How to make a gaussian channel in Matlab?

[bee]

can any one plz tell me how to make a gussian channel in matlab....i dont want to use the build in function awgn.

Waiting....

 

[amihomo]

AWGN ???

hi
since AWGN contains all frequencies in the signal bandwith , and its PSD is constant and equal in all frequencies , i.e PSD(f)=N0 . you only need to create the samples of gaussian random variable in your signal BW. In other words ,if B is the sinal bandwidth , define n=sigma*randn(B,1); and add it to the signal s :
r=s+n

the awgn function in Matlab simply does the same as above.

regards

 

[bee]

Re: AWGN ???

tx allot for ur help.

can u tell me what is sigma and why u have used it?

Waiting....

 

[amihomo]

Re: AWGN ???

hi

sigma is the standard deviation of the gaussian noise which is equal to the square root of the noise power :

to get a better view , let Eb be the energy of the transmitted signal bits, and signal to noise power ratio be SNR, then for a baseband system:


SNR=signal power/noise power= S/N=(Eb×Rb)/(N0/2 × Rb)=2×Eb/N0

where N0 is the power spectral density of the bandpass noise and Rb is the signal bit rate (≈signal bandwidth). hence ,


sigma= √N=sqrt(Rb×N0/2)

it's that simple


regards