Transmission Power and roaming

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  • Updated 4 months ago
Hello

I
would like a help, I have in an office of the same floor mounted 3 aps, however when performing tests going from one place to another my pc stays stuck to the other ap, in this case I was seeing the possibility of adjusting the power manually but I would like to listen your recommendations before applying the change.

the disposition of the aps is on the image

Thank you
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Danilo Arias

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Posted 5 months ago

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Dianne Dunlap

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Roaming behavior in any device is a function of the device drivers - the power, channels, signal-to-noise it sees, the number of neighboring client devices and many other factors.  Unless APs are on incorrectly configured channels and/or power set too high or too low, tweaking AP power to accommodate a single device is not a good idea.  You should first look at upgrading the device drivers.
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BJ, Champ

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Rather than manually setting the power, try configuring a radio profile with a reduced max power, particularly on the 2.4 radio. This will still allow ACSP to do its job.

On another note, is there any particular reason you put three APs in what appears to be such a close proximity?
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Hans

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few more tips:
- disable slow basic data rates as 1-2-5.5 and 11Mb if there are no 802.11b devices
- load balancing can create sticky roaming, however if the environment is high density and mobility (roaming) using load balancing can be the better chose

As already mentioned, there are a lot of things that can be the cause of this, every driver does his thing on a different way, as Dianne said, first update the driver. A validation survey or packet capturing is the next step if the problem still exists and you want to know the cause of it.
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Crowdie, Champ

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Get an Android tablet or smartphone and download the Aruba Utilities application.  Turn the Android tablet or smartphone off and stand by the right most access point (as shown on your plan).  Turn the Android tablet or smartphone on and wait for it to authenticate to a SSID on the right most access point.  Once it has authenticated run the Aruba Utilities application.

You should now see the signal strength of the SSID you are authenticated to.  Click on the "SHOW WI-FI EVENTS" button at the bottom of the screen.  You will now see what the wireless card in the Android smartphone or tablet is reporting.  If you just stand there you will see "RSSI_CHANGED" updates as the detected signal strength goes through slight changes.  Don't worry this is normal.

Work towards the second access point and look for the BSSI to change.  This is when the Android smartphone or tablet has roamed from the right most access point to the central access point.  I suspect that the roam will not occur.

Repeat this same walk from the right most access point to the left most access point.  Again I suspect the roam will not occur or will occur well after you arrive at the left most access point.

You can use this application to tell you where the roam occurs and adjust the transmit power settings on your three access points so the roaming process occurs quickly and where you want it.

If you need to have a dense access point deployment, and this is not uncommon, then having all your transmit powers on auto (i.e. letting ACSP set your channels and transmit powers) will not work.   I have a number of dense deployments where the traffic is 5 GHz only and the transmit powers are around 3 to 5 dBm.
(Edited)
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Danilo Arias

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Hello

Thank you all for your answers, but unfortunately, despite making changes in powers, I have observed a behavior that is too anomalous.

Turn off and leave only one ap, I connect and the connectivity tests showed enough intermittences, keep in mind that the tests were done next to the ap and the intermittences went to the gateway, the ports in the switch were verified and discarded wiring watching the same behavior.

Another anomalous behavior was that it did not allow connecting new users (in the profile I see that there is a maximum of 100 users), the tests were done with 3 android and 2 laptops (although old users who came using the wireless showed stability in tests of ping and signal)

From hive manager I tried to upload again the complete configuration to the aps but it showed me an error message after 29%, the last thing I did and that I solved the issue of the complete configuration was to allow all the ports (in the firewall they have rules specific to allow ports 80/443/12222 / 53 tcp and udp) do not know if any additional port is required?

On the other hand I tried to connect via ssh with the credentials admin / aerohive but it was not possible, in the case that in the initial configuration in the hvNg no password had been configured, they are still the default ones?

When I had the 3 aps connected I noticed alarms indicating alert raised this what is it about?

Another thing that caused me curiosity is if these 3 aps should be on the same channel for roaming and note that they were installed on channels 1, 6, 11 should not automatically see that they are neighbors of the same manufacturer and work on the same channel . ?


Finally in order to solve the issue install some ubiquiti that worked properly.

Could you please give me ideas
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Crowdie, Champ

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Whether you use manual or ACSP power levels really depends on the density of the access point deployment.  The denser the access point deployment the less likely you are to use ACSP power levels.

If you think of the access points in the floor plan above and number them AP#1, AP#2 and AP#3 (moving from left to right) then you want a client connected to AP#1 to roam to AP#2 before they physically reach AP#2.  With any automatic power setting the AP is going to boot and then "push out" to find another radio on the same channel.  With only three access points (and no neighbours just to make this easier) the 2.4 GHz radio in AP#1 is going to "look" for neighbouring radios and find two - AP#2 and AP#3.  If AP#2 is on channel 6 and AP#3 is on channel 11 then AP#1 will be assigned channel 1 and, since there are no neighbouring access points on channel 1, will be assigned the maximum transmit power allowed by the radio profile and local regulations.  That transmit power may be so high that signal can be detected right underneath AP#3 and client roaming will be extremely poor. 

So, if you are going to use ACSP transmit power assignment, and there is nothing wrong with that, be extremely careful with the radio profile's maximum transmit power assignment.  It is likely that you will need to make multiple radio profiles as the maximum and minimum transmit powers may be different in different areas of the deployment.
(Edited)
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Danilo Arias

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Hi, in this case, how do you recommend carrying out the coverage tests to adjust the powers? leaving only one AP on and seeing its coverage and so one at a time? or with an insider seeing the power of each ap identifying it by mac?

Thank you
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Crowdie, Champ

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You need a minimum of two access points to complete roaming testing.  You could use the Client Monitor tool in HiveManager but I find it better as a diagnostic tool as you need to know really quickly when the client roams and there is a delay with Client Monitor.

For a non-high density access point deployment I normally start by setting the 2.4 GHz radios (if any) to 14 dBm and the 5 GHz radios to 17 dBm.  Use the previously mentioned Aruba Utilities Android application to look for the BSSI changes.  This indicates the roam has occurred.

Walk from AP#1 to AP#2.  If the roam occurs too close to AP#2 reduce the transmit power on AP#1. Repeat until you can walk from AP#1 to AP#2 with the roaming occurring quickly and where you want it to.

Now you repeat this process but walking from AP#2 to AP#1.  This is the part of the process people forget about and this can cause users to report connectivity issues as the roaming from AP#1 to AP#2 works but the roaming from AP#2 to AP#1 is poor.
Next repeat this using AP#2 and AP#3 but remember that if you make significant changes to the AP#2 transmit power you may affect the AP#2 to AP#1 roaming.

Finally, walk from AP#1 to AP#2 to AP#3 and back.  The roaming should all occur nicely.
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Danilo Arias

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Hello, thanks but I wanted to make a query the ideal thing is that the roaming is generated when it is approximately in that range, in the range contention range -67 to -85 dBm).

Thank you
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Crowdie, Champ

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When the client roams is up to the client's wireless driver so one client may roam at -75 dBm while another may roam at -72 dBm. 

A client is unlikely to roam at -67 dBm (as the signal strength is too high) and shouldn't roam when the RSSI is -83 dBm or less (the signal is too low).
(Edited)