3GPP

    the third generation partnership project
3D

    three dimentional
5G

    fifth generation
6G

    sixth generation
AI

    artificial intelligence
AR

    augmented reality
AoA

    angle-of-arrival
AoD

    angle-of-departure
BS

    base station
D-MIMO

    distributed multiple-input multiple-output
EM

    electromagnetic
GDOP

    geometric dilution of precision
GNSS

    global navigation satellite system
HMI

    human-machine interaction
IQ

    in-phase and quadrature
JCS

    Joint Communication and Sensing
ISAC

    integrated sensing and communication
JRC

    joint radar and communication
JRC2LS

    joint radar communication, computation, localization, and sensing
ICI

    inter-carrier interference
IOO

    indoor open office
IoT

    Internet of Things
IRN

    infrastructure reference node
KPI

    key performance indicator
KVI

    key value indicator
LCA

    life cycle analysis
LoS

    line-of-sight
MIMO

    multiple-input multiple-output
mmWave

    millimeter-wave
NLoS

    non-line-of-sight
NR

    new radio
NTN

    non-terrestrial network
OFDM

    orthogonal frequency-division multiplexing
OTFS

    orthogonal time-frequency-space
PRS

    positioning reference signal
QoS

    Quality of Service
RAN

    radio access network
RAT

    radio access technology
RedCap

    reduced capacity
RF

    radio frequency
RIS

    reconfigurable intelligent surface
RTK

    real-time kinematic
RTT

    round-trip-time
SDG

    sustainable development goal
SLAM

    simultaneous localization and mapping
SNR

    signal-to-noise ratio
SIT

    sustainability, inclusiveness, and trustworthiness
SOTA

    state of the art
ToA

    time-of-arrival
TDoA

    time-difference-of-arrival
TR

    time-reversal
TRP

    transmission and reception point
TX/RX

    transmitter/receiver
TX

    transmitter
RX

    receiver
UE

    user equipment
UN

    United Nations
multi-RTT

    multi-cell round-trip-time
UL-TDOA

    uplink time-difference-of-arrival
DL-TDOA

    downlink time-difference-of-arrival
UMi

    3D-urban micro
UMa

    3D-urban macro
UWB

    ultra-wide band
FR1

    frequency range 1
FR2

    frequency range 2

# 6G Positioning and Sensing Through the Lens of Sustainability,
Inclusiveness, and Trustworthiness

Henk Wymeersch, Hui Chen, Hao Guo, Musa Furkan Keskin,
Bahare M. Khorsandi, Mohammad H. Moghaddam, Alejandro Ramirez,
Kim Schindhelm, Athanasios Stavridis, Tommy Svensson, and Vijaya Yajnanarayana

###### Abstract

6G promises a paradigm shift in which positioning and sensing are inherently
integrated, enhancing not only the communication performance but also enabling
location- and context-aware services. Historically, positioning and sensing
have been viewed through the lens of cost and performance trade-offs, implying
an escalated demand for resources, such as radio, physical, and computational
resources, for improved performance. However, 6G goes beyond this traditional
perspective to encompass a set of broader values, namely sustainability,
inclusiveness, and trustworthiness. This paper aims to: (i) shed light on
these important value indicators and their relationship with the conventional
key performance indicators, and (ii) unveil the dual nature of 6G in relation
to these key value indicators (i.e., ensuring operation according to the
values and enabling services that affect the values).

###### Index Terms:

6G, Positioning, Sensing, Performance, Values.

##  I Introduction and Motivation

ISAC is expected to be a major differentiator of 6G when compared to previous
generations [1]. The promises of integrated sensing and communication (ISAC)
include pervasive situational awareness by monostatic, bistatic, and multi-
static _radar-like sensing_ , complemented with extremely accurate _position
and orientation estimation of devices_. These promises are delivered thanks to
a variety of technological advances, including mmWave and sub-THz spectrum,
reconfigurable intelligent surfaces, artificial intelligence (AI), radio
frequency (RF) hardware, etc. In turn, ISAC will enable new applications with
unprecedented demands in terms of the key performance indicators (e.g.,
accuracy, latency, coverage), such as extended reality, digital twinning, and
collaborative robotics [2].

