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Low-Power Sensors and Systems for IoT
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Low-Power Sensors and Systems for IoT

A special issue of Sensors (ISSN 1424-8220). This special issue belongs to the section "Internet of Things".

Deadline for manuscript submissions: closed (31 July 2020) | Viewed by 79324

Special Issue Editors

Prof. Dr. Ramon Gonzalez Carvajal

E-Mail Website
Guest Editor
Department of Electronics Engineering, University of Seville, 41092 Seville, Spain
Interests: low voltage; low power analog circuit design; embedded systems; wireless sensor networks; IoT
Special Issues, Collections and Topics in MDPI journals
Prof. Dr. Antonio J. Lopez-Martin

E-Mail Website
Guest Editor
Department of Electrical, Electronic and Communications Engineering, Public University of Navarra, Campus Arrosadia, 31006 Pamplona, Spain
Interests: microelectronic design; wireless communications, signal processing and instrumentation
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

The Internet of Things (IoT) paradigm is envisaged as one of the most disruptive concepts in the near future, with large technological, societal and economic impacts. Massive IoT applications involve a large number of low-cost devices, often portable/wearable, with sensing and wireless transmission capabilities. They often transmit small data volumes and have stringent energy consumption requirements. Some of these applications are smart health, smart metering, transportation fleet management, smart buildings, monitoring of large infrastructures or industrial plants, agriculture or natural ecosystems.

This Special Issue solicits innovative contributions from both industry and academia in the rapidly growing area of low power sensors and systems for IoT. The sensing devices demanded by IoT applications cover a wide range, including optical, acoustic, chemical, physical and electrical devices. Low power, energy-efficient circuit and system design techniques for sensor data collection, processing as well as wireless communications will be the focus of this Special Issue. Hence contributions may include, but are not limited to device, circuit and system level techniques.

Prof. Dr. Ramon Gonzalez Carvajal
Prof. Dr. Antonio J. Lopez-Martin
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Sensors is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2600 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Low power sensors for the Internet of Things (IoT)
  • Circuit and system level design for wireless sensor nodes
  • Low power design for the Internet of Things (IoT)
  • Energy harvesting and power management for the Internet of Things (IoT)
  • Experiences from low-power IoT testbeds and field-trials

Published Papers (18 papers)

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24 pages, 5615 KiB  
Article
LoRa-Based Traffic Flow Detection for Smart-Road
by David Asiain and Diego Antolín
Sensors 2021, 21(2), 338; https://doi.org/10.3390/s21020338 - 06 Jan 2021
Cited by 12 | Viewed by 4803
Abstract
This paper presents a wireless traffic flow detection system, mainly focused on conditions in which the traffic flow is slow or stopped, which increases the risk of highway accidents. To achieve this goal, a Low Power Wide Area Network (LPWAN) based on LoRa [...] Read more.
This paper presents a wireless traffic flow detection system, mainly focused on conditions in which the traffic flow is slow or stopped, which increases the risk of highway accidents. To achieve this goal, a Low Power Wide Area Network (LPWAN) based on LoRa called Short LoRa has been developed. This LoRa sub-network complies with the European Telecommunications Standards Institute (ETSI) harmonized standard for its compatibility in Europe countries. In addition, the development of the devices has allowed them to also work on a LoRaWAN network. The introduced development has been compared to a reference system mounted with laser barriers that provided a high accurate comparison. Field tests of the system have been carried out and the data obtained in the measurement has been analyzed with two different methods, and both of them were valid for the application. The results can determine vehicle speed with adequate precision at low speeds. The attenuating behavior of the communication signal is also analyzed through the Radio Signal Strength Indicator (RSSI). The relationship between vehicle speed, gate distances and RSSI attenuation has been studied. The system is proven to have efficient results in detecting traffic flow under the conditions for which it has been developed. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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22 pages, 16470 KiB  
Article
Energy Consumption Analysis of LPWAN Technologies and Lifetime Estimation for IoT Application
by Ritesh Kumar Singh, Priyesh Pappinisseri Puluckul, Rafael Berkvens and Maarten Weyn
Sensors 2020, 20(17), 4794; https://doi.org/10.3390/s20174794 - 25 Aug 2020
Cited by 66 | Viewed by 8139
Abstract
The spectrum of Internet of Things (IoT) applications is exponentially growing, driving the demand for better energy performance metrics. In conjunction, Low Power Wide Area Networks (LPWAN) have evolved as long-range connectivity enabler with low management cost. The integration of LPWAN communication assists [...] Read more.
