Antenna Array In-Situ Calibration through Source Reconstruction

Take the opportunity to develop a motivating career path in a multidisciplinary scientific community at the cutting edge of technological research at CEA Grenoble, as part of an internationally renowned R&D team in the field of antennas.

PhD Subject:
In many advanced applications (radar, direction finding, electromagnetic -EM- context monitoring), precise knowledge of antenna radiation rules the accuracy of processing (angular direction, polarization of received signals). The integration of miniature antennas on objects or vehicles of a few wavelengths largely impacts their radiation pattern. Particularly in low-frequency bands, antenna calibration is not sufficient to achieve the best levels of performance, let alone robustness over time.
The challenge of the proposed PhD is to be able to update the antenna array far-field calibration table in situ (i.e., in near-real time). To do this, the first part on EM analysis will be based on an exhaustive analysis of the equivalent modes/sources induced on the carrier structure via EM simulations, with the aim of extracting the modes present and their radiation. A second part dealing more with RF instrumentation will size and develop an array of spatial sampling probes installed on the structure of the carrier, which will measure the weightings of these modes in situ. Finally, the last part will hybridize the two previous parts in order to reconstruct the far-field radiation by weighting the simulated modes by the measured points.
During the final year, an experimental implementation will be used to validate the methodology and to analyze its performance.
This subject (EM simulation of antennas, EM analyses, RF measurements) will be supervised by an experienced team relying on exceptional tools and instruments (http://www.leti-cea.fr/cea-tech/leti/english/Pages/Applied-Research/Facilities/telecommunications-platform.aspx).

Applicant Profile: Engineer School or Master with major on Antenna, Electromagnetism, RF instrumentation

Laboratory: CEA Grenoble, heart of the French Alps
(http://www.youtube.com/watch?v=bCIcNJOzYZY)
The CEA is a major research organization working in the best interests of the French State, its economy and citizens. Thanks to its strong roots in fundamental research, it is able to provide tangible solutions to meet their needs in four key fields: Low-carbon energy (nuclear and renewable), Digital technology, Technology for medicine of the future, Defense and national security.
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Super-gain miniature antennas with circular polarization and electronic beam steering

Antenna radiation control in terms of shape and polarization is a key element for future communication systems. Directive compact antennas offer new opportunities for wireless applications in terms of spatial selectivity and filtering. This leads to a reduction in electromagnetic pollution by mitigating interferences with other communication systems and reducing battery consumption in compact smart devices (IoT), while enabling also new use modes. However, the conventional techniques for enhancing the directivity often lead to a significant increase of the antenna size. Consequently, the integration of directional antennas in small wireless devices is limited. This difficulty is particularly critical for the frequency bands below 3 GHz if object dimensions are limited to a few centimeters. Super directive/gain compact antennas with beam-steering capabilities and operating on a wideband or on multi-bands are an innovative and attractive solution for the development of new applications in the field of the connected objects. In fact, the possibility to control electronically the antenna radiation properties is an important characteristic for the development of the future generation and smart communication systems. CEA Leti has a very strong expertise in the domain of superdirective antennas demonstrating the potentials of the use of ultra-compact parasitic antenna arrays. This PhD project will take place at CEA Leti Grenoble in the antennas and propagation laboratory (LAPCI). The main objectives of this work are: i) contribution to development of numerical tools for the design and optimization of superdirective compact arrays with beam-steering capabilities; ii) the study of new elementary sources for compact antenna arrays; iii) the realization and experimental characterization of a supergain compact array with circular polarization and beam-steering capabilities. This work will combine theoretical studies and model developments, antenna design using 3D electromagnetic software, prototyping and experimentations.

Advanced RF circuit design in a system and technology co-optimization approach

This thesis addresses the two major challenges facing Europe today in terms of integrating the communication systems of the future. The aim is to design RF integrated circuits using 22nm FDSOI technology in the frequency bands dedicated to 6G, which will not only increase data rates but also reduce the carbon footprint of telecoms networks. At the same time, it is essential to consider the evolution of silicon technologies that could improve the energy efficiency and effectiveness of these circuits. This work will be carried out with an eye to the design methodology of radio frequency systems.
Within the framework of the thesis, the objective will be broken down into three phases. Firstly, simulation tools will be developed to predict the performance of Leti's future 10nm FDSOI technology. The second stage will involve identifying the most relevant architectures available in the literature for the application areas envisaged for the technology. A link with upstream telecoms projects will be systematically established to ensure that the candidate understands the systems' challenges.
Finally, in order to validate the concepts developed, the design of an LNA and a VCO as part of an ongoing project in the laboratory will be proposed.

