Introduction
Over the last year or
so you may have heard about a new computing concept known as motes. This
concept is also called smart dust and wireless sensing networks. It seems like
just about every issue of Popular Science, Discover and Wired today contains a
blurb about some new application of the mote idea.
Intel Mote Hardware
The Intel Mote has
been designed after a careful study of the application space for sensor
networks. We have interviewed a number of researchers in this space and
collected their feedback on desired im-provements over currently available mote
designs.
A Typical Mote
MICA mote is a
commercially available product that has been used widely by researchers and
developers. It has all of the typical features of a mote and therefore can help
you understand what this technology makes possible today. MICA motes are
available to the general public through a company called Crossbow. These motes
come in two form factors:
• Rectangular, measuring 2.25 x 1.25 by 0.25
inches (5.7 x 3.18 x.64 centimeters), it is sized to fit on top of two AA
batteries that provide it with power.
• Circular, measuring 1.0 by 0.25 inches
(2.5 x .64 centimeters), it is sized to fit on top of a 3 volt button cell
battery.
Bluetooth Based Mesh Networks
Bluetooth was originally
designed for personal area networks (PANs) that are quite different from the
application that we had in mind. PANs are often simple star network topologies
that consist of a sin-gle master and a number of attached slaves. A very simple
example would be a BT-enabled cell phone nd wireless headset (a point to point
connection consisting of a single master and single slave). A more complex
network could involve a PC as the master with mouse, keyboard and printer
attached as wireless slaves. Such a network is called a piconet in the BT
specification.
For a number of
sensor network applications that use battery powered nodes, low power
consumption is essential. In order to support this, the Intel Mote employs a
number of power reduction schemas. The overall platform can be brought to a low
power state when no active computation of communication is ongoing. In this
mode, power consumption is about 1mW or less. In addition, the Bluetooth
protocol allows for the radio to enter low power states in-between active
communication slots. Special commands allow devices to enter “hold”, “sniff” or
“park” modes.
Conclusion
We have described the
design of a new enhanced sensor network node, called the Mote. This device
provides enhanced CPU, storage and radio facilities that various sensor network
application developers and implementers have been asking for.
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