Time Slotted Channel Hopping Protocol Research Articles

An enhanced MSU‐TSCH scheduling algorithms for industrial wireless sensor networks

SummaryThe reliability and latency requirements of wireless sensor network‐based smart grid communications are met in large part by MAC protocols. Developed by IEEE, time slotted channel hopping (TSCH), a method that is effective, dependable, and predictable. However, the TSCH standard does not enable mobility and does not offer any solution for scheduling, especially in IEEE 802.15.4 TSCH, the most recent generation of extremely dependable and low‐power MAC protocols. Recently, MSU‐TSCH a time‐frequency communication schedule was proposed to provide mobility to TSCH. Despite its distinctive qualities, MSU‐TSCH has the drawback of computing the TSCH schedule at each node independently of its traffic load, which can significantly increase the communication delay. Due to this limitation, MSU‐TSCH is not suitable for some delay‐sensitive smart grid applications. In this article, we provide an improved MSU‐TSCH‐based TSCH protocol, called Mobility‐TSCH, that dynamically adjusts time slot assignments based on traffic volume and latency requirement. Moreover, the protocol Mobility‐TSCH adapts to topology changes and supports mobility. Additionally, it optimizes time slot allocation by prioritizing nodes closest to the sink. The performance and evaluation analysis of Mobility‐TSCH compared to the original MSU‐TSCH, reveal that the communication delay is greatly reduced, decreases the average end‐to‐end latency, the high packet delivery ratio (PDR), Increase the performance of both metrics, parent connectivity ratio (PCR) and convergence time (CT), while maintaining a minimal overhead signaling.

A hardware accelerator for IEEE 802.15.4 Time-Slotted Channel Hopping transceiver

Time-Slotted Channel Hopping (TSCH), an operational mode of the IEEE 802.15.4e standard, imposes a high workload on the embedded processor, mainly due to its precise timing. The limited embedded processor of an edge device cannot satisfy the considerable memory footprint and computational complexity caused by functions that need precise timing in the protocol stack. Moving such duties to hardware seems to be a viable path towards offloading the processor and releasing its resource to be used for running firmware related to the implementation of the upper layers of the protocol stack as well as the application. In this work, a TSCH protocol hardware accelerator is designed and integrated within the digital baseband processor of an IEEE 802.15.4 transceiver. The whole system is implemented targeting the TSMC 65 nm technology. The designed TSCH accelerator has an efficient interface and is totally configurable by the software. It efficiently controls the transceiver, frees up embedded processor cycles, and reduces the interrupt callback to the processor. Therefore, the TSCH hardware accelerator makes it possible to use a cheaper embedded processor or to operate the processor on a lower clock speed which results in lower power consumption. The power analysis of the implemented system shows that, in the minimal setting of the TSCH accelerator, only 0.1% is added to the power consumption of the digital baseband processor. The power overhead increases to 5.6% for supporting three parallel slotframes which is a widely used TSCH setting in multi-hop networks. In return, the embedded processor is relaxed of processing TSCH timing related interrupts that are required for software-based TSCH implementation.

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.

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.

Design of a Wireless Sensor Network-Based IoT Platform for Wide Area and Heterogeneous Applications

Internet of Things (IoT) is not only a promising research topic but also a blooming industrial trend. Although the basic idea is to bring things or objects into the Internet, there are various approaches, because an IoT system is highly application oriented. This paper presents a wireless sensor network(WSN)-based IoT platform for wide area and heterogeneous sensing applications. The platform, consisting of one or multiple WSNs, gateways, a Web server, and a database, provides a reliable connection between sensors at fields and the database on the Internet. The WSN is built based on the IEEE 802.15.4e time slotted channel hopping protocol, because it has the benefits such as multi-hop transmission, collision-free transmission, and high energy efficiency. In addition to the design of a customized hardware for range extension, a new synchronization scheme and a burst transmission feature are also presented to boost the network capacity and reduce the energy waste. As a result, the proposed platform can fulfill the high throughput requirement for high-rate applications and the requirement of long battery life for low-rate applications at the same time. We have developed a testbed in our campus to validate the proposed system.

