TSCH Networks Research Articles

Low discrepancy on non-linear sensor deployment in a time-critical linear IIoT network

Linear networks are characterized by their long and narrow topology, which transmits data in a linear manner. For time-critical linear IIoT networks, stable connectivity is paramount. A good deployment strategy ensures stable connectivity in the network and maximize the lifetime and coverage of the network. In order to achieve this goal, deployment strategies should address tunnelling effects in linear networks. The proposed method tackles three major issues: 1. minimizing tunnelling effects using non-linear sensor deployment method, 2. maximizing network coverage by introducing a modified Latin Hypercube Sequence (LHS), and 3. Minimizing data interference in the multichannel TSCH network using a neighbour count-based sensor node deployment technique. The simulation validates the efficacy of the suggested approach in prolonging the network’s lifespan by mitigating the tunnelling effect near the sink. Moreover, it optimally utilizes over 70% of the mean energy within the network system. This is a significant improvement over previous algorithms which often failed to even utilizing 40% of the energy, and many a times much lesser. In terms of network coverage, it surpasses other algorithms. Consequently, the proposed method delivers economic advantages by extending the network’s longevity, achieved through a higher number of nodes concentrated around the sink, and significantly reduces the tunnelling effect in the network.

Enhanced Energy-Saving Mechanisms in TSCH Networks for the IIoT: The PRIL Approach

Lifetime of motes in wireless sensor networks can be enlarged by decreasing the energy spent for communication. Approaches like time slotted channel hopping pursue this goal by performing frame exchanges according to a predefined schedule, which helps reducing the duty cycle. Unfortunately, whenever the receiving radio interface is active but nobody in the network is transmitting, idle listening occurs. If the traffic pattern is known in advance, as in the relevant case of periodic sensing, proactive reduction of idle listening (PRIL) noticeably lowers energy waste by disabling receivers when no frames are expected for them. Optimal PRIL operation demands that, at any time, the transmitter and receiver sides of a link have a coherent view of its state (either enabled or disabled). However, this is not ensured in the presence of acknowledgment frame losses. This paper presents and analyzes some strategies to cope with such events. An extensive experimental campaign has been carried out through discrete event simulation to determine what consequences above errors may have from both a functional and performance viewpoint. Results show that, although no strategy is optimal in all circumstances, different solutions can be profitably adopted depending on the specific operating conditions.

Assessing the Effectiveness of Channel Hopping in IEEE 802.15.4 TSCH Networks

Assessing the Effectiveness of Channel Hopping in IEEE 802.15.4 TSCH Networks

Traffic-Aware Reliable Scheduling in TSCH Networks for Industry 4.0: A Systematic Mapping Review

Traffic-Aware Reliable Scheduling in TSCH Networks for Industry 4.0: A Systematic Mapping Review

Tsch-Varba – Dynamic Channel Allocation with Variable Bandwidth in Tsch Networks

Tsch-Varba – Dynamic Channel Allocation with Variable Bandwidth in Tsch Networks

Link-Based Autonomous Cell Scheduling for IEEE 802.15.4e TSCH With Improved Traffic Throughput

Low-power and lossy networks built in industrial environments may be required to handle large amounts of wireless communication traffic. The IEEE 802.15.4e TSCH MAC protocol (TSCH) is widely used in this environment. TSCH uses slotted time and channel hopping. In the TSCH network, a slotframe composed of a timeslot offset and channel offset operates repeatedly. Each node in the network operates according to the cells allocated in the slotframe, and the performance of the TSCH network is very different depending on the method of scheduling these cells. We propose an improved link-based autonomous cell scheduling scheme for TSCH, called IM-LAS, which makes the size of the slotframe different for each wireless link and activates a cell without additional communication overhead when there is a traffic request. In the experiment using hardware devices, IM-LAS showed better performance with up to 43% higher PDR and 67% lower latency than ALICE, and up to 83% higher PDR and 92% lower latency than Orchestra in high-traffic environments.

