www.pudn.com > layer1.rar > tonedemod.h
/*
*******************************************************************************
*
* COPYRIGHT (C) 2000 BY ERICSSON EUROLAB DEUTSCHLAND GmbH
* 90411 NUERNBERG, GERMANY, Tel Int + 49 911 5217 100
*
* The program(s) may be used and/or copied only with the
* written permission from Ericsson or in accordance
* with the terms and conditions stipulated in the agreement or
* contract under which the program(s) have been supplied.
*
*******************************************************************************
*
* File : tonedemod.h
* Purpose : Demodulator for the Cellular Text Telephone Modem
* 1-out-of-4 tones (400, 600, 800, 1000 Hz)
* for the coding of each pair of two adjacent bits
*
* Definition of the type demod_state_t and of the
* functions init_tonedemod() and tonedemod()
*
*******************************************************************************
*/
#ifndef tonedemod_h
#define tonedemod_h "$Id: $"
/*
*******************************************************************************
* INCLUDE FILES
*******************************************************************************
*/
#include "ctm_defines.h"
/*
*******************************************************************************
* DECLARATION OF PROTOTYPES
*******************************************************************************
*/
typedef struct {
WORD16 buffer_tone_rx[3*SYMB_LEN];
WORD16 xcorr_t0[2*SYMB_LEN];
WORD16 xcorr_t1[2*SYMB_LEN];
WORD16 xcorr_t2[2*SYMB_LEN];
WORD16 xcorr_t3[2*SYMB_LEN];
WORD16 xcorr_wb[2*SYMB_LEN];
WORD16 lowpass[SYMB_LEN];
WORD16 waveform_t0[SYMB_LEN];
WORD16 waveform_t1[SYMB_LEN];
WORD16 waveform_t2[SYMB_LEN];
WORD16 waveform_t3[SYMB_LEN];
WORD16 diff_smooth[SYMB_LEN];
} demod_state_t;
/* ----------------------------------------------------------------------- */
/* FUNCTION tonedemod() */
/* ******************** */
/* Tone Demodulator for the Cellular Text Telephone Modem */
/* using one out of four tones for coding two bits in parallel within a */
/* frame of 40 samples (5 ms). */
/* */
/* The function has to be called for every frame of 40 samples of the */
/* received tone sequence. However, in order to track a non-ideal */
/* of the transmitter's and the receiver's clock frequencies, one frame */
/* might be shorter (only 39 samples) or longer (41 samples). The */
/* of the following frame is indicated by the variable */
/* *sampling_correction, which is calculated and returned by this function.*/
/* */
/* input variables: */
/* bits_out contains the 39, 40 or 41 actual samples of the */
/* received tones; the bits are soft bits, i.e. they */
/* are in the range between -1.0 and 1.0, where the */
/* magnitude serves as reliability information */
/* num_in_samples number of valid samples in bits_out */
/* */
/* output variables: */
/* bits_out contains the two actual decoded soft bits */
/* sampling_correction is either -1, 0, or 1 and indicates whether the */
/* next frame shall contain 39, 40, or 41 samples */
/* demod_state contains all the memory of tonedemod. Must be */
/* initialized using the function init_tonedemod() */
/* ----------------------------------------------------------------------- */
void tonedemod(WORD16 *bits_out,
WORD16 *rx_tone_vec,
WORD16 num_in_samples,
WORD16 *ptr_sampling_correction,
demod_state_t *demod_state);
/* ----------------------------------------------------------------------- */
/* FUNCTION init_tonedemod() */
/* ************************* */
/* Initialization of one instance of the Tone Demodulator. The argument */
/* must contain a pointer to a variable of type demod_state_t, which */
/* contains all the memory of the tone demodulator. Each instance of */
/* tonedemod must have its own variable. */
/* ----------------------------------------------------------------------- */
void init_tonedemod(demod_state_t *demod_state);
#endif