A Case for Time Slotted Channel Hopping for ICN in the IoT

Recent proposals to simplify the operation of the IoT include the use of Information Centric Networking (ICN) paradigms. While this is promising, several challenges remain. In this paper, our core contributions (a) leverage ICN communication patterns to dynamically optimize the use of TSCH (Time Slotted Channel Hopping), a wireless link layer technology increasingly popular in the IoT, and (b) make IoT-style routing adaptive to names, resources, and traffic patterns throughout the network--both without cross-layering. Through a series of experiments on the FIT IoT-LAB interconnecting typical IoT hardware, we find that our approach is fully robust against wireless interference, and almost halves the energy consumed for transmission when compared to CSMA. Most importantly, our adaptive scheduling prevents the time-slotted MAC layer from sacrificing throughput and delay

LPDQ: a self-scheduled TDMA MAC protocol for one-hop dynamic lowpower wireless networks

Current Medium Access Control (MAC) protocols for data collection scenarios with a large number of nodes that generate bursty traffic are based on Low-Power Listening (LPL) for network synchronization and Frame Slotted ALOHA (FSA) as the channel access mechanism. However, FSA has an efficiency bounded to 36.8% due to contention effects, which reduces packet throughput and increases energy consumption. In this paper, we target such scenarios by presenting Low-Power Distributed Queuing (LPDQ), a highly efficient and low-power MAC protocol. LPDQ is able to self-schedule data transmissions, acting as a FSA MAC under light traffic and seamlessly converging to a Time Division Multiple Access (TDMA) MAC under congestion. The paper presents the design principles and the implementation details of LPDQ using low-power commercial radio transceivers. Experiments demonstrate an efficiency close to 99% that is independent of the number of nodes and is fair in terms of resource allocation.Peer ReviewedPostprint (author’s final draft

Standardized low-power wireless communication technologies for distributed sensing applications

Recent standardization efforts on low-power wireless communication technologies, including time-slotted channel hopping (TSCH) and DASH7 Alliance Mode (D7AM), are starting to change industrial sensing applications, enabling networks to scale up to thousands of nodes whilst achieving high reliability. Past technologies, such as ZigBee, rooted in IEEE 802.15.4, and ISO 18000-7, rooted in frame-slotted ALOHA (FSA), are based on contention medium access control (MAC) layers and have very poor performance in dense networks, thus preventing the Internet of Things (IoT) paradigm from really taking off. Industrial sensing applications, such as those being deployed in oil refineries, have stringent requirements on data reliability and are being built using new standards. Despite the benefits of these new technologies, industrial shifts are not happening due to the enormous technology development and adoption costs and the fact that new standards are not well-known and completely understood. In this article, we provide a deep analysis of TSCH and D7AM, outlining operational and implementation details with the aim of facilitating the adoption of these technologies to sensor application developers.Peer ReviewedPostprint (published version

Determinism Through Path Diversity: Why Packet Replication Makes Sense

International audienceIndustrial low-power wireless mesh standards, such as IEEE802.15.4-TSCH, WirelessHART and ISA100.10a, offer wire-like end-to-end reliability and a decade of battery lifetime. These technologies have become de-facto standards, used in the most demanding applications such as industrial process monitoring. In this paper, we explore what it takes to go from industrial process monitoring to industrial process control. The difference is that, in the latter case, the network needs to provide low and predicable latency, and deterministic operation. We explore the overall usefulness of packet replication, in which a source node sends multiple copies of a packet on disjoint multihop paths. We show, through extensive simulation, that packet replication allows for a reduction of end-to-end latency by 40%. In addition, packet replication significantly improves the network reliability through path diversity. This work is directly in line with standardization activities at the IETF 6TiSCH and DetNet working groups, to which it is being contributed

A decentralized scheduling algorithm for time synchronized channel hopping

Abstract. 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 typically computed by a central node. This paper presents, to our knowledge, the first scheduling algorithm for TSCH networks which both is distributed and which copes with a mobile nodes. Two scheduling algorithms are presented. Aloha-based scheduling allocates one frequency channel for broadcasting advertisements for new neighbors. Reservation-based scheduling augments Aloha-based scheduling with a dedicated slot for targeted advertisements based on gossip information. A mobile ad-hoc network with frequent connectivity changes is simulated, and the performance of the two proposed algorithms is assessed against the optimal case. Reservation-based scheduling performs significantly better than Aloha-based scheduling, suggesting that the improved network reactivity is worth the increased algorithmic complexity and resource consumption