The timing of 6G happens to be well-aligned with the Agenda 2030 for
Sustainable Development by the United Nations (UN). Under this agenda, 17
interlinked sustainable development goals have been defined, which serve as a
“shared blueprint for peace and prosperity for people and the planet, now and
into the future” [3]. 6G can use these SDGs to identify the critical
sustainability areas in which 6G can play an important role. Notably, the
European Hexa-X 6G Flagship project has pinpointed specific SDGs where 6G can
significantly contribute, through the establishment of infrastructures that
promote remote work, privacy-focused designs, eco-design of products, and a
holistic approach towards societal, economic, and environmental
sustainability.

The conventional KPIs focus on functionality and measurable requirements. To
extend this view towards a more comprehensive approach, key value indicators
have been introduced to complement the KPIs and are able to better capture the
spirit of the SDGs [4]. The KVIs have been defined in three categories:
_sustainability_ , _inclusiveness_ , and _trustworthiness_. Hence, the 6G
system should itself meet each of these KVIs, not only during the lifecycle of
its components, but also by enabling services and applications that can, in
turn, improve the KVIs. This vision of 6G positioning and sensing is
visualized in Fig. 1.

In this paper, we aim to describe and structure the KVIs for 6G in the context
of ISAC (i.e., positioning and sensing), reveal their synergies and conflicts,
and propose ways to quantify them (thus effectively turning them into new
KPIs). Each KVI will also be discussed in detail, shedding light on the dual
role of 6G. By integrating these KVIs into the architectural design of 6G
ISAC, we anticipate not only novel research avenues but also the facilitation
of achieving the SDGs.

Figure 1: The vision of 6G positioning and sensing. 6G use cases are
conventionally mapped to positioning and sensing KPIs, which drive the 6G
design. To support a subset of the UN’s SDGs (highlighted: #8 (Sustainable
development), #9 (Industry, innovation, and infrastructure), #11 (Sustainable
cities and communities), #12 (Sustainable consumption and production), #13
(Climate action)), three KVIs (sustainability, inclusiveness, and
trustworthiness) are introduced, which should be integrated with the KPIs.

##  II Performance and Value Indicators

In this section, we elaborate on the 6G use cases and the corresponding KPIs.
Then, we detail the three KVIs and explain the relation to the KPIs.

###  II-A 6G Use Cases and KPIs

Figure 2: 6G use cases and KPIs. Positioning and sensing require a well-
defined process and suitable interfaces to (i) create an ecosystem and (ii)
support the use case clusters (corresponding to the verticals of healthcare,
automotive, industry, and extended reality). The high-level (green) and low-
level (blue) KPIs vary widely depending on the specific use case, with
qualitative shapes shown for 5G (dashed black) and 6G (red).

For the efficient realization of ISAC that can unleash the true potential of
applications and higher-layer services, the 6G architecture necessitates the
incorporation of open and well-defined interfaces (such as those providing raw
or processed measurements) to enable easy data access and flow. This will
catalyze the 6G ecosystem, synergizing sensing, positioning, and services
designed for optimization and analytics. As illustrated in Fig. 2, the typical
6G use cases can be clustered according to the verticals: healthcare,
automotive, industry, and extended reality. According to the use cases, the
corresponding positioning requirements are expected to be tighter than the
ones for the existing 5G standard [2]. Moreover, new sensing requirements must
be introduced in alignment with the specific use cases. Positioning and
sensing information can also be used internally by the 6G system to enhance
and optimize communication functionality, for example using position
information to optimize proactive resource allocation.

Definition of positioning and sensing requirements in 6G is done through the
lens of KPIs, which can be divided into low-level and high-level KPIs. The
low-level KPIs relate to the performance and limitations of the underlying
radio resources and algorithms for positioning and sensing. For example, in
positioning and radar-based sensing, accuracy and resolution of the delay,
Doppler, and angle measurements are the most important KPIs. In contrast, the
high-level KPIs relate to the performance and assessment of the system as a
whole, focusing on the quantities of interest. The most representative
examples of high-level KPIs are positioning accuracy, availability, and update
rate.

