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Access network design for branch, remote, outdoor and campus locations with Aruba access points, and mobility controllers.
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Avoid interference on same channel

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  • 1.  Avoid interference on same channel

    Posted Dec 02, 2013 08:07 AM

    Hello to all.

    We have a highly dense network with multiple access points near and including the signal leakage between floors ends up affecting our use of channel time that is an AP with a high TX directly affects the others that are on the same channel, the next time or not. The fact is that even decreasing the power of the ARM have the co-channel interference, as can be seen in the attached figure. My question is: Is it possible to use the RX Sensitivity Tuning Based Channel Reuse to try to mitigate this interference? Sometimes we have 90% occupancy of the channel in one area so the RX received.
    We have enabled the ARM with the Client Aware enabled and no longer used the HT-40 just to avoid the aggregation of channels. We have 14 controllers 3400 and 500 AP's model AP125 connected, is our version of ArubaOS 6.2.1.3
    thank you


    #3400


  • 2.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 08:32 AM

     

    One thing I noticed is that all those APs have the same channel, are those neighbor APs ?

     

    What's the density of your deployment ? if it is too dense then you should decrease the minimum to 9 and max to 15  ,you should test   this first to make sure that you don't leave any holes .



  • 3.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 08:35 AM

    Exactly, they are neighbors and are on the same channel ARM is who is managing, but as the client is aware active, they do not change the channel, sometimes we have 3 ap's online and on the same channel :smileyfrustrated:



  • 4.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 08:45 AM

     

    Can you please run this command to check if you have the other channels available under the regulatory domain attached to the AP-Group those APs belong to?

     

    (controller) #show  ap regulatory-domain-profile <profile name> 

    Regulatory Domain profile "default"
    -----------------------------------
    Parameter Value
    --------- -----
    Country Code US
    Valid 802.11g channel 1
    Valid 802.11g channel 6
    Valid 802.11g channel 11

     

    Can you pleas share your ARM config ?



  • 5.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 08:51 AM

    Country Code BR
    Valid 802.11g channel 1
    Valid 802.11g channel 6
    Valid 802.11g channel 11

     

     

    -------------------------------------------------------

    Adaptive Radio Management (ARM) profile "RF_PROFILE_G_A4"
    ---------------------------------------------------------
    Parameter Value
    --------- -----
    Assignment single-band
    Allowed bands for 40MHz channels None
    Client Aware Enabled
    Max Tx EIRP 127 dBm
    Min Tx EIRP 15 dBm
    Rogue AP Aware Disabled
    Scan Interval 10 sec
    Aggressive scanning true
    Active Scan Disabled
    ARM Over the Air Updates Enabled
    Scanning Enabled
    Multi Band Scan Enabled
    VoIP Aware Scan Enabled
    Power Save Aware Scan Disabled
    Video Aware Scan Enabled
    Ideal Coverage Index 10
    Acceptable Coverage Index 4
    Free Channel Index 25
    Backoff Time 240 sec
    Error Rate Threshold 50 %
    Error Rate Wait Time 30 sec
    Noise Threshold 75 -dBm
    Noise Wait Time 120 sec
    Minimum Scan Time 8
    Load aware Scan Threshold 1250000 Bps
    Mode Aware Arm Disabled
    Scan Mode all-reg-domain

     

    ----------------------------------------

    Profile 802.11g

     

    Parameter Value
    --------- -----
    Radio enable Enabled
    Mode ap-mode
    High throughput enable (radio) Enabled
    Channel N/A
    Transmit EIRP 15 dBm
    Non-Wi-Fi Interference Immunity 2
    Enable CSA Disabled
    CSA Count 4
    Spectrum Monitoring Disabled
    Spectrum Monitoring Profile default-g
    Advertise 802.11d and 802.11h Capabilities Disabled
    Spectrum Load Balancing Enabled
    Spectrum Load Balancing Mode channel
    Spectrum Load Balancing Update Interval (sec) 30 seconds
    Spectrum Load Balancing Threshold (%) 20 percent
    Spectrum Load Balancing Domain N/A
    Beacon Period 100 msec
    Beacon Regulate Disabled
    Advertized regulatory max EIRP 0
    ARM/WIDS Override OFF
    Reduce Cell Size (Rx Sensitivity) 0 dB
    Management Frame Throttle interval 1 sec
    Management Frame Throttle Limit 20
    Maximum Distance 0 meters
    RX Sensitivity Threshold 0 dB
    RX Sensitivity Tuning Based Channel Reuse disable
    Protection for 802.11b Clients Enabled
    Adaptive Radio Management (ARM) Profile RF_PROFILE_G_A4
    High-throughput Radio Profile default-g
    AM Scanning Profile default

     

    thx Victor



  • 6.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 08:41 AM

    Hi Victor

    Once tested with the EIRP power 9dBm and the result was not very encouraging, several customers complained of lack of signal in your area. We have a very complicated environment before trying to reposition access points I want to exhaust all possible configurations.



