512 lines
17 KiB
C
512 lines
17 KiB
C
/*
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* Copyright (C) 2010 DSD Author
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* GPG Key ID: 0x3F1D7FD0 (74EF 430D F7F2 0A48 FCE6 F630 FAA2 635D 3F1D 7FD0)
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*
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* Permission to use, copy, modify, and/or distribute this software for any
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* purpose with or without fee is hereby granted, provided that the above
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* copyright notice and this permission notice appear in all copies.
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*
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* THE SOFTWARE IS PROVIDED "AS IS" AND ISC DISCLAIMS ALL WARRANTIES WITH
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* REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY
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* AND FITNESS. IN NO EVENT SHALL ISC BE LIABLE FOR ANY SPECIAL, DIRECT,
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* INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM
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* LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE
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* OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
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* PERFORMANCE OF THIS SOFTWARE.
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*/
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#include "dsd.h"
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#include "p25p1_hdu.h"
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#include "p25p1_check_hdu.h"
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#include "p25p1_heuristics.h"
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int
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read_dibit (dsd_opts* opts, dsd_state* state, char* output, int* status_count, int* analog_signal, int* did_read_status)
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{
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int dibit;
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int status;
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if (*status_count == 35) {
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#ifdef TRACE_DSD
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char prev_prefix = state->debug_prefix;
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state->debug_prefix = 's';
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#endif
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// Status bits now
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status = getDibit (opts, state);
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// TODO: do something useful with the status bits...
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if (did_read_status != NULL) {
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*did_read_status = 1;
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}
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*status_count = 1;
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#ifdef TRACE_DSD
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state->debug_prefix = prev_prefix;
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#endif
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} else {
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if (did_read_status != NULL) {
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*did_read_status = 0;
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}
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(*status_count)++;
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}
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dibit = get_dibit_and_analog_signal (opts, state, analog_signal);
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output[0] = (1 & (dibit >> 1)); // bit 1
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output[1] = (1 & dibit); // bit 0
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return dibit;
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}
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void
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read_dibit_update_analog_data (dsd_opts* opts, dsd_state* state, char* output, unsigned int count, int* status_count,
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AnalogSignal* analog_signal_array, int* analog_signal_index)
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{
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unsigned int i;
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unsigned int debug_left, debug_right;
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for (i=0; i<count; i+=2)
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{
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// We read two bits on each call
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int analog_signal;
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int did_read_status;
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int dibit;
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dibit = read_dibit(opts, state, output + i, status_count, &analog_signal, &did_read_status);
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if (analog_signal_array != NULL)
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{
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// Fill up the AnalogSignal struct
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analog_signal_array[*analog_signal_index].value = analog_signal;
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analog_signal_array[*analog_signal_index].dibit = dibit;
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analog_signal_array[*analog_signal_index].sequence_broken = did_read_status;
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(*analog_signal_index)++;
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}
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}
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}
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void
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read_word (dsd_opts* opts, dsd_state* state, char* word, unsigned int length, int* status_count,
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AnalogSignal* analog_signal_array, int* analog_signal_index)
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{
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read_dibit_update_analog_data(opts, state, word, length, status_count, analog_signal_array, analog_signal_index);
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}
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void
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read_golay24_parity (dsd_opts* opts, dsd_state* state, char* parity, int* status_count,
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AnalogSignal* analog_signal_array, int* analog_signal_index)
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{
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read_dibit_update_analog_data(opts, state, parity, 12, status_count, analog_signal_array, analog_signal_index);
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}
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void
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read_hamm_parity (dsd_opts* opts, dsd_state* state, char* parity, int* status_count,
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AnalogSignal* analog_signal_array, int* analog_signal_index)
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{
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// Read 2 dibits = read 4 bits.
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read_dibit_update_analog_data(opts, state, parity, 4, status_count, analog_signal_array, analog_signal_index);
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}
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/**
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* Corrects a hex (6 bit) word using the Golay 24 FEC.
