Signal vs Noise
Signal refers to both the process and the result of transmission of data over some media accomplished by embedding some variation. Signals are important in multiple subject fields including signal processing, information theory and biology
Signal-to-noise ratio (SNR or S/N) is a measure used in science and engineering that compares the level of a desired signal to the level of background noise. SNR is defined as the ratio of signal power to noise power, often expressed in decibelsA ratio higher than 1:1 (greater than 0 dB) indicates more signal than noise.
Definitions specific to sub-fields are common:
- In electronics and telecommunications, signal refers to any time-varying voltage, current, or electromagnetic wave that carries information.
- In signal processing, signals are analog and digital representations of analog physical quantities.
- In information theory, a signal is a codified message, that is, the sequence of states in a communication channel that encodes a message.
- In a communication system, a transmitter encodes a message to create a signal, which is carried to a receiver by the communication channel. For example, the words "Mary had a little lamb" might be the message spoken into a telephone. The telephone transmitter converts the sounds into an electrical signal. The signal is transmitted to the receiving telephone by wires; at the receiver it is reconverted into sounds.
- In telephone networks, signaling, for example common-channel signaling, refers to phone number and other digital control information rather than the actual voice signal.
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