U-Wear: Software-Defined Ultrasonic Networking for Wearable Devices

Abstract

Wearable medical sensing devices with wireless capabilities have become the cornerstone of many revolutionary digital health applications that promise to predict and treat major diseases by acquiring and processing health information. Existing wireless wearable devices are connected through radio frequency (RF) electromagnetic wave carriers based on standards such as Bluetooth or WiFi. However, these solutions tend to almost-blindly scale down traditional wireless technologies to the body environment, with little or no attention to the peculiar characteristics of the human body and the severe privacy and security requirements of patients. We contend that this is not the only possible approach, and we present U-Wear, the first networking framework for wearable medical devices based on ultrasonic communications. U-Wear encloses a set of physical, data link and network layer functionalities that can flexibly adapt to application and system requirements to efficiently distribute information between ultrasonic wearable devices. U-Wear also offers reconfiguration functionalities at the application layer to provide a flexible platform to develop medical applications. We design two prototypes that implement U-Wear and operate in the near-ultrasonic frequency range using commercial-off-the-shelf (COTS) speakers and microphones. Despite the limited bandwidth, i.e., about 2 kHz, and COTS audio hardware components not optimized for operating at high frequency, our prototypes (i) achieve data rates up to 2.76 kbit/s with bit-error-rate lower than 10-5 using a transmission power of 20 mW; (ii) enable multiple nodes to share the medium; and (iii) implement reconfigurable data processing to extract medical parameters from sensors with high accuracy.