Work package WP3 – PHY and MAC enablers
WP3 focuses on the design of PHY and MAC enablers for supporting extreme communication requirements for in-X subnetworks. The objectives of WP3 are:
- Identify PHY enablers for supporting ultra-low latencies and/or extreme reliability, also exploiting macro-diversity solutions for achieving robustness to blockage.
- Developing novel beam steering/focusing initial access procedures suitable for 6G-SHINE subnetworks with devices of low complexity, e.g., based on hybrid beam forming capabilities.
- Provide sub-THz system models and hardware abstractions supporting PHY design.
- Develop a jamming resilient PHY interface and novel channel access mechanisms for the operation in unlicensed spectrum.
- Study ad hoc schemes for multiplexing of services with diverse air interface requirements within subnetworks.
- Design of data-driven and AI-powered predictive scheduling schemes to support mixed traffic flows in 6G-SHINE subnetworks and guarantee bounded service delivery.
- Identify the most appropriate RIS technologies for in-X subnetwork scenarios along with their describing models.
- Extend the PHY/MAC protocols as well as CSI estimation schemes to account for the presence of RISs.
- Design of RIS configuration and deployment strategies aimed at minimizing the outage and the interference.
This task addresses the design of robust (e.g., natively robust to jamming) and efficient PHY suitable for/and
exploiting the in-X subnetwork characteristics. Novel mechanisms for data and reference sequences multiplexing will
be investigated, as well as multi-link extension of PHY (macro diversity), along with new methods for data detection
with ultra-short transmissions and performing fast beam steering and beam focusing with minimum overhead.
Subtask 3.1a: Radio interface enablers for ultra-reliable, ultra-short transmissions in subnetwork scenarios.
This subtask includes studies for addressing the main PHY challenges for supporting ultra-short transmissions with
extremely low latency and reliability in potentially interference-limited environments. COGN will look into disruptive
approaches for multiplexing of low overhead reference sequences with data leveraging the time/frequency characteristics
of in-X deployments, as well as on receiver processing algorithms for ensuring high reliability while relying on limited
reference sequences overhead based, for instance, on compressed sensing and AI processing. CNIT will investigate
the impact of near-field propagation conditions on channel response acquisition and associated overhead accounting
for HW constraints as well as joint communication and channel tracking schemes. Sony will study the possibility of
having multiple transmissions of the same packet in spite of the tight latency target, by leveraging fast HARQ feedbacks
enhanced by predictive retransmissions.
Related TCs: TC4.
Subtask 3.1b: Intra-subnetwork macro-diversity and cooperative schemes.
This subtask will focus on the design of macro-diversity and cooperation solutions for achieving spatial diversity in
subnetworks, in order to obtain robustness to blockage effects.
FHG will investigate methods to exploit spatial diversity via the PHY multi-links and via subnetwork devices in range
by using cooperative mechanisms. This will be done in view of the extreme requirements regarding cycle time, latency
and reliability. AAU will look into novel macro-diversity solutions with super-fast signal forwarding methods, where
secondary nodes can retransmit signals via amplify and forward on a sample basis rather than a packet basis. Also, joint
precoder design of primary and secondary AP will be considered using minimal feedback overhead, by exploiting the
expected large-scale fading correlation of devices. COGN will contribute to cooperative medium access protocols in the
unlicensed or other bands relying on ultra-reliable diversity and cooperative solutions such as blind repetition techniques.
Related TCs: TC8.
Subtask 3.1c: Jamming-robust native PHY design.
This task aims to make the 6G-SHINE subnetwork radio interface natively robust to jamming and malicious attacks. This
includes making the control and data channel transmissions time and frequency locations as unpredictable as possible for
an external observer/attacker not authorized to be a part of the in-X 6 subnetwork, while limiting operational complexity
and energy consumption at the devices. AAU and IMEC will look into new approaches for data and control channel
mapping in a frame for the sake of achieving robustness to such jammers. Objective of the research is to design solutions
that are able to address the trade-off between robustness to jamming and low implementation complexity.
Related TC: TC6.
Subtask 3.1d: Native support of low complexity beam forming and beam aware scheduling.
