Time Slotted Channel Hopping Research Articles

On-the-Fly Bandwidth Reservation for 6TiSCH Wireless Industrial Networks

In smart factory applications, sensors, actuators, field devices, and supervision systems often require a high degree of reliability and timeliness in information exchange. The quality of service provided by the underlying industrial communication network is a key requisite for quality of control. In this context, the WirelessHART, ISA100.11a, and IEEE802.15.4e time-slotted channel hopping standards contribute novel protocols to support quasi-deterministic services, based on wireless short-range communication technologies. The recently created IETF 6TiSCH working group binds IPv6 to this market. Within the 6TiSCH architecture, the 6top sublayer manages the way communication resources are scheduled in time and frequency. The on-the-fly (OTF) bandwidth reservation module plays a complementary role; it is a distributed approach for adapting the scheduled bandwidth to network requirements. This paper first describes the OTF module and its interactions with the 6top sublayer. It then presents the simulation results of the OTF, drawn from a realistic 50-sensor mote multi-hop network that models a small industrial plant. Results show that the OTF can attain an end-to-end latency of the order of a second, with over 99% end-to-end reliability. The first real-world OTF implementation in OpenWSN is presented to demonstrate that it can easily be added within the 6TiSCH architecture.

Mobility Aware Framework for Timeslotted Channel Hopping IEEE 802.15.4e Sensor Networks

Ubiquitous object networking has sparked the concept of the Internet of Things (IoT), which defines a new era in the world of networking. Realization of this concept needs to be addressed by standardization efforts that will shape the infrastructure of the networks. This has been achieved through the IEEE 802.15.4e, 6LoWPAN, and IPv6 standards. In addition, the IEEE 802.15.4e standard, which can be considered as the backbone of the IoT structure, has presented timeslotted channel hopping (TSCH). Although these standards provide a coherent and diffused system, several implications challenge these standards to achieve optimal performance and reliability. Node mobility can be considered as the delimited factor for realizing a fully connected network, especially with the inclusion of TSCH mode that will complicate the association process of the mobile nodes, as a result of the frequency hopping mechanism. In this paper, we investigate the impact of mobility over the TSCH sensor network, and a Markov chain model is presented to determine the parameters that affect mobile node association process. Second, we provide a proposed mobility-aware Mobile Timeslotted Channel Hopping (MTSCH) protocol that will facilitate the mobile nodes association and minimize the latency incurred by leaving the nodes dissociated from the network. TSCH and the proposed MTSCH techniques have been implemented and evaluated through Contiki OS. The proposed MTSCH manages to reduce the radio duty cycle of the mobile nodes by an average of 30% while increasing the connectivity of the nodes by 25%. Moreover, cluster heads managed to save energy by a ratio of 14%.

Decentralized Traffic Aware Scheduling in 6TiSCH Networks: Design and Experimental Evaluation

This paper capitalizes on two emerging trends, i.e., the growing use of wireless at the edge of industrial control networks and the growing interest to integrate IP into said networks. This is facilitated by recent design contributions from the IEEE and the IETF, where the former developed a highly efficient deterministic time–frequency scheduled medium access control protocol in the form of IEEE 802.15.4e timeslotted channel hopping (TSCH) and the latter IPv6 networking paradigms in the form of 6LoWPAN/ROLL, and scheduling approaches in the form of 6TiSCH. The focus of the present work is on advancing the state-of-the-art of deterministic 6TiSCH schedules toward more flexible but equally reliable distributed approaches. In addition, this paper aims to introduce the first implementation of 6TiSCH networks for factory automation environments: it outlines the challenges faced to overcome the scalability issues inherent to multihop dense low-power networks; the experimental results confirm that the naturally unreliable radio medium can support time-critical and reliable applications. These developments pave the way for wireless industry-grade monitoring approaches.

When Scavengers Meet Industrial Wireless

Recent standardization efforts on industrial low-power wireless communication technologies clearly bet for the Time Slotted Channel Hopping (TSCH) medium access control (MAC) layer as it proved to achieve 99.999% reliability while ensuring deterministic behavior. Standards such as WirelessHART, ISA100.11a, and IEEE802.15.4e rooted at the TSCH MAC layer are used to connect millions of industrial devices today, enabling the emergence of the Industrial Internet paradigm. At that point and due to the ultralow energy profile of TSCH networks, scavengers come into play, enabling autonomously powered control and monitoring systems on industries. However, putting these systems together requires a clear understanding of their behavior. Therefore, this paper presents a methodology and a model to reliably dimension scavenger properties to network requirements and application needs, allowing industries to optimize the adoption of that technologies while keeping technical risks low.

