Adaptive Multi-Channel Offset Assignment for Reliable IEEE 802.15.4 TSCH Networks

International audienceMore and more IoT applications require low-power operations and high reliability (close to 100%). Unfortunately, radio transmissions are unreliable by nature since they are prone to collision and external interference. The IEEE 802.15.4-2015 TSCH standard has been recently proposed to provide high-reliability through radio channel hopping and by appropriately scheduling all the transmissions. Since some of the radio channels still suffer from external interference, blacklisting techniques consist in detecting bad radio channels, and in privileging the good ones to transmit the packets. MABO-TSCH is a centralized scheduling algorithm which allocates several channel offsets to allow each radio link to apply a localized blacklist. However, such strategy is inefficient for large blacklists. In this study, we propose to allocate the channel offsets dynamically at each timeslot according to the number of parallel transmissions, while still avoiding collisions. We evaluate the performance of our solution relying on a real experimental dataset, highlighting the relevance of dynamic and per timeslot channel offset assignment for environments with high external interference, such as a smart building

A mobility-supporting MAC scheme for bursty traffic in IoT and WSNs

International audienceRecent boom of mobile applications has become an essential class of mobile Internet of Things (IoT), whereby large amounts of sensed data are collected and shared by mobile sensing devices for observing phenomena such as traffic or the environmental. Currently, most of the proposed Medium Access Control (MAC) protocols mainly focus on static networks. However, mobile sensor nodes may pose many communication challenges during the design and development of a MAC protocol. These difficulties first require an efficient connection establishment between a mobile and static node, and then an efficient data packet transmissions. In this study, we propose MobIQ, an advanced mobility-handling MAC scheme for low-power MAC protocols, which achieves for efficient neighbour(hood) discovery and low-delay communication. Our thorough performance evaluation, conducted on top of Contiki OS, shows that MobIQ outperforms state-of-the-art solutions such as MoX-MAC, MOBINET and ME-ContikiMAC, in terms of significantly reducing delay, contention to the medium and energy consumption

Communications fiables pour l'Internet des objets industriels

The Industrial Internet of Things (IIoT) re-uses the Internet of Things mechanisms to enable smart factories. However, industrial applications often require deterministic communications as well as end-to-end reliability close to 100%. To address these requirements, the Time-Slotted Channel Hopping (TSCH) mode of the IEEE 802.15.4 standard was proposed in 2015. TSCH schedules the transmissions to avoid collisions and exploits a slow channel hopping technique to combat external interference. TSCH can be further improved for the IIoT to be exploited in critical industrial applications, which is the main goal of this work. Towards this direction, we highlighted radio links' spatial and temporal characteristics by conducting experiments in indoor testbeds. We proposed blacklisting techniques that exclude from the channel hopping sequence the low-quality channels, thus enhancing the overall performance. Finally, we proposed a scheduling function that aims to meet the requirements of IIoT.L’Internet des Objets Industriel (IIoT) cible les applications critiques telles que les usines intelligentes. Cependant, les applications industrielles requièrent souvent une haute fiabilité. Afin de répondre à ces contraintes, IEEE 802.15.4 a proposé le mode Time-Slotted Channel Hopping (TSCH). TSCH ordonnance les transmissions afin d’éviter les collisions, et du saut de fréquences lent pour combattre les interférences externes. Nous proposons ici d’améliorer TSCH pour les applications industrielles critiques. Nous avons tout d’abord caractérisé spatialement et temporellement les liens radio, à travers une série d’expérimentations sur testbeds. Nous avons également proposé des techniques de type blacklisting permettant d’exclure les moins bons canaux de la séquence de saut de fréquences, permettant ainsi d’améliorer globalement la fiabilité. Finalement, nous avons proposé un algorithme d’ordonnancement des transmissions permettant de fournir haute fiabilité et faible délai

