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The article provides an analysis and reports experimental validation of the various performance metrics of the LoRa low-power wide-area network technology. The LoRa modulation is based on chirp spread spectrum, which enables use of low-quality oscillators in the end device, and to make the synchronization faster and more reliable. Moreover, LoRa technology provides over 150 dB link budget, providing good coverage. Therefore, LoRa seems to be quite a promising option for implementing communication in many diverse Internet of Things applications. In this article, we first briefly overview the specifics of the LoRa technology and analyze the scalability of the LoRa wide-area network. Then, we introduce setups of the performance measurements. The results show that using the transmit power of 14 dBm and the highest spreading factor of 12, more than 60% of the packets are received from the distance of 30 km on water. With the same configuration, we measured the performance of LoRa communication in mobile scenarios. The presented results reveal that at around 40 km/h, the communication performance gets worse, because duration of the LoRa-modulated symbol exceeds coherence time. However, it is expected that communication link is more reliable when lower spreading factors are used.

Low power consumption, low transceiver chip cost and large coverage area are the main characteristics of the low power wide area networks (LPWAN) technologies. We expect that LPWAN can be part of enabling new human-centric health and wellness monitoring applications. Therefore in this work we study the indoor performance of one LPWAN technology, namely LoRa, by the means of real-life measurements. The measurements were conducted using the commercially available equipment in the main campus of the University of Oulu, Finland, which has an indoor area spanning for over 570 meters North to South and over 320 meters East to West. The measurements were executed for a sensor node operating close to human body that was periodically reporting the sensed data to a base station. The obtained results show that when using 14 dBm transmit power and the largest spreading factor of 12 for the 868 MHz ISM band, the whole campus area can be covered. Measured packet success delivery ratio was 96.7 % without acknowledgements and retransmissions.

Abstract. Long lifetime of a wireless sensor/actuator node, low transceiver chip cost and large coverage area are the main characteristics of the low power wide area network (LPWAN) technologies. These targets correlate well with the requirements imposed by the health and wellbeing applications of the digital age. Therefore, LPWANs can found their niche among traditional short range technologies for wireless body area networks, such as ZigBee, Bluetooth and ultra wideband. To check this hypothesis, in this work we investigate the indoor performance with one of the LPWAN technologies, named LoRa, by the means of empirical measurements. The measurements were conducted using the commercially available devices in the main campus of the University of Oulu, Finland. In order to obtain the comprehensive picture, the experiments were executed for the sensor nodes operating with various physical layer settings, i.e., using the different spreading factors, bandwidths and transmit powers. The obtained results indicate that with the largest spreading factor of 12 and 14 dBm transmit power, the whole campus area (570 meters North to South and over 320 meters East to West) can be covered by a single base station. The average measured packet success delivery ratio for this case was 96.7%, even with no acknowledgements and retransmissions used. The campus was covered also with lower spreading factors with 2 dBm transmit power, but considerably more packets were lost. For example with spreading factor 8, 13.1% of the transmitted packets were lost. Aside of this, we have investigated the power consumption of the LoRa compliant transceiver with different physical layer settings. The experiments conducted using the specially designed module show that based on the settings used, the amount of energy for sending the same amount of data may differ up to 200-fold. This calls for efficient selection of the communication mode to be used by the energy restricted devices and emphasizes the importance of enabling adaptive data rate control.

For decades, wireless energy transfer and harvesting remained of focused attention in the research community, but with limited practical applications. Recently, with the development of fifth-generation (5G) mobile technology, the concept of dedicated radio-frequency (RF) charging promises to support the growing market of wearable devices. In this work, we shed light on the potential of wireless RF power transfer by elaborating upon feasible system parameters and architecture, emphasizing the basic trade-offs behind omni-directional and directional outof-band energy transmission, providing system-level performance evaluation, as well as discussing open challenges on the way to sustainable wireless-powered wearables. The key aspects highlighted in this article include system operation choices, user mobility effects, impact of network and user densities, as well as regulatory issues. Ultimately, our research targets to facilitate the integration of wireless RF charging technology into the emerging 5G ecosystem. Index Terms-Wireless energy transfer, 5G mobile technology, wearable devices, RF power transfer, directional energy transmission, system-level performance evaluation. O. Galinina, S. Andreev, and Y. Koucheryavy are with Tampere University of Technology, Finland. H. Tabassum and E. Hossain are with University of Manitoba, MB, Canada. K. Mikhaylov is with University of Oulu, Finland.