The prevalence of chronic diseases has become public health concerns and strains on an over-burdened healthcare system, therefore to effectively control chronic disease and improve the quality of life for patients, continuous health monitoring is required. A proposed model for this is human body communication (HBC), a signal transmission method utilizing the human body as a part of the transmission path, a body area network (BAN), for data storage and communication. Now, a study from researchers at Tokyo University constructs a signal transmission system using a transmitter on the human body to an off-body receiver touched by a finger. The team states the HBC characteristics specific to impedance and electrodes have the potential to improve the design and working of devices based on HBC. The study is published in the journal IEEE Transactions on Biomedical Circuits and Systems.
Previous studies show HBC represents a more secure network as it uses a lower-frequency signal sharply attenuated depending on the distance. HBC uses electrodes to conduct an electric field from a transmitter to a receiver to communicate data. The signal emanates from the transmitter electrode and goes through the body where the body’s conductivity couples the field to the environment to serve as the return path for the transmitted signal. The current study constructs an equivalent circuit model of a signal transmission system travelling from the body to an off-body receiver through touch.
The current study constructs an HBC system where the ground electrode of the transmitter is in contact with the human body. This is a different configuration compared to capacitive HBC configurations which leave the ground electrode floating. The relationship between the received signal voltage and the distance between the transmitter’s electrodes, the size of the receiver ground, and the transmitter-receiver distance were evaluated.
Results show the transmitter-receiver distance and the distance between the transmitter’s electrodes were both independently related to the equivalent signal source voltage. Data findings show the receiver ground size which is related to the capacitive coupling between the receiver ground and the human body was related to the equivalent output impedance. The team states their data is important as it enables scientists to design more efficient HBC devices, which are better tuned to the human electric field and, hopefully, better suited for user interaction.
The team surmises they have developed an HBC model which makes it possible to communicate with confidentiality without generating electromagnetic noise. For the future, the researchers state focus will now be on applications of HBC which transmit relatively low-capacity data, such as authentication information and biomedical signals, for long periods with low power consumption.
Source: Tokyo University
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