The Routing Protocol for Low-power and Lossy Networks (RPL) is a popular routing layer protocol f... more The Routing Protocol for Low-power and Lossy Networks (RPL) is a popular routing layer protocol for multi-hop Wireless Sensor Networks (WSNs). However, typical RPL configurations are based on decade-old assumptions, leading to a mismatch with: (1) advances in wireless hardware; and (2) growing wireless contention. To soften the impact of external stressors (i.e., jamming and interference), we extended RPL to exploit the capabilities of modern multi-interfaced wireless devices. More specifically, our main contribution is the design, development, and evaluation of a novel RPL Objective Function (OF) which, through simulations, is compared to traditional single-interface approaches and a state-of-the-art multi-interface approach. We examine two scenarios, with and without the injection of jamming, respectively. Our proposed OF is shown to outperform, or otherwise perform similar to, all alternatives considered. In normal conditions, it auto-selects the best interface whilst incurring n...
Due to the limited bandwidth of Low-Power Wide-Area Networks (LPWAN), the application layer is cu... more Due to the limited bandwidth of Low-Power Wide-Area Networks (LPWAN), the application layer is currently often tied straight above the link layer, limiting the evolution of sensor networks distributed over a large area. Consequently, the highly efficient Static Context Header Compression (SCHC) standard was introduced, where devices can compress the IPv6 and upper layer protocols down to a single byte. This approach, however, assumes that every compression context is distributed before deployment, again limiting the evolution of such networks. Therefore, this paper presents two context registration mechanisms leveraging on the SCHC adaptation layer. This is done by analyzing current registration solutions in order to find limitations and optimizations with regard to very constrained networks. Both solutions and the current State-of-The-Art (SoTA) are evaluated in a Lightweight Machine to Machine (LwM2M) environment. In such situation, both developed solutions decrease the energy con...
2020 14th European Conference on Antennas and Propagation (EuCAP), 2020
Radio frequency identification (RFID) technology brings tremendous advancement in Internet-of-Thi... more Radio frequency identification (RFID) technology brings tremendous advancement in Internet-of-Things, especially in supply chain and smart inventory management. Phase-based passive ultra high frequency RFID tag localization has attracted great interest, due to its insensitivity to the propagation environment and tagged object properties compared with the signal strength based method. In this paper, a phase-based maximumlikelihood tag positioning estimation is proposed. To mitigate the phase uncertainty, the likelihood function is reconstructed through trigonometric transformation. Weights are constructed to reduce the impact of unexpected interference and to augment the positioning performance. The experiment results show that the proposed algorithms realize fine-grained tag localization, which achieve centimeter-level lateral accuracy, and less than 15-centimeters vertical accuracy along the altitude of the racks.
Proceedings of the 18th International Conference on Information Processing in Sensor Networks, 2019
Indoor Positioning Systems (IPS) using ultra-wideband (UWB) are used in several application domai... more Indoor Positioning Systems (IPS) using ultra-wideband (UWB) are used in several application domains to optimize production processes and save expensive man hour costs. To deploy such a system, most solutions rely on an existing backbone network that is used for communication between the anchors and the Real Time Localization System (RTLS), which calculates the location. Our solution aims to be easy to install by using an IoT-standardized and low-power sub-GHz radio as backbone communication medium. Furthermore, using this low-power radio allows us to decrease the overall energy consumption of the anchors. In the demo we showcase that our solution does not require any wired connections and is a factor five more energy efficient than existing implementations.
2018 3rd Cloudification of the Internet of Things (CIoT), 2018
The Internet of Things (IoT) domain is characterized by many applications that require low bandwi... more The Internet of Things (IoT) domain is characterized by many applications that require low bandwidth communication over a long range at a low cost and at low power, which has given rise to novel Low Power Wide Area Network (LPWAN) technologies that operate in the sub-GHz domain. Today, these technologies are being adopted in more complex settings and configurations than originally intended. Devices are being equipped with multiple LPWAN radio technologies to satisfy more diverse requirements, connecting to different networks at different times and locations. Further, organizations can have devices with different LPWAN technologies in the field or existing infrastructure might be shared across different organizations. As a consequence, there arises an increasing complexity in managing such multimodal LPWANs and in designing IoT applications on top. We present and validate the concept of a cloud-based virtual LPWA network operator that unifies such multimodal communications and homogenizes the way such heterogeneous private LPWAN deployments are managed by means of distributed OMA Lightweight M2M (LwM2M) containers. In addition, our architecture provides support for the most recent efforts in adopting IPv6 for LPWAN communication.
