6 ms. Every time it wakes up, it follows the
following pattern: it consumes 0.035 mA during the 27.6 ms that the XSM is
sleeping, it consumes 0.4 mA for the next 0.8 ms, 0.75 mA for the next 2.25 ms,
and 6.35 mA for the next 0.5 ms, after which the 27.6 ms of sleep period follows.
With careful configuration and some hardware improvements, the value of ilpl
slp
may be brought down to 0.035 mA, which will significantly increase an XSM??™s
lifetime.
273 Chapter 11 Maximizing the Lifetime of an Always-On WSN Application
Santosh Kumar, Anish Arora, and Ten H. Lai
3. ilpl
sample - The average current consumed by an XSM in sampling the
channel every time the radio wakes up. By measurement on an XSM,
we found that ilpl
sample = 9.6571 mA10.
4. tlpl
sample - Time taken to sample the channel every time the radio wakes
up to sample the channel. By measurement on an XSM, we found that
tlpl
sample = 0.014 seconds.
Using the above values, we obtain
ilpl =
ilpl
slp ?¤ tlpl
slp + ilpl
sample ?¤ tlpl
sample
tlpl
slp + tlpl
sample
=
0.1974 ?¤ tlpl
slp + (9.6571 ?¤ 0.014)
tlpl
slp + 0.014
. (1)
mpr: Number of control messages transmitted every hour. With the configuration
used in the ExScal application, every XSM sends three routing
messages and one time synchronization message every minute, for a total
of 240 messages every hour. Therefore, in ExScal, mpr = 240.
me: Number of event-detection messages generated by the heaviest-loaded
XSM every hour.
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