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I have project to deploy wireless networks for big meeting,who all have laptop.

We are planning to install all AP use the same SSID and connect to

at each location, we will install 03 AP with difference channel such 1,6,11

So I wonder how wireless clients to preffer which AP to connect, AP in channel 1 or 6 or 11?


And the second question : How can wireless client to know (do it know ?) to choose AP with have less congestion, or all wireless client will just connect to one channel and could not change to another channel (another AP), which have the same SSID


Please help me to understand how wireless client to choose and associate with multiple AP with same SSID in this case

Thank you
Tuan Nguyen from Vietnam

In this case, if all of your AP's are autonomous (no controller), the clients will connect to the AP that gives the best signal, there's very little you can do to control that.

Neil Mac
CWNT

neilmac Escribi?3:

In this case, if all of your AP's are autonomous (no controller), the clients will connect to the AP that gives the best signal, there's very little you can do to control that.

Neil Mac
CWNT

And best signal might fluctuate a lot, and not necessarily be "true".

Some software client utilities (like atheros) enable you to configure a preferred mac address. This will make a certain client sticky to what you think is the best AP for that client. This ofcourse is not an option for roaming clients.

I don't know how big the area is? But maybe you can play arround with the rates that you enable on the access points. If for example you configure the lowest basic rate at 6Mbit the beacons will also be send on that speed. Meaning they will not travel that far, resulting in less clients ping-ponging / edge clients.

In the end it will all depend on how big the area is, what service you expect (throughput, mobility?) and

To make a long story short, it wil be very hard in your situation to balance the clients between the AP's in a proper way.

aklepper Escribi?3:

I don't know how big the area is? But maybe you can play arround with the rates that you enable on the access points. If for example you configure the lowest basic rate at 6Mbit the beacons will also be send on that speed. Meaning they will not travel that far, resulting in less clients ping-ponging / edge clients.

Thank you for advice, the cover space was 40x60m, and there is Press Conference, which could have 700 participants with laptops -> they need quite high throughput.

So with your advice, I am planning to set lowest rate to be 11mbps, set the power tx to minimum, so the wireless beacons will at this speed to still support B and G client and signal will not travel too far.

Second thing, I suppose to use the same model of AP with same power TX, and locate these AP with the same height, with some distant between each other. In this case wireless clients could get right AP with better signal base on clients location, so clients connected to each AP could be more predictable ?

Please advise do my above choices are suitable, or do I need something more ?

Thank you

700 laptops all connecting from a single space?

You might look to a Xirrus kind of solution for the high density you need.

You should also offer different frequencies as part of your solution. I'm pretty sure most of those laptops will have an 802.11 abg card.

So if you split up and have two SSIDs - one for 2.4 GHz and one for 5GHz. (I like to call them something like "Press Access Slow" and "Press Access Fast" to *help* users to choose the 802.11a SSID)

The 5GHz signals don't cover as much area as the 2.4 and you can get smaller, more controlled cell sizes.

But at least take a look at Xirrus - they are a great solution in high density situations.

aklepper Escribi?3:

If for example you configure the lowest basic rate at 6Mbit the beacons will also be send on that speed. Meaning they will not travel that far, resulting in less clients ping-ponging / edge clients.

You will only get beacons at 6Mbit on OFDM (802.11a).

On HR-DSSS and ERP-OFDM ( 802.11b and 802.11g) the beacons will still go at 1Mbps, and in some circumstances 2Mbps (proxim, I beleive transmits at 2 under certain settings). The beacons will advertise that you can't connect at the lower rates though, you must use higher rates.

The beacons will travel the same distance regardless of the modulation, it's down to frequency. 5GHz will fade before 2.4 GHz.

Now we have a question of density, you should definitely be looking at a different option. Xirrus is ideal for this kind of installation, however if your users are receiving (ie multicast/broadcast), then you can also look at Extricom, who have some interesting solutions.

Neil Mac
CWNT

neilmac Escribi?3:

aklepper Escribi?3:

If for example you configure the lowest basic rate at 6Mbit the beacons will also be send on that speed. Meaning they will not travel that far, resulting in less clients ping-ponging / edge clients.

You will only get beacons at 6Mbit on OFDM (802.11a).

On HR-DSSS and ERP-OFDM ( 802.11b and 802.11g) the beacons will still go at 1Mbps, and in some circumstances 2Mbps (proxim, I beleive transmits at 2 under certain settings). The beacons will advertise that you can't connect at the lower rates though, you must use higher rates.

The beacons will travel the same distance regardless of the modulation, it's down to frequency. 5GHz will fade before 2.4 GHz.

Now we have a question of density, you should definitely be looking at a different option. Xirrus is ideal for this kind of installation, however if your users are receiving (ie multicast/broadcast), then you can also look at Extricom, who have some interesting solutions.

Neil Mac
CWNT

I doubt beacons are always send on 6Mb/s, anyway it might differ per vendor.

If you take extricom as an example they will send the beacons on the lowest basic rate configured. And it makes sense to me.

Do you have a source for your statement on the beacons? I don't believe it is written in the standards at least.

You are right on the propagation of the signal, but the goal is for clients not to associate to a "wrong" AP in this situation. As they will not be able to de-modulate the signal at higher rates far from the AP you will more or less have the same result. Not ideal, but might help in his situation ;)

tuannd Escribi?3:

aklepper Escribi?3:

I don't know how big the area is? But maybe you can play arround with the rates that you enable on the access points. If for example you configure the lowest basic rate at 6Mbit the beacons will also be send on that speed. Meaning they will not travel that far, resulting in less clients ping-ponging / edge clients.

Thank you for advice, the cover space was 40x60m, and there is Press Conference, which could have 700 participants with laptops -> they need quite high throughput.

So with your advice, I am planning to set lowest rate to be 11mbps, set the power tx to minimum, so the wireless beacons will at this speed to still support B and G client and signal will not travel too far.

Second thing, I suppose to use the same model of AP with same power TX, and locate these AP with the same height, with some distant between each other. In this case wireless clients could get right AP with better signal base on clients location, so clients connected to each AP could be more predictable ?

Please advise do my above choices are suitable, or do I need something more ?

Thank you

You will not make 700 people happy with 3 AP's, you will need a more dense solution. Is there a budget you have to hold yourself to?

Personally i never used xirrus, but they seem to have promissing case study's on deployments with the same requirements as you have.

With extricom you could make a very dense solution without having to worry about channel planning etc. You could even build a 802.11n blanket next to an 802.11a + 802.11b/g network to get optimal performance for all clients you might have.

It is a bit hard to tell from here what would be the best solution. You might want to make some calculations on what bandwidth will be required to see whether your solution will be feasible.

You may want to look at an Aruba controller based solution. They have a really helpful feature called "band steering". The controller will steer clients toward the uncrowded 5Ghz band. No need to create a seperate SSID.

If your going to attempt to provide a reliable and usable wi-fi connection for 700 users with 3 APs don't do it. Your users will just be complaining. I would think 10 or more APs in this space would be a more realistic number if your using 802.11a/g.

I would definelty use 5Ghz along with 2.4Ghz for this deployment.

Band steering will only work if there are enough end users with 11a cards to make a significant difference. Does anyone have any statistics as to the distribution numbers of end user devices with 11g, 11a/g and 11n cards? I'd love to see the numbers by year and device type.

I think we'd find that many hand held devices (cellular phones etc) only support 11g.

GT