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/* -*- c++ -*- */
/*
* Copyright 2002 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2, or (at your option)
* any later version.
*
* GNU Radio is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#include <math.h>
#include <atsci_single_viterbi.h>
#include <iostream>
using std::cerr;
using std::cout;
const float atsci_single_viterbi::was_sent[32] = {
-7,-3,-7,-3,-7,-3,-7,-3,
-5,-1,-5,-1,-5,-1,-5,-1,
1,5,1,5,1,5,1,5,
3,7,3,7,3,7,3,7
};
const int atsci_single_viterbi::transition_table[32] = {
0,2,4,6,
2,0,6,4,
1,3,5,7,
3,1,7,5,
4,6,0,2,
6,4,2,0,
5,7,1,3,
7,5,3,1
};
void
atsci_single_viterbi::reset()
{
for (unsigned int i = 0; i<2; i++)
for (unsigned int j = 0; j<8; j++) {
path_metrics[i][j] = 0;
traceback[i][j] = 0;
}
phase = 0;
}
atsci_single_viterbi::atsci_single_viterbi()
{
reset();
}
char
atsci_single_viterbi::decode(float input)
{
for (unsigned int next_state = 0; next_state < 8; next_state++) {
unsigned int index = next_state << 2;
int min_metric_symb = 0;
float min_metric = fabs(input - was_sent[index + 0]) +
path_metrics[phase][transition_table[index + 0]];
for (unsigned int symbol_sent = 1; symbol_sent < 4; symbol_sent++)
if( (fabs(input-was_sent[index+symbol_sent]) +
path_metrics[phase][transition_table[index+symbol_sent]])
< min_metric) {
min_metric = fabs(input-was_sent[index+symbol_sent]) +
path_metrics[phase][transition_table[index+symbol_sent]];
min_metric_symb = symbol_sent;
}
path_metrics[phase^1][next_state] = min_metric;
traceback[phase^1][next_state] = (((unsigned long long)min_metric_symb) << 62) |
(traceback[phase][transition_table[index+min_metric_symb]] >> 2);
}
unsigned int best_state = 0;
float best_state_metric = path_metrics[phase^1][0];
for (unsigned int state = 1; state < 8; state++)
if(path_metrics[phase^1][state] < best_state_metric) {
best_state = state;
best_state_metric = path_metrics[phase^1][state];
}
if(best_state_metric > 10000) {
for(unsigned int state = 0; state < 8; state++)
path_metrics[phase^1][state] -= best_state_metric;
// cerr << "Resetting Path Metrics from " << best_state_metric << " to 0\n";
}
phase ^= 1;
return (0x3 & traceback[phase][best_state]);
}
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