sfd_detection.m

一个UWB仿真程序包

function [sfd_index] = sfd_detection(rx_down,sfd_code,sfd_thld, ...
    fine_sync_index,channel_mask,G,CODE_ID,blocks_per_code_symbol,PLOT_DEBUG)

code_len = length(len31_preamble_code(CODE_ID));
samples_per_code = code_len * blocks_per_code_symbol;

%integrate over 31*16 samples ie one whole code. at the same time also
%apply the channel mask and the code.
rx_sfd_zero = zero_pad_reshape(rx_down(fine_sync_index+ ...
    G*samples_per_code:end),samples_per_code);
if(isempty(rx_sfd_zero))
  sfd_index = 0;
else
  rx_sfd_weighted = reshape(rx_sfd_zero,blocks_per_code_symbol, ...
    length(rx_sfd_zero)/blocks_per_code_symbol)'*channel_mask;
  rx_sfd_int = abs(len31_preamble_code(CODE_ID))* ...
    (reshape(rx_sfd_weighted,code_len,length(rx_sfd_weighted)/code_len));


  %create sfd_template
  sfd_templ = 2*abs(sfd_code)-1;
 
  sfd_corr = conv(rx_sfd_int,fliplr(sfd_templ));

%   if(PLOT_DEBUG)
%       figure
%       plot(sfd_corr(length(sfd_templ):end))
%       hold on
%       plot(sfd_thld * ones(1,length(sfd_corr)),'m')
%   end

  %find the first value in the correlation above the threshold
  sfd_ind_corr = find(sfd_corr(length(sfd_templ):end-(length(sfd_templ)-1))>=sfd_thld);

  if(isempty(sfd_ind_corr))
      sfd_index = 0;
  else
      sfd_index = samples_per_code*(sfd_ind_corr(1) - 1) + fine_sync_index+ ...
          G*samples_per_code;
  end
end
return;