Transmission Impairment in Data Communication
When analog signals are sent through a transmission media, it can be observed that the quality of the signals is weakened by the time it reaches the end point or the receiver. This nature is called signal impairment. There are three main reasons that have been identified to be causing transmission impairment .
1.Noise
2.Attenuation
3.Distortion
Noise :
When there are unplanned and random signals that get in the way of the signal that has been sent through a transmission medium, we term it as a ‘noise impairment’. A few different types of noise can be identified as:
- Impulse noise : Has high energy , comes from lightning /power lines
- Thermal noise : Due to extra signal created by moving electrons
- Induced noise: Comes from devices that act as sending antenna with the transmission medium acting as a receiver .
- Crosstalk noise: One wire affecting another
Image source : GeeksforGeeks
Noise can be produced by internal and external sources.
External noise : atmospheric noises , extra-terrestrial noises, industrial noise
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Internal noise : transit-time noise ,shot noise, thermal agitation noise ,miscellaneous
Measures of noise :
- SNR (Signal to Noise Ratio) — when this is higher , the quality of the signal transmitted is higher
SNR = Signal Power/ Noise Power
- Figure of Merit — Describing the performance of the device
F = Output SNR/ Input SNR
Attenuation :
When the signal strength drops as the distance of transmission increases resulting in a loss of energy to face the resistance of the medium we term this as attenuation. The solution that has been identified for this is the use of an amplifier or to use repeaters at fixed intervals. An amplifier would make sure that the original signal is recreated through the amplification of the attenuated signal. The unit of measurement used to measure attenuation, which is done by measuring the relative strength of a signal in two places, is called decibels (dB). The loss of strength relative to the distance is measured using dB per kilometer. Attenuation is highly dependent on frequency. A complex Fourier series can be used as an example to understand the nature of attenuation.
Image source : GeeksforGeeks
Distortion :
Distortion mainly happens when there are composite signals consisting of a variety of frequencies. This results in changing the form and the shape of the signal . The signal also gets delayed to arrive because the speed of propagation varies depending on the frequency and the medium. When they arrive at the receiver’s end at different times distortion occurs. There are several types of distortion as harmonic, phase and amplitude distortion.
Image source : GeeksforGeeks
Attenuation vs Distortion
