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gr-satnogs
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Improve CW decoding process 

Our approach exploits the autocorrelation properties of the CW signal.
Thus low, high or band pass filtering greatly affects the performance of
the algorithm, because they introduce autocorrelation.
This commit is contained in:
Manolis Surligas 2017-09-05 01:37:47 +03:00
parent 52efa4c8bd
commit f560f16af3
3 changed files with 66 additions and 62 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

9
lib/cw_to_symbol_impl.cc
View File

@ -91,10 +91,10 @@ namespace gr
* a false alarm. As we use the window size for setting the history
* it should have a reasonably size.
*/
size_t i = 10;
size_t i = 1;
d_window_size = d_dot_samples / i;
while(d_window_size > 200) {
i += 10;
while(d_window_size > 256) {
i++;
d_window_size = d_dot_samples / i;
}
@ -103,6 +103,9 @@ namespace gr
d_window_size++;
}
LOG_DEBUG("Dot samples: %lu", d_dot_samples);
LOG_DEBUG("Window size: %lu", d_window_size);
/* Set the duration of each symbol in multiples of the window size */
d_dot_windows_num = d_dot_samples / d_window_size;
d_dash_windows_num = 3 * d_dot_windows_num;

10
lib/morse_decoder_impl.cc
View File

@ -41,7 +41,7 @@ namespace gr
void
morse_decoder_impl::symbol_msg_handler (pmt::pmt_t msg)
{
bool res;
bool res = false;
std::string str;
morse_symbol_t s;
s = (morse_symbol_t) pmt::to_long (msg);
@ -85,16 +85,14 @@ namespace gr
* If the decoding return false, it means that either an non decode-able
* character situation occurred or the maximum word limit reached
*/
if (!s) {
if (!res) {
if (d_morse_tree.get_max_word_len () == d_morse_tree.get_word_len ()) {
str = d_morse_tree.get_word ();
d_morse_tree.reset ();
std::cout << "Received word: " << str << std::endl;
message_port_pub (pmt::mp ("out"),
pmt::make_blob (str.c_str (), str.length ()));
}
}
else {
LOG_DEBUG("Something went wrong");
}
}
/*

109
lib/morse_tree.cc
View File

@ -2,7 +2,8 @@
/*
* gr-satnogs: SatNOGS GNU Radio Out-Of-Tree Module
*
* Copyright (C) 2016, Libre Space Foundation <http://librespacefoundation.org/>
* Copyright (C) 2016,2017
* Libre Space Foundation <http://librespacefoundation.org/>
*
* This program is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
@ -36,12 +37,12 @@ namespace gr
* Constructs a Morse code tree for Morse code decoding
*/
morse_tree::morse_tree () :
d_unrecognized_symbol('#'),
d_root (new tree_node(0)),
d_current (d_root),
d_buff_len(4096),
d_word_len(0),
d_word_buffer(new char[d_buff_len])
d_unrecognized_symbol ('#'),
d_root (new tree_node (0)),
d_current (d_root),
d_buff_len (4096),
d_word_len (0),
d_word_buffer (new char[d_buff_len])
{
construct_tree ();
}
@ -52,12 +53,12 @@ namespace gr
* in the place of unrecognized symbols
*/
morse_tree::morse_tree (char unrecognized) :
d_unrecognized_symbol(unrecognized),
d_root (new tree_node(0)),
d_current (d_root),
d_buff_len(4096),
d_word_len(0),
d_word_buffer(new char[d_buff_len])
d_unrecognized_symbol (unrecognized),
d_root (new tree_node (0)),
d_current (d_root),
d_buff_len (4096),
d_word_len (0),
d_word_buffer (new char[d_buff_len])
{
construct_tree ();
}
@ -200,46 +201,46 @@ namespace gr
bool ret = false;
/* Check for overflow */
if (d_word_len == d_buff_len) {
return false;
return false;
}
switch (s)
{
case MORSE_DOT:
if (d_current->get_left_child ()) {
d_current = d_current->get_left_child ();
ret = true;
}
break;
case MORSE_DASH:
if (d_current->get_right_child ()) {
d_current = d_current->get_right_child ();
ret = true;
}
break;
case MORSE_S_SPACE:
/*
* A short space received, but the decoder is still at the root.
* This is not in general an error so we return true
*/
if(d_current == d_root){
return true;
}
c = d_current->get_char ();
d_current = d_root;
/*
* Some nodes are null transitions and do not correspond to
* a specific character
*/
if (c != 0) {
d_word_buffer[d_word_len] = c;
d_word_len++;
ret = true;
}
break;
default:
LOG_ERROR("Unsupported Morse symbol");
return false;
}
{
case MORSE_DOT:
if (d_current->get_left_child ()) {
d_current = d_current->get_left_child ();
ret = true;
}
break;
case MORSE_DASH:
if (d_current->get_right_child ()) {
d_current = d_current->get_right_child ();
ret = true;
}
break;
case MORSE_S_SPACE:
/*
* A short space received, but the decoder is still at the root.
* This is not in general an error so we return true
*/
if (d_current == d_root) {
return true;
}
c = d_current->get_char ();
d_current = d_root;
/*
* Some nodes are null transitions and do not correspond to
* a specific character
*/
if (c != 0) {
d_word_buffer[d_word_len] = c;
d_word_len++;
ret = true;
}
break;
default:
LOG_ERROR("Unsupported Morse symbol");
return false;
}
return ret;
}
@ -265,7 +266,7 @@ namespace gr
morse_tree::delete_tree (tree_node *node)
{
if (!node) {
return;
return;
}
delete_tree (node->get_left_child ());
delete_tree (node->get_right_child ());
@ -273,7 +274,9 @@ namespace gr
}
tree_node::tree_node (char c) :
d_char (c), d_left (NULL), d_right (NULL)
d_char (c),
d_left (NULL),
d_right (NULL)
{
}