IMPLEMENTING VOCODER AND HF MODEM ALGORITHMS USING THE TMS320C31 DSP

This application report describes the implementation of a universal DSP module (UDM) to vocoders for a range of bit rates and to modems operating in the voice-band range. The UDM is based on the Texas Instruments (TI(TM)) TMS320C31 DSP.

Difficulties in vocoder design are examined as well as measurement results for the HF modem under simulated HF channel environments. The error correction coding is varied among several methods during the HF modem measurement.

A functional description of the DSP module is included. The design described in this project enables the system to support vocoders with a bit rate range of 1.2 to 32 kb/s and HF modems with a bit rate range of 1.2 to 4.8 kb/s. An effective method of linear prediction parameter evaluation is presented for the bit rate range of 1.2 to 4.8 kb/s.

Parallel HF modem functionality and experimental research results on HF channel characteristics are also presented. The HF channel is simulated in real time using the PC-plugged DSP module. The fast synchronization approach is applied to a real world signal with a large frequency offset. Various methods of coding are compared.

This document was part of the first European DSP Education and Research Conference that took place September 26 and 27, 1996 in Paris. For information on how TI encourages students from around the world to find innovative ways to use DSPs, see TI's World Wide Web site at www.ti.com.

*DISCLAIMER: This document was part of the DSP Solution Challenge 1995 European Team Papers. It may have been written by someone whose native language is not English. TI assumes no liability for the quality of writing and/or the accuracy of the information contained herein.

Go to the Engineering Design Center to locate information on other TI Semiconductor devices.

(c) Copyright 1998 Texas Instruments Incorporated. All rights reserved.
Trademarks, Important Notice!