Proceedings of the 15th ACM Conference on Embedded Network Sensor Systems, 2017
IEEE 802.11ah is a new Wi-Fi standard operating on unlicensed sub-GHz frequencies. It aims to pro... more IEEE 802.11ah is a new Wi-Fi standard operating on unlicensed sub-GHz frequencies. It aims to provide long-range connectivity to Internet of Things (IoT) devices. The IEEE 802.11ah restricted access window (RAW) mechanism promises to increase throughput and energy efficiency in dense deployments by dividing stations into different RAW groups and allowing only one group to access the channel at a time. In this demo, we demonstrate the ability of the RAW mechanism to support a large number of densely deployed IoT stations with heterogeneous traffic requirements. Differentiated Quality of Service (QoS) is offered to a small set of high-throughput wireless cameras that coexist with thousands of best-effort sensor monitoring stations. The results are visualized in near real-time using our own developed IEEE 802.11ah visualizer running on top of the ns-3 event-based network simulator.
This document describes a format to create entities that can be used for group communication usin... more This document describes a format to create entities that can be used for group communication using CoAP unicast messages.
While IEEE 802.15.4 and its Time Slotted Channel Hopping (TSCH) medium access mode were developed... more While IEEE 802.15.4 and its Time Slotted Channel Hopping (TSCH) medium access mode were developed as a wireless substitute for reliable process monitoring in industrial environments, most deployments use a single/static physical layer (PHY) configuration. Instead of limiting all links to the throughput and reliability of a single Modulation and Coding Scheme (MCS), you can dynamically re-configure the PHY of link endpoints according to the context. However, such modulation diversity causes links to coincide in time/frequency space, resulting in poor reliability if left unchecked. Nonetheless, to some level, intentional spatial overlap improves resource efficiency while partially preserving the benefits of modulation diversity. Hence, we measured the mutual interference robustness of certain Smart Utility Network (SUN) Orthogonal Frequency Division Multiplexing (OFDM) configurations, as a first step towards combining spatial re-use and modulation diversity. This paper discusses the p...
Proceedings of the 17th ACM Symposium on QoS and Security for Wireless and Mobile Networks, 2021
Bluetooth Mesh technology can be used to realize heterogeneous IoT networks, consisting of a smar... more Bluetooth Mesh technology can be used to realize heterogeneous IoT networks, consisting of a smart lighting backbone augmented with sensor-based applications. It offers many configuration options to adhere to the diverse application requirements and limit the overhead. Finding an optimal configuration of the network is a complex issue which leads to numerous performance-related questions. In this paper, Digital Twin technology is used to provide continuous and diverse insights into the network's behavior, under monitored or artificial network conditions. The twin is constantly connected to the physical network and combines selective simulation, graph algorithms and a data driven link model into a single toolbox. We evaluated its usage for smart lighting applications on a real-life testbed. The results indicate that the twin can produce end-to-end (E2E) latencies, E2E path distributions and a packet delivery ratio comparable to experiment outcomes in the physical network and in compliance with application requirements. Statistical validation of the similarity between measured and predicted E2E latency distributions indicates a Mean Absolute Error < 10 % and a positive discrete Kolmogorov-Smirnov test for all results.
