function ofdm_sym = ofdm_trans(in_bits,n_point);


%this function is to do the ofdm ,
%   in_bits is the input v-blast symbols, in_bits is (m_transmitter * bits_len) array
%   n_point is the N-point IFFT

size_in = size(in_bits);
size_trans = size_in(1,1);  %   M-transmitter
size_len = size_in(1,2);    %   data length

antena_index_symbols(size_trans,n_point,size_len/n_point) = 0;

%   for every antena,  it need to do a series-parallel transformation
%   the 1st dimension stands for the first v-blast dimension
%   the 2nd dimension stands for the ith ofdm subchannel
%   the 3th dimension stands for the length of bits on each subchannel

for index = 1:size_trans
    antena_index_symbols(index,:,:) = series2paralle(in_bits(index,:), n_point);
    cur = squeeze(antena_index_symbols(index,:,:));         %   this is the ith channel OFDM data
    fren_time_trans_bits(index,:,:) = ifft(cur, n_point);   %   IFFT freq-time
    %cur2 = ifft(cur, n_point);
    %size(cur2)
    % the code below is added 21:33 13-12-2006
    %cur3 = parallel2series(cur2);
    %temp_bits(index,:) = parallel2series(cur2);     %   parallel-series transformation
end;
%save antena_index_symbols antena_index_symbols;     %   the symble after ofdm series-parallel 
ofdm_sym = fren_time_trans_bits;                    %   the symbols after ifft