casestudy2.m

midamble码的生成和基于midamble码的td-scdma信道估计

% 3GPP CHANNEL SIMULATION
%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
A=['B';'2';'A';'C';'4';'2';'0';'F';'7';'C';'8';'D';'E';'B';'F';'A';'6';'9';'5';'0';'5';'9';'8';'1';'B';'C';'D';'0';'2';'8';'C';'3'];
B=hex2dec(A);
C=dec2bin(B);
D=reshape(C,128,1);
m0=str2num(D);
for i=1:128
    if m0(i)==0
        m0(i)=-1;
    end
    m0(i)=j^i.*m0(i);
end
P=128;
Lm=144;
Kmax=16;
W=16;
im=Lm+(Kmax-1).*W;
for i=1:im
    if i<129
        m(i)=m0(i);
    elseif i>256
        m(i)=m0(i-2*P);
    else
        m(i)=m0(i-P);
    end
end
% here we let k=8
K=8;
if K>8
    W=8;
else
    W=16;
end
Lm=144;
for k=1:K
    for i=1:Lm
        g(i,k)=m(i+(Kmax-k).*W);
    end
end
%转置得8*144矩阵
g=g.';

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
% 使用3GPP channel model中的case II,Vehicular,6 of Paths
L=6;
% Relative Path Power (dB) 为 0,-1,-9,-10,-15,-20
p0=[0.0,-1.0,-9.0,-10.0,-15.0,-20.0];
% (dB)转换为十进制
for i=1:6
    p1(i)=10^(p0(i)./10);
end
% 归一化得pk 
p2=sum(p1);
for i=1:6
    pk(i)=p1(i)./p2;
end

%求pn
% round(x)取最接近x的整数;ceil(x)取大于x的最小整数;floor(x)取小于x的最大的整数
a=2510*(10^(-9));
B=1.28*(10^6);
W1=ceil(a.*B);
t=[0,310*(10^(-9)),710*(10^(-9)),1090*(10^(-9)),1730*(10^(-9)),2510*(10^(-9))];
pn=zeros(1,W1+1);%pn(1*5)
for i=1:6
    b(i)=t(i).*B;
    n(i)=floor(b(i));
    pn(n(i)+1)=pn(n(i)+1)+((n(i)+1)-t(i).*B).*pk(i);
    pn(n(i)+2)=pn(n(i)+2)+(t(i).*B-n(i)).*pk(i);
end

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%Cn,k - N(un,pn)
%生成瑞利信道
k=8;%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%此处可取k=1,2,4,8
%W1=4,W1+1=5
%对Cnk产生实部和虚部
Cnk=zeros(k,5);
for p=1:k
    for q=1:5
        x1=random('Normal',0,pn(q)/2,1,1);
        x2=random('Normal',0,pn(q)/2,1,1);
        Cnk(p,q)=x1+j*x2;
    end
end
%卷积,g144维，Cnk5维，卷积后e148维
e=zeros(1,148);
for a=1:k
    ek=conv(Cnk(a,:),g(a,:));
    e=e+ek;
end
%取后128个即可，128+16=144可消除midanble码对数据块的影响，做IFFT，h128维
e1=e(:,(W+1):(W+128));
m1=m(:,1:128);
h=ifft(fft(e1)./fft(m1));

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%估计值h与计算值h1对比，实部与虚部分别对比
%k=1,2,4,8时，W=16，应把5维h1也扩为16维，再变换为与h一样的(1*128)
%CAT(DIM,A,B) concatenates the arrays,CAT(2,A,B) is the same as [A,B]
d=zeros(k,11);
h1=cat(2,Cnk,d);
h1=h1.';
h1=reshape(h1,1,128);

subplot(2,2,1);
stem(1:W,real(h(:,1:W)));
subplot(2,2,3);
stem(1:W,real(h1(:,1:W)));
subplot(2,2,2);
stem(1:W,imag(h(:,1:W)));
subplot(2,2,4);
stem(1:W,imag(h1(:,1:W)));