topic Re: RSSI reading comparisons in SmartZone and Virtual SmartZone

RSSI reading comparisons

philip_francis1 — Tue, 11 Jan 2022 01:57:29 GMT

Hello, when looking at the RSSI readings for clients in Smartzone I notice they appear a lot worse than when actually on site using a tool such as INSSIDER to show RSSI levels.

For example, the Smartzone client RSSI level might show -75dbM, however when using INSSIDER on the local laptop the RSSI is much better at -60dbM.

My question is how reliable/accurate are the SmartZone RSSI levels shown for clients ?

What could be causing these differences ?

Re: RSSI reading comparisons

Anonymous — Tue, 11 Jan 2022 06:17:49 GMT

Hi @philip_francis_3lh2kfry55kua,

The RSSI value presented in SZ is the value reported by Clients to AP at any given distance. Try moving the spectrum analyzer (Inssider) close to AP in question and check if the RSSI value approximates. We can't expect the same value, as the client reported RSSI value would differ from Vendor to Vendor.

You could run below command from AP CLI for current RSS Value.

get station <WLAN_ID> info

Regards,

Parikshith

Re: RSSI reading comparisons

jamie_walmsley — Tue, 11 Jan 2022 06:36:43 GMT

The value shown on the SZ is what the AP is hearing the client at. Inssidr is showing it from the client perspective

depending on the configured AP tx power the AP is likely to be transmitting at a much higher power level than what the client device is TXing at, which could be contributing to why the values are so different. (Although the AP will have a better receive sensitivity and a higher gain antenna usually)

Re: RSSI reading comparisons

philip_francis1 — Tue, 11 Jan 2022 17:59:15 GMT

@parikshith_nagaraj_aa0004

Thank you. I have run the AP command 'get station <WLAN ID> info' and these RSSI values match exactly the INSSIDER values from the local laptop.

Therefore I want to understand why the SmartZone client RSSI values are so much higher than the values from the AP CLI and INSSIDER.

Thank you,

Re: RSSI reading comparisons

Anonymous — Tue, 11 Jan 2022 18:12:51 GMT

@philip_francis_3lh2kfry55kua it takes some time for the AP to report client values to SZ. If the client is frequently roaming between APs we could expect value mismatch. Another possibility is the RSSI value is state in SZ.

Regards,

Parikshith

Re: RSSI reading comparisons

eizens_putnins — Mon, 17 Jan 2022 15:02:32 GMT

I agree with Jamie, SZ reported value is client signal level received by AP.

It's also completely normal that communication is non-symmetric. Typically, client has less Tx power, much worse antenna, which results in lower RSSI on AP side (which is compensated by better sensitivity and better antenna). In the same time, AP has more power (it usually uses full power), has much better antenna -- which compensates worse client antenna and lower client sensitivity and provides higher speeds for download, as usually is needed.

Re: RSSI reading comparisons

philip_francis1 — Mon, 17 Jan 2022 21:01:46 GMT

Thanks guys.

Up until now we have been using the Smartzone GUI RSSI values as a guide as to whether signal in the offices was good or not.
Now, based on this information, it seems we can only use these readings as a very rough estimate of how good the signal strength is between client and AP.

Re: RSSI reading comparisons

jamie_walmsley — Tue, 18 Jan 2022 07:29:55 GMT

Yeah , there is no mechanism for the AP to know what SNR the client heard a frame at. Only way to get that info is from the clients themselves unfortunately.

When i look at a wireless issue I usually look at the reading on the AP/SZ coupled with the reading on the client , so you are getting both sides. As Eizen mentioned, it is not symmetric.

What I usually find in my environments is that the return SNR (AP hearing what the client is transmitting) is worse than what the client hears the AP transmitting at.

the result is you get higher data rate (mcs rate) from the AP transmitting to the client, than you do from the client->AP. This is usually because the AP is transmitting at a much higher TX power and in my environment, I typically have relatively weak clients i.e low RX sensitivity/ antenna gain (mobile phones, IoT type devices etc)

However this is going to be dependant on your environment, configured TX power, client devices etc.

Personally I try and match the TX power of the APs to the TX power of my weakest clients (in my case its usually things like Amazon Echo's) so I can at least attempt to get a roughly similar TX rate in both directions. https://clients.mikealbano.com/ is a good resource for client capabilities