[Tinyos-help] Varying signal strength on Telos motes.

Youssef Chraibi chraibi at kth.se
Thu Sep 1 10:02:11 PDT 2005

Hi everyone !

I was running some experiments regarding the RSSI on the Telos motes, and
I had some results that are a bit strange to me, so I'd like to know if
anybody has an idea on those 2 or 3 questions.

First of all, is the emitting power conditionned by the battery voltage ?
I was trying to trace it out in the code, but didn't really manage. As far
as i understood the nodes should be emitting at full power. I am just
using the CntToLedsAndRfm application, and modified my TOSBase to display
the RSSI and LQI values. When I run with middle age batteries, 2.4V, I
have lower RSSI than with brand new ones having 3.3V.

Then I used exactly the same batteries, but changed the motes. I made my
measurements for only one spot (5 meters away indoor), with four different
motes, and
was surprised to see that the RRSI differs. That was ranging from -55 to
-65 dBm, even if every single signal was quite clean and stable. Have you
ever experienced such behaviour or heard about it ? I don't see what could
explain this from the hardware side, the motes being the same, and
purchased at the same time.

I would be very gratefull if someone has some ideas on those !

Thanks a lot for your time !



Youssef Chraïbi <chraibi at kth.se>
KTH - Stockholm - Sweden

Mobile: +46 737 25 46 23

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