rllnd.m

rll(run length limited) code for channel simulate

%RLLnd(n,d)
%   This function returns the number of RLL codewords
%   with bit length 'n' adhering to a (d,inf) RLL
%   encoding system.  They do not necessarily hold when
%   concatenated.
%
%   The numbers produced with this function match the
%   table given in the Tang and Bahl paper.

function out = RLLnd(n,d)

dec = [0:2^n-1]';
bin = de2bi(dec);
good = ones(1,2^n)';

for i=1:2^n
    for j=1:(n-d)
        x = 0;
       for k = 0:d
           x = x + bin(i,(j+k));
       end
       if x > 1
           good(i,1) = 0;
       end
   end
end
            
totalwords = sum(good);

wordsparse = good .* dec;
worddense = find(wordsparse) - 1;
somecodes = de2bi(worddense);
somezeros = zeros(1,n);
allbackwards = [somezeros ; somecodes];
allwords = fliplr(allbackwards);

save codebook n d allwords totalwords;

out = totalwords;