Pere Tuset-Peiro

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.

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.

On the suitability of the 433MHz band for M2M low-power wireless communications: propagation aspects

The 433MHz band is gaining relevance as an alternative to the 2.4GHz band for machine-to-machine communications using low-power wireless technologies. Currently, two standards are being developed that use the 433MHz band, DASH7 Mode 2 and IEEE802.15.4f. The article presents propagation models based on measurements conducted at the 433MHz and 2.4GHz bands that can be used for link budget calculations in both outdoor and indoor environments depending on node height. The results obtained show that the 433MHz band has a larger communication range in both indoor and outdoor environments despite the negative effects of having a larger Fresnel zone. In addition, indoor propagation measurements are conducted in line-of-sight and nonline-of-sight conditions to determine the suitability of channel hopping to combat the effects of multipath propagation. Contrary to the 2.4GHz band, the results show that channel hopping at 433MHz does not provide any link robustness advantage because the channel coherence bandwidth is larger than the whole band bandwidth, and thus, all channels are highly correlated. Copyright

Energy analysis of a contention tree-based access protocol for machine-to-machine networks with idle-to-saturation traffic transitions

Machine-to-Machine (M2M) area networks must provide connectivity between an M2M gateway and a large number of energy-constrained M2M devices. Attaining high energy efficiency is essential in order to prolong devices lifetime. In this paper, we consider a wireless M2M area network composed of hundreds or even thousands of dormant devices that wake up periodically to transmit data upon request from a gateway. We theoretically analyze the energy efficiency of a Medium Access Control (MAC) protocol that uses a tree-splitting algorithm to resolve the collisions among devices: the Distributed Queuing (DQ) access. Computer-based simulations have been carried out to validate the accuracy of the analytical model and to evaluate and compare the energy consumption of devices using also a basic Contention Tree Algorithm (CTA) and Frame Slotted-ALOHA (FSA). Results show that DQ can reduce energy consumption in more than 35% with respect to CTA and in more than 80% with respect to FSA in dense M2M area networks with devices in compliance with the IEEE 802.15.4 physical layer.

Energy performance of distributed queuing access in Machine-to-Machine networks with idle-to-saturation transitions

Machine-to-Machine (M2M) networks must be energy-efficient to operate autonomously for years, or even decades. In this paper, we consider a synchronized duty-cycled M2M network composed of a huge number of dormant devices that periodically wake up to transmit data to a coordinator. We propose the use of Distributed Queuing (DQ) tree-splitting algorithms to optimize the shared access to the channel among the high number of devices, in order to improve the energy efficiency and thus extend the network lifetime. We evaluate the energy performance of DQ access in this kind of dense M2M networks, and we compare it to traditional access schemes based on variations of Frame Slotted-ALOHA (FSA) and the Contention Tree Algorithm (CTA). Computer-based simulations show that DQ can reduce the energy consumption in more than a 50% with respect to FSA and CTA. Results show that there is an optimum number of contention slots which maximizes the energy efficiency of DQ regardless of the number of devices. The performance evaluation presented in this paper also compares the energy consumption of DQ using low power Wi-Fi and IEEE 802.15.4 devices.

Demonstrating Low-Power Distributed Queuing for active RFID communications at 433 MHz

This paper presents a demonstrator of Low-Power Distributed Queuing (LPDQ), a MAC protocol targeted at active RFID systems operating at 433 MHz. LPDQ is based on a packet-based Preamble Sampling for network synchronization and Distributed Queuing for channel access. Compared to the MAC protocol defined in the ISO 18000-7 standard, based on an analog Preamble Sampling and Frame Slotted ALOHA, LPDQ represents a major breakthrough in terms of system performance and energy consumption. At the MAC layer system performance is close to the optimal, e.g., no collisions during data packet transmission, and tag energy consumption can be reduced by more than 10% compared to FSA.

