INFORME TAREA N1

SISTEMAS DE COMUNICACIONES PTICAS

POR:

JOHN JAIRO ARANGO QUINTERO

ID 000015263

PRESENTADO A:

NEIL GUERRERO

MAESTRA EN INGENIERA DE TELECOMUNICACIONES

UNIVERSIDAD PONTIFICIA BOLIVARIANA

MEDELLN

SEPTIEMBRE 24 DE 2010

ANLISIS DEL CDIGO EN MATLAB DE LA SIMULACIN N2 En las lneas 8 a 15 se realiza la definicin de variables.

8. Fs = 40e9; % sampling frequency

9. Fb = 1e9; % Bit rate

10. Fc = 5e9; % Carrier frequency

11. Fc1 = 10e9; % Carrier frequency

12. Fc2 = 15e9; % Carrier frequency

13. N_of_sym = 20000;

14. phase_Base = 0;%46*pi/180;

15. Noise_level = 8;

En las lneas 18 a 22 se lleva cabo la generacin de 3 mensajes aleatorios. 18. M = 8; % Alphabet size

19. x = randint(N_of_sym,1,M); %First PRBS

20. x1 = randint(N_of_sym,1,M); %Second PRBS

21. x2 = randint(N_of_sym,1,M); %Third PRBS

22. Nsamp = Fs/Fb;

En las lneas 26 a 29 se realiza la modulacin 8PSK. 26. %y=modulate(modem.qammod(M),x);

27. y = modulate(modem.pskmod(M),x);

28. y1 = modulate(modem.pskmod(M),x1);

29. y2 = modulate(modem.pskmod(M),x2);

En las lneas 33 a 35 se genera el pulso rectangular con sobre muestreo. 33. ypulse = rectpulse(y,Nsamp);

34. ypulse1 = rectpulse(y1,Nsamp);

35. ypulse2 = rectpulse(y2,Nsamp);

En las lneas 39 a 46 se implementa un filtro Gaussiano. Tambien se puede observar el diagrama de ojo de la seal transmitida 39. BT = .4; % 3-dB bandwidth-symbol time

40. OF = Nsamp/2; % Oversampling factor (i.e., number of samples

per symbol)

41. NT = 1; % 2 symbol periods to the filters peak.

42. h = gaussfir(BT,NT,OF);

43. %hfvt = fvtool(h,'impulse');

44. y_up = upsample(y,Nsamp);

45. ypulse_g = filter(h,1,y_up);

46. eyediagram(ypulse_g(1:2000),Nsamp*2); title('Transmission');

Diagrama de ojo creado en la lnea 46

En las lneas 50 a 52 se introduce ruido AWGN en el pulso Gaussiano. Tambin se puede apreciar el diagrama de ojo de la seal con ruido 50. ynoisy = awgn(ypulse,Noise_level,'measured');

51. ynoisy_g = awgn(ypulse_g,Noise_level,'measured');

52. eyediagram(ynoisy_g(1:2000),Nsamp*2); title('Noisy Signal');

Diagrama de ojo creado en la lnea 52

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Eye Diagram for In-Phase Signal

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Transmission

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Eye Diagram for In-Phase Signal

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Noisy Signal

En las lneas 56 a 60 se le implementa a la seal un filtro de acoplamiento en el receptor. Se puede apreciar tambin el diagrama de ojo de la seal en el receptor. 56. ypulse_rec_g = filter(h,1,ynoisy_g); 57. ypulse_rec_g = ypulse_rec_g(Nsamp/2+1:end-Nsamp/2); 58. eyediagram(ypulse_rec_g(1:2000),Nsamp*2); title('Receiver'); 59. % figure, stem(real(ynoisy_g(1:1000))); hold on; 60. % stem(real(ypulse_rec_g(1:1000)),'r'); hold off;

Diagrama de Ojo creado en la lnea 58

En las lneas 65 a 69 se hace muestreo en el receptor con el fin de sacar la constelacin de la seal en el receptor. 65. ydownsamp = intdump(ynoisy,Nsamp);

66. ydownsamp_g = intdump(ynoisy_g,Nsamp);

67. ydownsamp_rec_g = intdump(ypulse_rec_g,Nsamp);

68. scatterplot(ydownsamp); title('Constellation Diagram

Rectangular Pulse');

69. scatterplot(ydownsamp_rec_g,1,0,'r.'); title('Constellation

Diagram Rise Cosine Pulse with filter');

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Eye Diagram for In-Phase Signal

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Receiver

Diagrama de constelacin creado en la lnea 68

Diagrama de constelacin creado en la lnea 69

En las lneas 73 a 75 se hace la modulacin de la seal 8PSK con ruido. 73. z=demodulate(modem.pskdemod(M),ydownsamp);

74. z1=demodulate(modem.pskdemod(M),ydownsamp_rec_g);

75. z2=demodulate(modem.pskdemod(M),ydownsamp_g);