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*/
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static void
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correct_hex_word (dsd_state* state, char* hex, char* parity)
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{
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int fixed_errors;
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int irrecoverable_errors;
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irrecoverable_errors = check_and_fix_golay_24_6(hex, parity, &fixed_errors);
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state->debug_header_errors += fixed_errors;
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if (irrecoverable_errors != 0)
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{
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state->debug_header_critical_errors++;
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}
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}
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/**
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* Reads an hex word, its parity bits and attempts to error correct it using the Golay24 algorithm.
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*/
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static void
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read_and_correct_hex_word (dsd_opts* opts, dsd_state* state, char* hex, int* status_count,
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AnalogSignal* analog_signal_array, int* analog_signal_index)
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{
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char parity[12];
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// Read the hex word
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read_word (opts, state, hex, 6, status_count, analog_signal_array, analog_signal_index);
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// Read the parity
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read_golay24_parity (opts, state, parity, status_count, analog_signal_array, analog_signal_index);
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// Use the Golay24 FEC to correct it. This call modifies the content of hex to fix it, hopefully
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correct_hex_word (state, hex, parity);
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}
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/**
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* Uses the information from a corrected sequence of hex words to update the AnalogSignal data.
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* The proper Golay 24 parity is calculated from the corrected hex word so we can also fix the Golay parity
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* that we read originally from the signal.
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* \param corrected_hex_data Pointer to a sequence of hex words that has been error corrected and therefore
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* we trust it's correct. Typically this are hex words that has been decoded successfully using a
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* Reed-Solomon variant.
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* \param hex_count The number of hex words in the sequence.
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* \param analog_signal_array A pointer to the AnalogSignal information for the sequence of hex words.
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*/
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static void
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correct_golay_dibits_6(char* corrected_hex_data, int hex_count, AnalogSignal* analog_signal_array)
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{
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int i, j;
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int analog_signal_index;
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int dibit;
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char parity[12];
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analog_signal_index = 0;
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for (i=hex_count-1; i>=0; i--)
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{
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for (j=0; j<6; j+=2) // 3 iterations -> 3 dibits
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{
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// Given the bits, calculates the dibit
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dibit = (corrected_hex_data[i*6+j] << 1) | corrected_hex_data[i*6+j+1];
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// Now we know the dibit we should have read from the signal
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analog_signal_array[analog_signal_index].corrected_dibit = dibit;
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#ifdef HEURISTICS_DEBUG
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if (analog_signal_array[analog_signal_index].dibit != dibit)
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{
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printf("HDU data word corrected from %i to %i, analog value %i\n",
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analog_signal_array[analog_signal_index].dibit, dibit, analog_signal_array[analog_signal_index].value);
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}
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#endif
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analog_signal_index++;
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}
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// Calculate the Golay 24 parity for the corrected hex word
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encode_golay_24_6(corrected_hex_data+i*6, parity);
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// Now we know the parity we should have read from the signal. Use this information
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for (j=0; j<12; j+=2) // 6 iterations -> 6 dibits
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{
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// Given the bits, calculates the dibit
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dibit = (parity[j] << 1) | parity[j+1];
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// Now we know the dibit we should have read from the signal
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analog_signal_array[analog_signal_index].corrected_dibit = dibit;
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#ifdef HEURISTICS_DEBUG
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if (analog_signal_array[analog_signal_index].dibit != dibit)
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{
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printf("HDU parity corrected from %i to %i, analog value %i\n",
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analog_signal_array[analog_signal_index].dibit, dibit, analog_signal_array[analog_signal_index].value);
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}
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#endif
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analog_signal_index++;
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}
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}
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}
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/**
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* The important method that processes a full P25 HD unit.
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*/
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void
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processHDU(dsd_opts* opts, dsd_state* state)
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{
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char mi[73], mfid[9], algid[9], kid[17], tgid[17], tmpstr[255];
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int i, j;
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long talkgroup;
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int algidhex, kidhex;
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char hex[6];
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int status_count;
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int status;
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char hex_data[20][6]; // Data in hex-words (6 bit words). A total of 20 hex words.
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char hex_parity[16][6]; // Parity of the data, again in hex-word format. A total of 16 parity hex words.
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int irrecoverable_errors;
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AnalogSignal analog_signal_array[20*(3+6)+16*(3+6)];
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int analog_signal_index;
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analog_signal_index = 0;
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// we skip the status dibits that occur every 36 symbols
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// the next status symbol comes in 14 dibits from here
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// so we start counter at 36-14-1 = 21
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status_count = 21;
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// Read 20 hex words, correct them using their Golay 24 parity data.
