Luc Martens

Ghent University | UGhent · Department of Information Technology

Physical inactivity is a public health issue. Mobile health interventions to promote physical activity often still experience dropout, resulting in people not adhering to the interventions. This paper aims to further improve mobile health apps with innovatively applied techniques from recommender system algorithms to increase personalization for ph...

With the ever-growing amount of news, there is an increasing need for tools capable of filtering out and tailoring the content to the wants and needs of the reader. Over the last decade, researchers have noted that the inclusion of objectives such as diversity, novelty, and serendipity plays a vital role in further improving recommender systems’ pe...

In this presented study, we measured in situ the uplink duty cycles of a smartphone for 5G NR and 4G LTE for a total of six use cases covering voice, video, and data applications. The duty cycles were assessed at ten positions near a 4G and 5G base-station site in Belgium. For Twitch, VoLTE, and WhatsApp, the duty cycles ranged between 4% and 22% i...

Background To seek appropriate veterinary attention for horses with colic, owners must recognise early signs. Direct observation of horse behaviour has several drawbacks: it is time‐consuming, hard to see subtle and common behavioural signs, and is based on intuition and subjective decisions. Due to recent advances in wearables and artificial intel...

New frequency bands, such as the mmWave at 28 GHz for fifth Generation networks in Frequency Range 2, are being introduced to accomplish the required throughput for new services such as remote surveillance, object tracking, and factory automation. These high-frequency bands are sensible to reflections and diffraction. Therefore, accurate path loss...

Objective: Acousto-electrophysiological neuroimaging (AENI) is a technique hypothesized to record electrophysiological activity of the brain with millimeter spatial and sub-millisecond temporal resolution. This improvement is obtained by tagging areas with focused ultrasound (fUS). Due to mechanical vibration with respect to the measuring electrod...

UWB ranging algorithms using thresholding require careful settings that account for multipath richness. Max-peak ratio thresholds are incapable of detecting attenuated first-path components (FPCs) or risk triggering on noise. A noise-based threshold is more reliable and robust, but setting this threshold transforms the problem into distinguishing n...

p>Most spectrum surveys conducted worldwide demonstrate that the radio-electric spectrum in use at any given location and instant of time is below 25%. Current spectrum management policies and spectrum utilization inefficiency are becoming unsustainable for the future development of radio technologies and services. In this context, dynamic spectrum...

p>Most spectrum surveys conducted worldwide demonstrate that the radio-electric spectrum in use at any given location and instant of time is below 25%. Current spectrum management policies and spectrum utilization inefficiency are becoming unsustainable for the future development of radio technologies and services. In this context, dynamic spectrum...

This study investigates wireless power transfer for deep in-body receivers, determining the optimal frequency, power budget, and design for the transmitter and receiver. In particular, the focus is on small, in-body receivers at large depths up to 20 cm for obese patients. This enables long-term monitoring of the gastrointestinal tract for all body...

Recommender systems are commonly-used tools to assist people in making decisions. However, most research has focused on the domain of recommendations for audio-visual content and e-commerce, whereas the specific characteristics of recommendations for recipes and cooking did not receive enough attention. Since meals are often consumed in group (with...

This article presents a comparative numerical study of collocated and distributed massive multiple-input–multiple-output (MIMO) deployments at 3.5 GHz in an industrial indoor environment from the point of view of downlink human electromagnetic field (EMF) exposure. A collection of environmental models incorporating elements with stochastic geometry...

In this paper, we aim to improve existing health recommender systems by defining relevant contextual and motivational variables to recommend physical activities and collect appreciation feedback. Current health recommenders do not sufficiently include users’ context and motivational theory when personalizing health suggestions. To bridge these gaps...

Acousto-electrophysiological neuroimaging is a technique hypothesized to record electrophysiological activity of the brain with millimeter spatial and sub-millisecond temporal resolution. This improvement is obtained by tagging areas with focused ultrasound (fUS). Due to mechanical vibration with respect to the measuring electrodes, the electrical...

Spectrum surveys performed worldwide demonstrate that the spectrum utilization efficiency is less than 0.25. Therefore, the traditional long-term licensed spectrum allocation by regulators is not sustainable. Although dynamic spectrum access networks allow increasing the efficiency of spectrum utilization, coexistence is still a major problem. In t...

Electronic boluses with biotelemetry capabilities enable wireless monitoring of animals’ physiological data (e.g., temperature, pH). The aim of this study was to design and experimentally validate a novel multiband (434, 868, 1400) MHz conformal patch antenna for in-body biotelemetry applications for cows. The optimal frequency band was studied pri...

