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