1.問題描述：

?MRC誤碼率的matlab仿真

2.部分程序：

?

%Comparison of Decode and F,Detect and F and Amplify and Forward?
%BPSK in flat fading with WGN:?
%plot simulation results of BER and theoratical results for it.?
%combining the two signals using MRC?
%using averaged BER?

%%%%%%%%%house hold instuctions%%%%%%%%%%%%%%%%%%?
clc?
clear all?
close all?

sum_dcf = 0;?
sum_dtf = 0;?
sum_af = 0;?
%%%%%%%%%%%%%%%%%%%User1:Source%%%%%%%%%%%%%%?
N_bits = 15000; %Number of data bits?

%number of iterations over which the results are going to be averaged?
N_iter = 15;?
for iter = 1:N_iter?

data = round(rand(N_bits,1));%random data bits?
%channel coding using rate 1/2 convolutional code:?
trellis = poly2trellis(3,[5 7]); %trellis structure?
c_data = convenc(data,trellis);?

%BPSK modulation?
tx = 2*c_data - 1;?

%%%%%%%%%Channel characteristics%%%%%%%%%%%%%%%%?
SNRdB = -3:20; %Range of SNR for which BER is investigated.?

%additive noise and channel response for the relay channel:?
%Source uplink channel:?
noise_d = 1/sqrt(2) * (randn(2 * N_bits,1) + j * randn(2 * N_bits,1));?
h_d = 1/sqrt(2) * (randn(2 * N_bits,1) + j * randn(2 * N_bits,1));?

%interuser channel:?
noise_r1 = 1/sqrt(2) * (randn(2 * N_bits,1) + j * randn(2 * N_bits,1));?
h_r1 = 1/sqrt(2) * (randn(2 * N_bits,1) + j * randn(2 * N_bits,1));?

%for Relay uplink:?
noise_r2 = 1/sqrt(2) * (randn(2 * N_bits,1) + j * randn(2 * N_bits,1));?
h_r2 = 1/sqrt(2) * (randn(2 * N_bits,1) + j * randn(2 * N_bits,1));?

for k = 1:length(SNRdB)?

SNR = 10^(SNRdB(k)/10); %convert SNRdB to linear value SNR?

ftx_r1 = sqrt(SNR) * h_r1 .* tx + noise_r1;?

%%%%%%%%%%%%%%%%% At the Relay %%%%%%%%%%%%%?
%%%%%%%%%%%%%%%%%%%%%%%%%Decode n F%%%%%%?
%equalizing at relay?
eq_rx1 = ftx_r1 .* conj(h_r1);?
%hard decision and converting from bipolar to bits?
r_bits = (sign(real(eq_rx1)) + 1)/2;?
%channel decoding:?
dec_dcf_r1 = vitdec(r_bits,trellis,3,'term','hard');?
%re-encoding using the same procedure as Source:?
c_data2 = convenc(dec_dcf_r1,trellis);?
%BPSK signal for the relay coded data:?
tx2_dcf = 2 * c_data2 - 1;?
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%?

%%%%%%%%%%%%%%%%%%Detect n F%%%?

dec_dtf_r1 = sign(real(eq_rx1));?
tx2_dtf = dec_dtf_r1;?

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%Apmlify n F%%?

beta = sqrt(1./((SNR * abs(h_r1).^2) + 1));?
%amplification:?
ftx_amp = ftx_r1 .* beta;?

%%%%%%%%%%%%%%%%%%%%%%%%%%Relay to Destination%?
%DCF?
ftx_dcf_r2 = sqrt(SNR) * tx2_dcf .* h_r2 + noise_r2 ;?
%DTF?
ftx_dtf_r2 = sqrt(SNR) * tx2_dtf .* h_r2 + noise_r2 ;?
%AF?
ftx_af_r2 = sqrt(SNR) * ftx_amp .* h_r2 + noise_r2 ;?

%%%%%%%%%%%%%%%%% At the Destination%%%%%%%%%%%?
ftx_d = sqrt(SNR)* tx .* h_d + noise_d;?

%%%%%%%%%%%%%%%%%%%%%%%%DCF%%%%%%%%%%%?
%%%%%%%%%%%%%%%%%%%MRC%%%%%%%%%%%%%%%?
R_dcf = ftx_dcf_r2 .* conj(h_r2) + ftx_d .* conj(h_d);?
%hard decisioning?
dec_com_dcf = sign(real(R_dcf));?

%%%%%%%%%%%BER calculations%%%%%%%%%%%%%%%%%%?
%at destination:?
err_com1(k) = sum(abs(dec_com_dcf - tx)/2);?
simber_com1(k) = err_com1(k) / (2 * N_bits);?

%%%%%%%%%%%%%%%%%%%%%%%%DTF%%%%%%%%%%%?
%%%%%%%%%%%%%%%%%%%MRC%%%%%%%%%%%%%%%?
R_dtf = ftx_dtf_r2 .* conj(h_r2) + ftx_d .* conj(h_d);?
%hard decision?
dec_com_dtf = sign(real(R_dtf));?
%%%%%%%%%%%BER calculations%%%%%%%%%%%%%%%%%%?
%at destination:?
err_com2(k) = sum(abs(dec_com_dtf - tx)/2);?
simber_com2(k) = err_com2(k) / (2 * N_bits);?

%%%%%%%%%%%%%%%%%%%%%%%%AF%%%%%%%%%%%?
%%%%%%%%%%%%%%%%%%%MRC%%%%%%%%%%%%%%%?
R_af = ftx_af_r2 .* conj(h_r2) .* conj(h_r1) + ftx_d .* conj(h_d);?
dec_com_af = sign(real(R_af));?
%%%%%%%%%%%BER calculations%%%%%%%%%%%%%%%%%%?
%at destination:?
err_com3(k) = sum(abs(dec_com_af - tx)/2);?
simber_com3(k) = err_com3(k) / (2 * N_bits);?

theberawgn(k) = 0.5 * erfc (sqrt(SNR));%theoratical BER for AWGN?
theberrayleigh(k) = 0.5 * (1 - sqrt(SNR./(1 + SNR))); %theoratical rayleigh?

mue = sqrt(SNR/(1+SNR));?
mrcth(k) = 0.25 * (2 + mue) * (1-mue)^2;%theoratical 2Rx MRC?

end?

sum_dcf = sum_dcf + simber_com1;?
sum_dtf = sum_dtf + simber_com2;?
sum_af = sum_af + simber_com3;?
end?

%average BER:?
avgber_dcf = sum_dcf/N_iter;?
avgber_dtf = sum_dtf/N_iter;?
avgber_af = sum_af/N_iter;?

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%?
%%%%%%%%%BER plots%%%%%%%%%%%%%%%%%%%%%%%%%%?
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%?

figure?
semilogy(SNRdB,avgber_dcf,SNRdB,avgber_dtf,SNRdB,avgber_af,SNRdB,theberawgn,SNRdB,theberrayleigh,SNRdB,mrcth);?
axis([SNRdB(1) max(SNRdB) 10^-5 0.5]);?
grid on?
legend('DCF','DTF','AF','AWGN','Rayleigh','MRC 2 senders');?
xlabel('SNR dB');?
ylabel('BER');?
title(['BER curves for comparison,(averaged for ',num2str(N_iter),' iterations)']);?

3.仿真結論：

D69

?

總結

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