How do I apply a Gaussian pulse shaping filter on a random bit stream using Communications Toolbox?

I want to do a Gaussian pulse shaping of a binary signal.

Answer 1

[MathWorks Support Team]

The ability to apply a Gaussian pulse shaping filter on a signal is not available in Communications Toolbox.

As a workaround, you may use the GAUSSFIR function in the Signal Processing Toolbox. The following example demonstrates how this can be done.

%%Signal Source

% Build a set of test data.

x = randint(5,1);

x = x*2 -1;

rxsig = upsample(x,33); % Upsampled signal

rxsig = [zeros(16,1); rxsig];

stem(rxsig); hold on

%%Setup

% Define parameters.

bt = 0.3;

o=8;

n = 2;

%%Filter Definition

% Define filter-related parameters.

h = gaussfir(bt,n,o) ;

%%Filter the Signal

% y = filter(h,1,rxsig)/(h*h'); %Scaling by energy

y = filter(h,1,rxsig)/(max(h)); %Scaling by magnitude

plot(y(17:end, :), 'r');hold off;

legend('Upsampled Binary Signal','After Pulse Shaping')

%%Plot the impulse response of the Gaussian Filter

figure;impz(h);

Answer 2

[Tasos Giannoulis]

Alternatively, you can construct an FIR Gaussian filter using dsp.FIRFilter (from DSP System Toolbox) and gaussdesign (from Signal Processing Toolbox):

bt = 0.3;
span = 4;
sps = 4;
num = gaussdesign(bt, span, sps);
gaussianFilter = dsp.FIRFilter('Numerator', num);
filtered = gaussianFilter(yourSignal);