Error on BER vs SNR for ACO-OFDM when apply zero clipping

Could anyone help me how to rectify this problem as I facing a difficulties in generating a correct out of BEr vs SNR for ACO-OFDM program as the graph plotted in linear line. The ACO-OFDM program as follows:

N = 20; % Number of rows in the array

m = 10; % Number of columns in the array

M = 64; %constellation size --> M=4/8/16/32/64/128/256

Ncp=5;

%Generation of random bits matrix of size m x N

Data_new = randi([0 1],m,N);

Data_ACO = Data_new;

%ACO-OFDM Principle (Only apply on odd sc

for x=1:m %m=row

for y=1:N %N=column

if mod(y,2)==0 %perform modulas operator to find even sc

Data_ACO(x,y)=0;%set even sc to 0

end

end

end

disp(Data_ACO);

%Performing data modulation

DataQAM_ACO = qammod(Data_ACO, M);

disp(DataQAM_ACO);

DataMat_ACO = DataQAM_ACO.';

%Apply HS on N-Sc

DataMat_ACO(1,:)=0;

DataMat_ACO(11,:)=0;

DataMat_ACO(12:20 , :)=flipud(conj (DataMat_ACO (2:10,:)));

%IFFT computational

ACO_IFFT = ifft(DataMat_ACO);

ACO_IFFT_P2S = ACO_IFFT2.';

%Zero Clipping

ZeroClip_ACO=ACO_IFFT_P2S;

for row=1:m

for col=1:N

if(ACO_IFFT_P2S(row,col)<0)

ZeroClip_ACO(row,col)=0;

end

end

end

P_Part_ACO = ZeroClip_ACO(:,end - Ncp + 1:end);

CP_ACO = [CP_Part_ACO ZeroClip_ACO];

%--------------------------------------------------------------------------------------

% Optical Channel

%-------------------------------------------------------------------------------------

count=0;

snr_vector=0:1:18;

for snr=snr_vector

SNR_ACOOFDM = snr + 10 * log10 (log2 (M));

count=count + 1;

ACO_OFDM_Channel = awgn(CP_ACO, SNR_ACOOFDM, 'measured'); %add AWGN

ACO_CP_removal = ACO_OFDM_Channel(:,Ncp+1:N+Ncp);

ACO_Rx_S2P = ACO_CP_removal.';

%FFT computational (TD - FD)

ACO_Rx_FFT = fft(ACO_Rx_S2P);

ACO_Rx_P2S = ACO_Rx_FFT.';

%QAM Demodulation

ACO_Demod = qamdemod(ACO_Rx_P2S, M);

[~,bit_errorACO(count)] = biterr (Data_ACO(:,2:10), ACO_Demod(:,2:10));

end

Thanks in advanced.

Answer 1

[Neelanshu]

Hello Norzalina,

I understand that you're looking to create a graph of BER vs. SNR for ACO-OFDM program, as illustrated in the image you've provided.

I noticed a few typographical errors in the variable names within the code you shared:

• In the IFFT computation, the variable should be 'ACO_IFFT' instead of 'ACO_IFFT2' when calculating 'ACO_IFFT_P2S'. Here is the corrected segment:

% IFFT computation

ACO_IFFT = ifft(DataMat_ACO);

ACO_IFFT_P2S = ACO_IFFT.'; % corrected 'ACO_IFFT2' to 'ACO_IFFT'

• In the Zero Clipping section, the variable name should be 'CP_Part_ACO' rather than 'P_PART_ACO', as shown below:

% Zero Clipping

ZeroClip_ACO = ACO_IFFT_P2S;

for row = 1:m

for col = 1:N

if ACO_IFFT_P2S(row, col) < 0

ZeroClip_ACO(row, col) = 0;

end

end

end

CP_Part_ACO = ZeroClip_ACO(:, end - Ncp + 1:end); % corrected 'P_Part_ACO' to 'CP_Part_ACO'

CP_ACO = [CP_Part_ACO ZeroClip_ACO];

After implementing these changes, here is the resulting BER vs. SNR graph:

Hope this helps.