Constructive Interference in 802.15.4: A Tutorial

International audienceConstructive Interference (CI) can happen when multiple wireless devices send the same frame at the same time. If the time offset between the transmissions is less than 500 ns, a receiver will successfully decode the frame with high probability. CI can be useful for achieving low-latency communication or low-overhead flooding in a multi-hop low-power wireless network. The contribution of this article is threefold. First, we present the current state-of-the-art CI-based protocols. Second, we provide a detailed hands-on tutorial on how to implement CI-based protocols on TelosB motes, with well documented open-source code. Third, we discuss the issues and challenges of CI-based protocols, and list open issues and research directions. This article is targeted at the level of practicing engineers and advanced researchers and can serve both as a primer on CI technology and a reference to its implementation

Synchronous and Concurrent Transmissions for Consensus in Low-Power Wireless

With the emergence of the Internet of Things, autonomous vehicles and the Industry 4.0, the need for dependable yet adaptive network protocols is arising. Many of these applications build their operations on distributed consensus. For example, UAVs agree on maneuvers to execute, and industrial systems agree on set-points for actuators.Moreover, such scenarios imply a dynamic network topology due to mobility and interference, for example. Many applications are mission- and safety-critical, too.Failures could cost lives or precipitate economic losses.In this thesis, we design, implement and evaluate network protocols as a step towards enabling a low-power, adaptive and dependable ubiquitous networking that enables consensus in the Internet of Things. We make four main contributions:- We introduce Orchestra that addresses the challenge of bringing TSCH (Time Slotted Channel Hopping) to dynamic networks as envisioned in the Internet of Things. In Orchestra, nodes autonomously compute their local schedules and update automatically as the topology evolves without signaling overhead. Besides, it does not require a central or distributed scheduler. Instead, it relies on the existing network stack information to maintain the schedules.- We present A2 : Agreement in the Air, a system that brings distributed consensus to low-power multihop networks. A2 introduces Synchrotron, a synchronous transmissions kernel that builds a robust mesh by exploiting the capture effect, frequency hopping with parallel channels, and link-layer security. A2 builds on top of this layer and enables the two- and three-phase commit protocols, and services such as group membership, hopping sequence distribution, and re-keying.- We present Wireless Paxos, a fault-tolerant, network-wide consensus primitive for low-power wireless networks. It is a new variant of Paxos, a widely used consensus protocol, and is specifically designed to tackle the challenges of low-power wireless networks. By utilizing concurrent transmissions, it provides a dependable low-latency consensus.- We present BlueFlood, a protocol that adapts concurrent transmissions to Bluetooth. The result is fast and efficient data dissemination in multihop Bluetooth networks. Moreover, BlueFlood floods can be reliably received by off-the-shelf Bluetooth devices such as smartphones, opening new applications of concurrent transmissions and seamless integration with existing technologies

Energy-efficient wireless communication schemes and real-time middleware for machine-to-machine networks

