Difference of two RSSI value

1

Hi,

I received a raw beacon message from gateway V4 v1.2.5.22 below:

00 dd cd 99 db 44 48 d3 02 01 06 1a ff 4c 00 02 15 fd a5 06 93 a4 e2 4f b1 af cf c6 eb 07 64 78 25 00 01 00 02 d8

  • Based on the header info page, the byte 0xd3 is RSSI = 0xd3 -256 = -45.

  • In the raw advertising data format below, the byte 0xd8 is RSSI at 1m = 0xd8 -256 = -40.

    format
    format1158×448 18.9 KB

Why there are two RSSI value, what is the difference?

Thanks.

Cheers,
Paul

2

The 0xd8 is measured power bit. see What is Measured Power

3

Thanks for you quick response, I still a bit confused.

Let me try to understand:
beacon_rssi

  1. For example, gateway measures RSSI of the beacon message from a beacon device one meter away
  2. This RSSI is the Measured Power
  3. This Measured Power value then is hard coded into beacon message as a reference?

My question is what the beacon’s transmitting power is when measure this Measured Power?
If I change the transmitting power on beacon device, does this reference will also change?
Do you have a table mapping the Transmitting Power --> Measured Power?

Thanks.
Paul

4

No. You need do measure RSSI at 1 meter and write new measured power to the beacon.

No. It’s depend on your hardware. For Transmitting Power 0dBm, the measured power is usually -59dB.

5

Hi,

Thanks for your support.

Now I understand. It is a value for me to set based on my settings and calibration.

This is very helpful, thanks.
Paul