smtp

Login to the NWA-3160N’s console via SSH and use the CLI commands to show the RSSI.
show wlan wds all
show wlan slot1 list all sta
If you are more comfortable with a dBm value , then you could subtract 95(Atheros chipset) from the RSSI to derive the dBm value.
For example:
RSSI = 85
dBm = 85-95 which is -10
However, it is only an approximate value, not accurate.
Refer to the link below for details.
http://tomatousb.org/tut:measuring-rssi-with-wifi-cards