OOV-detection and channel error protection for distributed speech recognition over wireless networks

This paper presents research on two aspects of distributed speech recognition (DSR) in the presence of channel transmission errors in wireless network environments. The first is on experiments with a frame-based channel error protection scheme, where in previous research we reported results from experiments using randomly distributed bit-errors. This paper presents results from experiments using three additional, more realistic error distributions: burst-like packet loss, GSM error patterns and UMTS statistics. The second is on exploiting the knowledge about channel transmission errors for the purpose of optimising the Out-of-Vocabulary (OOV) detection. Transmission errors influence the acoustic likelihood, and therefore affect the optimal threshold setting for discrimination between In-Vocabulary (IV) words and OOV words. An OOV-detection method is proposed in which the estimated Frame-Error-Rate (FER) is used to adjust the discrimination threshold. Results from experiments are reported over a range of transmission errors.