[Tinyos-help] relationship between RSSI and distance

[CASTEL Myriam]

Hello,

I'm trying to use RSSI value to obtain the distance between two sensor 
nodes mica2.
I know that a lot of such experiments are made and that a lot of people 
use this method.
However, when I do the experiment, I obtain unexploitable results:
- between 0 and 70 cm, I obtain always the same RSSI.
- above 150cm, all values of RSSI are possible.
More strange: i do the same with micaz, and the results are exploitable.

For information, I am using rcv_packet->strength to obtain RSSI knowing 
that the transmitted power is always the same.

Can anybody tell me if it possible to use mica2 and RSSI to obtain 
distance and if yes, how to do that and why I didn't manage?


Thanks for your help.