Many people think this is the most important factor, but it isn't. Signal strength, which is called RSRP in 4G LTE and 5G networks, definitely matters. But it’s often not the most important factor. If your RSRP signal is stronger than around -100 dBm, then a stronger signal won't help increase your data rates.
SINR ( Important )
In 4G LTE and 5G networks, signal quality is measured as SINR. Increasing your SINR can have a dramatic impact on your connection speeds. The best way to improve SINR is to use a outdoor antenna.
RSRP - the Reference Signal Received Power is the power of the LTE Reference Signals spread over the full bandwidth and narrowband
RSRQ - Reference Signal Received Quality is a C/I type of measurement and it indicates the quality of the received reference signal (similar to EC/IO)
SINR - Signal to Interference plus Noise Ratio (A minimum of -20 dB SINR is needed to detect RSRP/RSRQ). Indicates the throughput capacity of the channel. As the name implies, SINR is the strength of the signal divided by the strength of any interference