  • 7.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 08:52 AM

    Please make sure we enable BCMC on all VAP`s to reduce the air congestion especially on 2.4 GHz.

    May I know the type of clients connected to the network ? Disable the multi-band scanning and band-steering if the clients are swithcing between "a" and "g". 

     

    From the Screen shot I see one of the AP shows up "56%" of Channel busy and other AP`s are less than 30 %.

    Enable AMON on the controller pointing to airwave to capture the live report of RF utilization, client report and it`s history.

    Find below link.

     

    http://community.arubanetworks.com/t5/Community-Tribal-Knowledge-Base/Why-you-should-always-enable-AMON-on-your-Aruba-Controller-when/ta-p/72104

     

    Also please attach show ap debug radio-stats and show ap arm rf-summary to look at mac errors etc...

    Is the clients are dropping when they roam or being stationary or are we facing ping loss on 2.4.GHz.

     

    It would be great if you can provide little bit of more info.

     

    Thx.

     



  • 8.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 09:58 AM

    Sriram,

     

    We have no problems in clients alternating between radio A or G, the same concern is only the interference between channels. The issue of AMON is active in the Airwave only thing he does not plot is the question of interfering Detected device, despite having access points working as a spectrum analyzer of our access points do not support all available options. We AP125 access point model.

     

    Thx



  • 9.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 10:01 AM

     

     

    The only thing I can't understand is why ARM is assigning the same channel to all those APs ?

     

     

     

     



  • 10.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 10:07 AM

    @victorfabian wrote:

     

     

    The only thing I can't understand is why ARM is assigning the same channel to all those APs ?

     

     

     

     




     

    If Client-Aware is on (it is by default) and clients are always passing traffic, access points would never change channel



  • 11.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 10:15 AM


     

    If Client-Aware is on (it is by default) and clients are always passing traffic, access points would never change channel


     

    cjoseph that's valid point.

     

    Rafael,

     

    What type of clients are you using ? 

    Is this a hospital or a university dorm ?



  • 12.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 10:45 AM

    Victor

     

    99% of our clients are mobile, iPhone, Android ... Here are Brazil's parliament, chamber of deputies



  • 13.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 10:55 AM

    Thanks for the reply. As Colin said, disabling 40 MHz  is a good move. We may need to disable Client-aware temporarily as well for the AP`s to move to better channel. I wouldn`t recommend to enable "local-probe-threshold" as there could be a chances of AP`s pushing the client from one AP to another AP veru frequently since this is dense deployment.

     

    We could set the AP power level to 9 - 12 for GHz band and optimize the basic rate and transmit rates say like "12 & 24" as basic rates and transmit rates covering all the way from "12 - 54".

     

     

    Thx.



  • 14.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 11:02 AM

    I disabled the HT 40 there is a week ago, since then the scenario has improved but not that much. I have a question regarding EIRP, if I put for example minimum 9 and maximum 12 they worked only in this range, it does not create areas of shade?



  • 15.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 11:13 AM

    @Rafap wrote:

    I disabled the HT 40 there is a week ago, since then the scenario has improved but not that much. I have a question regarding EIRP, if I put for example minimum 9 and maximum 12 they worked only in this range, it does not create areas of shade?


    That depends on the layout and how those APs are deployment .

     

    One thing you could do if you don't have Airwave is to download the standalone VisualRF and do a plan deployment with the map of that location , that way you can have an idea of how to signal propagation is in that area.



  • 16.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 11:16 AM

    I would get an eval version of Airwave and target the RF Heatlh report and the RF Capacity dashboard.  Let it run for a few days and look at the data.  It should give you a good indication of what's happening.  I think it's safe to lower from 15 to 12 dBm for min TX EIRP.  If you then look and see that ALL APs (2.4 radio) have tuned down to 12, then you may even be safe to lower to 9 in select spots.  



  • 17.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 11:20 AM
      |   view attached

    Here's to get an idea of how our RF coverage and how our environment.