The KPIs manifest considerable variations across and within each use case
cluster shown in Fig. 2. For example, in healthcare, the collection of
biomedical samples in remote rural areas using drones requires 3D position
accuracy of around $0.1\,\mathrm{m}$ and an update rate of around
$1\,\mathrm{Hz}$, while remote surgery requires very high positioning accuracy
(approximately $1\,\mathrm{mm}$ in space and $1\,\mathrm{deg}$ in orientation)
and a high update rate. In the extended reality cluster, specifications for
human-machine interface cases like gesture recognition entail additional low-
level KPIs, such as velocity, range, and angle resolution. Meanwhile,
applications like augmented reality impose supplementary high-level KPIs,
encompassing 3D orientation accuracy. Industrial use cases for digital twins
impose requirements on the unambiguous range, range resolution, and Doppler
resolution to ensure sensing and positioning coverage within a factory. In the
automotive space, KPIs such as range and velocity resolution together with
unambiguous range and velocity play a critical role in use cases such as
collision avoidance and platooning.

A comprehensive exploration of the use cases, KPIs, and gap analysis in the
context of 6G positioning and sensing are beyond the scope of this paper, but
an in-depth discussion is available for interested readers in [2].

###  II-B The 6G KVIs Explained

The inception of value-based considerations in 6G, though initially introduced
in [4], has philosophical roots that can be traced to broader social awareness
and responsibility [5]. The concept of _value_ , as delineated by [4],
encompasses “intangible yet essential human and societal imperatives,
including growth, sustainability, trustworthiness, and inclusion.” The
operationalization of these values within the 6G framework necessitates the
formulation and integration of associated criteria, in the design,
functionality, and decommissioning of the system. While [4] refrained from
explicit definitions of these values and the KVIs, we regard them as
analogous. Our objective is to provide useful definitions for each KVI that
are comprehensive yet specific, a task that will be further expounded in the
context of 6G positioning and sensing in the next section.

#### Sustainability111Given that all SDGs are by definition related to
sustainability, a more narrow definition is proposed.

bifurcates into environmental and economic domains. Economic sustainability
pertains to practices that support long-term economic growth, balancing
organizational and societal needs without undermining social, environmental,
and cultural facets [6]. Environmental sustainability was already highlighted
in the 4G era [7], where life cycle analyses indicate that a holistic approach
must incorporate considerations of manufacturing, operational energy
consumption, recycling practices, and end-of-life treatment. However, with 6G
these considerations must be considered already in the design and
standardization phase.

#### Inclusiveness

is multifaceted and aims to foster increased participation and mitigate
digital divides, promoting an equitable technological landscape. Inclusiveness
encompasses accessibility to 6G technologies, education, and facilitation in
their usage, as well as assisting vulnerable demographics, such as the elderly
or infants, and those marginalized due to geography, gender, culture, health,
or education.

#### Trustworthiness

encompasses security (defense against deliberate attacks), robustness
(mitigation of unintentional faults, including environmental disturbances,
human errors, and system malfunctions), and privacy (unauthorized leakage of
sensitive information, whether deliberate or inadvertent) [8]. Notably, the
anticipated pervasive utilization of AI in 6G introduces unprecedented
challenges and considerations in the realm of trustworthiness, necessitating
innovative approaches.

###  II-C Relations Between KPIs and KVIs

The evolution of positioning and sensing paradigms in wireless communication
networks has primarily emphasized satisfying the KPIs tailored for specific
applications. However, responsible deployment of 6G should transcend technical
performance, aligning with global values of sustainability, inclusiveness, and
trustworthiness. An intricate relation exists between the traditional KPIs and
new KVIs, underlined by a multifaceted interplay of trade-offs and synergies,
as visually depicted in Fig. 3. This relationship will be further elaborated
below, incorporating the measurement methodologies for KVIs and exposing the
challenges emanating from potential knock-on effects. The latter signifies
that enhancement in one KVI may result in unintended repercussions in another
KVI, further influencing subsequent KPIs.

