Nicola Accettura

Standardized Protocol Stack for the Internet of (Important) Things

We have witnessed the Fixed Internet emerging with virtually every computer being connected today; we are currently witnessing the emergence of the Mobile Internet with the exponential explosion of smart phones, tablets and net-books. However, both will be dwarfed by the anticipated emergence of the Internet of Things (IoT), in which everyday objects are able to connect to the Internet, tweet or be queried. Whilst the impact onto economies and societies around the world is undisputed, the technologies facilitating such a ubiquitous connectivity have struggled so far and only recently commenced to take shape. To this end, this paper introduces in a timely manner and for the first time the wireless communications stack the industry believes to meet the important criteria of power-efficiency, reliability and Internet connectivity. Industrial applications have been the early adopters of this stack, which has become the de-facto standard, thereby bootstrapping early IoT developments with already thousands of wireless nodes deployed. Corroborated throughout this paper and by emerging industry alliances, we believe that a standardized approach, using latest developments in the IEEE 802.15.4 and IETF working groups, is the only way forward. We introduce and relate key embodiments of the power-efficient IEEE 802.15.4-2006 PHY layer, the power-saving and reliable IEEE 802.15.4e MAC layer, the IETF 6LoWPAN adaptation layer enabling universal Internet connectivity, the IETF ROLL routing protocol enabling availability, and finally the IETF CoAP enabling seamless transport and support of Internet applications. The protocol stack proposed in the present work converges towards the standardized notations of the ISO/OSI and TCP/IP stacks. What thus seemed impossible some years back, i.e., building a clearly defined, standards-compliant and Internet-compliant stack given the extreme restrictions of IoT networks, is commencing to become reality.

On Optimal Scheduling in Duty-Cycled Industrial IoT Applications Using IEEE802.15.4e TSCH

As exposed in a recent report by General Electric, an industrial Internet of Things (IoT) is emerging as a commercially viable embodiment of the IoT where physical sensors gather data readings from the field and deliver the traffic to the Internet. The collected real-time big data, in turn, allow the optimizing of entire industry verticals with enormous return of investments. Although opportunities are ample, it comes along with serious engineering design challenges as industrial applications have stringent requirements on delay, lifetime and standards-compliance. To this end, we advocate the use of an IEEE/IETF standardized IoT architecture along with a recently introduced data-centric scheduling algorithm known as traffic aware scheduling algorithm (TASA). Applying graph theoretical tools to the multi-channel, time-synchronized, and duty-cycled nature of TASA, we rigorously derive optimality and bounds on the minimum number of needed active slots (impacting end-to-end delays) and the network duty-cycle (impacting lifetime). We demonstrate the enormous superiority of TASA over traditional IEEE802.15.4/ZigBee approaches in terms of energy efficiency. The outcome of this paper is currently to lay foundations of the recently formed IETF standardization group 6TSCH with the aim to significantly improve IoT data flows over IEEE802.15.4e TSCH and IETF 6LoWPAN/ROLL enabled technologies.

Traffic Aware Scheduling Algorithm for reliable low-power multi-hop IEEE 802.15.4e networks

The Time Synchronized Channel Hopping (TSCH) protocol is part of the newly defined IEEE 802.15.4e standard and represents the latest generation of highly reliable low-power MAC protocols. With implementation details left open, we conceive here a novel Traffic Aware Scheduling Algorithm (TASA) by extending the theoretically well-established graph theory methods of matching and coloring by means of an innovative approach based on network topology and traffic load. TASA is able to support emerging industrial applications requiring low latency at low duty cycle and power consumption. Preliminary simulation results have also been reported to highlight the effectiveness of the proposed algorithm.

Performance analysis of the RPL Routing Protocol

The IETF Routing Over Low-power and Lossy Networks working group has recently proposed the IPv6 Routing Protocol for Low power and Lossy Networks, i.e., the RPL protocol. It has been designed to face the typical requirements of wireless sensor networks. Given its relevance in the industrial and scientific communities, this paper presents a performance analysis of RPL based on simulations. Our results clearly show that RPL can ensure a very fast network set-up, thus allowing the development of advanced monitoring applications also in critical conditions. On the other hand, we found that further research is required to optimize the RPL signaling in order to decrease the protocol overhead.

Decentralized Traffic Aware Scheduling for multi-hop Low power Lossy Networks in the Internet of Things

The emerging IEEE802.15.4e standard and IETF RPL routing protocol are core to the organization of multi-hop Low-power and Lossy Networks. They provide key functionalities useful for a really viable Internet of Things. However, several open issues still remain and require research efforts to be solved. Among others, the design of effective scheduling schemes in such systems is one of the major problems; in fact, there are no specifications about how schedules should be realized. Trying to fill this gap, this paper presents a new Decentralized Traffic-Aware Scheduling algorithm, which is able to construct optimum multi-hop schedules in a distributed fashion. Its effectiveness has been proved by using simulation results and comparing it with a centralized scheme. The reported performance results encourage the use of the developed scheduling technique, since it allows a very efficient queue management, and thus it minimizes packet discards due to buffer overflows, while at the same time minimizing the network duty cycle.