Proceedings of the 10th Workshop on ns-3 - WNS3 '18, 2018
IEEE 802.11ah, marketed as Wi-Fi HaLow, is a new Wi-Fi standard for sub-1Ghz communications, aimi... more IEEE 802.11ah, marketed as Wi-Fi HaLow, is a new Wi-Fi standard for sub-1Ghz communications, aiming to address the major challenges of the Internet of Things (IoT), namely connectivity among a large number of densely deployed power-constrained stations. The standard was only published in May 2017 and hardware supporting Wi-Fi HaLow is not available on the market yet. As such, research on 802.11ah has been mostly based on mathematical and simulation models. Mathematical models generally introduce several simplifications and assumptions, which do not faithfully reflect real network conditions. As a solution, we previously developed an IEEE 802.11ah module for ns-3, publicly released in 2016. This initial release consisted of physical layer models for sub-1GHz communications and an implementation of the fast association and Restricted Access Window (RAW) channel access method. In this paper, we present an extension to our IEEE 802.11ah simulator. It contains several new features: an online RAW configuration interface, an energy state model, adaptive Modulation and Coding Scheme (MCS), and Traffic Indication Map (TIM) segmentation. This paper presents the details of our implementation, along with experimental results to validate each new feature. The extended Wi-Fi HaLow module can now support different scenarios with both uplink and downlink heterogeneous traffic, together with real-time RAW optimization, sleep management for energy conservation and adaptive MCS.
2018 IEEE Conference on Standards for Communications and Networking (CSCN), 2018
In order to extend the Internet technologies into constrained networks, there have been several r... more In order to extend the Internet technologies into constrained networks, there have been several research efforts and innovations over the past few years. These efforts resulted in several networking standards and protocols which have led to the emergence of the Internet of Things (IoT). Within this enormous ecosystem of protocols, the Lightweight Machine-to-Machine (LwM2M), a standard for device and service management, is a very promising candidate to achieve global interoperability, especially when constrained devices are involved. In this paper, we propose extensions to the LwM2M in order to improve communication efficiency and introduce Intermittent Connectivity, which will improve support for Low-Power Wide Area Networks (LPWANs) in LwM2M. For this purpose, we introduce two new object models, namely, Notify and Batch. The Notify Object enables the creation of reverse interaction models and Readyto-Receive (RTR) functionality, which allows LwM2M clients to send periodic updates of resources without any need for a request and to notify LwM2M servers that it is ready to receive downlink messages and to keep the network connectivity open if it is necessary for downlink communication. Finally, the Batch object allows LwM2M servers to perform actions on multiple resources in a device via a single request.
Industry 4.0 is being enabled by a number of new wireless technologies that emerged in the last d... more Industry 4.0 is being enabled by a number of new wireless technologies that emerged in the last decade, aiming to ultimately alleviate the need for wires in industrial use cases. However, wireless solutions are still neither as reliable nor as fast as their wired counterparts. Closed loop communication, a representative industrial communication scenario, requires high reliability (over 99%) and hard real-time operation, having very little tolerance for delays. Additionally, connectivity must be provided over an entire industrial side extending across hundreds of meters. IEEE 802.11ah fits this puzzle in terms of data rates and range, but it does not guarantee deterministic communication by default. Its Restricted Access Window (RAW), a new configurable medium access feature, enables flexible scheduling in dense, large-scale networks. However, the standard does not define how to configure RAW. The existing RAW configuration strategies assume uplink traffic only and are dedicated exclusively to sensors nodes. In this article, we present an integer nonlinear programming problem formulation for optimizing RAW configuration in terms of latency in closed loop communication between sensors and actuators, taking into account both uplink and downlink traffic. The model results in less than 1% of missed deadlines without any prior knowledge of the network parameters in heterogeneous time-changing networks. INDEX TERMS IEEE 802.11ah, industrial Internet of Things (IIoT), optimization, restricted access window (RAW), Wi-Fi HaLow, wireless automation.
