Measuring Signal Strength: RSSI and dbm

[trinpm]

Hi community,

From my research, there are 2 ways to measure signal strength:

1. RSSI - Received Signal Strength Indicator (usually 0-60 or 0-255,...).
2. dBm - Decibels in relation to a milliwatt (usually -30 to -100).

Different vendor goes with different way to measure signal strength collected by their APs. I think Meraki APs uses RSSI since I saw positive signal strength values in our data.

I saw a document [*] which shows conversion (from RSSI to dBm) for Cisco device as follows:

• 0 = -113
• 1 = -112
• 2 = -111
• 3 = -110
• 4 = -109
• ...
• 92 = -13
• 93 = -12
• 94 = -10
• 95 = -10
• 96 = -10
• 97 = -10
• 98 = -10
• 99 = -10
• 100 = -10

The above conversion applied when range of RSSI is from 0 - 100.

My question are:

1. Does anyone know if the above conversion table is correct (I understand it cannot be 100% accurate)? Is there any other way to convert RSSI to dBm?
2. If Meraki is using RSSI, what is the range of value? Is it 0-100?

Thank you,

Daniel

[*] source: https://d2cpnw0u24fjm4.cloudfront.net/wp-content/uploads/Converting_Signal_Strength.pdf

[PhilipDAth]

Note this special "Meraki" formula:

RSSI - 95 = signal strength in dBm

It's hard to find, but buried deep in this document:

https://documentation.meraki.com/MR/Monitoring_and_Reporting/Location_Analytics

[HodyCrouch]

For a bit more information, take a look at this thread: https://community.meraki.com/t5/Wireless-LAN/Displayed-Client-RSSI-equivalent-Client-Band-RSSI-table...

Key point is that Meraki often shows SNR rather than RSSI.

[trinpm]

Thanks Hody for the link.

Yes, but from their API, they instead reported the RSSI: https://documentation.meraki.com/MR/Monitoring_and_Reporting/Location_Analytics

I'm trying to figure out if that reported RSSI considered the noise floor yet..

[trinpm]

Thanks Philip for the information.

The formula "RSSI - 95 = signal strength in dBm": After applying it to have some number in dBm - do you know if that value considered the noise floor yet?

The one with consideration of noise-floor (Signal-to-Noise Ratio or SNR) seems to be the one exposed to user (not API developer): https://documentation.meraki.com/MR/WiFi_Basics_and_Best_Practices/Wireless_fundamentals%3A_Signal-t...

[PhilipDAth]

I don't know.

[80211WiGuy]

Thanks, 95 stuck in my mind as something familiar.

-95dBm is the starting point for the RX-SOP slider in an RF Profile.  I'm guessing -95dBm is also Meraki's min receive sensitivity.