En las lneas 79 a 96 se calcula y se muestra en pantalla la rata de error de smbolo. 79. [num_rec,rt_rec]= symerr(x,z);

80. rt_rec = -1*log10(rt_rec);

81. [num_g_w,rt_g_w]= symerr(x(1:end-1),z1);

82. rt_g_w = -1*log10(rt_g_w);

83. [num_g_wo,rt_g_wo]= symerr(x,z2);

84. rt_g_wo = -1*log10(rt_g_wo);

87.disp('%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%')

88. disp(['Error Rate Rectangular: ' num2str(rt_rec)])

89. disp(['Error Rate Gaussian with Filter: ' num2str(rt_g_w)])

90. disp(['Error Rate Gaussian withot Filter: ' num2str(rt_g_wo)])

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Constellation Diagram Rectangular Pulse

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Constellation Diagram Rise Cosine Pulse with filter

91.disp('%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Error Rate Rectangular: Inf Error Rate Gaussian with Filter: Inf Error Rate Gaussian withot Filter: Inf %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Visualizacin en pantalla del error

En las lneas 96 a 135 se hace la modulacin IQ a las tres seales generadas. 96. %1. Primera RF

97. F = Fc/Fs;

98. t_c = 0:1:length(real(ypulse))-1;

99. In_phase = cos(2*pi*F.*t_c + phase_Base);

100. Quadrature = sin(2*pi*F.*t_c + phase_Base);

101. In_phase_np = cos(2*pi*F.*t_c);

102. Quadrature_np = sin(2*pi*F.*t_c);

103. % figure, plot(In_phase(1:100)); hold on;

104. % plot(real(ypulse(1:100)),'r');

105. IP_c = real(ypulse)'.*In_phase;

106. Q_c = imag(ypulse)'.*Quadrature;

107. RF_signal = IP_c + Q_c;

108. %figure, stem(RF_signal(1:100));

110. %1. Segunda RF

111. F1 = Fc1/Fs;

112. t_c = 0:1:length(real(ypulse))-1;

113. In_phase1 = cos(2*pi*F1.*t_c + phase_Base);

114. Quadrature1 = sin(2*pi*F1.*t_c + phase_Base);

115. In_phase1_np = cos(2*pi*F1.*t_c);

116. Quadrature1_np = sin(2*pi*F1.*t_c);

117. % figure, plot(In_phase1(1:100)); hold on;

118. % plot(real(ypulse(1:100)),'r');

110. IP_c1 = real(ypulse1)'.*In_phase1;

120. Q_c1 = imag(ypulse1)'.*Quadrature1;

121. RF_signal1 = IP_c1 + Q_c1;

122. %figure, stem(RF_signal(1:100));

124. %1. Tercera RF

125. F2 = Fc2/Fs;

126. t_c = 0:1:length(real(ypulse))-1;

127. In_phase2 = cos(2*pi*F2.*t_c + phase_Base);

128. Quadrature2 = sin(2*pi*F2.*t_c + phase_Base);

129. In_phase2_np = cos(2*pi*F2.*t_c);

130. Quadrature2_np = sin(2*pi*F2.*t_c);

131. % figure, plot(In_phase2(1:100)); hold on;

132. % plot(real(ypulse(1:100)),'r');

133. IP_c2 = real(ypulse2)'.*In_phase2;

134. Q_c2 = imag(ypulse2)'.*Quadrature2;

135. RF_signal2 = IP_c2 + Q_c2;

136. %figure, stem(RF_signal(1:100));

En las lneas 140 a 150 se saca el espectro de las tres seales generadas. 140. Fd=1;

141. Ei_u = RF_signal + RF_signal1 + RF_signal2; %% RF SIGNAL

142. Npoints_1 = length(RF_signal);

143. Ei_F = fftshift(fft(Ei_u));

144. Ei_Fa = abs(Ei_F)./length(Ei_F);

145. Frek_1 = ((-(Npoints_1)/2:((Npoints_1/2)-1))).*Fs/Npoints_1;

146. figure

147. plot(Frek_1/1e6,20*log10(Ei_Fa),'r');

148. xlabel('Frequency [MHz]')

149. ylabel('Power [dB]')

150. title('Power spectrum of RF received signal')

Espectro de potencia de la seal de RF en el receptor creado en la lnea 147

En la lnea 154 se introduce ruido AWGN a la seal generada en las lneas 140 a 150. 154. Ei_u = awgn(Ei_u,Noise_level,'measured');

En las lneas 159 a 161 se implementa en el receptor el oscilador local para poder hacer la demodulacin IQ. 159. %1 Local Oscillator 160. E_demod_BB = Ei_u.*In_phase_np; 161. E_demod_BB2 = Ei_u.*Quadrature_np;

En las lneas 163 a 169 se implementa un filtro pasa bajo para quitarle ruido a la seal. 163. %2 Low pass filter