The spectrum of Internet of Things (IoT) applications is exponentially growing, driving the demand for better energy performance metrics. In conjunction, Low Power Wide Area Networks (LPWAN) have evolved as long-range connectivity enabler with low management cost. The integration of LPWAN communication assists in reliable IoT operation with extended lifetime. Notable LPWAN technologies that contend for many of the IoT applications are LoRaWAN, DASH7, Sigfox, and NB-IoT. Most of the end-devices such as sensors and actuators are battery powered, therefore investigating energy consumption becomes crucial. To estimate the consumed power, it is important to analyze the energy consumption in wireless communication. This paper describes an empirical evaluation of energy consumption for LPWAN wireless technologies. We measure the current consumption of LoRaWAN, DASH7, Sigfox, and NB-IoT and derive the respective battery lifetime. These measurements help to quantify the energy performance of different protocols. We observe that LoRaWAN and DASH7 are more energy efficient when compared to Sigfox and NB-IoT. Finally, a case study on energy consumption is done on precision agriculture in the greenhouse, showing that battery lifetime in real applications can drop significantly from the ideal case. These results can be used for increasing the effectiveness of the IoT application by selecting the right technology and battery capacity. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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15 pages, 3642 KiB  
Article
An IoT Smart Rodent Bait Station System Utilizing Computer Vision
by Robert Ross, Lyle Parsons, Ba Son Thai, Richard Hall and Meha Kaushik
Sensors 2020, 20(17), 4670; https://doi.org/10.3390/s20174670 - 19 Aug 2020
Cited by 10 | Viewed by 5188
Abstract
Across the world billions of dollars of damage are attributed to rodents, resulting in them being classified collectively as the biggest animal pest in the world. At a commercial scale most pest control companies employ the labour intensive approach of deploying and manually [...] Read more.
Across the world billions of dollars of damage are attributed to rodents, resulting in them being classified collectively as the biggest animal pest in the world. At a commercial scale most pest control companies employ the labour intensive approach of deploying and manually monitoring rodenticide bait stations. In this paper was present, RatSpy, a visual, low-power bait station monitoring system which wirelessly reports both on bait station levels and intruders entering the bait station. The smart bait stations report data back to a custom designed cloud platform. The system performance was evaluated under realistic field conditions (on an active cattle farm) with initial results showing significant potential in terms of reducing manual labour, improving scalability and data. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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22 pages, 967 KiB  
Article
Ambient Backscattering-Enabled SWIPT Relaying System with a Nonlinear Energy Harvesting Model
by Thu L. N. Nguyen, Jin-Young Kim and Yoan Shin
Sensors 2020, 20(16), 4534; https://doi.org/10.3390/s20164534 - 13 Aug 2020
Cited by 4 | Viewed by 2047
Abstract
Since radio frequency (RF) signals can be used for both information transmission and energy harvesting, RF-based energy harvesting is capable of integrating with other existing communication techniques for providing better rate–energy tradeoff and quality-of-service. Within the context of an RF-based energy harvesting relaying [...] Read more.
