Time Synchronized Channel Hopping Research Articles

Minimal-Overlap Centrality for Multi-Gateway Designation in Real-Time TSCH Networks

This article presents a novel centrality-driven gateway designation framework for the improved real-time performance of low-power wireless sensor networks (WSNs) at system design time. We target time-synchronized channel hopping (TSCH) WSNs with centralized network management and multiple gateways with the objective of enhancing traffic schedulability by design . To this aim, we propose a novel network centrality metric termed minimal-overlap centrality that characterizes the overall number of path overlaps between all the active flows in the network when a given node is selected as gateway. The metric is used as a gateway designation criterion to elect as a gateway the node leading to the minimal number of overlaps. The method is then extended to multiple gateways with the aid of the unsupervised learning method of spectral clustering . Concretely, after a given number of clusters are identified, we use the new metric at each cluster to designate as cluster gateway the node with the least overall number of overlaps. Extensive simulations with random topologies under centralized earliest-deadline-first (EDF) scheduling and shortest-path routing suggest our approach is dominant over traditional centrality metrics from social network analysis, namely, eigenvector , closeness , betweenness , and degree . Notably, our approach reduces by up to 40% the worst-case end-to-end deadline misses achieved by classical centrality-driven gateway designation methods.

Multigateway Designation for Real-Time TSCH Networks Using Spectral Clustering and Centrality

This letter proposes a multi-gateway designation framework to design real-time wireless sensor networks (WSNs) improving traffic schedulability, i.e., meeting the traffic time constraints. To this end, we resort to Spectral Clustering unsupervised learning that allows defining arbitrary k disjoint clusters without knowledge of the nodes physical position. In each cluster we use a centrality metric from social sciences to designate one gateway. This novel combination is applied to a time-synchronized channel-hopping (TSCH) WSN under earliest-deadline-first (EDF) scheduling and shortest-path routing. Simulation results under varying configurations show that our framework is able to produce WSN designs that greatly reduce the worst-case network demand. In a situation with 5 gateways, 99% schedulability can be achieved with 3.5 times more real-time flows than in a random benchmark.

Design of High-Performance Intelligent WSN based-IoT using Time Synchronized Channel Hopping and Spatial Correlation Model

Wireless Sensor Network (WSN) is one of the most significant contributors to the Internet of Things (IoT), and it plays a significant role in the lives of individuals. There are three main problems in the design of traditional WSN based-IoT. First problem about data; the WSN transmits a huge volume of data to the IoT for processing. The second problem is the energy; since sensor nodes rely on their limited battery, conserving energy is crucial, and the third problem about efficiency of transmission. This paper presents new WSN based IoT framework that integrate important techniques to solve these problems; To increase the effectiveness of data processing and storing, the intelligent Adaptive Boosting stochastic algorithm is applied. IEEE 802.15.4e time slotted channel hopping (TSCH) protocol is used because it has the benefits such as collision-free transmission and multi-hop transmission. Data reduction at the Gateway (GW) level of the network is achieved through spatial correlation between sensors with the goal of conserving energy. Principle idea of this new framework is to identify the advantages of integrating the important techniques; intelligent Adaptive Boosting Stochastic diffusion search algorithm, TSCH, and Special correlation model. As a result, the proposed framework can thereby satisfy the need for a long battery life of low-rate applications and at the same time, the need for high throughput for high-rate uses also for testing it in achieved efficient classification of data, the important performance measures are used.

A Latin rectangles-based TSCH scheduling and interference mitigation design

The Industrial Internet of Things (IIoT) connects a large number of industrial objects to the Internet that requires a higher level of control in terms of reliability, low power, and delay. IEEE 802.15.4e is the standard of the IIoT and includes time-synchronized channel hopping mechanisms to allow multiple communications. It controls the medium access operations using a time–frequency schedule. However, TSCH (Time Slotted Channel Hopping) specification does not specify how to build an optimized schedule. In this paper, we propose a distributed channel hopping scheme by providing an analytical model for the exploitation of Latin rectangles to avoid interference and collisions. Indeed, Latin rectangles are used to perform the scheduling process, where rows present the channel offsets and columns for slot offsets. Thus, the frequency of communication is derived using Latin rectangles, which prevents the scheduling function of nodes from considering channels already allocated in their neighborhood. Consequently, interference and multi-path fading are mitigated with more reliability and robustness. Markov chain model for the queue on every node is introduced and takes the bulk arrivals and the slot distribution into account. We analyze the efficiency of this algorithm by analytical techniques and extensive simulations for three bulk arrivals: Poisson, Bernoulli, and Geometric.

