REAL-TIME IMPLEMENTATION OF A COFDM MODEM FOR DATA TRANSMISSION OVER HF CHANNELS

This application report describes a transmission system with Orthogonal Frequency Division Multiplexing (OFDM) and Quadrature Phase Shift Keying (QPSK) over noisy multipath fading channels. When an encoder and a coherent receiver based on the maximum-likelihood estimation is added, we obtain the modulator-demodulator (COFDM MODEM) presented in this paper. The required performance was obtained thanks to specific research into channel estimation for the coherent demodulator and on frequency-shift correction.

A digital implementation of the MODEM is built around a Texas Instruments (TI(TM)) TMS320C31 Digital Signal Processor (DSP) and efficient special-purpose hardware for the encoder-decoder. Simulation results for this modem are given.

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.

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