Since radio frequency (RF) signals can be used for both information transmission and energy harvesting, RF-based energy harvesting is capable of integrating with other existing communication techniques for providing better rate–energy tradeoff and quality-of-service. Within the context of an RF-based energy harvesting relaying network, a relay node not only acts as an intermediate node to help the delivery from source to destination, but also harvests energy from an RF dedicated source to prolong its lifetime. Thus, it brings diversity gain and coverage extension as well as provides extra energy for data transmission. This paper investigates a system that enables ambient backscattering communication-assisted simultaneous wireless information and power transfer at the relay. In the proposed system, a backscatter device plays a role as a relay to meet sustainable network coverage and to harvest ambient energy as well. With a power splitting (PS) scheme, we first investigate a nonlinear energy harvesting model at the relay node. In order to adapt to the channel gains, a dynamic PS ratio is required to perform well in changing environments. Moreover, we derive mathematical expressions for the outage probability and the achievable system throughput. Numerical results show the effects of various system parameters on the outage probability and the system throughput performance. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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16 pages, 2672 KiB  
Article
Energy Consumption Evaluation of a Routing Protocol for Low-Power and Lossy Networks in Mesh Scenarios for Precision Agriculture
by Frederico O. Sales, Yelco Marante, Alex B. Vieira and Edelberto Franco Silva
Sensors 2020, 20(14), 3814; https://doi.org/10.3390/s20143814 - 08 Jul 2020
Cited by 11 | Viewed by 2361
Abstract
Sensor nodes are small, low-cost electronic devices that can self-organize into low-power networks and are susceptible to data packet loss, having computational and energy limitations. These devices expand the possibilities in many areas, like agriculture and urban spaces. In this work, we consider [...] Read more.
Sensor nodes are small, low-cost electronic devices that can self-organize into low-power networks and are susceptible to data packet loss, having computational and energy limitations. These devices expand the possibilities in many areas, like agriculture and urban spaces. In this work, we consider an IoT environment for monitoring a coffee plantation in precision agriculture. We investigate the energy consumption under low-power and lossy networks considering three different network topologies and an Internet Engineering Task Force (IETF) standardized Low-power and Lossy Network (LLN) routing protocol, the Routing Protocol for LLNs (RPL). For RPL, each secondary node selects a better parent according to some Objective Functions (OFs). We conducted simulations using Contiki Cooja 3.0, where we considered the Expected Transmission Count (ETX) and hop-count metric (HOP) metrics to evaluate energy consumption for three distinct topologies: tree, circular, and grid. The simulation results show that the circular topology had the best (lowest) energy consumption, being 15% better than the grid topology and 30% against the tree topology. The results help the need to improve the evolution of RPL metrics and motivate the network management of the topology. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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21 pages, 1070 KiB  
Article
Energy-Efficient Cluster Management Using a Mobile Charger for Solar-Powered Wireless Sensor Networks
by Youngjae Son, Minjae Kang, Younghyun Kim, Ikjune Yoon and Dong Kun Noh
Sensors 2020, 20(13), 3668; https://doi.org/10.3390/s20133668 - 30 Jun 2020
Cited by 12 | Viewed by 3001
Abstract
In solar-powered wireless sensor networks (SP-WSNs), sensor nodes can continuously harvest energy to relieve the energy constraint problem in battery-powered WSNs. With the advent of wireless power transmission (WPT) technology, the nodes can be charged remotely if the energy harvested is insufficient. However, [...] Read more.
In solar-powered wireless sensor networks (SP-WSNs), sensor nodes can continuously harvest energy to relieve the energy constraint problem in battery-powered WSNs. With the advent of wireless power transmission (WPT) technology, the nodes can be charged remotely if the energy harvested is insufficient. However, even in SP-WSNs with WPT, an energy imbalance problem is observed, in which the energy consumption of the nodes around a sink node increases abnormally if the sink node is stationary. To solve this problem, recent studies have been conducted using a mobile sink node instead of a stationary one. Generally, a clustering scheme is used for the efficient utilization of a mobile sink. However, even in the case of mobile sinks, it is still necessary to minimize the energy burden of the cluster heads and their surrounding nodes. In this study, we propose a scheme that mitigates the energy imbalance problem of SP-WSNs by using a WPT-capable mobile sink and an efficient clustering scheme. In the proposed scheme, the energy imbalance is minimized by electing the cluster heads effectively after considering the energy state of the nodes, and by enabling the sink node to charge the energy of the cluster heads while collecting data from them. Consequently, this scheme allows the sink node to collect more data with fewer blackouts of the sensor nodes. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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28 pages, 3878 KiB  
Article
Low-Cost Conversion of Single-Zone HVAC Systems to Multi-Zone Control Systems Using Low-Power Wireless Sensor Networks
by Julio Antonio Jornet-Monteverde and Juan José Galiana-Merino
Sensors 2020, 20(13), 3611; https://doi.org/10.3390/s20133611 - 27 Jun 2020
Cited by 6 | Viewed by 4218
Abstract
This paper presents a novel approach to convert a conventional house air conditioning installation into a more efficient system that individually controls the temperature of each zone of the house through Wi-Fi technology. Each zone regulates the air flow depending on the detected [...] Read more.
