| 1. |
- Grabowski, Alexander, 1993
(author)
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VCSEL Equivalent Circuits and Silicon Photonics Integration
- 2022
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Doctoral thesis (other academic/artistic)abstract
- The vertical-cavity surface-emitting laser (VCSEL) is a light source of great importance for numerous industrial and consumer products. The main application areas are datacom and sensing. The datacom industry uses GaAs-based VCSELs for optical interconnects, the short-reach fiber optical communication links used to transfer large amounts of data at high rates between units within data centers and supercomputers. In the area of sensing, VCSELs are largely used in consumer products such as smart phones (e.g. face ID and camera auto focus), computer mice, and automobiles (e.g. gesture recognition and LIDAR for autonomous driving). In this work, an advanced physics-based equivalent circuit model for datacom VCSELs has been developed. The model lends itself to co-design and co-optimization with driver and receiver ICs, thereby enabling higher data rate transceivers with bandwidth limited VCSELs and photodiodes. The model also facilitates an understanding of how each physical process within the VCSEL affects the VCSEL static and dynamic performance. It has been applied to study the impact of carrier transport and capture on VCSEL dynamics. The work also includes micro-transfer-printing of GaAs-based single-mode VCSELs on silicon nitride photonic integrated circuits (PICs). Such PICs are increasingly used for e.g. compact and highly functional bio-photonic sensors. Transfer printing of VCSELs enables the much-needed on-PIC integration of power efficient light sources. The bottom-emitting VCSELs are printed above grating couplers on the PIC and optical feedback is used to control the polarization for efficient coupling to the silicon nitride waveguide. Wavelength tuning, as required by the bio-sensing application, is achieved by direct current modulation.
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| 2. |
- Gaspar Sánchez, José Manuel, et al.
(author)
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Edge computing for cyber-physical systems : A Systematic Mapping Study Emphasizing Trustworthiness
- 2022
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In: ACM Transactions on Cyber-Physical Systems. - : Association for Computing Machinery (ACM). - 2378-962X .- 2378-9638. ; 6:3, s. 1-28
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Journal article (peer-reviewed)abstract
- Edge computing is projected to have profound implications in the coming decades, proposed to provide solutions for applications such as augmented reality, predictive functionalities, and collaborative Cyber-Physical Systems (CPS). For such applications, edge computing addresses the new computational needs, as well as privacy, availability, and real-time constraints, by providing local high-performance computing capabilities to deal with the limitations and constraints of cloud and embedded systems. Edge computing is today driven by strong market forces stemming from IT/cloud, telecom, and networking - with corresponding multiple interpretations of ”edge computing” (e.g. device edge, network edge, distributed cloud, etc.). Considering the strong drivers for edge-computing and the relative novelty of the field, it becomes important to understand the specific requirements and characteristics of edge-based CPS, and to ensure that research is guided adequately, e.g. avoiding specific gaps.Our interests lie in the applications of edge computing as part of CPS, where several properties (or attributes) of trustworthiness, including safety, security, and predictability/availability are of particular concern, each facing challenges for the introduction of edge-based CPS. We present the results of a systematic mapping study, a kind of systematic literature survey, investigating the use of edge computing for CPS with a special emphasis on trustworthiness. The main contributions of this study are a detailed description of the current research efforts in edge-based CPS and the identification and discussion of trends and research gaps. The results show that the main body of research in edge-based CPS only to a very limited extent consider key attributes of system trustworthiness, despite many efforts referring to critical CPS and applications like intelligent transportation. More research and industrial efforts will be needed on aspects of trustworthiness of future edge-based CPS including their experimental evaluation. Such research needs to consider the multiple interrelated attributes of trustworthiness including safety, security, and predictability, and new methodologies and architectures to address them. It is further important to provide bridges and collaboration between edge computing and CPS disciplines.
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| 3. |
- Ranisch, Robert, et al.
(author)
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Ethics of digital contact tracing apps for the Covid-19 pandemic response
- 2020
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Reports (other academic/artistic)abstract
- There is a growing interest in contact tracing apps (CT apps) for pandemic man- agement. These apps raise significant moral concerns. It is therefore crucial to consider ethical requirements before and while implementing such apps. Public trust is of major importance for population uptake of contact tracing apps. Hasty, ill-prepared or badly communicated implementations of CT apps will likely under- mine public trust, and as such, risk impeding general effectiveness. In response to these demands, to meet ethical requirements and find a basis for justified trust, this background introduces an ethical framework for a responsible design and implementation of CT apps. However, even prudently chosen measures of digital contact tracing carry moral costs, which makes it necessary address different trade-offs. This background paper aims to inform developers, researchers and decision-makers be- fore and throughout the process of implementing contact tracing apps.
