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Journal ArticleDOI

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

TL;DR: This is the first academic study discussing LoRa mesh networking in detail and evaluating its performance via real experiments, and it is shown that in urban areas, LoRa requires dense deployment of LoRa gateways to ensure that indoor LoRa devices can successfully transfer data back to remote GWs.
Abstract: 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.
Citations
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Journal ArticleDOI
TL;DR: The packet error ratio is determined based on the estimated PL parameters to evaluate the performance of P2P links, and despite the unfavorable radio propagation in the urban scenario and the densely forested terrain, a maximum range of 1 km is achieved.
Abstract: Low-power wide-area technologies have demonstrated their usefulness in a wide variety of Internet of Things applications. New applications are emerging, requiring a mesh or point-to-point (P2P) topology, in contrast to the conventional star-of-stars topology. In this article, we evaluate the coverage and model the path loss (PL) of these links, based on experimental campaigns in three environments: 1) urban; 2) forest; and 3) coastal. More obstructions, scattering, and diffraction are encountered because the terminals are typically at a low height. This results in a higher PL compared to the star-of-stars topology. Consequently, more packets drop below the receiver sensitivity. Realistic PL parameters are estimated by also taking the censored data into account. The packet error ratio is determined based on the estimated PL parameters to evaluate the performance of P2P links. Even in these adverse environments, 80% of the transmitted packets are successfully received at a distance of approximately 200 m. Moreover, a range of over 4 km is observed in the line-of-sight scenario. Despite the unfavorable radio propagation in the urban scenario and the densely forested terrain, a maximum range of 1 km is achieved.

63 citations

Journal ArticleDOI
31 Jul 2020-Sensors
TL;DR: This article provides a review of the state-of-the-art multihop proposals for LoRaWAN, and carried out a comparative analysis and classification, considering technical characteristics, intermediate devices function, and network topologies.
Abstract: The growth of the Internet of Things (IoT) led to the deployment of many applications that use wireless networks, like smart cities and smart agriculture. Low Power Wide Area Networks (LPWANs) meet many requirements of IoT, such as energy efficiency, low cost, large coverage area, and large-scale deployment. Long Range Wide Area Network (LoRaWAN) networks are one of the most studied and implemented LPWAN technologies, due to the facility to build private networks with an open standard. Typical LoRaWAN networks are single-hop in a star topology, composed of end-devices that transmit data directly to gateways. Recently, several studies proposed multihop LoRaWAN networks, thus forming wireless mesh networks. This article provides a review of the state-of-the-art multihop proposals for LoRaWAN. In addition, we carried out a comparative analysis and classification, considering technical characteristics, intermediate devices function, and network topologies. This paper also discusses open issues and future directions to realize the full potential of multihop networking. We hope to encourage other researchers to work on improving the performance of LoRaWAN mesh networks, with more theoretical and simulation analysis, as well as practical deployments.

61 citations


Cites background or methods from "Monitoring of Large-Area IoT Sensor..."

  • ...However, many of the recent multihop proposals do not deal with energy issues, like the ones presented in [18,23,24]....

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  • ...The work in [23] proposed a routing protocol over a LoRa physical layer based on a child-list to create routes....

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  • ...[29] Router-Device Single Yes Yes Lee and Ke [23] Router-Device Single No Yes Liao et al....

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  • ...[29] LoRa x general Huh and Kim [55] LoRaWAN x urban/industrial Kim and Jang [56] LoRaWAN x general Lee and Ke [23] LoRa x University Campus Liao et al....

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Journal ArticleDOI
TL;DR: In this paper, the authors analyzed the cross-correlation between the transmitted waveforms and showed that LoRa can be considered approximately an orthogonal modulation only for large $M$.
Abstract: An important modulation technique for Internet of Things (IoT) is the one proposed by the low power long range (LoRa) alliance. 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.

59 citations

Journal ArticleDOI
TL;DR: In this article, the authors presented an application of the Internet-of-Things for model-based evaluation of micro-climate parameters inside two greenhouse crop production systems, where they developed a comfort ratio model, and a custom-built wireless sensor for data fusion in order to evaluate and compare microclimate parameters in two different tropical greenhouses prior to the actual cultivation of tomato.

56 citations

Journal ArticleDOI
TL;DR: An Internet of Things (IoT)-based intelligent fish farming and tracking control system that includes a forecasting method that enables automatic water quality management and supports tracking the breeding and selling of freshwater fish is developed.

56 citations

References
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Proceedings ArticleDOI
N. Abramson1
17 Nov 1970
TL;DR: A remote-access computer system under development as part of a research program to investigate the use of radio communications for computer-computer and console-computer links and a novel form of random-access radio communications developed for use within THE ALOHA SYSTEM is described.
Abstract: In September 1968 the University of Hawaii began work on a research program to investigate the use of radio communications for computer-computer and console-computer links. In this report we describe a remote-access computer system---THE ALOHA SYSTEM---under development as part of that research program and discuss some advantages of radio communications over conventional wire communications for interactive users of a large computer system. Although THE ALOHA SYSTEM research program is composed of a large number of research projects, in this report we shall be concerned primarily with a novel form of random-access radio communications developed for use within THE ALOHA SYSTEM.

