Lab11

Embedded Systems Research at the University of Michigan

The Internet of Everyday Things will bring a trillion new wireless, embedded, and networked systems online within a decade or two. Our work explores how these systems should be built to survive and thrive in this not-too-distant future, and how they can be prototyped today to enable breakthrough applications.


Harmonia. Cheap, accurate indoor localization with RF.

Ultra-wideband has been shown to achieve order-cm RF-localization accuracy, yet it is prohibitively expensive to implement in practice.

Harmonia seeks the best of both worlds, leveraging affordable, low-energy narrowband frontends with a novel mixing scheme to generate ultra-wideband (UWB) signals. These signals are captured using a tunable narrowband receiver that sweeps the spectrum, stitching together a complete UWB picture.

Harmonia is designed as an assymetric tag and anchor system. Lightweight, low-cost, low-energy, low-complexity tags are distributed in free space. These tags mix the output of a narrowband radio with a square wave to generate a UWB signal. Anchor nodes with a highly tunable narrowband frontend quickly sweep the spectrum and stitch together samples to form one, unified UWB capture.

Our Harmonia prototype captures 56 location samples/second, enabling location tracking with both high temporal fidelity and high resolution in 3D space.

View project page

VLC Localization. Positioning with LED lights and smartphones.

Consumer GPS changed the world. Knowing one's location and the ability to locate objects enabled whole fields of technologies. Yet there is no effective system for accurate indoor localization.

Most state-of-the-art indoor localization systems provide semantic localization, answering "Where Am I?" by telling the user what room or area of a room they are in. We aim to provide true localization, in practice this amounts to order 1 decimeter accuracy in 3D-space.

To achieve this, we exploit the rolling shutter of the CMOS imager in modern smartphones. By modulating (blinking) LED lights at high frequency (1-7 kHz) each light appears solidly on to any people in the room while communicating data to any smartphone in the room.

View project page

GridWatch. Monitor the grid.

The power grid is one of humanity's most significant engineering undertakings and is essential in developed and developing nations alike.

Currently, transparency into the power grid relies on utilities and more fine- grained insight is provided by costly smart meter deployments. We claim that greater visibility into power grids can be provided in an inexpensive, crowdsourced manner independent of utilities by leveraging existing smartphones. Our key insight is that an unmodified smartphone can detect power outages by monitoring changes to its own power state, locally verifying these outages using a variety of sensors, and corroborating with other phones through cloud services.

View project page

Opo. Ultrasonic ranging.

Capturing the human inter-contact matrix allows one to understand real-world social dynamics and their implications in a number of areas, such as epidemiological studies, informal informational networks, and childhood social development.

Smart phones are limited by their inaccurate and/or impractical ranging and orientation capabilities and other deployability issues. Smart badges constitute another approach to capturing such dynamics, but their bulky form factor, limited life time, and poor ranging ability have limited their use in practice. The key problem stems from the unpredictability of mobile neighbors, which makes synchronization and neighbor discovery difficult, resulting in either bulky, high powered nodes or infrastructure heavy systems.

View project page

Monjolo. Energy-harvesting energy meters.

Conventional AC power meters perform at least two distinct functions: power conversion, to supply the meter itself, and energy metering, to measure the load consumption. This paper presents Monjolo, a new energy-metering architecture that combines these two functions to yield a new design point in the metering space.

The key insight underlying this work is that the output of a current transformer -- nominally used to measure a load current -- can be harvested and used to intermittently power a wireless sensor node. The hypothesis is that the node's activation frequency increases monotonically with the primary load's draw, making it possible to estimate load power from the interval between activations, assuming the node consumes a fixed energy quanta during each activation. This paper explores this thesis by designing, implementing, and evaluating the Monjolo metering architecture.

View project page

M3. Millimeter-scale computing.

Pushing the leading edge of technology, M3 seeks to build a modular, composible, general-purpose sensing and computation platform at millimeter-scale.

The goal of the Michigan Micro Mote (M3) project is to finally realize the Smart Dust vision: networks of integrated, autonomous, energy-harvesting nodes that can sense the environment and deliver their data over a wireless mesh network. The concrete goal of the project is to: (1) create sensor nodes that are cubic-mm in size, (2) draw ~10 nW, and (3) deliver data every few minutes over a multihop network. This requires advances in every layer of the system stack -- circuits to memory to processor to timers to radios to interconnects to packaging to software to protocols to programming models. If successful, this represents a 1,000-10,000 fold improvement over the state-of-the-art in size and power.

View project page

EKG Sensor. The mobile phone as a medical instrument.

We believe that any hospital, village clinic, or doctor can have access to advanced health care instruments like an EKG monitor for little more than the cost of a mobile phone.

Health care facilities in developed countries have access to a large number of medical instruments unavailable to health care professionals in the developing world. One example of such an instrument is the EKG monitor. EKG signals are used to diagnose a wide range of medical conditions but they are often unavailable in all but the most advanced hospitals in developing countries like India, Ghana etc. We aim to design a low-power, low-cost EKG monitor that uses the "HiJack" platform for interfacing between the EKG sensor peripheral and the mobile phone, and the mobile phone for visualizing the ECG waveform.

View project page