The candidate will join a large team that works on new communication systems and addresses aspects of architectural study, modeling and design of integrated circuits. The candidate must have serious skills in the design of integrated circuits and radio frequency systems as well as good ability to work in a team.

A formal framework for the specification and verification of distributed processes communication flows in clouds

Clouds are constituted of servers interconnected via the Internet, on which systems can be implemented, making use of applications and databases deployed on the servers. Cloud-based computing is gaining in popularity, and that includes the context of critical systems. As a result, it is useful to define formal frameworks for reasoning about cloud-based systems. One requirement about such a framework is that it enables reasoning about the concepts manipulated in a cloud, which naturally includes the ability to reason about distributed systems, composed of subsystems deployed on different machines and interacting through message passing to implement services. In this context, the ability to reason about communication flows is central. The aim of this thesis is to define a formal framework dedicated to the specification and verification of systems deployed on clouds. This framework will capitalize on the formal framework of "interactions". Interactions are models dedicated to the specification of communication flows between different actors in a system. The thesis work will study how to define structuring (enrichment, composition) and refinement operators to enable the implementation of classical software engineering processes based on interactions.

Disruptive RF Transceivers for Full Duplex 6G Communications

This thesis is an opportunity to participate in the development of future telecommunications systems in the 10-15 GHz band, in partnership with the best research centers in Europe working on the subject.
Over the past 20 years, wireless communications systems have continued to evolve and offer new services. Today, such is their success that frequency bands below 10 GHz are saturated, and the focus is now on higher frequencies.
To maintain sufficient range, beamforming is needed to compensate for the higher attenuation associated with propagation. Beamforming architectures are often costly in terms of power consumption and generate losses when implementing phase shifters, but they are also a tremendous opportunity for innovation. What's more, the development of 6G can only be achieved by significantly reducing base station power consumption and adding new functionalities such as full duplex (using the same band to receive and transmit simultaneously). To achieve these ambitious goals, new architectures need to be developed, and this is the aim of the European project that brings together Ericsson (Sweden), ETH Zurich (Switzerland), the University of Twente (Netherlands) and CTTC (Spain). The candidate will therefore be working in an ambitious context with partners of excellence.

Scalability of the Network Digital Twin in Complex Communication Networks

Communication networks are experiencing an exponential growth both in terms of deployment of network infrastructures (particularly observed in the gradual and sustained evolution towards 6G networks), but also in terms of machines, covering a wide range of devices ranging from Cloud servers to lightweight embedded IoT components (e.g. System on Chip: SoC), and including mobile terminals such as smartphones.

This ecosystem also encompasses a variety of software components ranging from applications (e.g. A/V streaming) to the protocols from different communication network layers. Furthermore, such an ecosystem is intrinsically dynamic because of the following features:
- Change in network topology: due, for example, to hardware/software failures, user mobility, operator network resource management policies, etc.
- Change in the usage/consumption ratio of network resources (bandwidth, memory, CPU, battery, etc.). This is due to user needs and operator network resource management policies, etc.

To ensure effective supervision or management, whether fine-grained or with an abstract view, of communication networks, various network management services/platforms, such as SNMP, CMIP, LWM2M, CoMI, SDN, have been proposed and documented in the networking literature and standard bodies. Furthermore, the adoption of such management platforms has seen broad acceptance and utilization within the network operators, service providers, and the industry, where the said management platforms often incorporate advanced features, including automated control loops (e.g. rule-based, expert-system-based, ML-based), further enhancing their capability to optimize the performance of the network management operations.

Despite the extensive exploration and exploitation of these network management platforms, they do not guarantee an effective (re)configuration without intrinsic risks/errors, which can cause serious outage to network applications and services. This is particularly true when the objective of the network (re)configuration is to ensure real-time optimization of the network, analysis/ tests in operational mode (what- if analysis), planning updates/modernizations/extensions of the communication network, etc. For such (re)configuration objectives, a new network management paradigm has to be designed.

In the recent years, the communication network research community started exploring the adoption of the digital twin concept for the networking context (Network Digital Twin: NDT). The objective behind this adoption is to help for the management of the communication network for various purposes, including those mentioned in the previous paragraph.

The NDT is a digital twin of the real/physical communication network (Physical Twin Network: PTN), making it possible to manipulate a digital copy of the real communication network, without risk. This allow in particular for visualizing/predicting the evolution (or the behavior, the state) of the real network, if this or that network configuration is to be applied. Beyond this aspect, the NDT and the PTN network exchange information via one or more communication interfaces with the aim of maintaining synchronized states between the NDT and the PTN.

