Time Slotted Channel Hopping Research Articles

Fast Synchronization Scheme Using 2-Way Parallel Rendezvous in IEEE 802.15.4 TSCH.

The high level of robustness and reliability required in industrial environments can be achieved using time-slotted channel hopping (TSCH) medium access control (MAC) specified in institute of electrical and electronics engineers (IEEE) 802.15.4. Using frequency channel hopping in the existing TSCH network, a parallel rendezvous technique is used to exchange packets containing channel information before network synchronization, thereby facilitating fast network synchronization. In this study, we propose a distributed radio listening (DRL)–TSCH technique that uses a two-way transmission strategy based on the parallel rendezvous technique to divide the listening channel by sharing the channel information between nodes before synchronization. The performance evaluation was conducted using the OpenWSN stack, and the actual experiment was carried out by utilizing the OpenMote-cc2538 module. The time taken for synchronization and the number of rendezvous packets transmitted were measured in linear and mesh topologies, and the amount of energy used was evaluated. The performance results demonstrate a maximum average reduction in synchronization time of 67% and a reduction in energy consumption of 58% when compared to the performance results of other techniques.

Multi‐Source Time Synchronization in IEEE Std 802.15.4‐2015 TSCH Networks

IEEE std 802.15.4‐2015 Time Slotted Channel Hopping (TSCH) extends and replaces multiple proprietary industrial standards to support ultra‐reliable and ultra‐low power operation in Industrial Internet of Things. Under TSCH, all devices must remain continuously synchronized with their time source neighbor. To do so, the nodes either periodically exchange control packets or data packets to compensate for clock drift. However, single time source neighbor scheme endangers de‐synchronization in the wireless network. In this letter, we propose using multiple time source parents to improve the synchronization of the network.

The analysis of energy consumption in 6TiSCH network nodes working in sub-GHz band

The 6TiSCH communication stack enables IPv6 networking over the TSCH (Time Slotted Channel Hopping) mode of operation defined in IEEE 802.15.4. Lately, it becomes an attractive solution for Low power and Lossy Networks (LLNs), suitable for Industrial Internet of Things (IIoT) applications. This article introduces a credible energy consumption model for the 6TiSCH network nodes, operating in the 863-870 MHz band. It presents the analysis leading to the construction of the model as well as detailed verification through experimental measurements which showed 98% accuracy in determining power consumption for two different network topologies. The article includes reliable battery lifetime predictions for transit and leaf nodes along with other parametric study results.

TSCH for Long Range Low Data Rate Applications

The TSCH (Time Slotted Channel Hopping) protocol from the IEEE 802.15.4-2015 standard is known to be suitable for highly reliable applications in low-power networks of severely constrained wireless embedded devices. Most of the research on TSCH has focused on the 2.4 GHz frequency band. The present work extends the TSCH protocol to low data rate applications using the sub-GHz frequency bands for an increased link budget. We introduce multiple improvements on top of the standard TSCH, namely, a special schedule for the network’s root nodes and their direct neighbors, as well as the option to have multiple root nodes in a single TSCH network. Experimental results in a testbed and a real-world deployment show that after applying the improvements, the network meets application requirements and provides reliable and energy-efficient operation.

Coexistence Analysis of Multiple Asynchronous IEEE 802.15.4 TSCH-Based Networks

Low-power Wireless Sensor Networks (WSNs) play a key role in realization of the Internet-of-Things (IoT). Among others, Time Slotted Channel Hopping (TSCH) is a Medium Access Control (MAC) operational mode of the IEEE 802.15.4 standard developed for communications in short range IoT networks. TSCH provides high level reliability and predictability by its channel hopping mechanism and time division channel access nature. In many applications, a number of TSCH networks may coexist in the same neighborhood. Several vehicles close to one another, each including a TSCH network for its in-vehicle communications, serve as an example. Since such networks are running independent of one another, they are not expected to be synchronized in time, and they are not scheduled to operate in exclusive frequency channels. This may lead to inter-TSCH interferences deteriorating the reliability of the networks, which is an important requirement for many IoT applications. This paper analyzes the impact of multiple asynchronous TSCH networks on one another. An analytical model is developed that estimates the chance of such interferences, and the expectation of the number of affected TSCH channels when a number of them are in the vicinity of one another. The developed model is verified using extensive simulations and real-world experiments. Also, a scalable and fast multi-TSCH coexistence simulator is developed that is used to get insight about coexistence behaviors of any number of TSCH networks with various configurations.

