sustained collisions were caused by the faulty node behavior due to severe
environmental conditions. It was observed that because of the node
failures, the network size reduced over time. Even though this improved
the packet losses by reducing the packet collisions, smaller network size
compromised the objective of deploying a sensor network. Hence a proper
sensor node packaging to protect from harsh weather conditions is necessary.
4. Node Reclamation: Due to the environmental impact and sensor node
costs, it was necessary to recollect the sensor nodes deployed in the field.
However only half of the deployed sensor nodes could be recollected. The
rest of the nodes were unrecoverable and might have been moved by animals.
As the sensor networks become larger and more prevalent, node
reclamation would become an important issue in the design of the wireless
sensor networks, due to pollution and cost concerns.
Thus these experiments provided valuable insights into the functioning of an
unmanaged sensor network. Specifically, it showed that the problems of MAC
and end-to-end reliability are important issues for a data gathering sensor
network even with low tra?±c density. The importance of these issues could not
have been foreseen without these experiments. Details of these experiments
can be found in [47, 48].
6.2 The Shared Wireless Infostation Model (SWIM)
Objective
The SWIM architecture [46] was developed to study the impact of natural and
man-made environmental conditions on the behavior and mobility patterns of
whales and large marine mammals.
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