The so-called Industrial Internet of Things (IIoT) is expected to transform our world, and in depth modernize very different domains such as manufacturing, energy, agriculture, construction industry, and other industrial sectors. The need for low power radio networks first led to low duty cycle approaches where nodes turn off their radio chipset most of the time to save energy. The medium access control (MAC) has thus been largely investigated over the last fifteen years. Unfortunately, classical contention access methods use a random access and are unable to provide guarantees. In the meantime, some dedicated standards have emerged (e.g. IEEE 802.15.4-2006, IEEE 802.15.4-2015), combining Time Division Multiple Access (TDMA) with slow channel hopping in order to enable reliability and energy efficiency. Slow channel hopping allows each node to use different channels for a frame and its possible retransmissions with a low-cost hardware. To provide high-reliability, these protocols rely on a common schedule in order to prevent simultaneously interfering transmissions. In this context, we clearly observe a strong growth of the number of proposals in the last years, denoting a strong interest of the research community for deterministic slow channel hopping scheduling for the IIoT. We categorize here the numerous existing solutions according to their objectives (e.g. high-reliability, mobility support) and approaches. We also identify some open challenges, expected to attract much attention over the next few years.
Abs tract. Semantic clustering is a recent technique for saving energy in wireless sensor networks. Its mechanism of action consists in dividing the network into groups (clusters) formed by semantically related nodes and at least one semantic collector, which acts as a bridge between its internal nodes and the sink node. Since semantic collector nodes need to perform more tasks than normal nodes, they deplete their energy budget faster, so it is necessary to use efficient mechanisms for electing semantic collectors to prolong the network lifetime. Our hypothesis is that an effective choice of semantic collectors allows a longer network lifetime. To test it, we start from a previous work of the authors of this article and we propose an algorithm for electing semantic collectors in a distributed way based on a fuzzy inference engine. The inputs of the inference engine are the residual energy of nodes and their received signal strength indicator (RSSI). Simulation results confirm our hypothesis, since the algorithm provides (i) an improvement of 17.4% in relation to another proposal of the related literature, and (ii) a gain of 68.8% over the time life of the network's original work.
Industrial networks differ from others kinds of networks because they require real-time performance in order to meet strict requirements. With the rise of low-power wireless standards, the industrial applications have started to use wireless communications in order to reduce deployment and management costs. IEEE802.15.4-TSCH represents currently a promising standard relying on a strict schedule of the transmissions to provide strong guarantees. However, the radio environment still exhibits time-variable characteristics. Thus, the network has to provision sufficient resource (bandwidth) to cope with the worst case while still achieving high energy efficiency. The 6TiSCH IETF working group defines a stack to tune dynamically the TSCH schedule. In this paper, we analyze in depth the stability and the convergence of a 6TiSCH network in an indoor testbed. We identify the main causes of instabilities, and we propose solutions to address each of them. We show that our solutions improve significantly the stability.
Industrial networks are typically used to monitor safetyrelated processes where high reliability and an upper bounded latency are crucial. Because of its flexibility, wireless is more and more popular, even for real-time applications. Because radio transmissions are known to be lossy, deterministic protocols have been proposed, to schedule carefully the transmissions to avoid collisions. In parallel, industrial environments now integrate mobile industrial robots to enable the Industry 4.0. Thus, the challenge consists in handling a set of mobile devices inside a static wireless network infrastructure. A mobile robot has to join the network before being able to communicate. Here, we analyze this attachment delay, comprising both the synchronization, and the negotiation of dedicated cells. In particular, since the control frames (EB and 6P) have a strong impact on the convergence, our proposed model carefully integrates the collision probability of these packets. We validate the accuracy of our model, and we analyze the impact of the different EB transmission policies on the discovery delay. Our performance evaluation demonstrates the interest of using efficiently the radio resources for beacons to handle these mobiles devices.
An increasing number of industrial applications rely on low power embedded devices because of their flexibility. To work properly, the network has to respect requirements concerning specifically the delay and the reliability. Fortunately, low power, and slow channel hopping MAC help to cope with these requirements. For instance, IEEE802.15.4-TSCH relies on a strict schedule of the transmissions, spread over orthogonal radio channels, to setup a resilient wireless infrastructure. A routing protocol (e.g. RPL) has then to construct energy-efficient routes on top of this link-layer topology. Unfortunately, the radio environment keeps on exhibiting time-varying characteristics, due to e.g. obstacles, and external interference. In a reservation-based stack, the network will have to implement over-provisioning, to cope with small-term variations: additional resources allow the network to operate in the worst situation. Inversely, long-term changes are triggered only when a node/link failure is detected. In this paper, we investigate experimentally the performance stability of a 6TiSCH/ IETF/ RPL stack in collocated deployments. We focus on some key metrics to exhibit the intermittent losses of guarantees (e.g. delivery ratio) under yet static conditions. Our results in large scale testbeds highlight that in the presence of radio oscillations, 6TiSCH introduces frequent network reconfigurations to combat interference and provide high reliability. We perform a multi-layer analysis of the 6TiSCH stack identifying the main sources of instability and proposing solutions to address each one of them. Our performance evaluation highlights the accuracy of our solutions to set up an efficient and reliable network.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.