??? Reducing the Transmitter Power Level: With the radio used in XSM
and in motes from the Mica family, the energy consumed in transmission
depends on the power level used. Using a lower power level means lower energy
consumption at the expense of a reduced transmission range. Using a
lower transmission range also means lower interference in the network. On
the other hand, using a lower transmission range can result in more hops
in a multi-hop network. The reliability of transmitting a packet across
multiple hops decreases as the number of hops increases in the path of
the packet. Therefore, a careful analysis should be performed before reducing
the transmission range to ensure that the connectivity and packet
reliability requirements of the application are still met with a reduced
transmission range.
There may be more fine-grained approaches to extend the lifetime of a WSN
than what we have discussed in this chapter. An application developer should
explore all these options before deciding to deploy redundant sensor nodes or
redundant batteries in order to get a desired lifetime from the network.
265 Chapter 11 Maximizing the Lifetime of an Always-On WSN Application
Santosh Kumar, Anish Arora, and Ten H. Lai
3 The ExScal Application and the XSM Platform
In this section, we provide an overview of the ExScal application [2], an
overview of the sensor platform used in ExScal (called XSM) and the major
requirements (or features) of ExScal that have a significant impact on its
lifetime.
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