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for (i=19; i>=0; i--)
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{
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read_and_correct_hex_word (opts, state, hex, &status_count, analog_signal_array, &analog_signal_index);
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// Store the corrected hex word into the hex_data store:
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for (j=0; j<6; j++)
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{
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hex_data[i][j] = hex[j];
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}
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}
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// Read the 16 parity hex word. These are used to FEC the 20 hex words using Reed-Solomon.
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for (i=15; i>=0; i--)
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{
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read_and_correct_hex_word (opts, state, hex, &status_count, analog_signal_array, &analog_signal_index);
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// Store the corrected hex word into the hex_parity store:
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for (j=0; j<6; j++)
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{
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hex_parity[i][j] = hex[j];
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}
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}
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// Don't forget to mark the first element as the start of a new sequence
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analog_signal_array[0].sequence_broken = 1;
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// Use the Reed-Solomon algorithm to correct the data. hex_data is modified in place
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irrecoverable_errors = check_and_fix_redsolomon_36_20_17((char*)hex_data, (char*)hex_parity);
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if (irrecoverable_errors != 0)
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{
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// The hex words failed the Reed-Solomon check. There were too many errors. Still we can use this
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// information to update an estimate of the BER.
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state->debug_header_critical_errors++;
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// We can correct (17-1)/2 = 8 errors. If we failed, it means that there were more than 8 errors in
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// these 20+16 words. But take into account that each hex word was already error corrected with
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// Golay 24, which can correct 3 bits on each sequence of (6+12) bits. We could say that there were
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// 9 errors of 4 bits.
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update_error_stats(&state->p25_heuristics, 20*6+16*6, 9*4);
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}
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else
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{
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// The hex words passed the Reed-Solomon check. This means that very likely they are correct and we
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// can trust that the digitizer did a good job with them. In other words, each analog value was
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// correctly assigned to a dibit. This is extremely useful information for the digitizer and we are
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// going to exploit it.
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char fixed_parity[16*6];
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// Correct the dibits that we did read according with the newly corrected hex_data values
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correct_golay_dibits_6((char*)hex_data, 20, analog_signal_array);
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// Generate again the Reed-Solomon parity for the corrected data
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encode_reedsolomon_36_20_17((char*)hex_data, fixed_parity);
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// Correct the dibits that we read according with the corrected parity values
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correct_golay_dibits_6(fixed_parity, 16, analog_signal_array+20*(3+6));
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// Now we have a bunch of dibits (composed of data and parity of different kinds) that we trust are all
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// correct. We also keep a record of the analog values from where each dibit is coming from.
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// This information is gold for the heuristics module.
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contribute_to_heuristics(state->rf_mod, &(state->p25_heuristics), analog_signal_array, 20*(3+6)+16*(3+6));
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}
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// Now put the corrected data on the DSD structures
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mi[72] = 0;
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mfid[8] = 0;
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algid[8] = 0;
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kid[16] = 0;
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tgid[16] = 0;
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mi[ 0] = hex_data[19][0] + '0';
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mi[ 1] = hex_data[19][1] + '0';
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mi[ 2] = hex_data[19][2] + '0';
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mi[ 3] = hex_data[19][3] + '0';
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mi[ 4] = hex_data[19][4] + '0';
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mi[ 5] = hex_data[19][5] + '0';
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mi[ 6] = hex_data[18][0] + '0';
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mi[ 7] = hex_data[18][1] + '0';
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mi[ 8] = hex_data[18][2] + '0';
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mi[ 9] = hex_data[18][3] + '0';
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mi[10] = hex_data[18][4] + '0';
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mi[11] = hex_data[18][5] + '0';
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mi[12] = hex_data[17][0] + '0';
