Juha Petäjäjärvi

On the coverage of LPWANs: range evaluation and channel attenuation model for LoRa technology

In addition to long battery life and low cost, coverage is one of the most critical performance metrics for the low power wide area networks (LPWAN). In this work we study the coverage of the recently developed LoRa LPWAN technology via real-life measurements. The experiments were conducted in the city of Oulu, Finland, using the commercially available equipment. The measurements were executed for cases when a node located on ground (attached on the roof rack of a car) or on water (attached to the radio mast of a boat) reporting their data to a base station. For a node operating in the 868 MHz ISM band using 14 dBm transmit power and the maximum spreading factor, we have observed the maximum communication range of over 15 km on ground and close to 30 km on water. Besides the actual measurements, in the paper we also present a channel attenuation model derived from the measurement data. The model can be used to estimate the path loss in 868 MHz ISM band in an area similar to Oulu, Finland.

Evaluation of LoRa LPWAN technology for remote health and wellbeing monitoring

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.

Soft handover method for mobile wireless sensor networks based on 6LoWPAN

In many wireless sensor network applications the sensor nodes needs to be mobile. In order to support mobility, the management of several issues, such as routing, handover, security, addressing and auto-configuration of the network needs to be handled. In the past, the main focus of sensor network research has been on static sensor networks, therefore many mobility related problems remain unsolved. In this paper, the focus is on the management of handover and addressing in networks, where gateways and sensor nodes can be mobile. A novel approach, which eliminates unnecessary handovers in the case where multiple gateways are in the range of mobile sensor node, is introduced in this paper. The proposed soft handover method has been implemented and its functionality has been proven in a full-scale testbed. Furthermore, it has been evaluated that the soft handover method performs fairly well also in the sensor network where gateways are static. The proposed solution is designed for IEEE 802.15.4 standard based sensor networks which use 6LoWPAN technique, but it can be easily adapted also to other type of networks.

Performance of a low-power wide-area network based on LoRa technology : Doppler robustness, scalability, and coverage

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.

Extensible modular wireless sensor and actuator network and IoT platform with plug&play module connection

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 nodes operation accounting for its structure, available resources and active applications.

A generic wake-up radio based MAC protocol for energy efficient short range communication

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.

Demo: Modular Multi-radio Wireless Sensor Platform for IoT Trials with Plug&Play Module Connection

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.

On LoRaWAN scalability: Empirical evaluation of susceptibility to inter-network interference

Appearing on the stage quite recently, the Low Power Wide Area Networks (LPWANs) are currently getting much of attention. In the current paper we study the susceptibility of one LPWAN technology, namely LoRaWAN, to the inter-network interferences. By means of excessive empirical measurements employing the certified commercial transceivers, we characterize the effect of modulation coding schemes (known for LoRaWAN as data rates (DRs)) of a transmitter and an interferer on probability of successful packet delivery while operating in EU 868 MHz band. We show that in reality the transmissions with different DRs in the same frequency channel can negatively affect each other and that the high DRs are influenced by interferences more severely than the low ones. Also, we show that the LoRa-modulated DRs are affected by the interferences much less than the FSK-modulated one. Importantly, the presented results provide insight into the network-level operation of the LoRa LPWAN technology in general, and its scalability potential in particular. The results can also be used as a reference for simulations and analyses or for defining the communication parameters for real-life applications.

Preliminary study of superregenerative wake-up receiver for WBANs

A superregenerative wake-up receiver with addressing capability (SR-WUR) for medical and wireless body area networks (WBAN) is proposed in this paper. The SR-WUR is based on a self-quenched superregenerative oscillator (SRO) which enables high sensitivity while maintaining low power consumption. Due to the high sensitivity, low transmit power can be used, which reduces the energy radiation towards a human body. In this work, the SRO is exploited in a novel manner. The SRO charges a voltage multiplier that is used to detect the transmitted bit. The SRO also generates the self-quench and provides a clock signal for a digital logic which processes the received bits. The SR-WUR design is scalable for different type of wireless network applications because the front-end configuration can be changed. Therefore, it can be easily integrated to different type of WBAN platforms. The SR-WUR performance is estimated by using simulations for the back-end components and mathematical analysis for an example front-end configuration. The example configuration includes a low noise amplifier that improves sensitivity of the receiver and it provides isolation between SRO and antenna. Results show that the SR-WUR sensitivity and average power consumption with the example front-end configuration are -84.8 dBm and 186 μW, respectively. Therefore, the proposed SR-WUR has potential to improve the overall energy efficiency, and to reduce the radiated power of wake-up signaling, which are important design goals in medical applications.

D2D communications in LoRaWAN Low Power Wide Area Network: From idea to empirical validation

In this paper we advocate the use of device-to-device (D2D) communications in a LoRaWAN Low Power Wide Area Network (LPWAN). After overviewing the critical features of the LoRaWAN technology, we discuss the pros and cons of enabling the D2D communications for it. Subsequently we propose a network-assisted D2D communications protocol and show its feasibility by implementing it on top of a LoRaWAN-certified commercial transceiver. The conducted experiments show the performance of the proposed D2D communications protocol and enable us to assess its performance. More precisely, we show that the D2D communications can reduce the time and energy for data transfer by 6 to 20 times compared to conventional LoRaWAN data transfer mechanisms. In addition, the use of D2D communications may have a positive effect on the network by enabling spatial re-use of the frequency resources. The proposed LoRaWAN D2D communications can be used for a wide variety of applications requiring high coverage, e.g. use cases in distributed smart grid deployments for management and trading.