    Thx



  • 18.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 11:30 AM

     

    You may have an issue because all those APs are in the hallway and they can hear each other too much vs if you had them inside the offices.

     

    Whats the structure of those walls ?

     



  • 19.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 12:12 PM

    Victor, 

    All possible and imaginable as glass, concrete, marble and plaster walls. This is the great challenge.

    In the latter case the idea is to reposition these points Justamante access in the rooms, but I want to minimize as much as possible before reposition them.



  • 20.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 12:19 PM

    You can also turn-off 2.4 GHz band on few AP`s by doing AP-specfic to avoid too much coverage after being done with the site-survey.

     

    Thx. 



  • 21.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 12:21 PM

    Sriram,

    One idea would be that, thanks for reminding, after a survey if I have an acceptable coverage but can turn off some radios 2.4, transforming them in monitor this frequency.



  • 22.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 08:51 AM

    @Rafap wrote:

    Hello to all.

    We have a highly dense network with multiple access points near and including the signal leakage between floors ends up affecting our use of channel time that is an AP with a high TX directly affects the others that are on the same channel, the next time or not. The fact is that even decreasing the power of the ARM have the co-channel interference, as can be seen in the attached figure. My question is: Is it possible to use the RX Sensitivity Tuning Based Channel Reuse to try to mitigate this interference? Sometimes we have 90% occupancy of the channel in one area so the RX received.
    We have enabled the ARM with the Client Aware enabled and no longer used the HT-40 just to avoid the aggregation of channels. We have 14 controllers 3400 and 500 AP's model AP125 connected, is our version of ArubaOS 6.2.1.3
    thank you


    I would:

     

    1.  Uncheck Client-Aware

    2.  Change the ARM Max TX Power to 18

    3.  Change the ARM Min TX power to 12

    4.  For now, do not use the RX sensitivity Tuning Based Channel Reuse, just to see what happens.  It seems like all of your APs are at 15, which means they could go lower.  12 or 9 is probably the lowest that you want them on.

    5.  Disabling 40 MHZ channels is good, but it will not do anything for 2.4ghz (b/g) channels; it would only help with 5ghz (a) channels.

    6.  Are you using "Drop Broadcast and Multicast" on all of your Virtual AP profiles?

    7.  How far apart are your access points?

     

     

    How far apart are your access points?



  • 23.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 09:28 AM

    Hello cjoseph

    I'll have to perform these tests by the parties, even to have a better understanding and control of changes, I will begin the same way you put it, in the same sequence.

    The question of distance between access points on average have 10 access points allocated in a hall of about 200 meters, with a single account would be one access point every 20 meters, assuming all are below the ceiling and targeted.
    thank you



  • 24.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 09:31 AM
    You should have no more than 4 access points in an open hall with no obstructions, because they can all see each other..

    Try turning off all but 4.


  • 25.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 09:42 AM

    An alternative to turning the APs off is to convert them to Air Monitors.  I agree with the other recommendations.  One word of caution, look at all APs in this AP Group.  Do you want to change ALL APs in this group or just a subset of them in certain areas?  If it's the latter, consider creating a new AP group with these settings and re-provision the APs into this new group.  

     

    I went through this recently with a client of mine.  It was an office area and a warehouse.  We created a new group for the office area and left the warehouse untouched.  

     

    This was the list I changed for this particular client:

     

    Drop BC and MC in Virtual AP profile
    Deny Broadcast Probes in SSID Profile --> Advanced
    Disabled low TX and Basic rates (set to 6&12).  NOTE: this prevents "b" clients from associating
    Set local probe threshold to 25dB
    Lowered Min Tx EIRP to 9 dB
    Advertised 802.11h and 802.11d
    •Converted a few APs to Air Monitors (2.4 GHz radio only)



  • 26.  RE: Avoid interference on same channel

    Posted Dec 02, 2013 10:57 AM

    Hi Seth,

    I think swapping some access points to monitor only going to create a very large shadow, further to 2.4 which is where most of our clients are associated. Currently we only have 2 ssid's being published on our network and we have disabled the network 802.11B clients, we allow only pure G, A and N
    The parameters to be modified I will bring them, but for parties, since any change that directly impact the customer is not welcomed here. I'll do the tests and will post the results.

    Thx



  • 27.  RE: Avoid interference on same channel

    Posted Dec 04, 2013 11:45 AM

    "You may have an issue because all those APs are in the hallway and they can hear each other too much vs if you had them inside the offices.

