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A Centralized Controller for Reliable and Available Wireless Schedules in Industrial Networks
... Therefore, we use a centralized scheduling method and distribute it to the nodes. We should note that this schedule has been created manually, but it is possible to generate one automatically using a controller, as can be seen in [8]. ...
The Internet of Things (IoT) has become ubiquitous due to its flexibility, ease-of-use, and reduced cost. As a consequence, the industry is adopting these systems in its transformation into Industry 4.0. However, the strict Quality of Service (QoS) requirements of the industry are not met with the default best-effort provisions of the IoT. Most industrial applications require strict guarantees in terms of end-to-end network reliability and latency. For instance, consecutive packet losses can lead to communication disruptions in supply chain systems. Therefore, adaptations are being made to fulfill these requirements with the IEEE Std 802.15.4-2015 Time slotted Channel Hopping (TSCH) link-layer standard and the IPv6 Routing Protocol for Low-Power and Lossy Networks (RPL) standard at the Internet Engineering Task Force (IETF). However, even by employing such industrial protocols, it is still difficult to achieve the expected QoS levels. Considering that RPL constructs and maintains a single-path from a source to a destination if there are potential issues on this path (e.g., queue overflow, variable wireless link quality) packets may suffer unexpected delays and even drops. If we consider a multi-path implementation where each node can replicate a packet into several paths, the transmission reliability improves since each packet copy is used to forward the packet information. However, uncontrolled replication can lead to network flooding, resulting in excessive power consumption. In this article, we present On-Demand Selection (ODeSe), a novel multi-path routing algorithm, which improves our previous work, the Common Ancestor (CA) algorithms, by selecting the most suitable upward forwarders. Moreover, we use the Packet Automatic Repeat reQuest, Replication and Elimination, and Overhearing (PAREO) functions in order to improve network reliability and availability. In order to control the number of relay nodes during a transmission, ODeSe forces each node of the same relay level to select the same Preferred Parent (PP) and the same Alternative Parent (AP). Thus, we address the trade-off between the total number of traversed nodes in the network and high reliability. Using the Cooja network simulator running the Contiki OS, we compare ODeSe against single-path RPL and multi-path RPL with different alternative parent selection algorithms. The results demonstrate that ODeSe outperforms single-path RPL in terms of reliability, and multi-path RPL in terms of energy consumption while maintaining a 99.14% packet delivery ratio.
Due to uncontrolled interferences, including the self-induced multi-path fading, deterministic networking is difficult to achieve on wireless links. The radio conditions may change much faster than a centralized routing paradigm can adapt and reprogram, in particular when the controller is distant and connectivity is slow and limited. Reliable and Available Wireless (RAW) separates the routing time scale at which a complex path is recomputed from the forwarding time scale at which the forwarding decision is taken for an individual packet. RAW operates at the forwarded time scale. The RAW problem is to decide, within the redundant solutions that are proposed by the routing plane, which will be used for each individual packet to provide a Deterministic Networking (DetNet) service while minimizing the waste of resources. A solution would consist of a set of protocols that evaluate the media in real time and another that controls the use of redundancy and diversity attributes that are available along the path. In this paper, we first introduce the motivation behind this approach along with the industrial use cases that requires RAW characteristics. We then give an overview of the ongoing related works at the Internet Engineering Task Force (IETF). Finally, we present the RAW problem statement.
Important changes in electricity consumption model require a communication network within the electrical grid, which is called the Advanced Metering Infrastructure (AMI) that can handle the increase of multiple and fluctuating production sites. Recently, we witness the convergence of this communication network and the electricity network into what is now called Smart Grid. This communication network will serve the purpose of automatic meter reading, but new usages and services could be developed on top of this network. The massive integration of renewable energy sources will shift the production level close to the consumption sites. Therefore, new communication models are required to control the energy consumption depending on the production capabilities. In this Chapter, we explain why a two‐way communication network is necessary for future Smart Grid. Furthermore, we present the required network characteristics, and we particularly describe what are the current protocols selected to achieve these goals.
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.
