Cyclic Spectrum (Spectral Correlation Function) of OFDM Signal

can anyone provide me some code to find cyclic spectrum of OFDM signal? i've try it using my code as seen below, when the input is noise only the output is noise. But when the input is OFDM Signal the output is still give me noise only. I want the output like this picture. thank you.

clc;
clear all;
close all;

%% Some signals
NS=100000;
x = sqrt(10).*(randn(NS,1)+1i*randn(NS,1));

%% calculate the FFT
P_paralel=reshape(x,100,1000);
P_fft=zeros(100,1000);
for k=1:1000
    P2=fft(P_paralel(:,k));
    P_fft(:,k)=P2;
end

%% calculate autocorrelation function
P_fft1=fftshift(P_fft,1);
P_paralel1=P_fft1';
P_tensor=zeros(100,100,1000);
for i=1:1000
    P1=P_fft1(:,i)*P_paralel1(i,:);
    P_tensor(:,:,i)=P1;
end
P_abs=abs(P_tensor);
P_mean=mean(P_abs,3);
figure(1)
surf(P_mean)