Software-Based Remote Network Attestation

Internet of Things (IoT) applications build upon resource-constrained, distributed devices that generate data and enable communication. For such applications to be truly trustworthy, it must be ensured that the devices are not compromised by malicious software. Remote attestation (RA), a prominent technique, exploits challenge-response protocols to detect malware on remote devices. Given the increasing scale and number of IoT deployments, recent work on RA has explored collective attestation of <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">swarms</i> of devices. However state-of-the-art swarm attestation techniques require trusted hardware which makes them inapplicable to both legacy and next generation IoT deployments without trusted hardware. We present SWARNA, a <italic xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">software-based</i> swarm attestation for IoT devices. After highlighting the challenges in designing such a solution, we present two protocol variants for IEEE 802.15.4 TSCH networks. We assess their performance analytically and empirically through testbed experiments. SWARNA maintains a constant payload size whereas, it increases linearly with the network size for existing solutions requiring trusted hardware. The two protocol variants attest 30 nodes networks, in 6s and 1.5s to 8.2s, respectively, depending on the number of malicious nodes. Further, we demonstrate that attestation traffic has a negligible impact on the packet delivery ratio (0.4 percent drop) of a typical data collection application.

Efficient Route Management Method for Mobile Nodes in 6TiSCH Network.

The combination of time slotted access and channel hopping technology in IEEE 802.15 TSCH networks enables high reliability and low power operation to meet the stability and real-time requirements of industrial applications. Basically, TSCH and RPL, a routing protocol for TSCH, are proposed for static nodes that generate fewer control messages, so they allow collisions in shared cells when they exchange control messages. In a topology containing mobile nodes, the collision of control messages in a shared cell makes the network difficult to recover quickly. The proposed scheme minimizes the collision of control messages by allocating dedicated control cells to form preferred parent nodes quickly for mobile nodes. We also proposed a method for establishing a fixed route from the root node to the mobile node in RPL to minimize the delay time. Through the simulation using the 6TiSCH simulator, it was confirmed that the performance of the proposed method was approximately 2.5 times better in terms of overhead and resource use, and 33% better in terms of network participation time of mobile nodes compared with existing solutions.

FAN: Fast and Active Network Formation in IEEE 802.15.4 TSCH Networks

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.

QuickCal: Assisted Calibration for Crystal-Free Micromotes

The single-chip micro mote (SC <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{M}$ </tex-math></inline-formula> ) is a crystal-free single-chip mote that brings us one step closer to the Smart Dust vision, in particular, as it can communicate with off-the-shelf IEEE802.15.4 and Bluetooth low energy devices. However, before it can be part of such networks, the crystal-free SC <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{M}$ </tex-math></inline-formula> chip needs to be able to accurately tune its communication frequency to synchronize to the network. This is a challenge since its onboard RC and LC-based resonating circuits have a drift rate that can be three orders of magnitude worse than crystal-based oscillators typically used in today’s radios. This article introduces QuickCal, a solution that allows an SC <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{M}$ </tex-math></inline-formula> chip to self-calibrate against off-the-shelf devices dedicated to assisting with its calibration. We show that an SC <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{M}$ </tex-math></inline-formula> chip can self-calibrate against this QuickCal Box in fewer than 3 min. We further validate that once it has self-calibrated, an SC <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{M}$ </tex-math></inline-formula> chip can reliably communicate with off-the-shelf IEEE802.15.4 devices. Finally, we demonstrate a heterogeneous network—composed of an SC <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\mu \text{M}$ </tex-math></inline-formula> chip and an OpenMote device—implementing a full 6TiSCH Industrial IoT protocol stack, which uses time synchronization and channel hopping. This is the first time that a crystal-free radio is participating in a channel-hopping-enabled TSCH network.

Beacon Optimization for Optimized Routing Model using Tsch Network

TSCH (Time-Slotted Channel Hopping) protocol is introduced recently by IETF 6TiSCH working group for achieving low energy consumption and highly reliable IEEE 802.15.4e. TSCH is a synchronous MAC (Medium Access Control) protocol with IPv6 enabling Internet of Things (Io T) that are deployed in environments that are prone to interference. However, the IEEE 802.15.4e only describes TSCH link-layer design without a study of communication scheduling and network formation for high density and rapid mobile ad hoc network (MANET) which are still an open issue to the research community. The exiting model incurs high latency and energy overhead for performing device association. To address aforementioned issues, this paper present an Adaptive Routing (AR) model for MANET using mobility enabled TSCH network. Our model reduces the overhead of mobile device within mobility enabled TSCH network by introducing a novel modified beaconing for achieving Adaptive Routing design. Experiment are conducted to evaluate performance of AR over existing approaches shows significant reduction of energy overhead and attain good packet routing outcomes.

