IEEE 802.15.4 TSCH in Sub-GHz: Design Considerations and Multi-band Support

This paper has been presented at : The 44th IEEE Conference on Local Computer Networks (LCN) October 14-17, 2019.In Press / En PrensaIn this paper, we address the support of Time-Slotted Channel Hopping (TSCH) on multiple frequency bands within a single TSCH network. This allows to simultaneously run applications with different requirements on link characteristics and to increase resilience against interference. To this end, we first enable sub-GHz communication in TSCH, which has been primarily defined for the 2.4 GHz band. Thereafter, we propose two designs to support multiple physical layers in TSCH on the same nodes. Our experimental evaluation shows that TSCH is applicable in a wide range of data rates between 1.2 kbps and 1000 kbps. We find that data rates of 50 kbps and below have a long communication range and a nearly perfect link symmetry, but also have a 20x higher channel utilization compared to higher data rates, increasing the risk of collisions. Using these findings, we show the advantages of the multi-band support on the example of synchronization accuracy when exchanging TSCH beacons with a low data rate and application data at a high data rate.This work was financed by the H2020 collaborative Europe/Taiwan research project 5G-CORAL (grant num. 761586), the ERCIM Alain Bensoussan postdoc fellowship program, and the distributed environment E-care@home, funded by the Swedish Knowledge Foundation

RF Circuits and Systems Design and Technologies Enabling IoT Applications

Internet of Things (IoT) is the paradigm used nowadays to summarize what is expected form the fourth industrial revolution (Industry 4.0) that is the connectivity of a huge number of “smart” objects disseminated in dissimilar scenarios. This concept is foreseen for practically any possible application domain: from home to transportation, from industry plants to health care, and for space monitoring. Long-term and self-sustainability of these smart thinks (people, objects, tools, etc.) becomes the most relevant aspect for the implementation of such a complex vision. In this framework, my PhD activities have been concentrated. The common goal is to investigate advanced solutions for energy-aware systems and circuits cooperating to enable the IoT paradigm. In particular, I have studied, designed and experimentally demonstrated quite a few novel solutions able to overcome some of the energy limitations existing in IoT. The first project I have developed is an energy-autonomous power relay node at 2.45 GHz that is able to harvest energy from ambient-available or from dedicated RF sources and either use it for operating the node or for supplying power to other nodes. Both a hybrid and a monolithic implementation of the relay system have been implemented. Then I was dedicated to the design of a system enabling Wake-Up Radio (WuR) operation at ultra-low power. The ambitious goal of WuR radios is to reduce the communication power consumption in Wireless Sensor Networks (WSN) and IoT. With this scope in mind, I have proposed and implemented a multi-band WuR architecture. The flexibility of using frequency diversity in WuR enables a more reliable and robust communication channel. From the source side, analytical and experimental studies have been carried out to define the optimum Power Optimized Waveform (POW) excitation to push the WuR sensitivity down to power as low as -65 dBm

Real-time and long lasting Internet of Things through semantic wake-up radios

The world is going towards the Internet of Things (IoT) where trillions of objects that are common in our lives will be enhanced and revolutionized by adding them computational and networking capabilities. Examples are cars, street lamps, industrial machinery, electrical appliances. The corner- stone of Internet of Things research is Wireless Sensor Networks (WSNs). These networks are made of hundreds of low-cost, low-complexity devices endowed with sensors to monitor the surrounding environment or objects. Typically these devices (also called sensors, nodes or motes) are battery-powered, therefore they can operate for a limited amount of time (i.e., days) before running out of energy. This is the main challenge that applications of Wireless Sensor Networks have to face. Since one of the major power consumers in a node is the radio transceiver, a lot of research effort has been put into finding solutions that keep the radio in a low-power state as much as possible, while not harming the communication capability. While this approach brings the network lifetime, i.e. the time before battery-operated nodes die having depleted their energy, to years or more, it introduces significant latency, as the energy reduction comes at the cost of not being able to reach nodes in deep sleep for long period of times. The most promising solution to this problem is the wake-up radio, an additional ultra-low power transceiver used for the sole purpose of triggering the activation of the high power, high bandwidth radio. Wake-up radio enabled IoT systems maintain always on their wake up radio, which has a negligible energy consumption, in this way optimizing both energy and latency performance metrics. Most of the research so far focused on the design of wake-up receivers, while a limited amount of communication protocols that take advantage of this radio has been proposed. Moreover, almost all of these protocols have been evaluated only through simulations. In this thesis we set to start filling this gap. We first evaluate the range performance of an ultra-low power wake-up receiver integrated into a state- of-the-art Wireless Sensor Network mote, the MagoNode++. Based on the results of this evaluation we deploy an outdoor testbed made of MagoNode++ motes. The testbed allows to validate in a real-world scenario our implementation of CTP-WUR, an extension of the widely used Collection Tree Protocol (CTP) for wake-up radio-enabled Wireless Sensor Networks. The comparison between CTP-WUR and CTP demonstrates that wake-up radios can effectively reduce the power consumption and obtain, at the same time, end-to-end latencies in the order of milliseconds, enabling new time critical applications. Based on the results and on the insights gained dur- ing the testbed evaluation a new version of CTP-WUR is presented that improves its performance across all the metrics taken into consideration: end-to-end packet latency, energy consumption and Packet Delivery Ratio

