Sensors get activated and could form dynamic clusters on detecting
a target identity. These clusters could then be used to perform target
localization. In the following subsections, we look at these problems.
Location determination
Location determination is an important problem for almost all WSN applications.
However, it becomes particularly important in case of tracking-based
applications, since the whole objective of the sensor network is to track a particular
target. In this case, the problem of location determination is at two
levels. Firstly, the sensor nodes themselves need to determine their location
at an appropriate level of granularity. Secondly, the sensors have to localize
the target, at various time instants. The two desirable features of any such
location determination scheme are (i) robustness [38] and (ii) energy-e?±ciency
[58, 36]. By robustness, we mean that the scheme should be able to produce
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an accurate location estimate of the target in spite of variations in the radio
channel, or changes in topology due to node failures or duty-cycling. By
energy-e?±ciency, we mean that the localization should be done at the desired
level of resolution, at the minimum possible cost in terms of energy consumption.
There is an inherent conflict and tradeo?® between the energy expenditure
and accuracy of the target localization. This is explored in [36].
Dynamic clustering
The problem of formation and maintenance of dynamic clusters (sets of sensors),
which can collaborate on target localization and report time-stamped
location estimates of the target to the sink, is considered in [16, 10].
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