Intra-body Communication Research Articles

A Galvanic Coupling Method for Assessing Hydration Rates

Recent advances in biomedical sensors, data acquisition techniques, microelectronics and wireless communication systems opened up the use of wearable technology for ehealth monitoring. We introduce a galvanic coupled intrabody communication for monitoring human body hydration. Studies in hydration provide the information necessary for understanding the desired fluid levels for optimal performance of the body’s physiological and metabolic processes during exercise and activities of daily living. Current measurement techniques are mostly suitable for laboratory purposes due to their complexity and technical requirements. Less technical methods such as urine color observation and skin turgor testing are subjective and cannot be integrated into a wearable device. Bioelectrical impedance methods are popular but mostly used for estimating total body water with limited accuracy and sensitive to 800 mL–1000 mL change in body fluid levels. We introduce a non-intrusive and simple method of tracking hydration rates that can detect up to 1.30 dB reduction in attenuation when as little as 100 mL of water is consumed. Our results show that galvanic coupled intrabody signal propagation can provide qualitative hydration and dehydration rates in line with changes in an individual’s urine specific gravity and body mass. The real-time changes in galvanic coupled intrabody signal attenuation can be integrated into wearable electronic devices to evaluate body fluid levels on a particular area of interest and can aid diagnosis and treatment of fluid disorders such as lymphoedema.

Galvanically Coupled Intrabody Communications for Medical Implants: A Unified Analytic Model

Health-care monitoring and diagnostics technology continues to be of great interest in research due to an increasing trend in the number of people with chronic diseases. To improve accuracy and timeliness of diagnosis, electronic devices could be implanted inside human body to provide various real-time diagnostic information. However, effective technique for communicating the implant with outside world is still an open problem. Early efforts based on radio wave propagation are standardized as the medical implant communication services (MICSs) for 402–405-MHz frequency range, which was later adopted as medical device radiocommunication services for 401–406-MHz frequency range. Intrabody communication (IBC) is a relatively new technique that uses the human body as a channel with communication frequencies not exceeding several megahertz. In this paper, we propose a new analytical electromagnetic model that uses galvanically coupled IBC as an alternative to radio wave-based implant communication. The model is unified in the sense that it is based on multilayered ellipsoidal geometry that can be applied to any part of the body (i.e., head, torso, limbs, and so on). Our model effectively describes the influences of tissue layer thicknesses and electromagnetic properties, implant size and depth, and geometry of the body part. The model proves the security and low power consumption of IBC. The path loss characterization of IBC implants shows lower values compared with their MICS counterparts.

Analysis of Intra-body Communication Measurement in Biomedical Applications

The main objective of the paper is to characterize the concept of intra-body communication that allows electric signal to flow through human body. Various experiments are performed in order to verify how it is influenced under different conditions. The methodology used for this purpose is galvanic coupling method. The model is been implemented on ARM processor to measure heart rate and temperature of the human body. Measurements are carried out analyzing various IBC parameters such as size of electrodes, distance between transmitter and receiver, different environment and grounding. Practical conclusions are obtained thus analyzing the IBC performance. The system gives better performance as the data is transmitted in the form of packets. This provides secure and enhanced communication as compared to the existing systems.

Effects of human limb gestures on galvanic coupling intra-body communication for advanced healthcare system.

BackgroundIntra-Body Communication (IBC), which utilizes the human body as the transmission medium to transmit signal, is a potential communication technique for the physiological data transfer among the sensors of remote healthcare monitoring system, in which the doctors are permitted to remotely access the healthcare data without interrupt to the patients’ daily activities.MethodsThis work investigates the effects of human limb gestures including various joint angles, hand gripping force and loading on galvanic coupling IBC channel. The experiment results show that channel gain is significantly influenced by the joint angle (i.e. gain variation 1.09–11.70 dB, p < 0.014). The extension, as well as the appearance of joint in IBC channel increases the channel attenuation. While the other gestures and muscle fatigue have negligible effect (gain variation <0.77 dB, p > 0.793) on IBC channel. Moreover, the change of joint angle on human limb IBC channel causes significant variation in bit error rate (BER) performance.ConclusionsThe results reveal the dynamic behavior of galvanic coupling IBC channel, and provide suggestions for practical IBC system design.

