Mitigation of channel errors in EFR-based speech recognition

Network-based speech recognition (NSR) using the conventional speech channel with the enhanced full rate (EFR) or the adaptive multi-rate (AMR) codec is a very attractive approach since no change to existing mobile phones is needed. However, NSR reveals a degrading performance due to both transmission channel errors and the speech encoding process in comparison with distributed speech recognition (DSR), where speech features are efficiently coded and transmitted on a data channel. We focus on the degradation of the speech features caused by channel errors in an NSR system and propose methods to improve the quality of these features. Applying these methods, it turns out that the performance of an NSR system based on EFR coding is comparable to that based on DSR.