####  II-C1 Trade-off between KPIs and KVIs

Achieving a particular KPI might necessitate a compromise on a corresponding
KVI. Pursuing heightened accuracy might demand extensive infrastructure
deployment or resource consumption, undermining sustainability. Consequential
impacts may manifest in reduced trustworthiness (owing to a less diversified
technology ecosystem) and diminished inclusiveness (resulting from
unaffordable services for specific demographics). Conversely, elevating a KVI
may cause conflicts with KPIs. The construction of a trustworthy system,
albeit fostering secure services and long-term reliability, might entail
additional resources or complex algorithms. This, in turn, might introduce
latencies or degrade performance within the given resource constraints,
affecting the associated KPIs.

####  II-C2 Synergy between KPIs and KVIs

Certain scenarios reveal mutual support between KPIs and KVIs. Accurate
position and map information can improve energy efficiency via so-called
channel knowledge maps. Enhancements in positioning and sensing, coupled with
broadened service reach, can promote user inclusiveness. This may, in turn,
catalyze commercialization and privacy through distributed processing, thereby
enabling accurate cooperative positioning. Trustworthiness and sustainability
are valued intrinsically by users, thereby amplifying inclusiveness through
wider adoption. By carefully exploiting these synergies, future networks can
be designed to concurrently optimize both KPIs and KVIs, ensuring both
performance objectives and broader societal benefits are achieved. A salient
instance of this synergy manifests in hardware impairment exploitation, where
attributes of cost-efficient hardware (contributing to sustainability and
inclusiveness) can be harnessed to enhance KPIs, such as sensing accuracy and
unambiguous range [9].

####  II-C3 Quantification of KVIs

While KPIs can offer quantifiable metrics for evaluating positioning and
sensing performance in 6G networks, quantifying KVIs poses a formidable
challenge as they often encompass essential societal values that lack a
rigorous mapping to tangible metrics. New performance metrics of KVIs need to
be defined, which may involve weighing a set of KPIs based on evolving trends
in a specific 6G use case or application [4]. Below are examples of how we can
transform KVIs into actionable KPIs, beyond those shown in Fig. 2:

  * •

Sustainability KPIs: Obvious KPIs include _energy efficiency_ , which is
relatively well-defined for communication, but not for positioning and
sensing, as well as _capital_ (e.g., deployment) and _operational expenses_
(e.g., power consumption of components or systems).

  * •

Inclusiveness KPIs: Possible KPIs include _coverage_ that can be provided
within the legacy KPI (e.g., accuracy and latency) requirements, _cost_ of the
device or service for the end-user, _accuracy_ of new human-machine interfaces
(e.g., via gesture recognition).

  * •

Trustworthiness KPIs: The broad nature of trustworthiness requires metrics
like _position integrity_ to ensure robustness against faults, and security
evaluation through the _probability of undetected attacks and the subsequent
impact_. Privacy considerations may invoke measures such as _differential
privacy_ and _mutual information_ metrics.

Despite these formalized attempts at quantification, the perceived performance
remains inherently subjective, influenced by various factors, including not
only the specific use case, but also background, culture, location,
regulations, and stakeholder structures.

Figure 3: Synergies (green) and trade-offs (red) among KPIs and KVIs,
including higher-order effects. KPIs must be augmented to quantify the KVIs in
6G design, when possible.

##  III The Dual Role of Positioning and Sensing from a KVI Perspective

In this section, we go deeper into each of the KVIs, in order to provide
specific examples of how they relate to positioning and sensing in 6G. For
each KVI, a dual view is taken: (i) how the network can operate in a way that
is aligned with each value, and (ii) how positioning and sensing,
conceptualized as a service, can improve the KVIs, which can be interpreted as
a higher-order effect.

###  III-A Sustainability

Sustainability is arguably among the major concerns in 6G systems, guiding the
entire lifecycle design.

####  III-A1 Sustainable Positioning and Sensing

We consider three dimensions of sustainable design: radio resource
optimization, infrastructure optimization, and the level of integration of
positioning and sensing within 6G communication.

