[SOLVED] variance in time domain domain

[Romance42932]

hi...
i have calculated variance for a paricular SNR say 20dB for awgn noise ... so this variance will be in frequency domain....can anybody tell me how to find the equivalent time domain varaince so that i can find noise in time domain


...thanks in advance

 

[glen_campbells_dead]

If you're looking to create a time-domain noise signal with a particular SNR, use the awgn or wgn functions in MATLAB. You can specify the level of noise you want it on an existing signal using the awgn, or just create noise using the wgn function.

 

[zorro]

Hi Romance,

Can you explain better the problem?
SNR (when defined as a ratio of powers) is the same if calculated in time- or frequency- domain. Signal variance as well.
Regards

Z

 

[Romance42932]

hi zorro.. thanks for replying.....
actually i am doing LS and MMSE estimation for OFDM in matlab ... i wanna to plot MSE vs SNR plot..., after adding CP and then IDFT , i have to pass signal thru a channel...
i have defined channel impulse response as h = (pdp*randn(5,1)) where pdp = exp(-n/5) for n = 0:4..... channel tap is 5...
after convolution of channel and signali have to add noise into it and then remove CP and other all stuffs... i am using QPSK
... so variance of noise = (2/10^(snr/10)) for snr = 5:5:25 ..... this is in freq domain.... but i think we can add noise only in time domain...... so i want to find equivalent noise of that variance as calculated in freq domain...... i hope you get my problem