Combined source and channel coding using a sub-band coder

A dynamic-bit allocation subband coder and a rate-compatible punctured convolutional channel coder (RCPC) are described. The subband coder produces good communications-quality speech of bit rates as low as 12 kb/s. The coder also produces a prioritized bit stream which can easily be used for noisy channels. An analysis of the bit-error sensitivities revealed that not all of the bits in the bitstream require error protection, and among those that do, unequal error protection is called for. The RCPC channel coder is extremely flexible and capable of producing unequal error protection while using the same convolutional encoder and decoder for all bits. When matched to the speech-coder bitstream, a combined 16 kb/s coder was produced, which was demonstrated to give robust performance over even fairly noisy channels.<>