Signal Leakage in Fat Tissue-Based In-Body Communication: Preserving Implant Data Privacy

Medical implants are becoming increasingly widespread, and with that comes a need for networking multiple implants in the human body. This puts new demands on in-body communication, where conventional techniques (such as galvanic coupling) suffer from low bandwidth and data rates that can be insufficient for a network with several medical implants. Radio-based techniques at microwave frequencies can, on the other hand, provide a high-capacity communication channel, with the caveat that wave propagation through bodily materials at such frequencies is associated with significant signal loss, which limits the range. Fat tissue has been shown to have low loss compared to other tissues at frequencies such as 2.45 GHz and 5.8 GHz and could be a good choice of medium for a high-capacity channel. However, a drawback of radio-based in-body communication remains: signals may "leak" out of the channel to the outside environment. This work investigates the leakage aspects of fat tissue-based in-body communication and explores methods for preserving the privacy of data from implants communicating through fat tissue. Through both simulations and practical experiments, we show that signals are heavily attenuated (on average by about 27 dB) when leaving the fat channel through the skin. Signal attenuation through the skin layer is similar even when the channel is not straight. Additionally, we demonstrate that reducing the transmit power as well as using an external, friendly "jamming" signal can prevent that an external eavesdropper receives the data packets. In summary, we show that there is indeed RF leakage from in-body communication through fat tissue. However, the skin layer attenuates the signal quite heavily so that reducing the transmit power in combination with external jamming may prevent eavesdroppers outside the body from receiving sensitive in-body data.