Ultra-low power data storage for sensor networks
ACM Transactions on Sensor Networks (TOSN)
Human++: wireless autonomous sensor technology for body area networks
Proceedings of the 16th Asia and South Pacific Design Automation Conference
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Wearable and implantable wireless biomedical devices are often constrained by the limited bandwidth and high power consumption of their communication links. The VHF or UHF transceivers (e.g. MICS radios) traditionally used for this communication function have relatively high power consumption, on the order of mW, due to the high bias currents required for the analog sections of the radio. To reduce overall power consumption, both the data rate and the duty cycle of the radio are usually minimized, because the lifetime of the device is limited by the energy density of available battery technologies. Recent innovations in modulated backscatter techniques offer the possibility of a radical reduction in the power cost and complexity of the data uplink, while significantly improving data rate. This is achieved by a re-partitioning of the communication link. Backscatter techniques shift the burden of power cost and complexity from the remote device to a base station. Instead of actively transmitting an RF signal, the remote device uplinks data to the base station by modulating its reflected field. We present two ultra-low power biotelemetry systems that leverage modulated backscatter in both the near-field and far-field propagation regimes. The first example operates in the far field and is designed to telemeter multiple channels of neural/EMG signals from dragonflies in flight. This device has a mass of 38 mg, a data rate of 5 Mbit/s, and a range of approximately 5 m. The second example operates in the near field and is designed to be implanted in mice. The sensor has a maximum implant depth of 6cm and can transmit at data rates of up to 30 Mbit/s. The power cost of the animal side of both data links is 4.9 pJ/bit and 16.4 pJ/bit respectively.