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Towards wireless industrial control over 6TiSCH networks
Abstract
IETF 6TiSCH is emerging as a promised open-standard for industrial internet of things (IIoT). With employing Time Slotted Channel Hopping (TSCH) mode, 6TiSCH can meet critical requirements in the industrial sector such as reliability, determinism and real time. 6TiSCH is currently focusing on monitoring applications. This paper considers its applicability in industrial control, in which sensor and actuator are coexistent in the network. We first investigate applicable wireless sensor-actuator models based on 6TiSCH. Then, an efficient data transmission scheme between sensor and actuator is proposed. Through simulation results, we show that our solution achieves a significant improvement in terms of end-to-end latency and energy consumption compared to the bursty transmission in the 6TiSCH networks.
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Wireless industrial networks require reliable and deterministic communication. Determinism implies that there must be a guarantee that each data packet will be delivered within a bounded delay. Moreover, it must ensure that the potential congestion or interference will not impact the predictable properties of the network. In 2016, IEEE 802.15.4-Time-Slotted Channel Hopping (TSCH) emerged as an alternative Medium Access Control to the industrial standards such as WirelessHART and ISA100.11a. However, TSCH is based on traditional collision detection and retransmission, and can not guarantee reliable delivery within a given time. This article proposes LeapFrog Collaboration (LFC) to provide deterministic and reliable communication over an RPL-based network. LFC is a novel multi-path routing algorithm that takes advantage of route diversity by duplicating the data flow onto an alternate path. Simulations and analytical results demonstrate that LFC significantly outperforms the single-path retransmission-based approach of RPL+TSCH and the state-of-the-art LinkPeek solution.
With the emergence of the Internet of Things (IoT), Industry 4.0 and Cyber-Physical System (CPS) concepts, there is a tremendous change ongoing in industrial applications that is imposing increasingly diverse and demanding network dynamics and requirements with a wider and more fine-grained scale. The purpose of this article is to investigate how a Hybrid Schedule Management in 6TiSCH architecture can be used to achieve the coexistence of applications with heavily diverse networking requirements. We study the fundamental functionalities and also describe network scenarios where such a hybrid scheduling approach can be used. In addition, we present the details about the design and implementation of the first 6TiSCH Centralized Scheduling Framework based on CoMI. We also provide theoretical and experimental analysis where we study the cost of schedule management operations and illustrate the operation of the CoMI-based 6TiSCH Schedule Management.
The IEEE 802.15.4e standard is an amendment of the IEEE 802.15.4-2011 protocol by introducing time-slotted channel hopping access behavior mode. However, the IEEE 802.15.4e only defines time-slotted channel hopping link-layer mechanisms without an investigation of network formation and communication scheduling which are still open issues to the research community. This article investigates the network formation issue of the IEEE 802.15.4e time-slotted channel hopping networks. In time-slotted channel hopping networks, a joining node normally takes a long time period to join the network because the node has to wait until there is at least one enhanced beacon message advertised by synchronized nodes (synchronizers) in the network on its own synchronization channel. This leads to a long joining delay and high energy consumption during the network formation phase, especially so in highly dynamic networks in which nodes join or rejoin frequently. To enable a rapid time-slotted channel hopping network formation, this article proposes a new design for slotframe structure and a novel adaptive joining scheme based on fuzzy logic. Our proposed scheme enables a synchronizer to be able to adaptively determine an appropriate number of enhanced beacons it should advertise, based on the number of available synchronizers in the network, so that joining nodes can achieve a short joining time while energy consumption of enhanced beacon advertisement at the synchronizers is optimized. Through extensive mathematical analysis and experimental results, we show that the proposed scheme achieves a significant improvement in terms of joining delay compared to state-of-the-art studies.
In this paper we present an innovative monitoring system, namely TLSensing, that can be integrated in future aerial vehicles for supporting the development of advanced health management systems. Based on the revolutionary Internet of Things paradigm and emerging open standards for low-power and short-range wireless technologies, it intends to enable pervasive monitoring services through the diffusion of a large number of sensors around the aircraft, which continuously capture critical and non critical parameters from on-board equipments and the environment and deliver them to the remote monitoring devices through wireless communication links. In summary, TLSensing is composed by a number of constrained devices equipped with sensing and wireless communication capabilities, a central system coordinator that controls data acquisition processes through a dedicated monitoring software, and a web server application that collects data coming from the network and makes them available to the user and to external software entities belonging to the health management system. Starting from the description of the technological background that motivated the development of the presented platform, we will carefully describe both hardware and software components integrated in TLSensing, alongside their interaction and the most important features they cover. Moreover, to provide a further insight, we will also present how TLSensing works by showing some measurements collected with an experimental testbed deployed in our research laboratory.
