However this would require considerable
storage at each node, since a node may potentially visit every
other node before reaching the sink. Other packet replication strategies
that are proposed in [46] are: (i) replicating packets with a certain probability,
(ii) maintaining a record of packets that have already been o??oaded
to the sink, so that these packets need not be reacquired from other nodes,
(iii) maintaining a record of o??oaded packets, and also informing other
nodes about these packets, so that they can safely erase these packets
from their memory, etc. See [46] for details on the packet replication and
erasure strategies.
4. Packet Replication and Energy Expenditure: Besides a?®ecting the
packet delivery delays, the packet replication strategy also impacts the
energy expenditure of the sensor nodes. For example, consider a packet
replication strategy that is aggressive in terms of erasing redundant information,
i.e., information that is already conveyed to the sink. Such a
scheme results in lower storage requirements at each node. However, it
also requires additional communication between the sensor nodes so that
all the nodes are aware of all the packets that have already been delivered
to the sink. This additional communication results in higher battery
energy expenditure for all the nodes.
Thus, we note that the solution of tagging the whales with sensor nodes
to monitor them presents several interesting and challenging design problems.
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