Communications fiables pour l'Internet des objets industriels

L’Internet des Objets Industriel (IIoT) cible les applications critiques telles que les usines intelligentes. Cependant, les applications industrielles requièrent souvent une haute fiabilité. Afin de répondre à ces contraintes, IEEE 802.15.4 a proposé le mode Time-Slotted Channel Hopping (TSCH). TSCH ordonnance les transmissions afin d’éviter les collisions, et du saut de fréquences lent pour combattre les interférences externes. Nous proposons ici d’améliorer TSCH pour les applications industrielles critiques. Nous avons tout d’abord caractérisé spatialement et temporellement les liens radio, à travers une série d’expérimentations sur testbeds. Nous avons également proposé des techniques de type blacklisting permettant d’exclure les moins bons canaux de la séquence de saut de fréquences, permettant ainsi d’améliorer globalement la fiabilité. Finalement, nous avons proposé un algorithme d’ordonnancement des transmissions permettant de fournir haute fiabilité et faible délai.The Industrial Internet of Things (IIoT) re-uses the Internet of Things mechanisms to enable smart factories. However, industrial applications often require deterministic communications as well as end-to-end reliability close to 100%. To address these requirements, the Time-Slotted Channel Hopping (TSCH) mode of the IEEE 802.15.4 standard was proposed in 2015. TSCH schedules the transmissions to avoid collisions and exploits a slow channel hopping technique to combat external interference. TSCH can be further improved for the IIoT to be exploited in critical industrial applications, which is the main goal of this work. Towards this direction, we highlighted radio links' spatial and temporal characteristics by conducting experiments in indoor testbeds. We proposed blacklisting techniques that exclude from the channel hopping sequence the low-quality channels, thus enhancing the overall performance. Finally, we proposed a scheduling function that aims to meet the requirements of IIoT

Communications fiables pour l'Internet des objets industriels

The Industrial Internet of Things (IIoT) re-uses the Internet of Things mechanisms to enable smart factories. However, industrial applications often require deterministic communications as well as end-to-end reliability close to 100%. To address these requirements, the Time-Slotted Channel Hopping (TSCH) mode of the IEEE 802.15.4 standard was proposed in 2015. TSCH schedules the transmissions to avoid collisions and exploits a slow channel hopping technique to combat external interference. TSCH can be further improved for the IIoT to be exploited in critical industrial applications, which is the main goal of this work. Towards this direction, we highlighted radio links' spatial and temporal characteristics by conducting experiments in indoor testbeds. We proposed blacklisting techniques that exclude from the channel hopping sequence the low-quality channels, thus enhancing the overall performance. Finally, we proposed a scheduling function that aims to meet the requirements of IIoT.L’Internet des Objets Industriel (IIoT) cible les applications critiques telles que les usines intelligentes. Cependant, les applications industrielles requièrent souvent une haute fiabilité. Afin de répondre à ces contraintes, IEEE 802.15.4 a proposé le mode Time-Slotted Channel Hopping (TSCH). TSCH ordonnance les transmissions afin d’éviter les collisions, et du saut de fréquences lent pour combattre les interférences externes. Nous proposons ici d’améliorer TSCH pour les applications industrielles critiques. Nous avons tout d’abord caractérisé spatialement et temporellement les liens radio, à travers une série d’expérimentations sur testbeds. Nous avons également proposé des techniques de type blacklisting permettant d’exclure les moins bons canaux de la séquence de saut de fréquences, permettant ainsi d’améliorer globalement la fiabilité. Finalement, nous avons proposé un algorithme d’ordonnancement des transmissions permettant de fournir haute fiabilité et faible délai

LABeL: Link-based Adaptive BLacklisting Technique for 6TiSCH Wireless Industrial Networks

International audienceIndustrial applications require more and more low-power operations , low-delay, deterministic communications as well as end-to-end reliability close to 100%. However, traditional radio technologies are sensitive to external interference, which degrades the reliability and introduces unpredictable delays due to collision detection and retransmissions. Therefore, recent standardization efforts focus on slow channel hopping strategies to provide strict Quality of Service (QoS) for the Industrial Internet of Things (IIoT). By keeping nodes time-synchronized and by employing a channel hopping approach, IEEE 802.15.4-TSCH (Time-Slotted Channel Hoping) aims at providing high-level network reliability. However, some radio channels still suffer from high external interference and need to be blacklisted. Since the interference pattern is rather dynamic, unpredictable and highly localized, we here propose heuristics to decide which channels to blacklist. To avoid deafness, the transmitter and the receiver must also agree on a consistent blacklist. Furthermore, since the external interference may be time-dependent as well, we also propose mechanisms to decide when a channel has to be blacklisted or on the contrary recovered. Our thorough experimental evaluation based on OpenWSN and FIT IoT-LAB highlight the relevance of this approach: with a localized blacklisting strategy, we increase by 20% packet delivery rate for the worst links

