cutongbu.m

64路OFDM系统MATLAB仿真

function   [zhentou_zhongjian]=cutongbu(all)
%%                           粗同步               %%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
fujia=1;
kaishi=0;
jieshu=0;

for zhuanhuan_i=1:length(all)
    if (real(all(zhuanhuan_i))>=0 & imag(all(zhuanhuan_i))>=0)
        temp_all(zhuanhuan_i)=1+i;
    elseif (real(all(zhuanhuan_i))>=0 & imag(all(zhuanhuan_i))<0)
        temp_all(zhuanhuan_i)=1-i;
    elseif (real(all(zhuanhuan_i))<0 & imag(all(zhuanhuan_i))>=0)
        temp_all(zhuanhuan_i)=-1+i;
    else (real(all(zhuanhuan_i))<0 & imag(all(zhuanhuan_i))<0)
        temp_all(zhuanhuan_i)=-1-i;
    end
end 
% conj_all=conj(all);
conj_temp_all=conj(temp_all);

for guji=1:length(all)-15-16

window=temp_all(guji:guji+15);

window_xia=conj_temp_all(guji+16:guji+15+16);

power=sum(window.*conj(window));


% tongbuguji(guji)=sum(window.*window_xia)/power;
tongbuguji(guji)=sum(window.*window_xia);%%%%%%%%%%不归一化
tongbuguji_abs=abs(tongbuguji).*abs(tongbuguji);

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
if tongbuguji_abs(guji)>150 & fujia==1 ;%%%%%%%%%%%%%     权值范围 ，有待进一步改善，越小越容易出错，但是，越大对信噪比要求越高%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    kaishi=guji;  
    fujia=0;
end
if tongbuguji_abs(guji)<150 & fujia==0;
    jieshu=guji;
    fujia=1;  
end

if jieshu-kaishi>120;
    real_kaishi=kaishi;
    real_jieshu=jieshu;   
    zhentou_zhongjian=round((real_jieshu-real_kaishi)/2);
end

end
%  subplot(121);
% 
%   plot(1:900,tongbuguji_abs(1:900));
%   title('粗同步');
%%%%%%%%%%%%%%%%%%%%%%%%%%%% 缺点：帧头前20个符号以内的干扰峰值会被记入帧头。%%%%%%%%%%%%%%%%%%%%%
%%%%%%%%%%%%%%%%%%%%%%%%%%%% 优点： 可以识别出帧头内部凹谷，能排除其他位置干扰峰值%%%%%%%%%%%%%%%%%