Human Body Channel Research Articles

Bio-Physical Modeling, Characterization, and Optimization of Electro-Quasistatic Human Body Communication.

Human body communication (HBC) has emerged as an alternative to radio wave communication for connecting low power, miniaturized wearable, and implantable devices in, on, and around the human body. HBC uses the human body as the communication channel between on-body devices. Previous studies characterizing the human body channel has reported widely varying channel response much of which has been attributed to the variation in measurement setup. This calls for the development of a unifying bio-physical model of HBC, supported by in-depth analysis and an understanding of the effect of excitation, termination modality on HBC measurements. This paper characterizes the human body channel up to 1MHz frequency to evaluate it as a medium for the broadband communication. The communication occurs primarily in the electro-quasistatic (EQS) regime at these frequencies through the subcutaneous tissues. A lumped bio-physical model of HBC is developed, supported by experimental validations that provide insight into some of the key discrepancies found in previous studies. Voltage loss measurements are carried out both with an oscilloscope and a miniaturized wearable prototype to capture the effects of non-common ground. Results show that the channel loss is strongly dependent on the termination impedance at the receiver end, with up to 4dB variation in average loss for different termination in an oscilloscope and an additional 9 dB channel loss with wearable prototype compared to an oscilloscope measurement. The measured channel response with capacitive termination reduces low-frequency loss and allows flat-band transfer function down to 13KHz, establishing the human body as a broadband communication channel. Analysis of the measured results and the simulation model shows that instruments with 50 Ω input impedance (Vector Network Analyzer, Spectrum Analyzer) provides pessimistic estimation of channel loss at low frequencies. Instead, high impedance and capacitive termination should be used at the receiver end for accurate voltage mode loss measurements of the HBC channel at low frequencies. The experimentally validated bio-physical model shows that capacitive voltage mode termination can improve the low frequency loss by up to 50dB, which helps broadband communication significantly.

Characterization and Classification of Human Body Channel as a function of Excitation and Termination Modalities.

Human Body Communication (HBC) has recently emerged as an alternative to radio frequency transmission for connecting devices on and in the human body with order(s) of magnitude lower energy. The communication between these devices can give rise to different scenarios, which can be classified as wearable-wearable, wearable-machine, machine-machine interactions. In this paper, for the first time, the human body channel characteristics is measured for a wide range of such possible scenarios (14 vs. a few in previous literature) and classified according to the form-factor of the transmitter and receiver. The effect of excitation/termination configurations on the channel loss is also explored, which helps explain the previously unexplained wide variation in HBC Channel measurements. Measurement results show that wearable-wearable interaction has the maximum loss (upto -50 dB) followed by wearable-machine and machinemachine interaction (min loss of 0.5 dB), primarily due to the small ground size of the wearable devices. Among the excitation configurations, differential excitation is suitable for small channel length whereas single ended is better for longer channel.

Measurement and Analysis of Electric Signal Transmission Using Human Body as Medium for WBAN Applications

Human body communications (HBCs) realize wireless body area networks (WBANs) using the human body as a transmission channel without wired or wireless connections. While presenting various approaches for measurement and analysis of the human body channel, previous studies require additional interpretations of their results to obtain practical design parameters for a desired communication system. This paper addresses the provision of specific design guidelines based on the proposed channel measurement for capacitive coupling HBC employing digital transmission, adopted in the IEEE standards 802.15.6. for WBAN. In the experiments, customized channel-sounding signals were applied to the human body using a battery-powered device with a ground-electrode size of $27 \times 50$ mm2. The signals received after passage through the body were measured considering 30 kinds of measurement conditions determined by the body postures and locations of the transmitter and receiver. The operating frequencies of the transmission signals were varied up to 100 MHz. This work derives the minimum required lengths of symbol-codes based on analyses of channel-measured data in terms of measurement conditions, operating frequencies, and bandwidths of a receive-filter, to achieve a maximum data rate. This was done to ensure handling of intrinsic signal errors such as those by inter-symbol-interference, and to provide more reliable bit-error-rate performance in the human body channel, depending on the transmitter structures.

