"Low-power Embedded Computing at the Limits of Digital Abstraction"

Mastooreh (Negin) Salajegheh, Post-doctoral Researcher, UVA

March 1st (Friday), 10:00am
Harold Frank Hall (HFH), Rm 4164 - ECE Conference Room

It’s extremely difficult to store information or keep time without power. As embedded systems continue to shrink in size and energy consumption, batteries become the greatest hurdle to further optimization. In this talk, I will describe my recent research results on low-power computers. This work consists of three systems: stochastic storage on Half-Wits (USENIX FAST’11), time estimation based on memory decay (USENIX Security’12), and secure backscatter communication (USENIX Security’09).

The Half-Wits work analyzes the stochastic behavior of writing to embedded flash memory at voltages lower than recommended by a microcontroller’s specifications to reduce energy consumption. Flash memory integrated within a microcontroller typically requires the entire chip to operate on common supply voltage almost double what the CPU portion requires. Our approach tolerates a lower supply voltage so that the CPU may operate in a more energy efficient manner. Our software-only coding algorithms enable reliable storage at low voltages on unmodified hardware by exploiting the electrically cumulative nature of half-written data in write-once bits. Measurements show that our software approach reduces energy consumption by up to 50%. This work is joint with Erik Learned-Miller (UMass Amherst) and Andrew Jiang (Texas A&M).

The TARDIS technique helps locally maintain a sense of time elapsed without power and without special-purpose hardware. The TARDIS software computes the expiration state of a timer by analyzing the decay of existing on-chip SRAM. The TARDIS enables coarse-grained, hourglass-like timers such that cryptographic software can more deliberately decide how to throttle its response rate. Our experiments demonstrate that the TARDIS can measure time ranging from seconds to several hours depending on hardware parameters. Key challenges to implementing a practical TARDIS include compensating for temperature and handling variation across hardware. This work is joint with Wayne Burleson (UMass Amherst) and Jacob Sorber (Clemson University).

The CCCP work exploits radio as a resource to amplify the storage capabilities of batteryless, programmable RFID tags. The smaller energy requirements of radio allow the RFID tags either to devote more energy to computation or to accomplish the same tasks using less energy, which may translate into a longer operating range. The main challenge in this work is to design an energy-saving remote storage system that provides security under the constraints of passive RFID systems. Our experiments show that—despite cryptographic overhead—remote storage consumes less energy than storing data to flash for data sizes above roughly 64 bytes.

About Mastooreh (Negin) Salajegheh:

photo of mastooreh salajegheh Mastooreh (Negin) Salajegheh is a postdoctoral research associate at the University of Virginia working with Dr. Kevin Skadron. She received her Ph.D. degree in 2012 from the University of Massachusetts Amherst, under the supervision of Dr. Kevin Fu. During her internship with Dr. Jie Liu's Sensing and Energy Research Group (SERG) at Microsoft Research, Negin researched trustworthy operation of Near Field Communication (NFC). She has received the Outstanding Synthesis Project award (Sponsored by Yahoo) for her work on probabilistic storage. Negin was one of the top four finalists of UMass Innovation Challenge Award. Her research focuses on low-power and trustworthy operation of pervasive computers, energy management, and probabilistic storage. Her research goal is to make low-power computers (specially batteryless ones) more energy-aware and more robust. During her PhD studies, Negin served as the co-chair of CS Women group at UMass Amherst for a year and she has attended several outreach events for girls in IT.

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