Second order cone programming (SOCP) relaxations for large margin HMMs in speech recognition

In this paper, we present a new fast optimization method to solve large margin estimation (LME) of continuous density hidden Markov models (CDHMMs) for speech recognition based on second order cone programming (SOCP). SOCP is a class of nonlinear convex optimization problems which can be solved very efficiently. In this work, we have formulated the LME of CDHMMs as an SOCP problem and proposed two improved tighter SOCP relaxation methods for LME. The new LME/SOCP methods have been evaluated in a connected digit string speech recognition task using the standard TIDIGITS database. Experimental results demonstrate efficiency and effectiveness of the proposed LME/SOCP methods in speech recognition.