Though devices and APs in subnetworks will have small form factor, they should be able to accommodate at least one
antenna panel whose degree of freedom can be exploited for improving the received signal quality in the direction of
interest. The subtask will cover both initial beam alignment, tracking of beam-pairs and recovery mechanisms if the
signal degrades significantly on a beam-pair. Nokia and IDE will research low-overhead and fast beam alignment for
the in-X subnetworks. Nokia also intends to study how a fast beam recovery can be achieved, such that communication
over the beam formed link is not interrupted. This includes a study on how beam management can be done together with
multi-AP diversity (as studied in subtask 3.1b).
6G in-X subnetwork APs can be capable of hybrid/digital beam forming functionalities, while subnetwork devices will
only be equipped with analog beam forming capabilities and will be resource constrained. To this regard, leveraging
the short-distance communication range and dense deployment characteristics of these networks, IDE will explore
coordinated hybrid beamforming techniques for maximum bandwidth utilization and reduced interference among the
The subtask will consider both the feasibility of beam forming and beam focusing, where the latter shows a high potential
for being able to isolate the beams even for devices in close proximity. Beam focusing is challenging in the need for
accurate channel estimation (CSI) and angle-of-arrival estimation and hence CNIT will study techniques capable to move
part of the processing at electromagnetic (EM) level by exploiting intelligent metasurfaces with the purpose to tackle
complexity, energy consumption, and size issues and reduce significantly the latency. Further, CNIT will investigate the
adoption of metasurface-based antenna arrays to enable native self-beam alignment and low-latency initial access. Sony
intends to investigate benefits of AP awareness of the UE antenna implementation, i.e., how much about the device’s
antenna implementation is meaningful for the AP to know/be able to configure.
Related TC: TC5.
Subtask 3.1e: Sub-THz PHY System Models and Abstractions
While PHY models for centimeter-wave and mmWave bands are well known, new abstraction models of the PHY
performance and power consumption are needed when moving to sub-THz frequencies, due to specific hardware and
propagation behavior, such that realistic and efficient solutions can be designed. End-to-end models assess the PHY
link performance (e.g., bit error rate or equivalent metric) based on realistic models of propagation, analog hardware
non-idealities and related signal processing at transmitter/receiver side. They are used to select and optimize the
related algorithms, by simulating them under realistic conditions. In parallel, power consumption models are needed
to assess the expected energy efficiency of different architectures. They are created for systems combining digital
and analog components, including new sub-THz hardware solutions. Power consumption models quantify trade-offs
when dimensioning architectures or considering various technology options. In this subtask, IMEC investigates: (i) a
power model of the full system (analog front-end, power amplifiers, digital processing) with different architectures
and technology options, (ii) a link-level PHY simulator including realistic models of processing, propagation and nonidealities,
and (iii) optimized architectures based on trade-offs assessed by combining those power and performance
Related TCs: TC3.
This task deals with improved MAC protocols capable of managing heterogeneous services, including those with extreme
requirements in terms of latency or data rates, while maintaining the expected quality of service in licensed and unlicensed
spectrum. Within this context, the design of proactive and predictive interference-robust scheduling algorithms will be
addressed. This may consider in-X subnetworks where the AP can be capable of full or flexible duplexing, and the
devices may be limited to half-duplex transceiver capabilities.
Subtask 3.2a: Enhanced multiple access procedures for service multiplexing and reduced latencies.
This subtask will seek to develop new medium access enhancements for multiplexing services with diverse requirements
in terms of cycle time, latency, data rate (for example, high throughput services together with control cycles of sub-ms
duration). Specifically, AAU will develop new scheduling mechanisms leveraging flexible/full duplex capabilities of the
AP. Such capabilities open up new opportunities for coexistence of traffic with tight periodicity (and therefore frequent
UL/DL switch) with high data rate traffic which were not exploited earlier. The proposed design aims at significantly
lower latencies with respect to known TDD and dynamic TDD approaches, without additional complexity at the device
side. UMH will work on the integration and joint evaluation of full and/or flexible duplexing solutions developed in this
task into predictive scheduling mechanisms of Task 3.2b for enhanced service multiplexing and reduced latencies.
