bpsk 调制解调的误码率Matlab仿真程序

bpsk 调制解调的误码率Matlab仿真程序 % ***********SIMULATION OF COEFFICIENTS OF RAYLEIGH FADING CHANNEL************ % % VEHICULAR SPEED, DOPPLER SHIFT % FADING COEFFICIENTS %********************************************************************** ******** Num_path=2000; % Number of paths t=0.0001:10/Num_path:10; % Time range f=150*10.^6; % Carrier frequency (150 Mhz, 900 Mhz) wc=2*pi*f; vehicle_speed=100; % Speed of car[km/hrs] v=vehicle_speed*5/18; % Receiver speed[m/hrs] c=300*10^3; % Speed of light wm=wc*(v/c); % Maximum shift fm=wm/(2*pi); % Doppler shift % SIMULATING ENSEMBLES OF SINUSOIDS for i=1:Num_path A(i)=(2*pi/Num_path)*i; %Azimuthal angles wn(i)=wm*cos(A(i)); phi(i)=(pi*i)/(Num_path+1); xc(i)=2*cos(wn(i)*t(i)).*cos(phi(i))+cos(wm*t(i)); xs(i)=2*cos(wn(i)*t(i)).*sin(phi(i)); T(i)=(1/(2*Num_path+1)^0.5).*(xc(i)+j*xs(i));% Complex envelope end; M=mean(abs(T)); % Mean MdB=20*log10(M); TdB=floor(20*log10(abs(T))); % Field [dB] % PLOTTING THE HISTOGRAM z1=hist(abs(T)); z=hist(TdB,9); n=0; for k=1:9 n=n+z(k); end for j=1:9 P(j)=z(j)/n; end f(1)=P(1); for x=2:9 f(x)=f(x-1)+P(x); F(10-x)=f(x); end plot(z1); % Distribution chart title('Rayleigh distribution'); semilogy(t,abs(T)/max(abs(T)),'r') % Fading graphic title('Received field'); ylabel('Received field intensity'); xlabel('time'); grid on; %*********************BINARY PHASE SHIFT KEYING ******************* % % Simulation of BPSK system in presence of Additive White Guassian Noise % and Rayleigh fading and Dopper shift and using SPREAD SPECTRUM TECH % %******************DIRECT SEQUENCE SPREAD SEQUENCE****************** clear all clc f_data=1; % DATA FREQUENCY f_chip=11; % LENGTH OF CHIP SEQUENCE fc=220; % RELATIVE CARRIER FREQUENCY fs=fc*3; % SAMPLING FREQUENCY N=fs/f_chip; % CODING RATE data_length=1000; M=2; % BINARY LEVEL CODING matches=0; errors=0; count=1; SNRpbit=0; SNR=SNRpbit; rand('state',12345); % INITIALISATION 'SEED' randn('state',54321); numplot=100; msg_unspread=randsrc(data_length,1,[0:M-1]); % GENERATION OF RANDOM DATA PN_sequence=randsrc(11,1,[0:1]); % GENERATION OF PN SEQUENCE % GENERATION OF SPREADED MESSAGE j=1; for i = 1:data_length for k = j:j+f_chip msg_orig(k) = msg_unspread(i); end; msg_orig(j:(j+f_chip-1)) = xor(msg_orig(j:(j+f_chip-1))',PN_sequence(1:f_chip)); j = f_chip*i+1; end; len_of_orig=length(msg_orig); % MODULATING THE SPREAD MESSAGE msg_tx=dmod(msg_orig,fc,f_chip,fs,'psk',M); len_of_tx=length(msg_tx); % % RAYLEIGH COEFFICIENTS % magT=abs(T); % % % ADDING RAYLEGH FADING COEFFICIENTS % k=1; % for i=1:len_of_tx % msg_tx(1,i)=msg_tx(1,i)*10*magT(1,k); % if(mod(i,k)) % k=k+300; % end ; % end; % PERFORMANCE ANALYSIS FOR VARYING SNR'S for SNRpbit=0:1:7 SNR=SNRpbit; rand('state',12345); randn('state',54321); % ADDING AWGN TO THE SIGNAL msg_rx_data=awgn(msg_tx,SNR-10*log10(N),'measured','dB'); % plot(t,msg_rx(1:length(t)),'b-'); msg_rx= msg_rx_data ; msg_rx=msg_tx; % DEMODULATING THE RECEIVED SIGNAL msg_demod=ddemod(msg_rx,fc,f_chip,fs,'psk',M); % CORRELATING WITH THE PN SEQUENCE j=1; for i = 1:data_length msg_demod(j:(j+f_chip-1)) = xor(msg_demod(j:(j+f_chip-1))',PN_sequence(1:f_chip)); j = f_chip*i+1; end; % DESPREADING THE RECEIVED SIGNAL j=1; for i = 1:data_length sum=0; for k = j:j+f_chip sum=sum+msg_demod(k); end; if (sum >=7) msg_demod_rec(i)=1; else msg_demod_rec(i)=0; end; j = f_chip*i+1; end; % CALCULATION OF ERRORS for i=1:data_length; if (msg_demod_rec(1,i)== msg_unspread(i,1)) matches=matches+1; else errors=errors+1; end ; end; % BER_ray(count)=errors/data_length; BER_awgn(count)=errors/data_length; %BER_theo(count)=0.07*erfc(SNR^0.5); count=count+1; errors=0; end;