wscan(1)

NAME
wscan - Wifi Signal Scanner

SYNOPSIS
wscan [-P] [-i ifname]

DESCRIPTION
wscan is intended as a visual signal strength meter, primarily for Lucent/Orinoco 802.11 wireless cards. It will show the quality, signal strength, and noise in a visual manner. It may also be used to dynamically learn the ESSID in managed mode. It is read-only. It more or less uses the same background wireless instrumentation on Linux as the wireless tools, iwconfig, and iwspy. or wicontrol on FreeBSD. It is intended to run on FreeBSD, or Linux systems. In addition to Lucent cards, it can work (but with less information) on the prism2 cards.

SWITCHES
-P Forces wscan to use the correct range for a prism2 card. Without this switch, the range values are wrong, and the meters will not work correctly. -i <ifname> can be used to tell wscan the name of the desired interface.

WINDOW OVERVIEW
Wscan has two main windows, which we will call the multi-source window, and the more detailed single-source window (aka the detail window). Right now, wscan starts with the multi-source window. In managed mode, that window shows one access point's quality. In ad hoc mode, (more details below), there can be one to five sources. The single-source window shows signal (level), noise, and quality bars, as well as various important details, including the cell's ESSID, and source's MAC address.

MULTI-SOURCE WINDOW
The multi-source window currently shows only one access point in managed mode. In ad hoc mode, it may show multiple sources depending on cache loading (see HINTS below). Each meter shows the quality value, scaled in percent from 0..100. The "true" hardware value is also shown in the little yellow box. Note that the true hardware value is not in decibel units. The multi-source window has four buttons at the top. list - shows a list of sources. You may select one, and then click on the detail button to go to it. poll interval - Can be used to change the default polling interval. detail - Clicking on this box takes you to the selected single-source window to show more details.

close exits the application.

SINGLE-SOURCE DETAIL WINDOW
This window shows 3 meters, one each for signal strength, noise, and quality, which is merely signal - noise. Meters are scaled to 100%. The hardware value is shown below the meters in the little yellow boxes. Every time a sample is taken, a history dot is placed next to the bar on the right hand side of the individual meters. Mode, MAC address (for the source), ESSID, channel, and possibly an IP address in ad hoc mode, may be shown. The detail screen has three buttons at the top, and a fourth "log" bottom at the side: change - go back to the multi-screen. reset - reinitializes the history values; i.e., it erases them. close - quits. log - the log button invokes a program named "/usr/local/bin/wscanlog.sh", and passes it various parameters (see the included shellscript that is installed in /usr/local/bin along with wscan itself). This script may be modified for any purpose.

HINTS/DETAILS
The hardware values shown in the yellow bars are different from the "negative" values shown with the BSD wicontrol , and Linux iwconfig commands. This is because for the Lucent cards, the hardware ranges for signal and noise are 47..138. The drivers subtract 149 in order to covert this to a DBM measurement. Of course, this also makes wicontrol/iwconfig print out signal and noise as a negative number. Wscan adds 149 back in order to keep the values positive, thus the range remains 47..138 for the hardware values in wscan. Quality on the other hand ranges from 0..92. Ad hoc mode on Linux is dependent on the operation of iwspy(8). On BSD, it is based on the signal-strength cache in the wi driver. See wicontrol(8) for details. The caches may need something in them to be useful. You may want to use ping in some cases to help you gauge signal strength. The Lucent card can automagically learn the ESSID if the ESSID is programmed to "". E.g., the following example BSD script MAY reset wscan so that it can learn any new ESSIDs with Lucent cards:
# wicontrol -i wi0 -p 1
# wicontrol -i wi0 -n ""
# wicontrol -i wi0 -Z The first command sets managed mode. The second command sets the ESSID to the magic "null" string. The third command zeroes out the signal strength cache in the driver. Lucent note: wscan is oblivious to the difference between Lucent ad hoc "demo" mode and true IBSS ad hoc mode. There is no discernable difference as far as it is concerned. prism2 note: (e.g., D-Link card) Under the FreeBSD wi0 driver, it is possible to get signal strength from the prism2 cards. However, there is no noise value. The signal strength range is set to 0..255.

SEE ALSO
On FreeBSD, see wicontrol(8) On Linux, see iwconfig(8) and iwspy(8)

AUTHORS
Written by Ginny Mak and Jim Binkley, Portland State University