Title :
Estimation of unreliable packets in subband coding of speech (digital mobile radio)
Author :
Wong, W.C. ; Seshadri, N. ; Sundberg, C.-E.W.
Author_Institution :
Dept. of Electr. Eng., Nat. Univ. of Singapore, Singapore
Abstract :
A robust speech communications system over a digital mobile radio channel is considered. The authors examine a system using 12 kbit/s embedded subband coding of speech and rate compatible punctured convolutional (RCPC) codes with generalised Viterbi decoding for combined error detection and correction. System performance is improved by exploiting the frame-to-frame redundancy in the subband energy profile used for adaptive bit allocation in the subband coder. The subband side information deemed unreliable is replaced with the estimates based on frame-to-frame redundancy. This improved error detection capability in the subband side information allows a judicious reassignment of channel error protection bits to the subband main information, leading to an overall improvement in system performance. Using a realistic simulation model, an improvement of up to 4.4 dB in recovered speech segmental SNR is obtained at a channel SNR of 6 dB, compared with a system with only channel error protection.<>
Keywords :
digital radio systems; encoding; error correction codes; error detection codes; estimation theory; mobile radio systems; speech analysis and processing; RCPC codes; adaptive bit allocation; channel error protection bits; digital mobile radio channel; error correction; error detection; estimation; frame-to-frame redundancy; generalised Viterbi decoding; rate compatible punctured convolutional codes; recovered speech segmental SNR; signal to noise ratio; simulation model; speech coding; speech communications system; subband coder; subband coding;
Journal_Title :
Communications, Speech and Vision, IEE Proceedings I