Mathematical Model of Human Forearm Based Muscle Fiber Tissues’ Anisotropic Characteristics

On the basis of human muscle fiber tissues' characteristics, it is first proposed to establish the analytical model of galvanic coupling intra-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 intra-body communication signals in the channel.

Channel modeling and power consumption analysis for galvanic coupling intra-body communication

Intra-body communication (IBC), using the human body as the channel to transmit data, has lower power consumption, less radiation, and easier linking than common wireless communication technologies such as Bluetooth, ZigBee, and ANT+. As a result, IBC is greatly suitable for body area network (BAN) applications, such as the medical and health care field. Furthermore, IBC can be implemented in wearable devices, including smart watches, sports bracelets, somatic game devices, and multimedia devices. However, due to the limited battery capacity of sensor nodes in a BAN, especially implanted sensor nodes, it is not convenient to charge or change the batteries. Thus, the energy effectiveness of the media access control (MAC) layer strongly affects the life span of the nodes and of the entire system. Certainly, analyzing MAC layer performance in a galvanic coupling IBC is of great importance for the overall system. To obtain the attenuation properties of IBC, in vivo experiments with seven volunteers were performed. Meanwhile, an equalizer was used to compensate the frequency distortion in consideration of frequency-selective fading characteristics of intra-body channels. In addition, a comparison of the bit error rates (BER) of different modulation methods was carried out to obtain the best modulation method. Then, the attenuation characteristics of intra-body channels were applied in a multi-node physiological signal monitor and transmission system. Finally, TDMA and CSMA/CA protocols were introduced to calculate the bit energy consumption of IBC in the practical scenario. With stable characteristics of the intra-body channels, QPSK with an equalizer had a better performance than the tests without an equalizer. As a result, the modulation method of FSK could achieve a lower BER in lower signal-to-noise ratio situations and an FSK method with TDMA for the IBC had the lowest energy consumption under different practical scenarios.

Radiated noise analysis via human body for intra-body communication

The transmission path of intra-body communication is composed of capacitance coupling among nodes. Therefore, a channel model of the communication is expressed by capacitive ambient elements. Such a communication is greatly affected by external noise because the balance of the transmission path deteriorates due to environmental factors. There is a serious problem in that radiated noise via the human body emitted from an electric light or peripheral electronic equipment is likely to be transmitted along the same path as a signal by capacitance coupling. We investigated a channel model and estimated radiated noise via the human body based on experiments and circuit simulation. The validity of the channel model was clarified from noise measurement. When an additional electrode was connected to a ground electrode in a measurement system for a practical scene, the noise reduction rating was 5.11dB. However, actually, reducing the noise is difficult. Therefore, reducing the noise source in such a communication is necessary.

A Novel Field-Circuit FEM Modeling and Channel Gain Estimation for Galvanic Coupling Real IBC Measurements.

Existing research on human channel modeling of galvanic coupling intra-body communication (IBC) is primarily focused on the human body itself. Although galvanic coupling IBC is less disturbed by external influences during signal transmission, there are inevitable factors in real measurement scenarios such as the parasitic impedance of electrodes, impedance matching of the transceiver, etc. which might lead to deviations between the human model and the in vivo measurements. This paper proposes a field-circuit finite element method (FEM) model of galvanic coupling IBC in a real measurement environment to estimate the human channel gain. First an anisotropic concentric cylinder model of the electric field intra-body communication for human limbs was developed based on the galvanic method. Then the electric field model was combined with several impedance elements, which were equivalent in terms of parasitic impedance of the electrodes, input and output impedance of the transceiver, establishing a field-circuit FEM model. The results indicated that a circuit module equivalent to external factors can be added to the field-circuit model, which makes this model more complete, and the estimations based on the proposed field-circuit are in better agreement with the corresponding measurement results.

Wireless image-data transmission from an implanted image sensor through a living mouse brain by intra body communication

Intra body communication technology allows the fabrication of compact implantable biomedical sensors compared with RF wireless technology. In this paper, we report the fabrication of an implantable image sensor of 625 µm width and 830 µm length and the demonstration of wireless image-data transmission through a brain tissue of a living mouse. The sensor was designed to transmit output signals of pixel values by pulse width modulation (PWM). The PWM signals from the sensor transmitted through a brain tissue were detected by a receiver electrode. Wireless data transmission of a two-dimensional image was successfully demonstrated in a living mouse brain. The technique reported here is expected to provide useful methods of data transmission using micro sized implantable biomedical sensors.