Cracking Channel Hopping Sequences and Graph Routes in Industrial TSCH Networks

Industrial networks typically connect hundreds or thousands of sensors and actuators in industrial facilities, such as manufacturing plants, steel mills, and oil refineries. Although the typical industrial Internet of Things (IoT) applications operate at low data rates, they pose unique challenges because of their critical demands for reliable and real-time communication in harsh industrial environments. IEEE 802.15.4-based wireless sensor-actuator networks (WSANs) technology is appealing for use to construct industrial networks because it does not require wired infrastructure and can be manufactured inexpensively. Battery-powered wireless modules easily and inexpensively retrofit existing sensors and actuators in industrial facilities without running cables for communication and power. To address the stringent real-time and reliability requirements, WSANs made a set of unique design choices such as employing the Time-Synchronized Channel Hopping (TSCH) technology. These designs distinguish WSANs from traditional wireless sensor networks (WSNs) that require only best effort services. The function-based channel hopping used in TSCH simplifies the network operations at the cost of security. Our study shows that an attacker can reverse engineer the channel hopping sequences and graph routes by silently observing the transmission activities and put the network in danger of selective jamming attacks. The cracked knowledge on the channel hopping sequences and graph routes is an important prerequisite for launching selective jamming attacks to TSCH networks. To our knowledge, this article represents the first systematic study that investigates the security vulnerability of TSCH channel hopping and graph routing under realistic settings. In this article, we demonstrate the cracking process, present two case studies using publicly accessible implementations (developed for Orchestra and WirelessHART), and provide a set of insights.

Energy Savvy Network Joining Strategies for Energy Harvesting Powered TSCH Nodes

This article presents methods that enable batteryless energy harvesting powered time-synchronized channel hopping (TSCH) wireless sensor nodes to join a network with less energy wastage. Network joining of TSCH nodes is very power hungry yet inevitable process to form a working wireless sensor network (WSN). Since the energy level from energy harvesting is scarce, energy passive methods are essential. A duty-cycled network joining process in combination with an appropriate capacitor size is proposed here as they are among the factors that can be easily controlled without extra energy. When a node joins the network in a duty-cycled manner, other nodes may join the network during the gap time, which reduces energy wastage of the nodes in waiting. With an appropriate capacitor size, the capacitor can be charged up within a reasonable time and power up the node for a sufficiently long time, which increases the probability to complete the network joining process of the node. With the combination of a join duty cycle of 50% with a 100-mF capacitor, a WSN was successfully formed by two energy harvesting powered wireless sensor nodes in one network joining attempt.

TLS-VaD: A New Tool for Developing Centralized Link-Scheduling Algorithms on the IEEE802.15.4e TSCH Network

A simulator plays an important role in network protocol research, as it enables researchers to develop protocols more flexibly. Many simulators have been developed to support research in this field, including NS-2, NS-3, OPNET, OMNeT, and Cooja. Although, as a research support tools, NS3 and Cooja have already been equipped with an Internet of things (IoT) module, their support for research on IoT centralized scheduling is still limited. Therefore, this study is aimed to develop a tool for IoT centralized scheduling research, where the IoT technology is based on the IEEE802.15.4e time synchronized channel hopping (TSCH) standard. The tool is called the TSCH Link-Scheduling visualization and data processing (TLS-VaD). The results of validity tests show that TLS-VaD works well; therefore, this tool can be used in the performance measurement of centralized scheduling algorithms on TSCH networks. As an example of the application, this research used TLS-VaD to test the performance of three scheduling algorithms: Iman Ramli Bursty Transmission Scheduling Algorithm (IRByTSA), first top scheduling algorithm (FTSA), and first leaf scheduling algorithm (FLSA). The test results using TLS-VaD shows that IRByTSA had better performance compared to FLSA and FTSA, because it saved more power and was able to generate scheduling decisions relatively quickly.

