Introduction: Bird’s-Eye View of Wireless Sensor Networks - Application and Multidisciplinary Aspects of Wireless Sensor Networks - page 5

d
E = K* d 2

E = K* d 2 /4 E = K* d 2 /4

Fig. 1.4 Energy conservation through deployment into energy efficient topologies

Power

Task

Reduced voltage
and frequency

Time

Fig. 1.5 Energy conservation through variable voltage processing

gets stuck in an infinite loop, needlessly expending energy; using sleep states; and
finally, variable voltage processing, which exploits the fact that with decreased
processing frequency (which allows processor voltage to be slightly dropped), some
tasks may take longer to finish, but the power/time product might be smaller thus
yielding smaller overall energy consumption (Fig. 1.5 ) [ 4 ].

1.3.2 Routing

Due to energy considerations, the primary criteria for selection of the best route
in computer networks - “shortest path” - cannot be directly applied to sensor
networks. The reason for this is that in such schemes, the same nodes will always
be used to relay traffic to the gateway using the “shortest path,” and will eventually
run out of energy.