2,297 citations


"Monitoring of Large-Area IoT Sensor..." refers methods in this paper

  • ...The PDR could fall even further if nodes are allowed to send data actively (such as in the ALOHA protocol in LoRaWAN approach)....

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  • ...If nodes are allowed to send data actively, without waiting for a data request from the GW, as in the ALOHA LoRaWAN approach, packet collision may decrease PDR in the event that many nodes send data simultaneously....

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  • ...The design and drawbacks of LoRaWAN are similar to those of the ALOHA [17] protocol, as there is no mechanism to arbitrate access to a shared wireless frequency....

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Journal ArticleDOI
09 Sep 2016-Sensors
TL;DR: An overview of LoRa and an in-depth analysis of its functional components are provided and some possible solutions for performance enhancements are proposed.
Abstract: 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.

1,126 citations


"Monitoring of Large-Area IoT Sensor..." refers methods or result in this paper

  • ...The time-related performance of LoRa and LoRaWAN was also evaluated [16] to determine the uncertainty of schedule to transmission and long-term clock stability....

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  • ...In a study of how SF affects receiver sensitivity in LoRa and LoRaWAN [13], researchers used a Semtech SX1276 Mbed shield as the end device and a Cisco 910 industrial router as the GW....

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  • ...This result indicates that the one-hop LoRa network does not perform well for indoor nodes, which again confirmed the analysis of [11]–[13]....

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  • ...In a study of how SF affects receiver sensitivity in LoRa and LoRaWAN [13], researchers used a Semtech SX1276 Mbed...

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  • ...We can compare this drawback to singlehop LoRaWAN systems, which suffer from low PDR with a high density of LoRa devices, as mentioned in [13]....

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Journal ArticleDOI
TL;DR: This article introduces a new type of wireless connectivity, characterized by low-rate, long-range transmission technologies in the unlicensed sub-gigahertz frequency bands, used to realize access networks with star topology referred to as low-power WANs (LPWANs).
Abstract: Connectivity is probably the most basic building block of the IoT paradigm. Up to now, the two main approaches to provide data access to things have been based on either multihop mesh networks using short-range communication technologies in the unlicensed spectrum, or long-range legacy cellular technologies, mainly 2G/GSM/GPRS, operating in the corresponding licensed frequency bands. Recently, these reference models have been challenged by a new type of wireless connectivity, characterized by low-rate, long-range transmission technologies in the unlicensed sub-gigahertz frequency bands, used to realize access networks with star topology referred to as low-power WANs (LPWANs). In this article, we introduce this new approach to provide connectivity in the IoT scenario, discussing its advantages over the established paradigms in terms of efficiency, effectiveness, and architectural design, particularly for typical smart city applications.

842 citations


"Monitoring of Large-Area IoT Sensor..." refers background in this paper

  • ...Increasing the spreading factor (SF) of LoRa PHY to 12 can significantly extend the communication range by increasing the receiver sensitivity [9], but the drawback is that doing so can lower the data throughput rate and cause more severe data collision due to the longer times required for transmission....

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Posted Content
TL;DR: In this paper, the authors introduce a new approach to provide connectivity in the IoT scenario, discussing its advantages over the established paradigms in terms of efficiency, effectiveness, and architectural design, in particular for the typical Smart Cities applications.
Abstract: Connectivity is probably the most basic building block of the Internet of Things (IoT) paradigm. Up to know, the two main approaches to provide data access to the \emph{things} have been based either on multi-hop mesh networks using short-range communication technologies in the unlicensed spectrum, or on long-range, legacy cellular technologies, mainly 2G/GSM, operating in the corresponding licensed frequency bands. Recently, these reference models have been challenged by a new type of wireless connectivity, characterized by low-rate, long-range transmission technologies in the unlicensed sub-GHz frequency bands, used to realize access networks with star topology which are referred to a \emph{Low-Power Wide Area Networks} (LPWANs). In this paper, we introduce this new approach to provide connectivity in the IoT scenario, discussing its advantages over the established paradigms in terms of efficiency, effectiveness, and architectural design, in particular for the typical Smart Cities applications.

748 citations

Proceedings ArticleDOI
01 Dec 2015
TL;DR: This work studies the coverage of the recently developed LoRa LPWAN technology via real-life measurements and presents a channel attenuation model derived from the measurement data that can be used to estimate the path loss in 868 MHz ISM band in an area similar to Oulu, Finland.
Abstract: 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.

593 citations


"Monitoring of Large-Area IoT Sensor..." refers background in this paper

  • ...To test long-range outdoor transmission, Petäjäjärvi and colleagues [14] installed a LoRa node on the roof rack of a car and another on the radio mast of a boat....

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