Article

# FAN: Fast and Active Network formation in IEEE 802.15.4 TSCH networks

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## Abstract

The IEEE 802.15.4 TSCH standard is designed to improve the reliability, timeliness, and energy efficiency of short-range wireless communications in industrial applications. TSCH relies upon a network formation process to efficiently create and maintain a synchronized reliable mesh network. The standard adopts a purely passive scan mechanism enabling joining nodes to listen to periodic Enhanced Beacons (EBs) in order to locate a TSCH network and associate to it. Nevertheless, the standard defines neither the advertisement strategy nor the rate at which the EBs should be sent. Consequently, long (re)association times might be observed, which postpones the proper functioning of the network and might have devastating consequences on the industrial application. In this paper, we propose a Fast and Active Network formation scheme (FAN) that leans on active scan procedures and Trickled beacon advertising strategies to accelerate the (re)association process. To do so, FAN equips joiners with a collision avoidance mechanism and allows them to initiate EB requests, on free channels, to trigger EBs. FAN is implemented in Contiki and evaluated through extensive realistic simulations and public testbed experiments. Obtained results assert the robustness of FAN compared to state-of-the-art solutions in terms of association times and overhead.

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... Finally, our recent work [31] proposes FAN a Fast and Active Network Formation in IEEE 802.15.4 TSCH Networks. This solution leans on active scan procedures and Trickled beacon advertising strategies to accelerate the association process. ...
... However, all the above-mentioned solutions still in essence based on trade-off when using passive-scan. Concerning the FAN solution [31], indeed, this solution is active scan-based and enhances the performance of the network during the formation process. However, it does not take into account energy considerations since the joining nodes remain always-on during the formation process. ...
... Hence, collisions with other TSCH packets will be avoided. Alternatively, we can consider the use of a collision avoidance mechanism that has been developed in our recent work [31] to not conflict with the running schedule and avoid potential collisions. This mechanism is designed in a way to perform a Clear Channel Assessment (CCA) before sending every single EBR and abort EBR transmissions if the channel is found to be busy. ...
Article
The Time Slotted Channel Hopping (TSCH) mode of the IEEE 802.15.4 standard is expected to revolutionize the Industrial Internet of Things. Indeed, it can achieve high reliability and deterministic latency with a very low duty cycle. Nevertheless, forming a TSCH network with the standard approach might not be as efficient, constituting, thus, one of the TSCH’s major issues. Such a network formation process relies on nodes passively scanning for advertised Enhanced Beacon (EB) frames to join the network. Doing so, a node wishing to join a TSCH network may stay awake randomly scanning for EBs for a considerable period of time, leading to a lengthy formation process with excessive energy consumption. To deal with these issues, this paper presents a practical and effective Radio duty-cycled, Active-Scan based network formation process for TSCH networks (RAST). Our proposal leans on active-scan procedures combined with radio duty cycling mechanisms to shorten joining delays and reduce energy consumption. Obtained results from extensive and realistic simulations show that our solution is efficient and outperforms state-of-the-art solutions, regarding the association time and energy consumption by up to two orders of magnitude.
... At the beginning, researchers proposed different approaches such as transmission of more number of EB frames in a slotframe [22], efficient selection of the collision-free EB broadcasting slots [23]- [26] and active EB scanning [27]- [29] to reduce the initial channel scanning time of the pledges. However, their solutions are limited to TSCH synchronization and allow only one-hop communication, where only the transmission of EB frame is considered. ...
Article
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IEEE has standardized the 802.15.4e Time Slotted Channel Hopping (TSCH) mode to provide stringent latency, higher reliability, and low duty-cycle in various Internet of Things (IoT) applications. TSCH eliminates interference and multi-path fading on channels, but its channel hopping feature severely affects the 6TiSCH (IPv6 over IEEE 802.15.4e TSCH mode) network formation. Further, 6TiSCH Minimal Configuration standard does not provide sufficient bandwidth (i.e., minimal cell) for quick transmission of control packets required by the new nodes (i.e., pledges) during their network association. Many works have been proposed on 6TiSCH network formation as it has high impact on network performance and lifetime. However, the existing works either did not use all the available physical channels while allocating minimal cell(s) or are not stable with topology changes. Therefore, this work proposes a Time-Variant RGB (TRGB) model for minimal cell allocation and scheduling, which results in faster association of pledges and maintains network stability. We evaluate the TRGB using Markov Chain model and also on a real 60-node testbed in FIT IoT-LAB. Testbed results show that TRGB achieves 51% and 23% improvement over the state-of-the-art scheme in terms of joining time and energy consumption, respectively, while maintaining stability of the network.