SA-RPL: a scheduling-aware forwarding mechanism in RPL/TSCH-operated networks

Wireless sensor networks have shown to be a promising technology for industrial automation in which continuous monitoring is a critical requirement. Deploying an energy-aware sensor network permits increasing the network lifetime and prolonging the monitoring operation. IEEE 802.15.4e and RPL have been used as de-facto protocols at the access and network layer in low power and low-rate wireless networks. Specifically, the time slotted channel hopping (TSCH) of 802.15.4e has been designed to provide a reliable access method in low power and lossy networks. More importantly, the combination of TSCH and RPL facilitates providing load-balancing together with energy-saving in such networks. This paper proposes schedule aware RPL (SA-RPL) which aims at prolonging the network lifetime while improving load balancing. It periodically collects scheduling matrix information form TSCH to compute a new measure for selecting the next hop at the network layer. More precisely, the parent with minimum number of occupied cells is more likely to be chosen as the preferred parent. To evaluate the performance of SA-RPL, we modified a distributed management scheme already developed in NS2 simulator. Simulation results show that SA-RPL, compared with other methods, prolongs the network lifetime up to two times and achieves a more uniform energy consumption distribution without decreasing other performance metrics.

Priority Based Centralized Scheduling for Time Slotted Channel Hopping Based Multihop IEEE 802.15.4 Networks

To meet the growing demands of low power and determinism in Industrial Wireless applications, IEEE defined IEEE 802.15.4e amendment that includes many channel access methods. Time Slotted Channel Hopping protocol is one of the most popular MAC protocols under IEEE 802.15.4e. However, scheduling of time slots for time slotted channel hopping, was not part of the protocol and so different scheduling algorithms were proposed by researchers. A new time slotted channel hopping scheduling mechanism that considers priorities to meet the time critical industrial applications is proposed in this work. Latency improvements of about 40 percentage are obtained here, for slot allocations to higher priority devices, when compared with the conventional queuing methods.

Optimizing the Lifetime of IoT-Based Star and Mesh Networks

In this paper, we propose and analyze a novel optimization model to maximize the lifetime of Internet-of-Things (IoT) networks, including the Low Power Wide-Area Network (LPWAN) based Sigfox star networks and Time Slotted Channel Hopping (TSCH) mesh networks. An IoT cloud manages the IoT network adapting to sensed phenomenon changes in the deployment area retrieved from peered cloud-based environmental monitoring systems. While increasing the number of paths for IoT devices to cloud communication increases reliability, it also comes at the expense of increased energy consumption. We consider an optimization problem to determine the best redundancy level to be applied in the IoT network such that the lifetime is maximized while achieving the quality-of-service (QoS) requirements in the presence of unreliable sensing environments. Our model is generic and easily adaptable to a given IoT technology by considering the technology’s devices, environmental, and protocol specifications while spanning single-hop, multi-hop, short-range, and long-range IoT technologies. We formulate the tradeoff between energy conservation vs. reliability of an IoT network as an Integer Non-Linear Programming (INLP) optimization problem. The feasibility of our approach in maximizing the lifetime of IoT networks for both the star and mesh network topologies is demonstrated using SigFox and TSCH as representative technologies, respectively. We conduct an extensive comparative performance analysis demonstrating that our model outperforms contemporary baseline models in both SigFox and TSCH IoT network technologies.

Wireless Sensor Networks and TSCH: A Compromise Between Reliability, Power Consumption, and Latency

Reliability, power consumption, and latency are the three main performance indicators of wireless sensor networks. Time slotted channel hopping (TSCH) is a promising technique introduced in the IEEE 802.15.4 standard that performs some steps ahead in the direction of the final dream to meet all the previous requirements at the same time. In this article, a simple and effective mathematical model is presented for TSCH that, starting from measurements performed on a real testbed, permits to characterize both the network and the surrounding environment. To better characterize power consumption, an experimental measurement campaign was purposely performed on OpenMote B devices. The model, which was checked against a real 6TiSCH implementation, can be employed to predict network behaviour when configuration parameters are varied, in such a way to satisfy different application contexts. Results show that, when one of the three above indices is privileged, unavoidably there is a worsening of the others.

