PhD defence: Low-Complexity Multiband and Beam-Reconfigurable Antennas for Beyond 5G Communications

Publicerad: 2023-03-14

Thesis title: Low-Complexity Multiband and Beam-Reconfigurable Antennas for Beyond 5G Communications

Author: Qiuyan Liang, Department of Electrical and Information Technology, Lund university

Faculty opponent:  Professor Sean Victor Hum - Canada.

Location: E:1406 E-huset, Ole Römers väg 3, LTH, Lund University, Lund.

Streamed at: https://lu-se.zoom.us/s/64926871940

Thesis at LU Research Portal

Abstract

Antennas with large frequency bandwidth, high gain, and beam steering capability are very importance for future wireless communication systems. However, it is very challenging to design antennas with low-complexity structures and high space utilization that can achieve these desired features. Base stations with fixed installations and non-stationary mobile terminals play critical roles in wireless communication networks. The research in this thesis focuses on the low-complexity multiband and beam-reconfigurable antenna design for the two applications.

The first topic of this thesis is about partially reflective surfaces (PRS) antennas, which have significant potential for application in future base stations. In the first part (Part I) of this thesis, existing PRS antennas and challenges to be addressed in PRS antenna design are introduced with respect to beam steering capability and shared-aperture antenna design. To give a clearer insight into the working principle of PRS antenna as well as several observed phenomena involving PRS, the existing theory for PRS antenna is extended. Ray-tracing models as well as the theory of PRS unit cells are utilized to explain the operation of PRS antennas that generate broadside and/or deflected beams. Using these tools, two practical PRS antennas are designed for beam reconfigurability and shared-aperture implementation, respectively. In the first work, we compare the beam deflection capability of different types of PRSs using ray-tracing analysis, with the aim of providing a guideline for selecting a suitable PRS type that would yield a larger beam steering range. In addition, the role of a feeding source in enhancing beam deflection of PRS is explained using ray-tracing analysis, and a beam-reconfigurable feeding source with low-complexity structure is presented. In the second work, we derive the frequency ratio gap for traditional dual-band shared-aperture Fabry-Pérot cavity (DS-FPC) antennas with single-layer PRS and subsequently present a shared-aperture antenna design method with flexible frequency ratio to fill the gap.

The second topic of this thesis is on the co-design of mobile terminal antennas that can cover a wide range of frequency bands. Such antennas are of significant current interest due to the current trend of utilizing higher frequency spectra in wireless communication. A co-designed millimeter-wave (mm-wave) and sub-6GHz antenna system is conceived, where the mm-wave antennas that offer reconfigurable beams for beam steering are integrated into the capacitive coupling elements (CCEs) of the sub-6GHz antenna. Such an implementation aims to achieve a compact and low-complexity antenna structure. In addition, several techniques have been investigated by simulation to achieve further performance improvements in the proposed antenna system with respect to mm-wave antenna gain and bandwidth as well as sub-6GHz antenna tunability and bandwidth.

PhD defence: Efficient Security Protocols for Constrained Devices

Publicerad: 2023-03-14

Thesis title: Efficient Security Protocols for Constrained Devices

Author: Martin Gunnarsson, Department of Electrical and Information Technology, Lund university

Faculty opponent:  Professor Jerker Delsing - Luleå University of Technology.

Location: E:1406 E-huset, Ole Römers väg 3, LTH, Lund University, Lund.

Streamed at: https://lu-se.zoom.us/s/69278738433

Thesis at LU Research Portal

Abstract

During the last decades, more and more devices have been connected to the Internet. Today, there are more devices connected to the Internet than humans. An increasingly more common type of devices are cyber-physical devices. A device that interacts with its environment is called a cyber-physical device. Sensors that measure their environment and actuators that alter the physical environment are both cyber-physical devices.

Devices connected to the Internet risk being compromised by threat actors such as hackers. Cyber-physical devices  have become a preferred target for threat actors since the consequence of an intrusion disrupting or destroying a cyber-physical system can be severe. Cyber attacks against power and energy infrastructure have caused significant disruptions in recent years.

Many cyber-physical devices are categorized as constrained devices. A constrained device is characterized by one or more of the following limitations: limited memory, a less powerful CPU, or a limited communication interface. Many constrained devices are also powered by a battery or energy harvesting, which limits the available energy budget. Devices must be efficient to make the most of the limited resources.