... This process is inherently prone to errors (e.g., beacon storms [19]), and it can be energy inefficient and time-consuming if the packet overhead is high. Not many alternative association proposals exist; however, a few proposals can be found made by authors in [20][21][22] and in more advanced MACs in [23][24][25]. The standard addresses directly this problem to some degree in its IEEE 802.15.4e-2012 [26] amendment and is part of the latest revision of the standard [27]. ...
Article
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The IEEE 802.15.4 is a popular standard used in wireless sensor networks (WSNs) and the Internet of Things (IoT) applications. In these networks, devices are organized into groups formally known as personal area networks (PAN) which require a bootstrap procedure to become operational. Bootstrap plays a key role in the initialization and maintenance of these networks. For this reason, this work presents our implementation and performance analysis for the ns-3 network simulator. Specifically, this bootstrap implementation includes the support of three types of scanning mechanisms (energy scan, passive scan, and active scan) and the complete classic association mechanism described by the standard. Both of these mechanisms can be used independently by higher layers protocols to support network initialization, network joining, and maintenance tasks. Performance evaluation is conducted in total network association time and packet overhead terms. Our source code is documented and publicly available in the latest ns-3 official release.
... In [27] a dynamic algorithm to allocate resources during network bootstrap is given to guarantee fast join to TSCH network and distribute routing information properly. In [28], it is declared that the TSCH standard defines neither the advertisement strategy nor the rate of the transmission of proper EBs, then a Fast and Active Network formation (FAN) is proposed to accelerate the (re)association process. A key operation of FAN is to allow joiners to send EB requests to trigger EBs. ...
Article
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In a real-time wireless sensor network (RT-WSN), an unpredictable time length of the synchronization (or connection) process between nodes is generally a pity, though the communication after the connection may be controllable. The purpose of this paper is to solve this kind of pity based on the multiple-request-single occasion (multiple slave nodes request to send data to a single master node simultaneously before getting synchronized using the frequency channel hopping technique). Suppose that the master sends the synchronization packet (or beacon ) and the slaves scan for this packet with different channels for connection. A slave getting synchronized with the master means that both nodes have just selected an identical frequency channel during a time region and the slave has received the synchronization packet successfully in this region, which is called frequency and time synchronization , abbreviated as FTS . For many existing wireless protocols, if they are directly adopted in this situation, two deficiencies exist as for real-time performances: First, the time length required for a slave to join the network is often not deterministic if one or more channels are disturbed. Second, when multiple slaves do their scanning simultaneously, which slave can synchronize with the master first is unpredictable so that a slave with a lower priority may be serviced prior to others. In this paper, two FTS examples with poor real-time performances are provided first. Then, a synchronization method named 1/ $2n$ FTS is presented and proved. With this method, a slave scans for the synchronization packet of the master with $n$ different available channels repeatedly until it gets the packet while the master transmits the packet $2n$ times in $2n$ continuous timeslots. The width of the scan widow of the salve takes twice the width of the slot. In this way, every slave has the opportunity to get synchronized with the master at the end of the $2n$ slots even if one or more (not all) channels are disturbed. Then, the slaves can send their requests to the master in different slots so that the master can schedule subsequent communications according to their requests and priorities. Also, if the mater broadcasts the beacon periodically, the time length for a slave to join or rejoin the master is not difficult to predict. The theorems associated with the 1/ $2n$ FTS method are demonstrated in experiments with NORDIC Semiconductor chips.
... The approaches proposed in [20] and [34] are centralized and those proposed in [21] and [22] are distributed. The authors of [24,29,35] have studied the network association process. In [25], the authors have addressed the blind channel hopping problem. ...
