2.4.7.6
Signal Quality
Cellular modems offer several signal quality metrics for determining if a device has a
good, poor, or bad connection with the network. These signal metrics are Received
Signal Strength Indicator (RSSI), Reference Signal Received Power (RSRP), and
Reference Signal Received Quality (RSRQ). RSSI measurements are available for
2G, 3G, and 4G connections while RSRP/RSRQ measurements are only available for
4G connections.
These three signal quality metrics differ as follows:
-
RSSI is a measurement that looks at the wide band RF power coming into the
modem from all sources, including all noise and interference from other
sources.
-
RSRP looks at the average of the RF power in the passband that the modem
and the tower are using to communicate and can be used to determine how
good the signal power is between the tower while excluding noise and
interference from other sources.
-
A poor RSRP signal can indicate that the modem is in a poor coverage
zone or there is an issue with the antenna connection.
-
RSRQ indicates the quality of the connection between the tower and modem by
measuring the quality of a received reference signal sent from the tower to the
modem.
-
A poor RSRQ signal can be an indication that there is noise interfering
with the modem's communication.
For 4G connections it is best to rely on the RSRQ and RSRP measurements as they
provide a more granular perspective on the cellular connection. Applications using 4G
devices that have 2G/3G fall back should also check RSSI in the event the modem
falls back to a 2G/3G network.
The table below shows the mapping of signal quality to the returned values from the
modem. Devices will typically start seeing some occasional connectivity issues, such
as dropped connections, when the signal quality is in the lower end of the "Fair" signal
quality range. When the modem is in the poor signal quality range connectivity may be
problematic.
PN 1002634 REV 1
© NimbeLink Corp. 2021. All rights reserved.
19
Technology
2G, 3G, 4G
LTE Only
LTE Only
Signal Quality
RSSI (dBm)
RSRQ (dB)
RSRP (dBm)
Excellent
RSSI > -70
RSRQ
≥
-8
RSRP > -80
Good
-70 > RSSI
≥
-85
-8
≥
RSRQ
≥
-12
-80
≥
RSRP
≥
-90
Fair
-85 > RSSI
≥
-100
-8
≥
RSRQ
≥
-12
-90
≥
RSRP
≥
-100
Poor
RSSI < -100
RSRQ <-12
RSRP < -100
