RSSI value variation

[Jingar]

Hello,

              We are working on machine health monitoring system. For that we are using nRF52840 SOC as Central and nRF52833 SOC as end node. We had used single Central node and 4 end node in a single system. We have to put different end node at different position.

               To get better connectivity, we decided that we will decide  position of node based on value of RSSI. We are logging data of RSSI for central as well as for end node. It is observed that value of RSSI was continuously varying. Observed variation into value of RSSI is between 15 to 20 dBm. Even though we increased transmission power and observed  value of RSSI. Due to variation into RSSI, we can not judge about improvement into RSSI. So, what is the reason behind continuous variation into RSSI ? How can we achieve stable RSSI such that we can obtain variation within 5 dBm ? Are we missing something or any special algorithm required ?

             

        

[Andreas]

Hi,

 

This is normal as the signal strength of the wireless signal will differ depending on the position and orientation of the devices, and the channel between them. There is no way to workaround this, but you might be able to get cleaner results by conducting more measurements and filtering the readings.

 

Best regards,

Andreas

[Jingar]

Thanks Andreas for quick response.

In our case, both position and orientation were static for end node as well as for central node.So, only variable is communication channel, Am I correct ?

After pairing of central & end node, Will there also change in communication channel during any data transfer ?

[Andreas]

Hi,

 

Yes various objects and their position will have an impact on the signal strength, both between the devices and outside the exact line of sight. This variation is as expected. Typically to get consistent radiated RSSI you need to test in a 100% stationary environment, which practically is only possible to get in an antenna chamber.

 

Best regards,

Andreas

[Jingar]

Thanks Andreas, we understood very well.