Balancing load on AP's

Unanswered Question
May 10th, 2007

Hello all,

I'm new to WLANs and dutch (what could be worse). Recently employed at a school I'm confronted with WLAN problems. Trying to understand it all I'm reading as much as possible and found this forum.

We're planning to have 2 AP's on a mobile cart servicing approx. 20 laptops. With my limited knowledge I understand the client connects to the AP with the strongest signal. Is it possible to prevent this?

TIY

Carl

I have this problem too.
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sethgarnar Fri, 05/11/2007 - 06:31

I've seen some wireless clients that have the ability to connect to a certain AP using its mac address. You could also set one AP to mac filter and use 10 laptops on that and the other AP would have the other 10 laptops. Maybe the easiest option is to have two SSID's AP1/AP2 then configure half the laptops to one SSID and the other half to the 2nd AP.

john.preves Sat, 05/12/2007 - 04:35

Certainly, the two ssid option will allow physical separation, provided the laptops do not need to roam. However, if that scenario is undesireable, the best way to physically load balance the network would be to perform a site survey and use lower powered cells to create smaller cell sizes that can only cover 'half' of the intended area. Two cells with 10 - 20 % overlap (same ssid) will create the physical separation you are looking for. The drawback to this, will be when more than half of the clients are on one side or the other. The fix to that will be to add more AP's at low power to add aggregate throughput.

If you have a room like a cubicle farm with very little in the way of signals, you need to be more creative as to where you place the AP's.

Case in point - a large break area (lunchroom) in a hospital. You will never get three or four AP's cells' small enough (without using pico cell methodology which will cost more than you probably want to spend). Rather then place 4 AP's in one room, place them in 4 rooms close by and let the signals bleed in to such a point where the physical balancing can be achieved. Granted the sweet spots will be on the other side of the walls and you may not need signal there, but the bleed over may be just enough to get what you need in the "lunchroom". This cannot be done properly without a survey.

carlhoogen Mon, 05/14/2007 - 13:37

Thank you for the help.

The AP's have to be placed on the cart, which in itself is positioned randomly in the classroom by the teacher. So I think creating two cells is nearly impossible. The idea of creating two SSID's seems a good one to me, but it creates a practical problem with using a particular laptop in another place in the building. On the other hand, maybe I better go for a single AP at first, just to give it a try.

Tx,

Carl

dbentley Tue, 05/15/2007 - 06:12

One AP might get you what you want for the short term, it really depends on the traffic you are generating. The next option might be moving toward LWAPP and using a small 2006 controller. This will get you the load balancing that you are looking for. Just something to think about.

The same SSID on both APs.. Set one AP to channel 11, one AP to channel 1. This will eliminate the chance of co-channel interference. Remember the maximum number of clients per AP is recommended to be 24. So you should be ok if you end up only having a single AP.

I understand you are new to the technology so i will give you instructions on how to limit the number of associations via the gui.

Connect to your AP's web interface

Click on the security tab on the left

Click on SSID Manager

Click on the SSID you wish to limit.

Scroll down towards the bottom. "Association Limit". Set each to ten.

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