Experimental Energy Consumption of Frame Slotted ALOHA and Distributed Queuing for Data Collection Scenarios

Data collection is a key scenario for the Internet of Things because it enables gathering sensor data from distributed nodes that use low-power and long-range wireless technologies to communicate in a single-hop approach. In this kind of scenario, the network is composed of one coordinator that covers a particular area and a large number of nodes, typically hundreds or thousands, that transmit data to the coordinator upon request. Considering this scenario, in this paper we experimentally validate the energy consumption of two Medium Access Control (MAC) protocols, Frame Slotted ALOHA (FSA) and Distributed Queuing (DQ). We model both protocols as a state machine and conduct experiments to measure the average energy consumption in each state and the average number of times that a node has to be in each state in order to transmit a data packet to the coordinator. The results show that FSA is more energy efficient than DQ if the number of nodes is known a priori because the number of slots per frame can be adjusted accordingly. However, in such scenarios the number of nodes cannot be easily anticipated, leading to additional packet collisions and a higher energy consumption due to retransmissions. Contrarily, DQ does not require to know the number of nodes in advance because it is able to efficiently construct an ad hoc network schedule for each collection round. This kind of a schedule ensures that there are no packet collisions during data transmission, thus leading to an energy consumption reduction above 10% compared to FSA.

I3Mote: An Open Development Platform for the Intelligent Industrial Internet

In this article we present the Intelligent Industrial Internet (I3) Mote, an open hardware platform targeting industrial connectivity and sensing deployments. The I3Mote features the most advanced low-power components to tackle sensing, on-board computing and wireless/wired connectivity for demanding industrial applications. The platform has been designed to fill the gap in the industrial prototyping and early deployment market with a compact form factor, low-cost and robust industrial design. I3Mote is an advanced and compact prototyping system integrating the required components to be deployed as a product, leveraging the need for adopting industries to build their own tailored solution. This article describes the platform design, firmware and software ecosystem and characterizes its performance in terms of energy consumption.

Teaching Communication Technologies and Standards for the Industrial IoT? Use 6TiSCH!

The IETF 6TiSCH stack encompasses IEEE802.15.4 TSCH, IETF 6LoWPAN, RPL, and CoAP. It is one of the key standards-based technologies to enable industrial process monitoring and control, and unleash the Industrial Internet of Things (IIoT). The 6TiSCH stack is also a valuable asset for educational purposes, as it integrates an Internet-enabled IPv6-based upper stack with stateof- the-art low-power wireless mesh communication technologies. Teaching with 6TiSCH empowers students with a valuable set of competencies, including topics related to computer networking (medium access control operation, IPv6 networking), embedded systems (process scheduling, concurrency), and wireless communications (multipath propagation, interference effects), as well as application requirements for the IIoT. This article discusses how the 6TiSCH stack can be incorporated into existing and new curricula to teach the next generation of electrical engineering and computer science professionals about designing and deploying such networks. It also gives a comprehensive overview of the 6TiSCH stack and the tools that exist to support a course based on it.

Combining distributed queuing with energy harvesting to enable perpetual distributed data collection applications

This paper presents, models, and evaluates energy harvesting–aware distributed queuing (EH-DQ), a novel medium access control protocol that combines distributed queuing with energy harvesting (EH) to address data collection applications in industrial scenarios using long-range and low-power wireless communication technologies. We model the medium access control protocol operation using a Markov chain and evaluate its ability to successfully transmit data without depleting the energy stored at the end devices. In particular, we compare the performance and energy consumption of EH-DQ with that of time-division multiple access (TDMA), which provides an upper limit in data delivery, and EH-aware reservation dynamic frame slotted ALOHA, which is an improved variation of frame slotted ALOHA. To evaluate the performance of these protocols, we use 2 performance metrics: delivery ratio and time efficiency. Delivery ratio measures the ability to successfully transmit data without depleting the energy reserves, whereas time efficiency measures the amount of data that can be transmitted in a certain amount of time. Results show that EH-DQ and TDMA perform close to the optimum in data delivery and outperform EH-aware reservation dynamic frame slotted ALOHA in data delivery and time efficiency. Compared to TDMA, the time efficiency of EH-DQ is insensitive to the amount of harvested energy, making it more suitable for energy-constrained applications. Moreover, compared to TDMA, EH-DQ does not require updated network information to maintain a collision-free schedule, making it suitable for very dynamic networks.