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
Wireless Sensor Networks (WSN) are gaining popularity as a flexible and
economical alternative to field-bus installations for monitoring and control
applications. For mission-critical applications, communication networks must
provide end-to-end reliability guarantees, posing substantial challenges for
WSN. Reliability can be improved by redundancy, and is often addressed on the
MAC layer by re-submission of lost packets, usually applying slotted
scheduling. Recently, researchers have proposed a strategy to optimally improve
the reliability of a given schedule by repeating the most rewarding slots in a
schedule incrementally until a deadline. This Incrementer can be used with most
scheduling algorithms but has scalability issues which narrows its usability to
offline calculations of schedules, for networks that are rather static. In this
paper, we introduce SchedEx, a generic heuristic scheduling algorithm extension
which guarantees a user-defined end-to-end reliability. SchedEx produces
competitive schedules to the existing approach, and it does that consistently
more than an order of magnitude faster. The harsher the end-to-end reliability
demand of the network, the better SchedEx performs compared to the Incrementer.
We further show that SchedEx has a more evenly distributed improvement impact
on the scheduling algorithms, whereas the Incrementer favors schedules created
by certain scheduling algorithms.
Satisfiability Modulo Theories (SMT) problem is a decision problem for logical first order formulas with respect to combinations of background theories such as: arithmetic, bit-vectors, arrays,
and uninterpreted functions. Z3 is a new and efficient SMT Solver freely available from Microsoft Research. It is used in
various software verification and analysis applications.
The Internet Engineering Task Force 6TiSCH Working Group standardizes the protocol stack for the Industrial Internet of Things, which combines the industrial performance of IEEE802.15.4 time-slotted channel hopping (TSCH) with the addressability and Internet integration capabilities of Internet Protocol version 6. The 6top Protocol, which is part of 6TiSCH, allows distributed management of the TSCH communication schedule. The Scheduling Function Zero (SF0) is the default algorithm for a node to decide when to add/remove cells to its neighbors. SF0 picks the cells to add randomly; hence, it is possible that 2 nearby pairs of nodes pick the same cell, resulting in a schedule collision. This article introduces cost-aware cell relocation (CCR), which is a solution to detect and fix such schedule collisions in a distributed manner. CCR monitors the performance of individual cells and uses that information to detect collisions. When such a collision is detected on a cell, neighbor nodes communicate to relocate that cell to a different slot/channel in the TSCH schedule. We implement CCR and run it on a 5-node network on the Internet of Things Laboratory testbed. The results show that, compared with today's SF0 and for the same traffic requirements, CCR increases the average packet delivery ratio by 2% and reduces the number of cells that need to be scheduled by 27.3%.
The wide deployment of lower-cost wireless devices will significantly improve the productivity and safety of industrial plants while increasing the efficiency of plant workers by extending the information set available about the plant operations. The aim of this document is to analyze the functional requirements for a routing protocol used in industrial Low-power and Lossy Networks (LLNs) of field devices.
As exposed in a recent report by General Electric, an industrial Internet of Things (IoT) is emerging as a commercially viable embodiment of the IoT where physical sensors gather data readings from the field and deliver the traffic to the Internet. The collected real-time big data, in turn, allow the optimizing of entire industry verticals with enormous return of investments. Although opportunities are ample, it comes along with serious engineering design challenges as industrial applications have stringent requirements on delay, lifetime and standards-compliance. To this end, we advocate the use of an IEEE/IETF standardized IoT architecture along with a recently introduced data-centric scheduling algorithm known as traffic aware scheduling algorithm (TASA). Applying graph theoretical tools to the multi-channel, time-synchronized, and duty-cycled nature of TASA, we rigorously derive optimality and bounds on the minimum number of needed active slots (impacting end-to-end delays) and the network duty-cycle (impacting lifetime). We demonstrate the enormous superiority of TASA over traditional IEEE802.15.4/ZigBee approaches in terms of energy efficiency. The outcome of this paper is currently to lay foundations of the recently formed IETF standardization group 6TSCH with the aim to significantly improve IoT data flows over IEEE802.15.4e TSCH and IETF 6LoWPAN/ROLL enabled technologies.
Reliable and Available Wireless Technologies
- P Thubert
- D Cavalcanti
- X Vilajosana
- C Schmitt
Reliable and Available Wireless Technologies
- thubert