Real-Time Implementation of QCELP Vocoder for speech and data in CDMA Cellular System Using TMS320C50 Fixed Point DSP Chip

An variable rate QCELP speech coder was proposed for CDMA digital cellular system and QCELP algorithm has been chosen as the speech coder of digital cellular system in North America and Korea. In this paper, real-time implementation of variable rate QCELP speech coder algorithm (IS-96) is presented. Before programming by assembly code for real time operation, a fixed point simulation of QCELP coder is performed in order to find the the optimum data size and scaling factor. Thereafter a real-time implementation of the QCELP algorithm is achieved using a 16 bit fixed point TMS320C50 DSP Chip.. The QCELP codec implementation is evaluated in a DSP evaluation board and verified within our real CDMA digital cellular system for speech and data service.

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