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Body-Centric Sensors for the Internet of Things

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

Deadline for manuscript submissions: closed (31 December 2021) | Viewed by 22686

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Special Issue Editors

Prof. Dr. Patrick Van Torre

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Guest Editor

Universiteit Gent, Ghent, Belgium
Interests: body-centric wireless communication; wireless sensor networks; MIMO wireless systems; software-defined radio

Prof. Dr. Slawomir J. Ambroziak

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Guest Editor

Department of Radio Communication Systems and Networks, Faculty of Electronics, Telecommunications and Informatics, Gdańsk University of Technology, Gdańsk, Poland
Interests: body-centric wireless communication; body area networks; radio channel measurements and modelling; radio wave propagation; IoT for healthcare

Dr. Akram Alomainy

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Guest Editor

School of Electronic Engineering and Computer Science, Faculty of Science and Engineering, Queen Mary University of London, Mile End Road, London E1 4NS, UK
Interests: basics of antennae and electromagnetism, from megastructures and metasurfaces to novel applications in telerobotics, cognitive radio, wearable electronics, nanoscale networks, healthcare, and bioengineering
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

In today’s world, wireless connectivity is of ever increasing importance. The Internet of Things (IoT) allows wireless internet connection to small low-power sensors, supported by a number of wireless standards, employed in different frequency bands, each of which has its unique radio propagation properties. In body-centric applications, multiple sensors can be used on the same person, cooperating in a wirelessly connected system. Multiple wearable nodes on the same person can help to mitigate shadowing of the radio waves by the human body. Sensor fusion techniques can be employed to obtain richer or more reliable measurements, or cooperative communication can be used in order to increase the reliability or throughput of communication. The new Bluetooth 5.1 standard now allows angle of arrival (AoA) as well as angle of departure (AoD) capabilities and is one example of emerging technologies that will shape the future of wireless sensing. In fact, the measured wireless signal’s strength together with its angle of arrival provide an additional sensory system on their own. In these systems, the sensor and its wireless connectivity should be seen as a whole. Body-centric wireless sensors form an important research domain, with virtually unlimited possibilities for the development of ever more performing systems.

Prof. Dr. Patrick Van Torre
Prof. Dr. Sławomir J. Ambroziak
Dr. Akram Alomainy

Guest Editors

Manuscript Submission Information

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Keywords

body-centric
wearables
Internet of Things (IoT)
wireless sensor networks (WSN)
radio propagation
angle of arrival (AoA)
5G

Published Papers (7 papers)

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Research

13 pages, 3683 KiB

Open AccessArticle

Wearable Sensors Based on Force-Sensitive Resistors for Touch-Based Collaborative Digital Gaming

by Balaji Dontha, Kyoung Swearingen, Scott Swearingen, Susan E. Thrane and Asimina Kiourti

Sensors 2022, 22(1), 342; https://doi.org/10.3390/s22010342 - 04 Jan 2022

Cited by 2 | Viewed by 2612

Abstract

We report new classes of wearable sensors that monitor touch between fully-abled and disabled players in order to empower collaborative digital gaming between the two. Our approach relies on embroidered force-sensitive resistors (FSRs) embedded into armbands, which outperform the state-of-the-art in terms of sensitivity to low applied forces (0 to 5 N). Such low forces are of key significance to this application, given the diverse physical abilities of the players. With a focus on effective gameplay, we further explore the sensor’s touch-detection performance, study the effect of the armband fabric selection, and optimize the sensor’s placement upon the arm. Our results: (a) demonstrate a 4.4-times improvement in sensitivity to low forces compared to the most sensitive embroidered FSR reported to date, (b) confirm the sensor’s ability to empower touch-based collaborative digital gaming for individuals with diverse physical abilities, and (c) provide parametric studies for the future development of diverse sensing solutions and game applications. Full article

(This article belongs to the Special Issue Body-Centric Sensors for the Internet of Things)

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15 pages, 50750 KiB

Open AccessArticle

A Wearable Button Antenna Sensor for Dual-Mode Wireless Information and Power Transfer

