Wireless Access

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Occasional Contributor II
Posts: 30
Registered: ‎01-19-2010

Auditorium Antenna Selection

I'm in the process of improving the wireless coverage in an auditorium space and need some advice on antennas.  I've read the VRD for auditorium and high density design, but there's no mention of 802.11ac or the newer 3x3 access points and I've read in a few places that some of the considerations change for higher performance requirements.

 

Here are the details on the space:

  • 1300 seats, completely open inside with no pillars or other obstructions.
  • I am only planning capacity for roughtly 100-200 users.  Students use the space to capacity, but wifi coverage is only needed for staff meetings in the front 1/3 of the seating area.
  • All 200 clients are 5 ghz.  We have purposely shifted our primary SSID to 5 ghz only and only use 2 ghz for guest access.
  • The ceiling is a minimum of 30 feet high.  Catwalks, conduit, and power are all easily accessible.  Wall mounting options are limited to one spot on each side and a minimum of 15 feet off the floor.  Floor installations are not an option.

The VRD seems to indicate serval omni directional antennas/access points would be suffient.  At the same time, the VRD is more targeted towards a normal 9-15 foot ceiling and I'm concerned the 30 foot ceiling here would result in a much wider cone of coverage and more overlap.  I could use directional antennas, but from what I understand, directionals are not great for the performance improvements in MIMO radios.  Any advice would be appreciated.

Guru Elite
Posts: 21,491
Registered: ‎03-29-2007

Re: Auditorium Antenna Selection

The AP105, 135 and 225 all have integrated downtilt omnidirectional antennas and can be mounted 40 feet above the coverage area in the overhead coverage model.  The VRD does not mention the AP135 and 225, because ithe VRD predates wide distribution of those access points.

 

 



Colin Joseph
Aruba Customer Engineering

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MVP
Posts: 562
Registered: ‎11-28-2011

Re: Auditorium Antenna Selection

I'm not a big fan of directionals, other than for outdoor p2p links.

 

I think first of all, I'd seek to understand if the user count of 200 is realistic and reasonable from a business perspective. I.e. sure they don't want to expand it to the full seat count ever? Really?

 

If it is 200, and the customer can afford them, 8 x AP225 (or similar) would be fine I would expect.

 

The 8 is based on maximum non-overlappers available to us in the UK for example. Not sure what region you're in?

 

Based on 8, that's about 25 clients per radio. Of course, you should check all the normal "bandwidth/application" demands bits.

 

Then consider only enabling 3 or 4 of those APs for 2.4ghz if desired (maybe by AP group)?

 

Mounting them under the catwalks facing directly down into the seats should be fine. You might want to do an exercise where you check the SNR at ground level and tweak TX powers down a bit, but you shouldn't REALLY need to if the channels select correctly automatically?

 

Kudos appreciated, but I'm not hunting! (ACMX 104)
Contributor I
Posts: 55
Registered: ‎10-04-2012

Re: Auditorium Antenna Selection

It depends on how you want to distribute the RF.  Are you willing to place AP's on a 30' ceiling?  If you are, using an omni will give you the most even distribution in all directions.  But, depending on the power output of each radio, you need to make sure they are far away enough from each other if you plan to reuse channels.  It sounds like that won't be a problem in your case because of the number of clients is 200.  What are the constraints of the project?  Will you be able to wall mount as an option?  How much bandwidth do you want to supply to each client?  I have always tried to keep each radio to a maximum of 20 clients, but you could get away with 50 max.  4-5 AP's?  Then balance the users across the channels in that auditorium.

 

 

Occasional Contributor II
Posts: 30
Registered: ‎01-19-2010

Re: Auditorium Antenna Selection


mbonadie wrote:

It depends on how you want to distribute the RF.  Are you willing to place AP's on a 30' ceiling?  If you are, using an omni will give you the most even distribution in all directions.  But, depending on the power output of each radio, you need to make sure they are far away enough from each other if you plan to reuse channels.  It sounds like that won't be a problem in your case because of the number of clients is 200.  What are the constraints of the project?  Will you be able to wall mount as an option?  How much bandwidth do you want to supply to each client?  I have always tried to keep each radio to a maximum of 20 clients, but you could get away with 50 max.  4-5 AP's?  Then balance the users across the channels in that auditorium.

 

 


 

Thanks for the replies everyone.  Wall mounts are not an option, but from the sound of things, ceiling mounted APs with internal omnis should be fine for the installation.  The bandwidth requirements for individual clients are not that high, but there are certain times where ac speeds would be a huge help.  I think several 225s should meet my needs.

Contributor I
Posts: 55
Registered: ‎10-04-2012

Re: Auditorium Antenna Selection

Cool.  Have fun with the 225's.  I have 35 of them serving 80 MHz channels in our IT office building with much success.  Remember that the 225 is dual core and will process faster by default over the 105/135's.  Excellent choice.

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