Meaning
Logarithmic quality ratios compare the strength of a desired signal to the sum of all unwanted energy in the channel. The signal-to-interference-plus-noise ratio is the most accurate predictor of the maximum data rate a wireless link can support. Unlike simple signal strength, this metric accounts for the presence of other transmitters and the natural background noise of the environment.
Quality Calculation
Dividing the power of the carrier by the total power of the noise and interference produces a single value, usually expressed in decibels. A high signal-to-interference-plus-noise ratio indicates a clean channel where complex modulation schemes can be used reliably. If the interference from a neighboring network increases, the ratio drops even if the primary signal remains strong.
Modulation Stability
Maintaining a fast connection requires the radio to keep this ratio above a specific threshold for the selected data rate. When the signal-to-interference-plus-noise ratio falls, the receiver can no longer distinguish between the different states of the modulation constellation. This leads to bit errors that force the system to use a slower and more resilient transmission mode which reduces the throughput of the entire cell.
Error Probability
Low ratios are the primary cause of packet loss. Even with advanced error correction, a poor signal-to-interference-plus-noise ratio will eventually lead to a broken link.