Article
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Time Slotted Channel Hopping (TSCH) is one of the Medium Access Control methods proposed in the IEEE 802.15.4e standard to deal with the requirements of the industrial Wireless Sensor Networks (WSNs), especially in terms of high reliability and low latency. The key feature of the TSCH method is the combination between a time slotted access with a channel hopping, while considering both shared and dedicated links. The latter are essential for ensuring transmissions without loss and additional delays. Therefore, the objective we are seeking to reach in this paper is to demonstrate the benefit use of dedicated links on industrial WSNs-based 802.15.4e TSCH method. To this end, we propose an analytical model-based Markov chains for the TSCH method taking into account the dedicated links, and we estimate the transmission probability $$\tau$$ of a data packet. The latter will be then used to develop others analytical models, in order to derive a number of performance metrics, namely the average access delay, the reliability, the throughput, and the energy consumption. Furthermore, to validate the analytical model, we perform extensive simulations-based Monte-Carlo. Finally, to give credibility to the obtained simulation results, we compute $$95\%$$ confidence intervals. Numerical results show that increasing the number of dedicated links reduces significantly the retransmission probability offering best network performances in terms of average access delay, reliability and throughput.
Chapter
IETF IPv6 over the TSCH mode of IEEE 802.15.4e (6TiSCH) is an open communication protocol stack designed specifically for low-power wireless networks and aimed at being a key enabler technology of Industrial Internet of Things. 6TiSCH combines Time Slotted Channel Hopping (TSCH) with IPv6 to form a well-tuned and complete networking solution. In this paper, we study the parameters that affect the process of 6TiSCH network formation, such as the Enhanced Beacon transmission period, the scan period, the slotframe size, etc. We carry out extensive simulations to examine the impact of these parameters on the time of TSCH synchronization and the time of the formation of RPL Destination Oriented Graph. Results reveal that most of the studied variables affect greatly the 6TiSCH network formation time. This study allowed us to gain insights into how 6TiSCH networks behave during the bootstrapping phase, and how it is affected by different parameters.KeywordsIIoT6TiSCHTSCHNetwork formationIEEE 802.15.4
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Chapter
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Conference Paper
One of the most recent and reliable MAC protocols for low-rate wireless personal area networks is the IEEE802.15.4-TSCH. The formation of an IEEE802.15.4-TSCH network depends on the periodic transmission of Enhanced Beacons (EBs), and, by extension, on the scheduling of EB transmissions. In this paper, we present and analyze a negative phenomenon that can occur in most of the autonomous EB scheduling methods proposed in the literature. This phenomenon, which we call full collision, takes place when all the neighboring EB transmissions of a joining node collide. As a consequence, a node may not be able to join the network fast, consuming a considerable amount of energy as well. In order to eliminate collisions during EB transmissions, and, thus, to avoid the occurrence of this phenomenon, we propose a novel autonomous collision-free EB scheduling policy. The results of our simulations demonstrate the superiority of our policy compared to two other recently proposed policies.
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The Time-Slotted Channel Hopping (TSCH) mode of the standard IEEE~802.15.4 provides Medium Access Control (MAC) for most Low-power and Lossy Network (LLN) applications in the Internet of Things (IoT). TSCH creates a synchronized mesh network capable of delivering data packets in a reliable and timely manner. The standard defines a scan mechanism to allow nodes to detect the presence of a TSCH network and to associate to it. However, the time required to do so can be long, which causes excessive energy consumption, as nodes that are trying to associate stay awake during this process. In this paper, we present a rendezvous-based algorithm for TSCH association called PRV-TSCH that significantly reduces the time required for going through this process. The algorithm uses the principle of parallel rendezvous to allow nodes to associate to a TSCH network in a very short time. The interaction between the IPv6 Routing Protocol for LLNs (RPL) and the time to associate to the TSCH network is also studied. The results of extensive simulation experiments and a mathematical model demonstrate that PRV-TSCH outperforms the purely passive scan proposed by the standard in terms of the time and energy required to associate to a TSCH network.
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In this paper, we focus first on the time needed by a node to join a Time Slotted Channel Hopping (TSCH) network, this time is called joining time. Second, we are also interested in the network building time. Since the data generated by a sensor node remain unavailable as long as this node has not yet joined the wireless sensor network, these times are of prime importance for applications having strong latency requirements on data gathering. The joining time depends on the beacon advertising policy that has been left unspecified by the standard. The contribution of this paper is triple. First, we propose an Enhanced Deterministic Beacon Advertising algorithm, called EDBA, that ensures a collision-free advertising of beacons and minimizes the average joining time. Second, we model the behavior of a joining node by a Markov chain, validated by NS3 simulations, and compute the average joining time. Third, we compare the performance of EDBA with this of MBS, considered as the best beacon advertising algorithm in the literature.
