Željka Lučev Vasić

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.

Past Results, Present Trends, and Future Challenges in Intrabody Communication

Intrabody communication (IBC) is a wireless communication technology using the human body to develop body area networks (BANs) for remote and ubiquitous monitoring. IBC uses living tissues as a transmission medium, achieving power-saving and miniaturized transceivers, making communications more robust against external interference and attacks on the privacy of transmitted data. Due to these advantages, IBC has been included as a third physical layer in the IEEE 802.15.6 standard for wireless body area networks (WBANs) designated as Human Body Communication (HBC). Further research is needed to compare both methods depending on the characteristics of IBC application. Challenges remain for an optimal deployment of IBC technology, such as the effect of long-term use in the human body, communication optimization through more realistic models, the influence of both anthropometric characteristics and the subject’s movement on the transmission performance, standardization of communications, and development of small-size and energy-efficient prototypes with increased data rate. The purpose of this work is to provide an in-depth overview of recent advances and future challenges in human body/intrabody communication for wireless communications and mobile computing.

Biological Evaluation of the Effect of Galvanic Coupling Intrabody Communication on Human Skin Fibroblast Cells

Intrabody communication (IBC) is an effective way to connect various kinds of wearable devices attached on or under the surface of the body, but it is important to quantitatively evaluate the biological effects of the IBC signal on the human body before its further application. The research described in this paper analyzed the responses of HSF (human skin fibroblast) cells exposed to IBC electrical signals. A galvanic coupling IBC signal transmitting system was designed to expose the experimental samples with different amplitudes (from 0 V to 6 V or 0 mA to 4 mA), different frequencies (from 10 kHz to 1 MHz), and different duration times (12 h and 24 h). The control groups were unexcited. Cell morphology and activity were evaluated with inverted microscope and MTT assays. The cell survival rates of all the experiment groups were in the range of 90% to 110%. Then, the data was analyzed by t-tests to assess whether there were statistically significant differences. The results showed that values were greater than 0.05, so there were no significant differences between the experimental and control groups. Therefore, it can be concluded that the IBC signals do not have a significant effect on HSF cells.

On the Transformer Effects in the Measurements of Capacitive Intrabody Communication Transmission Characteristics Using Grounded Instruments

In a balun transformer, balanced winding terminals are symmetrical with respect to the ground. However, some commercial RF transformers used in the measurements of the IBC system transmission characteristics and referred to as baluns do not have symmetrical capacitances between their input terminals and ground. When using these transformers, switching the positions of the electrodes connected to the same transformer winding can lead to drastically different measurement results. In this paper we will show that the change in the measured amplitude for different signal and ground electrode arrangements is influenced by the transformer symmetry to the ground, and not the capacitive intrabody communication transmission characteristics.

Corrigendum to “Biological Evaluation of the Effect of Galvanic Coupling Intrabody Communication on Human Skin Fibroblast Cells”

1College of Physics and Information Engineering, Fuzhou University, Fuzhou, China 2Key Lab of Medical Instrumentation & Pharmaceutical Technology of Fujian Province, Fuzhou, China 3Faculty of Electrical Engineering and Computing, University of Zagreb, Zagreb, Croatia 4State Key Laboratory of Analog and Mixed-Signal VLSI, University of Macau, Macau, China 5Department of Electrical and Computer Engineering, Faculty of Science and Technology, University of Macau, Macau, China 6Key Lab of Eco-Industrial Green Technology of Fujian Province, Nanping, China

Single-Chip Intrabody Communication Node

The goal of this paper is to present the development of a phase modulated signal generator and receiver pair that are designed with intrabody communication (IBC) purposes in mind. The system is to be implemented using Programmable System-on-Chip (PSoC) microcontrollers produced by Cypress. The design and the firmware are to be implemented in Cypress PSoC Creator for the CY8C5888LTI-LP097.

The Design and Experiment of the Leg Model Based on Galvanic Coupling Intra-Body Communication

The phantom model of the leg based on galvanic coupling IBC (intra-body communication) was established to simulate the channel characteristics of human body. The 3D reconstruction of human’s leg was carried out by using the data of real man. It’s outer contour was printed by the 3D printer, then filled it with the special solution to obtain the phantom model. To verify whether the phantom model can be conformity with reality, the in vivo experiment was done. The experimental results showed that the outcome of the phantom experiment was consistent with that of the in vivo experiment, while the channel length range from 4 cm to 30 cm and the frequency was at 10 kHz–500 kHz. The absolute value of the error of corresponding data was less than 7 dB. It turned out that the phantom model restructured by the real human image data could simulate the real galvanic coupling IBC channel better.

Investigation of Power Consumption with Different MAC Layer Protocols for Galvanic Coupling Intra-body Communication

Galvanic coupling intra-body communication is a low power consumption method, which is especially suitable for the Body Area Network (BAN) in medical or healthcare domain. Based on the physical layer modeling to get an insight in the propagation mechanism in the human body, it is necessary to analyze the MAC layer performance for the galvanic coupling IBC. A multi-node physiological signal monitoring and transmission system was assumed as the application scenario in this paper. Two common protocols, namely TDMA and CSMA/CA were selected to calculate and compare the energy consumption per bit in wireless networks consisting of intra-body communication and ZigBee nodes. The results showed that, due to the low power consumption during the transmitting and receiving period, the TDMA protocol in an IBC network had the lowest energy consumption of around 1.3 μJ/bit, which was also nearly constant with the number of nodes. The energy consumption of CSMA/CA protocol in an IBC network increased slowly along with the number of nodes, and was a little lower than the consumption of a TDMA protocol in a ZigBee network, because of the higher data rate of ZigBee. A large amount of energy was consumed in channel listening to avoid data packet collision. So the CSMA/CA protocol in a ZigBee network used the highest amount of energy per bit.