The package wireless-tools
contains utilities that allow to set wireless LAN specific parameters and
get statistics. See
http://www.hpl.hp.com/personal/Jean_Tourrilhes/Linux/Tools.html
for more information.
kismet (package kismet) is a
network diagnosis tool with which to listen to the WLAN packet traffic.
In this way, you can also detect any intrusion attempts in your network.
More information is available at
http://www.kismetwireless.net/ and in the manual page.