Fine-grained power management
schemes do not require deploying any more sensor nodes than are absolutely
necessary to meet the monitoring requirements of an application.
??? Coarse-grained Power Management: In this approach, more sensor nodes
are assumed to be deployed than are necessary to meet the monitoring and
notification requirements of an application. The redundancy in the number
of sensor nodes is then exploited to increase the network lifetime. Time is
divided into intervals and in each interval, only that many sensor nodes
are active as are necessary to provide the desired level of monitoring. The
redundant nodes are put into deep sleep by putting all their components
(the processor, the radio, and all the sensors) to sleep. The nodes that
remain active are sometimes called sentries [15].
These two approaches are complementary in the sense that we can first use
fine-grained power management schemes to extend the active lifetime of individual
sensor nodes by the maximum extent possible. If this extended active
lifetime of the sensor nodes still falls short of the desired lifetime of the network,
coarse-grained power management schemes can be used to extend the
network lifetime further. Another alternative to using coarse-grained power
management schemes (which will require deploying redundant sensor nodes) is
to deploy redundant batteries per node or to use more expensive but higher capacity
batteries.
Pages:
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426