Low-Power and Lossy Networks (LLNs) are a class of network in which
both the routers and their interconnect are constrained. LLN routers
typically operate with constraints on processing power, memory, and
energy (battery power). Their interconnects are characterized by
high loss rates, low data rates, and instability. LLNs are comprised
of anything from a few dozen to thousands of routers. Supported
traffic flows include point-to-point (between devices inside the
LLN), point-to-multipoint (from a central control point to a subset
of devices inside the LLN), and multipoint-to-point (from devices
inside the LLN towards a central control point). This document
specifies the IPv6 Routing Protocol for Low-Power and Lossy Networks
(RPL), which provides a mechanism whereby multipoint-to-point traffic
from devices inside the LLN towards a central control point as well
as point-to-multipoint traffic from the central control point to the
devices inside the LLN are supp
Intra-vehicle Wireless Sensor Networks (WSNs) require reliable and real-time data delivery. The Time-Slotted Channel Hopping (TSCH) mode of the IEEE 802.15.4 standard provides a reliable solution for low-power networks through guaranteed medium access and channel diversity. However, satisfying the stringent requirements of dense in-vehicle networks demands for special consideration in network formation and TSCH scheduling. This paper targets convergecast in dense in-vehicle WSNs in which all nodes can potentially directly reach the sink node. A cross-layer Low-Latency Topology management and TSCH scheduling (LLTT) technique is proposed that provides a very high timeslot utilization for the TSCH schedule and minimizes communication latency. Two techniques, namely grouped retransmission and periodic aggregation, are also exploited to increase the performance of the TSCH communications. The experimental results show that LLTT reduces the end-to-end communication latency compared to other approaches, while keeping the communications reliable by using dedicated links and grouped retransmissions.
Recently, the new IETF 6TiSCH Working Group (WG) was created to enable the IPv6 over the deterministic Time Slotted Channel Hopping (TSCH) mode of the 802.15.4e standard for the Industrial Internet of Things (IIoT). Due to the dynamic nature of the target network environment, the 6TiSCH WG is now calling for an efficient distributed scheduling through a Scheduling Function in which the neighbor nodes negotiate with one another to add/delete cells to satisfy the bandwidth requirement. A Scheduling Function consists of the following two main points: when a node should add/delete one or more cells to its neighbor, and the cells that should be selected. Although several Scheduling Function studies have been conducted, the primary focus of the current works is the first point, while the optimal selection method regarding the cells remains
an unresolved issue. In this paper, a reliable distributed cell-selection mechanism for the Scheduling Function in the 6TiSCH networks is proposed. The simulation and experiment results show that the proposed mechanism helps in the reductions of the negotiation-error ratio, the number of colliding cells and the signaling overhead compared with the state-of-the-art approaches.
Safety function response time is a metric for safety-critical automation systems defined in the IEC 61784-3-3 standard for single input and single output systems communicating over wired technologies. We propose a model to estimate the safety function response time for a multiple input and multiple output feedback control loop system communicating wirelessly over one of the modes defined in the IEEE 802.15.4e standard that was specifically designed for process automation. Our model merges the architecture and safety requirements defined in the IEC 61784-3-3 standard with the communication protocol defined in the IEEE 802.15.4e standard. We present equations for the worst case delay time and watchdog timer of the participating network entities, and demonstrate the application of our model via an example of a multiple input and multiple output system implementing a feedback control loop.
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.
Wireless Sensor–Actuator Networks (WSANs) have a myriad of applications, ranging from pacifying bulls to controlling light intensity in homes automatically. An important aspect of WSANs is coordination. Unlike conventional Wireless Sensor Networks (WSNs), sensor and actuator nodes must work hand-in-hand to collect and forward data, and act on any sensed data collaboratively, promptly and reliably. To this end, this paper reviews current state-of-the-art techniques that address this fundamental problem. More specifically, we review techniques in the following areas: (i) sensor–actuator coordination, (ii) routing protocols, (iii) transport protocols, and (iv) actuator-to-actuator coordination protocols. We provide an extensive qualitative comparison of their key features, advantages and disadvantages. Finally, we present unresolved problems and future research directions.
The constrained application protocol (CoAP)
- Z Shelby
- Shelby
Z. Shelby, et al., The constrained application protocol (CoAP), RFC7252
(2014). https://tools.ietf.org/html/rfc7252
Neighbor discovery optimization for ipv6 over low-power wireless personal area networks (6lowpans) RFC
- Z Shelby
Z. Shelby, et al., Neighbor discovery optimization for ipv6 over low-power
wireless personal area networks (6lowpans), RFC 6775 (2012)
"https://tools.ietf.org/html/rfc6775".
On-the-Fly Bandwidth Reservation for 6TiSCH Wireless Industrial Networks
- Maria Rita Palattella
Hybrid Schedule Management in 6TiSCH Networks: The Coexistence of Determinism and Flexibility
- Abdulkadir Karaagac
- T Chang
T. Chang, et al., 6TiSCH Minimal Scheduling Function (MSF), IETF Draft (2018),
https://tools.ietf.org/html/draft-chang-6tisch-msf-02
RPL: IPv6 routing protocol for low power and lossy networks
- T Winter
- Winter