SINR (Signal to Interference plus Noise Ratio) compares the power of the wanted signal with the combined power of interference and background noise at the device's antenna. Of the common cellular radio measurements, it is the one most closely tied to the data throughput a connection can achieve.

SINR is reported in dB and, unlike RSRP and RSRQ, higher positive values are better. 20 dB or higher is excellent, 13 to 20 dB as good, 0 to 13 dB as fair to poor, and 0 dB or lower as poor. A strong RSRP with a low SINR means the router can reach the network but cannot carry data at speed.

SINR shapes throughput because it determines how densely data can be packed into the radio signal. LTE devices use SINR to calculate the Channel Quality Indicator (CQI) they report to the network, which the network uses to choose a modulation and coding scheme. A high SINR supports higher-order QAM and fewer retransmissions, while a low SINR forces more conservative modulation, lower speeds and higher latency.

In LTE, SINR is not defined by 3GPP and is not reported to the network, so the calculation is left to the modem. Readings can therefore differ between modem manufacturers, so compare SINR values from the same router model rather than across different devices. In 5G NR, SS-SINR is formally defined in 3GPP TS 38.215.

Low SINR alongside good RSRP typically indicates interference, for example an elevated antenna that can see several cells at similar strength, or heavy traffic on neighbouring cells. Common remedies include repositioning the antenna, using a directional antenna aimed at a single cell, or trying a different band or network. On Teltonika routers, SINR feeds into the RutOS Signal Quality score alongside RSRP and RSRQ, and Teltonika RMS can record SINR history to show whether poor readings are constant or confined to busy periods.

‍