rs_encoder_154a.m

source Matlab traites the UWB

%
% function tx_bit = rs_encoder_154a(data,DATALENGTH,interleaver_seed)
%
function tx_bit = rs_encoder_154a(data,DATALENGTH,interleaver_seed)

% RS encoding parameters
% We are in GF(2^6)
m = 6;
% Codeword length and message length
k = 55;
n = k+8;
% Note: rsgenpoly(n,k) and rsgenpoly(n,k,67) are the same

nblock = ceil(DATALENGTH/330);
fprintf('[RS encoder] Number of blocks = %d\n',nblock);

tx_bit = [];
for l = 1:nblock
  fprintf('[RS encoder] block = %d, (%d,%d)\n',...
          l,1+(l-1)*330,min(l*330,DATALENGTH));

  data_block = data(1+(l-1)*330:min(l*330,DATALENGTH));
  BLOCKLENGTH = length(data_block);
  fprintf('[RS encoder] BLOCKLENGTH = %d\n',BLOCKLENGTH);
  % Note: according to 15.4a, the maximum number of bit is 330. Hence, if
  % DATA_LENGTH < 330, pad zeros at the beginning
  if BLOCKLENGTH < 330
    fprintf('[RS encoder] zero padding\n');
    data_block = [zeros(1,330-BLOCKLENGTH) data_block];
  end
  % Conversion from bit to symbol in GF(2^6)
  data_block = permute(reshape(data_block,m,k),[2 1]);
  symbols = bi2de(data_block,'left-msb');

  % RS encoding
  enc_symbols = rsenc(gf(symbols',m),n,k);
  % Keep only what is necessary
  if BLOCKLENGTH < 330
    enc_symbols = enc_symbols(floor((330-BLOCKLENGTH)/m)+1:end);
  end
  % Convert back to bit
  tx_bit_block = de2bi(double(enc_symbols.x),m,'left-msb');
  tx_bit_block = reshape(permute(tx_bit_block,[2 1]),1,size(tx_bit_block,1)*m);

  tx_bit = [tx_bit tx_bit_block];
end

if ~isempty(interleaver_seed)
  fprintf('[RS encoder] interleaving\n');
  tx_bit = randintrlv(tx_bit,interleaver_seed);
end

return;