www.gusucode.com > 基于VBLAST-OFDM的MATLAB SIMULATION，图形化界面，并且给出了各仿真图 > 基于VBLAST-OFDM的MATLAB SIMULATION，图形化界面，并且给出了各仿真图/vblast-ofdm simulation/tx_gen_preamble.m

    
function preamble = tx_gen_preamble(SimulationParameters);


global SimulationConstants;
M=SimulationParameters.M;
N=SimulationParameters.N;
fft_length=SimulationParameters.FFTPoints;

% generate the two long training symbols
long_tr = SimulationConstants.LongTrainingSymbols;
long_tr_symbol = tx_convert_to_time(long_tr,SimulationParameters);
	if ~SimulationParameters.TxDiv
  		 % single antenna preamble
  	 	% extend with the 2*guard interval in front and then two long training symbols 
  	 	long_trs_signal = [long_tr_symbol(fft_length-2*16+1:fft_length) long_tr_symbol long_tr_symbol];
    elseif SimulationParameters.TxDiv==2
   	% generate the two antenna preamble,
	   % long training symbols are not transmitted simultaneously from both antennas to allow
   	% channel estimation in receiver (orthogonal in time)
	   long_trs_signal(1,:) = sqrt(2)*[long_tr_symbol(fft_length-16+1:fft_length) long_tr_symbol ...
   	      zeros(1,(fft_length+16))];
	   long_trs_signal(2,:) = sqrt(2)*[zeros(1,(fft_length+16)) ...
   	      long_tr_symbol(fft_length-16+1:fft_length) long_tr_symbol];
    elseif SimulationParameters.TxDiv==4
       long_trs_signal(1,:) = sqrt(4)*[long_tr_symbol(fft_length-16+1:fft_length) long_tr_symbol ...
   	      zeros(1,(fft_length+16)) zeros(1,(fft_length+16)) zeros(1,(fft_length+16))];
	   long_trs_signal(2,:) = sqrt(4)*[zeros(1,(fft_length+16)) ...
   	      long_tr_symbol(fft_length-16+1:fft_length) long_tr_symbol ...
      zeros(1,(fft_length+16)) zeros(1,(fft_length+16))];
  	   long_trs_signal(3,:) = sqrt(4)*[zeros(1,(fft_length+16)) zeros(1,(fft_length+16)) ...
   	      long_tr_symbol(fft_length-16+1:fft_length) long_tr_symbol zeros(1,(fft_length+16))];
	   long_trs_signal(4,:) = sqrt(4)*[zeros(1,(fft_length+16)) zeros(1,(fft_length+16)) zeros(1,(fft_length+16)) ...
   	      long_tr_symbol(fft_length-16+1:fft_length) long_tr_symbol];

	end

	% concatenate first short training symbols and long training symbols
	preamble(1,:) = [long_trs_signal(1,:)];

	% add the second antenna preamble
	if SimulationParameters.TxDiv==2
   	preamble(2,:) = [long_trs_signal(2,:)];
    elseif SimulationParameters.TxDiv==4
   	preamble(2,:) = [long_trs_signal(2,:)];
    preamble(3,:) = [long_trs_signal(3,:)];
   	preamble(4,:) = [long_trs_signal(4,:)];
	end