Autonomous and traffic-aware scheduling for TSCH networks

Wireless Sensor Networks (WSNs) have been recognized as a promising communication technology for smart grid monitoring and control applications. However, the deployment of WSNs in smart grid brought new challenges that pertain to the harsh electrical grid nature, and the different and often contradicting communication requirements of smart grid monitoring applications. MAC protocols play a crucial role to meet the reliability and latency requirements of WSN-based smart grid communications. In particular, the IEEE 802.15.4 TSCH (Time Slotted Channel Hopping), the latest generation of low-power and highly reliable MAC protocols, orchestrates the medium access according to a time-frequency communication schedule. However, TSCH specification does not provide any practical solution for the establishment of the schedule. Orchestra is a recent scheduling solution for TSCH that brings significant advantages such as, the use of simple scheduling rules, the low signaling overhead, and the high delivery ratio. Despite its unique features, Orchestra has the limitation of computing the TSCH schedule at each node independently from its traffic load, which can drastically affect the communication delay. This limitation makes Orchestra not sufficiently convenient for several delay-sensitive smart grid applications. Further, the current TSCH specification does not support traffic differentiation (i.e. handle all packets equally regardless of their criticality levels). In this paper, we propose an enhanced Orchestra-based TSCH protocol, called e-TSCH-Orch, that dynamically adjusts time slots assignment according to traffic load and criticality level. The performance analysis of e-TSCH-Orch shows that it significantly reduces the communication delay compared to the original Orchestra-based TSCH, while preserving the low signaling overhead and the high packet delivery ratio.

Dependable Interference-Aware Time-Slotted Channel Hopping for Wireless Sensor Networks

IEEE 802.15.4 Time-Slotted Channel Hopping (TSCH) aims to improve communication reliability in Wireless Sensor Networks (WSNs) by reducing the impact of the medium access contention, multipath fading, and blocking of wireless links. While TSCH outperforms single-channel communications, cross-technology interference on the license-free ISM bands may affect the performance of TSCH-based WSNs. For applications such as in-vehicle networks for which interference is dynamic over time, it leads to non-guaranteed reliability of the communications over time. This article proposes an Enhanced version of the TSCH protocol together with a Distributed Channel Sensing technique (ETSCH+DCS) that dynamically detects good quality channels to be used for communication. The quality of channels is extracted using a combination of a central and a distributed channel-quality estimation technique. The central technique uses Non-Intrusive Channel-quality Estimation (NICE) technique that proactively performs energy detections in the idle part of each timeslot at the coordinator of the network. NICE enables ETSCH to follow dynamic interference, while it does not reduce throughput of the network. The distributed channel quality estimation technique is executed by all the nodes in the network, based on their communication history, to detect interference sources that are hidden from the coordinator. We did two sets of lab experiments with controlled interferers and a number of simulations using real-world interference datasets to evaluate ETSCH. Experimental and simulation results show that ETSCH improves reliability of network communications, compared to basic TSCH and the state-of-the-art solution. In some experimental scenarios NICE itself has been able to increase the average packet reception ratio by 22% and shorten the length of burst packet losses by half, compared to the plain TSCH protocol. Further experiments show that DCS can reduce the effect of hidden interference (which is not detectable by NICE) on the packet reception ratio of the affected links by 50%.

A performance analysis of Orchestra scheduling for time‐slotted channel hopping networks

The IEEE 802.15.4 TSCH (Time Slotted Channel Hopping) represents the latest generation of low‐power and highly reliable medium‐access control (MAC) protocols. It orchestrates the medium access according to a time‐frequency communication schedule. However, TSCH specification does not provide any practical solution for the establishment of the schedule. Orchestra is a recent scheduling solution for TSCH that brings significant advantages such as, the use of simple scheduling rules, the low signaling overhead, and the high delivery ratio it is able to fulfill. In this paper, we investigate the use of TSCH protocol with Orchestra scheduling approach for the Internet of Things (IoT) applications. Performance analysis results demonstrate that despite its unique features, Orchestra may incur high end‐to‐end communication delay, especially when the traffic is not uniformly distributed in the network. This limitation makes Orchestra not sufficiently convenient for several delay‐sensitive IoT applications, such as smart grid applications.