sequence_spread.m

一段简单的扩频matlab 程序 加噪声与同频干扰

clear;
A = 3;
w0 = 1;
Lc = 20;
delay = [0,2,4,6];
amp = [1 1 0 0];
for snr_in_dB = 0:1:20   
snr = 10^(snr_in_dB/10);
sgma = 1;
Eb = 2*sgma^2*snr;
E_chip = Eb/Lc;
N = 10000;
num_of_err = 0;
for i = 1:N
    temp = rand;
    if(temp<0.5)
        data = -1;
    else
        data = 1;
    end
    for j = 1:Lc
    repeated_data(j) = data;
    end
    for j = 1:Lc
        temp =rand;
        if(temp<0.5)
            pn_seq(j) = -1;
        else
            pn_seq(j) = 1;
        end
    end
    trans_sig = sqrt(E_chip)*repeated_data.*pn_seq;
    Lc1 = Lc+max(delay);
    noise = sgma*randn(1,Lc1);
    n = (i-1)*Lc1 + 1:i*Lc1;
    interference = A*sin(w0*n);
 %多径信道%%
 [signal_out] = multi_path(trans_sig,delay,amp);
 trans_sig = signal_out;
 pn_seq1 = [pn_seq,zeros(1,max(delay))];
    %received signal%
    rec_sig = trans_sig + noise + interference;
    temp = rec_sig.* pn_seq1;
    decision_variable = sum(temp);
    % making decision
    if (decision_variable < 0)
        decision = -1;
    else
        decision = 1;
    end
    if(decision ~= data)
        num_of_err = num_of_err + 1;
    end
end
p(snr_in_dB +1) = num_of_err/N;
end
snr_in_dB = 0:1:20;
figure;
semilogy(snr_in_dB,p,'-*')
grid on;
% figure;
% plot(p,'*');