Efficient and robust distributed speech recognition (DSR) over wireless fading channels: 2D-DCT compression, iterative bit allocation, short BCH code and interleaving

In this paper, a new framework for distributed speech recognition (DSR) over wireless fading channels is proposed. A 2D-DCT based compression method and an iterative bit allocation algorithm are developed for source coding, while short BCH code integrated with interleaving is proposed for channel coding. The high correlation among speech feature parameters in the temporal domain is well exploited in the 2D-DCT based compression, and a carefully designed iterative bit allocation algorithm can very efficiently make use of every bit transmitted. The very low bit rate provides planning space for strong error control. Short BCH code integrated with interleaving is initially proposed to efficiently handle the severe bursty errors usually encountered in wireless fading channels. Overall system simulation based on a GPRS wireless channel simulator indicated significant recognition performance improvement is achievable at a bit rate of 3.4 kbit/s as compared to the conventional SVQ compression approach (with bit rate 4.4 or 4.8 kbit/s). The low computation requirements for all processes involved make it easy to implement them in the mobile telephone clients with existing technology.