How to detect interference on WLAN networks

You can use Wirelessmon, NetStumbler, or InSSIDer (downloaded for free on the Internet) to check whether there is strong co-channel or adjacent-channel interference near the AP. In general, the interference signal strength should be lower than �?0 dBm. If multiple co-channel or adjacent-channel interference signals exist and the strength is strong, perform network optimization to prevent channel conflicts.

If interference sources cannot be determined using a scanning tool,

- Check whether wireless devices such as Bluetooth devices, infrared devices, and microwave ovens exist, because non-WLAN devices may cause severe interference to WLAN networks.

- Use the interference detection function to further determine the interference source.

Radio channels are often affected by the radio environment, and the service quality is therefore degraded. Interference detection allows APs to send alarms to an AC when co-channel, adjacent-channel, or STA interference exceeds the alarm threshold.

Interference detection can detect AP co-channel interference, AP adjacent-channel interference, and STA interference.

AP co-channel interference: Two APs working at the same frequency band interfere with each other. For example, on a large-scale WLAN (a university campus network), different APs often use work in the same channel. When coverage areas of the APs overlap, co-channel interference exists, degrading network performance.

AP adjacent-channel interference: Two APs with different center frequencies have overlapping areas, resulting in adjacent-channel interference. Therefore, if APs are placed too close to each other or they have strong signals, bigger noise will be produced, degrading network performance.

STA interference: If there are many STAs that are managed by other APs around an AP, services of the STAs managed by the local AP may be affected.

The following are alarms for co-channel interference and STA interference.

V200R005C10:

WLAN/4/AP_COMMON_FREQUENCY_DISTURB: OID [oid] The co-channel interference exceeds the alarm threshold. (APID=[INTEGER], APID=[INTEGER], RadioID=[INTEGER], APMAC=[OPAQUE], APChannel=[INTEGER], BssId=[OPAQUE], RSSI threshold percent=[INTEGER])//AP_COMMON_FREQUENCY_DISTURB indicates that co-channel interference exists.

WLAN/4/STATION_DISTURB: OID [oid] Jam of station is detected notify.(APID=[INTEGER], APID=[INTEGER], RadioID=[INTEGER], APMAC=[OPAQUE], APChannel=[INTEGER], StatMACList=[STRING])//STATION_DISTURB indicates that STA interference exists.

V200R006:

WLAN/4/AP_COMMON_FREQUENCY_DISTURB: OID [oid] The co-channel interference exceeds the alarm threshold.(APMAC=[OPAQUE], RadioID=[INTEGER], ApName=[OCTET], APChannel=[INTEGER], BssId=[OPAQUE], RSSI threshold percent=[INTEGER]%, APID=[INTEGER])//AP_COMMON_FREQUENCY_DISTURB indicates that co-channel interference exists.

WLAN/4/STATION_DISTURB: OID [oid] Jam of station is detected notify.(APMAC=[OPAQUE], RadioID=[INTEGER], ApName=[OCTET], APChannel=[INTEGER], StatMACList=[STRING], APID=[INTEGER])//STATION_DISTURB indicates that STA interference exists.

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