David Naranjo-Hernández

A Comprehensive Study Into Intrabody Communication Measurements

One of the main objectives of research into intrabody communication (IBC) is the characterization of the human body as a transmission medium for electrical signals. However, such characterization is strongly influenced by the conditions under which the experiments are performed. In addition, the outcomes reported in the literature vary according to the measurement method used, frequently making comparisons among them unfeasible. Further studies are still required in order to establish a methodology for IBC characterization and design. In this paper, both galvanic and capacitive coupling setups have been implemented and a comprehensive set of measurements has been carried out by analyzing fundamental IBC parameters such as optimum frequency range, maximum channel length, and type of electrodes, among others. Consequently, practical conclusions regarding the experimental conditions that optimize IBC performance for each coupling technique have been obtained.

Design and Implementation of a Distributed Fall Detection System—Personal Server

In this paper, the main results related to a fall detection system are shown by means of a personal server for the control and processing of the data acquired from multiple intelligent biomedical sensors. This server is designed in the context of a telehealthcare system for the elderly, to whom falls represent a high-risk cause of serious injuries, and its architecture can be extended to patients suffering from chronic diseases. The main design issues and developments in terms of the server hardware and software are presented with the aim of providing a real-time analysis of the processed biosignals. As a result, the evaluation study of the implemented algorithm for fall detection through a set of laboratory experiments is presented, together with some important issues in terms of the devices consumption. The proposed algorithm exhibits excellent outcomes in fall detection.

Distributed Circuit Modeling of Galvanic and Capacitive Coupling for Intrabody Communication

Modeling of intrabody communication (IBC) entails the understanding of the interaction between electromagnetic fields and living tissues. At the same time, an accurate model can provide practical hints toward the deployment of an efficient and secure communication channel for body sensor networks. In the literature, two main IBC coupling techniques have been proposed: galvanic and capacitive coupling. Nevertheless, models that are able to emulate both coupling approaches have not been reported so far. In this paper, a simple model based on a distributed parameter structure with the flexibility to adapt to both galvanic and capacitive coupling has been proposed. In addition, experimental results for both coupling methods were acquired by means of two harmonized measurement setups. The model simulations have been subsequently compared with the experimental data, not only to show their validity but also to revise the practical frequency operation range for both techniques. Finally, the model, along with the experimental results, has also allowed us to provide some practical rules to optimally tackle IBC design.

SoM: A Smart Sensor for Human Activity Monitoring and Assisted Healthy Ageing

This paper presents the hardware and software design and implementation of a low-cost, wearable, and unobstructive intelligent accelerometer sensor for the monitoring of human physical activities. In order to promote healthy lifestyles to elders for an active, independent, and healthy ageing, as well as for the early detection of psychomotor abnormalities, the activity monitoring is performed in a holistic manner in the same device through different approaches: 1) a classification of the level of activity that allows to establish patterns of behavior; 2) a daily activity living classifier that is able to distinguish activities such as climbing or descending stairs using a simple method to decouple the gravitational acceleration components of the motion components; and 3) an estimation of metabolic expenditure independent of the activity performed and the anthropometric characteristics of the user. Experimental results have demonstrated the feasibility of the prototype and the proposed algorithms.

Study of Attenuation and Dispersion Through the Skin in Intrabody Communications Systems

Intrabody communication (IBC) is a technique that uses the human body as a transmission medium for electrical signals to connect wireless body sensors, e.g., in biomedical monitoring systems. In this paper, we propose a simple, but accurate propagation model through the skin based on a distributed-parameter circuit in order to obtain general expressions that could assist in the design of IBC systems. In addition, the model is based on the major electrophysiological properties of the skin. We have found the attenuation and dispersion parameters and they have been successfully compared with several published results, thus showing the tuning capability of the model to different experimental conditions. Finally, we have evaluated different digital modulation schemes in order to assess the tradeoffs between symbol rate, bit error rate, and distance between electrodes of the skin communication channel.