Peer-to-Peer Communication in Neuronal Nano-Network

Serving as peers in the central nervous system, neurons make use of two communication paradigms, electrochemical, and molecular. Owing to their effective coordination of all the voluntary and involuntary actions of the body, an intriguing neuronal communication nominates as a potential paradigm for nano-networking. In this paper, we propose an alternative representation of the neuron-to-neuron communication process, which should offer a complementary insight into the electrochemical signals propagation. To this end, we apply communication-engineering tools and abstractions, represent information about chemical and ionic behavior with signals, and observe biological systems as input–output systems characterized by a frequency response. In particular, we inspect the neuron-to-neuron communication through the concepts of electrochemical communication, which we refer to as the intra-neuronal communication due to the pulse transmission within the cell, and molecular synaptic transmission, which we refer to as the inter-neuronal communication due to particle transmission between the cells. The inter-neuronal communication is explored by means of the transmitter, the channel, and the receiver, aiming to characterize the spiking propagation between neurons. Reported numerical results illustrate the contribution of each stage along the neuronal communication pathway, and should be useful for the design of a new communication technique for nano-networks and intrabody communications.

Electrical characteristic of the titanium mesh electrode for transcutaneous intrabody communication to monitor implantable artificial organs.

We have developed a tissue-inducing electrode using titanium mesh to obtain mechanically and electrically stable contact with the tissue for a new transcutaneous communication system using the human body as a conductive medium. In this study, we investigated the electrical properties of the titanium mesh electrode by measuring electrode-tissue interface resistance in vivo. The titanium mesh electrode (Hi-Lex Co., Zellez, Hyogo, Japan) consisted of titanium fibers (diameter of 50μm), and it has an average pore size of 200μm and 87% porosity. The titanium mesh electrode has a diameter of 5mm and thickness of 1.5mm. Three titanium mesh electrodes were implanted separately into the dorsal region of the rat. We measured the electrode-electrode impedance using an LCR meter for 12weeks, and we calculated the tissue resistivity and electrode-tissue interface resistance. The electrode-tissue interface resistance of the titanium mesh electrode decreased slightly until the third POD and then continuously increased to 75Ω. The electrode-tissue interface resistance of the titanium mesh electrode is stable and it has lower electrode-tissue interface resistance than that of a titanium disk electrode. The extracted titanium mesh electrode after 12 weeks implantation was fixed in 10% buffered formalin solution and stained with hematoxylin-eosin. Light microscopic observation showed that the titanium mesh electrode was filled with connective tissue, inflammatory cells and fibroblasts with some capillaries in the pores of the titanium mesh. The results indicate that the titanium mesh electrode is a promising electrode for the new transcutaneous communication system.

Equivalent-Circuit Expression of Environmental Noise Electric Fields in Intrabody Communication Channels

In the development of intrabody communication systems, the most challenging goal is to protect against noise due to other electronic devices. In this paper, the equivalent-circuit expression of environmental noise electric fields (the so-called radiated noise) in intrabody communication channels are derived based on the theory of electrostatic fields. In addition, numerical examples are shown by means of electrostatic analysis based on the method of moments, and the results agree with those by full-wave analysis based on the finite-difference time-domain method and those by measurements. Therefore, it is concluded that the proposed circuit model can properly express the contribution of environmental noise electric fields.

Effect of transformer symmetry on intrabody communication channel measurements using grounded instruments

Transformers with one winding terminal symmetrical with respect to ground (capacitances between their terminals and ground are the same) are referred to as balun transformers, and are often used for decoupling in the measurements of the intrabody communication (IBC) system transmission characteristics. We measured IBC system amplitude and phase transmission characteristics using three types of galvanic decouplers: non-symmetric RF transformers, balun transformers with center tap grounded and balun transformers with center tap floating. Four possible electrode configurations (AA, AB, BA, and BB) and four electrode arrangements (GSGS, GSSG, SGGS, and SGSG), result in a total of 16 measurement scenarios for each of three measurement setups. We showed that the change in the measured amplitude for different signal and ground electrode arrangements while measuring with non-symmetric transformers is influenced by the transformer symmetry to the ground, and not the capacitive intrabody communication transmission characteristics. The change of the amplitude in case symmetric balun transformers are used is negligible for practical purposes.

