3G UMTS Signal Strength Reference Guide
The following indicators are used to determine the quality of a 3G signal. The charts indicate rough guidelines as to what constitutes a particular level of quality, ranging from excellent to unusable.
To avoid performance issues none of these values should be in, or dip into the red. Optimal performance is achieved when all values are in the green.
Diagnosing Signal Issues
There are many reasons why signal performance can vary significantly, which is why it is important to accurately diagnose your signal issues so that the correct solution can be implemented. For more information on how to diagnose signal issues see our Guide to Understanding Poor Mobile Coverage, which contains advice that applies to mobile phones and mobile data devices.
RSSI - Received Signal Strength Indication
| RSSI | Quality | Description |
| ≥ -75 dBm | Excellent | Strong signal enabling maximum data capacity |
| ≥ -80 dBm | Good | Good signal and speeds with no dropouts expected |
| ≥ -90 dBm | Fair to Poor | Fair/usable signal with possibility of dropouts and slowdowns |
| ≤ -112dBm | Unusable | No usable signal - expect frequent disconnections and sluggish performance |
RSCP - Received Signal Code Power
| RSCP | Quality | Description |
| ≥ -60 dBm | Excellent | Strong signal enabling maximum data capacity |
| ≥ -75 dBm | Good | Good signal and speeds with no dropouts expected |
| ≥ -85 dBm | Fair to Poor | Fair/usable signal with possibility of dropouts and slowdowns |
| ≤ -125 dBm | Unusable | No usable signal - expect frequent disconnections and sluggish performance |
Ec/Io - Signal to Noise Ratio
This is a ratio of the received chip rate energy (Ec) to the interfering co-channel (Io); in other words, it is a signal to noise ratio. Because a payload is transmitted over multiple chips, as Ec/Io becomes poorer, some chips may not make it to the destination or may need to be retransmitted multiple times before the message can be successfully decoded. It is also a factor used by the mobile network to determine preciesly when to perform handover of user equipment to another base station.
| Ec/Io | Quality | Description |
| ≥ -6 dBm | Excellent | Strong signal enabling maximum data capacity |
| ≥ -10 dBm | Good | Good signal and speeds with no dropouts expected |
| ≥ -15 dBm | Fair to Poor | Fair/usable signal with possibility of dropouts and slowdowns |
| ≤ -20 dBm | Unusable | No usable signal - expect frequent disconnections and sluggish performance |
