Plug and play reconfigurable solutions for heterogeneous IoT

Abstract The world is rapidly developing into a networked society, where people, machines, data, services and applications are tightly integrated by means of information and communications technology. The members of Wireless Sensor requires solutions to support the unprecedented level of the system’s pervasion and heterogeneity, solutions which are missing today. Today’s device-level design procedures are an obstacle in the transition to this heterogeneous future, which demands diverse Internet of Things (IoT) devices, including low-end and low-power ones. Reducing the design and production costs of devices in low to mid-scale production quantities, requires new approaches to cope with application versatility. To address this problem, this thesis proposes a novel wireless sensor and actuator network (WSAN)/IoT device design methodology based on the combination of two approaches: platform-based design and autoconfiguration, that are applied to hardware (HW) and software (SW) components. Unlike the state-of-the-art methodologies, the methodology proposed enables more flexibility both during the design and after device deployment, while reducing the development expenses and time-to-market. Although neither of the two these approaches is fundamentally novel on its own, in this thesis they are employed in, and adapted to, extremely resource restricted systems. The feasibility of the methodology is shown by the development of technology artifact representing a Plug-and-Play enabled WSAN/IoT device platform. The new devices are assembled from HW modules, encapsulating the various power supply, processing, transceiver, sensor and actuator units, or sets of those. The central control unit of a device automatically identifies the HW, and configures the SW accordingly. The technology enablers for this - the HW and SW architectures and interfaces – are reported in this thesis. Experimentation confirms the viability of the proposed concepts and mechanisms. The utility of the designed solutions has been shown by a series of successful research projects and experimental results.Tiivistelmä Maailma on nopeasti muuttumassa verkottuneeksi yhteisöksi, jossa ihmiset, koneet, tiedot, palvelut ja sovellukset ovat integroituneet tiiviisti yhteen tieto- ja viestintätekniikan avulla. Tämän dynaamisen ihmisten ja koneiden välisen yhteisön jäsenillä on erilaisia ja jopa ainutlaatuisia kykyjä. Tämän vision toteutuminen edellyttää toistaiseksi puuttuvia ratkaisuja, jotka tukevat ennennäkemättömän laajalle levinnyttä ja hajanaista järjestelmää. Nykyiset laitetason suunnittelumenetelmät estävät siirtymisen tähän heterogeeniseen tulevaisuuteen, joka edellyttää monipuolisia IoT-laitteita (Internet of Things, esineiden internet), mukaan lukien yksinkertaiset ja vähän virtaa kuluttavat laitteet. Tuotantomääriltään pienten ja keskisuurten laitteiden suunnittelu- ja tuotantokustannusten vähentäminen edellyttää uusia lähestymistapoja sovellusten monipuolisuuden vuoksi. Tutkielmassa ehdotetaan tämän ongelman ratkaisuksi uutta langattomien antureiden ja toimilaitteiden verkon (WSAN) / IoT-laitteiden suunnittelumenetelmää, joka perustuu näiden kahden lähestymistavan yhdistelmään: käyttöympäristöön perustuva rakenne ja automaattinen määritys, joita sovelletaan sekä laitteisto- että ohjelmistokomponentteihin. Toisin kuin nykyiset johtavat menetelmät, ehdotettu menetelmä on joustavampi sekä suunnitteluvaiheessa että laitteen käyttöönoton jälkeen. Tämä vähentää kehityskustannuksia ja laitteen markkinoille tuomiseen tarvittavaa aikaa. Vaikka kumpikaan menetelmä ei ole lähtökohtaisesti uusi, tutkielmassa niitä käytetään järjestelmissä, joissa on äärimmäisen rajoitetut resurssit, ja ne sovitetaan niihin. Menetelmän käyttökelpoisuutta esitellään kehittämällä Plug and Play –yhteensopivaa WSAN-/IoT-laiteympäristöä edustava tekninen artefakti. Uudet laitteet kootaan laitteistomoduuleista, joissa on erilaisia virtalähteitä, prosessori-, lähetin-vastaanotin-, anturija toimilaiteyksikköjä tai niistä koostuvia kokonaisuuksia. Laitteen keskusyksikkö tunnistaa laitteiston automaattisesti ja konfiguroi sen. Tutkielmassa kerrotaan, mitä teknologiaa eli laitteisto- ja ohjelmistoarkkitehtuureja ja -rajapintoja sovelluksessa on käytetty

On the uplink traffic distribution in time for duty-cycle constrained LoRaWAN networks