<italic>DeAMON</italic>: A Decentralized Adaptive Multi-Hop Scheduling Protocol for 6TiSCH Wireless Networks

The IEEE 802.15.4-2015 standard provides a link-layer mechanism, based on time synchronized channel hopping (TSCH), to enable deterministic low-power wireless mesh networking. The emerging IPv6 over IEEE 802.15.4e TSCH (6TiSCH) working group aims at harmonizing an IP-enabled protocol stack with the IEEE 802.15.4e link layer. In 802.15.4-TSCH medium access control, nodes follow a communication schedule; however, the standard does not specify any scheduling policy. Therefore, a number of recent studies have investigated scheduling mechanisms for 6TiSCH wireless networks. This paper introduces DeAMON , which is decentralized adaptive multi-hop scheduling protocol for 6TiSCH wireless networks. The key features of DeAMON include traffic-awareness, sequential scheduling, parallel transmissions, robust over-provisioning, and adaptability to topology changes. Moreover, DeAMON incurs minimal signaling overhead. Performance evaluation demonstrates that DeAMON outperforms state-of-the-art distributed scheduling protocols in terms of reliability, latency, and resource utilization.

MABO‐TSCH: Multihop and blacklist‐based optimized time synchronized channel hopping

AbstractEmerging Industrial Internet of Things applications, such as smart factories, require reliable communication and robustness against interference from colocated wireless systems. To address these challenges, frequency‐hopping spread spectrum has been used by different protocols, including IEEE802.15.4‐2015 TSCH. Frequency‐hopping spread spectrum can be improved with the aid of blacklists to avoid bad frequencies. The quality of channels in most environments shows significant spatial‐temporal variation, which limits the effectiveness of simple blacklisting schemes. In this article, we propose an enhanced blacklisting solution to improve the TSCH protocol. The proposed algorithms work in a distributed fashion, where each pair of receiver/transmitter nodes negotiates a local blacklist, based on the estimation of packet delivery ratio. We model the channel quality estimation as a multiarmed bandit problem and show that it is possible to create blacklists that provide results close to optimal without any separate learning phase. The proposed algorithms are implemented in OpenWSN and evaluated through simulations in 2 different scenarios with about 40 motes and experiments using an indoor testbed with 40 TelosB motes.

A Wireless Cloud Network Platform for Industrial Process Automation: Critical Data Publishing and Distributed Sensing

Wireless technologies combined with advanced computing are changing industrial communications. Industrial wireless networks can improve the monitoring and the control of the entire system by jointly exploiting massively interacting communication and distributed computing paradigms. In this paper, we develop a wireless cloud platform for supporting critical data publishing and distributed sensing of the surrounding environment. The cloud system is designed as a self-contained network that interacts with devices exploiting the time synchronized channel hopping protocol (TSCH), supported by WirelessHART (IEC 62591). The cloud platform augments industry-standard networking functions as it handles the delivery (or publishing) of latency and throughput-critical data by implementing a cooperative-multihop forwarding scheme. In addition, it supports distributed sensing functions through consensus-based algorithms. Experimental activities are presented to show the feasibility of the approach in two real industrial plant sites representative of typical indoor and outdoor environments. Validation of cooperative forwarding schemes shows substantial improvements compared with standard industrial solutions. Distributed sensing functions are developed to enable the autonomous identification of recurring cochannel interference patterns.

Simple Distributed Scheduling With Collision Detection in TSCH Networks

The IETF IPv6 over the time synchronized channel hopping mode of IEEE 802.15.4e (6TiSCH) working group standardizes a distributed mechanism for neighbor motes to agree on a schedule to communicate, driven by a scheduling function. This letter introduces the notion of housekeeping to the schedule function, in which motes relocate cells in the schedule to build a collision-free schedule in a distribute manner. The solution, based on detecting underperforming cells and listening for unexpected packets, does not require additional signaling traffic or state. This letter shows that simple housekeeping rules introduced allow a network to contain 17% more motes and suffer from 64% fewer collision, while maintaining end-to-end reliability above 99.5% in a typical industrial environment. This solution is now being discussed for standardization at 6TiSCH.

Distributed PID-Based Scheduling for 6TiSCH Networks

Industrial low-power networks are becoming the nexus of operational technologies and the Internet thanks to the standardization of networking layer interfaces. One of the main promoters of this shift is the IETF 6TiSCH WG, which addresses network management and IP integration of time synchronized channel hopping (TSCH) networks as those developed by the IEEE802.15.4 TG. The 6TiSCH WG is defining the operational interface and mechanism by which the network schedule can be distributed amongst the devices in the network. This operational sublayer, called 6top, supports distributed scheduling and enables implementers to define the scheduling policy, only standardizing the distribution mechanism. This letter proposes a novel distributed scheduling policy based on the well-known industrial control paradigm referred as proportional, integral, and derivative (PID) control. The proposed technique is completely decentralized, enabling each node to determine the number of cells to schedule to one another, according to its traffic demand. The mechanism is reactive to sudden or bursty traffic patterns, while staying conservative in over-provisioning cells.

