Wireless Access

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Occasional Contributor I
Posts: 10
Registered: ‎02-21-2013

Possible Interference?

Hi Guys,

 

Recently I went to a customer site for site survey. Picture below is the floor plan with VisualRF AP heatmap plot.

floorplan


The wall in between all the rooms is thick concrete and equiped with fireproof door.

 

user's requirement is to cover the whole corridor and rooms.

 

after I did the site survey, i found that the signal penetration is bad. Refer to the picture above, 7 x AP -135 in a row is barely fulfil the user requirement, but the signal overlap issue is quite serious in this scenario.

 

My dumb question is, how bad the interference in between the APs will be if really deploy it in the future?

 

Your answer will be greatly appreaciated.

 

Thanks

Yeap

Guru Elite
Posts: 21,270
Registered: ‎03-29-2007

Re: Possible Interference?

You need to put the access points in the rooms, period.

 

Please see the VRD for residence halls here:  PDF

 

Your design will not provide good coverage in the rooms and cause too much contention in the halls.



Colin Joseph
Aruba Customer Engineering

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Aruba
Posts: 1,377
Registered: ‎12-12-2011

Re: Possible Interference?

Here is a graphical example I just did yesterday using AP225s in a dorm.  Followed that VRD.  General starting place is alternate the APs on each side of the hallway.  So bottom left, start with the first room...skip two rooms, place second AP.  Other side of the hallway, skip first room, place AP in second...skip two, and place another AP. 

 

Alternate this pattern per floor.  So...floor 1 - bottom left room gets an AP.  Floor 2, bottom left room gets an AP on other side of hallway..

 

Example Floor 1

 

Screen Shot 2013-12-23 at 9.02.07 AM.png

 

Example Floor 2

 

Screen Shot 2013-12-23 at 9.05.58 AM.png 

Seth R. Fiermonti
Consulting Systems Engineer - ACCX, ACDX, ACMX
Email: seth@hpe.com
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Occasional Contributor I
Posts: 10
Registered: ‎02-21-2013

Re: Possible Interference?

Hi Cjoseph

 

this is what I concern about . May i know what is bad consequence of the contention if deployed? definitely i can't take any risk of it.

 

Thanks.

Aruba
Posts: 1,377
Registered: ‎12-12-2011

Re: Possible Interference?

You have to keep in mind that the APs are on different channels.  Even though the signal "bleeds" between them, the APs next to each other are talking on a different wavelength.  The  concern is at 2.4 where you only have 3 channels to work with.  However, ARM should take care of that for you.  In 5 GHz, there are many more channels you can use so co-channel interference is much less of a possibility. 

Seth R. Fiermonti
Consulting Systems Engineer - ACCX, ACDX, ACMX
Email: seth@hpe.com
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Occasional Contributor I
Posts: 10
Registered: ‎02-21-2013

Re: Possible Interference?

Hi SethFiermonti,

 

I try to simulate your design my floor plan, but the result doesn't seem good. there is thick concrete across the ceiling in between every floor. I doubt the signal can penetrate to above/below in this scenario.

 

Thanks.

MVP
Posts: 4,301
Registered: ‎07-20-2011

Re: Possible Interference?

[ Edited ]

 

You should try testing with Seth suggestion , we did similar setup this past summer and had really good results by wall mounting the AP135APs and placing them in between floors ( good bleed between floors ) .

 

The walls between rooms are CMU Block and it attenuates the signal by 25-35 dbm .

 

Another thing you may have to do is also adjust the ARM power levels Min/Max because in any of these type of deployments you will still see a lot of APs hearing each other on either band (.11g/.11a)

Thank you

Victor Fabian
Lead Mobility Engineer @ Integration Partners
AMFX | ACMX | ACDX | ACCX | CWAP | CWDP | CWNA
Occasional Contributor I
Posts: 10
Registered: ‎02-21-2013

Re: Possible Interference?

ok, I'll try test with Seth suggestion first. Stay for my update :)

 

Thanks!

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