Different signal strength on SSIDs

[jigsaw2026]

Hi,

Just a quick question as I'm curious...I have 2 SSIDs being advertised by the same AP, and (at the edge of its range), one SSID shows 2 bars of strength on my laptop, the other shows 4 bars. This is the same with all APs throughout the building, and they are being controlled by a WLC. I guess it's a global config somewhere...any ideas?

Thanks!

J

[dennischolmes · Accepted solution]

Not actually a global config but more than likely an issue of the fact that SSID number 1 is the first advertised in the beacons. This is the one with the lowest data rate advertised so if you have lower data rates advertised it will appear to be of lessor signal strength than it really is.

[Rob Huffman]

Hi Dennis,

You always amaze me with something new and helpful. +5 points my friend.

Cheers!

Rob

[George Stefanick]

Dennis, are you saying that all ssids after number 1 go out at a higher data rate?? Im a bit confused by that ... can you please explain further for my pea brain .... thanks

[dennischolmes]

No, no, no not at all. It is a perception thing at the client receiver. The client sees the beacons that are broadcast. The lowest mandatory supported data rate goes out as a beacon. The client refreshes its SSID list with the SSIDs it sees advertised on the AP it just saw a mandatory data rate from. That's why you can never really trust the five bars system. Watch a spectrum analyzer or Airmagnet analyzer and you will see that all SSIDs from the same AP are at the same signal strength and SNR. Basically the client device is going with what it thinks it sees not what it actually sees.

[jigsaw2026]

Thanks Dennis, very useful and interesting info.

[George Stefanick]

5 stars from me ... This is a good nugget right here ... cutting and pasting this one into email for later follow up ...

Thanks Dennis!

[ralphfowler]

Dennis!

I think you may have just addressed a nagging problem I have been having on a city-wide outdoor mesh system.

This issue seems to be limited to the Windows Zero Config wreless client, which is what most of the users are using.

There are several SSIDs on the system. Two belong to an ISP and several others are ones I use for other things. The complaint from users is: "Why do I only have 2 bars on xxxx but I have all bars on yyyy"

I have posed this question to various Cisco folks and asked about everyone I know, including TAC, and no one seems to have an answer. I had pretty much decided it was a Windows (and perception) issue, and requested that Cisco work with Microsoft to fix it, since it has a high chance of causing user trouble calls for the ISP.

And as you mentioned, I had already verified that the actual signal strenth (dB)of all SSIDs was the same.

I don't remember back in the thread well enough whether there was a "solution" for this, but I am wondering if possibly I should remove all the SSIDs and re enter them with the ISPs one last. Do you think this might fix the majority of the issue?

Thanks

Ralph

[ericgarnel]

Wow!

this actually leads to me to a question....

If this is really the case, then theoretically, if I want one ssid to be stronger, I should have a non-broadcast ssid with an index of 1 before the ssid I want to have advertised as stronger with an index of 2 or higher. Assuming that the advertised strength is directly in correlation to the signal strength.

Ultimately, if signal strength is stronger than the advertised strength, that should be fine for you & I, but at the end of the day, the end-user perception is what we are left to deal with!

Back in my day, 5 bars would be good, but most of the time, we didn't make it past the 1st one.

[ericgarnel]

5 points to you Dennis!

[severi]

My problem is similar.

I have 3 on the same SSID AP.

The third SSID is not always displayed by all the PCs with Wireless Zero-Config and Intel Pro-Set, the display is done only occasionally.

If the beacon is transmitted to lower datarate and then to 1 Mbps, only the third SSID not always see the others for a problem not known to client Microsoft and Intel.

is it correct?

Mirko.

[ralsaid]

This is totally incorrect.

All SSIDs will be broadcasted at the same time with the same data rates.

If this did not happen, then it is a misbehavior and a bug should be opened.