The landscape of the contemporary IoT radio access technologies (RATs) is excessively diverse, especially when it comes to such a complex environment as Smart City. On the one hand, this diversity offers operators sufficient flexibility to select the most appropriate RAT for their target application. On the other hand, it becomes a severe limiting factor leading to high level of uncertainty for the IoT device vendors, who need to decide, which technology to support in their hardware. In this paper, we consider the provisioning of the low-power wide area network (LPWAN) devices supporting multiple RATs. First, we briefly discuss the parameters of several potential radio technologies as well as analyze the pros and cons of combining them in a single device. Next, we prototype a real-life device capable of communicating via two perspective LPWAN technologies, namely, LoRaWAN and NB-IoT, and report on the initial results of its performance evaluation. These confirm the feasibility of instrumenting dual-mode devices as well as reveal several important aspects related to the development of multi-radio IoT equipment and its performance. In our view, due to their higher flexibility, reliability, and dependability, the devices such as the one developed can be beneficial for various Smart City applications, with smart energy grids and road traffic control being only two of many examples.

It is expected that the number of the Internet of Things (IoT) devices will grow significantly in the coming years. Batteries, which are today the most common source of energy supply for these devices, have many limitations. The limited capacity and the negative environmental effect of their production and recycling are among the most crucial ones. Energy harvesting has been proposed to overcome this problem. Over the past decade, the academia has produced thousands of papers on this topic, but it is still difficult to find a commercial sensor node operating solely with energy harvesting. One of the major reasons for this is the highly opportunistic and unreliable nature of the energy income from most of the available ambient energy sources. In this paper, we address this problem by proposing a control loop enabling an energy harvesting sensor to request a recharge whenever needed. Energy-wise, the proposed method effectively transforms the operation mode of a passive wireless device from opportunistic to proactive, thus enabling an application to operate in a more predictable manner. The feasibility and efficiency of the proposed approach is demonstrated by implementing a real-life prototype Bluetooth Low Energy capable sensor node equipped with photovoltaic energy harvester, which can communicate and request a recharge from a commercial indoor smart lighting system.

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.

Internet of Things (ioT) drives today's world towards digitalization allowing diverse and innovative use cases. These use cases are changing in a fundamental way how people are conducting their business in various verticals. In this paper we focus on the real estate use case. We deploy a monitoring system in a large open space at University of Oulu. The deployed system visualizes real estate conditions of this environment and gives insight to understanding a LoRaWAN IoT-enabled building. The number of the sensor nodes composing the deployed system reaches 331, with each node comprising five sensors providing information about temperature, humidity, CO2, amount of light, and motion. In the paper we report the results and the lessons learned during the deployment of such an extensive LoRaWAN sensor network. Aside of the practicalities related to the deployment of the network, we characterize and report the performance of the deployed network. The conducted deployment can become a valuable reference for engineers and practitioners, deploying a real estate monitoring system with LoRaWAN.

The major focus of the low power wide area networks (LPWAN) is to provide energy efficiency and large coverage to Internet of Things (IoT) applications that do not require a large bandwidth. There are several LPWAN technologies that can enable these functionalities such as SigFox, LoRa Wide Area Network (LoRaWAN), Narrowband-IoT (NB-IoT), and Weightless. The estimates of the number of wireless IoT devices in the near future are between 20 Billion to even 75 Billion. At the very same time the development and deployment of the 5th generation of mobile networks (5G) is rolling out. Among others, the new technology will deliver huge capacity which can be employed for enabling the backbone connectivity for LPWAN. Therefore, there is a need to have possibility to seamlessly integrate LPWANs with the upcoming 5G. In this work, we investigate how one can integrate the LoRaWAN with the 5G Test Network (5GTN) running in the University of Oulu, Finland. Furthermore, one of the options discussed is implemented in practice and its operation is verified. At the moment the implementation is used for wide range of other research activities beside this work, enabling a third party to bring their LoRaWAN compliant devices for testing and application development.

Efficiency and flexibility are among the key requirements for Wireless Sensor and Actuator Networks (WSAN) of Internet of Things (IoT) era. In this work we present and demonstrate a novel WSAN and IoT platform. The new nodes are constructed by stacking together the different hardware modules encapsulating power sources, processing units, wired and wireless transceivers, sensors and actuators, or sets of those. Once a node is built, its processing unit can automatically identify all the connected hardware modules, obtain required software modules and tune node's operation accounting for its structure, available resources and active applications.

In the paper we present and demonstrate the modular prototyping platform designed for trialing the Internet of Things (IoT) applications. The new devices are constructed by stacking together the various hardware modules encapsulating power sources, processing units, wired and wireless transceivers, sensors and actuators, or sets of those. The main processing unit automatically identifies all the attached modules and adjusts own operation accordingly. The demo will showcase how the platform can be used for building up multi-radio technology enabled wireless devices which will automatically form a heterogeneous wireless sensor and actuator network (WSAN). The possible use case scenarios and the ongoing research activities around the platform will be highlighted as well.

To avoid idle listening and to improve energy efficiency in short range communication networks, a generic wake-up radio (WUR) based medium access control (GWR-MAC) protocol is proposed. GWR-MAC is not restricted to a specific WUR technology or data radio technology, and therefore it is suitable for a variety of scenarios in wireless sensor and body area networks. GWR-MAC includes a bidirectional wake-up procedure and a transmission period for data communication. Two different options for the wake-up procedure are defined: source-initiated and sink-initiated. The data transmission period can be implemented by using different type of channel access methods, which enables scalability. This paper describes the GWR-MAC protocol and an analytical model which is used to explore the energy efficiency of the proposed GWR-MAC based network and conventional duty cycle MAC based network. The comparison is done as a function of number of events to enable the selection of a correct radio technology for different application scenarios. The results clearly illustrate the usefulness and energy efficiency of the proposed protocol especially in applications that have low event frequency and require a low delay wake-up procedure.