Multilayer Distributed Circuit Modeling for Galvanic Coupling Intrabody Communication

Characterization of the human body as a transmission medium for electrical signals is a necessity for using intrabody communication (IBC) technique into connecting wearable electronic sensors and devices. In this paper, we propose a novel multilayer distributed circuit model for galvanic-coupling type IBC, which is emphasized on the propagation characteristics in contrast with other IBC models. Based on the model, a program is written in MATLAB to investigate the propagation characteristics of a human body channel with the frequency of 10 MHz to 20 MHz and the distance of 5 cm to 10 cm. Finally, a galvanic coupling IBC measurement is implemented to verify the proposed model. The outcome proves that the model is valid and correct.

Non-Parametric Approach of Video Capsule Endoscope Localization Using Suboptimal Method of Position Bounded CWCL

For proper diagnosis, location of the wireless video capsule endoscope is required to be known by the physicians. In this paper, we propose an algorithm of localizing the capsule using path loss-based calibrated weighted centroid localization (CWCL). The main challenge in path loss-based localization is the highly randomness of measured path loss due to shadow fading and multi-path propagation effects of human body channel. To address the randomness in the measured path loss, we propose two methods of path loss estimation using Gaussian weighted average filter and the multiple input multiple output diversity scheme. Then, we calculate the weight of the sensor receiver position using the estimated path loss. Finally, the position of the capsule is estimated using position-bounded CWCL. We propose a realistic suboptimal method of estimating the calibration coefficient and also compute the optimal value of coefficient to set the benchmark. Additionally, we propose two boundary conditions on the estimated positions to improve the localization accuracy. We simulate our proposed algorithms using MATLAB to validate the accuracy and observe significant improvements without any prior knowledge of channel parameters. The proposed algorithms improve the accuracy up to 5.14-mm root mean square error and outperform the existing literature.

A 274µW clock synchronized wireless body area network IC with super-regenerative RSSI for biomedical ad-hoc network system.

A clock synchronized multi-node wireless body area network (WBAN) transceiver IC with super-regenerative RSSI is proposed for biomedical ad-hoc network system. The ad-hoc network makes stable communication even in the harsh human body channel condition (<;-50 dB attenuation) with low-power consumption. The proposed system consists of two types of IC - a hub and node IC. The hub IC broadcasts the 240 MHz clock signal to the whole node ICs and gather the measured data through body channel communication (BCC). In the node IC, it has 2 key building blocks; 1) Injection locking clock synchronization receiver, and 2) Super-regenerative RSSI (SR-RSSI) and OOK receiver. As a result, the 240 MHz clock is exactly synchronized in the node IC with 90 μW power consumption. And a channel-condition-adapted ad-hoc network is constructed based on the SR-RSSI data. SR-RSSI consumes 184 μW concurrent achieving OOK receiver functionality for the ad-hoc network. The proposed WBAN IC is fabricated in 0.18 μm CMOS technology.

Characterization of Impulse Radio Intrabody Communication System for Wireless Body Area Networks

Intrabody communication (IBC) is a promising data communication technique for body area networks. This short-distance communication approach uses human body tissue as the medium of signal propagation. IBC is defined as one of the physical layers for the new IEEE 802.15.6 or wireless body area network (WBAN) standard, which can provide a suitable data rate for real-time physiological data communication while consuming lower power compared to that of radio-frequency protocols such as Bluetooth. In this paper, impulse radio (IR) IBC (IR-IBC) is examined using a field-programmable gate array (FPGA) implementation of an IBC system. A carrier-free pulse position modulation (PPM) scheme is implemented using an IBC transmitter in an FPGA board. PPM is a modulation technique that uses time-based pulse characteristics to encode data based on IR concepts. The transmission performance of the scheme was evaluated through signal propagation measurements of the human arm using 4- and 8-PPM transmitters, respectively. 4 or 8 is the number of symbols during modulations. It was found that the received signal-to-noise ratio (SNR) decreases approximately 8.0 dB for a range of arm distances (5–50 cm) between the transmitter and receiver electrodes with constant noise power and various signal amplitudes. The SNR for the 4-PPM scheme is approximately 2 dB higher than that for the 8-PPM one. In addition, the bit error rate (BER) is theoretically analyzed for the human body channel with additive white Gaussian noise. The 4- and 8-PPM IBC systems have average BER values of 10−5 and 10−10, respectively. The results indicate the superiority of the 8-PPM scheme compared to the 4-PPM one when implementing the IBC system. The performance evaluation of the proposed IBC system will improve further IBC transceiver design.

