Xavier Vilajosana

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.

OpenWSN: a standards‐based low‐power wireless development environment

The OpenWSN project is an open-source implementation of a fully standards-based protocol stack for capillary networks, rooted in the new IEEE802.15.4e Time Synchronized Channel Hopping standard. IEEE802.15.4e, coupled with Internet of Things standards, such as 6LoWPAN, RPL and CoAP, enables ultra-low-power and highly reliable mesh networks, which are fully integrated into the Internet. The resulting protocol stack will be cornerstone to the upcoming machine-to-machine revolution. This article gives an overview of the protocol stack, as well as key integration details and the platforms and tools developed around it. The pure-C OpenWSN stack was ported to four off-the-shelf platforms representative of hardware currently used, from older 16-bit microcontroller to state-of-the-art 32-bit Cortex-M architectures. The tools developed around the low-power mesh networks include visualisation and debugging software, a simulator to mimic OpenWSN networks on a PC, and the environment needed to connect those networks to the Internet. Experimental results presented in this article include a network where motes operate at an average radio duty cycle well below 0.1% and an average current draw of 68  μA on off-the-shelf hardware. These ultra-low-power requirements enable a range of applications, with motes perpetually powered by micro-scavenging devices. OpenWSN is, to the best of our knowledge, the first open-source implementation of the IEEE802.15.4e standard. Copyright

Bootstrapping smart cities through a self-sustainable model based on big data flows

We have a clear idea today about the necessity and usefulness of making cities smarter, the potential market size, and trials and tests. However, it seems that business around Smart Cities is having difficulties taking off and is thus running short of projected potentials. This article looks into why this is the case and proposes a procedure to make smart cities happen based on big data exploitation through the API stores concept. To this end, we first review involved stakeholders and the ecosystem at large. We then propose a viable approach to scale business within that ecosystem. We also describe the available ICT technologies and finally exemplify all findings by means of a sustainable smart city application. Over the course of the article, we draw two major observations, which are seen to facilitate sustainable smart city development. First, independent smart city departments (or the equivalent) need to emerge, much like todays well accepted IT departments, which clearly decouple the political element of the improved city servicing from the underlying technologies. Second, a coherent three-phase smart city rollout is vital, where in phase 1 utility and revenues are generated; in phase 2 only-utility service is also supported; and in phase 3, in addition, a fun/leisure dimension is permitted.

6TiSCH: deterministic IP-enabled industrial internet (of things)

Industrial and IP-enabled low-power wireless networking technologies are converging, resulting in the Industrial Internet of Things. On the one hand, low-power wireless solutions are available today that answer the strict reliability and power consumption requirements of industrial applications. These solutions are based on Time- Synchronized Channel Hopping, a medium access control technique at the heart of industrial standards such as the WirelessHART and ISA100.11a, and layer 1 and 2 standards such as IEEE802.15.4e. On the other hand, a range of standards have been published to allow low-power wireless devices to communicate using the Internet Protocol (IP), thereby becoming true “fingers of the Internet,” and greatly simplifying their integration into existing networks. This article acknowledges the standardization effort to combine those capabilities. The networks resulting from this convergence exhibit reliability and power consumption performances compatible with demanding industrial applications, while being easy to integrate, and following the end-to-end paradigm of todays Internet. In particular, this article presents the work being done in 6TiSCH, a newly-formed working group in the Internet Engineering Task Force, which is standardizing the mechanisms making the Industrial Internet of Things a reality.

Understanding the Limits of LoRaWAN

Low-power wide area networking technology offers long-range communication, which enables new types of services. Several solutions exist; LoRaWAN is arguably the most adopted. It promises ubiquitous connectivity in outdoor IoT applications, while keeping network structures and management simple. This technology has received a lot of attention in recent months from network operators and solution providers. However, the technology has limitations that need to be clearly understood to avoid inflated expectations and disillusionment. This article provides an impartial and fair overview of the capabilities and limitations of LoRaWAN. We discuss those in the context of use cases, and list open research and development questions.