Most spectrum surveys conducted worldwide demonstrate that the radio-electric spectrum in use at any given location and instant of time is below 25%. Current spectrum management policies and spectrum utilization inefficiency is becoming unsustainable for the future development of radio technologies and services. In this context, dynamic spectrum ac...

Of particular interest within fifth generation (5G) cellular networks are the typical levels of radiofrequency (RF) electromagnetic fields (EMFs) emitted by ‘small cells’, low-power base stations, which are installed such that both workers and members of the general public can come in close proximity with them. In this study, RF-EMF measurements we...

Cattle behaviour is fundamentally linked to the cows’ health, (re)production, and welfare. The aim of this study was to present an efficient method to incorporate Ultra-Wideband (UWB) indoor location and accelerometer data for improved cattle behaviour monitoring systems. In total, 30 dairy cows were fitted with UWB Pozyx wearable tracking tags (Po...

Fixed wireless access (FWA) provides a solution to compete with fiber deployment while offering reduced costs by using the mmWave bands, including the unlicensed 60 GHz one. This paper evaluates the deployment of FWA networks in the 60 GHz band in realistic urban and rural environment in Belgium. We developed a network planning tool that includes n...

Despite a lot of research about predictive maintenance for onshore and offshore windmill farms, nearly no investigation has been performed to obtain the optimal sequence in which windmills are to be served in a predefined time frame. The higher fuel costs and the increasing time pressure on maintenance jobs urge the need for optimisation, so offsho...

This paper proposes a genetic algorithm (GA) combined with ray tracer to generate a cell-free topology of massive MIMO (mMIMO) for the optimal focusing performance serving multiple users. The realistic hardware impairment, for instance the non-ideal power amplifier, is taken into account of the system modeling and topology optimization. To the best...

The world population is aging and more and more people suffer from dementia, which makes remembering and orientation in time and space difficult. Moreover dementia has a strong negative effect on the quality of living of the people suffering from it, but also of their relatives. In this paper, we investigate if and how the playback of carefully cho...

This paper describes the exploration of the combined antenna–channel model for a horse hoof. An antenna of 25 mm × 40 mm is designed in the ISM 868 MHz band. During the characterization and design of the antenna, the dynamic and harsh environment of the horse hoof is taken into account throughout every step of the procedure because it is impossible...

Today, our society mainly relies on the energy generated by burning fossil fuels, which provides a reliable supply at an affordable price. However, this energy is not renewable and will eventually be depleted in the future. To address sustainability issues, we need to take action in all layers of our society, including our wireless access networks,...

The constant increase in the required user capacity and the evolution of wireless network technologies impact the exposure that users experience from wireless networks. This paper evaluates various 5G network topologies regarding human exposure, mobile communication quality, and sustainability. We assess human exposure, based on a novel Exposure Ra...

Temporal interference (TI) stimulation is a technique in which two high frequency sinusoidal electric fields, oscillating at a slightly different frequency are sent into the brain. The goal is to achieve stimulation at the place where both fields interfere. This study uses a simplified version of the Hodgkin - Huxley model to analyse the different...

New measurement methods and equipment for correct 5G New Radio (NR) electromagnetic field (EMF) in-situ exposure assessment of instantaneous time-averaged exposure (Eavg) and maximum extrapolated field exposure (Emax) are proposed. The different options are investigated with in-situ measurements around 5G NR base stations (FR1) in different countri...

Radio frequency identification (RFID) localization technology has attracted great attention in stocktaking in warehouses. In this paper, we investigate drone-based RFID localization for fast and accurate inventory management. Considering the drone trajectory errors, we propose a robust RFID lateral localization method based on the unwrapped phase,...

Accurate wireless network planning is crucial for the deployment of new wireless services. This usually requires the consecutive evaluation of many candidate solutions, which is only feasible for simple path loss models, such as one-slope models or multi-wall models. However, such path loss models are quite straightforward and often do not deliver...

Due to its high delay resolution, the ultra-wideband (UWB) technique has been widely adopted for fine-grained indoor localization. Instead of active positioning, UWB radar-based passive human tracking is explored using commercial off-the-shelf (COTS) devices. To extract the time-of-flight (ToF) reflected by the moving person, the accumulated channe...

Sound pollution is an ever growing problem in modern society, and especially in urban environments. In this paper, we investigate if and how artificial sounds can improve the experience of visitors of an urban park with a lot of traffic noise. By using a mobile app, park visitors can control the sound playback by selecting the natural sounds they l...