Adaptive synchronization in multi-hop TSCH networks

Time Slotted Channel Hopping (TSCH) enables highly reliable and ultra-low power wireless networking, and is at the heart of multiple industrial standards. It has become the de facto standard for industrial low-power wireless solutions, and a true enabler for the Industrial Internet of Things. In a TSCH network, all nodes remain tightly synchronized by periodically communicating with one another to compensate for clock drift. The synchronization algorithm used in a network determines how often the nodes need to re-synchronize, which greatly influences their energy consumption.This article presents an adaptive synchronization technique which allows a node to learn and predict how its clock is drifting relative to its neighbors’, and coordinates the instants at which the nodes re-synchronize. This technique increases synchronization accuracy, while reducing synchronization communication overhead, thereby extending the battery lifetime of the network.Through simulation, we show how adaptive synchronization allows the nodes in a 3-hop deep network to maintain synchronization within 76μs of one another, while sending an average of only 18.9 re-synchronization packets per hour, a 83% reduction compared to a network not using adaptive synchronization. Through experimentation on a range of hardware platforms, we show how adaptive synchronization is needed for interoperability.

Security Protocols and Privacy Issues into 6LoWPAN Stack: A Synthesis

With the emergence of the Internet of Things (IoT), many devices organized into network, communicate by themselves on the Internet, and send data or private information on the web. It is essential to secure the transmitted data and the identities that may be disclosed to make these new technologies accepted by the largest number of citizens. However, the security mechanisms that are widely used on the Internet are too heavy to be integrated on small constrained objects. This paper describes the current protocols and security solutions that can be deployed in constrained resources. It shows the benefits and the limitations of each scheme-the security extension of IEEE 802.15.4e in time-slotted channel hopping (TSCH) mode, compressed IPsec, datagram transport layer security (DTLS)-embedded at different levels of the OSI model into the 6LoWPAN stack. It opens with the challenge that one must tackle in the coming years. Several use cases are studied to envisage the security integration in cyber physical systems (CPSs) for host-to-host and host-to-network communications. The privacy issue is also addressed and different ways to hide the device identity are discussed.

Standardized Low-Power Wireless Communication Technologies for Distributed Sensing Applications

Recent standardization efforts on low-power wireless communication technologies, including time-slotted channel hopping (TSCH) and DASH7 Alliance Mode (D7AM), are starting to change industrial sensing applications, enabling networks to scale up to thousands of nodes whilst achieving high reliability. Past technologies, such as ZigBee, rooted in IEEE 802.15.4, and ISO 18000-7, rooted in frame-slotted ALOHA (FSA), are based on contention medium access control (MAC) layers and have very poor performance in dense networks, thus preventing the Internet of Things (IoT) paradigm from really taking off. Industrial sensing applications, such as those being deployed in oil refineries, have stringent requirements on data reliability and are being built using new standards. Despite the benefits of these new technologies, industrial shifts are not happening due to the enormous technology development and adoption costs and the fact that new standards are not well-known and completely understood. In this article, we provide a deep analysis of TSCH and D7AM, outlining operational and implementation details with the aim of facilitating the adoption of these technologies to sensor application developers.

A Realistic Energy Consumption Model for TSCH Networks

Time slotted channel hopping (TSCH) is the highly reliable and ultra-low power medium access control technology at the heart of the IEEE802.15.4e-2012 amendment to the IEEE802.15.4-2011 standard. TSCH networks are deterministic in nature; the actions that occur at each time slot are well known. This paper presents an energy consumption model of these networks, obtained by slot-based “step-by-step” modeling and experimental validation on real devices running the OpenWSN protocol stack. This model is applied to different network scenarios to understand the potential effects of several network optimization. The model shows the impact of keep-alive and advertisement loads and discusses network configuration choices. Presented results show average current in the order of 570 <formula formulatype="inline" xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex Notation="TeX">$\mu{\rm A}$</tex></formula> on OpenWSN hardware and duty cycles 1% in network relays in both real and simulated networks. Leaf nodes show 0.46% duty cycle with data rates close to 10 packets per minute. In addition, the model is used to analyze the impact on energy consumption and data rate by overprovisioning slots to compensate for the lossy nature of these networks.

Performance Analysis of IEEE 802.15.4e Time Slotted Channel Hopping for Low-Rate Wireless Networks

The release of IEEE 802.15.4e specification significantly develops IEEE 802.15.4. The most inspiring improvement is the enhancement for medium access control (MAC) sublayer. To study the performance of IEEE 802.15.4e MAC, in this paper we first present an overview of IEEE 802.15.4e and introduce three MAC mechanisms in IEEE 802.15.4e. And the major concern here is the Time Slotted Channel Hopping (TSCH) mode that provides deterministic access and increases network capacity. Then a detailed analytical Markov chain model for TSCH carrier sense multiple access with collision avoidance (CSMA-CA) is presented. Expressions which cover most of the crucial issues in performance analysis such as the packet loss rate, energy consumption, normalized throughput, and average access delay are presented. Finally the performance evaluation for the TSCH mode is given and we make a comprehensive comparison with unslotted CSMA-CA in non-beacon enabled mode of IEEE 802.15.4. It can validate IEEE 802.15.4e network can provide low energy consumption, deterministic access and increase network capacity.