Journal ArticleDOI

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

27 Mar 2018--Vol. 67, Iss: 9, pp 2177-2187

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.
Topics: , Mesh networking (56%), Wireless sensor network (52%)
##### Citations
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Journal ArticleDOI
16 Nov 2018-Sensors
TL;DR: A detailed description of the technology is given, including existing security and reliability mechanisms, and a strengths, weaknesses, opportunities and threats (SWOT) analysis is presented along with the challenges that LoRa and LoRaWAN still face.
Abstract: 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.

182 citations

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

• ...The tested setup employed only 19 nodes in total deployed indoor and outdoor in an area of 800 m by 600 m [19]....

[...]

• ...[12] Medical • • [13] Medical • • • [14] Agriculture [15] Agriculture • [16] Agriculture • [17] Agriculture • [18] Sensor Networks • • [19] Sensor Networks • [20] Traffic Monitoring • • [23] Localization • [26] Tele-metering • • [28] Smart Grid [24] Smart City • •...

[...]

• ...Lee and Ke [19] focused in mesh communication for LoRa nodes by introducing a system architecture where the gateway is the central sink....

[...]

• ...LoRaWAN is used for different application types ranging from health and wellbeing monitoring [12,13], agriculture monitoring [14–17], wireless sensor networks [18,19], traffic monitoring [20], localization [21–23], smart city applications [24] up to smart grids and tele-measurements [25–28]....

[...]

• ...It is shown that in such a network topology the PDR for end nodes far away from gateway will improve, for some nodes from 0% to 91% [19]....

[...]

Journal ArticleDOI
Marco Chiani1, Ahmed Elzanaty1Institutions (1)
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
30 Apr 2019-IEEE Access
TL;DR: Test results show that the synchronous LoRa mesh network approach clearly outperforms the standard LoRaWAN technique with regard to the reliability of packet delivery when transmitting from range-critical locations, which is expected to generally ease data collection from difficult-to-access locations such as underground areas.
Abstract: Collecting precise real-time information on urban drainage system performance is essential to identify, predict, and manage critical loading situations, such as urban flash floods and sewer overflows. Although emerging low-power wireless communication techniques allow efficient data transfers with great above-ground performance, for underground or indoor applications in a large coverage range are difficult to achieve due to physical and topological limitations, particularly in dense urban areas. In this paper, we first discuss the range limitations of the LoRaWAN standard based on a systematic evaluation of a long-term operation of a sensor network monitoring in-sewer process dynamics. Analyses reveal an-on average-five-fold higher data packet loss for sub-surface nodes, which steadily grows with increasing distance to the gateway. Second, we present a novel LPWAN concept based on the LoRaR technology that enhances transmission reliability, efficiency, and flexibility in range-critical situations through meshed multi-hop routing and ensures a precise time-synchronization through optional GPS or DCF77 long-wave time signaling. Third, we illustrate the usefulness of the newly developed concept by evaluating the radio transmission performance for two independent full-scale field tests. Test results show that the synchronous LoRa mesh network approach clearly outperforms the standard LoRaWAN technique with regard to the reliability of packet delivery when transmitting from range-critical locations. Hence, the approach is expected to generally ease data collection from difficult-to-access locations such as underground areas.

43 citations

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

• ...Recently, Lee and Ke [22] proposed a mesh network approach to overcome low packet delivery ratios (PDRs)....

[...]

Journal ArticleDOI
23 Oct 2019-Applied Sciences
TL;DR: This article reviews the state of the start on the application of the latest key technologies for the development of smart campuses and universities, and defines the essential characteristics of a smart campus/university and the latest communications architectures and technologies.
Abstract: Smart campuses and smart universities make use of IT infrastructure that is similar to the one required by smart cities, which take advantage of Internet of Things (IoT) and cloud computing solutions to monitor and actuate on the multiple systems of a university. As a consequence, smart campuses and universities need to provide connectivity to IoT nodes and gateways, and deploy architectures that allow for offering not only a good communications range through the latest wireless and wired technologies, but also reduced energy consumption to maximize IoT node battery life. In addition, such architectures have to consider the use of technologies like blockchain, which are able to deliver accountability, transparency, cyber-security and redundancy to the processes and data managed by a university. This article reviews the state of the start on the application of the latest key technologies for the development of smart campuses and universities. After defining the essential characteristics of a smart campus/university, the latest communications architectures and technologies are detailed and the most relevant smart campus deployments are analyzed. Moreover, the use of blockchain in higher education applications is studied. Therefore, this article provides useful guidelines to the university planners, IoT vendors and developers that will be responsible for creating the next generation of smart campuses and universities.

42 citations

Journal ArticleDOI
Andrea Abrardo1, Alessandro Pozzebon1Institutions (1)
19 Jan 2019-Sensors
TL;DR: An ad-hoc transmission scheme is presented that optimally evaluates the wake-up time of all nodes with the aim of minimizing the average energy dissipation deriving from clock offsets, and results show that the proposed wake- up time optimization leads in the best case to a 50% reduction in power dissipation.
Abstract: In this paper, a pervasive monitoring system to be deployed in underground environments is presented. The system has been specifically designed for the so-called "Bottini", i.e., the medieval aqueducts dug beneath the Centre of Siena, Italy. The results of a measurement campaign carried out in the deployment scenario show that the transmission range of LoRa (Long Range) technology is limited to a maximum of 200 m, thus, making the adoption of a classical star topology impossible. Hence, a Linear Sensor Network topology is proposed based on multi-hop LoRa chain-type communications. In this scenario, an ad-hoc transmission scheme is presented that optimally evaluates the wake-up time of all nodes with the aim of minimizing the average energy dissipation deriving from clock offsets. Numerical results show that the proposed wake-up time optimization leads in the best case to a 50% reduction in power dissipation with respect to a scheme that evaluates the wake-up time in a non-optimal way.

39 citations

##### References
More filters

Proceedings ArticleDOI
N. Abramson1Institutions (1)
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.

2,177 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)....

[...]

• ...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....

[...]

• ...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....

[...]

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.

864 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....

[...]

• ...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....

[...]

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

[...]

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

[...]

• ...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]....

[...]

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.

721 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....

[...]

Posted Content
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.

659 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.

466 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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