Vector Sum Excited Linear Prediction
Wai C. Chu · 2003
In this chapter, the focus is placed on the study of the TIA IS54 coder. Like the FS1016, the IS54 utilizes the exact same principle of the adaptive codebook. Excitation vectors from the stochastic codebook, however, are obtained through linear combination of a number of fixed basis vectors—hence the name of vector sum excitation. The VSELP coder was designed to achieve the highest possible quality with reasonable computational complexity while providing robustness to channel errors, essential requirements for cellular telephony applications. The chapter begins with the core encoding structure of the VSELP coder, followed by the structure of the stochastic codebook and search methodologies. Gain quantization is explained next, followed by an analysis of the structure for the encoder and decoder. Performance of the coder and comparison among the various standards are also included.