A 5600 bps vselp speech coder candidate for half-rate gsm

The bit rate for the speech and channel coder for the half-rate GSM channel is 11400 bps. A 5600 bps VSELF speech coder designed for this application is described. This speech coder is one of two candidates being considered by GSM channel for the half-rate channel. It employs a novel strategy for vector quantization of the reflection coefficients (rj), which combines high coding efficiency, low codebook search complexity, and low storage requirements. A computationally streamlined version of a zero-pole spectral noise weighting function is implemented. An adaptive pitch prefilter and an adaptive spectral postfilter are used to improve the speech coder's performance for both the tandemed and non tandemed cases.