To provide wireless coverage in challenging industrial environments, IEEE802.15.4 Time-Slotted Ch... more To provide wireless coverage in challenging industrial environments, IEEE802.15.4 Time-Slotted Channel Hopping (TSCH) presents a robust medium access protocol. Using multiple Physical Layers (PHYs) could improve TSCH even more in these heterogeneous environments. However, TSCH only defines one fixed-duration timeslot structure allowing one packet transmission. Using multiple PHYs with various data rates therefore does not yield any improvements because of this single-packet limitation combined with a fixed slot duration. We therefore defined two alternative timeslot structures allowing multiple packets transmissions to increase the throughput for higher data rate PHYs while meeting a fixed slot duration. In addition, we developed a flexible Link Quality Estimation (LQE) technique to dynamically switch between PHYs depending on the current environment. This paper covers a theoretical evaluation of the proposed slot structures in terms of throughput, energy consumption and memory constraints backed with an experimental validation, using a proof-of-concept implementation, which includes topology and PHY switching. Our results show that a 153 % higher net throughput can be obtained with 84 % of the original energy consumption and confirm our theoretical evaluation with a 99 % accuracy. Additionally, we showed that in a real-life testbed of 33 nodes, spanning three floors and covering 2550 m 2 , a compact multi-PHY TSCH network can be formed. By distinguishing between reliable and high throughput PHYs, a maximum hop count of three was achieved with a maximum throughput of 219 kbps. Consequently, using multiple (dynamic) PHYs in a single TSCH network is possible while still being backwards compatible to the original fixed slot duration TSCH standard.
Aside from vast deployment cost reduction, Industrial Wireless Sensor and Actuator Networks (IWSA... more Aside from vast deployment cost reduction, Industrial Wireless Sensor and Actuator Networks (IWSAN) introduce a new level of industrial connectivity. Wireless connection of sensors and actuators in industrial environments not only enables wireless monitoring and actuation, it also enables coordination of production stages, connecting mobile robots and autonomous transport vehicles, as well as localization and tracking of assets. All these opportunities already inspired the development of many wireless technologies in an effort to fully enable Industry 4.0. However, different technologies significantly differ in performance and capabilities, none being capable of supporting all industrial use cases. When designing a network solution, one must be aware of the capabilities and the trade-offs that prospective technologies have. This paper evaluates the technologies potentially suitable for IWSAN solutions covering an entire industrial site with limited infrastructure cost and discusses ...
IEEE Transactions on Network and Service Management, 2019
With the emergence of the Internet of Things (IoT) and Industry 4.0 concepts, industrial applicat... more With the emergence of the Internet of Things (IoT) and Industry 4.0 concepts, industrial applications are going through a tremendous change that is imposing increasingly diverse and demanding network dynamics and requirements with a wider and more fine-grained scale. Therefore, there is a growing need for more flexible and reconfigurable industrial networking solutions complemented with powerful monitoring and management functionalities. In this sense, this paper presents a novel efficient network monitoring and telemetry solution for Industrial Wireless Sensor Networks mainly focusing on the 6TiSCH Network stack, a complete protocol stack for ultrareliable ultra-low-power wireless mesh networks. The proposed monitoring solution creates a flexible and powerful in-band network telemetry design with minimized resource consumption and communication overhead while supporting a wide range of monitoring operations and strategies for dealing with various network scenarios and use cases. Besides, the technical capabilities and characteristics of the proposed solution are evaluated via a real-life implementation, practical and theoretical analysis. These experiments demonstrate that in-band telemetry can provide ultra-efficient network monitoring operations without any effect on the network behavior and performance, validating its suitability for Industrial Wireless Sensor Networks.
Radio frequency (RF)-based indoor positioning systems (IPSs) use wireless technologies (including... more Radio frequency (RF)-based indoor positioning systems (IPSs) use wireless technologies (including Wi-Fi, Zigbee, Bluetooth, and ultra-wide band (UWB)) to estimate the location of persons in areas where no Global Positioning System (GPS) reception is available, for example in indoor stadiums or sports halls. Of the above-mentioned forms of radio frequency (RF) technology, UWB is considered one of the most accurate approaches because it can provide positioning estimates with centimeter-level accuracy. However, it is not yet known whether UWB can also offer such accurate position estimates during strenuous dynamic activities in which moves are characterized by fast changes in direction and velocity. To answer this question, this paper investigates the capabilities of UWB indoor localization systems for tracking athletes during their complex (and most of the time unpredictable) movements. To this end, we analyze the impact of on-body tag placement locations and human movement patterns on localization accuracy and communication reliability. Moreover, two localization algorithms (particle filter and Kalman filter) with different optimizations (bias removal, non-line-of-sight (NLoS) detection, and path determination) are implemented. It is shown that although the optimal choice of optimization depends on the type of movement patterns, some of the improvements can reduce the localization error by up to 31%. Overall, depending on the selected optimization and on-body tag placement, our algorithms show good results in terms of positioning accuracy, with average errors in position estimates of 20 cm. This makes UWB a suitable approach for tracking dynamic athletic activities.
