Wireless Access

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Occasional Contributor II

Re: Signal fluctuation too high and too frequently

Hi Jerrod Howard,

 

For your information, my customer is purchasing small auto robotics device that assisting them to carry the boxes around. This robotics device is a self design by a AGV company based on the customer requirement. This robotics device is using a usb wireless adapters with external antenna to receive the wireless signal for the robotics device. 

 

 

Highlighted
Guru Elite

Re: Signal fluctuation too high and too frequently


@niv lee wrote:

Hi Jerrod, 

 

I had done a site survey using airmagnet. Attachment is the document for the site survey using airmagnet.

 

The signal for the coverage is ok, however, customer still not satisfied on it. Customer need a gurantee from Aruba that how to prevent the signal fluctuation would not be too many and provide a recommanded signal fluctuation range to allow their robotics device function. 

 

Please correct me if i'm wrong. For my understand, signal will fluctuation more when the AP discover nearby have many same channel or too many interference, AP will change the channel or re-adjust power transmit.


The signal from the device itself will not fluctuate; when there is co-channel interference or reflections, the signal will seem to fluctuate.  Questions:

 

How high do you have these access points mounted?

How far apart are the access points mounted?

What is the output of "show ap radio-summary"?

 


*Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.*
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Highlighted
MVP Expert

Re: Signal fluctuation too high and too frequently

Thanks, that helps alot. Colin has you on the right track. APs don't have to change power or channels to find slight variations in power output, as that is due to reflections and nulls in the RF due to reflectivity.

 

You can disable ARM and do a static channel plan, or you can set the min and max ARM power to the same and just let it change channels if/when needed. But to know what is best, the info Colin is looking for will be the starting point. 


Jerrod Howard
Distinguished Technologist, TME
Highlighted
Occasional Contributor II

Re: Signal fluctuation too high and too frequently

Thanks alot. I will suggest the configuraton to my customer for a testing. 

 

Just to confirm, there is no any gurantee that the signal fluctuation will be stable on a value and not keep change?

 

Based on your experience, what is the signal fluctuation range consider normally behavior from wireless? +-15dbm or +-20dbm? 

Highlighted
Guru Elite

Re: Signal fluctuation too high and too frequently

The fluctuation has little to do with the equipment.  It has everything to do with the environment it is being measured in.  Most likey you need to reduce the power on your access points, because you have too much coverage.  Co-channel interference and collisions are probably the culprit here.  The Airmagnet survey gives clues about coverage, but it does not say specifically what coverage is being provided by what access points, so it does not get to the root of your problem.

 

Here is what I would do:

 

The ARM profile by default has a minimum of 18 and a maximum of 127.  That is much too high for a warehouse environment where everything is open.  RF can propagate hundreds of meters in open space and that can cause exactly what you are observing.  I would make the minimum 12 and a maximum of 15, and then take more measurements to see if the "fluctuation" continues.

 

Access points with  ARM do not change channel or power any sooner than 8 minutes, so if there are any fluctuations in power, that is not ARM; that is the environment.  Depending on the access point, it can only output power of up to 21 dbm, so a swing of 15 to 20 dbm could not be the hardware, unless the access point is being turned on and off.

 

If you could overlay where the access points are mounted in the diagram and how high, that would be a good start for us to figure this out...


*Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.*
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View solution in original post

Highlighted
Occasional Contributor II

Re: Signal fluctuation too high and too frequently

Hi,

 

The high is around 3 meter high. 

Below is the AP's location that deployed. Each red small square represent the pillar. Each pillar distance is around 5 to 6 meter. In this floor location, there is alot of machines that running on testing micro chipset. 

floor2.JPG

Highlighted
Guru Elite

Re: Signal fluctuation too high and too frequently

That placement is good.  Do you have the Airmagnet Survey of just a single access point?  Can you filter it to just one?


*Answers and views expressed by me on this forum are my own and not necessarily the position of Aruba Networks or Hewlett Packard Enterprise.*
ArubaOS 8.5 User Guide
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