On-the-Fly Bandwidth Reservation for 6TiSCH Wireless Industrial Networks

In smart factory applications, sensors, actuators, field devices, and supervision systems often require a high degree of reliability and timeliness in information exchange. The quality of service provided by the underlying industrial communication network is a key requisite for quality of control. In this context, the WirelessHART, ISA100.11a, and IEEE802.15.4e time-slotted channel hopping standards contribute novel protocols to support quasi-deterministic services, based on wireless short-range communication technologies. The recently created IETF 6TiSCH working group binds IPv6 to this market. Within the 6TiSCH architecture, the 6top sublayer manages the way communication resources are scheduled in time and frequency. The on-the-fly (OTF) bandwidth reservation module plays a complementary role; it is a distributed approach for adapting the scheduled bandwidth to network requirements. This paper first describes the OTF module and its interactions with the 6top sublayer. It then presents the simulation results of the OTF, drawn from a realistic 50-sensor mote multi-hop network that models a small industrial plant. Results show that the OTF can attain an end-to-end latency of the order of a second, with over 99% end-to-end reliability. The first real-world OTF implementation in OpenWSN is presented to demonstrate that it can easily be added within the 6TiSCH architecture.

Decentralized Traffic Aware Scheduling in 6TiSCH Networks: Design and Experimental Evaluation

This paper capitalizes on two emerging trends, i.e., the growing use of wireless at the edge of industrial control networks and the growing interest to integrate IP into said networks. This is facilitated by recent design contributions from the IEEE and the IETF, where the former developed a highly efficient deterministic time-frequency scheduled medium access control protocol in the form of IEEE 802.15.4e timeslotted channel hopping (TSCH) and the latter IPv6 networking paradigms in the form of 6LoWPAN/ROLL, and scheduling approaches in the form of 6TiSCH. The focus of the present work is on advancing the state-of-the-art of deterministic 6TiSCH schedules toward more flexible but equally reliable distributed approaches. In addition, this paper aims to introduce the first implementation of 6TiSCH networks for factory automation environments: it outlines the challenges faced to overcome the scalability issues inherent to multihop dense low-power networks; the experimental results confirm that the naturally unreliable radio medium can support time-critical and reliable applications. These developments pave the way for wireless industry-grade monitoring approaches.

Standardized power-efficient & internet-enabled communication stack for capillary M2M networks

Machine-to-machine (M2M) communications refer to the ability of devices to communicate with each other without human intervention. Being arguably the most industrial branch of the emerging Internet of Things (IoT), it has some very stringent requirements on reliability, low-power and often delay. With cellular M2M today still being relatively power hungry, we concentrate in this paper on capillary M2M which is also more cost-efficient. Capillary M2M systems however are known to suffer from poor reliability and unbounded delay. To this end, we argue for a communication stack composed of latest IEEE and IETF protocols, which allows meeting the stringent requirements. Notably, the emerging IEEE 802.15.4e MAC coupled with a suitable IETF 6LoWPAN adaption and IETF ROLL routing protocol is shown to allow for aggressive duty cycling without jeopardizing reliability and delays.

An Energy Efficient and Reliable Composite Metric for RPL Organized Networks

In the recent past, we witnessed to a dramatic growth of networks with a huge number of interconnected wireless nodes exchanging large amounts of information. This has brought to the need of ad-hoc, energy-aware protocols suitable for low-power and lossy networks. Among these, Routing Protocol for Low Power and Lossy Networks (RPL) is surely one of the most interesting ones. It chooses the optimal routes from a source to a destination node, based on specific metrics. In this work we present a RPL compliant composite metric that considers both reliability and energy. Its aim is twofold. First, it realizes energy consumption balancing, so that each node tends to consume the same amount of energy of all the others, thus prolonging the overall network lifetime. Second, it takes into account data reliability along the paths, expressed by the well known Expected Transmission Count (ETX). The effectiveness of the proposed metric is confirmed by some interesting simulation results, that strongly encourage a deeper investigation on this issue.

The Capture-Recapture approach for population estimation in computer networks

The estimation of a large populations size by means of sampling procedures is a key issue in many networking scenarios. Their application domains span from RFID systems to peer-to-peer networks; from traffic analysis to wireless sensor networks; from multicast networks to WLANs. The present contribution aims at illustrating and classifying in a coherent framework the main approaches proposed so far in the computer networks literature to deal with such a problem. In particular, starting from the methodologies proposed in ecological studies since the last century, this paper surveys their counterparts in the computer network domain, finding that many lessons can be gained from this insightful investigation. Capture-Recapture techniques are deeply analyzed to allow the reader to exactly understand their pros, cons, and applicability bounds. Finally, some open issues that deserve further investigations and could be relevant to afford estimation problems in next generation Internet are discussed for sake of completeness.