How can i insert Cyclic prefix in an array?

N=1024; Cp=64; NTx=8;

% Constellation of Binary-Coded 16-QAM

C=[-3+3j, -3+1j, -3-3j, -3-1j, -1+3j, -1+1j, -1-3j, -1-1j,...
    3+3j, 3+1j, 3-3j, 3-1j, 1+3j, 1+1j, 1-3j, 1-1j];

% Generate random symbols
bk= randi ([0,15],NTx,N);

Dk=C(bk+1);

d=ifft(Dk).*sqrt(N);

tx=[d(end-Cp+1:end) d];

I have d is (8X1024) and I want to add Cyclic Prefix for each row, how can I do that?? [d(end-Cp+1:end) d]; this works for vectors only.

Answer 1

[Cedric]

 >> tx = [d(:,end-Cp+1:end) d] ; 
 >> size(tx)
 ans =
           8        1088

and

 >> tx = [zeros(size(d,1), Cp) d] ;

if you wanted zero padding.

[sharif]

Thanks for the answer :)

Answer 2

[Qaisar Hussain Alvi]

IFFT_Data = ifft(d,N);
txCy = [IFFT_Data(N-Ncp+1):N,:); IFFT_Data];

[Walter Roberson]

What is the purpose of doing an ifft() of something that was just calculated as an ifft ?

d=ifft(Dk).*sqrt(N);