However, role rotation is no longer possible in such heterogeneous networks. In
[33, 34], the authors present a cost-based comparison of homogeneous and heterogeneous
networks, and provide guidelines to choose the most cost-optimal
architecture for a given scenario.
Mode of Communication
In a clustered sensor network, in order to communicate with their respective
clusterheads, the sensor nodes can either use single hop or multi-hop mode of
communication. The problem of determining the optimum mode of communication
has been studied in [33]. The authors also propose a hybrid mode of
communication that the sensor nodes can use if they have power control capabilities.
This hybrid mode of communication is a combination of single-hop
and multi-hop modes, and results in a more uniform energy drainage pattern
across the network. In [33, 34], the authors also determine the optimum
communication range when multi-hopping is used within the clusters.
5.3 Sink-initiated Querying
In several application classes, the sink is not interested in data updates from all
the nodes in the network. The sink may want updates from di?®erent regions
at di?®erent times. Thus, requiring all the nodes to send their data to the
sink at all times amounts to wastage of energy on communication as well as
computation. In such cases, the sink selectively queries a set of sensor nodes
located in the region of interest. This results in a more energy-e?±cient use
of resources.
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