The best wakeup sensor is the one that draws a small
current. For the sleeping sensors, it is important to have a low startup time
so that when they are woken up, they do not miss an event. In Section 4.5,
we show that by using hierarchical sensing (with PIR sensor as the wakeup
sensor) together with LPL we can extend the lifetime of ExScal by 12 times.
2.3 Other Fine-grained Power Management Schemes
There are several other fine-grained power management schemes that can be
used in an always-on application to extend the network lifetime. Some of these
are:
1. Reducing Periodic Messages: Reducing periodic control messages can
result in significant lifetime extensions. The lifetime of ExScal can be increased
by 31.6% if there were no periodic messages.
2. In-Network Data Aggregation: Aggregating the event detection messages
as it flows towards the base station can also extend network lifetime.
In ExScal, using data aggregation can result in a lifetime extension of upto
8.91%.
3. Reduced Control Operations: Reducing the number of control operations
such as wireless reprogramming results in further lifetime extensions.
4. Reduced Actuations: Actuations such as blinking LEDs and sounding
buzzers can consume significant energy. For example, keeping even one
LED continuously active will reduce ExScal??™s lifetime by more than half.
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We provide the details of calculation on how to analyze the e?®ect of the above
schemes on the lifetime of a WSN in Section 4.
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