syn_m2.m

在高斯与一径瑞利衰落信道下对DVB-T系统的同步算法进行仿真

%syn_m2.m
%高斯与1径瑞利衰落信道下正确符号定时的概率

% (under one path fading)

%********************** preparation part ***************************
clear;
para=2048;   % Number of parallel channel to transmit (points)
fftlen=2048; % FFT length
noc=2048;    % Number of carrier
nd=5;       % 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=0:4:20;    % Eb/N0


%******************* Fading initialization ********************
% If you use fading function "sefade", you can initialize all of parameters.
% Otherwise you can comment out the following initialization.

% Time resolution

tstp=1/sr/(fftlen+gilen); 

% Arrival time for each multipath normalized by tstp
% If you would like to simulate under one path fading model, you have only to set 
% direct wave.

itau = [0];

% Mean power for each multipath normalized by direct wave.
% If you would like to simulate under one path fading model, you have only to set 
% direct wave.
dlvl = [0.0];

% Number of waves to generate fading for each multipath.
% In normal case, more than six waves are needed to generate Rayleigh fading
n0=[6];

% Initial Phase of delayed wave
th1=[0.0];

% Number of fading counter to skip 
itnd0=nd*(fftlen+gilen)*10;

% Initial value of fading counter
% In this simulation one-path Rayleigh fading are considered.
% Therefore one fading counter are needed.
itnd1=[1000];

% Number of directwave + Number of delayed wave
% In this simulation one-path Rayleigh fading are considered
now1=1;        

% Maximum Doppler frequency [Hz]
% You can insert your favorite value
fd=320;       

% You can decide two mode to simulate fading by changing the variable flat
% flat     : flat fading or not 
% (1->flat (only amplitude is fluctuated),0->nomal(phase and amplitude are fluctutated)
flat =1;

%************************** main loop part **************************

for j=1:length(ebn0)
nloop=100;  % Number of simulation loops
noee=0;     % Number of error data
noe = 0;    % Number of error data
nod = 0;    % Number of transmitted data
nodd=0;     % Number of transmitted data
z(j)=ebn0(j)/(ebn0(j)+1)/2;  % corelated factor of ML algorithm

for iii=1:nloop

%************************** 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(j)/10);
attn=sqrt(attn);

%********************** Fading channel **********************

% Generated data are fed into a fading simulator
[ifade,qfade]=sefade(ich3,qch3,itau,dlvl,th1,n0,itnd1,now1,length(ich3),tstp,fd,flat);
  
% Updata fading counter
itnd1 = itnd1+ itnd0;

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

[ich4,qch4]=comb(ifade,qfade,attn);
[ich44,qch44]=comb(ich3,qch3,attn);

%***************received signal**********************

r=ich4+qch4*i;
rr=ich44+qch44*i;

%**************** ML estimation*******************************
 
for ii=1:noc;     % FFT窗口移动的距离
    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
    data11=rr(ii:gilen+ii-1);  
    data22=rr(noc+ii:noc+gilen+ii-1);
    s=data1*data2';     % 求互相关值    
    ss=data11*data22'; 
    cor(ii)=abs(s);     %  abs: built in function
    corr(ii)=abs(ss);
    
%************** 求能量项 ********************** 

    data3=abs(data1).^2;
    data4=abs(data2).^2;
    data33=abs(data11).^2;
    data44=abs(data22).^2;
    data5=(data3+data4)*z(j);
    data6=sum(data5);
    con(ii)=data6; 
    data55=(data33+data44)*z(j);
    data66=sum(data55);
    conn(ii)=data66; 
    
%************ ML时间变量估计 ********************

    data7(ii)=cor(ii)-con(ii);
    data77(ii)=corr(ii)-conn(ii);
    
end

   a=max(data7);   % 求最大值
   jest(iii)=find(data7==a);    % 求最大值所在位置
  
   aa=max(data77);
   jestt(iii)=find(data77==aa);
   
end

%******************* 粗符号正确定时的概率 *****************

A=ones(1,nloop);          % 产生nloop个全1数组
noe1=sum((jest-A)==0);    % 正确定时符号个数
nod1=nloop;               % 定时符号总个数
noee1=sum((jestt-A)==0);
nodd1=nloop;
noe=noe+noe1;
nod=nod+nod1;
noee=noee+noee1;
nodd=nodd+nodd1;
ser(j)=noe/nod;          %正确定时符号率
serr(j)=noee/nodd;

end

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

figure(1)
plot(ebn0,serr,'ro-');
hold on;
plot(ebn0,ser,'r*-');
hold on;
xlabel('信噪比/dB');ylabel('正确符号定时的概率');
legend('AWGN信道正确符号定时概率','Rayleigh信道正确符号定时概率');

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