  * •

_Radio resources:_ 6G calls for sustainable designs that are optimized to
reach the target KPIs, rather than over-optimizing the indicators themselves.
Optimization of radio resources considers the KPIs as objective, with an
implicit consideration in terms of sustainability, as the allocated resources
should be as small as possible. However, conservative designs based on over-
provisioning should be avoided in favor of flexible and adaptive resource
allocation schemes, such that energy and resource consumption can be
minimized, while still (exactly) meeting the instantaneous target KPIs.
Complementary to the radio resources, sleep/idle modes should be activated
whenever possible to conserve energy.

  * •

_Infrastructure:_ Positioning and sensing generally require a more extensive
infrastructure deployment than communication. Such an extension is provided in
6G through two emerging technologies: distributed multiple-input multiple-
output (D-MIMO) systems and RISs. In D-MIMO deployments, user equipments are
surrounded by a large number of energy-efficient base stations, providing not
only outstanding performance in communication but also in positioning and
sensing. RIS are a class of low-energy equipment that can replace/complement
location anchors (e.g., BSs) and manipulate the wireless environment [10],
resulting in better propagation channels, especially in the presence of
blockages. Similar to the radio resources, the infrastructure should be
optimized, for instance, the deployment, the manufacturing, and the
replacement possibility of D-MIMO and RIS systems, to improve sustainability
under long-term target KPI requirements.

  * •

_Level of integration:_ One of the key features of 6G is to use resources and
infrastructures for both positioning/sensing and communications, thereby
inherently improving sustainability. The integration of positioning/sensing
and communications can span different levels, from sites, spectrum, and
infrastructure, to waveforms and time/frequency resources, as shown in Fig. 4.
While progressive integration improves sustainability, there are unavoidable
trade-offs in terms of performance. Hence, stringent KPI requirements may not
be suitable for the tightest possible integration.

Figure 4: Different levels of integration between communication, positioning,
and sensing functionalities. Tighter integration is more sustainable but may
come at a penalty in terms of performance (e.g., reduced accuracy or increased
latency).

####  III-A2 Positioning and Sensing for Sustainability

Positioning and sensing, through their ability to understand and digitize the
physical world, provide a unique tool to enhance sustainability. First of all,
by harnessing positioning and sensing information, data communication
sustainability can be improved (e.g., context-aided communication with
proactive resource allocation, beam alignment, and blockage avoidance) [11].
In addition to the more sustainable operation of communication, the ability to
sense and localize has broader sustainability implications, such as earth
monitoring (e.g., the ability to monitor pollution and weather). Recalling the
verticals from Fig. 2, sustainability benefits in healthcare include the
reduction in CO2 emissions thanks to remote surgery and drone deliveries. In
the automotive sector, traffic coordination and platooning can be used to
minimize fuel/battery consumption. In the industry vertical, digital twins
(e.g., twins for manufacturing and autonomous supply chains, twins for
sustainable food production, or twins in the context of immersive smart
cities) can track the position of assets or humans to optimize processes, save
material, and reduce waste or energy per produced item. Finally, in the realm
of extended reality, the ability to collaborate virtually can lead to enormous
CO2 savings, due to reduced ground and air travel.

###  III-B Inclusiveness

In the pursuit of global digital equity, 6G should ensure accessibility to all
humans, irrespective of gender, age, ability, and geographical location [12].
An integral part of this vision is to make the technology affordable,
scalable, and ubiquitous. As such, positioning and sensing are the core
aspects of this inclusive objective.

####  III-B1 Inclusive Positioning and Sensing

Positioning and sensing, embedded in the network architecture, can be
facilitated by network deployment across all geographical terrains. This is
feasible through a combination of several developments: the reuse of
communication resources and infrastructure for multi-purpose functionality,
ubiquitous connectivity, and cooperative networks.

  * •

_Multi-purpose functionality:_ The infrastructure for providing communication
and network services will be repurposed for positioning and sensing functions.
This dual-purpose application obviates the need for additional hardware and
does not necessitate any alterations to the existing communication signals or
protocols. A proof-of-concept for this dual-purpose application is illustrated
in Fig. 5, where communication signals are used to track a person.

