# What is Signal-To-Noise Ratio (SNR)?

Signal-To-Noise Ratio (SNR) is defined as the ratio of signal power to the noise power, often expressed in decibels. A ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise. Read about SNR as related to cables, SNR in Class A & Class B Boosters, SNR in Signal Quality/ Speed, and SNR in Public Safety Boosters.

## Signal to Noise Ratio.

The SNR (Signal-To-Noise Ratio) of a system or component is defined as the ratio of signal level to the noise level. SNR is expressed in decibels. It is calculated by dividing the signal power by the noise power. A ratio bigger than 1 dB indicates that the signal is more than the noise. Conversely, if the ratio is less than 1, it indicates that the noise level is bigger than the signal level.

If the power of the signal is less than the power of the noise, i.e. the SNR < 1, the signal becomes unusable.

When an audio component for example has a SNR of 100 dB, it means that the level of the audio signal is 100 dB higher than the level of the noise. This means that a SNR of 100 dB is better than one that is for example 70 dB.

## Noise and Signal Boosting.

Cell phone signal boosters are designed to take the outdoor cellular signal, boost it, and rebroadcast it to the designated indoor space. It is unfortunately not possible to simply take only the signal you need to boost. Other energy sources, such as other radio signals, the weather and the sun's rays, all generate some background interference which need to be considered during installation.

Although it is possible to handle a limited amount of interference, this interference will eventually lead to problems if it is not addressed. When the SNR increases, the channel's data throughput also increases. This means that for a given signal level, an increase in noise will decrease the data throughput. The higher the noise level, the less space there is for the actual data that is being transmitted on the channel. The maximum throughput for a channel depends heavily on the SNR, even when multilevel encoding techniques are used.

Interference across all types of communication presents as static. Static is commonly known for its unpleasant sound, leading to the term noise. As the level of interference increases, the static noise becomes louder. This leads to problems hearing the other person on the call, and even to dropped calls.

Cell phone signal boosters don't create their own signals, but boost existing signals. This means that any noise at the outside antenna will also be amplified. Installers therefore have to test both signal quality and signal strength. If the outside signal has too much noise, the booster installation may well not be possible.

Signal booster product specifications normally contain the signal to noise ratio, abbreviated as S/N or SNR. Similarly, Signal-to-Quantization-Noise Ratio (SQNR). This specification is one of several that impacts a system's overall sound quality.