A Periodic Transmission Line Model for Body Channel Communication

Body channel communication (BCC) is a technique for data transmission exploiting the human body as communication channel. Even though it was pioneered about 25 years ago, the identification of a good electrical model behind its functioning is still an open research question. The proposed distributed model can then serve as a supporting tool for the design, allowing to enhance the performances of any BCC system. A novel finite periodic transmission line model was developed to describe the human body as transmission medium. According to this model, for the first time, the parasitic capacitance between the transmitter and the receiver is assumed to depend on their distance. The parameters related to the body and electrodes are acquired experimentally by fitting the bio-impedentiometric measurements, in the range of frequencies from 1 kHz to 1 MHz, obtaining a mean absolute error lower than 4° and 30 $Omega$ for the phase angle and impedance modulus, respectively. The proposed mathematical framework has been successfully validated by describing a ground-referred and low-complexity system called Live Wire, suitable as supporting tool for visually impaired people, and finding good agreement between the measured and the calculated data, marking a ±3% error for communication distances ranging from 20 to 150 cm. In this work we introduced a new circuital approach, for capacitive-coupling systems, based on finite periodic transmission line, capable to describe and model BCC systems allowing to optimize the performances of similar systems

A Periodic Transmission Line Model for Body Channel Communication

Body channel communication (BCC) is a technique for data transmission exploiting the human body as communication channel. Even though it was pioneered about 25 years ago, the identification of a good electrical model behind its functioning is still an open research question. The proposed distributed model can then serve as a supporting tool for the design, allowing to enhance the performances of any BCC system. A novel finite periodic transmission line model was developed to describe the human body as transmission medium. According to this model, for the first time, the parasitic capacitance between the transmitter and the receiver is assumed to depend on their distance. The parameters related to the body and electrodes are acquired experimentally by fitting the bio-impedentiometric measurements, in the range of frequencies from 1 kHz to 1 MHz, obtaining a mean absolute error lower than 4° and 30Ω for the phase angle and impedance modulus, respectively. The proposed mathematical framework has been successfully validated by describing a ground-referred and low-complexity system called Live Wire, suitable as supporting tool for visually impaired people, and finding good agreement between the measured and the calculated data, marking a ±3% error for communication distances ranging from 20 to 150 cm. In this work we introduced a new circuital approach, for capacitive-coupling systems, based on finite periodic transmission line, capable to describe and model BCC systems allowing to optimize the performances of similar systems

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

Human Body–Electrode Interfaces for Wide-Frequency Sensing and Communication: A Review

Several on-body sensing and communication applications use electrodes in contact with the human body. Body–electrode interfaces in these cases act as a transducer, converting ionic current in the body to electronic current in the sensing and communication circuits and vice versa. An ideal body–electrode interface should have the characteristics of an electrical short, i.e., the transfer of ionic currents and electronic currents across the interface should happen without any hindrance. However, practical body–electrode interfaces often have definite impedances and potentials that hinder the free flow of currents, affecting the application’s performance. Minimizing the impact of body–electrode interfaces on the application’s performance requires one to understand the physics of such interfaces, how it distorts the signals passing through it, and how the interface-induced signal degradations affect the applications. Our work deals with reviewing these elements in the context of biopotential sensing and human body communication

Estudio de la variabilidad de las medidas de comunicaciones intracorporales ante diferentes sujetos con diferentes características