Nonetheless, setting up a network digital twin (NDT) is not a simple task. Indeed, frequent and real-time PTN-NDT synchronization poses a scalability problem when dealing with complex networks, where each network information is likely to be reported at the NDT level (e.g. a very large number of network entities, very dynamic topologies, large volume of information per node/per network link).

Various scientific contributions have attempted to address the question of the network digital twin (NDT). The state-of-the-art contributions focus on establishing scenarios, requirements, and architecture for the NDT. Nevertheless, the literature does not tackle the scalability problem of the NDT.

The objective of this PhD thesis is to address the scalability problem of network digital twins by exploring new machine learning models for network information selection and prediction.

Analysis, compensation and use of beam-squint for wideband mmWave/sub-Thz communications

The ever-increasing demand for data traffic pushes communication systems to upgrade, networks to densify and thus being more and more power-hungry. How to satisfy this need of high connectivity while limiting the carbon footprint of telecommunication systems?

To this end, the combination of the rise in frequency into the upper spectrum (mmWave/sub-Thz) and hybrid (analog/digital) MIMO architectures has emerged from recent research topics. However, with the rise in frequency and bandwidth enlargement, unwanted effect, such as beam squinting, appears and limits the performance of communication systems. Their characterisation and compensation is a trendy topic with a growing number of scientific publications.
The proposed thesis subject aims at first properly modelling to propose innovative compensation techniques. In a second time, we will investigate the possibilities to control side beams for tracking or sensing purposes. The proposed study is on the border between antenna design and digital signal processing. Pioneering antenna systems and innovative signal processing modules will be considered.

At Grenoble (France), we are about to join a dynamic “Telecom” team with a large set of competences ranging from propagation analysis, RF circuit and antenna design and modem/DSP specifications and optimisations. Beside, the thesis is 100% funded by “France 2030” and the national research program “PEPR-Réseaux du futur” which gives the ph.d students the chance to share and present their results to major French research laboratories. The position is available for autumn 2024.

Integration of communication and localization/sensing in distributed wireless networks

The proposed PhD study focuses on the integration of sensing and communication (ISAC) functionalities in next-generation wireless networks. According to this new ISAC paradigm, communication networks should be “spatially aware”, i.e. capable of autonomously retrieving information regarding their operating context and/or physical environment, such as the positions/velocity of end-user terminals and non-connected objects, the room shape, the presence of obstacles… On the other hand, future networks are also expected to be less centralized but more cooperative, while aiming at lower latency, better adaptability to users’ actual needs, and better resilience against local service outages.

In this PhD program, we ambition to explore and evaluate new distributed forms of ISAC. First, cooperative localization, detection and mapping algorithms will be specifically designed, taking advantage of the multiple radio transmissions between mobile users and/or with respect to serving base stations. These algorithms will have to guarantee good spatial resolution, while being adapted to the specific features of massively distributed and scalable networks. Another objective will be to reduce the impact of these new functions on the underlying communication service, by means of optimized resource allocation (power, time, frequency, etc.) and signalling strategies. Finally, new communication schemes based on the acquired location and sensing information will be investigated (e.g. dynamic and proactive association mechanisms, jointly exploiting the predicted positions of users and moving obstacles). Among the various tools and methods envisaged for solving the above multi-objective optimisation problems, machine learning-based approaches will be taken into consideration.

These algorithmic proposals will be validated through both realistic synthetic simulations and experimental data. The latter will be collected in the frame of dedicated field measurement campaigns, conducted by another lab at CEA-Leti with unique hardware capabilities (including a wideband multi-point radio channel sounder, as well as several prototypes of reconfigurable intelligent surfaces, both developed at CEA-Leti).

This PhD will be conducted in a stimulating, international, and multi-disciplinary working environment, at the crossroads between academic and industrial R&D communities, while combining exploratory research and more applied developments. Finally, while working in the frame of a collaborative European research project, the candidate will also benefit from technical inputs and scientific interactions with numerous research teams, inside and outside CEA.

The expected outcomes of this research may contribute to the specification of future communication networks, paving the way for tighter interactions with the physical environment, as well as for frugality in terms of global resources consumption.

To know more:
- https://www.leti-cea.fr/cea-tech/leti/Pages/recherche-appliquee/solutions-technologiques/communication-sans-fil-reseaux.aspx
- https://www.linkedin.com/in/benoit-denis-cea/

Multi-purpose OTA testing for communication and sensing applications

The PhD thesis here proposed is in the field of channel propagation modeling for wireless communication and sensing systems.

