How to check wireless AP resource utilization

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How to check wireless AP resource utilization

To view the current channel utilization of the AP

[H3C]probe

[H3C-probe] display ar5 1/2 channelbusy

For example:

[H3C-probe]display ar5 2 channelbusy

ChannelBusy information

 Ctl Channel: 06 Channel Band: 20M

 Ext Channel:

 Record Interval(s): 9

 Date/Month/Year: 13/04/2017

Time(h/m/s): CtlBusy(%) TxBusy(%) RxBusy(%) ExtBusy(%)

 01 07:20:59 80 6 26 0

 02 07:20:50 87 6 25 0

 03 07:20:41 84 6 22 0

 04 07:20:32 83 6 23 0

 05 07:20:23 89 6 29 0

 06 07:20:14 80 6 29 0

 07 07:20:05 83 7 21 0

 08 07:19:56 86 9 20 0

 09 07:19:47 85 6 23 0

 10 07:19:38 80 6 24 0

 11 07:19:29 82 4 22 0

 12 07:19:20 80 5 22 0

 13 07:19:11 82 0 24 0

 14 07:19:02 85 4 20 0

 15 07:18:53 83 4 22 0

(1) RxBusy>>TxBusy, RxBusy+TxBusy sums to 80 or more.

For example, RxBusy is 80 on average and TxBusy is less than 5. This situation is typical of internal WLAN interference, i.e. APs on the same frequency are visible to each other and compete for a channel medium, resulting in abnormally high RX utilization of airports. Solutions include reasonable channel planning, power planning, turning off RRM low rate, turning off broadcast Probe answering and increasing Beacon frame spacing, layer 2 isolation, etc.

(2) RxBusy and TxBusy are similar, with the sum of RxBusy+TxBusy reaching 80 or more.

For example, the average RxBusy is 50 and the average TxBusy is about 40. If there are still terminals with slow Internet access, the most likely reason is that there are too many wireless CPEs, or some of them have a large service volume and take up too much bandwidth. It is recommended to open the terminal speed limit or expand the capacity to increase the AP to solve the problem.

(3) The sum of RxBusy<<TxBusy, RxBusy+TxBusy reaches 80 or more.

For example, the average TxBusy is 80 and RxBusy is less than 5. This situation indicates that the AP is blocked from sending packets in the downstream direction. It is more common in outdoor applications. When this type of failure occurs, it is usually accompanied by a low TX negotiation rate in the client verbose message, i.e. the frames sent by the AP to the STA are often lost and then slowed down and retransmitted, resulting in the AP sending frames at low speeds. The low speed frames consume a lot of null resources, which in turn leads to a collective poor STA experience.

If you encounter this situation, you can first observe the signal strength of the STA under the AP.

(4) Another scenario that leads to poor air port experience is the presence of non-WLAN interference, but the evidence of the presence of non-WLAN interference is not obvious. In terms of air port utilisation, when CtlBusy greatly exceeds the sum of RxBusy and TxBusy, it can be considered as an evidence of the presence of non-WLAN interference. Common sources of non-WLAN interference include, for example, wireless cameras and 3G/4G base stations that are too close together (outdoor APs are required to maintain a distance of at least 5 metres from the 3/4G base station antenna).

When non-WLAN interference is suspected, it can be proven by using the exclusion method. That is, first exclude the surrounding WLAN interference sources, e.g. turn off the surrounding APs and use omnipeek to capture packets and find that WiFi packets cannot be captured. If an unusually high CtlBusy is still present in such cases, this can be used as evidence of the presence of external interference.