When a remote gateway drops offline, the first thing a technician checks is signal. RSSI is the classic number for that - a measure of how strong the received cellular signal is. This guide explains RSSI, how it reads in dBm, and how it relates to the LTE metrics RSRP, RSRQ, and SINR that matter on modern networks.
Cellular Signal (RSSI) in one line: RSSI (Received Signal Strength Indicator) is a measure of the total power a cellular device receives, expressed in dBm; a less negative number (closer to zero) means a stronger signal, and it is used to gauge whether a remote site has usable connectivity.
RSSI is reported in dBm and is always negative for cellular. As a rough guide, around -65 dBm or higher is excellent, -75 to -85 dBm is good, -85 to -95 dBm is fair, and below about -100 dBm is poor - marginal enough to cause dropped sessions and retries. The exact thresholds vary by network and hardware, but the direction is universal: closer to zero is better.
The catch is that RSSI measures total received power, including noise and interference from neighboring channels, so a high RSSI does not guarantee a clean, usable signal. That is why on LTE and 5G engineers lean on more specific metrics rather than RSSI alone.
On LTE, RSRP (Reference Signal Received Power) isolates the power of the network's reference signals, giving a cleaner strength figure than RSSI: roughly -80 dBm and up is strong, while below -100 dBm is weak. RSRQ (Reference Signal Received Quality) and SINR (Signal-to-Interference-plus-Noise Ratio) describe quality - how clean the signal is relative to noise. A site can show decent RSRP but poor SINR, and it will still perform badly.
For a remote SCADA site, the practical takeaway is to read both strength and quality. A gateway that reports strong RSRP but low SINR often benefits from a better antenna, repositioning, or locking to a cleaner band rather than simply amplifying the signal. Getting signal right up front prevents the intermittent, hard-to-diagnose dropouts that plague marginal sites.
As a rule of thumb, around -65 dBm or higher is excellent, -75 to -85 dBm is good, and below about -100 dBm is poor. Closer to zero is stronger. On LTE, also check RSRP and SINR, since RSSI alone does not reflect signal quality.
RSSI is the total received power including noise and interference, while RSRP measures only the power of the LTE reference signals, giving a cleaner strength reading. On modern networks RSRP is the more reliable indicator of coverage.
Strong RSSI or RSRP shows the signal is present but not that it is clean. Poor RSRQ or SINR - from interference or noise - can cause retries and dropped sessions despite a strong reading, often fixed with a better antenna or a cleaner band.
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