Why do we consider zero mean for gaussian noise in a communication channel?

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Discussion Overview

The discussion revolves around the reasons for considering zero mean in Gaussian noise within communication channels. Participants explore the implications of DC components in noise and the practicalities of noise modeling in analog systems.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question why Gaussian noise is assumed to have a zero mean and whether it can contain a DC component.
  • One participant suggests that a DC component implies energy is permanently leaving the source, which could lead to the source "evaporating" and eventually ceasing to exist.
  • Another participant retracts their earlier explanation about the DC component, indicating uncertainty about the reasoning behind the zero-mean assumption for AWGN.
  • A participant notes that in analog equipment, low-rate drifting of DC levels is typically due to other effects rather than Gaussian noise, and that channels are often AC coupled to mitigate issues related to DC.
  • There is a discussion about the term "matter of semantics," with one participant explaining that it refers to the different meanings attributed to words and assumptions made by individuals.

Areas of Agreement / Disagreement

Participants express varying opinions on the significance of DC components in noise and the rationale for assuming zero mean in Gaussian noise. The discussion remains unresolved, with multiple competing views presented.

Contextual Notes

Participants mention practical considerations in analog systems, such as AC coupling and the relevance of noise power at low frequencies, but do not reach a consensus on the implications of these factors for the zero-mean assumption.

dexterdev
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Hi all,
I got an idea why noise is having a gaussian pdf but didnot understood why it should be having zero mean. Why can't noise contain a dc content.

-Devanand T
 
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in most cases we consider 0 mean awgn , is it so...
 
dexterdev said:
Why can't noise contain a dc content.

DC component means that there is energy (power) permanently leaving the source, i.e. the source is "evaporating" so it would eventually seize to exist.
 
FailedLaunch said:
DC component means that there is energy (power) permanently leaving the source, i.e. the source is "evaporating" so it would eventually seize to exist.

Can you explain in simple english (Iam not good in english). I didnot got the idea of evaporate and seize etc..
 
Taking it back

FailedLaunch said:
DC component means that there is energy (power) permanently leaving the source, i.e. the source is "evaporating" so it would eventually seize to exist.
Actually, it looks like I'll need to take this explanation back since it doesn't appear to be to right reason while the used AWGN is zero-mean. :rolleyes:

Check also this thread: [thread=163759]White noise in communication channel[/thread]
 
dexterdev said:
Hi all,
I got an idea why noise is having a gaussian pdf but didnot understood why it should be having zero mean. Why can't noise contain a dc content.

-Devanand T

Your question is quite a reasonable one. It is largely a matter of semantics and practicalities, I think. In all analogue equipment, you can expect very low rate drifting of DC levels and these will mostly be due to other effects (due to thermal variations of gain etc.) than the normal Gaussian Noise that you can also expect. Most analogue channels are deliberately made 'AC' coupled so there is a lower frequency limit, below which we are not particularly interested and it is not very relevant, in any case. Also, if you think of noise power in W/Hz, there is very little of it in a small fraction of a Hz, compared with normal signalling rates.
 
Thankyou for your helpful replies. but what does "matter of semantics" mean
 
dexterdev said:
Thankyou for your helpful replies. but what does "matter of semantics" mean

It refers to the meaning we attribute to words. We make 'assumptions' when we read some words but different people make different assumptions. Mostly, we take it for granted that channels are AC coupled because DC is too difficult. (I can't think of an example, in fact. Now that's a challenge for you all.)
 
thanks again sir
 

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