This paper presents a novel approach to convert a conventional house air conditioning installation into a more efficient system that individually controls the temperature of each zone of the house through Wi-Fi technology. Each zone regulates the air flow depending on the detected temperature, providing energy savings and increasing the machine performance. Therefore, the first step was to examine the communication bus of the air conditioner and obtain the different signal codes. Thus, an alternative Controller module has been designed and developed to control and manage the requests on the communication bus (Bus–Wi-Fi gateway). A specific circuit has been designed to adapt the signal of the serial port of the Controller with the communication bus. For the acquisition of the temperature and humidity data in each zone, a Node module has been developed, which communicates with the Controller through the Wi-Fi interface using the Message Queuing Telemetry Transport (MQTT) protocol with Secure Sockets Layer / Transport Layer Security (SSL/TLS) certificates. It has been equipped with an LCD touch screen as a human-machine interface. The Controller and the Node modules have been developed with the ultra-low power consumption CC3200 microController of Texas Instruments and the code has been implemented under the TI-RTOS real-time operating system. An additional module based on the Raspberry Pi computer has been designed to create the Wi-Fi network and implement the required network functionalities. The developed system not only ensures that the temperature in each zone is the desired one, but also controls the fan velocity of the indoor unit and the opening area of the vent registers, which considerably improves the efficiency of the system. Compared with the single-zone system, the experiments carried out show energy savings between 75% and 94% when only one of the zones is selected, and 44% when the whole house is air-conditioned, in addition to considerably improving user comfort. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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18 pages, 2195 KiB  
Article
Performance Evaluation of UAV-Enabled LoRa Networks for Disaster Management Applications
by Omar A. Saraereh, Amer Alsaraira, Imran Khan and Peerapong Uthansakul
Sensors 2020, 20(8), 2396; https://doi.org/10.3390/s20082396 - 23 Apr 2020
Cited by 53 | Viewed by 5213
Abstract
In hostile and remote environments, such as mountains, forests or suburban areas, traditional communications may not be available, especially after a disaster, such as a flood, a forest fire or an earthquake. In these situations, the wireless networks may become congested or completely [...] Read more.
In hostile and remote environments, such as mountains, forests or suburban areas, traditional communications may not be available, especially after a disaster, such as a flood, a forest fire or an earthquake. In these situations, the wireless networks may become congested or completely disrupted and may not be adequate to support the traffic generated by rescuers. It is also considered as the key tool in Corona Virus (COVID-19) battle. Moreover, the conventional approaches with fixed gateways may not work either, and this might lead to decoding errors due to the large distance between mobile nodes and the gateway. To avoid the decoding errors and improve the reliability of the messages, we propose to use intermediate Unmanned Aerial Vehicles (UAVs) to transfer messages from ground-based Long Range (LoRa) nodes to the remote base station (BS). Specifically, this UAV-enabled LoRa architecture is based on the ad hoc WiFi network, wherein, UAVs act as relays for the traffic generated between LoRa nodes and BS. To make the architecture more efficient, a distributed topology control algorithm is also proposed for UAVs. The algorithm is based on virtual spring forces and movement prediction technique that periodically updates the UAV topology to adapt to the movement of the ground-based LoRa nodes that move on the surface. The simulation results show the feasibility of the proposed approach for packet reception rate and average delay quality of service (QoS) metrics. It is observed that the mechanisms implemented in a UAV-enabled LoRa network effectively help to improve the packet reception rate with nominal buffer delays. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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26 pages, 729 KiB  
Article
A Systematic Analysis of Narrowband IoT Quality of Service
by Andreas Philipp Matz, Jose-Angel Fernandez-Prieto, Joaquin Cañada-Bago and Ulrich Birkel
Sensors 2020, 20(6), 1636; https://doi.org/10.3390/s20061636 - 14 Mar 2020
Cited by 24 | Viewed by 8533
Abstract
Narrowband-IoT (NB-IoT) is part of a novel group of access technologies referred to as Low-Power Wide Area Networks (LPWANs), which provide energy-efficient and long-range network access to IoT devices. Although NB-IoT Release 13 has been deployed by Mobile Network Operators (MNO), detailed Quality [...] Read more.
Narrowband-IoT (NB-IoT) is part of a novel group of access technologies referred to as Low-Power Wide Area Networks (LPWANs), which provide energy-efficient and long-range network access to IoT devices. Although NB-IoT Release 13 has been deployed by Mobile Network Operators (MNO), detailed Quality of Service (QoS) evaluations in public networks are still rare. In this paper, systematic physical layer measurements are conducted, and the application layer performance is verified. Special consideration is given to the influence of the radio parameters on the application layer QoS. Additionally, NB-IoT is discussed in the context of typical smart metering use cases. The results indicate that NB-IoT meets most theoretical Third Generation Partnership Project (3GPP) design goals in a commercial deployment. NB-IoT provides a wide coverage by using signal repetitions, which improve the receiver sensitivity, but simultaneously increase the system latency. The maximum data rates are consistent over a wide range of coverage situations. Overall, NB-IoT is a reliable and flexible LPWAN technology for sensor applications even under challenging radio conditions. Four smart metering transmission categories are analyzed, and NB-IoT is verified to be appropriate for applications that are not latency sensitive. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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13 pages, 2934 KiB  
Article
An Adaptive Spreading Factor Selection Scheme for a Single Channel LoRa Modem
by Seungku Kim, Heonkook Lee and Sungho Jeon
Sensors 2020, 20(4), 1008; https://doi.org/10.3390/s20041008 - 13 Feb 2020
Cited by 48 | Viewed by 5225
Abstract
When the low power wide area network (LPWAN) was developed for the internet of things (IoT), it attracted significant attention. LoRa, which is one of the LPWAN technologies, provides low-power and long-range wireless communication using a frequency band under 1 GHz. A long-range [...] Read more.
When the low power wide area network (LPWAN) was developed for the internet of things (IoT), it attracted significant attention. LoRa, which is one of the LPWAN technologies, provides low-power and long-range wireless communication using a frequency band under 1 GHz. A long-range wide area network (LoRaWAN) provides a simple star topology network that is not scalable; it supports multi-data rates by adjusting the spreading factor, code rate, and bandwidth. This paper proposes an adaptive spreading factor selection scheme for corresponding spreading factors (SFs) between a transmitter and receiver. The scheme enables the maximum throughput and minimum network cost, using cheap single channel LoRa modules. It provides iterative SF inspection and an SF selection algorithm that allows each link to communicate at independent data rates. We implemented a multi-hop LoRa network and evaluated the performance of experiments in various network topologies. The adaptive spreading factor selection (ASFS) scheme showed outstanding end-to-end throughput, peaking at three times the performance of standalone modems. We expect the ASFS scheme will be a suitable technology for applications requiring high throughput on a multi-hop network. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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18 pages, 625 KiB  
Article
Performance Analysis of Addressing Mechanisms in Inter-Operable IoT Device with Low-Power Wake-Up Radio
by Taewon Song and Taeyoon Kim
Sensors 2019, 19(23), 5106; https://doi.org/10.3390/s19235106 - 21 Nov 2019
Cited by 4 | Viewed by 2319
Abstract
Internet of Things (IoT) technology is rapidly expanding the use of its application, from individuals to industries. Owing to this, the number of IoT devices has been exponentially increasing. Considering the massive number of the devices, overall energy consumption is becoming more serious. [...] Read more.
Internet of Things (IoT) technology is rapidly expanding the use of its application, from individuals to industries. Owing to this, the number of IoT devices has been exponentially increasing. Considering the massive number of the devices, overall energy consumption is becoming more serious. From this point of view, attaching low-power wake-up radio (WUR) to the devices can be one of the candidate solutions to deal with this problem. With WUR, IoT devices can go to sleep until WUR receives a wake-up signal, which enables a significant reduction of its power consumption. Meanwhile, one concern for WUR operation is the addressing mechanism, since operational efficiency of the wake-up feature can significantly vary depending on the addressing mechanism. We therefore introduce addressing mechanisms for IoT devices equipped with WUR and analyze their performances, such as elapsed time to wake up, false positive probability and power/energy consumption, to provide appropriate addressing mechanisms over practical environments for IoT devices with WUR. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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18 pages, 9149 KiB  
Article
ITERL: A Wireless Adaptive System for Efficient Road Lighting
by María García-Castellano, Juan Manuel González-Romo, Juan Antonio Gómez-Galán, Juan Pablo García-Martín, Antonio Torralba and Ventura Pérez-Mira
Sensors 2019, 19(23), 5101; https://doi.org/10.3390/s19235101 - 21 Nov 2019
Cited by 16 | Viewed by 4558
Abstract
This work presents the development and construction of an adaptive street lighting system that improves safety at intersections, which is the result of applying low-power Internet of Things (IoT) techniques to intelligent transportation systems. A set of wireless sensor nodes using the Institute [...] Read more.
This work presents the development and construction of an adaptive street lighting system that improves safety at intersections, which is the result of applying low-power Internet of Things (IoT) techniques to intelligent transportation systems. A set of wireless sensor nodes using the Institute of Electrical and Electronics Engineers (IEEE) 802.15.4 standard with additional internet protocol (IP) connectivity measures both ambient conditions and vehicle transit. These measurements are sent to a coordinator node that collects and passes them to a local controller, which then makes decisions leading to the streetlight being turned on and its illumination level controlled. Streetlights are autonomous, powered by photovoltaic energy, and wirelessly connected, achieving a high degree of energy efficiency. Relevant data are also sent to the highway conservation center, allowing it to maintain up-to-date information for the system, enabling preventive maintenance. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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24 pages, 1459 KiB  
Article
Power Efficient Random Access for Massive NB-IoT Connectivity
by Mamta Agiwal, Mukesh Kumar Maheshwari and Hu Jin
Sensors 2019, 19(22), 4944; https://doi.org/10.3390/s19224944 - 13 Nov 2019
Cited by 14 | Viewed by 4020
Abstract
Sensors enabled Internet of things (IoT) has become an integral part of the modern, digital and connected ecosystem. Narrowband IoT (NB-IoT) technology is one of its economical versions preferable when low power and resource limited sensors based applications are considered. One of the [...] Read more.
Sensors enabled Internet of things (IoT) has become an integral part of the modern, digital and connected ecosystem. Narrowband IoT (NB-IoT) technology is one of its economical versions preferable when low power and resource limited sensors based applications are considered. One of the major characteristics of NB-IoT technology is its offer of reliable coverage enhancement (CE) which is achieved by repeating the transmission of signals. This repeated transmission of the same signal challenges power saving in low complexity NB-IoT devices. Additionally, the NB-IoT devices are expected to suffer from congestion due to simultaneous random access procedures (RAPs) from an enormous number of devices. Multiple RAP reattempts would further reduce the power saving in NB-IoT devices. We propose a novel power efficient RAP (PE-RAP) for reducing power consumption of NB-IoT devices in a highly congested environment. The existing RAP do not differentiate the failures due to poor channel conditions or due to collision. After the RAP failure either due to collision or poor channel, the devices can apply power ramping or can transit to a higher CE level with higher repetition configuration. In the proposed PE-RAP, the NB-IoT devices can re-ascertain the channel conditions after an RAP attempt failure such that the impediments due to poor channel are reduced. The power increments and repetition enhancements are applied only when necessary. We probabilistically obtain the chances of RAP reattempts. Subsequently, we evaluate the average power consumption by devices in different CE levels for different repetition configurations. We validate our analysis by simulation studies. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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11 pages, 361 KiB  
Article
Bit Error Rate Closed-Form Expressions for LoRa Systems under Nakagami and Rice Fading Channels
by Claudio Ferreira Dias, Eduardo Rodrigues de Lima and Gustavo Fraidenraich
Sensors 2019, 19(20), 4412; https://doi.org/10.3390/s19204412 - 12 Oct 2019
Cited by 19 | Viewed by 3446
Abstract
We derive exact closed-form expressions for Long Range (LoRa) bit error probability and diversity order for channels subject to Nakagami-m, Rayleigh and Rician fading. Analytical expressions are compared with numerical results, showing the accuracy of our proposed exact expressions. In the [...] Read more.