Impact of interference free frequency channels on optimum time slot allocation for priority-based TSCH MAC

Time slotted channel hopping (TSCH), the most promising MAC protocol under IEEE 802.15.4 is meeting the growing demands of low power and determinism in time critical industrial wireless applications. An efficient duty cycle is a necessary mandate for time critical applications which can be achieved by an appropriate reduction of active time slots in the slot frame and this saves node power. Even though many attempts were done in realising an optimum scheduling protocol, the impact of the number of channels on the optimum time slot allocation is not yet considered which signifies importance with the present scenario of many channels being induced by interference from neighbouring wireless networks. Optimum time slot is essential for making efficient duty cycle. Hence, a study on the impact of the number of channels on the optimum time slot allocation is necessitated and is accomplished in this paper. It is found that increasing the number of channels beyond a certain value does not have an impact on the optimum slot allocation and there is a direct relationship between the number of channels and the number of links per track and number of root node branches.

Industrial internet of things over IEEE 802.15.4 TSCH networks: design and challenges

Using the internet of things technologies in manufacturing provides a promising opportunity to build powerful industrial systems and applications. The quest for mobility, flexibility, and low-energy consumption has created a strong push toward using low-power wireless solutions to enable the industrial internet of things (IIoT). This paper presents a survey of the emerging research concerning IIoT with a focus on the most promising solutions. It, first, outlines the main requirements to be addressed in order to build a powerful IIoT system. The paper, then, presents an overview accompanied by a comparative study of the most prevalent IIoT communication technologies. The study reveals the potential of the IEEE 802.15.4 standard with its time slotted channel hopping (TSCH) mode to lead the way through the IIoT, thanks to its latency, reliability and low-power characteristics along with the support of multi-hop communications. Based on this outcome, the paper provides an in-depth look at TSCH mechanisms and outlines the most challenging issues. Finally, the paper concludes the need to propose new solutions addressing such issues in order to make successful IIoT systems.

SA-RPL: a scheduling-aware forwarding mechanism in RPL/TSCH-operated networks

Wireless sensor networks have shown to be a promising technology for industrial automation in which continuous monitoring is a critical requirement. Deploying an energy-aware sensor network permits increasing the network lifetime and prolonging the monitoring operation. IEEE 802.15.4e and RPL have been used as de-facto protocols at the access and network layer in low power and low-rate wireless networks. Specifically, the time slotted channel hopping (TSCH) of 802.15.4e has been designed to provide a reliable access method in low power and lossy networks. More importantly, the combination of TSCH and RPL facilitates providing load-balancing together with energy-saving in such networks. This paper proposes schedule aware RPL (SA-RPL) which aims at prolonging the network lifetime while improving load balancing. It periodically collects scheduling matrix information form TSCH to compute a new measure for selecting the next hop at the network layer. More precisely, the parent with minimum number of occupied cells is more likely to be chosen as the preferred parent. To evaluate the performance of SA-RPL, we modified a distributed management scheme already developed in NS2 simulator. Simulation results show that SA-RPL, compared with other methods, prolongs the network lifetime up to two times and achieves a more uniform energy consumption distribution without decreasing other performance metrics.

Industrial internet of things over IEEE 802.15.4 TSCH networks: design and challenges

Using the internet of things technologies in manufacturing provides a promising opportunity to build powerful industrial systems and applications. The quest for mobility, flexibility, and low-energy consumption has created a strong push toward using low-power wireless solutions to enable the industrial internet of things (IIoT). This paper presents a survey of the emerging research concerning IIoT with a focus on the most promising solutions. It, first, outlines the main requirements to be addressed in order to build a powerful IIoT system. The paper, then, presents an overview accompanied by a comparative study of the most prevalent IIoT communication technologies. The study reveals the potential of the IEEE 802.15.4 standard with its time slotted channel hopping (TSCH) mode to lead the way through the IIoT, thanks to its latency, reliability and low-power characteristics along with the support of multi-hop communications. Based on this outcome, the paper provides an in-depth look at TSCH mechanisms and outlines the most challenging issues. Finally, the paper concludes the need to propose new solutions addressing such issues in order to make successful IIoT systems.

