What are the LTE signal levels and what should be the optimal values?
In the LTE modem web configurator on the System Monitor > LTE Status page, you can view the current state of the LTE connection. To determine the quality of the signal, pay attention to the following fields:
- Signal strength
The following table shows the different values of these parameters, which correspond to very poor (Cell Edge), poor (Mid Cell), good (Good) and very good (Excellent) LTE signal quality:
Next, we briefly explain each parameter that determines the quality of the LTE signal.
The signal strength value indicates the level of the LTE signal received by the modem. These values correspond to the RSSI (Received Signal Strength Indication) readings of the LTE connection. The value is measured in dBm (dBm). Additional information on the RSSI indicator can be found in the article: “Signal Quality Indicators in LTE Modems”
RSRP (Reference Signal Received Power) - the average power of the received pilot signals (Reference Signal) or the level of the received signal from the Base Station. The RSRP value is measured in dBm (dBm). The signal strength of the LTE modem can also be determined using the SIGNAL STRENGTH indicators on the top panel of the device. The maximum level correspond to the three burning indicators. If no indicator is lit, then the signal strength is insufficient to connect to the LTE network. With RSRP = -120 dBm and below, the LTE connection may be unstable or not installed at all.
RSRQ (Reference Signal Received Quality) - characterizes the quality of the received pilot signals. The RSRQ value is measured in dB (dB).
SINR (Signal Interference + Noise Ratio) also called CINR (Carrier to Interference + Noise Ratio) is the ratio of the signal level to the noise level (or simply the signal-to-noise ratio). The SINR value is measured in dB (dB). It's simple: the higher the value, the better the signal quality. At SINR values below 0, the connection speed will be very low, since This means that there is more noise in the received signal than the useful part, and the probability of losing an LTE connection also exists.
CQI (Channel Quality Indicator)
For each subscriber station UE (User Equipment) and each frequency block of the carrier, CQI channel quality indicators (Channel Quality Indicator) are formed. Depending on the data transfer rate required by the UE, the base station makes a decision on the number of resource blocks allocated to a particular user, and which frequency blocks to allocate to users depends on the CQI indicator. Users are allocated those resource blocks that have the highest CQI, and therefore the best signal-to-noise ratio. This parameter can take values from 0 to 15. The higher the value, the better (the higher the speed that an LTE base station can allocate).