Various modulating and encoding schemes have been devised to provide protection against the errors caused by channel distortion and channel noise. Both noise and distortion are commonly introduced by all transmission media, and they both result in errors in reception. Distortion is any undesired change in the amplitude or phase of any component of an information signal that causes a change in the overall waveform of the signal.
Noise is the presence of random, unpredictable, and undesirable electromagnetic emissions that can mask the intended information signal. Signal degradation generally falls into three types: noise, distortion, and attenuation (reduction in power). All transmitted signals are to some extent degraded by the environment through which they propagate. Maintenance - содержание и техническое обслуживание, уход текущий ремонтĪvailability - возможность использованияĮvery telecommunications system involves the transmission of an information-bearing electromagnetic signal through a physical medium that separates the transmitter from the receiver.
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