MTL Annual Research Report 2011

Figure 1: Self-powered microsensor platform components.

Microsensor networks have applications ranging from environmental and industrial monitoring to wearable and implantable medical devices.  Despite the breadth of the application space, some design requirements are almost universal: small size, long lifetime, and, consequently, extremely high energy efficiency.  Ideally, the sensors would scavenge all the energy they need from their environment, so that their lifetime is not dependent on the capacity of their batteries.  We are developing a complete platform (Figure 1) for such a sensor system, including sensor interfaces, digital signal processors, radios and protocol processors, and energy harvesting and storage.

A system-level view is required to achieve long battery life and ultimately energy self-sufficiency. Since communication circuits typically dominate the power consumption of sensor nodes, energy-efficient local processing of information (e.g., compression or feature extraction, implemented using a custom ultra low-power DSP and algorithm-specific hardware accelerator cores) can drastically reduce the amount of transmitted data and therefore reduce the overall power consumption.  A dedicated protocol processor utilizing network coding techniques will further reduce the number of transmitted bits.  However, even with this data reduction, conventional radio circuits would still dominate the power budgets.  We are developing narrow-band transceivers that employ high-Q resonators as filters and local oscillators which will greatly reduce radio power, given the short link distances typical of microsensor networks. Finally, energy harvesting, by its very intermittent nature, is unreliable. We are developing an energy-combining power processor that combines multiple energy sources to improve reliability while also achieving improved efficiencies with an integrated maximum power-point tracking scheme.

This project is a collaboration with Stanford University and the Georgia Institute of Technology.