Welcome to EDAboard.com

Welcome to our site! EDAboard.com is an international Electronics Discussion Forum focused on EDA software, circuits, schematics, books, theory, papers, asic, pld, 8051, DSP, Network, RF, Analog Design, PCB, Service Manuals... and a whole lot more! To participate you need to register. Registration is free. Click here to register now.

Are gaussian distributed noise always white noises in awgn channel?

Status
Not open for further replies.

lordsathish

Full Member level 5
Joined
Feb 11, 2006
Messages
247
Helped
33
Reputation
66
Reaction score
3
Trophy points
1,298
Location
Asia
Activity points
2,698
In the awgn channel the noise added is gaussian as well as white noise...
my question is whether gaussian distributed noises are always white noise....?
is the vice versa is also correct...?
 

carpa

Member level 3
Joined
Nov 12, 2004
Messages
56
Helped
6
Reputation
12
Reaction score
3
Trophy points
1,288
Activity points
481
uncorrelated awgn

The answer is "NO". Distribution does not concern anything about time or frequency. Gaussion noise can have any power spectrum shape, and the very special one of it is white.
 

    lordsathish

    Points: 2
    Helpful Answer Positive Rating

lordsathish

Full Member level 5
Joined
Feb 11, 2006
Messages
247
Helped
33
Reputation
66
Reaction score
3
Trophy points
1,298
Location
Asia
Activity points
2,698
awgn channel wiki

Then how come one can make sure that the noise added is gaussian as well as white noise... suppose i do a awgn simulation in matlab without using the function awgn... randn function will generate gaussian noise but to make sure it is white noise...
 

farzad_m

Junior Member level 2
Joined
Sep 26, 2006
Messages
24
Helped
6
Reputation
12
Reaction score
1
Trophy points
1,283
Activity points
1,434
what is awgn channel

when we say that a process is white we just define its second moment,but by knowing that its gaussian some more information will be known such as mean,etc.

and about randn. it produce a white gaussian noise because its samples are uncorrelated and so its white,to produce a colored noise you should use a proper innovation filter which is applied to your white noise and its output will have your desired spectrum charactristics.
 

    lordsathish

    Points: 2
    Helpful Answer Positive Rating

lordsathish

Full Member level 5
Joined
Feb 11, 2006
Messages
247
Helped
33
Reputation
66
Reaction score
3
Trophy points
1,298
Location
Asia
Activity points
2,698
verilog awgn

actually my problem is to create a verilog model of the awgn channel... for my turbo decoder... so can any one give me idea how to generate this uncorrelated gaussian noise...i think generating this gaussian noise won be a problem... but how to make it uncorrelated so that it is white noise...?
 

toshine

Newbie level 4
Joined
Sep 4, 2007
Messages
7
Helped
4
Reputation
8
Reaction score
2
Trophy points
1,283
Activity points
1,359
where does awgn come from?

white noise means that when you take samples of the noise at different time, these samples are independent.

to draw white gaussian noise, there are several ways. u can try in google. a popular method is box-muller method.

pls see the following c program, which is implemented by the box-muller method.

float x1, x2, w, y1, y2;

do {
x1 = 2.0 * ranf() - 1.0;
x2 = 2.0 * ranf() - 1.0;
w = x1 * x1 + x2 * x2;
} while ( w >= 1.0 );

w = sqrt( (-2.0 * ln( w ) ) / w );
y1 = x1 * w;
y2 = x2 * w;
(https://www.taygeta.com/random/gaussian.html)

y1 and y2 are independent gaussian r.v.'s.

hope it helps.
 

    lordsathish

    Points: 2
    Helpful Answer Positive Rating

valipour.m

Newbie level 1
Joined
Nov 1, 2007
Messages
1
Helped
0
Reputation
0
Reaction score
0
Trophy points
1,281
Activity points
1,287
how to make awgn channel

"A random vector w is a white random vector if and only if its mean vector and autocorrelation matrix are the following:

Mean(w)=0;
E(wwH)=sigma^2*I

I. e., it is a zero mean random vector, and its autocorrelation matrix is a multiple of the identity matrix. " ( https://en.wikipedia.org/wiki/White_noise)

As you see the white noise is independent from the distortion of that random variable.
in other wird you could have a white signal with any distribution.
 

Status
Not open for further replies.

Part and Inventory Search

Welcome to EDABoard.com

Sponsor

Top