High Density WiFi Design

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Hi Guys

So I thought that I would get the communities comment on a specific High Density wireless design.
Could make for a interesting discussion.
 
We have a a open room, 100 meters by 50 meters.
The room is used for students to bring your own device and then write exams.
We should cater for 1000 students.
With the various tests we have done we see 70% 2.4Ghz devices and 30% 5Ghz.

What would your designs look like for something like this?
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Andre Brits Kannemeyer

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Posted 2 years ago

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Andre Brits Kannemeyer

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Just some more info.
The students connect to a VMware VDI solution.
We have monitored the bandwidth requirement for the PCoE (PC over ethernet) protocol that VMView uses and bandwidth varies depending on the content of the Exam in die VDI.
If the exam is pure text we need a little as 256Kbps but if the exam has HD images/Videos it spikes to 7Mbps per client.

So worst case we can work on 5Mbps per client..........
(Edited)
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Ronald Dvorak, Embassador

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Are they allowed to connect with more then one device or only with one for the exam.
I'd imagine that if every device is allowed they will connect with 2-3 per person - right ?

So with the in mind let's assume 2500 devices with 70% (1750 devices) on 2.4GHz would mean that you'd need at least 16APs (max.112 clients / radio > datasheet AP3935) in this "small" space.
With that ammount of clients you'd need also a dedicated V2110-large or C5210.

I'm very interested in the input of the community as I've never had such requirement/installation.
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Andre Brits Kannemeyer

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We can work on a single device per student during the exam,
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JP

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Are you seeing 70% 2.4 only devices or are they 5ghz capable and just not using it ?  
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Andre Brits Kannemeyer

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Alot of the students have very old "Hand me down" devices that only supports 2.4ghz
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Joseph Burnsworth

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This is very similar to a few school district auditoriums that i have done. With 1000 students/faculty, in my mind we are looking at 3000+ devices. I like to stick around 100clients per AP do this would be 30 AP's. All set to low power in a load group.

Im sure everyone is looking the screen like "30 AP's?"

this will keep with a solid balance of the 2500+ devices that are going to be in the room. Also, AP dependent, I would also LAG the AP's, 20mghz radios's,  rate limit the VNS, bridged at AP unless this is all guest traffic.

Definitely stick with the 20Mghz. You wont get multiple spacial streams to the AP, but everyone will be connected with good coverage and stable throughput

How much bandwidth do you have for internet?
(Edited)
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Andre Brits Kannemeyer

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The students will be connecting to a VDI session on the local lan.
No internet required but the bandwidth required for the VDI session depends on the content of the exam. the PCoE protocol dynamically increases or decreases the requirments based on the content in the VDI.
We have seen text only exams to take 256Kbps and then other exams with HD pictures/Videos spike to 7Mbps per client.

Also keeping in mind that bulk of the users is on 2.4Ghz, Channel reuse is very difficult even if the output power is set very low. The area is so small you will still see the other AP's
(Edited)
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Andre Brits Kannemeyer

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I agree with the 20Mhz and then rate limiting client connection speed to for example 1Mbps ect
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Joseph Burnsworth

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if you can keep it to 1 device per student, then we can keep it to 10 AP's with all of the above settings. If they can burst to 7mb then I would limit them to 7 mb and nothing more.

Youll see the other AP's, however, with the AP group and low output levels, it should balance them accordingly. Especially with 10 AP's. 11 channels, 10 AP's 1 channel to spare :)
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Joseph Burnsworth

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if you can keep it to 1 device per student, then we can keep it to 10
AP's with all of the above settings. If they can burst to 7mb then I would limit them to 7 mb and nothing more.

Youll see the other AP's, however, with the AP group and low output levels, it should balance them accordingly. Especially with 10 AP's. 11 channels, 10 AP's 1 channel to spare :)
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Jeremy, Embassador

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This is according to ekahau.... 

One is the overbuilt one the other is the standard one.. note.. some of the stuff is wrong because you would turn down / off  power on some 2.4 ghz radios... 

https://drive.google.com/file/d/0Bz0vq-5RLwenNTlkNjB3bktTbHc/view?usp=sharing
https://drive.google.com/file/d/0Bz0vq-5RLwenWjhydVRKYlNXbEU/view?usp=sharing
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Joseph Burnsworth

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Hey Andre,

Just wondering if you need any more assistance and brainstorming on this? Not sure about anyone else, but I am pretty excited to see what your final build plan is and how it works for you.

Let us know!
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Hartmut Sachse

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Hello Andre, this is really challenging from RF perspective. If 70% of your devices only can use the 2,4 GHz frequency band CCC/CCI (Co Channel Contention/Co Channel Interference) could limit clients throughput. From RF perspective you better should use access points with external patch antennas creating smaller coverage area/cell sizes per access point. Using 20 MHz channels in 5 GHz, too is recommended practice in high density deployments.

To calculate the ap count you could use Andy van Nagy's capacity planner:

http://www.revolutionwifi.net/capacity-planner/


Best Regards
Hartmut
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Pascal Lurquin

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Hi,

we are using the 4 channels plan for 2.4GHz ... it works great

Use the new AP with spatial streams and MU-MIMO ...

Pascal

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Hartmut Sachse

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A 4 channel plan could create adjacent channel interference decreasing overall throughput.  802.11ac wave 2 access points are a great idea. With a growing number of clients supporting MU-MIMO spatial streams could be used more effectively.
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FES

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Hi, I can read that if you only have 802.11gn the modulation used is OFDM. In that modulation the witdth channel is 20Mhz, and with this scenario you could use the 4 channel plan with out channel interferences, isnt it?
Also in this scenario we could disable protection modes on radio2, Is this correct?

I have testing this values in order to prove that the 4 channel plan works...