Power, Communication and Sensing Solutions for Energy Constrained Platforms
MetadataShow full item record
We live in a world where mobile devices such as smartphones, smart watches and tablets are commonplace. With rapid strides in technology, we have come a long way from the first main frame computer ENIAC, which occupied 167 m2 and consumed 150 kW of electricity. But, we cannot stand still. We are still ways off from the vision of ubiquitous computing where, devices permeate our surroundings and function perpetually, without the need for maintenance or any user interference. Our current devices are either tethered to power cords or use batteries which require constant supervision and maintenance. In this work we introduce power, communication and sensing technologies to help us achieve the vision of ubiquitous computing. We note that batteries are too restricting for a large number of applications. First, we present RF energy harvesting solutions to replace batteries with power harvested from ambient RF signals. We show that we can use ambient TV and RFID signals to power computing and sensing devices. Next we show that we can transform a Wi-Fi router, a ubiquitous part of the wireless infrastructure into a source of far field wireless power, but without significantly compromising the performance of the Wi-Fi communication. For communication, we observe that traditional radio based communication is extremely power hungry which limits the lifespan of the device and makes energy harvesting impractical. We show that, using backscatter communication techniques, we can leverage ambient RF signals such as TV and RFID for power and communication between battery-free devices. This enables ubiquitous communication where devices can communicate among themselves at unprecedented scales and in locations that were previously inaccessible. Next, to bring the benefits of backscatter communication to mainstream applications, we demonstrate that using backscatter, we can synthesize Wi-Fi packets at 3-4 orders of magnitude lower power than Wi-Fi radios. These Wi-Fi transmissions at 1-11 Mbps data rate can be received on standard Wi-Fi radios, bringing low power connectivity to the Wi-Fi space. Finally, we demonstrate that backscatter techniques can also be applied to sensing to reduce power consumption. We use analog backscatter to directly transmit sensor information to a reader at zero power and combine this technique with digital backscatter to develop a digital addressable battery-free microphone. We believe the technologies developed in this work will bring up a step closer to a world where we are surrounded by perpetually operating devices.
- Electrical engineering