There are various kinds of transmission impairments in network while transferring data and information through network
Types of transmission impairments:
Attenuation means a loss of energy. The strength of a signal falls off with distance over any transmission medium. For guided media, this reduction in strength or attenuation is generally logarithmic and is thus typically expressed as a constant number of decibels per unit distance. In fig. shows the effect of attenuation and amplification.
Distortion means that the signal changes its form or shape. Delay distortion is a phenomenon peculiar to guided transmission media. The distortion is caused by the fact that the velocity of propagation of a signal through a guided medium varies with frequency. For a band limited signal, the velocity tends to be highest near the center frequency and lower toward the two edges of the band. Thus, various frequency components of a signal will arrive at the receiver at different times. This effect is referred to as delay distortion, as the received signal is distorted due to variable delay in its components.
Noise is refers to any unwanted signal. For any data transmission event, the received signal will consist of the transmitted signal, modified by the various distortions imposed by the transmission system, plus additional unwanted signals that are inserted somewhere between transmission and reception; the latter, undesired signals are referred to as noise-a major limiting factor in communications system performance.