Body Channel Communication System Research Articles

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.

Enabling Interactive Infrastructure with Body Channel Communication

Body channel communication (BCC) uses the human body to carry signals, and therefore provides communication and localization that are directly tied to human presence and actions. Previous BCC systems were expensive, could operate only in a laboratory, or only focused on special use cases. We present here an end-to-end BCC system that is designed for ambient intelligence. We introduce the BCC infrastructure that consists of portable devices (e.g., a simple sphere), mobile devices (e.g., a smartwatch-like wristband), and stationary devices (e.g., floor/wall tiles). We also describe the core technology that is used in each of these units. The TouchCom hardware-software platform is a simple transceiver with software-centered processing. The focus on software (even the implementation of the physical layer is based on software) allows the adaptivity that is necessary to operate a BCC-based system in practice. The paper describes the design and a prototype implementation of the TouchCom-based interactive infrastructure and provides evidence that this BCC infrastructure works for different persons and different setups. The system provides moderate bandwidth (about 3.5 kb/s) that is suitable for several usage scenarios like games, localization, and identification. The implemented demonstrations illustrate the benefits these applications gain when touching an object is tied to communication.

The Effects of Electrode Configuration on Body Channel Communication Based on Analysis of Vertical and Horizontal Electric Dipoles

The effects of electrode configuration on body channel communication (BCC) are studied for the development of body channel characteristics, such as frequency response, path loss, and resilience to other interferers. First, this paper introduces nine types of electrode configurations according to the arrangement and direction of both transmitting and receiving electrodes on the body. Each configuration is then modeled by means of vertical and horizontal electric dipoles. From Maxwell’s equations, the complete equations of vertical and horizontal electric fields on the human body, followed by the ratios of the received electric field to the transmitted electric field, are obtained to find the theoretical body channel characteristics and the effect of electrode configurations on the body channel. The theory is verified with measurement results using a network analyzer and balun transformer. In addition to the channel characteristics, the influence of BCC and RF interference on the body channel is investigated and discussed along with receiving electrode configurations. Based on the measurement results, we found that vertical electrodes in the transmitter and horizontal electrodes with longitudinal direction in the receiver is the optimal configuration for BCC in regard to transmission gain, environmental sensitivity, and interference resilience. Finally, we suggest an effective parameter for BCC, which is equivalent reference distance to determine the proper electrode size for the required frequency response. The relation between the parameter and the electrode size is formulated for the purpose of proper electrode utilization in the design of BCC systems as well as in many potential applications.

High Bandwidth Efficiency and Low Power Consumption Walsh Code Implementation Methods for Body Channel Communication

With the growing number of wearable devices and applications, there is an increasing need for a flexible body channel communication (BCC) system that supports both scalable data rate and low power operation. In this paper, a highly flexible frequency-selective digital transmission (FSDT) transmitter that supports both data scalability and low power operation with the aid of two novel implementation methods is presented. In an FSDT system, data rate is limited by the number of Walsh spreading codes available for use in the optimal body channel band of 40-80 MHz. The first method overcomes this limitation by applying multi-level baseband coding scheme to a carrierless FSDT system to enhance the bandwidth efficiency and to support a data rate of 60 Mb/s within a 40-MHz bandwidth. The proposed multi-level coded FSDT system achieves six times higher data rate as compared to other BCC systems. The second novel implementation method lies in the use of harmonic frequencies of a Walsh encoded FSDT system that allows the BCC system to operate in the optimal channel bandwidth between 40-80 MHz with half the clock frequency. Halving the clock frequency results in a power consumption reduction of 32%. The transmitter was fabricated in a 65-nm CMOS process. It occupies a core area of 0.24 × 0.3 mm 2 . When operating under a 60-Mb/s data-rate mode, the transmitter consumes 1.85 mW and it consumes only 1.26 mW when operating under a 5-Mb/s data-rate mode.

The Signal Transmission Mechanism on the Surface of Human Body for Body Channel Communication

The signal transmission mechanism on the surface of the human body is studied for the application to body channel communication (BCC). From Maxwell's equations, the complete equation of electrical field on the human body is developed to obtain a general BCC model. The mechanism of BCC consists of three parts according to the operating frequencies and channel distances: the quasi-static near-field coupling part, the reactive induction-field radiation part, and the surface wave far-field propagation part. The general BCC model by means of the near-field and far-field approximation is developed to be valid in the frequency range from 100 kHz to 100 MHz and distance up to 1.3 m based on the measurements of the body channel characteristics. Finally, path loss characteristics of BCC are formulated for the design of BCC systems and many potential applications.