Mercury is a sensor network platform designed to supports applications that are data-intensive and can gracefully adapt to fluctuations in resource availability and load. Key challenges addressed by Mercury include long sensor node lifetime, autonomous operation, and the need for the system to automatically tune its behavior in response to fluctuations in radio bandwidth and energy availability.
We are currently working with the Motion Analysis Laboratory at Spaulding Hospital to develop a prototype of this platform for long-term motion analysis studies in a home setting. A Mercury network consists of a number of wearable sensors and a base station installed in the patient's home. Each sensor samples multiple channels of accelerometer, gyroscope, and/or physiological data and stores raw signals to local flash. Sensors also perform feature extraction on the raw signals, which may involve expensive on-board computation. The body sensor network performs opportunistic data transfer to the base station, based on the quality of the radio link to each sensor and the remaining battery capacity. Each node dynamically tunes the number of data transfers and degree of computation applied to the sampled signal to meet a target lifetime (say, 12 or 24 hours). Nodes also save energy by dropping down to a low-power state when the sensor is not moving.
An earlier version of Mercury (v1.0) is being used in several studies by the Motion Analysis Lab at Spaulding Hospital.
We are using a range of wireless sensors in this project. Our current hardware platform is the SHIMMER wearable mote, developed by the Digital Health Group at Intel. SHIMMER incorporates a TI MSP430 processor, CC2420 IEEE 802.15.4 radio, triaxial accelerometer, and rechargeable Li-polymer battery. SHIMMER includes a MicroSD slot supporting up to 2 GBytes of Flash memory. This allows SHIMMER to store significant amounts of data (2GB can store more than 80 days of continuous triaxial accelerometer data sampled at 50Hz). SHIMMER can also be configured with an optional Bluetooth radio.
SHIMMER devices are now available commercially from www.shimmer-research.com.
|The Intel SHIMMER mote, including a triaxial accelerometer.||The SHIMMER mote connected to its programming board.||SHIMMER sensors being worn on a patient's arm.|
Our previous hardware platform is the Pluto mote, designed here at Harvard, which is a scaled-down version of the Telos designed to be small, lightweight, and wearable. The Pluto incorporates a tiny, rechargeable Li-ion battery, small USB connector, and 3-axis accelerometer.
|The Harvard "Pluto" mote, designed to be small and wearable.||Pluto mote with case and wriststrap.||Pluto mote in case.|
You can download Mercury from the following link:
Mercury VMware image (1.8 GB)
(includes, Pixie, TinyOS 2.x, and all other dependencies - unzip and read the instructions.)
This page will be updated soon with more details!