function [BER]  = MIMO_OFDM_VBLAST_receiver(channel_est,tx_data_pilot,rx_data_pilot_frequency,MIMO_OFDM_system_par);
% ordered V-BLAST receiver
%
% Begin:  April 2007
% Last edited: Sept.3, 2007
%   Feng Wan    

num_frame_channel_inv=MIMO_OFDM_system_par.num_frame_channel_inv;
num_tx_antenna=MIMO_OFDM_system_par.num_tx_antenna;
num_rx_antenna=MIMO_OFDM_system_par.num_rx_antenna;

num_pilot=MIMO_OFDM_system_par.num_pilot;
num_carriers=MIMO_OFDM_system_par.num_carriers;
firstnum_pilot=MIMO_OFDM_system_par.firstnum_pilot;
interval_pilot=MIMO_OFDM_system_par.interval_pilot;
channel_length=MIMO_OFDM_system_par.channel_length;
pulse_type=MIMO_OFDM_system_par.pulse_type;



if(pulse_type==1)
    channel_length=MIMO_OFDM_system_par.channel_length_equivalent;  % when pulse type is enabled,
                                              % the channel_length_quivalent  is the true channel length
end

% %+++++++++++++++++++++++++++++++++++++
% % generate the channel matrix for different subcarriers
% %+++++++++++++++++++++++++++++++++++++
channel_est_frequency=zeros(num_rx_antenna,num_tx_antenna,num_carriers);



    for n2=1:num_rx_antenna
        for n3=1:num_tx_antenna
            vec_temp1=zeros(num_carriers,1);
            vec_temp2=zeros(channel_length,1);            
            for n4=1:size(channel_est,3)
                vec_temp1(n4)=channel_est(n2,n3,n4);
            end
            vec_freq_temp1=fft(vec_temp1);
            for n4=1:num_carriers
                channel_est_frequency(n2,n3,n4)=vec_freq_temp1(n4);
            end

        end
    end


BER_subcarrier=zeros(num_carriers,1);    
    
%%% LOOP : subcarriers
for n_subcarrier=1:num_carriers
%%% LOOP : subcarriers

% %%% begin test
% if(n_subcarrier==4)
%     disp('begin check!');
% end
% %%% end test
if(rem(n_subcarrier-firstnum_pilot,interval_pilot)~=0)

[BER]  = VBLAST_receiver(channel_est_frequency(:,:,n_subcarrier),rx_data_pilot_frequency(:,n_subcarrier),...
    tx_data_pilot(:,n_subcarrier),num_tx_antenna);
         
% %%% begin test
% temp_res=norm(rx_data_pilot_frequency(:,n_subcarrier)-channel_est_frequency(:,:,n_subcarrier)...
%     *tx_data_pilot(:,n_subcarrier));
% 
% 
% if(BER>0)
%     disp('maybe problem!');
% end
% 
% if(temp_res>1e-11)
%     disp('maybe problem!');
% end
%    
% %%% end test



BER_subcarrier(n_subcarrier)=BER;

end
%%% LOOP : subcarriers
end
%%% LOOP : subcarriers

BER=sum(BER_subcarrier)/(num_carriers-num_pilot);