minn算法附matlab代码.zip

%********************schmidl algorithm******************* %*******************by:sk 2008-5-22********************** %Example: % If % X = rand(2,3,4); % then % d = size(X) returns d = [2 3 4] % [m1,m2,m3,m4] = size(X) returns m1 = 2, m2 = 3, m3 = 4, m4 = 1 % [m,n] = size(X) returns m = 2, n = 12 % m2 = size(X,2) returns m2 = 3 close all; clear all; clc; %参数定义 N=256; %FFT/IFFT 变换的点数或者子载波个数（Nu=N） Ng=N/8; %循环前缀的长度 (保护间隔的长度) Ns=Ng+N; %包括循环前缀的符号长度 loop=1000; %************利用查表法生成复随机序列********************** QAMTable=[7+7i,-7+7i,-7-7i,7-7i]; buf=QAMTable(randint(N/2,1,4)+1); %加1是为了下标可能是0不合法 %*************在奇数子载波的位置插入零*********************zj:是偶数吧？ deltaf=12.45; SNR=0:25; z=zeros(1,length(SNR)); SNR=0:25; for i=1:length(SNR) c=zeros(1,loop); g=zeros(1,loop); for ii=1:loop x=zeros(N/2,1); index = 1; for n=1:2:N/2 x(n)=buf(index); index=index+1; end; %**************利用IFFT变换生成Schmidl训练符号*************** sch = ifft(x); %[A A]的形式 sch2=[sch;(-1).*sch]; %*****************添加一个空符号以及一个后缀符号************* src = QAMTable(randint(N,1,4)+1).'; sym = ifft(src); sig =[zeros(N,1) sch2 sym]; %**********************添加循环前缀************************* tx =[sig(N - Ng +1:N,:);sig]; %***********************加时延******************************** recv = reshape(tx,1,size(tx,1)*size(tx,2)); for k=1:length(recv) recv(k)=recv(k)*exp(j*2*pi*deltaf*k/length(recv)); end %***********************经过信道*************************** %size的1表示行，2表示列，从%前向后数，超过了为1 recv1 = awgn(recv,SNR(i),'measured'); %recv2 = awgn(recv,5,'measured'); %recv3 = awgn(recv,10,'measured'); %*****************计算符号定时***************************** P=zeros(1,2*Ns); R=zeros(1,2*Ns); %P1=zeros(1,2*Ns); %R1=zeros(1,2*Ns); P2=zeros(1,2*Ns); R2=zeros(1,2*Ns); %P3=zeros(1,2*Ns); %R3=zeros(1,2*Ns); for d = Ns/2+1:1:2*Ns for k=1:2 for m=0:1:N/4-1 P(d-Ns/2) = P(d-Ns/2) + conj(recv1(d+m+(k-1)*N/2))*recv1(d+N/4+(k-1)*N/2+m); R(d-Ns/2) = R(d-Ns/2) + power(abs(recv1(d+N/4+(k-1)*N/2+m)),2); %P1(d-Ns/2) = P1(d-Ns/2) + conj(recv1(d+m))*recv1(d+N/2+m); %R1(d-Ns/2) = R1(d-Ns/2) + power(abs(recv1(d+N/2+m)),2); %P2(d-Ns/2) = P2(d-Ns/2) + conj(recv2(d+m))*recv2(d+N/2+m); %R2(d-Ns/2) = R2(d-Ns/2) + power(abs(recv2(d+N/2+m)),2); % P3(d-Ns/2) = P3(d-Ns/2) + conj(recv3(d+m))*recv3(d+N/2+m); % R3(d-Ns/2) = R3(d-Ns/2) + power(abs(recv3(d+N/2+m)),2); end end end M=power(abs(P),2)./power(abs(R),2); %M1=power(abs(P1),2)./power(abs(R1),2); %M2=power(abs(P2),2)./power(abs(R2),2); %M3=power(abs(P3),2)./power(abs(R3),2); [a b]=max(M); c(ii)=b; end for iii=1:loop g(iii)=power((c(iii)-177),2); end z(i)=min(g) end figure('Color','w'); SNR=0:5:25; semilogy(SNR,z(SNR+1),'-g*') axis([0,25,0.00001,1000]); xlabel('SNR(dB)');; ylabel('Mean of Timing Offset Estimation(sample'); grid on %**********************绘图****************************** %d=1:1:400; %plot(d,M(d)); %grid on; %axis([0,400,0,1.1]); %title('schmidl algorithm'); %xlabel('Time (sample)'); %ylabel('Timing Metric'); %legend('no noise','SNR=1dB','SNR=5dB','SNR=10dB');