A frequent question that users of the Intwine Connected Gateway have is “what do the bars on my ICG really mean?”
The simplest answer is that more bars are better and indicate that you are closer to a cellular tower. This means that your system should have better upload and download speeds. As long as you have any number of bars you will have an internet connection. However, 1 bar indicates that you are on the edge of the range for the closest tower and you may experience intermittent outages (based on weather, minor problems at the tower, etc) and will likely have lower data speeds.
For a more technical answer, the bars indicate the average amount of power in the frequency range that carries data. For 4G LTE networks, this value is called the RSRP (Reference Signal Received Power). This value is reported by the cellular modem in dBm and ranges from -44 to ‑140dBm where higher magnitude values indicate more power. While there is no standard conversion from RSRP to bars, we’ve produced the following table based on field experience and typical industrial approaches.
# of Bars
-105 up to -90
-113 up to -105
-120 up to -113
However, RSRP is not the whole story. Data speed is based on a large number of factors including weather, cell tower loading, noise in the spectrum, reflections, and a host of other factors. To provide an accounting for some of these, additional metrics exist to help determine the quality of the signal. Key amongst these for LTE networks is RSRQ, Reference Signal Received Quality. This metric ranges from a high of -3dBm to a low of -19.5dBm.
Why did we use the bars to indicate RSRP instead of RSRQ?
The primary objective of the bars is to assist the user with placement of the ICG. To this end, RSRP is the ideal choice as a system sitting in one place will not see much variability in RSRP. Since RSRQ is intentionally designed to be influences by a number of other factors it tends to move around even when the ICG is in the same place.
To help with debugging of cellular signal issues, both RSRP and RSRQ are reported on the ICG’s local configuration webpage.