  * •

_Ubiquitous connectivity_ : Connectivity is the prerequisite to providing
communication services, which is the main goal of 6G networks. For example,
the incorporation of non-terrestrial networks will significantly extend the
coverage of 6G networks to remote or difficult-to-reach areas, ensuring that
geographical barriers do not limit access to vital communication or sensing
services. Similarly, RISs also enhance and enable accurate and efficient
positioning and sensing in various scenarios, largely extending the coverage
of services [13]. Consequently, ubiquitous connectivity-enabled positioning is
poised to significantly augment the inclusiveness of the 6G network by
enabling uninterrupted connectivity regardless of the users’ proximity to the
traditional network infrastructure.

  * •

_Cooperative networks_ : Sidelink supports direct communication between
devices, bypassing the centralized network infrastructure. This capability can
facilitate the creation of localized communication networks, extending
connectivity and service availability in scenarios where conventional network
coverage may be absent or limited, such as in rural, remote, or disaster-
struck areas. Such a cooperative approach makes positioning and sensing tasks
to be completed in a distributed manner, largely extending the coverage and
reducing the cost of the provided services.

These three aspects underscore how 6G technology will be instrumental in
breaking down existing barriers in network access and functionality,
demonstrating a firm commitment to creating a truly inclusive, global digital
ecosystem.

Figure 5: Proof-of-concept for joint communication and sensing, showing how
existing communication infrastructure and signals can be repurposed for
sensing, in support of sustainability and inclusiveness. The hardware
comprises Sivers semiconductors EVK06002 as TX and RX, each with 1×16 arrays.
Standard 5G waveform with 120 kHz subcarrier spacing, 800 MHz bandwidth, 69
GHz carrier frequency, and 64 QAM modulation are employed. Besides the data
transmission (top middle), beam sweeping (top left) provides bearing
measurement of the passive target. Bistatic time measurements provide a
sensing ellipse to further improve the target position estimate (bottom left).

####  III-B2 Positioning and Sensing for Inclusiveness

Inclusiveness in 6G networks is not only a macro-level objective but also
addresses the accessibility challenges encountered at the micro-level of
individual human-machine interactions. Positioning and sensing can play a
crucial role in this context. On the one hand, advancements in sensing
technology will enable systems that can interpret and respond to gestures,
which benefits individuals who face challenges in traditional interaction
modalities. Such a transformation can redefine the nature of human-machine
interaction, making it more inclusive and accessible. On the other hand,
intelligent monitoring, especially in critical societal domains such as
elderly care, patient supervision, and infant care, emerges as a domain where
sensing can be a game-changer. Such integrative applications promise to
redefine caregiving, providing options characterized by precision, real-time
feedback, and remote monitoring. These developments serve to enhance the
quality of life for these demographic segments, underlining 6G’s commitment to
be genuinely inclusive and beneficial to all of society. Referring back to the
proof-of-concept demonstration from Fig. 5, a person can be tracked in a
cluttered environment with the aid of communication signals and
infrastructure, negating the need for additional equipment or invasive
monitoring techniques.

###  III-C Trustworthiness

Ensuring the robustness, security, and privacy of 6G positioning and sensing
must be a priority in the design of the overall 6G system, given the safety-
critical nature of the verticals highlighted in Fig. 2. This section outlines
challenges and approaches related to the trustworthiness of positioning and
sensing in 6G.

####  III-C1 Trustworthy Positioning and Sensing

We deconstruct trustworthiness into its constituent elements, such as
robustness, security, and privacy, before discussing the influence of AI on
them separately.

  * •

_Robustness:_ Robust positioning and sensing are primarily based on diversity,
relying on a large set of measurements from independent technologies,
observations, or dimensions, to provide redundancy for detecting and
eliminating faults. This approach is common in global navigation satellite
system (GNSS), where for instance, aviation applications demand protection
levels with a high degree of certainty, even in the presence of faults. The 6G
system itself can provide inherent redundancy, via diverse measurements (e.g.,
not only time-difference-of-arrival (TDoA), but also angle-of-arrival (AoA),
angle-of-departure (AoD), carrier phase, and perhaps Doppler), diverse
location references (e.g., using many access points in D-MIMO), and multi-
sensor fusion (e.g., relying on a combination of 6G sensing with vision). When
combined with integrity monitoring, 6G can provide high performance with
guaranteed robustness [14].

