how to add cyclic prefix..I want codings to add it

Cyclic prefix=15

[Walter Roberson]

I think we need more context.

[Janet]

i gave qpsk signal as input and then took ifft..now i should add cp of length 15

%Generate random data

len=128;

m=4;

msg1=randint(len,1,m);

msg2=randint(len,1,m);

% figure(1)

% stem(msg1);

% stem(msg2);

% grid on;

% xlabel('data points')

% ylabel('transmitted data phase representation')

% title('Transmitted Data "O"')

% QPSK modulation

qpsk_modulated_data1=pskmod(msg1,m);

qpsk_modulated_data2=pskmod(msg2,m);

% scatterplot(qpsk_modulated_data1);

% title('qpsk modulated transmitted data1');

% scatterplot(qpsk_modulated_data2);

% title('qpsk modulated transmitted data2');

%IFFT

x1=ifft(qpsk_modulated_data1);

x2=ifft(qpsk_modulated_data2);

[Dipsikha Roy]

could u finally added cyclic prefix?