Is that RSSI percentage value cut off at a certain point or does it span somewhat linearly from the entire range of dBm values (-102 to +17)? I understand that the NI WSN nodes aren't quite the same as a Wireless NIC but many of them measure RSSI to a certain point, making values of dBm which are less than the maximum achievable also appear as 100%. There is an article I found (http://www.wildpackets.com/elements/whitepapers/Converting_Signal_Strength.pdf) that explains it as follows (on page 8):
The effectiveness or reasonability of using dBm measurements obtained from a standard
wireless NIC is questionable when used as part of a real-world network troubleshooting
exercise. This is because most NICs only provide RSSI in a range that is below –10dBm,
and everything above that is mapped to RSSI_Max (or, 100% signal strength).
When using the NI WSN nodes then, if I was receiving a signal strength of -5 dbm, might that show up as ~80% {i.e. (-5 + 102) / (17 + 102)}, or does the WSN also have a similar cutoff that might make values of -5dBm, +10dBm, etc all appear as 100%, until they are less than a predetermined value? And if so, what is that value? We are using these values to roughly estimate the degree to which obstacles interfere with the signal, and knowing the minimum dBm that could result in a signal strength value of 100% would help make our estimates more accurate.
Thanks!
Garrett
