Beside the word posteriors, we use language model scores and a word count as features for confusion network decoding.
for an M-way system combination that uses N LMs, a total of M+N+1 decoding parameters, including M-1 system weights, one rank smoothing factor, N language model weights, and one weight for the word count feature, are optimized using Powell's method (Brent, 1973) to maximize BLEU score on a development set 4 .