Over-the-air (OTA) radiated testing is conducted without the need for a radio frequency (RF) cable connection to the Device Under Test (DUT), ensuring that the DUT remains intact and unaltered during testing."
Efficient beamforming and management are crucial for stable links in FR1-FR2 in 6G Networks. Current FR2 tests are static due to emulation complexities. Dynamic testing raises repeatability questions, and different metrics are needed for varying channels and multi-user scenarios including CF-mMIMO. FR2's larger test zones require 3D arrays for spatial channel validation. More sampling locations lead to longer tests. Near-field challenges arise due to test zone size and compact setups, requiring suitable validation methods. Multi-probe Setups for FR1 and simplified setups for FR2, aimed at NR UE testing, fall short for large devices due to size and cost constraints. Balancing system complexity while maintaining realistic fading channels is key. Base Station testing could also be explored in the future, given current lack of standards.
Joint Sensing and Communication (JSAC) and radar-like technology also demand for OTA testing reproducing the scattering scene as well as the target signature.

This thesis aims to explore and present a versatile OTA configuration designed for testing communication and radar systems. The theoretical analysis will focus on establishing optimal arrangements of multiple probes based on frequency allocation, DUT dimensions, and channel attributes such as angle of arrival and polarization spread. Consequently, the transformation from near-field to far-field will be addressed. In the context of radar and sensing, the 0OTA setup will endeavor to simulate scattering scenes and distinct target signatures. This will be achieved by reversing a near-field physical optic model to determine probe positioning and excitation. The emulation of scattering using OTA will be initially explored in free space propagation then extended to scenarios involving multi-path propagation and targets.
The final objective is to define the probe array configuration and associated processing associated for a Proof of Concept in CEA OTA anechoic chamber (http://www.leti-cea.fr/cea-tech/leti/english/Pages/Applied-Research/Facilities/telecommunications-platform.aspx).

The PhD student will be part of the Antenna, Propagation and Inductive Coupling Laboratory at CEA-LETI, in Grenoble (France). He/she will benefit of the state of the art facilities (channel sounders, emulator, OTA seutp, and electromagnetic simulator).

The position is open to outstanding students with Master of Science, “école d’ingénieur” or equivalent. The student should have specialization in the field of telecommunications, microwave and/or signal processing. The application must necessarily include a CV, cover letter and grades for the last two years of study.

Faster-Than-Nyquist transceiver: application to physical layer security

Transmission security is a major concern in an increasingly connected world, where electronic devices play a central role in our daily lives. Rapid technological advances have led to a growing dependence on connected objects, from smartphones to medical devices to autonomous vehicles. This issue is also reflected in global geopolitics, with various attempts to intimidate or even intercept strategic communications. This digital omnipresence raises crucial questions about the security of transmissions, which are often vulnerable to a variety of threats.

In this research project, we propose to focus on securing the physical layer of communications systems, in addition to cryptography-based security. Our aim is to protect the integrity of a message against interception, as well as its stealth character, i.e. the ability of a third party not to detect transmissions between a transmitter and several receivers.

The research work will focus on the concept of "Faster-than-Nyquist". This technique refers to an approach to data transmission that violates the Nyquist rule in terms of sampling frequency. The Nyquist rule stipulates that, to avoid loss of information when transmitting signals, the sampling frequency must be at least twice the maximum signal frequency. In the context of "Faster-than-Nyquist", the idea is to explore transmission methods that exceed this theoretical limit for the purpose of transmission security. Indeed, by exceeding the conventional sampling frequency, there is an increase in interference and in the level of transmission errors. The understanding, mastery and appropriate use of this technique will be at the heart of this research work.

Based on the laboratory's expertise in digital, IoT, satellite, 5G and 6G communications, the PhD student will be supported in his or her research by experts in the field. Advanced digital signal processing and rapid prototyping tools will be used to experimentally validate theoretical concepts. The research work will integrate (i) bibliographical studies (ii) understanding and proposing new transmission schemes (iii) validation by numerical simulations and/or demonstrators (iv) dissemination work including, filing patents, writing and presenting work in international journals and conferences.

Why join us?
- Experience at the cutting edge of innovation, with strong development potential
- A position in the heart of the Grenoble metropolitan area Capitals of the French Alps), easily accessible via the soft mobility encouraged by the CEA,
- A recognized work-life balance, (28 + 24 (RTT) paid leave, remote working possible (2 days/week)
- A salary of 2406€/year for 3 years.
- An active work council in terms of leisure and extra-professional activities, on-site catering.

About us: http://www.leti-cea.com/cea-tech/leti/english/Pages/Applied-Research/Technology-Fields/wireless-communication-networks.aspx

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