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164. Wp = (Fb + 100e6)/(Fs/2); Ws = (Fb + 250e6)/(Fs/2); 165. Rp = 3; Rs = 35; 166. [n,Ws] = cheb2ord(Wp,Ws,Rp,Rs); 167. [bRec,aRec] = cheby2(n,Rs,Ws); 168. % figure, freqz(bRec,aRec,2048,Fs); 169. % title('Pasa bajos');

En las lneas 171 a 175 se implementa otro filtro para separar las seales generadas. 171. %3 Filtering 172. EBB1 = filter(bRec,aRec,E_demod_BB); 173. EBB2 = filter(bRec,aRec,E_demod_BB2); 174. EBB1 = EBB1 - mean(EBB1); 175. EBB2 = EBB2 - mean(EBB2);

En las lneas 177 a 188 se observa el espectro despus de hacer la modulacin IQ. 177. %4 Power Spectrum 178. Fd=1; 179. Ei_u = EBB1; 180. Npoints_1 = length(RF_signal); 181. Ei_F = fftshift(fft(Ei_u)); 182. Ei_Fa = abs(Ei_F)./length(Ei_F); 183. Frek_1 = ((-(Npoints_1)/2:((Npoints_1/2)-1))).*Fs/Npoints_1; 184. figure 185. plot(Frek_1/1e6,20*log10(Ei_Fa),'r'); 186. xlabel('Frequency [MHz]') 187. ylabel('Power [dB]') 188. title('Power spectrum of RF received signal after quadrature

demodulator').

Espectro de potencia de la seal de RF en el receptor luego de la demodulacin en cuadratura, creado en la lnea 185

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En las lneas 190 a 192 se ajusta el retardo de la seal demodulada. 190. %5 Adjusting the delay 191. EBB1 = EBB1(n+floor(n/2):end); 192. EBB2 = EBB2(n+floor(n/2):end);

En las lneas 194 a 198 se lleva a cabo el sobre muestreo. 194. %6 Downsampling 195. EBB1_downsamp = intdump(EBB1(1:5000*Nsamp),Nsamp); 196. EBB2_downsamp = intdump(EBB2(1:5000*Nsamp),Nsamp); 197. RF_signal_recovered = EBB1_downsamp + i.*EBB2_downsamp; 198. scatterplot(RF_signal_recovered); title('Constellation after

demodulation');

Diagrama de constelacin luego de la demodulacin, creado en la lnea 198

En las lneas 201 a 223 se realiza la demodulacin de cada una de las subportadoras empleando el formato PSK. 201. %%%% Demodulation first RF subcarrier 202. %RF_signal_received_dem =

demodulate(modem.pskdemod(M),RF_signal_recovered); 203. RF_signal_received_dem =

demodulate(modem.pskdemod(M),RF_signal_recovered); 204. xm = x(1:length(RF_signal_received_dem))'; 205. %Bits_rec = n_MSK_signal_regeneration(x); 206. [num_RF_received,rt_RF_received]= symerr(xm,RF_signal_received_dem); 207. %[num_RF_received_Bits,rt_RF_received_Bits]= symerr(Bits,Bits_rec); 208. rt_RF_received = -1*log10(rt_RF_received); 209. %rt_RF_received_Bits = -1*log10(rt_RF_received_Bits); 211. %%%% Demodulation second RF subcarrier 212. %RF_signal_received_dem =

demodulate(modem.pskdemod(M),RF_signal_recovered); 213. RF_signal_received_dem =

demodulate(modem.pskdemod(M),RF_signal_recovered); 214. xm1 = x1(1:length(RF_signal_received_dem))';

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215. [num_RF_received1,rt_RF_received1]=

symerr(xm1,RF_signal_received_dem); 216. rt_RF_received1 = -1*log10(rt_RF_received1); 218. %%%% Demodulation third RF subcarrier 219. %RF_signal_received_dem =

demodulate(modem.pskdemod(M),RF_signal_recovered); 220. RF_signal_received_dem =

demodulate(modem.pskdemod(M),RF_signal_recovered); 221. xm2 = x2(1:length(RF_signal_received_dem))'; 222. [num_RF_received2,rt_RF_received2]=

symerr(xm2,RF_signal_received_dem); 223. rt_RF_received2 = -1*log10(rt_RF_received2); 224. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

225.

226. disp('%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%')

227. disp(['Error Rate first RF detected without phase recovery: '

num2str(rt_RF_received)])

228. disp(['Error Rate second RF detected without phase recovery: '

num2str(rt_RF_received1)])

229. disp(['Error Rate third RF detected without phase recovery: '

num2str(rt_RF_received2)])

230. disp('%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%')

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%% Error Rate first RF detected without phase recovery: 2.4437 Error Rate second RF detected without phase recovery: 0.053057 Error Rate third RF detected without phase recovery: 0.057793 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

Visualizacin en pantalla del error