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| 4. |
- Mao, Yadong, et al.
(author)
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Decentralized Training of 3D Lane Detection with Automatic Labeling Using HD Maps
- 2023
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In: IEEE Vehicular Technology Conference. - 1550-2252. ; 2023-June
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Conference paper (peer-reviewed)abstract
- To have competent 3D lane detection for real-world driving, a massive amount of data from all over the world is needed, but data collection and manual annotation are costly and time-consuming. The diversity of data collected by developmental cars might still be limited compared to the data collected by a large fleet of customer cars. Federated learning enables training models on edge without transferring data out of devices. However, training supervised learning tasks at the edge is directly tied to having access to high-quality labels, which is limited at the edge. In this paper, we propose a fully automatic method to generate 3D lane labels at the edge using a pre-recorded HD map to enable the federated training of the 3D lane detection model. As a reference, a semi-automatic method is applied for creating a 3D-lane dataset used as ground truth. Our experimental results show that the model can achieve comparable performance when training on the same dataset in both a centralized and a decentralized manner. And the models trained on semi-automatic labeled datasets slightly outperform those trained on fully-automatically labeled datasets. This study shows that a well-performing 3D lane detection model can be trained in a supervised and fully decentralized manner, and most importantly, data privacy at the edge is guaranteed.
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| 5. |
- Panigrahi, Smruti Ranjan, 1983-, et al.
(author)
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A Study of Delay and Doppler Spreads at 24 GHz ISM band
- 2020
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In: 2020 16th International Conference on Wireless and Mobile Computing, Networking and Communications (WiMob). - : Institute of Electrical and Electronics Engineers (IEEE). - 9781728197227 ; , s. 1-6
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Conference paper (peer-reviewed)abstract
- This article investigates the wide-band channel characteristics at 24 GHz ISM band in a mobile radio environment. The mobility in the test environment is achieved by attaching the transmit antenna to a KUKA robot's arm. The radio measurements were carried out inside the robotics lab at the University of Gävle, Sweden. The radio channel measurements were carried out at various situations, e.g., line of sight (LOS), non-line of sight (NLOS), regular lab environment, reflective environment, and different velocities of the robot's arm. The influence of these situations on the power delay profile, Doppler spectral density, root mean square (RMS) delay spread, RMS Doppler spread, coherence bandwidth and coherence time, has been studied.
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| 6. |
- Bao, Husileng, 1991, et al.
(author)
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Wideband mm-wave Spectrum-Efficient Transmitter Using Low-Pass Sigma–Delta-Over-Fiber Architecture
- 2023
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In: IEEE Microwave and Wireless Technology Letters. - 2771-9588 .- 2771-957X. ; 33:10, s. 1505-1508
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Journal article (peer-reviewed)abstract
- The millimeter-wave band offers large bandwidth and promises high data rates for wireless communication systems. This work proposes a millimeter-wave radio-over-fiber architecture suitable for wideband mm-wave communication, using a lowpass sigma-delta modulation approach. The central unit generates baseband sigma-delta bitstreams, in-phase/quadrature (I/Q) components, which are transported to a remote radio head (RRH) using a standard QSFP28 optical interconnect link connection. In the RRH, the baseband I/Q signals are upconverted to the millimeter-wave band, amplified, and transmitted through an antenna. The performance of the resulting sigma-delta-over-fiber transmitter architecture is experimentally verified at 28 GHz, demonstrating a state-of-the-art symbol rate up to 1.5 Gsym/s. Furthermore, in over-the-air measurements, the architecture is shown to support 1 Gsym/s with 5.9% error vector magnitude for 64/256/1024 quadrature amplitude modulation cases over a 5 m wireless distance. The results demonstrate the feasibility of the proposed architecture for the realization of wideband millimeterwave distributed antenna systems.
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| 7. |
- Bencheikh Lehocine, Chouaib, 1993, et al.
