cubic_estimation.m

通过图形实现OFMD的图像仿真

function [channel_estimation]=cubic_estimation(channel_post_ti)

frame_symbol=68;
row_begin=3;
row_end=frame_symbol-3;

fft_length=1705;                %for 2k mode
pilot_n=(fft_length-1)/3+1;

channel_estimation=channel_post_ti;

derivative=zeros(1,pilot_n);
coefficient=zeros(4,pilot_n);

for count_sn=row_begin:row_end
    %%%%%%%%%%%%%%%%%%%%%%%%%%derivative generation
    for count_pilot=2:(pilot_n-1)
        count_subch=count_pilot*3-2;
        previous=channel_estimation(count_sn, count_subch-3);
        current=channel_estimation(count_sn, count_subch);
        next=channetl_estimation(count_sn, count_subch+3);
        derivative(count_pilot)=((next-current)/3+(current-previous)/3)/2;
        
    end
    current=next;
    next=channel_estimation(count_sn, count_subch+6);
    derivative(pilot_n)=(next-current)/3*3/2-derivative(pilot_n-1);
    
    previous=channel_estimation(count_sn, 1);
    current=channel_estimation(count_sn, 4);
    derivative(1)=(current-previous)/3*3/2-derivative(2)/2;
    %%%%%%%%%%%%%%%%%%%%%%%%%
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%coefficient generation
    for count_pilot=1:pilot_n
        count_subch=count_pilot*3-2;
        coefficient(1,pilot_n)=channel_estimation(count_sn, count_subch);
    end
    coefficient(2,:)=derivative;
    for count_pilot=1:(pilot_n-1)
       d2=coefficient(2,count_pilot+1)-coefficient(2,count_pilot);
       s2=coefficient(2,count_pilot+1)+coefficient(2,count_pilot);
       d1=coefficient(1,count_pilot+1)-coefficient(1,count_pilot);
       s1=coefficient(1,count_pilot+1)+coefficient(1,count_pilot);
       coefficient(3,count_pilot)=(d2+6*d1)/6-3/2*s1;
       coefficient(4,count_pilot)=2*d1/27+s2/9;
    end
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
    %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%cubic estimation
    for count_pilot=1:(pilot_n-2)
        count_subch=count_pilot*3-2;
        c1=coefficient(1,pilot_n);
        c2=coefficient(2,pilot_n);
        c3=coefficient(3,pilot_n);
        c4=coefficient(4,pilot_n);
        channel_estimation(count_sn, count_subch+1)=c1+c2+c3+c4;
        channel_estimation(count_sn, count_subch+2)=c1+2*c2+4*c3+8*c4;
        
    end
    
end