Current inventory-taking methods (counting stocks and checking correct placements) in large verti... more Current inventory-taking methods (counting stocks and checking correct placements) in large vertical warehouses are mostly manual, resulting in (i) large personnel costs, (ii) human errors and (iii) incidents due to working at large heights. To remedy this, the use of autonomous indoor drones has been proposed. However, these drones require accurate localization solutions that are easy to (temporarily) install at low costs in large warehouses. To this end, we designed a Ultra-Wideband (UWB) solution that uses infrastructure anchor nodes that do not require any wired backbone and can be battery powered. The resulting system has a theoretical update rate of up to 2892 Hz (assuming no hardware dependent delays). Moreover, the anchor nodes have an average current consumption of only 27 mA (compared to 130 mA of traditional UWB infrastructure nodes). Finally, the system has been experimentally validated and is available as open-source software.
Mesh networks enable a many-to-many relation between nodes, which means that each node in the net... more Mesh networks enable a many-to-many relation between nodes, which means that each node in the network can communicate with every other node using multi-hop communication and path diversity. As it enables the fast roll-out of sensor and actuator networks, it is an important aspect within the Internet of Things (IoT). Utilizing Bluetooth Low Energy (BLE) as an underlying technology to implement such mesh networks has gained a lot of interest in recent years. The result was a variety of BLE meshing solutions that were not interoperable because of the lack of a common standard. This has changed recently with the advent of the Bluetooth Mesh standard. However, a detailed overview of how this standard operates, performs and how it tackles other issues concerning BLE mesh networking is missing. Therefore, this paper investigates this new technology thoroughly and evaluates its performance by means of three approaches, namely an experimental evaluation, a statistical approach and a graph-ba...
LoRaWAN is one of the low power wide area network (LPWAN) technologies that have received signifi... more LoRaWAN is one of the low power wide area network (LPWAN) technologies that have received significant attention by the research community in the recent years. It offers low-power, low-data rate communication over a wide range of covered area. In the past years, the number of publications regarding LoRa and LoRaWAN has grown tremendously. This paper provides an overview of research work that has been published from 2015 to September 2018 and that is accessible via Google Scholar and IEEE Explore databases. First, a detailed description of the technology is given, including existing security and reliability mechanisms. This literature overview is structured by categorizing papers according to the following topics: (i) physical layer aspects; (ii) network layer aspects; (iii) possible improvements; and (iv) extensions to the standard. Finally, a strengths, weaknesses, opportunities and threats (SWOT) analysis is presented along with the challenges that LoRa and LoRaWAN still face.
Currently, applications in the Internet of Things (IoT) are tightly coupled to the underlying phy... more Currently, applications in the Internet of Things (IoT) are tightly coupled to the underlying physical devices. As a consequence, upon adding a device, device replacement or user’s relocation to a different physical space, application developers have to re-perform installation and configuration processes to reconfigure applications, which bears costs in time and knowledge of low-level details. In the emerging IoT field, this issue is even more challenging due to its current unpredictable growth in term of applications and connected devices. In addition, IoT applications can be personalised to each end user and can be present in different environments. As a result, IoT scenarios are very changeable, presenting a challenge for IoT applications. In this paper we present Appdaptivity, a system that enables the development of portable device-decoupled applications that can be adapted to changing contexts. Through Appdaptivity, application developers can intuitively create portable ...
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Papers by Jeroen Hoebeke