LDSF: Low-latency Distributed Scheduling Function for Industrial Internet of Things

International audienceThe Industrial Internet of Things (IIoT) is expected to be a key enabler for the Industry 4.0. However, networked control automation often requires high reliability and a bounded latency to react properly. Thus, modern wireless protocols for industrial networks, such as IEEE 802.15.4-2015 Time Slotted Channel Hopping (TSCH), rely on a strict schedule of the transmissions to avoid collisions and to make the end-to-end traffic deterministic. Unfortunately, guaranteeing a bounded end-to-end latency is particularly challenging since transmissions have to be temporally chained. Even worse, potential degradation of the link quality may result in reconstructing the whole TSCH schedule along the path. In this article, we propose the Low-latency Distributed Scheduling Function (LDSF) that relies on the organization of the slotframe in smaller parts, called blocks. Each transmitter selects the right set of blocks, depending on its hop distance from the border router, so that retransmission opportunities are automatically scheduled. To save energy, a node can still turn off its radio as soon as its packet is correctly acknowledged. Our mathematical analysis as well as our simulation evaluation show the efficiency of the proposed LDSF algorithm compared to three state-of-the-art scheduling functions, the Minimal Scheduling Function (MSF), Low Latency Scheduling Function (LLSF) and Stratum

Is Local Blacklisting Relevant in Slow Channel Hopping Low-Power Wireless Networks?

International audienceWith the large growth of the Internet of Things (IoT), a strong focus has been put on designing and developing energy efficient and high performance protocols. Industrial-type wireless networks require strict and on-time delivery guarantees, such as close to 100% network reliability and ultra low delay. To this aim, standards such as IEEE 802.15.4-TSCH or Wireless HART, aim to guarantee high-level network reliability by keeping nodes time-synchronized and by employing a slow channel hopping pattern to combat noisy environments and external interference. In wireless networks, since all the radio channels are not impacted in a similar manner, blacklisting bad channels may improve performance of the whole wireless infrastructure. In this paper, we perform a thorough experimental study to characterize the radio (for all IEEE 802.15.4 channels) and connectivity among the nodes of an indoor testbed. More precisely, we investigate the locality of these blacklisting techniques and we highlighted: the fact that some channels perform poorly only in a small set of locations, for certain radio links. Our study tends to justify the need for local blacklisting techniques, demanding more control packets, but dealing more efficiently with spectral re-use

Whitelisting Without Collisions for Centralized Scheduling in Wireless Industrial Networks

© 2020 IEEE. Personal use of this material is permitted. Permission from IEEE must be obtained for all other uses, in any current or future media, including reprinting/republishing this material for advertising or promotional purposes, creating new collective works, for resale or redistribution to servers or lists, or reuse of any copyrighted component of this work in other works.International audienceIndustrial applications require more and more low-power operation and high-reliability (close to 100%). Since traditional low-power radio technologies are sensitive to external interference, many recent standards implement frequency hopping schemes. For instance, IEEE 802.15.4-2015 Time Slotted Channel Hopping (TSCH) relies on a deterministic schedule of data transmissions combined with a pseudo-random frequency hopping scheme to improve the reliability. Unfortunately, specific radio channels keep on increasing the average number of retransmissions. Using a subset of the best radio channels (whitelisting) helps to improve the reliability, but may create collisions when used improperly. We here investigate the most accurate techniques to use only the best radio channels while still providing deterministic performance. We propose to group the links per timeslot, allocating them either to the same whitelist or even appropriately reordering them to avoid collisions. Finally, we evaluate the performance of the different whitelisting schemes using an experimental dataset from FIT IoT-LAB platform, proving the relevance of such approach to improve the reliability