(author)
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Robust Analog Beamforming for Periodic Broadcast V2V Communication
- 2022
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In: IEEE Transactions on Intelligent Transportation Systems. - 1524-9050 .- 1558-0016. ; 23:10, s. 18404-18422
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Journal article (peer-reviewed)abstract
- We generalize an existing low-cost analog signal processing concept that takes advantage of the periodicity of vehicle-to-vehicle broadcast service to the transmitter side. In particular, we propose to process multiple antennas using either an analog beamforming network (ABN) of phase shifters, or an antenna switching network (ASN) that periodically alternates between the available antennas, to transmit periodic messages to receivers that have an analog combining network (ACN) of phase shifters, which has been proposed in earlier work. To guarantee robustness, we aim to minimize the burst error probability for the worst receiving vehicular user, in a scenario of bad propagation condition that is modeled by a single dominant path between the communicating vehicles. In absence of any form of channel knowledge, we analytically derive the optimal parameters of both ABN and ASN. The ABN beamforming vector is found to be optimal for all users and not only for the worst receiving user. Further, we demonstrate that Alamouti scheme for the special case of two transmit antennas yields similar performance to ABN and ASN. At last, we show that the derived parameters of the two proposed transmission strategies are also optimal when hybrid ACN-maximal ratio combining is used at the receiver.
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| 8. |
- Kang, Jeongwan, et al.
(author)
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Optimized Switching Between Sensing and Communication for mmWave MU-MISO Systems
- 2022
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In: 2022 Ieee International Conference On Communications Workshops (Icc Workshops). - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. 498-503
-
Conference paper (peer-reviewed)abstract
- In this paper, we propose a scheme optimizing the per-user channel sensing duration in millimeter-wave (mmWave) multi-user multiple-input single-output (MU-MISO) systems. For each user, the BS predicts the effective rate to be achieved after pilot transmission. Then, the channel sensing duration of each user is optimized by ending the pilot transmission when the predicted rate is lower than the current rate. The robust regularized zero-forcing (RRZF) precoder and equal power allocation (EPA) are adopted to transmit sensing pilots and data. Numerical results show that the more severe the interference among users, the longer channel sensing duration is required. Moreover, the proposed scheme results in a higher sum rate compared to benchmark schemes.
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| 9. |
- Kylin, Carl, 1996
(author)
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Over the air calibration of transmitter distortion for active antenna arrays
- 2024
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Licentiate thesis (other academic/artistic)abstract
- Radar systems for air surveillance have long utilised large antenna arrays to generate high enough gain for a narrow enough transmitted beam. In most modern systems this is accomplished through the use of large active electronically steered antenna arrays. Calibrating a large active antenna array is a challenging endeavour. Distorting effects stemming from the amplifying circuitry can have a non-negligible effect on the transmitted signal, and the effects can vary across the array. In modern and future transmitter arrays, individually controlled antenna elements will be a feature. With such systems, distortion that varies over an array can be combatted. One challenge is how to collect data about what signal is being transmitted and in what way the actual signal differs from the desired transmitted signal. The work presented in this thesis studies aspects of characterising a model describing the distortion generated in an active antenna array using an over the air channel. Specifically, the first included article presents a method where signals collected using an over the air channel generated by targets of opportunity are used to estimate the parameters of a non-linearly parametrised model for a radar transmitter. In this article, the radar is assumed to transmit different signals on each antenna element. The second included article studies conditions for identifiability for the setup in the first article as well as for other similar setups. These works constitute the second part of this thesis. To put this work into context, the first part of this thesis presents an overview of the problems caused by distortion in a radar system. This is investigated under different modelling assumptions and for radars operating in a number of different modes.
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| 10. |
- Liu, Edward, et al.
(author)
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A 25-40 GHz Three-Way Power Amplifier with No Load Modulation Achieving Broadband Deep Power Back-Off Efficiency Enhancement
- 2024
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In: IEEE Radio Frequency Integrated Circuits Symposium (RFIC), 2024.
-
Conference paper (peer-reviewed)abstract
- This paper presents a millimeter-wave (mm-Wave) power amplifier (PA) topology that avoids the trade-off between bandwidth and load modulation. The proposed topology uses three PA paths and can achieve efficiency enhancement at power back-off without load modulation. With a 100 MHz 5G NR FR2 1-CC 64-QAM signal, this PA achieves average power and PAE of 6.45 - 12.61 dBm and 5.9 - 16.4% from 25 - 40 GHz, respectively. With a 200 MHz signal, average power and PAE are 5.58 - 11.1 dBm and 4.8 - 13.3%, respectively.
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