We derive exact closed-form expressions for Long Range (LoRa) bit error probability and diversity order for channels subject to Nakagami-m, Rayleigh and Rician fading. Analytical expressions are compared with numerical results, showing the accuracy of our proposed exact expressions. In the limiting case of the Nakagami and Rice parameters, our bit error probability expressions specialize into the non-fading case. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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18 pages, 5896 KiB  
Article
A High-Voltage Energy-Harvesting Interface for Irregular Kinetic Energy Harvesting in IoT Systems with 1365% Improvement Using All-NMOS Power Switches and Ultra-low Quiescent Current Controller
by Hassan Saif, Muhammad Bilawal Khan, Jongmin Lee, Kyoungho Lee and Yoonmyung Lee
Sensors 2019, 19(17), 3685; https://doi.org/10.3390/s19173685 - 24 Aug 2019
Cited by 4 | Viewed by 4370
Abstract
An energy-harvesting interface for kinetic energy harvesting from high-voltage piezoelectric and triboelectric generators is proposed in this paper. Unlike the conventional kinetic energy-harvesting interfaces optimized for continuous sinusoidal input, the proposed harvesting interface can efficiently handle irregular and random high voltage energy inputs. [...] Read more.
An energy-harvesting interface for kinetic energy harvesting from high-voltage piezoelectric and triboelectric generators is proposed in this paper. Unlike the conventional kinetic energy-harvesting interfaces optimized for continuous sinusoidal input, the proposed harvesting interface can efficiently handle irregular and random high voltage energy inputs. An N-type mosfet (NMOS)-only power stage design is introduced to simplify power switch drivers and minimize conduction loss. Controller active mode power is also reduced by introducing a new voltage peak detector. For efficient operation with potentially long intervals between random kinetic energy inputs, standby power consumption is minimized by monitoring the input with a 43 pW wake-up controller and power-gating all other circuits during the standby intervals. The proposed harvesting interface can harvest energy from a wide range of energy inputs, 10 s of nJ to 10 s of µJ energy/pulse, with an input voltage range of 5–200 V and an output range of 2.4–4 V under discontinuous as well as continuous excitation. The proposed interface is examined in two scenarios, with integrated power stage devices (maximum input 45 V) and with discrete power stage devices (maximum input 200 V), and the harvesting efficiency is improved by up to 600% and 1350%, respectively, compared to the case when harvesting is performed with a full bridge rectifier. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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18 pages, 1012 KiB  
Article
EEMIP: Energy-Efficient Communication Using Timing Channels and Prioritization in ZigBee
by Pavol Gočal and Dominik Macko
Sensors 2019, 19(10), 2246; https://doi.org/10.3390/s19102246 - 15 May 2019
Cited by 7 | Viewed by 2964
Abstract
With the expansion of the Internet-of-Things, energy-efficient communication is becoming vital. The communication among energy-limited devices (e.g., powered by batteries or harvesting the energy from their environment) must be energy-efficient, prolonging their lifetime or increasing data throughput. This article aims at proposing energy-efficient [...] Read more.