TSCH Networks for Health IoT

The emerging Internet of Things has the potential to solve major societal challenges associated with healthcare provision. Low-power wireless protocols for residential Health Internet of Things applications are characterized by high reliability requirements, the need for energy-efficient operation, and the need to operate robustly in diverse environments in the presence of external interference. We enhance and experimentally evaluate the Time-Slotted Channel Hopping protocol from the IEEE 802.15.4 standard to address these challenges. Our contributions are a new schedule and an adaptive channel selection mechanism to increase the performance of time-slotted channel hopping in this domain. Evaluation in a test house shows that the enhanced system is suitable for our e-Health application and compares favorably with state-of-the-art options. The schedule provides higher reliability compared with the minimal scheduling function from the IETF 6TiSCH Working Group and has a better energy-efficiency/reliability tradeoff than the Orchestra scheduler. Results from 29 long-term residential deployments confirm the suitability for the application and show that the system is able to adapt and avoid channels used by WiFi. In these uncontrolled environments, the system achieves 99.96% average reliability for networks that generate 7.5 packets per second on average.

Service Migrations in TSCH Network using Wireless Channel Estimation and Prediction.

Service Migrations in TSCH Network using Wireless Channel Estimation and Prediction.

자율적인 TSCH 네트워크에서 충돌 회피를 위한 슬롯 재할당

IEEE 802.15.4e TSCH(Time Slotted Channel Hopping) 표준은 채널 호핑과 TDMA 방식을 사용하여 높은 안정성, 결정론적 지연과 효율적인 에너지 사용 등을 제공하나 표준 내 스케줄링 방법을 명시하지 않아, 이에 관한 연구가 활발하게 이루어졌다. Orchestra[6]는 최근 연구되고 있는 자율적인 스케줄링 방식 중 하나로 노드 간 협상과정이 필요하지 않아서 제어 메시지 교환으로 인한 오버헤드가 적다. 하지만, Orchestra는 슬롯프레임에서 노드당 하나의 슬롯만을 할당하기 때문에, 트래픽 부하가 높은 경우 성능이 크게 저하된다. 이에 대한 해결책으로 제안된 e-TSCH-Orch[7]는 임시 슬롯 할당을 통해 일시적으로 패킷 전달 속도를 증가시키지만, 트래픽 부하가 지속적으로 높은 경우에 대한 근본적인 해결책은 되지 못한다. 따라서 본 논문에서는 자율적으로 스케줄을 업데이트하는 알고리즘을 제안하여, Orchestra의 문제점을 해결하고 e-TSCH-Orch를 개선하고자 한다. 세 가지 성능 지표를 사용하여 기존의 Orchestra와 e-TSCH-Orch와 성능 비교를 진행하였고, 그 결과 제안하는 알고리즘이 기존 기술에 비해 저지연과 고신뢰성을 제공한다는 것이 검증되었다.

Optimal Number of Message Transmissions forProbabilistic Guarantee of Latency in the IoT.

The Internet of Things (IoT) is now experiencing its first phase of industrialization. Industrial companies are completing proofs of concept and many of them plan to invest in automation, flexibility and quality of production in their plants. Their use of a wireless network is conditioned upon its ability to meet three Key Performance Indicators (KPIs), namely a maximum acceptable end-to-end latency L, a targeted end-to-end reliability R and a minimum network lifetime T. The IoT network has to guarantee that at least of messages generated by sensor nodes are delivered to the sink with a latency ≤L, whereas the network lifetime is at least equal to T. In this paper, we show how to provide the targeted end-to-end reliability R by means of retransmissions to cope with the unreliability of wireless links. We present two methods to compute the maximum number of transmissions per message required to achieve R. is very easy to compute, whereas minimizes the total number of transmissions necessary for a message to reach the sink. and are then integrated into a TSCH network with a load-based scheduler to evaluate the three KPIs on a generic data-gathering application. We first consider a toy example with eight nodes where the maximum number of transmissions is tuned per link and per flow. Finally, a network of 50 nodes, representative of real network deployments, is evaluated assuming is fixed. For both TSCH networks, we show that provides a better reliability and a longer lifetime than , which provides a shorter average end-to-end latency. provides more predictable end-to-end performances than Kausa, a KPI-aware, state-of-the-art scheduler.