An Empirical Survey of Autonomous Scheduling Methods for TSCH

Time Slotted Channel Hopping (TSCH) is a link layer protocol defined in the IEEE 802.15.4 standard. Although it is designed to provide highly reliable and efficient service targeting industrial automation systems, scheduling TSCH transmissions in the time and frequency dimensions is left to the implementers. We evaluate the performance of existing autonomous scheduling approaches for TSCH on various traffic patterns and network configurations. We thoroughly investigate the pros and cons of each scheme; moreover, we propose the use of node based channel allocation to improve the performance of the best scheme, and demonstrate its practicality and reliability, with up to 6 percentage points better packet delivery ratio than the second best option while retaining a similar radio duty cycle. Finally, based on our extensive performance evaluation, we provide some guidelines on how to select a scheduler for a given network.

Enhanced 6P Transaction Methods for Industrial 6TiSCH Wireless Networks

IEEE802.15.4 time-slotted channel hopping (TSCH) is designed to provide reliability even in harsh wireless networks compromised by metal structures and external noise. TSCH provides reliability through coordinated communication based on link schedule however, no policies regarding this are defined by the IEEE802.15.4 standard. 6TiSCH (IPv6 over the TSCH mode of IEEE802.15.4e) provides management policies and link schedule negotiation mechanism that are not defined in the standard, and many studies are based on it. However, in most link-scheduling studies, 6top protocol (6P) for link schedule negotiation remains a premise, and the effect of harsh networks on 6P is rarely considered. Experimental results demonstrate that the performance of 6P is degraded due to the loss of 6P packets and transaction errors. These problems can threaten the fundamentals of existing link-scheduling studies. The main disadvantage of 6P in heavy traffic low-power and lossy networks (LLN)s is that nodes indiscriminately generate 6P requests according to their own demand. In this study, we analyze the performance and problems of 6P in harsh networks and propose parent-initiated 6P transaction and transaction revert methods to overcome such problems. The proposed methods enable stable cell negotiation even in LLNs under heavy traffic load through coordinated transactions of a parent based on the cell requirement of a child. The proposed methods are implemented using OpenWSN, an open-source project that implements the 6TiSCH IoT network stack, and its performance is evaluated through extensive experimentation. The results reveal that the proposed methods improve the success rate of 6P transactions and PDR of data packets by over 100% and 22%, respectively.

Multi-Agent Reinforcement-Learning-Based Time-Slotted Channel Hopping Medium Access Control Scheduling Scheme

Time-slotted channel hopping (TSCH) is a medium access control technology that realizes collision-free wireless network communication by coordinating the media access time and channel of network devices. Although existing TSCH schedulers have suitable application scenarios for each, they are less versatile. Scheduling without collisions inevitably lowers the throughput, whereas contention-based scheduling achieves high-throughput but it may induces to frequent collisions in densely deployed networks. Therefore, a TSCH scheduler that can be used universally, regardless of the topology and data collection characteristics of the application scenario, is required to overcome these shortcomings. To this end, a multi-agent reinforcement learning (RL)-based TSCH scheduling scheme that allows contention but minimizes collisions is proposed in this study. RL is a machine-learning method that gradually improves actions to solve problems. One specific RL method, Q-Learning (QL), was used in the scheme to enable the TSCH scheduler to become a QL agent that learns the best transmission slot. To improve the QL performance, reward functions tailored for the TSCH scheduler were developed. Because the QL agent runs on multiple nodes concurrently, changes in the TSCH schedule of one node also affect the performance of the TSCH schedules of other nodes. The use of action peeking is proposed to overcome this non-stationarity problem in a multi-agent environment. The experimental results indicate that the TSCH scheduler consistently performs well in various types of applications, compared to other schedulers.

A Performance-to-Cost Analysis of IEEE 802.15.4 MAC With 802.15.4e MAC Modes

The IEEE 802.15.4 standard is one of the widely adopted networking specification for Internet of Things (IoT). It defines several physical layer (PHY) options and medium access control (MAC) sub-layer protocols for interconnection of constrained wireless devices. These devices are usually battery-powered and need to support requirements like low-power consumption and low-data rates. The standard has been revised twice to incorporate new PHY layers and improvements learned from implementations. Research in this direction has been primarily centered around improving the energy consumption of devices. Recently, to meet specific Quality-of-Service (QoS) requirements of different industrial applications, the IEEE 802.15.4e amendment was released that focuses on improving reliability, robustness and latency. In this paper, we carry out a performance-to-cost analysis of Deterministic and Synchronous Multi-channel Extension (DSME) and Time-slotted Channel Hopping (TSCH) MAC modes of IEEE 802.15.4e with 802.15.4 MAC protocol to analyze the trade-off of choosing a particular MAC mode over others. The parameters considered for performance are throughput and latency, and the cost is quantified in terms of energy. A Markov model has been developed for TSCH MAC mode to compare its energy costs with 802.15.4 MAC. Finally, we present the applicability of different MAC modes to different application scenarios.