With the expansion of the Internet-of-Things, energy-efficient communication is becoming vital. The communication among energy-limited devices (e.g., powered by batteries or harvesting the energy from their environment) must be energy-efficient, prolonging their lifetime or increasing data throughput. This article aims at proposing energy-efficient periodic communication for devices over the ZigBee protocol and powered by a battery. We propose using timing channels for different data priorities, thus, more important data are sent more frequently. The priority is also considered in case of congested traffic, where a central device (coordinator) prioritizes more important communication. We have implemented a simulator, which serves for verification of the proposed solution, and conducted experiments comparing the proposed EEMIP method with the standard nonbeacon ZigBee communication. The experimental results show that the proposed method is more energy efficient. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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28 pages, 10022 KiB  
Article
A System-Level Methodology for the Design of Reliable Low-Power Wireless Sensor Networks
by Oussama Brini, Dominic Deslandes and Frederic Nabki
Sensors 2019, 19(8), 1800; https://doi.org/10.3390/s19081800 - 15 Apr 2019
Cited by 9 | Viewed by 3938
Abstract
Innovative Internet of Things (IoT) applications with strict performance and energy consumption requirements and where the agile collection of data is paramount are arising. Wireless sensor networks (WSNs) represent a promising solution as they can be easily deployed to sense, process, and forward [...] Read more.
Innovative Internet of Things (IoT) applications with strict performance and energy consumption requirements and where the agile collection of data is paramount are arising. Wireless sensor networks (WSNs) represent a promising solution as they can be easily deployed to sense, process, and forward data. The large number of Sensor Nodes (SNs) composing a WSN are expected to be autonomous, with a node’s lifetime dictated by the battery’s size. As the form factor of the SN is critical in various use cases, minimizing energy consumption while ensuring availability becomes a priority. Moreover, energy harvesting techniques are increasingly considered as a viable solution for building an entirely green SN and prolonging its lifetime. In the process of building a SN and in the absence of a clear and well-rounded methodology, the designer can easily make unfounded and suboptimal decisions about the right hardware components, their configuration, and reliable data communication techniques, such as automatic repeat request (ARQ) and forward error correction (FEC). In this paper, a methodology to design, configure, and deploy a reliable ultra-low power WSNs is proposed. A comprehensive energy model and a realistic path-loss (PL) model of the sensor node are also established. Through estimations and field measurements it is proven that, following the proposed methodology, the designer can thoroughly explore the design space and the make most favorable decisions when choosing commercial off-the-shelf (COTS) components, configuring the node, and deploying a reliable and energy-efficient WSN. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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14 pages, 597 KiB  
Letter
Voltage-Frequency Domain Optimization for Energy-Neutral Wearable Health Devices
by Yigit Tuncel, Sizhe An, Ganapati Bhat, Naga Raja, Hyung Gyu Lee and Umit Ogras
Sensors 2020, 20(18), 5255; https://doi.org/10.3390/s20185255 - 14 Sep 2020
Cited by 2 | Viewed by 2021
Abstract
Wearable health and activity monitoring devices must minimize the battery charging and replacement requirements to be practical. Numerous design techniques, such as power gating and multiple voltage-frequency (VF) domains, can be used to optimize power consumption. However, circuit-level techniques alone cannot minimize energy [...] Read more.
Wearable health and activity monitoring devices must minimize the battery charging and replacement requirements to be practical. Numerous design techniques, such as power gating and multiple voltage-frequency (VF) domains, can be used to optimize power consumption. However, circuit-level techniques alone cannot minimize energy consumption unless they exploit domain-specific knowledge. To this end, we propose a system-level framework that minimizes the energy consumption of wearable health and activity monitoring applications by combining domain-specific knowledge with low-power design techniques. The proposed technique finds the energy-optimal VF domain partitioning and the corresponding VF assignments to each partition. We evaluate this framework with experiments on two activity monitoring and one electrocardiogram applications. Our approach decreases the energy consumption by 33–58% when compared to baseline designs. It also achieves 20–46% more savings compared to a state-of-the-art approach. Full article
(This article belongs to the Special Issue Low-Power Sensors and Systems for IoT)
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