Low power wide area (LPWA) networks are attracting a lot of attention primarily because of their ability to offer affordable connectivity to the low-power devices distributed over very large geographical areas. In realizing the vision of the Internet of Things, LPWA technologies complement and sometimes supersede the conventional cellular and short range wireless technologies in performance for various emerging smart city and machine-to-machine applications. This review paper presents the design goals and the techniques, which different LPWA technologies exploit to offer wide-area coverage to low-power devices at the expense of low data rates. We survey several emerging LPWA technologies and the standardization activities carried out by different standards development organizations (e.g., IEEE, IETF, 3GPP, ETSI) as well as the industrial consortia built around individual LPWA technologies (e.g., LoRa Alliance, Weightless-SIG, and Dash7 alliance). We further note that LPWA technologies adopt similar approaches, thus sharing similar limitations and challenges. This paper expands on these research challenges and identifies potential directions to address them. While the proprietary LPWA technologies are already hitting the market with large nationwide roll-outs, this paper encourages an active engagement of the research community in solving problems that will shape the connectivity of tens of billions of devices in the next decade.

Low Power Wide Area Networks: An Overview

LoRa is a long-range, low-power, low-bitrate, wireless telecommunications system, promoted as an infrastructure solution for the Internet of Things: end-devices use LoRa across a single wireless hop to communicate to gateway(s), connected to the Internet and which act as transparent bridges and relay messages between these end-devices and a central network server. This paper provides an overview of LoRa and an in-depth analysis of its functional components. The physical and data link layer performance is evaluated by field tests and simulations. Based on the analysis and evaluations, some possible solutions for performance enhancements are proposed.

https://www.mdpi.com/1424-8220/16/9/1466/pdf

A Study of LoRa: Long Range & Low Power Networks for the Internet of Things

The Internet of Things (IoT) is a promising technology which tends to revolutionize and connect the global world via heterogeneous smart devices through seamless connectivity. The current demand for machine-type communications (MTC) has resulted in a variety of communication technologies with diverse service requirements to achieve the modern IoT vision. More recent cellular standards like long-term evolution (LTE) have been introduced for mobile devices but are not well suited for low-power and low data rate devices such as the IoT devices. To address this, there is a number of emerging IoT standards. Fifth generation (5G) mobile network, in particular, aims to address the limitations of previous cellular standards and be a potential key enabler for future IoT. In this paper, the state-of-the-art of the IoT application requirements along with their associated communication technologies are surveyed. In addition, the third generation partnership project cellular-based low-power wide area solutions to support and enable the new service requirements for Massive to Critical IoT use cases are discussed in detail, including extended coverage global system for mobile communications for the Internet of Things, enhanced machine-type communications, and narrowband-Internet of Things. Furthermore, 5G new radio enhancements for new service requirements and enabling technologies for the IoT are introduced. This paper presents a comprehensive review related to emerging and enabling technologies with main focus on 5G mobile networks that is envisaged to support the exponential traffic growth for enabling the IoT. The challenges and open research directions pertinent to the deployment of massive to critical IoT applications are also presented in coming up with an efficient context-aware congestion control mechanism.

A Survey on 5G Networks for the Internet of Things: Communication Technologies and Challenges

New Internet of Things (IoT) technologies such as Long Range (LoRa) are emerging which enable power efficient wireless communication over very long distances. Devices typically communicate directly to a sink node which removes the need of constructing and maintaining a complex multi-hop network. Given the fact that a wide area is covered and that all devices communicate directly to a few sink nodes a large number of nodes have to share the communication medium. LoRa provides for this reason a range of communication options (centre frequency, spreading factor, bandwidth, coding rates) from which a transmitter can choose. Many combination settings are orthogonal and provide simultaneous collision free communications. Nevertheless, there is a limit regarding the number of transmitters a LoRa system can support. In this paper we investigate the capacity limits of LoRa networks. Using experiments we develop models describing LoRa communication behaviour. We use these models to parameterise a LoRa simulation to study scalability. Our experiments show that a typical smart city deployment can support 120 nodes per 3.8 ha, which is not sufficient for future IoT deployments. LoRa networks can scale quite well, however, if they use dynamic communication parameter selection and/or multiple sinks.

https://dl.acm.org/doi/pdf/10.1145/2988287.2989163

Do LoRa Low-Power Wide-Area Networks Scale?

Low power wide area (LPWA) networks are making spectacular progress from design, standardization, to commercialization. At this time of fast-paced adoption, it is of utmost importance to analyze how well these technologies will scale as the number of devices connected to the Internet of Things inevitably grows. In this letter, we provide a stochastic geometry framework for modeling the performance of a single gateway LoRa network, a leading LPWA technology. Our analysis formulates the unique peculiarities of LoRa, including its chirp spread-spectrum modulation technique, regulatory limitations on radio duty cycle, and use of ALOHA protocol on top, all of which are not as common in today’s commercial cellular networks. We show that the coverage probability drops exponentially as the number of end-devices grows due to interfering signals using the same spreading sequence. We conclude that this fundamental limiting factor is perhaps more significant toward LoRa scalability than for instance spectrum restrictions. Our derivations for co-spreading factor interference found in LoRa networks enables rigorous scalability analysis of such networks.

Low Power Wide Area Network Analysis: Can LoRa Scale?

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.

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

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 spr...

/pdf/performance-of-a-low-power-wide-area-network-based-on-lora-3mp4xaq9wo.pdf

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

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.

/pdf/evaluation-of-lora-lpwan-technology-for-remote-health-and-56s75mh7df.pdf

Evaluation of LoRa LPWAN technology for remote health and wellbeing monitoring

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 m North to South and over 320 m 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.

/pdf/evaluation-of-lora-lpwan-technology-for-indoor-remote-health-2e3z9604qz.pdf

Evaluation of LoRa LPWAN Technology for Indoor Remote Health and Wellbeing Monitoring

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.

Juha Petajajarvi

Papers

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

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

Evaluation of LoRa LPWAN technology for remote health and wellbeing monitoring

Evaluation of LoRa LPWAN Technology for Indoor Remote Health and Wellbeing Monitoring

On LoRaWAN Scalability: Empirical Evaluation of Susceptibility to Inter-Network Interference