[moved] OFDM Index modulation (code gives wrong result)

[syee]

can someone tell me what is wrong with my code, the result is incorrect
----------------------------------------------------------------------
place this code first on a different file first for the function

function table2=BPSKAA(table2)


table2=[[1;0;1;0],[1;0;-1;0],[-1;0;-1;0],[-1;0;1;0],[0;1;0;1],[0;1;0;-1],[0;-1;0;-1],[0;-1;0;1],[1;0;0;1],[1;0;0;-1],[-1;0;0;-1],[-1;0;0;1],[0;1;1;0],[0;1;-1;0],[0;-1;-1;0],[0;-1;1;0]];
end

------------------------------------------------------------------------

clc
clear all;
close all;
% rand('seed',183);   randn('seed',321);
  

 %% MODEULATION AND DEMODULATION OBJECT BPSK
 M = 2;
;
       Eac = 2;
  
  taps=10;
%%
      SNR = 0:2:40;               % signal-to-noise ratio in dB
       No = (Eac)*10.^(-SNR/10);  % noise variance
     L_SNR = length(SNR);         % length of SNR
       ber = zeros (L_SNR,1);     % initializating BER
       Result_table=zeros(4 ,128);
      %  bit_RL=zeros(L_SNR,1); 
      
 Nframe=10000;
  bit_RL=zeros(21,1); 
  ;
%digMod1=zeros(2 , length(digMod));
;
        % initializating BER
 
     ; 
%% ============================= Transmitter ===============================
 for iL=1:Nframe % sending 1000 frame
           
     
bit_T= randi([0 1],512,1);     % generate random bits
G_bits = reshape(bit_T,4,128);    % grouping bits into blocks
  
%% taking the first two rows for index modulation selection    
Index_selection=  [G_bits(1:2,:)].'; 

%% Doing BPSK modulation for third and fourth rows for G_bits
AW=reshape(G_bits(2+1:end,:),1,[]);
digMod1 = 2*(AW)-1;
digMod=reshape(digMod1,2,[]);

% digMod = 2*(G_bits(2+1:end,:))-1;



%% Create a block 4x128 to add result for BPSK modulation depending on sub carrier position 
  block = zeros(4 , length(digMod));
ab=  zeros(2 , 128);
% ML = zeros(1,16);
%% Chosing which sub carrier active in each colum  
 for i=1:length(Index_selection)
     
    
if Index_selection(i,1:end)==[0 0]
    sub_no(i,1:2)=[1,3];
elseif Index_selection(i,1:2)==[0 1]
    sub_no(i,1:2)=[2,4];
elseif Index_selection(i,1:2)==[1 0]
    sub_no(i,1:2)=[1,4];
elseif Index_selection(i,1:end)==[1 1]
    sub_no(i,1:2)=[2,3]; 
end
    
%% Adding the modulated signal on active carriers    
block(sub_no(i,1:2) , i)=digMod(1:2,i);
 end
 
transmitted_signa =block; % transmitted_signal
%% Pass the signal through IFFT 
 transmitted_signa1=reshape(transmitted_signa,512,1);

 IFFT_data = ifft(fftshift(transmitted_signa1.')).';
 a=max(max(abs(IFFT_data)));
 transmitted_signa_IFFT=IFFT_data./a; % normalization
 %% % transmitted sinal with IFFT
transmitted_signa_IFFT=reshape(transmitted_signa_IFFT,4,128);
%% Appending cylic prefix
% transmitted_signa_IFFT2 = [transmitted_signa_IFFT(:,[112128]) transmitted_signa_IFFT];
 

   transmitted_signa_IFFT=reshape(transmitted_signa_IFFT,512,1);
%% Calling a table for all posible position for BPSK modulation in INdex modaulation 
 table=BPSKAA;
%   for iL=1:Nframe
%% Creating a channel and receiver 
ber=[];
   for  ii  =1: L_SNR  
          % for pp = 1 :128
  %% Creating  channel  and noise 
   ch = sqrt(.5)*( randn(1,1,1) + 1i*randn(1,1,1));
% %   ch=sqrt(.5)*(randn(1,1)+j*randn(1,1));
% 
  noise = sqrt(.5)*(randn(1 , 1) + 1i*randn(1 , 1))* sqrt(No(ii));
% % noise =awgn(xt,SNR(ii),'measured');