A novel low-power compact WBS human body channel receiver for wearable vital signal sensing application in wireless body-area network

This paper presents a low-power compact wideband signaling (WBS) human body channel (HBC) receiver for wearable vital sensing application in wireless body-area network. By investigating the characterization of HBC in frequency-domain and time-domain, a simply empirical HBC channel model over 1–100 MHz is proposed, and represented as a bandpass filter with its output signals of weak narrow pulses in 30 ns-width. According to the measurement and modeling for HBC, the proposed WBS based HBC receiver exploits an architecture with a low-power compact two-stage analog front end (AFE) followed by an all-digital data recovery circuit. To further reduce the power consumption and chip area, the AFE incorporates a capacitor-coupling pre-amplifier and a fully adjustable process, voltage, temperature independent 1-bit digitizer based on Schmitt trigger. Furthermore, the all-digital data recovery circuit adopts the feedforward 3-phase oversampling algorithm for low-jitter output with approximate 50% duty-cycle. With implementation in SMIC 130 nm CMOS technology, the proposed WBS based HBC receiver achieves 5 Mb/s operation with the power dissipation of 0.82 mW at a 1.2 V supply voltage while occupying a chip area of 0.26 mm2.

Local Parametric Approach of Wireless Capsule Endoscope Localization Using Randomly Scattered Path Loss Based WCL

We propose scattered path loss based weighted centroid localization (WCL) algorithm for wireless video capsule endoscope (VCE). The main challenge in this approach is the random deviation in the measured received signal strength indicator (RSSI) caused by multipath propagation and shadowing effects of human body channel which in turn increases the localization error. To address this issue, we propose local parameter dependent path loss representation in the training phase and apply adaptive least square error (LSE) method to extract the parameters. Then, in the test phase, we estimate distance using the extracted parameters and the randomly scattered path loss. The position of capsule is estimated using non-degree based WCL followed by a calibration process. We propose suboptimal method of estimating the calibration coefficient and also compute the optimal value of coefficient analytically to set the benchmark. We develop a simulation platform using MATLAB to present the results and to verify the performance. We gradually increase the number of sensors and place them in different topologies using different dimensions. The obtained accuracy by our proposed suboptimal method of WCL is very close to the optimal benchmark for all cases. Our proposed approach also outperforms existing works in terms of localization accuracy.

Review of capacitive coupling human body communications based on digital transmission

Abstract Human body communications (HBC) have been studied as an enabling technology to meet the recently increased demands for low-power and high-simplicity in wireless body area networks for wearable-device applications. Previous works on HBC focused mainly on channel modeling with a measurement method, signal transmission scheme, and transceiver implementation. In particular, the digital transmission, invented as a customized approach for the human body channel, has contributed to develope low-complexity HBC systems. This paper addresses on-going research on capacitive coupling HBC based on digital transmission by exploring recent literature.

Communication channel modeling of human forearm with muscle fiber tissue characteristics.

Human-Body Communication (HBC) is a wireless communication method using the human body tissue as a transmission medium for signals. This paper on the basis of human muscle fiber tissues' characteristics, it is first proposed to establish the analytical model of galvanic coupling human-body communication channel. In this model, the parallel and the transverse electrical characteristics of muscular tissue are fully considered, and the model accurately presents the transmission mechanism of galvanic coupling human-body communication signals in the channel. At last, through compare with the experimental results and calculation results, the maximum error of the model is 22.4% and the average error is 14.2% within the frequency range.

A Secure System For Pervasive Social Network-Based Healthcare

Modern technologies of mobile computing and wireless sensing prompt the concept of pervasive social network (PSN)-based healthcare. To realize the concept, the core problem is how a PSN node can securely share health data with other nodes in the network. In this paper, we propose a secure system for PSN-based healthcare. Two protocols are designed for the system. The first one is an improved version of the IEEE 802.15.6 display authenticated association. It establishes secure links with unbalanced computational requirements for mobile devices and resource-limited sensor nodes. The second protocol uses blockchain technique to share health data among PSN nodes. We realize a protocol suite to study protocol runtime and other factors. In addition, human body channels are proposed for PSN nodes in some use cases. The proposed system illustrates a potential method of using blockchain for PSN-based applications.

