Battery-free Connected Cameras

Abstract

Wireless cameras have traditionally been considered extremely power-hungry devices. The battery life of wearable camera systems (such as Google Glass, or Snap Spectacles) is under an hour when capturing video. Similarly, due to power requirements, wireless cameras (such as surveillance and monitoring cameras) are either battery-powered and require very frequent recharge, or must be plugged in, which increases cost and decreases reliability (since the camera can be disabled by attacking its power supply). In addition, power wires limit wireless camera deployment to places that have access to power lines. Existing approaches to wireless camera design optimize the camera and communication modules individually to minimize their power consumption. However, designing a wireless camera device requires power consuming hardware components and computationally intensive compression blocks (CODECs) that interface the camera and the communication modules. This thesis describes several projects that address these limitations of conventional wireless camera design. WISPCam enables battery-free image capture by harvesting energy from Radio Frequency signals. WISPCam relies on heavy duty-cycling, so there may be a long latency between consecutive images due to the camera's power requirements. Glimpse camera, a low power programmable wearable camera architecture for continuous mobile vision, integrates low-power sensing modalities and novel detection algorithms to detect when something interesting is happening in the wearer’s field of view. This allows a traditionally power hungry wireless camera system to remain in sleep mode when nothing of interest is occurring in front of the wearer. The Glimpse camera approach reduces overall power consumption of the wireless camera by more than one order of magnitude. Despite the significant reduction in wireless camera power consumption, power-wise, Glimpse is far from enabling battery-free wireless video streaming. Finally, our most recent work shows how to redesign the traditional camera architecture in order to eliminate the power-hungry CODEC, ADC, AGC and communication module in their conventional form. This work shows that 30 fps 720p (HD) video streaming can be achieved while burning only 250uW, five orders of magnitude less than available solutions. This work demonstrates that these high-resolution and high frame-rate wireless cameras can be powered by RF signals emitted from an FCC-compliant reader at a distance of up to 12 feet.