LoRaWAN is one of the low power wide area network (LPWAN) technologies that have received significant attention by the research community in the recent years. It offers low-power, low-data rate communication over a wide range of covered area. In the past years, the number of publications regarding LoRa and LoRaWAN has grown tremendously. This paper provides an overview of research work that has been published from 2015 to September 2018 and that is accessible via Google Scholar and IEEE Explore databases. First, a detailed description of the technology is given, including existing security and reliability mechanisms. This literature overview is structured by categorizing papers according to the following topics: (i) physical layer aspects; (ii) network layer aspects; (iii) possible improvements; and (iv) extensions to the standard. Finally, a strengths, weaknesses, opportunities and threats (SWOT) analysis is presented along with the challenges that LoRa and LoRaWAN still face.

https://biblio.ugent.be/publication/8586331/file/8586357.pdf

A Survey of LoRaWAN for IoT: From Technology to Application

Although many techniques exist to transfer data from the widely distributed sensors that make up the Internet of Things (IoT) (e.g., using 3G/4G networks or cables), these methods are associated with prohibitively high costs, making them impractical for real-life applications. Recently, several emerging wireless technologies have been proposed to provide long-range communication for IoT sensors. Among these, LoRa has been examined for long-range performance. Although LoRa shows good performance for long-range transmission in the countryside, its radio signals can be attenuated over distance, and buildings, trees, and other radio signal sources may interfere with the signals. Our observations show that in urban areas, LoRa requires dense deployment of LoRa gateways (GWs) to ensure that indoor LoRa devices can successfully transfer data back to remote GWs. Wireless mesh networking is a solution for increasing communication range and packet delivery ratio (PDR) without the need to install additional GWs. This paper presents a LoRa mesh networking system for large-area monitoring of IoT applications. We deployed 19 LoRa mesh networking devices over an $800\,\,\text {m} \times 600$ m area on our university campus and installed a GW that collected data at 1-min intervals. The proposed LoRa mesh networking system achieved an average 88.49% PDR, whereas the star-network topology used by LoRa achieved only 58.7% under the same settings. To the best of our knowledge, this is the first academic study discussing LoRa mesh networking in detail and evaluating its performance via real experiments.

Monitoring of Large-Area IoT Sensors Using a LoRa Wireless Mesh Network System: Design and Evaluation

Geologic hazards (geohazards) are naturally occurring or human-activity-induced geologic conditions capable of causing damage or loss of property and/or life. geohazards, such as landslides, surface subsidence, and earthquakes, can seriously affect and threaten life, property, or public safety. geohazards prevention is the application of geologic engineering principles and existing and emerging technologies to reduce, minimize, or prevent the effects of various geologic hazards. Monitoring and early warning are the most common strategies for geohazards prevention. With the development of the Internet of Things (IoT), an emerging new idea is to apply IoT technology to enhance the accuracy and efficiency of monitoring and early warning systems for geohazards prevention. This article aims to present a comprehensive survey of relevant research and technological developments of the IoT applied in geohazards prevention. It first surveys the applications of the IoT in the monitoring and early warning of seven types of common geohazards, including landslides, debris flow, rockfall, surface subsidence, surface collapse, surface cracks, and earthquakes, then investigates the key technologies in geohazards prevention when utilizing the IoT, and finally summarizes the challenges in IoT-based monitoring and early warning systems for geohazards prevention. Moreover, this article also highlights the future directions for employing the IoT for geohazards prevention.

A Survey of Internet of Things (IoT) for Geohazard Prevention: Applications, Technologies, and Challenges

To reach the goal of sustainable agriculture, smart farming is taking advantage of the Unmanned Aerial Vehicles (UAVs) and Internet of Things (IoT) paradigm. These smart farms are designed to be run by interconnected devices and vehicles. Some enormous potentials can be achieved by the integration of different IoT technologies to achieve automated operations with minimum supervision. This paper outlines some major applications of IoT and UAV in smart farming, explores the communication technologies, network functionalities and connectivity requirements for Smart farming. The connectivity limitations of smart agriculture and it’s solutions are analysed with two case studies. In case study-1, we propose and evaluate meshed Long Range Wide Area Network (LoRaWAN) gateways to address connectivity limitations of Smart Farming. While in case study-2, we explore satellite communication systems to provide connectivity to smart farms in remote areas of Australia. Finally, we conclude the paper by identifying future research challenges on this topic and outlining directions to address those challenges.

https://www.mdpi.com/2071-1050/13/4/1821/pdf

A Review of Applications and Communication Technologies for Internet of Things (IoT) and Unmanned Aerial Vehicle (UAV) Based Sustainable Smart Farming

