An implantable low-power ultrasonic platform for the Internet of Medical Things
It is well known that electromagnetic radio-frequency (RF) waves that are the basis of most commercial wireless technologies are largely unsuitable to interconnect deeply implanted medical devices. RF waves are in fact absorbed by aqueous biological tissues and prone to malicious jamming attacks or to environmental interference from pervasively deployed RF communication systems; moreover, they pose a potential safety hazard when exposure of tissues is prolonged and at high power. While existing wireless technologies can satisfy the requirements of some specific applications, the root challenge of enabling networked intra-body miniaturized sensors and actuators that communicate through body tissues is largely unaddressed. Considering these limitations, this article proposes a high data rate ultrasonic communication scheme for wireless intra-body networks. The proposed scheme can enable various applications that require high sampling rates such as neural data recording or monitoring of the digestive tract through endoscopic pills. The proposed scheme is based on Orthogonal Frequency-Division Multiplexing (OFDM), which is proven to be robust against frequency-selective channels with relatively long delay spreads like the intra-body ultrasonic channel. The proposed scheme is implemented in a prototype ultrasonic software-radio and demonstrated to achieve data rates up to 28.12 Mbit/s through synthetic phantoms mimicking the ultrasonic propagation characteristics of biological tissues.