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MVP
Posts: 1,110
Registered: ‎10-11-2011

2.4GHz - High average channel busy

I started running some RF reports and noticed very high average channel busy on the 2.4GHz band.   I'm seeing as high as 75% average channel busy on some APs, but it's mostly between 40% - 60% average channel busy.  Originally, I thought it was due to interference from non-wifi devices, but I've found that's not the case.  I did some spectrum analysis tests and determined the interference is coming from our own campus APs.  In my test, I disabled all APs on the floors above and below one floor that was reporting very high channel busy.  Before I turned off the APs, channel busy was around 75%.  After disabling the other APs in this building, channel busy dropped 40%.

 

APs are not on top of eachother from floor-to-floor. They're staggered.

APs are between 25 - 50ft apart.  Roughly 1 AP per 2500 sq ft.

 

Are there any configuration changes I should consider making?

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MVP
Posts: 1,405
Registered: ‎05-28-2008

Re: 2.4GHz - High average channel busy

[ Edited ]

Hi,

Please do some screenshots/or cli outputs of your ap-group profile/ssid profile/radio profile/arm profile (In order for us to understand better what might do this)

 

Some commands that might give us/you some good info:

(Aruba3200) #show ap arm history ap-name "AP NAME"

(Aruba3200) #show ap debug radio-stats ap-name "AP NAME" radio x advanced | include Busy

 

some questions:

  • What channels are u using?
  • are u using 40mhz in 2.4ghz?
  • what is the max EIRP of each AP.
  • is ARM enabled?
  • what is your AOS version | what is your AP type | ant type?

Also read the following post:

http://community.arubanetworks.com/t5/ArubaOS-and-Mobility-Controllers/channel-busy-in-Access-Point/m-p/44526

 

have a lovely weekend.

 

Me

*****************2Plus Wireless Solutions****************************
Aruba Airheads - Powered By community for empower the community
************ Don't Forget to Kudos + me,If i helped you******************
MVP
Posts: 1,110
Registered: ‎10-11-2011

Re: 2.4GHz - High average channel busy

This AP had a channel busy of 40% for the last week, but is one of the only on the floor that had channel change history:

 

Interface :wifi1
ARM History
-----------
Time of Change       Old Channel  New Channel  Old Power  New Power  Reason
--------------       -----------  -----------  ---------  ---------  ------
2013-02-17 01:08:26  1            1            12         9          P-
2013-02-17 01:02:45  1            1            9          12         P+
2013-02-17 00:55:24  11           1            9          9          I
2013-02-17 00:45:15  11           11           12         9          P-
2013-02-17 00:38:30  11           11           9          12         P+
2013-02-17 00:32:30  11           11           12         9          P-
2013-02-17 00:05:42  11           11           9          12         P+
2013-02-16 23:59:14  11           11           15         9          P-
2013-02-16 23:55:09  11           11           21         15         P-
2013-02-16 23:35:17  11           11           24         21         P-
2013-02-16 23:23:34  11           11           21         24         P+
2013-02-16 23:11:02  11           11           24         21         P-
2013-02-16 22:59:20  11           11           21         24         P+
2013-02-16 22:51:19  11           11           18         21         P+
2013-02-16 22:43:49  11           11           15         18         P+
2013-02-16 22:33:33  11           11           12         15         P+
2013-02-16 22:14:42  11           11           9          12         P+
2013-02-16 22:06:59  11           11           15         9          P-
2013-02-16 22:01:54  11           11           12         15         P+
2013-02-16 21:37:36  11           11           15         12         P-
2013-02-16 21:31:02  11           11           12         15         P+
2013-02-16 21:12:43  11           11           15         12         P-
2013-02-16 20:49:31  11           11           12         15         P+
2013-02-16 20:42:52  11           11           9          12         P+
2013-02-16 20:38:20  11           11           15         9          P-
2013-02-16 20:32:45  11           11           18         15         P-
2013-02-16 20:20:54  11           11           15         18         P+
2013-02-16 20:13:14  11           11           21         15         P-
2013-02-16 20:00:59  11           11           18         21         P+
2013-02-16 19:55:14  11           11           21         18         P-
2013-02-16 19:51:10  11           11           18         21         P+
2013-02-16 19:44:02  11           11           15         18         P+

&

Channel Busy 1s                  54
Channel Busy 4s                  57
Channel Busy 64s                 55
Ch Busy perct @ beacon intvl     62 53 51 55 34 61 53 52 64 60 60 62 61 64 34 64 63 61 65 57 65 63 64 37 62 63 61 59 59 67


What channels are u using?
1,6,11

Are u using 40mhz in 2.4ghz?
No.

What is the max EIRP of each AP.
9 min
127 max

Is ARM enabled?
Yes.

What is your AOS version | what is your AP type | ant type?
6.1.3.4
AP105
Internal

=======================================
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MVP
Posts: 1,405
Registered: ‎05-28-2008

Re: 2.4GHz - High average channel busy

try to low your max eirp level to 15.. (from 127)

tell me if there is any improvement.

(give it at least 5-7 min to run with the new EIRP values while the ARM is enabled)

and print out the same output commands.