El significativo avance de las Tecnologías de la Información y la Comunicación (TIC) en los últimos tiempos permite su aplicación en el sector de la salud de numerosas maneras, aportando beneficios de calidad, seguridad y un importante ahorro económico. En este ámbito toman gran relevancia los Sistemas de Salud Personales (PHS) que suponen una innovación ideada para ofrecer una asistencia sanitaria ininterrumpida, individualizada y de calidad controlada. En este marco se presentan las redes de sensores corporales (BSN) como una solución para el seguimiento de personas con problemas de salud, ya que las redes de sensores corporales surgen como respuesta a la necesidad de garantizar la individualización en la asistencia sanitaria y la prevención, así como mejorar la calidad de vida del paciente. Las redes inalámbricas de sensores proporcionan sistemas personalizados de atención médica que permiten la monitorización remota del paciente [1] en cualquier momento y lugar. Que el paciente sea supervisado las 24 horas del día influye en la necesidad de considerar que estas redes de sensores sean inalámbricas para una mayor comodidad, así como el tamaño de los sensores, u otros aspectos como el consumo de baterías, la inmunidad frente a interferencias, el alcance y la tasa de transmisión de datos. Zigbee o Bluetooth Low Energy (BLE) son estándares de comunicaciones empleados en redes inalámbricas de área personal que actualmente son implementadas pero con una serie de limitaciones [2] como: el número de dispositivos que se pueden usar, la velocidad [3] de transmisión de datos o interferencias con dispositivos que trabajen en la misma frecuencia. Debido a estas limitaciones surgieron las Intrabody Communication (IBC). Las Intrabody Communication emplean el cuerpo humano como medio de transmisión de las señales eléctricas para la interconexión de sensores inalámbricos en los sistemas de monitorización biomédicos. En este caso, la señal queda confinada en la superficie de la piel sin radiar al exterior, por lo que disminuye tanto las interferencias con dispositivos cercanos, como el consumo. Por ello, este tipo de comunicación es adecuada para aplicaciones biomédicas. No obstante, al ser las señales transmitidas a través de la superficie corpotal, se ven condicionadas por las propiedades de los tejidos vivos creando incertidumbre en las medidas. En este trabajo se ha realizado un análisis de la influencia de las características antropométricas en las comunicaciones intracorporales. Para ello, y como consecuencia de la falta de estandarización en las medidas en IBC y la incertidumbre que presenta el cuerpo humano, se ha empleado un modelo circuital (phantom) con el propósito de validar los distintos montajes experimentales empleados antes de las pruebas finales sobre voluntarios. Dicho phantom modela el comportamiento en frecuencia de los distintos tejidos que componen el brazo humano. El análisis fue realizado desde dos puntos de vista. En primer lugar se analizó la impedancia de entrada, con el propósito de estimar la corriente inyectada y mantenerla dentro de los márgenes de seguridad. En segundo lugar se analizó la atenuación de la señal en diversas frecuencias y diferentes distancias con el propósito de proporcionar información sobre las características del canal de comunicaciones corporal. A continuación, se procedió a realizar las medidas experimentales con dos sujetos de diferentes características. Las diferencias encontradas pusieron de manifiesto la importancia de las características antropométricas en las comunicaciones corporales. Como la señal se atenuaba rápidamente a medida que aumentaba la distancia, se encontraron serios problemas a la hora de medir en distancias superiores a 12 cm. El ruido en los niveles de señal obtenidos también resultaba importante, lo que impedía la realización de medidas objetivas para distancias mayores. Para resolver el problema de la señal atenuada se diseñó una etapa amplificadora en recepción. Para ello se realizó un estudio de amplificadores y de posibles configuraciones de circuitos para conseguir amplificar la señal. Aun solventando este problema de la atenuación, la señal seguía estando interferida por el ruido. Se realizó un proceso iterativo para eliminar el ruido de la señal implementando un circuito electrónico de captura de señal con tres electrodos. Este tercer terminal permitía obtener un punto de referencia para las medidas y de esta forma se conseguía eliminar el ruido. Se realizaron simulaciones en el osciloscopio para analizar los efectos que se producían en la señal recibida cuando se implementaba el tercer electrodo en las mediciones. Una vez comprobado los efectos, se volvieron a realizar medidas con diferentes personas para estudiar la influencia de las características de los distintos sujetos. Los resultados obtenidos para los dos sujetos con el setup mejorado fueron muy distintos, y estos resultados, a su vez, discrepaban de los resultados obtenidos para los dos sujetos de la primera experimentación. El setup mejorado ha permitido realizar medidas del canal de comunicaciones corporal a mayores distancias que el setup inicial. Los circuitos electrónicos de la etapa de captura de señal para la amplificación y eliminación de ruido con el tercer electrodo podrían ser empleados para optimizar las prestaciones de un transceptor en comunicaciones intracorporales.The significant advancement of information and communications technology (ICT ) in recent times allows implementation in the health sector in many ways providing quality benefits , safety and significant financial savings. In this area Personal Health Systems ( PHS ) take great relevance which represent an innovation designed to deliver an uninterrupted , individualized and quality controlled health care. In this framework the body sensor networks (BSN ) are shown as a solution for tracking people with health problems because the body sensor networks arise in response to the necesity to ensure individualization in health care and prevention as well as improve the quality of life of patients. Wireless sensor networks provide personalized health care systems that allow remote monitoring of the patient at any time and place. The patient is monitored 24 hours a day influences the need to consider these sensor networks are wireless for comfort as well as the size of the sensors, or other aspects such as battery consumption, immunity against interference the extent and rate of data transmission. Standards such as Zigbee or Bluetooth Low Energy ( BLE ) are wireless personal area networks that they are currently implemented but with a number of limitations such as the number of devices that it can be used , the speed of data transmission or interference with devices that work in the same frequency. Because of these limitations intrabody Communication ( IBC ) emerged. The Intrabody Communication employ the human body as a transmission medium of electrical signals to interconnect wireless sensor in biomedical monitoring systems. In this case, the signal is confined to the skin surface without radiating to the outside, thereby decreasing both interference with nearby devices such as consumption. Therefore, this type of communication is suitable for biomedical applications. However, when signals are transmitted through the corpotal surface, they are conditioned by the properties of living tissue by creating uncertainty in the measurements. The analysis was conducted from two points of view. Firstly, the input impedance was analyzed in order to estimate the injected current and keep within safety margins analyzed. Secondly, the signal attenuation at different frequencies and different distances was analyzed in order to provide information on the channel characteristics body communications. Then it proceeded to perform experimental measurements with two subjects with different characteristics. The differences highlighted the importance of anthropometric characteristics in body communications. As the signal is attenuated rapidly with increasing distance, serious problems when measured at distances exceeding 12 cm were found. The noise in the signal levels obtained also was important, which prevented the realization of objective measures for greater distances. To solve the problem of the attenuated signal design a amplifier stage in reception. For this, study amplifiers and possible circuit configurations was performed for amplifying the signal. Even solving this problem of attenuation, the signal was still interfered by noise. An iterative process was performed to remove noise signal implementing a phantom with three terminals. This third terminal allowed to obtain a reference point for measurements and thus eliminate noise was achieved. Simulations were performed on the oscilloscope to analyze the effects that occurred in the received signal when the third electrode was implemented in measurements. Once verified the effects, measurements with different people returned to perform to study the influence of the characteristics of the different subjects. The results obtained for the two subjects with improved setup were very different, and these results, in turn, results obtained differed for the two subjects of the first experimentation. The setup has allowed improved measures body channel communications over greater distances than the initial setup. The electronic circuitry of the capture step signal for amplification and elimination of noise with the third electrode could be used to optimize the performance of a transceiver in intracorporeal communications.Universidad de Sevilla. Grado en Ingeniería de las Tecnologías de Telecomunicació

