Wireless Transceivers

Greetings, I’ve been conducting extensive measurements of Uplink RSSI over an extended period to analyze its fluctuations in response to climate variations. The results I’ve obtained are rather intriguing. Initially, the RSSI values exhibit a standard variation, typically ranging between 3 and 5 dBi within the first hour. However, after an hour, the variations intensify, occasionally escalating up to 20 dBm between consecutive transmissions. These two distinct behaviors alternate cyclically after each hour how it looks in the next graph:

I conducted these measurements by consistently sending messages from a Heltec node LoRa32 v2 and receiving them via a gateway over a span of two days. I programmed the nodes using the “LoRaWAN_APP” library provided by Heltec, utilizing the LoRaWAN interruption example as the foundation. I rigorously tested the transmissions at intervals of both every 15 seconds and 1.5 seconds, observing similar patterns in both scenarios. Furthermore, I experimented with two different nodes to validate these observations.

I’m at a loss in identifying the root cause behind this peculiar behavior. Any insights or ideas you could offer would be immensely appreciated.

First thing that comes to mind is the effect of things around you: maybe there are devices in your home or neighborhood that also do stuff every x minutes / hours. They can cause interference in the cyclic way you mention. You would need to do the tests in a completely closed metal enclosure

It’s possible, but I believe it’s due to the device. In both cases—conducted on different days with varying time intervals between messages (1.5 seconds and 15 seconds)—during the period when the fluctuation happens, the messages consistently switch between low and high power almost exactly between two messages. I’ve illustrated this in the figure below, where I’ve plotted the same data in intervals of two for the 1.5-second scenarios:

In any case, I am going to try to improve the conditions to carry out measurements without interference.
Thank you very much for the reply!.

In case of 15-second scenarios:

On an as of yet unreleased LoRaWAN stack, Wireless Stick Lite V3 uplinking every ~35 seconds to TTN: