Search

Secure communication can be considered as an integral part of the next generation implantable medical devices. With the advent of Physical Layer Security (PLS) methods, confidential messages can be transmitted without the use of encryption keys. For analyzing the effectiveness of PLS for next-generation leadless cardiac pacemakers, we provide secrecy analysis using a performance metric of secrecy capacity. Secrecy capacity defines the secure transmission rate between legitimate nodes without leakage of information to an eavesdropper and depends on respective channel attenuations. The legitimate and eavesdropper channel attenuations are evaluated by 3D numerical electromagnetic simulations using a detailed human model. We do not assume eavesdropper to be located in specific directions or positions and considers it to be located anywhere around the body. We evaluate the secrecy capacity by defining a spherical grid for eavesdropper positions around the body with a radius of 1 m. The secrecy capacity of the entire space is evaluated by extrapolating the grid to different radial distances using free space path loss model. Moreover, by fixing application based secure communication rate, the entire space is divided into secure and in-secure volumes. The in-secure volume consists of all the eavesdropper positions from which the pacemaker can be eavesdropped. We also evaluated the angle from which the maximum leakage of information takes place and referred it as “Eve's sweet spot angle.” Data for channel attenuations from phantom and in-vivo experiments is also utilized to validate and observe the differences between simulations and experiments. This article will help in design of the communication module of implanted leadless cardiac pacemakers with enhanced security on the physical layer. [ABSTRACT FROM AUTHOR]

Propagation of radio-frequency signals inside human body is demanding to analyze as it is a highly complex medium consisting of different frequency-dependent lossy materials of varying thickness. Moreover, experimental analyses are also unfeasible because that requires probes to be placed inside a human body to collect the signals. This paper focuses on in-body to in-body implant communication for future multinodal capsule-like leadless cardiac pacemaker technology. The frequency range of 0.3–3 GHz is analyzed using very detailed numerical simulations of digital human models. The results show that the Industrial, Scientific, and Medical radio band of the frequency range of 2.4–2.5 GHz is optimal, having the least attenuation of signals considering the size constraints of the implant antenna. Furthermore, the placement of an additional subcutaneous implant transceiver is studied. The analysis shows that the abdominal wall is the optimal position for the placement of the implant compared to shoulder and lateral side of the body. This result is further validated by anin vivoexperiment on an adult pig. The other novelty of the study is the investigation of the channel behavior based on ventricular blood volume of the heart to find out the appropriate timing of the transmission of signals between the implants. The results show that the attenuation of the signal increases with the increase in blood volume inside the heart. [ABSTRACT FROM AUTHOR]