Ultrasound data communication system for bioelectronic medicines

PhD ThesisThe coming years may see the advent of distributed implantable devices to support bioelectronic medicinal treatments. Such treatments could be complementary and, in some cases, may even prove superior to pharmaceutical treatments for certain chronic disease conditions. Therefore, a significant research effort is being undertaken in the bioelectronics domain. Target conditions include diabetes, inflammatory bowel disease, lupus, and arthritis. Modern active medical implantable devices require communications to transmit information to the outside world or other implantable sub-systems. This can include physiological data, diagnostics, and parameters to optimise the therapeutic protocol. However, the communication scheme can be very challenging especially for deeper devices. Challenges include absorption and scattering by tissue, and the need to ensure there are no undesirable heating effects. Wired connectivity is undesirable and tissue absorption of traditional radio frequency and optical methods mean that ultrasound communications have significant potential in this niche. In this thesis, a reliable and efficient ultrasonic communication telemetry is presented. An omnidirectional transducer has been employed to implement intra body communication inside a model of the human body. A prototype has been implemented to evaluate the system performance in saline and up to 30 distance between the transmitter and receiver. Short pulses sequences with guard intervals have been employed to minimise the multipath effect that leads to an increase in the bit and thus packet error rates with distance. Error detection and correction code have been employed to improve communication at a low signal to noise ratio. The data rate is limited to 0.6 due to the necessary guard intervals. Energy per bit and current consumption for the transmitter and receiver main parts are presented and discussed in terms of battery life. Transmission can be achieved at an energy cost of 642 per bit data packet using on/off power cycling in the electronics