 

*****************2Plus Wireless Solutions****************************
Aruba Airheads - Powered By community for empower the community
************ Don't Forget to Kudos + me,If i helped you******************
MVP
Posts: 2,958
Registered: ‎10-25-2011

Re: 2.4GHz - High average channel busy

[ Edited ]

1- If your client support it turn on 802.11d/802.11h It will make clients and APS negociate power level which reduce interference...

It is recommended to turn it on if your clients support it...  you can turn it on, on rf managment, under 802.11g radio  for 2.4ghz and 802.11a for 5ghz.

2-Turn on Band steering if you dont have it(if you got dual band APS) that will move the capable 5ghz Clients to 5ghz channel which will free more the 2.4ghz channel.   You have to turn it on, on each vap(virtual AP)

 

Note: Optionally, You can try turning mode aware ARM in ARM profile it will dynamically change radios into AM mode if it determines that there is already suffiecent coverage...

----------------------------------------------------
Product Manager - Aruba Networks
Alternetworks Corp
MVP
Posts: 1,405
Registered: ‎05-28-2008

Re: 2.4GHz - High average channel busy

[ Edited ]

Good advise from NightShade1  :smileyhappy:

  • Just be Aware! - that mode aware will disable AP units as ACCESSPOINTS and will make some units as AIRMONITORS automatically

(it will do it only If the coverage of current deployment is good enough with less AP on the same area)

*****************2Plus Wireless Solutions****************************
Aruba Airheads - Powered By community for empower the community
************ Don't Forget to Kudos + me,If i helped you******************
MVP
Posts: 1,110
Registered: ‎10-11-2011

Re: 2.4GHz - High average channel busy

[ Edited ]

kdisc98 wrote:

try to low your max eirp level to 15.. (from 127)

tell me if there is any improvement.

(give it at least 5-7 min to run with the new EIRP values while the ARM is enabled)

and print out the same output commands.

 


AP1 - Before & After

Channel Busy 1s                  39
Channel Busy 4s                  36
Channel Busy 64s                 32
Ch Busy perct @ beacon intvl     37 34 39 36 37 41 42 46 45 6 44 40 43 42 41 38 37 6 38 36 37 38 42 39 46 43 43 16 39 36

Channel Busy 1s                  36
Channel Busy 4s                  38
Channel Busy 64s                 37
Ch Busy perct @ beacon intvl     34 32 32 31 71 33 34 30 34 35 36 42 45 35 39 34 34 33 34 36 32 32 35 84 31 34 36 36 32 33

AP2 - Before & After

Channel Busy 1s                  88
Channel Busy 4s                  82
Channel Busy 64s                 82
Ch Busy perct @ beacon intvl     83 88 86 87 87 88 97 88 87 86 85 88 87 94 88 88 86 90 87 91 85 84 83 86 86 89 90 88 87 77

Channel Busy 1s                  86
Channel Busy 4s                  75
Channel Busy 64s                 79
Ch Busy perct @ beacon intvl     85 86 83 94 90 86 85 84 89 82 82 61 78 76 70 75 73 73 72 73 70 88 72 68 66 70 72 76 71 69

 

I'm a little wary about turning on 802.11d/h without doing some more research.  The GUI mouse-over text isn't descriptive enough.

 

I've thought about enabling mode aware, but I am also a little skiddish about this feature.

=======================================
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MVP
Posts: 2,958
Registered: ‎10-25-2011

Re: 2.4GHz - High average channel busy

[ Edited ]

Do you have Band steering on?

you can turn that without any fear.....if you dont have please turn it on now.

 

If you turn on 802.11d/802.11h if client does not support it, it might have problems connecting.... i dont think you will have issue if your laptops tablets are not that old.... and well if they dont have super old drivers...

I have enable it succesfully on some clients... but i also tell clients that if they  find some device that cannot connect update the driver.  

 

About the mode arm aware it will just turn APs in this case the band of that ap in air monitor...  if he see he has too much coverage...

 

What are your concers about these features?

 

----------------------------------------------------
Product Manager - Aruba Networks
Alternetworks Corp
MVP
Posts: 1,110
Registered: ‎10-11-2011

Re: 2.4GHz - High average channel busy

Yes, we have band steering enables. 5GHz is preferred.

I get nervous about enabling a feature that could keep devices from connecting, like 802.11d/h. I would say to some extent I don't trust that mode aware will be smart enough to work as advertised. I may have to enable it over a weekend and see what happens.

Our oldest laptops should only be 3 years old. The majority of our laptops are imaged with an old driver. I believes it's a few years old. I'd like to make a push to update drivers but that's another group's responsibility. I can only suggest it.
=======================================
If a reply adequately addresses your issue, please click on the "Accept as Solution" and "Give Kudos" button so this information can benefit other users.
MVP
Posts: 1,110
Registered: ‎10-11-2011

Re: 2.4GHz - High average channel busy

Let me add that at the times that I performed my tests, there weren't many devices on wifi. Most APs were operating at around 9 eirp. So I'm not sure how much .11d/h would help.

I do have have about 4-5 SSIDs on all the APs. I wonder if that creates problems.
=======================================
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