  * •

_Security:_ Vulnerabilities exist in classical positioning technologies (e.g.,
GNSS and ultra-wide band (UWB)), where attackers can perform jamming (blinding
the receiver, leading to service interruption), meaconing (retransmission of
legitimate signals), or spoofing (transmission of false signals)[15]. Spoofing
can be mitigated by cryptographic countermeasures, while jamming can be
mitigated by directional nulling at the receiver. Attacks on radar sensing
include jamming, altering electromagnetic properties, deception, masking, and
imitation. Adaptive waveform design and frequency hopping help correct target
range or velocity errors. Extrapolating these concepts to 6G, it is clear that
each measurement type (delay, angle, Doppler), each piece of hardware (BS,
RIS, UE), and each waveform have potential security weaknesses that can
compromise positioning and sensing. An example of a positioning and sensing
attack in a 6G context is shown in Fig. 6, where an attacker manipulates the
TX beamforming, which leads to perceived high-power paths at the RX with
modified AoD (with limited knowledge at the attacker) or AoA (with complete
knowledge at the attacker).

  * •

_Privacy:_ Privacy protection in the area of location tracking of humans is
already crucial for 5G and comes even more into focus with 6G’s higher
positioning accuracy, its opportunities for cross-platform fusion of tracking
information, and exposure framework for internal and external use (see Fig.
2). Position information that can be easily used for behavioral profiling must
be secured from unauthorized access on all levels (including physical-layer
security). Moreover, not only tracking of humans is possible but tracking of
objects and assets as well. In corporate environments, where asset tracking is
used to monitor and optimize processes, this process information becomes
worthwhile protecting as well. Technological protection includes solutions
like active cloaking, reminiscent of techniques in electronic warfare.

In the context of the trustworthiness of 6G, the advent of AI possesses the
potential to instigate novel attacks, exploiting latent system
vulnerabilities. Conversely, AI can fortify system security and privacy by
innovating newly learned protocols or waveforms. However, the opaque nature of
AI mechanisms demands rigorous and transparent scrutiny to ensure stakeholders
are well-informed of the associated risks, especially for safety and mission-
critical tasks. Explainable and model-based AI can help address this concern
from a technical perspective.

Figure 6: A 6G ISAC attack example, where a transmitter modifies its
beamforming vector to fool an analog/hybrid receiver into believing there are
additional (strong) paths at arbitrary AoD or AoA, shifted $\pi/4$ in each
domain with respect to the LoS path at AoD and AoA of $0$ radians.

####  III-C2 Positioning and Sensing for Trustworthiness

The ability to localize users and objects with a high degree of accuracy can
support applications that rely on trustworthiness. First of all, in terms of
robustness, 6G will act as an additional sensor, complementing and verifying
existing sensors (e.g., camera, GPS, lidar, radar, inertial measurement unit).
This will benefit all safety-critical services (including the corresponding
communication), where incorrect location information may lead to harm.
Secondly, security functions can be based on accurate location information or
biometric 6G sensing data can be employed in access control or payment
services. Given the built-in encryption and security frameworks, 6G data is
poised to receive greater trust than other sensory inputs, driving the
emergence of novel applications. Lastly, surveillance and crowd control
applications are envisioned to benefit immensely from the sensory data
facilitated by 6G.

Figure 7: Selected enablers for 6G positioning and sensing in terms of the
impact on the KVIs.

###  III-D Impact of 6G Enablers on the KVIs

To conclude this section, we offer an analytical examination of various
technological enablers pertinent to 6G positioning and sensing, referencing
insights from [2]. These enablers include RIS, NTN, sidelink, AI, D-MIMO, and
sub-THz signals. Until now, our discussion has largely highlighted the
advantageous aspects of these enablers. However, as shown in Fig. 7, it is
crucial to recognize that each enabler also bears inherent challenges and
costs in relation to each KVI. Some of these associated costs emanate from
higher-order effects, underscoring the intricate and multifaceted nature of 6G
system design. It is paramount that 6G design and implementation consider not
just the direct benefits (KPIs) but also potential drawbacks (KVIs) –
optimally mapping the latter to quantifiable KPIs while concurrently
navigating these higher-order effects.

