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WLAN for more than 200 clients (little bandwidth)

Posted on 2013-06-22
Medium Priority
Last Modified: 2013-10-21

for an event we have to build a wlan (internet-access) for 200-300 wlan clients. Those clients need not much bandwidth, because they are only smartphones and notebooks checking mails or something like this. It is a big room with  no walls beetween and the clients are not moving. So roaming isn´t needed.
Is it possible to mount 4 accesspoints (e.g. draytek ap-800), one in each corner and give them the same SSID. All APs are conected over cable to the same router (DHCP provided by this router). So in worst case, every client would connect to the lets say to the first AP. Is it possible to connecct 300 clients over one AP.
I know that in this case all those clients share the speed of this AP. But as i said they are only checking mails (and not all at the exactly same time).
Or do you know a better way of making this ?
It s only for 1-2 days, so we can´t buy equipment for thousends of euros...

thanks in advance
Question by:loosain
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Expert Comment

by:Zephyr ICT
ID: 39268003
How big is the room?
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Assisted Solution

edster9999 earned 668 total points
ID: 39268056
Assuming you are using the standard 2.4 GHz frequencies and not the newer 5 GHz, then you are limited to about 11 channels.  But using one channel it floods the channels round it by about two channels.  This means if you use Channel '6' it floods the channels 4 and 5 on one side and 7 and 8 on the other.
This gives you 3 channels that will not interfere with each other.
They are 1, 6 and 11

I would use 3 APs not 4 to keep the interference  to a minimum.
To spread them around, I would put one in a corner (say top left), the next one in the corner on the same wall (say bottom left) and the last one in the middle of the right hand side wall.

Use the same SSID network name, the same password / security settings, and the same IP range and people should roam from one to another as they cross the room.
Speaking of IP - You'll need to have a big enough IP range to handle all those people.
You'll need a 23 bit network mask ( which would give you 512 IPs (a few will go for broadcast addresses, network equipment and servers etc)

Author Comment

ID: 39268174
a subnet was clear to me. This is managed by the router and its build in dhcp. The point with the frequencies is a good one. so 3 APs would be better than 4 APs interferring...

@spravtek: the roo is 60m x 30m

Anyone any idea if the Access Point of  draytek (AP-800) can handle over 100 WLAN-Clients at one time ?
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LVL 20

Expert Comment

ID: 39268458
100 clients or 300 if they all go to one corner at the same time :) , is a lot of clients
Any wireless AP will struggle with this many.
It may be low band width - but the available bandwidth is shared between them all.

If it is running as 802.11n the maximum speed you could get would be 300 Mb/s.
You would not be running at this speed.  For one thing you need to turn off channel bonding (also known as dual channel or 40 MHz operation).  If you had it turned on each router would run on two channels (like 1 and 6 or 6 and 11) so you'd end up clashing again.
This instant reduces to 150.
Then the speed will drop due to distance or different devices running different standards.
100 Mb/s is in my opinion the best speed you would get.
If older devices force the router to drop back to earlier wifi standards it may be running at 54 or even 11Mb/s
The bandwidth is shared - so even if they are not using it very much it will still be down to 0.11Mb/s.... Thats 110 Kb/s or just marginally faster than old phone dial up speeds :)

Author Comment

ID: 39269134
ok, but this is only the worst case. Normaly some Clients connect to the first some to the sceond and the rest would connect to the third AP. I think 200 will be the highest i have to calculate with.
I have to ask if i can turn off dual channel with 802.11n. I found no chance to operate with n-Standard without dual-channel...
So if i offer only 54mbit with 200 Clients, i would get 250 kbit/s.
Not fast, but for only getting some small mails, would be enough. And normally not all Clients doenloading at the exact same time.
Or do those APs offer a Maximum of bandwidth no matter the other Clients are idle or active ?
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Assisted Solution

by:Zephyr ICT
Zephyr ICT earned 664 total points
ID: 39269170
My opinion is this:

I would foresee at least 6 AP's, unless you are concentrating all the AP's in one part of the building, like for example around a stage or something, then 4 might be enough, but I doubt it. Besides better spread, you'll have some redundancy as well. Might keep one or two AP's as reserve to put one up extra in zones where deemed necessary.

The consensus around WiFi at conferences is that you should use as many AP's as possible. then lower the antenna power as much as possible to decrease the range of each AP, of course not too close together if adjacent channels are configured, but you know this. Also try to avoid encryption to put less strain on the CPU (I know about security etc, but it might outweigh the benefit here, besides there's other possibilities).

Another thing to take into account is that most users will have more then 1 WiFi enabled device, let's say an attendee brings his tablet/laptop and his (smart)phone, he/she probably would like both of them to be on the WiFi network, so that's 2 devices, now let's say half of your attendees will do this, that's an extra 100-150 devices that will be using your WiFi...

Make sure your broadband connection is up to the task (as in enough bandwidth), it would be a shame if your WiFi network is optimised but somehow the broadband connection isn't taking to the load like it should.

Try to use separate SSID's for the 5GHz network part, this way you can separate the "weak" from the "strong"...

Take into account, you're dealing with people, they will always do things you aren't expecting, dealing with WiFi at a conference, no matter how small, will acquire someone to monitor it and act on things when needed (someone is downloading things hogging bandwidth, toss him off or block the source/destination IP)

For a small venue with around 300 people, you'd be paying about 2000 Euro's/Dollars if you'd be asking some (reputed) company to provide a WiFi network and bandwidth, depending on country, location, venue ... etc.

There's much more to it, I'm high on caffeine from an all-nighter so I probably missed a few things... But it seems you're on the right track mostly.
LVL 47

Accepted Solution

Craig Beck earned 668 total points
ID: 39269861
Rule of thumb... no more than 30 clients per radio at a time - ever.  Any more than this and you should expect issues, no matter what the clients are doing.

Do the sums... 300 clients / 30 clients per AP = 10 APs

Make sure you use dual-band APs (so 2.4GHz and 5GHz).  This will help greatly when trying to deal with channel allocation as 5GHz offers around 15 non-overlapping channels and if your clients are using Apple devices they'll be able to use the frequency.

Author Closing Comment

ID: 39589356
worked fine. thanks for your knowledge

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