by Jiahao Zhang, Jin Meng, Wei Li, Sen Yan and Guy A. E. Vandenbosch

Sensors 2021, 21(17), 5678; https://doi.org/10.3390/s21175678 - 24 Aug 2021

Cited by 12 | Viewed by 2695

Abstract

A novel wearable button antenna sensor is proposed for the concept of simultaneous wireless information and power transfer (SWIPT). This integrates two working modes for the transfer of power and information, respectively, and optimizes transfer efficiency. An omni-directional radiation pattern is achieved in the 3.5 GHz World Interoperability for Microwave Access (WiMAX) band to support on-body wireless communications, while a circularly polarized broadside radiation pattern is obtained in the 5 GHz wireless local area networks (WLAN) band to harvest power. The measured −10 dB return loss bandwidths are 4.0% (3.47–3.61 GHz) in the lower band, and 25.0% (4.51–5.80 GHz) in the higher band, respectively. An artificial magnetic conductor (AMC) structure with wideband characteristics is applied to obtain a low-profile design and to increase the stability of the antenna sensor. A high radiation efficiency of over 80% in the whole working band is observed. The specific absorption rate (SAR) of the proposed antenna sensor is below 0.509 W/kg at 3.55 GHz, and below 0.0532 W/kg at 5.5 GHz, respectively, which is much lower than the European standard threshold of 2 W/kg. All these characteristics make the designed antenna sensor suitable for on-body information transmission and off-body energy harvesting. The antenna sensor has been prototyped. Simulations and measurements agree well, proving the validity of the new concept. Full article

(This article belongs to the Special Issue Body-Centric Sensors for the Internet of Things)

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15 pages, 1412 KiB

Open AccessArticle

Characterizing the Impact of Doppler Effects on Body-Centric LoRa Links with SDR

by Thomas Ameloot, Marc Moeneclaey, Patrick Van Torre and Hendrik Rogier

Sensors 2021, 21(12), 4049; https://doi.org/10.3390/s21124049 - 12 Jun 2021

Cited by 6 | Viewed by 1856

Abstract

Long-range, low-power wireless technologies such as LoRa have been shown to exhibit excellent performance when applied in body-centric wireless applications. However, the robustness of LoRa technology to Doppler spread has recently been called into question by a number of researchers. This paper evaluates the impact of static and dynamic Doppler shifts on a simulated LoRa symbol detector and two types of simulated LoRa receivers. The results are interpreted specifically for body-centric applications and confirm that, in most application environments, pure Doppler effects are unlikely to severely disrupt wireless communication, confirming previous research, which stated that the link deteriorations observed in a number of practical LoRa measurement campaigns would mainly be caused by multipath fading effects. Yet, dynamic Doppler shifts, which occur as a result of the relative acceleration between communicating nodes, are also shown to contribute to link degradation. This is especially so for higher LoRa spreading factors and larger packet sizes. Full article

(This article belongs to the Special Issue Body-Centric Sensors for the Internet of Things)

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17 pages, 4888 KiB

Open AccessArticle

Embroidered Textile Antennas: Influence of Moisture in Communication and Sensor Applications

by Davor Bonefačić and Juraj Bartolić

Sensors 2021, 21(12), 3988; https://doi.org/10.3390/s21123988 - 09 Jun 2021

Cited by 11 | Viewed by 2469

Abstract

Moisture causes detuning and increased losses in textile antennas, and it affects resonant and wideband textile antennas differently. In this work, we studied the effect of moisture on a resonant textile planar inverted-F antenna (PIFA) and a wideband textile monopole antenna. Both antennas were manufactured by embroidering conductive yarn in denim textile. The input reflection coefficient, antenna gain, and gain patterns were measured on both antennas for different moisture contents. The results show that wideband antennas are less affected by moisture in comparison with resonant antennas. For communications applications, large moisture content in the textile antenna should be avoided; therefore a flexible, textile-based waterproofing antenna cover was proposed, manufactured, and tested. On the other hand, the effect of antenna detuning by moisture can be used for moisture-sensing application. This concept was demonstrated on the resonant textile PIFA in transmission and reflection setups, showing that the reflection setup gives better results. Full article

(This article belongs to the Special Issue Body-Centric Sensors for the Internet of Things)

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14 pages, 4381 KiB

Open AccessArticle

RF Sensing Based Breathing Patterns Detection Leveraging USRP Devices

by Mubashir Rehman, Raza Ali Shah, Muhammad Bilal Khan, Najah Abed AbuAli, Syed Aziz Shah, Xiaodong Yang, Akram Alomainy, Muhmmad Ali Imran and Qammer H. Abbasi

Sensors 2021, 21(11), 3855; https://doi.org/10.3390/s21113855 - 02 Jun 2021

Cited by 18 | Viewed by 6379

Abstract

Non-contact detection of the breathing patterns in a remote and unobtrusive manner has significant value to healthcare applications and disease diagnosis, such as in COVID-19 infection prediction. During the epidemic prevention and control period of COVID-19, non-contact approaches have great significance because they minimize the physical burden on the patient and have the least requirement of active cooperation of the infected individual. During the pandemic, these non-contact approaches also reduce environmental constraints and remove the need for extra preparations. According to the latest medical research, the breathing pattern of a person infected with COVID-19 is unlike the breathing associated with flu and the common cold. One noteworthy symptom that occurs in COVID-19 is an abnormal breathing rate; individuals infected with COVID-19 have more rapid breathing. This requires continuous real-time detection of breathing patterns, which can be helpful in the prediction, diagnosis, and screening for people infected with COVID-19. In this research work, software-defined radio (SDR)-based radio frequency (RF) sensing techniques and machine learning (ML) algorithms are exploited to develop a platform for the detection and classification of different abnormal breathing patterns. ML algorithms are used for classification purposes, and their performance is evaluated on the basis of accuracy, prediction speed, and training time. The results show that this platform can detect and classify breathing patterns with a maximum accuracy of 99.4% through a complex tree algorithm. This research has a significant clinical impact because this platform can also be deployed for practical use in pandemic and non-pandemic situations. Full article

