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What is a carrier busy test?



Many factors prevents the successful transmission and reception of  wireless packets. With most common reason being interference and noise  carrier busy test is used to check the radio activity on 802.11 channels in the range of the device. During the carrier busy test, the device drops all associated wireless clients for about four seconds ,stops transmitting and listens the wireless medium on all 802.11  channels.  The result displays how far each channel is occupied with the traffic other than one's own wireless traffic.

Note: This test has to be run many time to get a real picture of what is happening in the network.

The carrier busy test is primarily used for a single access point or a bridge environment. For sites with multiple access points, a site survey is typically performed to determine the best operating locations and operating frequencies for the access points.

Interpreting Carrier Busy Test:

  • Left side of the graph displays the result in percentage. It indicates the Percentage of time each channel is busy transmitting 802.11 packets from other Wireless Lans within the range of the device performing the test. Percentage of the busiest channel(Least preferrable) is indicated in picture.

  • Right Side of the Graph indicates the noise (Non 802.11 signals) in each channel. Channel with highest noise is indicated in dbm . If highest noise is around -90 dbm or less it is good.

Note: This Carrier Busy Test might fail while you run it on the non-root bridge. This test produces any result only when it is run from the root bridge.

Note: Devices like Spectrum analyzer best indicates the activity on certain frequency. Nonetheless Carrier busy test functions as an alternative for this.

For this option, go to Network Interfaces > Radio0-802.11a/b/g > Carrier Busy.

For more information, refer to Performing a Carrier Busy Test section of Configuring Radio Settings.

Problem Type

The signal is weak or fluctuating



Access point

Link Status Meter Test Result


No signal

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