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The industrial Internet of Things (IIoT) is expected to revolutionize the current industry. The capillary introduction of sensors and actuators for real-time monitoring and remote control and their seamless integration into existing information systems will represent a technological breakthrough. The definition of wireless communication standards will play a crucial role in reducing deployment costs and minimizing the time for installation. The new IPv6 over the TSCH mode of IEEE802.15.4e communication stack, 6TiSCH, represents the current leading standardization effort that aims at achieving both reliable and timed wireless communication and integration within IPv6 communication networks for industrial systems. In this paper, the network formation dynamics of 6TiSCH networks are assessed, considering the current guidelines for the so-called minimal configuration, a static initial configuration to guarantee control communication during network bootstrap. It is shown that the minimal configuration might lead to long network formation and suboptimal performance of the routing algorithm which may result into a disconnected network. In order to overcome this issue, a dynamic resource management algorithm to be executed during network bootstrap is proposed. Simulation and experimental results show that the proposed solution allows to minimize the network formation time and also helps in optimizing routing operations leading to the discovery of better routes.
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Time Slotted Channel Hopping (TSCH) Medium Access Control (MAC) is a key feature of the IEEE 802.15.4 standard, aimed at accommodating the requirements of industrial Internet of Things systems. Time Division Multiple Access (TDMA) is a main pillar of TSCH, on top of which frequency hopping is added to increase the resilience of short range radio links. A tight synchronization among the network nodes is required in TSCH. Luckily, once a node joins the network, several lean techniques can be used to keep alive its synchronization. On contrary, the subtleties of the joining phase in TSCH still deserve investigations since they could hinder an effective usage of the TSCH MAC. To this end, the problem of acquiring the first synchronization in a TSCH network is investigated hereby, from several perspectives: (i) four novel mechanisms are proposed and implemented in real motes to speed up joining operations; (ii) their average joining time is analytically modeled with closed form expressions as a function of node density, communication reliability, and beacon transmission frequency; (iii) their effectiveness and the agreement between experimental and theoretical outcomes are evaluated in several scenarios.
Conference Paper
Time Slotted Channel Hopping (TSCH) is one of main features of IEEE 802.15.4e standard designed for wireless sensor networks. It improves energy efficiency, network capacity and communication reliability in industrial applications. However, in the joining phase of TSCH network formation, sensor nodes have to remain awake status for a long time till they can reach synchronization. This is the reason which consumes a significant amount of energy. In this paper, we therefore propose a reliable lightweight joining scheme for TSCH network formation to speed up joining operation. The scheme is present in detail through analysis models as well as implementation result in real sensor nodes. Moreover, the comparison with other approaches is also mentioned to show the potential efficiency and better performance of our proposal.
Article
Time Slotted Channel Hopping (TSCH) is one of the access behavior modes defined in the IEEE 802.15.4e standard. It combines time slotted access with multi-channel and channel hopping capabilities, providing predictable latency, energy efficiency, high network capacity, and high communication reliability. In this paper we focus on the formation process of TSCH networks, which relies on the regular advertisement of Enhanced Beacons (EBs). We consider a simple random-based advertisement algorithm, and evaluate its performance, through analysis and simulation, in terms of joining time (i.e., total time taken by a new node to join the network). We found that the joining time depends on a number of factors and, mainly, on the number of channels used for EB advertisement.
Low-Rate Wireless Personal Area Networks Amendment 1: MAC Sublayer
IEEE, IEEE802.15.4e-2012: IEEE Standard for Local and Metropolitan Area Networks. Part 15.4: Low-Rate Wireless Personal Area Networks Amendment 1: MAC Sublayer. IEEE Std., April 2012.
Ieee standard for low-rate wireless networks
IEEE, "Ieee standard for low-rate wireless networks," IEEE Std 802.15.4-2015, pp. 1-709, 2016.
The trickle algorithm
• P Levis
• T Clausen
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P. Levis, T. Clausen, J. Hui, O. Gnawali, and J. Ko, "The trickle algorithm," Internet Engineering Task Force, RFC6206, 2011.