Scheduling for Data Transmission in Multi-Hop IEEE 802.15.4e TSCH Networks

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. TSCH is a trend used as the underlying architecture of the Internet of Things. However, IEEE 802.15.4e defines when the MAC executes a schedule but it does not specify how the schedule is built. This paper focuses on the problem of data transmission scheduling for TSCH network which uses the IEEE802 .15.4e TSCH as the MAC protocol. We adopt matching rule to resolve conflicts in the TSH network and matching scheduling algorithm(MSA) to solve the problem of communication resources allocation in tree topology. The scheduling algorithm MSA can avoid conflict, reduce the delay and energy consumption. OSA is proposed by further optimization of MSA. Through simulation experiments, the proposed method can effectively shorten the time delay, reduce the energy consumption and reduce the utilization rate of the channel.

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.

Link‐layer security in TSCH networks: effect on slot duration

AbstractThe IEEE802.15.4e‐2012 standard is widely used in multi‐hop wireless industrial Internet of things applications. In the time‐slotted channel hopping mode, nodes are synchronised, and time is cut into timeslots. A schedule orchestrates all communications, resulting in high reliability and low power operations. A timeslot must be long enough for a node to send a data frame to its neighbour, and for that neighbour to send back an acknowledgement. Shorter timeslots enable higher bandwidth and lower latency, yet the minimal timeslot duration is limited by how long link‐layer security operations take. We evaluate the overhead of link‐layer security in time‐slotted channel hopping networks in terms of minimal timeslot length, memory footprint and energy consumption. We implement full link‐layer security on a range of hardware platforms, exploring different hardware/software implementation strategies. Through an extensive measurement campaign, we quantify the advantage of hardware accelerations for link‐layer security and show how the minimal duration of a timeslot varies between 9 and 88ms for the most common configuration, depending on hardware support. Furthermore, we also highlighted the impact that the timeslot duration has on both high‐level application design and energy consumption. Copyright © 2016 John Wiley &amp; Sons, Ltd.

Plexi: Adaptive re-scheduling web-service of time synchronized low-power wireless networks

Industrial IoT applications require highly dependable monitoring and actuation capabilities of remote interoperable low power devices. Time scheduling with channel hopping has been a well-attested mechanism to address these requirements in volatile environments. Yet, scheduling algorithms to date are not adaptive enough to changes in deployed applications and their environments. plexi is a restful web service API for monitoring and scheduling IEEE802.15.4e network resources hiding the complexity of schedule deployment and modification. On top, plexiflex allows any given scheduler to adapt to network performance changes by monitoring periodic data streams coming from the nodes. It triggers resource (de)allocation aiming at stable network performance. Both plexi API and plexiflex adaptive rescheduling algorithm allow for interoperability among devices, schedulers and applications. Experiments to real TSCH network deployments have shown significant gains of plexiflex compared to fixed offline scheduling. Via monitoring the interarrival time of those stream data packets, plexiflex can identify wiring new node joining and rewiring events and reschedule when and where is needed.

Wave: a distributed scheduling algorithm for convergecast in IEEE 802.15.4e TSCH networks

AbstractThe IEEE 802.15.4e MAC amendment has been proposed to meet the requirements of industrial applications. Using slotted medium access with channel hopping, the MAC layer orchestrates the medium accesses of nodes according to a given schedule. Nevertheless, this amendment does not specify how this schedule is computed. The purpose of this paper is to propose a distributed joint time slot and channel assignment, called Wave, for data gathering in low‐power lossy networks. This schedule targets minimised data convergecast delays by reducing the total number of slots in the schedule. Moreover, Wave ensures the absence of conflicting transmissions in the schedule provided. In such a schedule, a node is awake only during its transmission slots and those of its children in the convergecast routing graph. Thus, energy efficiency is ensured. In this paper, we present Wave with its properties (e.g. support of heterogeneous traffic, support of a sink equipped with multiple interfaces, worst case delays and buffer size) and compare it with a centralised scheduling algorithm like TMCP and a distributed one like DeTAS. Simulation results show the good performance of Wave compared with TMCP. Because in an industrial environment, several routing graphs can coexist, we study how Wave supports this coexistence. Copyright © 2015 John Wiley &amp; Sons, Ltd.