Related TCs: TC9.
Subtask 3.2b: Proactive and predictive interference-robust scheduling algorithms.
In this subtask, AAU and UMH will design data-driven and AI/ML-powered predictive scheduling and pre-allocation
mechanisms to support mixed traffic flows (including deterministic time-sensitive services) in 6G-SHINE subnetworks.
To this aim, they will exploit the subnetworks’ traffic datasets and characterization performed in Task 2.1b. It will
leverage service/application-domain information to derive correlations and predictability of traffic patterns generated by
the highly localized 6G in-X devices (e.g., sensors/actuators) that will be used to anticipate radio resource requests.
Related TCs: TC10.
Subtask 3.2c: Novel access schemes in unlicensed spectrum for in-X subnetworks.
This subtask will consider the so-called green-field spectrum, that is currently not deployed for unlicensed
communication and develop new channel access mechanisms suitable for in-X subnetworks while ensuring fairness
among devices. IMEC and COGN plan to design a novel MAC architecture aiming to support low latency, interference
free operation within the subnetwork but also when external interference/heterogeneous incumbent technologies are
present. They will investigate advanced 6G listen before talk (LBT) and beyond LBT procedures for periodic and latency
critical traffic. The proposed solutions could be evaluated also for general use in ISM bands.
Related TCs: TC11.
RIS are promising technology components for in-X subnetworks whose nature allows for a low-cost installation, e.g.
trunk in a car, or in industrial production modules. The objective of this task is to: i) identify the most appropriate RIS
technologies for in-X subnetworks scenarios along with their describing models; ii) extend the PHY/MAC protocols as
well as CSI estimation schemes investigated in the previous tasks to account for the presence of RISs; iii) Design of RIS
configuration and deployment strategies aimed at maximizing the link availability and minimizing the interference.
Subtask 3.3a: Identification of RIS technologies for the considered in-X subnetwork scenarios
The most appropriate RIS technologies to be tailored to the specific characteristics of subnetworks, where devices
might be located at a very close distance and experience very similar large-scale conditions, will be identified. For each
technology, CNIT and Sony will derive the most appropriate evaluation models as well as for various components, e.g.,
antennas, phase shifters, amplifiers, etc., as a trade-off between the capability to capture the main EM characteristics
(e.g., parasitic modes, diffraction, scattering) and for analytical simplicity. Sony can also perform fullwave simulations
of realistic implementations.
Related TCs: TC7.
Subtask 3.3b: RIS aware PHY and MAC protocols
IDE and COGN will investigate RIS beamforming, configuration, channel estimation, control signaling. Reinforcement
learning techniques will be developed for RIS configuration, channel estimation, and PHY/MAC procedures to deal
with the huge number of parameters to be optimized arising from the presence of RIS. Optimization algorithms to
configure the RISs to minimize the network outage, by exploiting only the statistical characterization of the locations
and movement prediction of devices, will be studied by CNIT. Sony intends to study the advantages of RIS aware PHY
layer when operated in near-field. Finally, CNIT will design ad hoc instantaneous, two-step, and long-term RIS-aware
CSI estimation schemes, based on location information and real-time ray launching (see subtask 2.2b).
Related TCs: TC7.
Subtask 3.3c: RIS deployment and interference mitigation strategies
RIS deployment strategies and optimization reconfiguration algorithms will be studied to minimize the outage and
mitigate the interference in case of multiple RIS and in-X subnetworks according to the scenarios defined in WP2. In
particular, IDE will explore distributed and coordinated interference management techniques for various RIS deployment
scenarios, while considering the limitations and overhead in the control channeling between RIS and the transmit and
receive entities. To reduce the optimization complexity, CNIT will consider alternating optimization methods, where RIS
configuration, deployment, and transmitter/receiver configuration are optimized in an iterative manner. In this context,
Sony intends to study interference mitigation strategies suitable for in-X subnetworks accounting for spurious emissions
and unwanted reflections due to RISs using the models developed in Task 2.2b using analytical and simulation tools
to assess performance.
Related TCs: TC7.