In another case the soldier may ask: ???How many
tanks are there in the battlefield at the time 4:00 pm???? As a result, none of
the single rendezvous nodes can reply with a complete answer. Collaboration
among the groups is needed. Rendezvous nodes can combine receiving replies
with its own data, and proceed with aggregation before sending out further
replies . This will help reduce bandwidth consumption. Alternately, raw data
are directly forwarded to the soldier to minimize delay.
s
A
B
C
ADV
REQ
Fig. 8. Illustration of the quorum-based object tracking.
Similarly, if one tank moves from place A to place C via place B (Figure 8),
the quorum based method still works well. For example, the soldier requires:
???Report back the location of the tank every 30 seconds.??? Sensor nodes will
disseminate information detection whenever a new tank moves into its range.
But rendezvous nodes in the row will take an aggregation, and only reply with
the location of the tank every 30 seconds. Alternately, a mechanism adjusting
the frequency of new location information dissemination is added, so that the
number of columns is limited.
B. Frequency Consideration
Recall that due to the ???void areas??? mentioned in Subsection 3.2.2, face
routing should be added to guarantee that any update information could
arrive at an extreme point of the network. However, the negative a?®ect is
that nodes on the perimeter of a network will also execute face routing due
to its lack of global information.
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