Human body and head characteristics as a communication medium for Body Area Network.

An in-depth investigation of the Body Channel Communication (BCC) under the environment set according to the IEEE 802.15.6 Body Area Network (BAN) standard is conducted to observe and characterize the human body as a communication medium. A thorough measurement of the human head as part of the human channel is also carried out. Human forehead, head to limb, and ear to ear channel is characterized. The channel gain of the human head follows the same bandpass profile of the human torso and limbs with the maximum channel gain occurring at 35MHz. The human body channel gain distribution histogram at given frequencies, while all the other parameters are held constant, exhibits a maximum variation of 2.2dB in the channel gain at the center frequency of the bandpass channel gain profile.

Performance of amplify forward and decode forward cooperative strategies for body surface communications in UWB Body Area Networks

SummaryBody area networks (BAN) are being developed for telemonitoring of patients. Ultra wideband (UWB) is the most preferred choice for the physical layer of the BAN as it provides high data rate at low power consumption along with a simple transceiver structure. But because of high fading characteristics of the human body channel, the range of UWB will be limited, and a reliable communication cannot be guaranteed. In that case, cooperative communications may be applied to BAN for improving system performance and link quality.The paper proposes a novel approach by applying amplify and forward, and decode and forward cooperative relaying strategies with maximal ratio combining for BAN. The performance of single relay AF and DF relaying have been compared with direct transmission. Further, the efficacy of the proposed strategies has been validated by transmitting electrocardiogram signals and magnetic resonance imaging images. Simulations and validations have been carried out on Institute of Electrical and Electronics Engineers designated CM3 channel model for BAN designed from real time measurements data. A signal‐to‐noise ratio gain of at least 3 dB is clearly observed from simulation results. Thus, transmit power requirement can be minimized, which in turn improves the battery life of body sensor nodes. Copyright © 2015 John Wiley &amp; Sons, Ltd.

Performance evaluation on correlation detection and energy detection for ultra wideband‐impulse radio communication with multi‐pulse position modulation scheme in implant body area networks

Ultra wideband-impulse radio (UWB-IR) transmission, which can provide high data rate for real-time transmission and low-power consumption in transceivers, is one of promising transmission technologies in implant body area networks (BANs). Some studies on UWB-IR propagation characteristics in implant BANs have reported that UWB-IR signals suffer from large attenuation in human body channels. It is therefore necessary to clarify the actual performance of UWB-IR modulation and demodulation methods in implant BANs. In this study, the authors focus on experimental evaluation of the correlation detection and energy detection for UWB-IR transmission with multi-pulse position modulation (MPPM). For this purpose, the authors develop a UWB-IR communication system with MPPM scheme, and experimentally evaluate the transmission performance of the developed systems with the two detection methods. In addition to the experimental evaluation, the authors also theoretically analyse the bit-error rate (BER) performance of the correlation detection and energy detection methods by using Gaussian approximation. From the experimental results, the developed system has achieved a BER of 10 -2 at the propagation loss of 75 dB with a data rate of 2 Mbps in the correlation detection. This result shows the feasibility of reliable UWB-IR communication in actual implant BANs.

THE USE OF A HUMAN BODY MODEL TO DETERMINE THE VARIATION OF PATH LOSSES IN THE HUMAN BODY CHANNEL IN WIRELESS CAPSULE ENDOSCOPY

Presently, wireless capsule endoscopy (WCE) is the sole technology for inspecting the human gastrointestinal (GI) tract for diseases painlessly and in a non-invasive way. For the further development of WCE, the main concern is the development of a high- speed telemetry system that is capable of transmitting high-resolution images at a higher frame rate, which is also a concern in the use of conventional endoscopy. A vital task for such a high-speed telemetry system is to be able to determine the path loss and how it varies in a radio channel in order to calculate the proper link budget. The hostile nature of the human body's channel and the complex anatomical structure of the GI tract cause remarkable variations in path loss at difierent frequencies of the system as well as at capsule locations that have high impacts on the calculation of the link budget. This paper presents the path loss and its variation in terms of system frequency and location of the capsule. Along with the guideline about the optimum system frequency for WCE, we present the difierence between the maximum and minimum path loss at difierent anatomical regions, which is the most important information in the link-margin setup for highly e-cient telemetry systems in next-generation capsules. In order

