Lowering the power level to reduce RF interference

Relevant Product(s): FortiAP

Reducing power reduces unwanted coverage and potential interference to other WLANs. Areas of unwanted coverage are a potential security risk. If possible, reduce the transmitter power of your wireless access point so that the signal is not available beyond the areas where it is needed. Auto Tx Power Control can be enabled to automatically adjust the transmit power.

In cases where customers complain about slow wireless traffic through a FortiAP, it might be necessary to try to reduce the possibility of RF interference. It is best practice not to locate FortiAPs near steel beams or other interfering materials. You can try using a wireless sniffer tool to collect the wireless packets and then analyze the extent of air interference.

A common mistake is spacing FortiAPs based upon the 5Ghz radio frequency. The 2.4Ghz signal travels further.

You have two options when confronted with slow wireless traffic through a FortiAP:

Option #1: Reducing transmit power

Perform a speed test and record the results. Set one of the radios on a FortiAP to be in dedicated monitoring mode. Then observe how many APs are detected. If the number of APs is too high (i.e., greater than 20), try reducing the transmit power in the WTP profile for the FortiAPs until the number of dedicated APs has dropped significantly.

Repeat the speed test.

Option #2: Ensuring that VAPs are distributed over the available channels

No built-in tools are available to measure RF interference directly. However, FortiOS 5.0 does allow for automatic power adjustment, which should minimize the occurrence of RF interference.