Transmission impairment is the damage or harm caused to the signal during the signal transmission. Due to the transmission impairment, the signal received at the receiver end may differ from the signal sent by the sender. This difference in the strength of the signal is signal impairment.
Now the question what is the reason behind transmission impairment? The signal needs transmission media to travel from sender to receiver. The transmission media have some imperfection which causes transmission impairment.
The reason behind the transmission impairment is attenuation, distortion, and noise. In this section, we will discuss the reasons that cause transmission impairment.
Attenuation can be defined as the loss in the strength and energy of the signal. Whenever the signal travels through any transmission medium it has to overcome the resistance of that transmission medium doing which the signal some of its energy.
You may have experienced that sometimes the wire (medium) carrying signal gets a little warm. This is because the electrical energy in the signal is converted to heat while the signal tries to overcome the resistance in the medium.
To overcome this loss in the energy of the signal amplifiers are send at a finite distance to amplify the signals.
Distortion can be defined as the change in the shape or form of the signal while it travels through the transmission medium. Each signal component has its own propagation speed in the transmission medium due to which it has its own delay in reaching the final destination.
If the delay is not exactly the same as it may also create a difference in the phase of the signal. This means that the phase of the signal at the sender’s end is not the same as the phase of the signal at the receiver’s end.
For example, observe the composite signal in the figure below, as you can see it has components each of which is in a different phase. You can see that the composite signal at the receiver end has a distorted shape.
Noise can be defined as unwanted variation or fluctuation in the signal that may corrupt the signal. Noise can be classified into various types such as impulse noise, crosstalk thermal noise, induced noise.
Thermal noise can be defined as the impairment that is caused because of the random motion of the electrons inside the wire when the signal travels through the wire. This creates an extra signal inside the wire which is not originally sent by the sender.
Crosstalk is the impairment caused by one wire over another among which one is the sender wire and the other is the receiver. The impulse noise is a sudden spike in the signal which means signals with high energy which come from power lines lightning and so on.
The sources such as motor or appliance when act as the sender of signal then the noise generated in the circuit of the device due to varying magnetic field or electrostatic field is termed as the induced noise.
These are the causes of transmission impairments.