As many of these species are endangered,
they are of particular interest to researchers, environmentalist groups, lawmakers,
and to the general public. Successful sensor network implementation
to study these large mammals would be of immense help in gathering the
necessary data to study the environmental impacts of human activities.
Node Architecture
A SWIM node consists of a Texas Instruments microprocessor, MSP430, with
60 KB of flash memory, and a 32 KHz quartz crystal reference for maintaining
the clock. The radio transmitter of the node uses a Silicon Labs Si4112 Phase
Lock Loop that is controlled by the MSP430 processor, and can generate a
carrier frequency of 62 MHz to 1GHz. The node can implement pulse interval
coding or frequency shift keying, for data communication. Various sensors such
as pressure, light, and temperature sensors, accelerometers, and electrodes can
be controlled through the microprocessor. The microprocessor has a small
dormant power consumption, and to minimize the energy consumption, the
node can employ duty-cycling.
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Node Mobility and Network Architecture
The total area spanned by the whales, or equivalently the range and the area
that needs to be monitored, is very large, possibly covering thousands of square
kilometers of deep sea. However, the high mobility of the whales provides an
elegant solution to this problem. In SWIM, a sensor node is directly attached
to the body of a whale.
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