Distance and temperature

[suke]

Hello.
I evaluated the effect of temperature and humidity on BLE connection stability.
I thought that the effect of humidity was higher than that of temperature, but the effect of temperature was high and the effect of humidity was small.
I would like to confirm whether the results of this experiment are correct.

Evaluation status
-One central device is connected to one peripheral device (both nRF52832 SDK v15.3  s132).
-Call sd_ble_gap_rssi_get() with BLE_GAP_EVT_RSSI_CHANGED event on the central device and output the log.
・Two devices are installed in a temperature & Humidity-controlled room at a distance of about 3 m.
・Humidity is constant (30%) and temperature changes (25℃→60℃→0℃→25℃)
・Humidity changes (30%→90%→about 0%) with constant temperature (25℃)

I have two questions.
1. RSSI fluctuates due to temperature changes as shown in the attached image. Is this result correct?
2. Are there any experimental reports of RSSI and communication distance due to changes in temperature and humidity of the Nordic device?

3.Why does the RSSI change when the temperature changes not constant for each channel?

Thank you.

[haakonsh]

RSSI fluctuates due to temperature changes as shown in the attached image. Is this result correct?

 Most likely. The ADC that measures RSSI is not that accurate, especially with respect to temperature. Humidity has little impact on the RSSI-ADC. 

 

Are there any experimental reports of RSSI and communication distance due to changes in temperature and humidity of the Nordic device?

 No, not really.

RSSI is not the actual Received Signal Strength, just an Indication. The actual range you have does not track the RSSI over changes in temperature or humidity.
You can determine the range by running a DTM between two devices and looking at the Packet Error Rate at different temperatures. 
I assumed you're using a small test chamber, so you will need to use 2.4GHz attenuators and external antennas.
Select an attenuation where your PER is close to 30.8% (BT SIG limit for the receiver sensitivity), and re-run the DTM at different temperatures/humidity. 
The goal is to observe the effect temperature/humidity has on the PER(link quality/range).

[suke]

haakonsh-san

Thank you !