function cost_update( t, vnum)
%
% update Viterbi cost function
%
% R. Perry, June 2001
%
% disp(sprintf( '\ncost_update: t = %g, vnum = %g\n', t, vnum));

global TYPE;

if( TYPE == 1) % single-user, known/constant-channel

  % do nothing

elseif( TYPE == 2) % multi-user, known-channel

  % do nothing

elseif( TYPE == 22) % multi-user, separate independent trellises

  % do nothing

elseif( TYPE == 23) % multi-user, separate trellises

  % do nothing

elseif( TYPE == 24) % multi-user, separate trellises

  % do nothing

else

  error( 'get_cost: unknown TYPE');

end