An important modulation technique for Internet of Things (IoT) is the one proposed by the LoRa allianceTM. In this paper we analyze the M-ary LoRa modulation in the time and frequency domains. First, we provide the signal description in the time domain, and show that LoRa is a memoryless continuous phase modulation. The cross-correlation between the transmitted waveforms is determined, proving that LoRa can be considered approximately an orthogonal modulation only for large M. Then, we investigate the spectral characteristics of the signal modulated by random data, obtaining a closed-form expression of the spectrum in terms of Fresnel functions. Quite surprisingly, we found that LoRa has both continuous and discrete spectra, with the discrete spectrum containing exactly a fraction 1/M of the total signal power.

/pdf/on-the-lora-modulation-for-iot-waveform-properties-and-46etr00fhh.pdf

On the LoRa Modulation for IoT: Waveform Properties and Spectral Analysis

Power consumption is one of the major issues associated with deploying a wireless sensor to monitor natural environments in the real world. It is not practical to frequently replace the battery of a sensor that is located in a remote mountainous area. While considering to save valuable energy, the sensor must be able to detect a particular event in a timely manner and report data. To satisfy these requirements, in this paper, we present a wireless sensor system, termed SMARTCONE, which is designed to monitor the slope movement and minimize the standby power consumption, while remaining active to detect events. Multiple SMARTCONEs need to synchronously change their operation modes to collect the physical parameters and transmit raw vibration data simultaneously. SMARTCONE is consuming a power of only 0.05 mA at 3.6 V in standby mode, which is significantly less than that consumed by the previous design. As far as we know, SMARTCONE is an unprecedented instrument for the monitoring of slope movement; no other instruments can achieve such a low-energy consumption while being triggered by external vibration and managed remotely. These complicated issues are considered while designing the SMARTCONE, whose performance is then evaluated. In order to prevent redundant effort and to reduce the entry-level knowledge required by the users who wish to design a system, and to promote the use of this design for monitoring natural environments, we would like to open source the design of SMARTCONE for the public. It can be modified for use in other applications to satisfy their requirements without the need to build from scratch.

Open-Source Wireless Sensor System for Long-Term Monitoring of Slope Movement

LoRa, an emerging wireless technology, is examined for long range communication performance in a large area. Although LoRa shows good performance for long-distance transmission in the countryside, its radio signals can be attenuated and interfered with by buildings, trees and other signal sources. In urban areas, our observation shows that LoRa requires a dense deployment of LoRa gateways to ensure that indoor LoRa devices can transfer data back to remote servers. Mesh networking is a solution for increasing the communication range and packet delivery ratio without the need to install additional LoRa gateways. This study presents our design of a LoRa mesh-networking module for IoT applications (e.g.,collecting data from multiple, widely distributed sensors on a university campus). We deployed 19 LoRa mesh-networking devices distributed in an 800m by 600m area on campus to serve as a gateway and to collect data at one-minute intervals. The results show our LoRa mesh networking module achieved a 88.49% packet delivery ratio (PDR), while the LoRaWAN in star-network topology was only 58.7% under the same conditions.

A LoRa wireless mesh networking module for campus-scale monitoring: demo abstract

Demo Abstract: A LoRa Wireless Mesh Networking Module for Campus-Scale Monitoring

The one of the major difficulties in deploying a wireless sensor to monitor debris flow in the real world is power consumption. Frequently replacing the battery of a sensor that is located in a remote mountainous area is not practical. In this study we examine the newly-introduced wireless debris flow sensor, SMARTCONE, which is designed to minimize the standby power consumption, but still keep alert to detecting debris flow. During standby periods, SMARTCONE turns off all major components and uses an accelerometer to sense vibration generated by moving debris flow, and it wakes up SMARTCONE for collecting the parameters of a moving debris flow. Multiple SMARTCONEs need to change operation modes between standby and wake up, collect physical parameters, and transmit data simultaneously, and these issues are kept in mind while designing the system. The performance of vibration detection, data transmission and records of GPS trajectories are evaluated to ensure the accuracy of the design.

Kai-Hsiang Ke

Papers

Monitoring of Large-Area IoT Sensors Using a LoRa Wireless Mesh Network System: Design and Evaluation

Open-Source Wireless Sensor System for Long-Term Monitoring of Slope Movement

A LoRa wireless mesh networking module for campus-scale monitoring: demo abstract

Demo Abstract: A LoRa Wireless Mesh Networking Module for Campus-Scale Monitoring

Poster Abstract: An Extremely Long Standby Time Wireless Sensor System for Debris Flow Monitoring