2 pág.

# sm10_31

DisciplinaTeoria de Telecomunicações240 materiais370 seguidores
Pré-visualização1 página
```Problem 10.31 In this experiment, we simulate the performance of bipolar signalling in
additive white Gaussian noise but with root-raised-cosine pulse shaping. A Matlab script
is included in Appendix 7 for doing this. With this simulation:
(a) Compute the spectrum of the transmitted signal and compare to the theoretical. Also
compare to the transmit spectrum with rectangular pulse shaping
(b) Plot the eye diagram of the received signal under no noise conditions. Explain the
relationship of the eye opening to bit error rate performance.
(c) Confirm the theoretically predicted bit error rate for Eb/N0 from 0 to 10 dB.

Solution
(a) We compare the spectra by inserting the following statements prior to noise being
added to the signal
[P,F] = spectrum(S,256,0,Hanning(256),Fs);
plot(F,P(:,1));
midpt = floor(length(F)/2);
hold on, plot(F, abs([(1+cos(pi*F(1:midpt)))/2; 0*F(midpt+1:end)]),'g'), hold off
xlabel('Frequency'), ylabel('Spectrum')

The comparison plot is shown below.

0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
0
0.2
0.4
0.6
0.8
1
1.2
1.4
Frequency
S
pe
ct
ru
m

(b) To plot the eye diagram we eliminate the noise by setting Eb/N0 to a high value
Eb_N0 = 2000;

Then running the Matlab script produces the following eye diagram.

Continued on next slide
Excerpts from this work may be reproduced by instructors for distribution on a not-for-profit basis for testing or instructional purposes only
to students enrolled in courses for which the textbook has been adopted. Any other reproduction or translation of this work beyond that
permitted by Sections 107 or 108 of the 1976 United States Copyright Act without the permission of the copyright owner is unlawful.
Problem 10.31 continued

-1 -0.8 -0.6 -0.4 -0.2 0 0.2 0.4 0.6 0.8 1
-1.5
-1
-0.5
0
0.5
1
1.5
Symbol periods
A
m
pl
itu
de

(c) We simulate the bit error rate by commenting out the plotting statements and adding a
set of statements similar to those used in Problem 10.30.

0 1 2 3 4 5 6 7 8 9 10
10-6
10-5
10-4
10-3
10-2
10-1
Eb/No (dB)
B
E
R
Theory
Simulation

Excerpts from this work may be reproduced by instructors for distribution on a not-for-profit basis for testing or instructional purposes only
to students enrolled in courses for which the textbook has been adopted. Any other reproduction or translation of this work beyond that
permitted by Sections 107 or 108 of the 1976 United States Copyright Act without the permission of the copyright owner is unlawful.```