Measurement of S-MAC Energy Consumption

Mohammd Rahimi
UCLA Center for Networked Embedded Sensing
January 2004

These measurements are performed with a snapshot of S-MAC code in CVS in January 2004. The timing and energy consumption are measured on Mica2 motes with an oscilloscope. S-MAC is configured to run at 10% duty cycle.

This is the Image of the active time:

Theses are the timings:

*Here when the CPU come out of sleep it takes 4.2ms for CPU comes out
  IDLE mode and the radio becomes ON
*The lenght of the whole cycle is 120.4 which part of it is 4.2 second.(If usefull
   we can see realy when the radio gets on)
*there are two packets being send.
*Sync packet is the smaller packet which took 13.4ms
*Data Packet which is longer (payload=8) and took 19.4ms

activeInterval.jpg

This is the image of the sleep time:

Here the sequence of sleep wake up is clear
* The sleep time is 1084 second

sleepCycles.jpg

Result and Notes:

*Duty cycle is 120.4/1084 which is 11.07%
*The current in IDLE mode is 3.1mA
*The current in listen is 11.95mA
*Average current is about 3.1*0.9+11.95*0.1= 3.98
*Life time increas is 11.95 /3.98 = 3.00

*In this calculation the effect of transmission has not been considered but since we are using radio at 0dbm output power the difference between transmssion power consumption and reception power consumption of the radio is not huge(from the first figure) and it only short period of time so it is well neglible.