Distributed MAC and Rate Adaptation for Ultrasonically Networked Implantable Sensors

TL;DR

This paper introduces ultrasonic communication protocols for implantable medical devices, addressing limitations of RF methods by proposing a new ultrasonic transmission technique and a distributed multiple access control, validated through multi-scale simulation.

Contribution

It develops the first ultrasonic-based network protocols for implantable devices, including a novel Ultrasonic WideBand transmission method and a distributed access control scheme.

Findings

Feasibility of ultrasonic intra-body communication demonstrated.

Proposed UsWB technique achieves efficient, low-impact data transmission.

Distributed access control enables multiple devices to communicate simultaneously.

Abstract

The use of miniaturized biomedical devices implanted in the human body and wirelessly internetworked is promising a significant leap forward in medical treatment of many pervasive diseases. Recognizing the well-understood limitations of traditional radio-frequency wireless communications in interconnecting devices within the human body, in this paper we propose for the first time to develop network protocols for implantable devices based on ultrasonic transmissions. We start off by assessing the feasibility of using ultrasonic propagation in human body tissues and by deriving an accurate channel model for ultrasonic intra-body communications. Then, we propose a new ultrasonic transmission and multiple access technique, which we refer to as Ultrasonic WideBand (UsWB). UsWB is based on the idea of transmitting information bits spread over very short pulses following a time-hopping pattern. The short impulse duration results in limited reflection and scattering effects, and its low duty cycle reduces the thermal and mechanical effects, which are detrimental for human health. We then develop a multiple access technique with distributed control to enable efficient simultaneous access by interfering devices based on minimal and localized information exchange and on measurements at the receiver only. Finally, we demonstrate the performance of UsWB through a multi-scale simulator that models the proposed communication system at the acoustic wave level, at the physical (bit) level, and at the network (packet) level.