Wireless Access

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Contributor I
Posts: 67
Registered: ‎10-17-2012

Low SNR, High Channel Busy % and High interference

I am observing high channel busy % along with high interference. Also a lot of clients have low SNR. Is there any way through which I can find out reasons for the same and take necessary corrective action. Are there any freeware tools ?

MVP
Posts: 2,989
Registered: ‎10-25-2011

Re: Low SNR, High Channel Busy % and High interference

If you wanna know the source and you have RF protect license you can convert some APS in spectrum analyzer and find out the cause of the interference.  It will tell you if its microwave if its another 802.11 or if its bluetooth and so on... And will tell you many good things...

 

Do you have that licence?

 

Here is a link that can be helpful for you with the spectrum analyzer

http://www.arubanetworks.com/wp-content/uploads/RFSpectrumWLANsAppNote_20120514.pdf

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Product Manager - Aruba Networks
Alternetworks Corp
MVP
Posts: 2,989
Registered: ‎10-25-2011

Re: Low SNR, High Channel Busy % and High interference

[ Edited ]

If you dont have the license you can get basic info.

 

Can you run

show ap active ip-addr <ap ip address>

 

Check to make sure: • Channel Frame Retry Rate % is below 30%. If higher then too much interference. • Channel Noise Floor is above 80. If Noise Floor is lower then too much non-802.11 interference

 

Check this on 2.4ghz and also on the 5ghz if you got dual band to see

 

Also i notice that yhou have like too many clients on 2.4ghz channel

 

Could you please check if you got band steering on on the SSIDS?

This will make the capable clients of 5ghz going to 5ghz channel instead of going to 2.4ghz channel...

Remenber you got 23 usable channel on 5ghz and just 3 usable non overlapping channels on 2.4ghz.  So clients are a way more happy being on 5ghz rather than 2.ghz... what got better 2.4ghz is that it travel a bit farther than 5ghz...

 

Not related to the interference but be sure you got Airtime fairness on...

 

First check this things we can help you to tune your network...

 

The thing is that some people just deliver the wireless network without thinking how to deploy it correctly.  Soemtimes they just see coverage when they need to see also the High density enviroment... for example i saw that in a School that before we arrived bough another brand(will not name it but its a known brand) and they just calculate it for coverage... and its a school its a high density enviroment.....

I have deployed wireless on school and you can see like 70 or 80 kids in one AP if you dont plan this correctly. 

It also depend in what you are using it will be just for internet browsing? will you use Wireless phones? will you run Intensive intranet apps? soo many things you should take in mind before deploying it.   I have seen bad implementations  that makes the brands look bad even fi they are not bad... including Arubas deployments... and its sad because aruba is like the best brand :)

 

Cheers

Carlos

 

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Product Manager - Aruba Networks
Alternetworks Corp
Contributor I
Posts: 67
Registered: ‎10-17-2012

Re: Low SNR, High Channel Busy % and High interference

show ap active command gives me Frame retry rate to be 0.Channel noise shown 99.While on the dashboard i see channel busy % between 80-90 and interference between 30-40.

 

Band steering has not been enabled.

 

Attaching snapshot of system profile. I want clients to use 5 GHz band as against 2.4 GHz for benefits as pointed out. Also HT mode has been enabled in 2.4 GHz band. Is it ok to have it ? I have checked with my implementation partner, he says it is fine. but, i am not quite sure of it. How do i detect the source of interference ?

MVP
Posts: 2,989
Registered: ‎10-25-2011

Re: Low SNR, High Channel Busy % and High interference

Does it show you that info for both bands? for 2.4ghz band and 5ghz band? i mean 0 of % of retries and noise over 90?

 

Okay to use band steering go to

ap configuration

ap group select here your ap group

go to wireless lan

go to virtual ap

go to the ap group you want to active the band steering

go to ssid and there you wil find a checkbox of band steering and you should activate it.

 

The airtime fairness is on QOS just create a new profile and put fair access on it and thats it click okay

 

Yes ht on 2.4ghz is okay... just be sure you are using 40hz channels on just A band...

 

 

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Product Manager - Aruba Networks
Alternetworks Corp
Contributor I
Posts: 67
Registered: ‎10-17-2012

Re: Low SNR, High Channel Busy % and High interference

I see majority of my AP's in 2.4 Ghz band only. Very few of my AP's are in 5 Ghz band, roughly 10 out of 100. And they belong to one particular group. Which setting is causing my majority of AP's to be in 2.4Ghz band ?

 

Above said info is seen in 2.4 Ghz band only.

 

My implementation partner is using HT 40 in 2.4 Ghz band, which I  think should not be the case. I raised this up with him but received an unsatisfactory answer.

MVP
Posts: 2,989
Registered: ‎10-25-2011

Re: Low SNR, High Channel Busy % and High interference

20mhz should not be be used... becasue it will overlap channels.  Are you sure you have it on? you can check it really easy  you will see channels  with a plus or minus next to it.

Also you can check it on

ap group

rf managment

802.11g

ARM

and check Allowed bands for 40MHz channels it should be on  a -only

 

 

What model of AP youuu got?

 

 

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Product Manager - Aruba Networks
Alternetworks Corp
Guru Elite
Posts: 20,993
Registered: ‎03-29-2007

Re: Low SNR, High Channel Busy % and High interference


mahesh_shirke wrote:

I am observing high channel busy % along with high interference. Also a lot of clients have low SNR. Is there any way through which I can find out reasons for the same and take necessary corrective action. Are there any freeware tools ?


High Channel Busy either means too much coverage or too much interference or both.  Unless you can (1) remove the source of interference (2) Decrease coverage by removing access points in the Area, your options might be limited...

 



Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

MVP
Posts: 2,989
Registered: ‎10-25-2011

Re: Low SNR, High Channel Busy % and High interference

Guess no need to remove it but you can convert it as AM...

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Product Manager - Aruba Networks
Alternetworks Corp
Guru Elite
Posts: 20,993
Registered: ‎03-29-2007

Re: Low SNR, High Channel Busy % and High interference

I think Nightshade is saying 40 MHz should not be used..


Colin Joseph
Aruba Customer Engineering

Looking for an Answer? Search the Community Knowledge Base Here: Community Knowledge Base

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