  %% Passing signal through noise amd channel


        received_signal = ch.*transmitted_signa_IFFT;
%         received_signal=awgn(received_signal,SNR(ii));
 received_signal=awgn(received_signal,SNR(ii));

 %% removing cyclic prefix
%  received_signal = received_signal(:,[33:160]);
 
%% Applying FFT and normalize the signal
%  received_signal=reshape(received_signal,4,128);
received_signal1  = a.*fftshift(fft(received_signal.' )).'; 
 
received_signal2=reshape(received_signal1,4,128);
    for pp= 1 : 128
   %% Maximum Likelihood 
   
   
   ML = zeros(1,16);
   
A=received_signal2(:,pp);
B= repmat(A,[1,16]);
%  AAA=awgn(table,SNR(ii));
 
 ML= sum(abs( (B) - (ch.*table).^2));
% %       
%  
             [temp1 temp2] = min(ML);
       
                  KL(pp)=temp2;
%   
  %% finding which sub carrier active in each colum    
  if  (  KL(pp)>=1 &&   KL(pp)<=4)
    P_sub_B(pp,1:2)= [1,3];
    GET_INDEX_Selec(pp,1:2)=[0,0];
elseif (  KL(pp)>=5 &&   KL(pp)<=8)
     P_sub_B(pp,1:2)=[2,4];
     GET_INDEX_Selec(pp,1:2)=[0,1];
elseif  (  KL(pp)>=9 &&   KL(pp)<=12)
     P_sub_B(pp,1:2)=[1,4];
     GET_INDEX_Selec(pp,1:2)=[1,0];
elseif (  KL(pp)>=13 &&   KL(pp)<=16)
     P_sub_B(pp,1:2)=[2,3];
     GET_INDEX_Selec(pp,1:2)=[1,1];
    
  end
 AC_subcarrier=P_sub_B;
 %%chosing the two colum for the postion os subcarrier
 
 %% Demodulate the transmiited_signal using the  Index selection bits you detected in receiver after you chose for the first colum
   
    ab(1:2,pp)= (transmitted_signa(AC_subcarrier(pp,1:2),pp));
   % converting modulated values into 0 and 1
   bi_demod(1:2,pp) = ( (ab(1:2,pp))+1)/2 ;   
%     bi_demod(1:2,pp) = ( (ab(1:2,pp))+1)/2 ;  
%    bi_demod(1:2,pp)=demodulate(modem.pskdemod(2),ab(1:2,pp));
% % %   
 %% Creating a Result_table 4x128 after you detected the INdex selection bits and demodulated signal bits 
% % %  
     GET_INDEX_Selec1=GET_INDEX_Selec(pp,1:2).';
      bi_demod1= bi_demod(1:2,pp);
      
  
 %% Creating a Result_table 4x128 after you detected the INdex selection bits and demodulated signal bits 
  Result_table(:,pp)=[   GET_INDEX_Selec1;  bi_demod1];
     

   end
      
bit_R=reshape( floor(Result_table),512,1);
 [~,ber(ii,1)] = biterr(bit_T(:,1),bit_R(:));
% [number,ratio(ii,1)] = symerr(bit_T(:,1),bit_R(:),'row-wise');
   end
  


   
bit_RL= bit_RL+ ber;



%% Adding the previous ber for thw previous frame with the next frame after it
    
% % % 
 end
 bit_RL=bit_RL/Nframe;

 

[pythonista]

Perhaps, the following Python implementation would help your understanding.

https://ishikawa.cc/imtoolkit/tutorial/CoherentOFDM-IdealRayleigh-BER.html