syn_m1.m

DVB-T（2K模式）同步

% syn_m1.m

% Simulation program to see the correlated peak under AWGN channel

%********************** preparation part ***************************

clear;
para=2048;   % Number of parallel channel to transmit (points)
fftlen=2048; % FFT length
noc=2048;    % Number of carrier
nd=6;        % Number of information OFDM symbol for one loop
ml=4;        % Modulation level : 16QAM
sr=250000;   % Symbol rate
br=sr.*ml;   % Bit rate per carrier
gilen=64;    % Length of guard interval (points)
ebn0=7;      % Eb/N0
z=ebn0/(ebn0+1)/2;    % corelated factor of ML algorithm  
T=1:3*noc+2*gilen;    %length of FFT window removes


%************************** transmitter *********************************

%************************** Data generation **************************** 

seldata=rand(1,para*nd*ml)>0.5;  %  rand : built in function

%****************** Serial to parallel conversion ***********************

paradata=reshape(seldata,para,nd*ml); %  reshape : built in function

%************************** QPSK modulation ***************************** 

[ich,qch]=qpskmod(paradata,para,nd,ml);
kmod=1/sqrt(2); %  sqrt : built in function
ich1=ich.*kmod;
qch1=qch.*kmod;

%******************* IFFT ************************

x=ich1+qch1.*i;
y=ifft(x);      %  ifft : built in function
ich2=real(y);   %  real : built in function
qch2=imag(y);   %  imag : built in function

%********* Gurad interval insertion **********

[ich3,qch3]= giins(ich2,qch2,fftlen,gilen,nd);
fftlen2=fftlen+gilen;

%********* Attenuation Calculation *********

spow=sum(ich3.^2+qch3.^2)/nd./para;  %  sum : built in function
attn=0.5*spow*sr/br*10.^(-ebn0/10);
attn=sqrt(attn);

%***************************  Receiver  *****************************
%***************** AWGN addition ********* 

[ich4,qch4]=comb(ich3,qch3,attn);

%******************* quantization*******************************

ich5=sign(ich4);
qch5=sign(qch4);
r=ich5+qch5*i;

%**************************** ML estimation *******************************

    for ii=1:length(T);    % FFT窗移动的距离
    data1=r(ii:gilen+ii-1);     % 取gilen长个数据存data1
    data2=r(noc+ii:noc+gilen+ii-1);    % 取相距noc的gilen长个数据存data2
    s=data1*data2';    %求互相关值    
    cor(ii)=abs(s);    %  abs: built in function
    
%********************** 求能量项 **********************

    data11=abs(data1).^2;   
    data22=abs(data2).^2;
    data3=(data11+data22)*z;
    data33=sum(data3);     %  sum : built in function
    con(ii)=data33; 
    
%********************* 时间变量估计样本值 *************** 

    data4(ii)=cor(ii)-con(ii);
    
    end

 
%****************** plot ************************

plot(T,data4);

xlabel('载波数');ylabel('相关值');


%********** end of file ******************