Abstract In the recent years, the LoRaWAN Low Power Wide Area Network (LPWAN) technology became a critical connectivity enabler for many Internet of Things (IoT) grade monitoring applications and has attracted substantial attention from Academy, Industry, and businesses. One of the most widespread assumption relative to the LoRaWAN and the basis for many studies has been the uniformity of distribution in time of uplink packet transmissions by the different machine devices composing the network. However, recent experimental studies revealed that this implication does not always hold in real-life networks composed of multiple devices, which operate under duty-cycle restrictions. This study dives deeper to identify the reason underlying this effect, which can potentially create negative consequences for the performance of the whole network. Specifically, the paper starts by detailing the key aspects of LoRaWAN procedures and mechanisms and hypothesize that non-uniform distribution of UL transmissions may be caused by a cumulative effect of (i) over-the-air activation (OTAA) procedure, (ii) duty-cycle restrictions and their implementation, and (iii) periodic UL traffic. This hypothesis is validated and confirmed through simulations using the specially-developed model, which captures the details of OTAA and subsequent data transmissions in LoRaWAN. After demonstrating this effect and validity of our hypothesis, several approaches, which can enable to mitigate it, are identified and pinpointed

On spatial diversity for LoRaWAN:experimental evaluation of performance of a dual-gateway network with and without downlink

Abstract The Low Power Wide Area Networks (LPWANs) is today seen as one of the key connectivity enablers for the massive Internet-of-Things (IoT) applications. In this paper, we experimentally study the performance of a LoRaWAN network composed of multiple end devices and two independently operating gateways (GW) for the case of uplink-only and uplink- downlink traffic. Our results demonstrate that even though the spatial diversity due to the use of multiple GWs improves the performance of the network for the packet error rate, it still does not guarantee low packet loss under heavy uplink network traffic. Nonetheless, when the downlink traffic is present, a second GW operating in the uplink-only mode can dramatically increase the uplink packets delivery rate in the network. Therefore, we consider that spatial decoupling of receiver and transmitters, or addition of uplink-only GWs may become an efficient way to improve the performance of LoRaWAN networks with downlink traffic. Even though the limited laboratory environment might have affected the results of our measurements, we expect that many of the observed trends will also stand for the real-life LoRaWAN deployments. For this reason, the presented results might be interesting both for analysts and practitioners working in the field

Design and implementation of the Plug&Play enabled flexible modular wireless sensor and actuator network platform

Abstract In this paper we address the problem of increasing the flexibility of the contemporary wireless sensor and actuator networks (WSANs) in regard to the design of the nodes. For this we propose the concept of a Plug&Play enabled modular WSAN node platform. According to our concept, the new WSAN nodes with desired functionalities can be built by stacking together the different hardware modules encapsulating power sources, processing units, wired and wireless transceivers, sensors and actuators, or even sets of these. Once a node is built, it automatically discovers and identifies all the connected hardware modules, obtains required software and tunes its own operation taking into account the node’s structure, available resources and active applications. In this paper we first present the concept and then report the developed hardware and software architectures and the most critical mechanisms enabling implementation. Also we discuss the practical implementations and report the evaluation results for the prototyped solution. Our results show that the developed platform is much more feature and resource rich than the existing ones, which is achieved at a cost of increased consumption and size. We believe that the unique features of the proposed platform have the potential to drastically change the procedure of WSAN development, especially when it comes to experimenting and developing dynamic WSANs with a heterogeneous structure. In this respect the hardware identification and reconfiguration capabilities conceived in the platform can be utilized in full and may drastically increase the performance of WSANs, if combined with novel control and optimization schemes yet to be developed

Wake-up radio enabled BLE wearables:empirical and analytical evaluation of energy efficiency

Abstract The energy efficiency is an important issue for a vast range of the Internet of Things (IoT) applications. However, especially critical is the energy efficiency in the context of wearable and body-area network devices. At the very same time, due to their nature, these use cases often impose stringent latency and reliability requirements. In this study, we provide an insight into the feasibility and the performance of the Bluetooth Low Energy (BLE) 5.0 compatible sensor devices enriched with a wake-up radio (WUR). Introduction of a low-consuming WUR radio equips a sensing device with a mechanism to know when its data are desired, and helps to avoid the unnecessary data transmissions thus saving energy. To investigate the utility of this approach and the associated with it trade-offs, we start by instrumenting and measuring a real-life prototype of a WUR-equipped BLE device. Based on the results of the real-life measurements, we first develop the analytical models, and then analyze how the latency requirements imposed by the application and the number of the wake-up signals affect the energy consumption of the WUR-equipped BLE device and a standalone BLE sensor. Our results show under which conditions each of these architectures outperforms another one and demonstrate that the WUR approach can be more energy efficient in the case if the desired latency for data delivery is below 2.11 s