Design, implementation, and measurement procedure of underwater and water surface antenna for lora communication

There is an increasing interest in water bodies, which make up more that seventy percent of our planet. It is thus imperative that the water environment should be remotely monitored. Radio frequency (RF) signals have higher bandwidth and lower latency compared to acoustic signals. However, water has high permittivity and conductivity which presents a challenge for the implementation of RF technology. In this work, we undertook a novel design, fabrication, measurement and implementation of an antenna for a sensor node with dual ability of underwater and water surface long range (LoRa) communication at 868 MHz. It was observed that the antenna’s performance deteriorated underwater without −10 dB effective bandwidth between 668 MHz and 1068 MHz. The introduction of an oil-impregnated paper buffer around the antenna resulted in an effective 400 MHz bandwidth within the same frequency span. The sensor node with the buffered antenna was able to achieve a distance of 6 m underwater and 160 m over water surface communication to a data gateway node. The sensor node without the buffered antenna was only able to achieve 80 m over water surface communication. These experimental results show the feasibility of using the LoRa 868 MHz frequency in underwater and water surface communication

Design of Wireless Sensors for IoT with Energy Storage and Communication Channel Heterogeneity

Autonomous Wireless Sensors (AWSs) are at the core of every Wireless Sensor Network (WSN). Current AWS technology allows the development of many IoT-based applications, ranging from military to bioengineering and from industry to education. The energy optimization of AWSs depends mainly on: Structural, functional, and application specifications. The holistic design methodology addresses all the factors mentioned above. In this sense, we propose an original solution based on a novel architecture that duplicates the transceivers and also the power source using a hybrid storage system. By identifying the consumption needs of the transceivers, an appropriate methodology for sizing and controlling the power flow for the power source is proposed. The paper emphasizes the fusion between information, communication, and energy consumption of the AWS in terms of spectrum information through a set of transceiver testing scenarios, identifying the main factors that influence the sensor node design and their inter-dependencies. Optimization of the system considers all these factors obtaining an energy efficient AWS, paving the way towards autonomous sensors by adding an energy harvesting element to them

Comparison of wireless data transmission protocols for residential water meter applications

This article provides a comparison of various wireless data transmission protocols, such as Wireless M-Bus, LoRaWAN, Sigfox, NB-IoT and a newly developed proprietary protocol, studying their performance in the application of battery-powered residential water meters. Key aspects of the comparison include energy consumption, which is analyzed through comparing unitary amount of charge required to conduct a single, bi-directional data transaction between the meter and base station, and maximum coupling loss which effectively defines the range and coverage in the system. For completeness, the study includes also a brief cost analysis and ends with a conclusion, stating when each of the particular standards should be favored

Design of Wireless Sensors for IoT with Energy Storage and Communication Channel Heterogeneity

Autonomous Wireless Sensors (AWSs) are at the core of every Wireless Sensor Network (WSN). Current AWS technology allows the development of many IoT-based applications, ranging from military to bioengineering and from industry to education. The energy optimization of AWSs depends mainly on: Structural, functional, and application specifications. The holistic design methodology addresses all the factors mentioned above. In this sense, we propose an original solution based on a novel architecture that duplicates the transceivers and also the power source using a hybrid storage system. By identifying the consumption needs of the transceivers, an appropriate methodology for sizing and controlling the power flow for the power source is proposed. The paper emphasizes the fusion between information, communication, and energy consumption of the AWS in terms of spectrum information through a set of transceiver testing scenarios, identifying the main factors that influence the sensor node design and their inter-dependencies. Optimization of the system considers all these factors obtaining an energy efficient AWS, paving the way towards autonomous sensors by adding an energy harvesting element to them