Human Activity Recognition (HAR) has attracted extensive attention in the past decade due to its potential application in areas such as elderly care, smart homes, virtual reality, etc. Especially, device-free (a.k.a., passive or contact-less) human positioning and sensing become an active area of research due to no user-attached sensor needed. Duri...

Ultra-wideband (UWB) attracts extensive attention for the Internet-of-Things applications, especially the fine-grained location-based services. Rather than active tracking, this paper explores the UWB-based device-free pedestrian tracking problem. Concerning the challenges of fine-grained passive tracking for the low-cost commodity UWB devices, we...

In an increasingly wireless world, spatiotemporal monitoring of the exposure to environmental radiofrequency (RF) electromagnetic fields (EMF) is crucial to appease public uncertainty and anxiety about RF-EMF. However, although the advent of smart city infrastructures allows for dense networks of distributed sensors, the costs of accurate RF sensor...

Objective In temporal interference (TI) deep brain stimulation (DBS), the neurons of mice react to two interfering sinusoids with a slightly different frequency. This is called a temporal interference (TI) signal. It was previously seen that for the same input intensity, the neurons do not react to a purely sinusoidal signal. This study aims to get...

Recommender systems have been investigated for many years, with the aim of generating the most accurate recommendations possible. However, available data about new users is often insufficient, leading to inaccurate recommendations; an issue that is known as the cold-start problem. A solution can be active learning. Active learning strategies proact...

Future wireless communication networks can benefit from Unmanned Aerial Base Stations (UABSs) to provide enhanced capacity to ground users (GU) in large and remote locations. Connecting UABSs to the terrestrial network presents several challenges, such as the limited gain traditional antennas need to maintain suitable wireless links between the cor...

Realistic human downlink exposure at 3.5 and 28 GHz to electromagnetic fields is evaluated for distributed and collocated base stations using a hybrid ray-tracing/finite-difference time-domain method. For the first time, the absorbed power density is computed for distributed massive multiple-input multiple-output (DMaMIMO) 6G base stations at 28 GH...

A framework is proposed for long-term vehicular channel simulation based on the vector time-frequency autoregressive (VTFAR) model for a sparse parametric description of nonstationary multivariate random processes. Based on vehicle-to-infrastructure tunnel measurements, we estimate the VTFAR model parameters and validate the model by comparing the...

Objective. To investigate computationally the interaction of combined electrical and ultrasonic modulation of isolated neurons and of the Parkinsonian cortex-basal ganglia-thalamus loop. Approach. Continuous-wave or pulsed electrical and ultrasonic neuromodulation is applied to isolated Otsuka plateau-potential generating subthalamic nucleus (STN)...

Equine training activity detection will help to track and enhance the performance and fitness level of riders and their horses. Currently, the equestrian world is eager for a simple solution that goes beyond detecting basic gaits, yet current technologies fall short on the level of user friendliness and detection of main horse training activities....

Due to its high delay resolution, the ultra-wideband (UWB) technique has been widely adopted for fine-grained indoor localization. Instead of active positioning, UWB radar-based passive human tracking is explored using commercial off-the-shelf (COTS) devices. To extract the time-of-flight (ToF) reflected by the moving person, the accumulated channe...

Despite the recent advances in broadband penetration and accessibility, broadcasting networks continue to be the most efficient way for delivering media content to large areas independently of the user density. Nevertheless, a convergence of broadcasting services into the broadband networks is foreseen. In this context, Layered Division Multiplexin...

LTE-eMBMS systems efficiently deliver multicast/broadcast services using Layered Division Multiplexing (LDM) technology. In a two-layer LDM system, Layer 1, with higher power allocation delivers mobile services, and Layer 2 in a Single Frequency Network scheme provides local content. The challenge is to reduce the gap in the layers' coverage areas...

Among the potential road maps to sustainable production, efficient manufacturing scheduling is a promising direction. This paper addresses the lack of knowledge in the scheduling theory by introducing a generalized flexible flow shop model with unrelated parallel machines in each stage. A mixed-integer programming formulation is proposed for such m...

We present a smartphone-based indoor localisation system, able to track pedestrians over multiple floors. The system uses Pedestrian Dead Reckoning (PDR), which exploits data from the smartphone’s inertial measurement unit to estimate the trajectory. The PDR output is matched to a scaled floor plan and fused with model-based WiFi received signal st...

A novel Machine Learning (ML) method based on Neural Networks (NN) is proposed to assess radio‐frequency (RF) exposure generated by WiFi sources in indoor scenarios. The aim was to build an NN capable of addressing the complexity and variability of real‐life exposure setups, including the effects of not only down‐link transmission access points (AP...