Visible to the public Body Sensor Networks: Holistic Approach from Silicon to Users

Body sensor networks (BSN) are emerging cyber-physical systems that promise to improve the quality of life through improved health, augmented sensing and actuation for the disabled, independent living for the elderly, and reduced healthcare costs. However, the physical nature of BSNs introduces several new challenges. The human body, especially in the context of medical conditions, is a highly dynamic and unpredictable physical environment that creates constantly changing demands on sensing, actuation, and quality of service (QoS). At the same time, movement between indoor and outdoor environments and rapid physical movements of arms and legs constantly change the wireless channel characteristics. These dynamic application contexts can also have a dramatic impact on data and resource prioritization. Thus, BSNs must simultaneously deal with rapid changes to both top-down application requirements and bottom-up resource availability. This is made all the more challenging by the wearable nature of BSN devices, which necessitates a vanishingly small size and, therefore, extremely limited hardware resources and power budget. Current research is being performed to develop new principles and techniques for adaptive operation in highly dynamic physical environments, using new miniaturized, energy-constrained devices. This work uses a holistic cross-layer approach that simultaneously addresses all aspects of the system, from low-level hardware design to higher-level communication and data fusion algorithms, to top-level applications, in order to optimize the energy efficiency, system lifetime, and value to the user of the BSN. As an example of the holistic view, we are developing a suite of new asymmetric "three radio" MAC protocols to simultaneously achieve low power, high data rate, and low response time. We designed a new hardware platform for energy efficient nodes. This node leverages the state-of-the- art in low power RF transmitters, low voltage boost circuits, sub-threshold processing, bio-signal front-ends, dynamic power management, and energy harvesting to realize an integrated reconfigurable SoC capable of autonomous power management for battery-free operation. We also developed a 98nW wake-up radio with an active area of 0.03sqmm. The radio has a sensitivity of -41dBm and a data rate of 100kbps while requiring two off-chip passive components, both smaller than the size of the a typical 915MHz chip antenna. A QoS framework has been developed to support coordination within and across multiple BSNs.

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Body Sensor Networks: Holistic Approach from Silicon to Users