In this paper, we propose two different language modeling approaches, namely skip trigram and across sentence boundary, to capture the long range dependencies. The skip trigram model is able to cover more predecessor words of the present word compared to the normal trigram while the same memory space is required. The across sentence boundary model uses the word distribution of the previous sentences to calculate the unigram probability which is applied as the emission probability in the word and the class model frameworks. Our experiments on the Penn Treebank show that each of our proposed models and also their combination significantly outperform the baseline for both the word and the class models and their linear interpolation. The linear interpolation of the word and the class models with the proposed skip trigram and across sentence boundary models achieves 118.4 perplexity while the best state-of-the-art language model has a perplexity of 137.2 on the same dataset.
Bibliographic reference. Momtazi, Saeedeh / Faubel, Friedrich / Klakow, Dietrich (2010): "Within and across sentence boundary language model", In INTERSPEECH-2010, 1800-1803.