Mitigating cyber attacks is a complex task, requiring technical and organizational measures. Constrained cyber-physical devices require efficient security mechanisms to avoid overloading the systems limited resources. In this thesis, we present research on efficient security protocols for constrained cyber-physical devices.

We have implemented and evaluated two state-of-the-art protocols, OSCORE and Group OSCORE. These protocols allow end-to-end protection of CoAP messages in the presence of untrusted proxies.

Next, we have performed a formal protocol verification of WirelessHART, a protocol for communications in an industrial control systems setting. In our work, we present a novel attack against the protocol.

We have developed a novel architecture for industrial control systems utilizing the Digital Twin concept. Using a state synchronization protocol, we propagate state changes between the digital and physical twins. The Digital Twin can then monitor and manage devices.

We have also designed a protocol for secure ownership transfer of constrained wireless devices. Our protocol allows the owner of a wireless sensor network to transfer control of the devices to a new owner. With a formal protocol verification, we can guarantee the security of both the old and new owners.

Lastly, we have developed an efficient Private Stream Aggregation (PSA) protocol. PSA allows devices to send encrypted measurements to an aggregator. The aggregator can combine the encrypted measurements and calculate the decrypted sum of the measurements. No party will learn the measurement except the device that generated it.

Cake seminar by Jakob Nordström: The Computational Challenge of Combinations

Publicerad: 2023-01-23

The Computational Challenge of Combinations

Prof. Jakob Nordström, Dept of Computer Science, Lund University

Abstract:

Combinatorial solving deals with problems that are solved by combining objects, but where these objects cannot be subdivided to make it easier to find solutions. To see what this means, note that in a power grid we can fine-tune voltages and currents to get the right power distribution, but if we want to distribute packages between delivery trucks, there is no way we can fine-tune the load balance by assigning 90% of a package to one truck and the remaining 10% to another. This fact makes combinatorial problems computationally very challenging. In this talk, I will discuss three aspects of my research on combinatorial problems:

1. Are we lacking good general-purpose algorithms for combinatorial problems because we just haven't been smart enough, or can one prove mathematically that these problems are somehow inherently hard to solve for computers?
2. For the type of combinatorial problems that can be solved in practice, can we leverage more sophisticated mathematical tools to get even better performance?
3. For problems with life-or-death consequences, is there any way we can guarantee that what the computer outputs is in fact a correct solution?

Design for security, privacy, and trust I - ELLIIT tech talk 7

Publicerad: 2023-01-09

AI-enabled digitalization of both good and evil intentions challenges how we handle justice, integrity, security, transparency and the division of responsibilities. We give examples of problems and explain principles for how they can be tackled - but also show that we sometimes have to choose what we mean by justice, convenience and security before we move on.

• Christian Gehrmann, professor in computer security
• Elena Pagnin, Assistant professor, Networks and security,
• Ulrika Evertsson, Chief Information Security Officer, LFV
• Johan Wester, Programledare, Host

You can watch this and more ELLIIT tech talks at Youtube.

Introduction to the theme Design for security, privacy, and trust

Participants: Fredrik Tufvesson, Johan Wester

Watch: https://youtu.be/gMjhzIj4064

Why don't the hackers leave our systems alone, and what can we do about it?

Every leap in the history of technology usually leads to consequential problems. Digitalization opens up fantastic opportunities but unfortunately also for the hackers who do not leave our systems alone. Professor Christian Gehrmann explains the paths to a safer digital future where we plan very carefully before creating a new digital service, where we use the latest protection mechanisms and also have a plan for how problems that nevertheless arise will be handled.

Speaker: Christian Gehrmann, professor in computer security

Watch: https://youtu.be/VEnS_NgbeoI

Enhancing Data Authentication

We live in a digital era where almost everybody owns and uses a couple of digital devices. Every time we send some digital information we take for granted that it  will be received precisely as it was sent, but how can we be sure of that? Assistant Professor Elena Pagnin brings us to the world of digital signatures and explains how they can be used to prevent hackers from changing the data we all are sending around.

Speaker: Elena Pagnin, Assistant professor, Networks and security

Watch: https://youtu.be/F7A6mQx5OVc

Conversation about design for security, privacy, and trust

Panelists

• Christian Gehrmann, professor in computer security
• Elena Pagnin, Assistant professor, Networks and security,
• Ulrika Evertsson, Chief Information Security Officer, LFV
• Johan Wester, Programledare, Host

Watch: https://youtu.be/7sx8CSHGl4w

Access

You can watch this and more ELLIIT tech talks at Youtube.

Read about ELLIIT tech talk at elliit.se