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Contributor II
Posts: 70
Registered: ‎05-01-2015

Could the noise affect the RSSI ?

Hi Guys,

 

Could the noise affect the RSSI?

Even the noise is very high, but I think it may not be able to affect the RSSI, right?

Aruba Employee
Posts: 159
Registered: ‎02-14-2013

Re: Could the noise affect the RSSI ?

That is correct. But it'll affect the SNR. 

 

Thanks, 

Rajaguru Vincent 

Thanks,
Rajaguru Vincent
CWNA | CWSP | CWAP | CWDP | ACMP
Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: Could the noise affect the RSSI ?

Thanks,

 

But what would happen if  STA get a very high RSSI but a very low SNR?

 

Because in RF Optimization profile, the AP only measures the RSSI.

 

Does the AP send a deauth to the STA?

Aruba Employee
Posts: 159
Registered: ‎02-14-2013

Re: Could the noise affect the RSSI ?

Hi, 

 

If RSSI is high, then SNR should also be high. 

 

For example, 

Noise floor =  -90 dBm

RSSI =  -35 dBm (high RSSI) 

SNR = 55 (high SNR) 

 

If RSSI is low, 

Noise floor = -90 dBm 

RSSI = -80 dBm (low RSSI) 

SNR = 10 (low SNR) 

 

In RF optimization profile, the RSSI threshold value can be 1-255. Here RSSI is not measured in dBm, but a relative measure of signal strength on a scale of 0-255. 

 

Thanks,

Rajaguru Vincent  

Thanks,
Rajaguru Vincent
CWNA | CWSP | CWAP | CWDP | ACMP
Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: Could the noise affect the RSSI ?

What if we increace the noise only, would the RSSI be affected by the high noise?

 

For example:

 

Noise floor =  -90 dBm

RSSI =  -35 dBm (high RSSI) 

SNR = 55 (high SNR) 

 

Some how, the noise floor increaced, maybe some one turned on a oven, then

 

Noise floor =  -50 dBm

 

Would the RSSI still be -35 dBM? 

Even if the RSSI still be -35 dBM, would the controller send a deauth to the STA because of the low SNR?

 

 

Guru Elite
Posts: 8,637
Registered: ‎09-08-2010

Re: Could the noise affect the RSSI ?

It's a ratio..

Sent from Nine

Tim Cappalli | Aruba Security TME
@timcappalli | timcappalli.me | ACMX #367 / ACCX #480
Aruba Employee
Posts: 159
Registered: ‎02-14-2013

Re: Could the noise affect the RSSI ?

Hi, 

 

Noise floor usually won't go that high in real world. 

 

RF optimization profile will look at only the RSSI. Noise or the SNR change will not trigger a deauth. If RSSI goes low, it will trigger a deauth. 

 

Thanks, 

Rajaguru Vincent 

Thanks,
Rajaguru Vincent
CWNA | CWSP | CWAP | CWDP | ACMP
Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: Could the noise affect the RSSI ?

Yes , it's a ratio.

We shouldn't say RSSI = -35 dBM, but RSSI can be convert to Power Value.

Like RSSI 50* K = -35 dBM , every vendor have a different K value.

Contributor II
Posts: 70
Registered: ‎05-01-2015

Re: Could the noise affect the RSSI ?

I think this a design flaw, Controller should measure bothe the SNR and RSSI. 

Aruba Employee
Posts: 159
Registered: ‎02-14-2013

Re: Could the noise affect the RSSI ?

ClientMatch does that. RF optimization profile is an old one. 

 

Thanks, 

Rajaguru Vincent 

Thanks,
Rajaguru Vincent
CWNA | CWSP | CWAP | CWDP | ACMP
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