Transmission Errors

Transmission Errors


It is virtually impossible to send any signal, analog or digital, over a distance without any distortion even in the most perfect conditions due to:

1. Delay Distortion
Signals of varying frequencies travel at different speeds along the medium. The speed of travel of a signal is highest at the center of the bandwidth of the medium and lower at both the ends. Therefore, at the receiving end, signals with different frequencies in the given medium will arrive at different times causing delay error.


2. Attenuation
As a signal travels through a medium, its signal strength decreases.


3. Noise
A signal travels as an electromagnetic signal through any medium. Electromagnetic energy that gets inserted somewhere during transmission is called noise.


Many attempts have been made to detect and rectify the transmission errors. Error detection schemes:

Vertical Redundancy Check (VRC) or Parity Check

Longitudinal Redundancy Check (LRC)

Cyclic Redundancy Check (CRC)

Error correction schemes:

1. stop-and-wait
2. go-back-n
3. sliding-window