How to read "show acsp channel-info details" outcome ?

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Hi Guys,

I'm just wondering how I should read below outcome from show acsp channel-info details:

Channel 1 Cost:21
Probability factor: -10
Channel deduction: 2 (CU: 15%, TxU: 0%, IU: 2%, CRC: 1%)
Neighbor adjustments: 31
Neighboring access points: 8
Maximum RSSI among same hive neighbors: 41
Aggregate interference 26
Interference number: 1
Penalty on channel: 41
Wide channel penalty: 41
Overlapping channel adjustments: 0
Tx power limit adjustments: 0 (Max Tx power: 20 dBm)


Channel 6 Cost:2
Probability factor: 2
Channel deduction: 28 (CU: 99%, TxU: 0%, IU: 99%, CRC: 0%)
Neighbor adjustments: 0
Neighboring access points: 0
Maximum RSSI among same hive neighbors: 0
Aggregate interference 0
Interference number: 0
Penalty on channel: 0
Wide channel penalty: 0
Overlapping channel adjustments: 0
Tx power limit adjustments: 0 (Max Tx power: 20 dBm)


Channel 11 Cost:14
Probability factor: -11
Channel deduction: 0 (CU: 1%, TxU: 0%, IU: 0%, CRC: 0%)
Neighbor adjustments: 25
Neighboring access points: 1
Maximum RSSI among same hive neighbors: 29
Aggregate interference 14
Interference number: 1
Penalty on channel: 29
Wide channel penalty: 29
Overlapping channel adjustments: 0
Tx power limit adjustments: 0 (Max Tx power: 20 dBm)




I check how many SSID are on each channel using show acsp neighbor command I can see on channel 1 five other SSID ( 3 of them are visible with around -40 RSSI). On channels 6 and 11 we got just one SSID per channel ( RSSI's are -63 for channel 11 and -82 for channel 6).

Most important statistic when you are checking those details is "Aggregate interference" and AP is choosing channel based on this statistic ? What other statistics mean ( penalty on channel ,probability factor and Channel deduction ?) Why for channel 6 channel deduction showing below statistics

(CU: 99%, TxU: 0%, IU: 99%, CRC: 0%) is this all right if some of them are reaching 99% ?



Am I reading those statistics correctly or just wrong :)

Thanks for any help how to read those details ....

Szymon
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Szymon

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Posted 2 years ago

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Gary Smith, Official Rep

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Hi Szymon,

There is a lot of information in these outputs.

Some explainations;

CU: 99%,  = This is the Channel utilization. I suspect the channel is saturated and a spectrum analysis would probably show a high duty cycle to his effect. (I suspect high levels of interference).

TxU: 0%, = I believe that this is the percentage of airtime/CU used by transmitting

IU: 99%,  = This is interference utilization. I would also look at the outputs for the overlapping channels as you would probably see high reading there too.

CRC: 0%) = percentage of airtime/CU taken by CRC errors.

I'd be interested to see a spectrum analysis output from this AP to see what it shows. As you can seen in your output, the IU is 99% of the CU%

Kind Regards,
Gary Smith
(Edited)
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Szymon

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Hi Gary,

Below is spectrum analysis screenshot. Am I reading this correctly and there is massive constant interference source on channel 6 (actually two sources ?). Spectrum analysis shows some video bridges discovered on channels  4,6,9 and 12. There is just one SSID visible on channel 6, nine on channel 1 and two on channel 11. From spectrum analysis output better channels should be channels 1 and 11 ? Am I correct ?

Apologize for lots of questions but I'm trying to get some knowledge how to read those statistics and spectrum analysis output. This AP is located in our office so I'm using it as a kind o lab :)

Thanks
Szymon



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Gary Smith, Official Rep

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Hi Szymon,

The spectrum analysis certainly confirms what the AP Logs were telling us. Based on the RF signatures we can see that the interference is non-wifi and because of the shape, likely to be a video bridge or similiar.

Channels 1 and 11 do have a lower duty cycle and I would expect these to be a better choice for the AP. In different parts of your building you might find the interefence on different channels.

Can you find out what the "video bridge" might be? Is it something you can locate in your office?

Kind Regards,
Gary Smith