Signal Path Loss Simulation of Human Arm for Galvanic Coupling Intra-body Communication

Galvanic coupling intra-body communication involves the formation of a network between small terminals applied to the surface of the human body and bio-signal sensors embedded within the body. To enable the design of a communication device, it is important to fully understand the signal transmission loss characteristics of the human body, while developing a method that optimizes the transmission efficiency. This study analyzed the signal path loss during galvanic-coupling intra-body communication of a human arm through the application of a four-terminal circuit and a finite-element method (FEM) model, with special attention given to the return path. The effect of the interface circuit of an LC series–parallel circuit that injected the signal into the human body was also examined. Without the LC series–parallel circuit, the attenuation of the transmitted signal was minimized within a range of 2–5 MHz in the circuit model and 3–7 MHz in the FEM model. The addition of the LC series–parallel circuit improved the attenuation by 1.9–5.8 dB at the resonant frequency (2 MHz).

自動車への人体通信の適用

自動車への人体通信の適用

Signal Path Loss through the Human Arm by Galvanic Coupling Intrabody Communication Using Noncontact Electrodes on the Transmission Side

Signal Path Loss through the Human Arm by Galvanic Coupling Intrabody Communication Using Noncontact Electrodes on the Transmission Side

Dynamic Measurements of Intrabody Communication Channels and Their Dependences on Grounding Conditions

Dynamic Measurements of Intrabody Communication Channels and Their Dependences on Grounding Conditions

Intra-Body Optical Channel Modeling for In Vivo Wireless Nanosensor Networks.

In vivo wireless nanosensor networks (iWNSNs) consist of nanosized communicating devices, which can operate inside the human body in real time. iWNSNs are at the basis of transformative healthcare techniques, ranging from intra-body health-monitoring systems to drug-delivery applications. Plasmonic nanoantennas are expected to enable the communication among nanosensors in the near infrared and optical transmission window. This result motivates the analysis of the phenomena affecting the propagation of such electromagnetic (EM) signals inside the human body. In this paper, a channel model for intra-body optical communication among nanosensors is developed. The total path loss is computed by taking into account the absorption from different types of molecules and the scattering by different types of cells. In particular, first, the impact of a single cell on the propagation of an optical wave is analytically obtained, by modeling a cell as a multi-layer sphere with complex permittivity. Then, the impact of having a large number of cells with different properties arranged in layered tissues is analyzed. The analytical channel model is validated by means of electromagnetic simulations and extensive numerical results are provided to understand the behavior of the intra-body optical wireless channel. The result shows that, at optical frequencies, the scattering loss introduced by cells is much larger than the absorption loss from the medium. This result motivates the utilization of the lower frequencies of the near-infrared window for communication in iWNSNs.

A 5.4-mW 180-cm Transmission Distance 2.5-Mb/s Advanced Techniques-Based Novel Intrabody Communication Receiver Analog Front End

This paper presents a low power, long-transmission distance, high data rate intrabody communication (IBC) analog receiver front end (RFE). First, to optimize the transmission performance, conventional transmission line analysis scheme is creatively adopted to the IBC design to characterize the body channel. Second, switched-capacitor filters based on sampling rate boosting technique are adopted for higher accuracy and lower power consumption. Third, a novel RFE topology is proposed to further enhance the IBC performance. The new RFE is designed and fabricated in a standard 180-nm CMOS process. Measurement results show that the RFE can successfully transmit data spanning the whole human body, around 180 cm, which is one of the longest transmission distances reported in related literatures. Furthermore, it reaches a maximum data rate of 2.5 Mb/s with a bit error rate less than 1e-7 and consumes 5.4 mW from a 1.8 V supply. The proposed RFE compares favorably to similar reported works.

Intra-body communications: radio-frequency versus ultrasonic

Ultrasonics have been used in a number of biomedical and civil application ranging from medical ultrasound devices to beam deformation non-destructive testing. Ultrasonic pressure waves have been used naturally for thousands of years by animals for navigation and communication, with the prime examples being bats with ultrasonic navigation through air and dolphins with ultrasonic communication and navigation in water. This paper investigates on signal propagation within the human being by means of intra-body communications without radio-frequency waves but, instead, with lower (if not deeply lower) frequency waves. An exhaustive review of up-to-date propagation modes in water-like vectors is performed and experimental measurements allow the setting up of a comparison with conventional propagation. A practical demonstrator has been developed to characterize within a low frequency range the ultrasonic wave one-direction propagation in piece of meat.