Stumbling Software
Software that you use for a site survey is often refered to as a "stumbler" because you can stumble across wireless networks that you didnt know about before. It gives you an update about what the radio in your wireless network card receives through the antenna.
SSID
The information you receive is the following and ESSID which is a piece of text used to identify the wireless network. Airstream networks have an ESSID in teh following format "Air-Stream-Suburb-Name".
Signal, Noise and -dBm
Stumbling software also allow you to see the recieved signal strength intensity "RSSI" or signal strength. Along with the signal you will also see a certain amount of background noise. Ideally you want all signal and no noise. Or at least more signal than noise, hence we have a signal to noise ratio(SNR) we want a really high SNR. Both signal and noise are typically measured in -dBm which is a negative log scale.
What is a good signal?
The weakest signal is around -100dBm and the strongest signal is around -10dBm each 3dBm closer to zero is a doubling in signal. If you have a signal of -80 dBm to -1dBm you can get a decent 11Mbps link, with a signal of -90 dBm to -100 dBm your link will have problems and packet loss.
Also a SNR of at least 5 is required.
Scanning through channels
There are 13 channels on the 802.11b range of frequencies. A wireless card reads from the radio tuned into one channel at a time so it may take some time to scan through all channels, you can also lock a piece of stumbling software into one channel to focus on a particular AP on a given channel giving you better feedback rather than hoppign through all channels at once.
Netstumbler and Ministumbler http://netstumbler.org
And an excellent Windows application, with a full GUI, compatible with most wireless cards, including Prism chipsets (Senao) and Hermes chipsets (Orinocco, Lucent, Cabletron). The graphical feedback is easy to interpret at a glance.
Screenshots
Kismet
POSIX (Linux, BSD, Unix) based software. Good for identifying networks but difficult for determining signal strength, uses a scale of 0-255 from minimum to maximum and doesnt seen to isolate the signal to noise ratio per SSID. A small kismet drone or drones can be placed on a remote access point and relay packets to a kismet server. The kismet client then connects to the kismet server and displays the data as a text display. The client and server can be on the same physical system or on seperate systems connected by a network.
Screenshots
Wavemon
POSIX based software, uses the ncurses text package to display signal strength and other information graphically.
Screenshots
dstumbler
BSD
Screen shots