A Realistic Energy Consumption Model for TSCH Networks

Time slotted channel hopping (TSCH) is the highly reliable and ultra-low power medium access control technology at the heart of the IEEE802.15.4e-2012 amendment to the IEEE802.15.4-2011 standard. TSCH networks are deterministic in nature; the actions that occur at each time slot are well known. This paper presents an energy consumption model of these networks, obtained by slot-based “step-by-step” modeling and experimental validation on real devices running the OpenWSN protocol stack. This model is applied to different network scenarios to understand the potential effects of several network optimization. The model shows the impact of keep-alive and advertisement loads and discusses network configuration choices. Presented results show average current in the order of 570 μA on OpenWSN hardware and duty cycles 1% in network relays in both real and simulated networks. Leaf nodes show 0.46% duty cycle with data rates close to 10 packets per minute. In addition, the model is used to analyze the impact on energy consumption and data rate by overprovisioning slots to compensate for the lossy nature of these networks.

IETF 6TSCH: Combining IPv6 Connectivity with Industrial Performance

This document presents a new work called 6TSCH that is starting at the IETF to enable a large IPv6 multi-link subnet with industrial-grade performances of jitter, latency and reliability. The subnet is composed of a high speed powered backbone and a number of IEEE802.15.4e TSCH wireless mesh networks attached and synchronized by specialized Backbone Routers. Route Computation may be achieved in a centralized or in a distributed fashion, and tracks are installed to forward well-known flows with deterministic properties along their multi-hop path.

Label switching over IEEE802.15.4e networks

An open issue still to be addressed in low-power lossy networks (LLNs) is how the application requirements, the available transport services, the network layer routes, and the data link-layer resources are mapped efficiently. This can be explained by the fact that, in most LLNs, link-layer resources cannot be easily managed; this results in a best effort IP layer, and traffic engineering performed solely through flow control at the transport layer. The new IEEE802.15.4e standard defines a link-layer mechanism by which motes in the network synchronise and communicate by following a schedule. Each slot in that schedule can be seen as an atomic link-layer resource, which can be allocated to any arbitrary link in the network. The schedule can be built to match the bandwidth, latency and power requirements of each mote in the network. Managing that schedule is performed centrally in IEEE802.15.4e networks today. This paper explores a solution to achieve the same goal in a distributed manner. Specifically, we argue that this problem is very similar to traffic engineering on todays Internet. We show how multiprotocol label switching can be mapped to LLNs to manage the networks schedule. By using the completely fair distributed scheduler, we show by simulation how this novel link-layer resource allocation scheme yields a proper distribution of end-to-end delays among the motes and an average throughput that achieves the 70% of the maximum possible throughput in the worst conditions tested. Copyright

OpenMote: Open-Source Prototyping Platform for the Industrial IoT

This paper introduces OpenMote, the latest generation of Berkeley motes. OpenMote is a open-hardware prototyping ecosystem designed to accelerate the development of the Industrial Internet of Things (IIoT). It features the OpenMote-CC2538, a state-of-the-art computing and communication device. This device interfaces with several other accessories, or “skins”, through a standardized connector. The skins developed to date include boards to provide power, boards which enable a developer to easily debug the platform, and boards to allow seamless integration of an OpenMote network into the Internet.

Using Oriented Random Search to Provide a Set of Alternative Solutions to the Capacitated Vehicle Routing Problem

In this paper we present SR-GCWS, a simulation-based algorithm for the Capacitated Vehicle Routing Problem (CVRP). Given a CVRP instance, the SR-GCWS algorithm incorporates a randomness criterion to the classical Clarke and Wright Savings (CWS) heuristic and starts an iterative process in order to obtain a set of alternative solutions, each of which outperforms the CWS algorithm. Thus, a random but oriented local search of the space of solutions is performed, and a list of “good alternative solutions” is obtained. We can then consider several properties per solution other than aprioristic costs, such as visual attractiveness, number of trucks employed, load balance among routes, environmental costs, etc. This allows the decision-maker to consider multiple solution characteristics other than just those defined by the aprioristic objective function. Therefore, our methodology provides more flexibility during the routing selection process, which may help to improve the quality of service offered to clients. Several tests have been performed to discuss the effectiveness of this approach.