Decentralized Time-Synchronized Channel Swapping for Ad Hoc Wireless Networks

Time-synchronized channel hopping (TSCH) is currently the most efficient solution for collision-free interference-avoiding communications in ad hoc wireless networks, such as wireless sensor networks, vehicular networks, and networks of robots or drones. However, all variants of TSCH require some form of centralized coordination to maintain the time–frequency slotting mechanism. This leads to slow convergence to steady state and moderate time–frequency slot utilization, particularly under node churn or mobility. We propose decentralized time-synchronized channel swapping (DT-SCS), which is a novel protocol for medium access control (MAC) in ad hoc wireless networks. Under the proposed protocol, nodes first converge to synchronous beacon packet transmissions across all available channels at the physical layer, with a balanced number of nodes in each channel. This is done by the novel coupling of distributed synchronization and desynchronization mechanisms —which are based on the concept of pulse-coupled oscillators—at the MAC layer. Decentralized channel swapping can then take place via peer-to-peer swap requests/acknowledgments made between concurrent transmitters in neighboring channels. We benchmark the convergence and network throughput of DT-SCS, TSCH, and the efficient multichannel MAC protocol (seen as the state of the art in decentralized, interference-avoiding, and multichannel MAC protocols) under simulated packet losses at the MAC layer. Moreover, performance results via a Contiki-based deployment on TelosB motes reveal that DT-SCS comprises an excellent candidate for decentralized multichannel MAC-layer coordination by providing for quick convergence to steady state, high bandwidth utilization under interference and hidden nodes, as well as high connectivity.

Fast Desynchronization for Decentralized Multichannel Medium Access Control

Distributed desynchronization algorithms are key to wireless sensor networks as they allow for medium access control in a decentralized manner. In this paper, we view desynchronization primitives as iterative methods that solve optimization problems. In particular, by formalizing a well established desynchronization algorithm as a gradient descent method, we establish novel upper bounds on the number of iterations required to reach convergence. Moreover, by using Nesterov's accelerated gradient method, we propose a novel desynchronization primitive that provides for faster convergence to the steady state. Importantly, we propose a novel algorithm that leads to decentralized time-synchronous multichannel TDMA coordination by formulating this task as an optimization problem. Our simulations and experiments on a densely-connected IEEE 802.15.4-based wireless sensor network demonstrate that our scheme provides for faster convergence to the steady state, robustness to hidden nodes, higher network throughput and comparable power dissipation with respect to the recently standardized IEEE 802.15.4e-2012 time-synchronized channel hopping (TSCH) scheme.

OpenWSN: a standards‐based low‐power wireless development environment

ABSTRACTThe OpenWSN project is an open‐source implementation of a fully standards‐based protocol stack for capillary networks, rooted in the new IEEE802.15.4e Time Synchronized Channel Hopping standard. IEEE802.15.4e, coupled with Internet of Things standards, such as 6LoWPAN, RPL and CoAP, enables ultra‐low‐power and highly reliable mesh networks, which are fully integrated into the Internet. The resulting protocol stack will be cornerstone to the upcoming machine‐to‐machine revolution.This article gives an overview of the protocol stack, as well as key integration details and the platforms and tools developed around it. The pure‐C OpenWSN stack was ported to four off‐the‐shelf platforms representative of hardware currently used, from older 16‐bit microcontroller to state‐of‐the‐art 32‐bit Cortex‐M architectures. The tools developed around the low‐power mesh networks include visualisation and debugging software, a simulator to mimic OpenWSN networks on a PC, and the environment needed to connect those networks to the Internet.Experimental results presented in this article include a network where motes operate at an average radio duty cycle well below 0.1% and an average current draw of 68 μA on off‐the‐shelf hardware. These ultra‐low‐power requirements enable a range of applications, with motes perpetually powered by micro‐scavenging devices. OpenWSN is, to the best of our knowledge, the first open‐source implementation of the IEEE802.15.4e standard. Copyright © 2012 John Wiley & Sons, Ltd.

A decentralized scheduling algorithm for time synchronized channel hopping

Time Synchronized Channel Hopping (TSCH) is an existing Medium Access Control scheme which enables robust communication through channel hopping and high data rates through synchronization. It is based on a time-slotted architecture, and its correct functioning depends on a schedule which is typicall