Principles of Communication Noise - Principles of Communication

What is Principles of Communication Noise?

In a few communication system, during the transmission of the signal, or while getting the signal, some surplus signal gets familiarized into the communication, making it hostile for the receiver, questioning the quality of the communication. Such a disruption is called as Noise.

What is Noise?

Noise is an unwanted signal which affects with the original message signal and spoils the parameters of the message signal. This modification in the communication process, leads to the message getting changed. It is most probably to be entered at the channel or the receiver.
The noise signal can be understood by taking a look at the resulting example.

noise


Therefore, it is assumed that noise is some signal which has no design and no continuous frequency or amplitude. It is quite random and unpredictable. Actions are typically taken to reduce it, though it can’t be totally removed.


Most common instances of noise are −

  • Hiss sound in radio receivers
  • Buzz sound amidst of telephone conversations
  • Flicker in television receivers, etc.

Effects of Noise


Noise is a troublesome feature which disturbs the system performance. Resulting are the effects of noise.

Noise limits the operating range of the systems

Noise ultimately places a limit on the pathetic signal that can be amplified by an amplifier. The oscillator in the mixer circuit may bind its frequency because of noise. A system’s operation rest on the operation of its circuits. Noise confines the smallest signal that a receiver is talented of processing.

Noise affects the sensitivity of receivers

Sensitivity is the least amount of input signal essential to attain the definite quality output. Noise disturbs the sensitivity of a receiver system, which ultimately affects the output.

Types of Noise

The classification of noise is done contingent on the type of the source, the result it demonstrations or the relation it has with the receiver, etc.
There are two key ways in which noise is created. One is over some external source while the other is formed by an internal source, within the receiver section.

External Source

This noise is created by the external sources which may happen in the medium or channel of communication, typically. This noise cannot be totally removed. The finest way is to evade the noise from affecting the signal.

Examples

Most mutual examples of this type of noise are −

  • Atmospheric noise (due to irregularities in the atmosphere).
  • Extra-terrestrial noise, such as solar noise and cosmic noise.
  • Industrial noise.

Internal Source

This noise is created by the receiver mechanisms while functioning. The components in the circuits, due to uninterrupted functioning, may create few types of noise. This noise is measurable. A good receiver design may lower the effect of this internal noise.

Examples

Most common examples of this type of noise are −

  • Thermal agitation noise (Johnson noise or Electrical noise).
  • Shot noise (due to the random movement of electrons and holes).
  • Transit-time noise (during transition).
  • Miscellaneous noise is another type of noise which includes flicker, resistance effect and mixer generated noise, etc.

Signal to Noise Ratio

Signal-to-Noise Ratio (SNR) is the ratio of the signal power to the noise power. The higher the value of SNR, the bigger will be the quality of the received output.

Signal-to-noise ratio at different points can be calculated by using the resulting formulae –

I n p u t S N R = ( S N R ) I = A v e r a g e p o w e r o f m o d u l a t i n g s i g n a l A v e r a g e p o w e r o f n o i s e a t i n p u t O u t p u t S N R = ( S N R ) O = A v e r a g e p o w e r o f d e m o d u l a t e d s i g n a l A v e r a g e p o w e r o f n o i s e a t o u t p u t C h a n n e l S N R = ( S N R ) C = A v e r a g e p o w e r o f m o d u l a t e d s i g n a l A v e r a g e p o w e r o f n o i s e i n m e s s a g e b a n d w i d t h

Figure of Merit

The ratio of output SNR to the input SNR can be termed as the Figure of merit (F). It is denoted by F. It describes the performance of a device.
F = ( S N R ) O ( S N R ) I Figure of merit of a receiver is –
F = ( S N R ) O ( S N R ) C It is so because for a receiver, the channel is the input.

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