Galvanic Coupling Transmission in Intrabody Communication: A Finite Element Approach

Galvanic coupling in intrabody communication (IBC) is a technique that couples low-power and low-frequency voltages and currents into the human body, which acts as a transmission medium, and thus constitutes a promising approach in the design of personal health devices. Despite important advances being made during recent years, the investigation of relevant galvanic IBC parameters, including the influence of human tissues and different electrode configurations, still requires further research efforts. The objective of this work is to disclose knowledge into IBC galvanic coupling transmission mechanisms by using a realistic 3-D finite element model of the human arm. Unlike other computational models for IBC, we have modeled the differential configuration of the galvanic coupling as a four-port network in order to analyze the electric field distribution and current density through different tissues. This has allowed us to provide an insight into signal transmission paths through the human body, showing them to be considerably dependent on variables such as frequency and inter-electrode distance. In addition, other important variables, for example bioimpedance and pathloss, have also been analyzed. Finally, experimental measurements were also carried out for the sake of validation, demonstrating the reliability of the model to emulate in general forms some of the behaviors observed in practice.

Measurement Issues in Galvanic Intrabody Communication: Influence of Experimental Setup

Significance: The need for increasingly energy-efficient and miniaturized bio-devices for ubiquitous health monitoring has paved the way for considerable advances in the investigation of techniques such as intrabody communication (IBC), which uses human tissues as a transmission medium. However, IBC still poses technical challenges regarding the measurement of the actual gain through the human body. The heterogeneity of experimental setups and conditions used together with the inherent uncertainty caused by the human body make the measurement process even more difficult. Goal: The objective of this study, focused on galvanic coupling IBC, is to study the influence of different measurement equipments and conditions on the IBC channel. Methods : Different experimental setups have been proposed in order to analyze key issues such as grounding, load resistance, type of measurement device and effect of cables. In order to avoid the uncertainty caused by the human body, an IBC electric circuit phantom mimicking both human bioimpedance and gain has been designed. Given the low-frequency operation of galvanic coupling, a frequency range between 10 kHz and 1 MHz has been selected. Results : The correspondence between simulated and experimental results obtained with the electric phantom have allowed us to discriminate the effects caused by the measurement equipment. Conclusion: This study has helped us obtain useful considerations about optimal setups for galvanic-type IBC as well as to identify some of the main causes of discrepancy in the literature.

A proposal of a fall detection algorithm for a Multidevice Personal Intelligent Platform

In this paper methodological and design issues about the development of a personal platform for the control and processing of data acquired from intelligent biomedical sensors are presented. This platform is designed in the context of a telehealthcare system for the elderly with chronic diseases, and one of its objectives is to monitor and detect fall events. The main feature of the device is its on-line personalization to the patient through adaptive knowledge generation in real-time, which will result in special time execution requirements. As a result a fall detection algorithm proposal is described and analyzed.

Distributed processing methodology for biomedical sensor networks: An optimal approach

In this paper, the major advantages of a distributed processing methodology developed in the context of biomedical sensor networks (BSN) are compared to the most usual wireless communication topology architectures developed in the literature. These advantages are highlighted in the context of a distributed fall detection system developed by the authors in terms of more facilities for system personalization to the end user and multimodal functionality in order to extend the biomedical application domain of the system. As the main result, a lower power consumption of the devices pertaining to the system is shown.

Low-Power platform and communications for the development of wireless body sensor networks

Although the roles of body sensor networks (BSNs) are similar to those carried out by the generic wireless sensor networks (WSNs), new solutions must be established to optimize communications for true pervasive biomedical monitoring transparent to the user. In this paper, a proposal of a hardware and software platform for biomedical sensors is performed, which is specially designed to minimize energy consumption in BSNs through a modular processing scheme based on the detection of events and information abstraction. The data flow is implemented through a novel communications protocol that enhances the performances of consumption and time delay of the platform. A novel aspect of the protocol is the explicit incorporation of an additional level of communications to support the distributed processing architecture that allows the execution of multiple applications in parallel within the smart sensors. The results obtained with an implementation of a smart sensor for fall detection demonstrate its feasibility as well as the viability of the communication protocol for the development of energy-efficient BSNs.