##  IV Outlook

The evolution of precise positioning and sensing for 6G ISAC presents a set of
challenges and opportunities. As this paper has underscored, the next
generation of digital communication is not merely about advancing the
traditional KPIs, but also to forge a digital ecosystem that is sustainable,
inclusive, and trustworthy, in line with the UN’s SDGs. We have shown that
these values should be related to KVIs, which in turn can be mapped to new
KPIs. Both synergies and trade-offs will occur, and higher-order effects
should be considered. For each of the KVIs, this paper has revealed the
intricate nature of 6G positioning and sensing, both to make positioning and
sensing coalesce with the KVIs, and to provide services that enhance the KVIs.

As we stand on the cusp of the 6G era, it has become clear that the adoption
of a holistic approach is imperative. As researchers, developers, and
stakeholders, our task is not only to innovate, but also to ensure that the
digital future is sustainable, inclusive, and trustworthy.

## Acknowledgments

This work was supported, in part, by the European Commission through the H2020
project Hexa-X (Grant Agreement no. 101015956). The authors are grateful to
Hamed Farhadi (Ericsson) for his comments on the manuscript.

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Henk Wymeersch is a Professor with the Department of Electrical Engineering at
Chalmers University of Technology, Sweden, in the area of radio localization
and sensing.
---
Hui Chen is a postdoc with the Department of Electrical Engineering at
Chalmers University of Technology, Sweden, focusing on mmWave/THz localization
and sensing.
---
Hao Guo is a postdoc with the Department of Electrical Engineering at Chalmers
University of Technology, Sweden, focusing on wireless backhaul and sensing-
aided communication systems.
---
Musa Furkan Keskin is a Research Specialist at Chalmers University of
Technology, Sweden, focusing on integrated sensing and communications with
hardware impairments in beyond 5G/6G systems.
---
Bahare M. Khorsandi, is a Core Network Specialist at Nokia Strategy and
Technology in Munich, Germany, working on 6G network architecture design.
---
Mohammad H. Moghaddam is a Research Specialist and joint communication and
sensing expert at QAMCOM Research and Technology AB, Gothenburg, Sweden.
---
Alejandro Ramirez is a Senior Key Expert at Siemens’ corporate research unit
in Munich, Germany, working on wireless communication and localization.
---
Kim Schindhelm is a Research Scientist at Siemens’ corporate research unit in
Munich, Germany, working on localization.
---
Athanasios Stavridis is a Senior Researcher at Ericsson Research, Ericsson,
Sweden, working in the field of signal processing for wireless communication
and sensing.
---
Tommy Svensson is a Professor with the Department of Electrical Engineering at
Chalmers University of Technology, Sweden, in the area of wireless systems.
---
Vijaya Yajnanarayana is a Master Researcher at Ericsson Research, India,
working in the area of radio signal processing and artificial intelligence.
---
  *[ISAC]: integrated sensing and communication
  *[AI]: artificial intelligence
  *[RF]: radio frequency
  *[UN]: United Nations
  *[SDGs]: sustainable development goal
  *[KPIs]: key performance indicator
  *[KVIs]: key value indicator
  *[KVI]: key value indicator
  *[KPI]: key performance indicator
  *[D-MIMO]: distributed multiple-input multiple-output
  *[RISs]: reconfigurable intelligent surface
  *[BSs]: base station
  *[RIS]: reconfigurable intelligent surface
  *[TX]: transmitter
  *[RX]: receiver
  *[GNSS]: global navigation satellite system
  *[TDoA]: time-difference-of-arrival
  *[AoA]: angle-of-arrival
  *[AoD]: angle-of-departure
  *[UWB]: ultra-wide band
  *[BS]: base station
  *[UE]: user equipment
  *[LoS]: line-of-sight