function z=mapping(y,N_RB,N_Cell_ID)
k_=(12/2)*(mod(N_Cell_ID,2*N_RB));
k(1)=k_;
k(2)=mod(k_+floor(N_RB/2)*12/2,N_RB*12);
k(3)=mod(k_+floor(2*N_RB/2)*12/2,N_RB*12);
k(4)=mod(k_+floor(3*N_RB/2)*12/2,N_RB*12);
%四聯復值映射發生在每個下行子幀的第一個OFDM符號里
j = 1;
for i=1:4
    Pos(i) =k(i) + pos(i);
    pos = [0,1,2,3];
    z(Pos(1),1)=y(j,1);
    PCFICH_mappingid(Pos(1),1)=1;
    z(Pos(2),1)=y(j+1,1);
    PCFICH_mappingid(Pos(2),1)=3;
    z(Pos(3),1)=y(j+2,1);
    PCFICH_mappingid(Pos(3),1)=4;
    z(Pos(4),1)=y(j+3,1);
    PCFICH_mappingid(Pos(4),1)=6;
    j = j + 4;
end