UCR CS 122B
Winter 2004
Prof. Frank Vahid                     Name: ____________________________

Quiz 3


1. Presently, a SmartDust chip is a mere 4 cubic millimeters (wow!). 2 cubic 
   millimeters of that is battery, and the battery stores about 2 Joules. 
   The chip, when active, runs at about 10 microwatts (which, by the way, 
   includes the analog-digital converter, light sensor, oscillator, state 
   machine, and communication send and receiver). 

   (a) How long can the device operate continuously in active mode?





   
   (b) Suppose the chip has a sleep mode that consumes 1 nanowatt.  You
       want the chip to wake up every X seconds, sample the light, and
       transmit. Assume each such sample requires 1 millisecond of active
       chip time.  You want the battery to last for 1 year.  Can you achieve
       1 year of battery lifetime? If so, what is X?