A Design of a High-Speed and High-Efficiency Capsule Endoscopy System

This paper presents a high-speed and high-efficiency capsule endoscopy system. Both a transmitter and a receiver were optimized for its application through an analysis of the human body channel. ON-OFF keying modulation is utilized to achieve low power consumption of the in-body transmitter. A low drop output regulator is adopted to prevent performance degradation in the event of a voltage drop in the battery. The receiver adopts superheterodyne structure to obtain high sensitivity, considering the link budget from the previous analysis. The receiver and transmitter were fabricated using the CMOS 0.13-μm process. The output power of the transmitter is -1.6 dB·m and its efficiency is 27.7%. The minimum sensitivity of the receiver is -80 dB·m at a bit error ratio (BER) of 3 × 10 (-6). An outer wall loop antenna is adopted for the capsule system to ensure a small size. The integrated system is evaluated using a liquid human phantom and a living pig, resulting in clean captured images.

Channel Decomposition Method for Designing Body-Worn Antenna Diversity Systems

A channel decomposition method is presented to evaluate the diversity performance of on-body UHF antenna systems. The novelty of this method amounts to separating the human body and propagation channel for independent estimation of each contribution. The proposed method can be readily adapted to different channel environments (once the statistics are known) to considerably reduce computation time. This channel decomposition method is adopted herein to evaluate the performance of a diversified UHF body-worn antenna system under a selection diversity scheme. The design process included three human postures (standing, kneeling, and prone) to incorporate a wide range of general human activity for realistic antenna performance. Mounting locations are evaluated and multiple antennas are used to increase communication data throughput. To validate the method, a 4-channel diversity module was fabricated employing selection diversity.

Channels and Collaterals’ Biology Characteristic Research: The Channels and Collaterals Low Resistance's Electricity Physiology Characteristic with has the Mechanism Research

AimThe discussion human body channels and collaterals low resistance's electricity physiology characteristic with has the mechanism. MethodExamines the law using the acupuncture point electricity (direct current) and the HP35665A analyzer (alternating current), the input low-tension current, observes the channels and collaterals to lead the kilowatt hour, discusses the channels and collaterals to lead the kilowatt hour with other spots the difference and has the mechanism. ResultThe channels and collaterals lead the kilowatt hour to surpass other spots obviously. ConclusionThe channels and collaterals have the material base, the low resistivity channels and collaterals are the channels and collaterals important electricity physiology characteristic, channels and collaterals on-line cause one of channels and collaterals low resistance substantial clauses with other spot ion distribution difference.

Studies of Scattering, Reflectivity, and Transmitivity in WBAN Channel: Feasibility of Using UWB

The Wireless Personal Area Network (WPAN) is one of the fledging paradigms that the next generation of wireless systems is sprouting towards. Among them, a more specific category is the Wireless Body Area Network (WBAN) used for health monitoring. On the other hand, Ultra-Wideband (UWB) comes with a number of desirable features at the physical layer for wireless communications. One big challenge in adoption of UWB in WBAN is the fact that signals get attenuated exponentially. Due to the intrinsic structural complexity in human body, electromagnetic waves show a profound variation during propagation through it. The reflection and transmission coefficients of human body are highly dependent upon the dielectric constants as well as upon the frequency. The difference in structural materials such as fat, muscles and blood essentially makes electromagnetic wave attenuation to be different along the way. Thus, a complete characterization of body channel is a challenging task. The connection between attenuation and frequency of the signal makes the investigation of UWB in WBAN an interesting proposition. In this paper, we study analytically the impact of body channels on electromagnetic signal propagation with reference to UWB. In the process, scattering, reflectivity and transmitivity have been addressed with analysis of approximate layer-wise modeling, and with numerical depictions. Pulses with Gaussian profile have been employed in our analysis. It shows that, under reasonable practical approximations, the human body channel can be modeled in layers so as to have the effects of total reflections or total transmissions in certain frequency bands. This could help decide such design issues as antenna characteristics of implant devices for WBAN employing UWB.