     

    Whats the structure of those walls ?"

     

     

    ^^ This!!!  We have an extremely dense deployment of Aruba with 4 of our sites having over 250+ AP and 3000+ clients daily in each.  Here are some suggestions I would make.

     

    Don't let APs see each other directly if possible.  This means putting them in rooms and not hallways.  When they are in the hallways, you get several bad things: users are on the other side of the wall(s) so they get reduced signal, APs will turn power down (see first point), interference indexes calculated by ARM will be higher than normal thereby adding possible issues with ARM, etc.

     

    Turn off at least 1/3 to 1/2 of the 2.4ghz radios (site survey needed for specifics).

     

    Turning off HT-40 really helps in many ways (you've already done that).

     

    Be careful with adjusting power levels.  Try to keep power levels fairly close for max/min.  We go as low as 9/6 in our 'ballroom' while some high density areas are 12/9.  Our normal levels are 18/15 for the 4 really high density sites mentioned above.  If you use a larger spread, say 18/12 then some APs will be 18 while many are 12... this causing a clumping of clients trying to get on the AP with power level 18 (it can happen but may not).

     

    If you start lowering power levels then consider removing some lower data rates.  This is an art more than a science so lots of testing will be required.

     

    Get the Aruba document(s) regarding how ARM calculates interference indexes (intf_index).  You can figure out a great deal with that information.  You will be able to determine when an AP should change channels and what channel it would probably change to as well.  Airwave can help with visuals as well.



  • 28.  RE: Avoid interference on same channel

    Posted Apr 10, 2014 09:03 AM

    Any updates on this?  I'm going through a similar exercise and it would be nice to know how you tackled the problem.



  • 29.  RE: Avoid interference on same channel

    Posted Apr 10, 2014 09:09 AM

    thecompnerd,

     

    The solution to any problem is site-specific.  If you could tell us your building construction, how far apart your access points are spaced, your user patterns and how many SSIDs you have, that would be a start.  Others can give you ideas, but not all would be applicable to your situation.



  • 30.  RE: Avoid interference on same channel

    Posted Apr 10, 2014 11:24 AM

     

    thecompnerd

     

    Actually the way we found to avoid this problem ended up being the repositioning of all our access points, which is also including a new project with new placements and acquisition of new access points.



  • 31.  RE: Avoid interference on same channel
    Best Answer

    Posted Apr 10, 2014 11:32 AM

    Actually the way we found to avoid this problem ended up being the repositioning of all our access points, which is also including a new project with new placements and acquisition of new access points.
     

     

    ***Sorry but at the time of writing I was at work a colleague season, so it came out his name.



  • 32.  RE: Avoid interference on same channel

    Posted Apr 10, 2014 10:14 AM

    Hi,

    I think my question is closely related to the subject.
    I am looking for a report or a command whihc will indicate areas with interference (APs on the same channel); we do have a lot of Aruba APs and some standalone AP on ADSL lines. ARM is sometimes limited by user connected and might have even left no choice by surrounding APs.
    I would like to help ARM by reconfiguring standalone APs ; but like I have mentioned; need to have indication of those areas first.
    thanks.



  • 33.  RE: Avoid interference on same channel

    Posted Apr 10, 2014 10:22 AM

    ravsv650,

     

    1.  RF is dynamic and that is why ARM exists.  Even if you come up with the perfect channel plan, there will be times when unexpected RF changes will need to be dealt with.

     

    2.  The administrator normally does not have the bandwidth to detect and change channels 24/7, and that is why ARM exists.

     

    3.  The 2.4ghz spectrum only has 3 non-overlapping channels so it is entirely possible in a dense or multi-story environment that there will be two access points on the same channel sitting next to each other..

     

    4.  To look at which access points have the most interference/utilization, look at the dashboard on the controller.  As time goes, on, this can change, along with your dynamic RF situation.



  • 34.  RE: Avoid interference on same channel

    Posted Apr 10, 2014 10:30 AM

    Totaly agree on ARM role and your comments but still need that overview.
    Checked Master and good news there because all 178 APs are on interfernece below 10%.
    We have another 10 locals and to avoid checking one by one I wonder if there is a summary in AirWave maybe ?



  • 35.  RE: Avoid interference on same channel

    Posted Apr 10, 2014 10:31 AM
    The RF health report in Airwave should give you an idea. By default it is limited to the 10 worst access points so you might have to run it against specific folders to get the info you need.