I took a friend to a VA hospital today. I took my MacBook Pro laptop with me and while I was there I used the wireless guest service at the facility. The performance of the wireless service was awful today as it was on a previous visit. To determine if the problem might be attributable to signal strength, I used the
airportcommand, which is available on OS X systems. The utility is located in
/System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/. Help information on the command is available using
$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -h Supported arguments: -c[<arg>] --channel=[<arg>] Set arbitrary channel on the card -z --disassociate Disassociate from any network -I --getinfo Print current wireless status, e.g. signal info, BSSID, port type etc. -s[<arg>] --scan=[<arg>] Perform a wireless broadcast scan. Will perform a directed scan if the optional <arg> is provided -x --xml Print info as XML -P --psk Create PSK from specified pass phrase and SSID. The following additional arguments must be specified with this command: --password=<arg> Specify a WPA password --ssid=<arg> Specify SSID when creating a PSK -h --help Show this help
To view the status for a wireless connection, use
$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I agrCtlRSSI: -67 agrExtRSSI: 0 agrCtlNoise: -86 agrExtNoise: 0 state: running op mode: station lastTxRate: 7 maxRate: 144 lastAssocStatus: 0 802.11 auth: open link auth: none BSSID: ec:44:76:81:e4:40 SSID: VA Internet MCS: 0 channel: 11
The signal strength for a connection is the value for
agrCtlRSSI. "RSSI" stands for
received signal strength
indication. The higher the number, the stronger the wireless signal.
The maximum value that may be reported will depend on the wireless
devices being used. Cisco Systems wireless cards have a maximum value of
100 while Wi-Fi chipsets from Atheros will return a value from 0 to 128.
For Apple OS X systems, the value will range from a high of 0 down to
minus 100 (-100). The closer the number is to zero, the stronger the signal
while the closer the number is to negative 100, the weaker the signal
Since I only wanted to check the signal strength initially, I looked just for that value. The signal strength seemed to be ok for the waiting room I was in, though not terrific.
$ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I | grep agrCtlRSSI agrCtlRSSI: -74 $ /System/Library/PrivateFrameworks/Apple80211.framework/Versions/Current/Resources/airport -I | grep agrCtlRSSI agrCtlRSSI: -68
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