To directly specify the variance of the noise generated by AWGN Channel, specify the
Mode as:
Variance from mask
, where you specify the variance in
the dialog box. The value must be positive.
Variance from port
, where you provide the variance as
an input to the block. The variance input must be positive, and its sampling rate must
equal that of the input signal.
For Variance from mask
and Variance
from port
mode:
If the variance is a scalar, then all signal channels are uncorrelated but share
the same variance.
If the variance is a vector whose length is the number of channels in the input
signal, then each element represents the variance of the corresponding signal
channel.
Note
If you apply complex input signals to the AWGN Channel block, then it adds
complex zero-mean Gaussian noise with the calculated or specified variance. The
variance for each quadrature component of the complex noise is half of the
calculated or specified value.
To specify the variance indirectly, that is, to have the block calculate the variance,
specify the Mode as:
Signal to noise ratio (Eb/No)
, where the block
calculates the variance from these quantities that you specify in the dialog box:
Signal to noise ratio (Es/No)
, where the block
calculates the variance from these quantities that you specify in the dialog box:
Signal to noise ratio (SNR)
, where the block calculates
the variance from these quantities that you specify in the dialog box:
Changing the symbol period in the AWGN Channel block affects the variance of the noise
added per sample, which also causes a change in the final error rate.
Tip
Select the symbol period equal to the symbol period of the model. The value depends
on what constitutes a symbol and what the oversampling applied to it is. For example, a
symbol could have 3 bits and be oversampled by 4. For more information, see AWGN Channel Noise Level.