(This article belongs to the Special Issue Body-Centric Sensors for the Internet of Things)

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14 pages, 572 KiB

Open AccessArticle

Securing the Insecure: A First-Line-of-Defense for Body-Centric Nanoscale Communication Systems Operating in THz Band

by Waqas Aman, Muhammad Mahboob Ur Rahman, Hasan T. Abbas, Muhammad Arslan Khalid, Muhammad A. Imran, Akram Alomainy and Qammer H. Abbasi

Sensors 2021, 21(10), 3534; https://doi.org/10.3390/s21103534 - 19 May 2021

Cited by 2 | Viewed by 2715

Abstract

This manuscript presents a novel mechanism (at the physical layer) for authentication and transmitter identification in a body-centric nanoscale communication system operating in the terahertz (THz) band. The unique characteristics of the propagation medium in the THz band renders the existing techniques (say for impersonation detection in cellular networks) not applicable. In this work, we considered a body-centric network with multiple on-body nano-senor nodes (of which some nano-sensors have been compromised) who communicate their sensed data to a nearby gateway node. We proposed to protect the transmissions on the link between the legitimate nano-sensor nodes and the gateway by exploiting the path loss of the THz propagation medium as the fingerprint/feature of the sender node to carry out authentication at the gateway. Specifically, we proposed a two-step hypothesis testing mechanism at the gateway to counter the impersonation (false data injection) attacks by malicious nano-sensors. To this end, we computed the path loss of the THz link under consideration using the high-resolution transmission molecular absorption (HITRAN) database. Furthermore, to refine the outcome of the two-step hypothesis testing device, we modeled the impersonation attack detection problem as a hidden Markov model (HMM), which was then solved by the classical Viterbi algorithm. As a bye-product of the authentication problem, we performed transmitter identification (when the two-step hypothesis testing device decides no impersonation) using (i) the maximum likelihood (ML) method and (ii) the Gaussian mixture model (GMM), whose parameters are learned via the expectation–maximization algorithm. Our simulation results showed that the two error probabilities (missed detection and false alarm) were decreasing functions of the signal-to-noise ratio (SNR). Specifically, at an SNR of 10 dB with a pre-specified false alarm rate of

0.2

, the probability of correct detection was almost one. We further noticed that the HMM method outperformed the two-step hypothesis testing method at low SNRs (e.g., a

10 %

increase in accuracy was recorded at SNR = −5 dB), as expected. Finally, it was observed that the GMM method was useful when the ground truths (the true path loss values for all the legitimate THz links) were noisy. Full article

(This article belongs to the Special Issue Body-Centric Sensors for the Internet of Things)

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20 pages, 5045 KiB

Open AccessArticle

Fully Flexible Textile Antenna-Backed Sensor Node for Body-Worn UWB Localization

by Dries Van Baelen, Nicola Macoir, Quinten Van den Brande, Eli De Poorter, Sam Lemey, Jo Verhaevert and Hendrik Rogier

Sensors 2021, 21(5), 1641; https://doi.org/10.3390/s21051641 - 26 Feb 2021

Cited by 5 | Viewed by 2357

Abstract

A mechanically flexible textile antenna-backed sensor node is designed and manufactured, providing accurate personal localization functionality by application of Decawave’s DW1000 Impulse Radio Ultra-Wideband (IR-UWB) Integrated Circuit (IC). All components are mounted on a flexible polyimide foil, which is integrated on the backplane of a wearable cavity-backed slot antenna designed for IR-UWB localization in Channels 2 and 3 of the IEEE 802.15.4-2011 standard (3744 MHz–4742.4 MHz). The textile antenna’s radiation pattern is optimized to mitigate body effects and to minimize absorption by body tissues. Furthermore, its time-domain characteristics are measured to be adequate for localization. By combining the antenna and the bendable Printed Circuit Board (PCB), a mechanically supple sensor system is realized, for which the performance is validated by examining it as a node used in a complete localization system. This shows that six nodes around the body must be deployed to provide system coverage in all directions around the wearer. Even without using sleep mode functionalities, the measurements indicate that the system’s autonomy is 13.3 h on a 5 V 200 mAh battery. Hence, this system acts as a proof of concept for the joining of localization electronics and other sensors with a full-textile antenna into a mechanically flexible sensor system. Full article

(This article belongs to the Special Issue Body-Centric Sensors for the Internet of Things)

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