEs
which can be terminals with limited antenna sizes,
tracking of small animals which implies low-energy
and constrained UEs, sparse deployments composed
of UEs for tracking assets or monitoring the environ-
ment, and deployments of emergency base-stations.
The table indicates that non-5G and 5G systems
can oer complementary services, suitable for dif-
ferent needs. It is assumed that small, low-power,
low-rate and sparse sensor deployments will benet
most from tailored or optimized non-5G solutions.
In these cases, the communication links can be tai-
lored to optimize the energy consumption. However,
integrated 5G systems may also oer similar suitable
solutions by using the same radio technologies and
more streamlined approaches. This can be seen, for
example, in the specications of 4/5G Narrowband
IoT (NB-IoT) which does not include handover sup-
port and uses narrower carriers.
5 Conclusions
The potential of satellite solutions for supporting
communications around the world is not new. How-
ever, there has been a signicant increase of lower-
cost solutions compared to the traditional large-scale,
high-cost GEO satellites. In this paper we compare
27 new or developing satellite solutions with dierent
capabilities and explore their potential in supporting
IoT.
While integrating satellite solutions as a backhaul
for terrestrial networks has already been explored in
the past, this has mostly served high-throughput ap-
plications and not focused on the direct support of
UEs. Currently, the integration of terrestrial and
non-terrestrial networks is a building block for 5G
and its ambitions of global coverage.
Regarding the integration of terrestrial and non-
terrestrial networks aspects that need to be re-
searched include the handover support in in NGSO,
which should be quick handovers and scalable. This
concerns the management of tracking and registra-
tion areas, information needed at the AMF, as well
as techniques for handling paging the UEs. From
the communication link perspective, increased prop-
agation delays from NTNs require the adaptation of
MAC/RLC protocols and procedures. However, 5G’s
support of multiple radio access technologies and def-
inition of dierent slices/QoS bearers, among other
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Copyright © 2019 by the Norwegian University of Science and Technology. Published by the IAF, with permission and
released to the IAF to publish in all forms.
functionalities, may help with adoption of this tech-
nology in distinct use cases.
Despite the potential of a 5G solution for providing
IoT around the world, with unied and standardized
approach for UEs and other network components,
several approaches are possible. Dierent architec-
tures and technologies may be more suitable for dis-
tinct use-cases and their requirements. For example,
an integrated 5G satellite solution has the potential
for providing a suitable answer in disaster scenarios
such as oods, avalanches or other natural disasters.
Deploying emergency base stations, or simply using
5GSat as an alternative backhaul link for damaged
terrestrial connections, could mitigate serious com-
munication issues. On the other hand, due to the
fast-paced evolution of the IoT and the wide range
of applications, smaller and more agile satellite sys-
tems, may provide more adequate solutions and push
new technology without going through long and slow
standardization and roll-out phases. However, non-
5G systems may become more dependent on individ-
ual companies and their strategic plans, which leads
to a higher risk of a system becoming discontinued.
The choice between a standalone satellite-IoT and a
5GSat solution signicantly depends on the use case
being considered and on how these technologies may
evolve. We consider dierent network architectures
and use cases, based on currently available or pro-
posed satellite systems, and conclude that use cases
characterized by extremely limited resources and/or
physical constraints will benet from tailored satellite
solutions, despite the integration of terrestrial and
non-terrestrial networks proposed by 5G.
Acknowledgements
This work was funded by the project TEL.01.19.7
“IoT over satellite for remote areas”, funded by the
Norwegian Space Agency and NTNU.
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