The digital sensors were interfaced directly using a serial
interface, while the analog sensors used an Analog-to-Digital Converter
for interfacing. Two types of sensor nodes were designed: burrow nodes for
detecting occupancy and weather nodes for monitoring the surface microclimates.
The body of the sensor nodes was sealed, but the sensing elements
were exposed to the environment. The nodes were deployed manually, burrow
nodes being inserted unobtrusively into the burrows of the storm petrels, and
weather nodes being deployed on the ground surface. The nodes were powered
with lithium batteries, and were expected to have a lifetime of around
100 days. The nodes were not expected to have significant mobility.
Network Architecture
A multi-level, hierarchical, data-gathering sensor network architecture was
used in this experiment. At the lowest level in the hierarchy, a group of closely
spaced sensor nodes would communicate with a gateway node using either a
direct transmission or multi-hop relaying. The gateway nodes, which form the
next level of the hierarchy, were programmed to communicate with a remote
sink located about 350 feet away, through a local transmit network. The sink
provided a database service and a satellite Internet connection, so that the
sensor data could be analyzed remotely. The gateway node is nothing but a
relay node with a high gain directional Yagi antenna.
The entire sensor network was divided into two parts, a single-hop based
network, and a multi-hop based network, in order to experimentally compare
and contrast the two modes of communication.
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