Esta tesis estudia sistemas Machine-to-Machine (M2M) en los que se ejecutan tareas de manera autónoma sin, o con mínima intervención humana. Los sistemas M2M están formados por dispositivos desplegados en un entorno que recolectan información relacionada con una tarea y la envían a aplicaciones para su proceso. Las aplicaciones optimizan estas tareas y responden a los dispositivos con comandos de control. Idealmente, después de configurar las políticas de tareas, los humanos son excluidos del lazo de control. Un importante caso de uso en M2M es la automatización de la red eléctrica, también conocido como Smart Grid, que se trata en esta tesis. Muchos escenarios M2M requieren dispositivos de bajo bitrate, bajo coste y que puedan ser fácilmente desplegables y mantenidos. Una solución adecuada son los dispositivos inalámbricos, alimentados por batería y de capacidades limitadas (con reducida potencia de procesado y memoria). Un bajo mantenimiento requiere años de vida, que sólo pueden conseguirse con protocolos de comunicación altamente eficientes energéticamente. En esta tesis nos centramos principalmente en las capas MAC y de enlace (especialmente en esquemas Cooperative Automatic Repeat Request) para mejorar la eficiencia energética de los dispositivos. Proponemos y evaluamos extensiones de Cooperative MAC para varios estándares como IEEE 802.11, IEEE 802.15.4 y sus revisiones MAC. El transmisor radio de los dispositivos puede ponerse en estado de reposo cuando está inactivo, llevando a cortos periodos de activación (duty-cycle) en dispositivos de bajo bitrate, consiguiendo así un ahorro energético considerable. Dado que la capa MAC controla los estados de reposo de los transmisores radio, los esquemas de Duty-Cycle MAC son el pilar de las comunicaciones energéticamente eficientes. Por ello, en esta tesis diseñamos, analizamos y evaluamos esquemas Cooperative and Duty-Cycled ARQ (CDC-ARQ). CDC-ARQ se basa en la (re)transmisión dinámica de paquetes (dynamic packet forwarding) dependiendo del estado del canal inalámbrico. Cuantificamos las ganancias considerando enlaces inalámbricos de baja potencia con modelos realistas, que sufren efectos de apantallamiento (shadowing) desvanecimientos (fading) de canal, y presentamos las condiciones bajo las cuales CDC-ARQ consiguen mejores resultados que las técnicas estándar de forwarding. Finalmente, determinamos estrategias óptimas de selección de enlace y retransmisión para direct, multi-hop y CDC-ARQ forwarding. Los esquemas de comunicación inalámbricos energéticamente eficientes son adecuados, por ejemplo, para automatización de edificios y hogar, contribuyendo a un buen uso de la energía eléctrica en dichos escenarios. Después de considerar el entorno de dispositivos, la tesis se centra en las aplicaciones, al otro lado de los sistemas M2M. Las aplicaciones típicamente intercambian datos sobre amplias zonas con varios dispositivos remotos. Las técnicas de computación distribuida, estandarizadas e implementadas en plataformas middleware para sistemas M2M, facilitan este intercambio de datos. Los requisitos de comunicación de estas aplicaciones son diversos en términos de latencia, número de actualizaciones, número de dispositivos asociados, etc. Mientras que las soluciones middleware existentes tales como ETSI M2M satisfacen los requisitos de ciertas aplicaciones, dichas soluciones son inadecuadas para los requisitos de latencia de transmisión en tiempo real. Esta tesis propone y analiza modificaciones del ETSI M2M que mejoran el rendimiento en tiempo real. El análisis se ejemplifica con tres aplicaciones Smart Grid, una relacionada con la automatización del hogar y edificios, y las otras dos con la monitorización y control del flujo de potencia de la red eléctrica.This thesis studies emerging Machine-to-Machine (M2M) systems that execute automated tasks without, or with minimum human intervention. M2M systems consist of devices deployed in the field to collect task-related information and send it to remote applications for processing. The applications optimise the tasks and issue control commands back to the devices. Ideally, after configuring the task policies, humans are excluded from the control loop. A prominent and urgent M2M use case concentrates on the automation of the electric power grid, also known as Smart Grid, that is considered in the thesis. Many M2M scenarios require devices that are low-rate, low-cost and can be easily deployed and maintained. A fitting solution are wireless, battery-powered and resource-constrained devices (with limited processing power and memory). Low-maintenance requires years of lifetime, that can only be achieved with unprecedented energy efficiency of communication protocols. Specifically, we focus on the MAC and link layers in this thesis (especially on the Cooperative Automatic Repeat Request schemes) to improve the energy efficiency of the devices. Cooperative MAC extensions to the various standard technologies such as IEEE 802.11, IEEE 802.15.4 and its MAC amendments are proposed and evaluated. The radio transceiver of a device can be put to sleep state when inactive, yielding very low duty-cycles for low-rate devices, and thus achieving significant energy savings. Since the MAC layer controls the radio transceiver sleep states, duty-cycled MAC schemes are the cornerstone of the energy-efficient communication schemes. To that end, Cooperative and Duty-Cycled ARQ (CDC-ARQ) scheme has been designed, analysed and evaluated in this thesis. CDC-ARQ is based on dynamic packet forwarding depending on the current state of the wireless channel. The benefits are quantified by considering realistic wireless low-power links that experience shadowing and multipath fading channel effects. The conditions under which CDC-ARQ outperforms the standard forwarding techniques are presented. Finally, optimal link selection and retransmission strategies are determined for direct, multi-hop or CDC-ARQ forwarding. The studied energy-efficient wireless schemes are suitable e.g. for home and building automation which can contribute to the efficient use of the electric power in homes and buildings. After considering the device domain, the focus of this thesis turns to the applications at the other end of the M2M system. The applications typically exchange data over wide areas with many remote devices. Distributed computing techniques facilitate this data exchange, standardised and implemented in the middleware platform for M2M systems. The communication requirements of these applications are diverse in terms of data latency, update rate, number of associated devices etc. While the existing middleware solutions such as ETSI M2M fully support communication requirements of some applications, the solution is inadequate when it comes to the real-time latency constraint. Some suitable upgrades that improve the real-time performance of data exchange in ETSI M2M middleware are analysed in the thesis. The analysis is exemplified with three Smart Grid applications, one related to the home and building automation and the other two concerned with monitoring and control of the power flow in the electric grid