ā11-18-2013 06:53 AM - edited ā07-04-2021 01:17 AM
Hello,
I've been observing with multiple access points and multiple wireless clients that RSSI signal received varies even 10dBm depending on whether the device is associated with the access point or just is listening to. When is associated is the maximum value.
Why this variation occurs?
What would be the correct value, the device gives me when I am associated or gives me when I'm not?
Thanks
ā11-18-2013 09:22 AM
You always want to look at the RSSI on an associated client.... clients that are not associated will not tell you anything to be honest.
Thanks,
Scott
Help out other by using the rating system and marking answered questions as "Answered"
ā11-19-2013 12:46 AM
I think it is also important the signal level that receive not associated devices, because to join need a minimum level of signal, at least enough to "listen" to the AP.
For example if I disable in AP data rates lower than 54Mbps, the client will need a signal level of at least -71 dBm to listen the AP, according to this table:
We also know that mobile devices such as smartphones or tablets are more "deaf" and therefore it is important the signal level that can listen without being associated with the AP.
In any case my question is why there is this difference between the values āāwith or without associated associated device? has something to do with the antenna gain of the AP or client technologies like client link?
What would be the correct way to measure for a site survey?
ā11-19-2013 04:39 AM
Well the issue is that the client is listening to all the beacons in the air. If you have tools like AirMagnet or Ekahau, those can run in passive mode to determine valid RSSI. If your looking at a Windows machine using the windows tool, I would say no. Use a tool or a free tool and I would say yes. Otherwise, association will really tell you the RSSI for that client be a use that client and ap has negotiated its modulation and will continue to negotiate. You will see a slight difference in RSSI from a passive and active client.
Sent from Cisco Technical Support iPhone App
ā11-26-2013 10:58 AM
Sometimes I use inSSIDer software, and with it the result can vary up to 10 dB being associated (active mode) to not be associated (passive mode). With other devices or software i see +-7dB difference. I think it's not a small difference, and so I wanted to know what is due to know which is the best way to make the site survey.
In the attached picture you can see the screenshot of how the signal varies from -50dBm (stable) being associated, to -60dBm about without being associated.
I do not understand why if the RSSI level is a parameter of radioelectrical power it varies being associated or not ... power emitted by the AP is the same, not it?
ā11-26-2013 09:22 PM
Well in passive mode, the device is scanning various channels as when compared to an actual association. The expensive tools allows you to passively scan an ssid and not all SSID's like many of the free tools. Fluctuation is minimal with these tools. You might want to email the tools support or if they have a forum, ask the question there. They probably can answer your question.
Sent from Cisco Technical Support iPhone App
ā11-21-2013 09:55 AM
RSSI is a Radio-Frequency (RF) term and stands for Received Signal Strength Indicator. It is a measure of the power level that a RF device, such as WiFi or 3G client, is receiving from the radio infrastructure at a given location and time. For instance, the power level a laptop is detecting from a nearby AP.
Usually, the higher the RSSI the better the quality and speed of the communication through the radio segment.
The closer the figure is to zero, the better. So in the figures you've given above, -75 is better than -100.
In my experience -75 provide a reasonable service. -85 provides an OK service. -100 provides a barely usable service. -110 provides no service at all.
This figure represents your signal strength to the cellular tower. The closer you are to a tower, the closer to zero the number will be.
Note that although I mentioned above that -75 provides a reasonable service, keep in mind that if the tower you're connected to is heavily congested the service won't be all that great. It is similar to the way in which ADSL works - even if you sync at 24mb/1mb, if the DSLAM is heavily congested, you'll get poor throughput.
Discover and save your favorite ideas. Come back to expert answers, step-by-step guides, recent topics, and more.
New here? Get started with these tips. How to use Community New member guide