Improving the energy efficiency of a LoRaWAN by a UAV-based gateway

Abstract The Internet of Things (IoT) devices and applications are spreading all over around us to become the cardiovascular infrastructure for the data of the cyber-physical systems of the future. The implementation of a reliable collection of telemetry data within various application domains, including medicine, safety, and security, industry, smart cities, or environmental monitoring, to name just a few, is among the major challenges still to be solved. Importantly, many of the use cases imply a huge geographic area span or operation in remote areas with limited infrastructure availability and poor reachability. To address these scenarios in this paper, we propose a combination of the two technologies the Low Power Wide Area Network (LPWAN) and the Unmanned Aerial Vehicles (UAVs). Specifically, we study the energy utility and the communication performance of introducing a UAV-based GW into an LPWAN based on the LoRaWAN technology. The results of our simulations show that a UAV-based GW enables to reduce the mean energy consumption for communication in the network by up to 59%. Depending on the UAV speed, the communication performance in terms of the packet delivery ratio can either increase or decrease by several percentage points

Investigation of the performance of TDoA-based localization over LoRaWAN in theory and practice

Abstract The paper deals with the localization in a low-power wide-area-network (LPWAN) operating long-range wide-area-network (LoRaWAN) technology. The LoRaWAN is, today, one of the most widely used connectivity-enabling technologies for the battery-powered smart devices employed in a broad range of applications. Many of these applications either require or can benefit from the availability of geolocation information. The use of global positioning system (GPS) technology is restrained by the bad propagation of the signal when the device is hidden indoors, and by energy consumption such a receiver would require. Therefore, this paper focuses on an alternative solution implying the use of the information readily available in the LoRaWAN network and application of the time difference of arrival (TDoA) method for the passive geolocation of end-devices in the network. First, the limits of geolocation services in networks that use narrow-band communication channels are discussed, as well as the relevant challenges faced by the TDoA approach. Then, we select five classic TDoA algorithms and evaluate their performance using simulation. Based on these results, we select the two providing the best accuracy (i.e., Chan’s and Foy’s). These algorithms were tested by the field measurements, using the specially designed low-cost gateways and test devices to estimate their real-life performance

Effect of downlink traffic on performance of LoRaWAN LPWA networks:empirical study

Abstract Today the LoRaWAN is among the most widely adopted Low Power Wide Area Network (LPWAN) technologies. In contrast to the other alternatives, LoRaWAN enables deploying both continent-wide public networks, and private networks composing one or several gateways. In this paper, we empirically investigate how does the presence of the downlink traffic affects the performance of uplink for LoRaWAN operating in 868 MHz EU bands. Our results show that in real-life the downlink transmissions can compromise performance of uplink and must be accounted for when planning a network. Also we demonstrate the effects that the selection of secondary frequency channels and data rates have on the performance of a LoRaWAN network. The reported results reveal new dependences and provide the ground truth reference for the future analytical works. For these reasons, the paper can be of interest to both practitioners, planning and deploying LoRaWAN networks, and the researchers performing analytical work on LoRaWAN

Experimental RF-signal based wireless energy transmission

Abstract The distributed measurement and control systems employing wireless connectivity are commonly seen as the key enablers for many novel industry, retail and consumer applications. Even though, the fast spread of large wireless sensor networks today is obstructed by the absence of solutions, which are at the same time dependable, and can minimize both capital and operational expenditures. In this respect the devices, which are powered with the energy collected from their environment, look very attractive. Among all of them, the systems collecting the energy from a designated wireless (i.e., radio frequency (RF)) channel can often enjoy a more stable energy income, which makes them more dependable than their counterparts. Due to this reason, in the current paper we focus on and discuss the key techniques and design aspects enabling development of a real-life RF-powered wireless sensor device. Namely, we address the problems of designing an antenna and the energy harvesting circuit with feasible efficiency. In addition, we detail particular aspects related to the design of a sensor node and optimizing its computing and communication. The developed device is tested in harsh environment as a part of a fast rotating mechanical structure, showing the feasibility of the proposed solutions. The technology discussed in the paper is an important part of the upcoming 5G and IoT development and deployment