RSSI mapped to signal 'strength'

1

Hi all,

I’m looking at building out on a tool that I’ve developed that presents me with a UI to enable me to provision sensors around buildings quickly. Currently, I just report the RSSI back from each sensor and use this to give me a good idea of ‘signal strength’. Now I understand that RSSI and SnR play equally, however I’d like to convert the RSSI reading(s) into a bar-graph, much like the one on your smartphone for cellular signal. If I had 5 bars, where would it be best to map the RSSI values?

I got my inspiration from a Particle Electron (3G MCU) where they did their mapping like this. Obviously not correct for LoRaWAN as the Link Budget differs:

/*   signal strength (u-Blox Sara U2 and G3 modules)
     *   0: < -105 dBm
     *   1: < -93 dBm
     *   2: < -81 dBm
     *   3: < -69 dBm
     *   4: < - 57 dBm
     *   5: >= -57 dBm
     */

Thanks

2

I’ve just found this reference on Github

https://github.com/IRNAS/Lora-signal-mapping/blob/master/images/color.png

3

So look at one of your typical buildings and see what the variance between RSSI reported actually is, strongest to weakest.

Then divide the range by the number of bars that you want.

4

Thanks - should it be a linear or logarithmic split?

5

RSSI is already a dB scale.

How you spilt it would rather depend on what use you want to make of the information.

If its of more interest to see how many nodes are close to reception failure (and if they are not close to failure, who cares) then SNR is a better indicator.