REA-6TiSCH: Reliable Emergency-Aware Communication Scheme for 6TiSCH Networks

From the perspective of the emerging Industrial Internet of Things (IIoT), the 6TiSCH working group has been created with the main goal to integrate the capabilities of the IEEE 802.15.4e time-slotted channel hopping (TSCH) with the IPv6 protocol stack. In order to support time-critical applications in IIoT, reliable real-time communication is a key requirement. Specifically, aperiodic critical traffic, such as emergency alarms, must be reliably delivered to the destination-oriented directed acyclic graph root within strict deadline bounds to avoid system failure or safety-critical situations. Currently, there is no mechanism defined in the 6TiSCH architecture for timely and reliably handling of such traffic and its prioritization over the noncritical one. In this article, we introduce REA-6TiSCH, a reliable emergency-aware communication scheme to support real-time communications of emergency alarms in 6TiSCH networks. In REA-6TiSCH, the aperiodic emergency traffic is opportunistically enabled to hijack transmission cells preassigned for the regular periodic traffic in the TSCH schedule. Moreover, we introduce a distributed optimization scheme to improve the probability that an emergency flow is delivered successfully within its deadline bound. To the best of our knowledge, this is the first approach to incorporate emergency alarms in 6TiSCH networks. We evaluate the performance of REA-6TiSCH through extensive simulations and the results show the effectiveness of our proposed method in handling emergency traffic compared to the Orchestra scheme. Additionally, we discuss the applicability of REA-6TiSCH and provide guidelines for real implementation in 6TiSCH networks.

Downward traffic retransmission mechanism for improving reliability in RPL environment supporting mobility

With the diversification of industrial Internet of Things applications, there is a growing demand for mobility support in industrial wireless networking environments. However, the routing protocol for low-power and lossy networks is designed based on a static environment and is vulnerable in a mobility environment. Routing protocol for low-power and lossy networks is an Internet engineering task force standard in the low-power and lossy network environments used mainly in industrial environments. In addition, although routing protocol for low-power and lossy networks is based on collection tree protocol and is suitable for data collection and upward traffic transmission, it struggles with downward traffic transmission in terms of control, actuation, and end-to-end transmission. In this article, the problems caused by mobile nodes in routing protocol for low-power and lossy networks are discussed, and a retransmission scheme named IM-RPL is proposed. This retransmission scheme can improve the performance of downward traffic for the mobile nodes by retransmitting the packets to the neighbor nodes, the mobile node’s new parent sets, and relaying them to the mobile node. Its performance is evaluated through an experiment. The results demonstrate that using OpenMote in OpenWSN’s time slotted channel hopping induces a packet reception ratio improvement and a lower transmission delay as compared to standard routing protocol for low power and lossy.

Adaptive Scheduling Design for Time Slotted Channel Hopping Enabled Mobile Adhoc Network

Industrial Internet of things (IIOT) applications comprises the wearable sensor devices for human activity monitoring; these devices generate the continuous data at higher data rate and it is powered through the battery. Hence, it restricts the uses of wireless protocol such as IEEE 802.15.4 and BLE (Bluetooth Low Energy). Moreover, there are promising technologies such as TSCH (Time Slotted Channel Hoping) MAC (Medium Access Control) which can be deployed in the different environment, which are prone to interference. In this research work we focus on overcoming the issue for designing the AS (Adaptive Scheduling) for TSCH – MANET (Mobile Adhoc Network); furthermore it is very difficult to design scheduling technique considering the unpredictable nature of data source location and wireless link, this results in waste of reserve resource. Moreover proposed Adaptive Scheduling model allows the both slots i.e. shared and dedicated slots, it also allows the communicating device to active the assigned slots adaptively. Hence, our proposed AS model achieves the higher overall access fairness, minimal idle listening overhead, higher packet deliver rate; further to cope up with the higher traffic load MANET device can activate the additional slots dynamically. Moreover, the outcome of Adaptive Scheduling model shows the higher data transmission and lower energy consumption.