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mi[13] = hex_data[17][1] + '0';
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mi[14] = hex_data[17][2] + '0';
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mi[15] = hex_data[17][3] + '0';
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mi[16] = hex_data[17][4] + '0';
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mi[17] = hex_data[17][5] + '0';
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mi[18] = hex_data[16][0] + '0';
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mi[19] = hex_data[16][1] + '0';
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mi[20] = hex_data[16][2] + '0';
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mi[21] = hex_data[16][3] + '0';
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mi[22] = hex_data[16][4] + '0';
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mi[23] = hex_data[16][5] + '0';
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mi[24] = hex_data[15][0] + '0';
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mi[25] = hex_data[15][1] + '0';
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mi[26] = hex_data[15][2] + '0';
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mi[27] = hex_data[15][3] + '0';
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mi[28] = hex_data[15][4] + '0';
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mi[29] = hex_data[15][5] + '0';
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mi[30] = hex_data[14][0] + '0';
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mi[31] = hex_data[14][1] + '0';
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mi[32] = hex_data[14][2] + '0';
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mi[33] = hex_data[14][3] + '0';
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mi[34] = hex_data[14][4] + '0';
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mi[35] = hex_data[14][5] + '0';
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mi[36] = hex_data[13][0] + '0';
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mi[37] = hex_data[13][1] + '0';
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mi[38] = hex_data[13][2] + '0';
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mi[39] = hex_data[13][3] + '0';
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mi[40] = hex_data[13][4] + '0';
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mi[41] = hex_data[13][5] + '0';
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mi[42] = hex_data[12][0] + '0';
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mi[43] = hex_data[12][1] + '0';
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mi[44] = hex_data[12][2] + '0';
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mi[45] = hex_data[12][3] + '0';
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mi[46] = hex_data[12][4] + '0';
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mi[47] = hex_data[12][5] + '0';
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mi[48] = hex_data[11][0] + '0';
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mi[49] = hex_data[11][1] + '0';
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mi[50] = hex_data[11][2] + '0';
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mi[51] = hex_data[11][3] + '0';
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mi[52] = hex_data[11][4] + '0';
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mi[53] = hex_data[11][5] + '0';
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mi[54] = hex_data[10][0] + '0';
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mi[55] = hex_data[10][1] + '0';
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mi[56] = hex_data[10][2] + '0';
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mi[57] = hex_data[10][3] + '0';
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mi[58] = hex_data[10][4] + '0';
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mi[59] = hex_data[10][5] + '0';
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mi[60] = hex_data[ 9][0] + '0';
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mi[61] = hex_data[ 9][1] + '0';
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mi[62] = hex_data[ 9][2] + '0';
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mi[63] = hex_data[ 9][3] + '0';
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mi[64] = hex_data[ 9][4] + '0';
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mi[65] = hex_data[ 9][5] + '0';
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mi[66] = hex_data[ 8][0] + '0';
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mi[67] = hex_data[ 8][1] + '0';
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mi[68] = hex_data[ 8][2] + '0';
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mi[69] = hex_data[ 8][3] + '0';
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mi[70] = hex_data[ 8][4] + '0';
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mi[71] = hex_data[ 8][5] + '0';
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mfid[0] = hex_data[ 7][0] + '0';
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mfid[1] = hex_data[ 7][1] + '0';
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mfid[2] = hex_data[ 7][2] + '0';
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mfid[3] = hex_data[ 7][3] + '0';
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mfid[4] = hex_data[ 7][4] + '0';
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mfid[5] = hex_data[ 7][5] + '0';
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mfid[6] = hex_data[ 6][0] + '0';
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mfid[7] = hex_data[ 6][1] + '0';
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algid[0] = hex_data[ 6][2] + '0'; // The important algorithm ID. This indicates whether the data is
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algid[1] = hex_data[ 6][3] + '0'; // encrypted and if so what is the encryption algorithm used.
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algid[2] = hex_data[ 6][4] + '0'; // A code 0x80 here means that the data is unencrypted.
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algid[3] = hex_data[ 6][5] + '0';
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algid[4] = hex_data[ 5][0] + '0';
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algid[5] = hex_data[ 5][1] + '0';
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algid[6] = hex_data[ 5][2] + '0';
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algid[7] = hex_data[ 5][3] + '0';
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kid[ 0] = hex_data[ 5][4] + '0';
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kid[ 1] = hex_data[ 5][5] + '0';
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kid[ 2] = hex_data[ 4][0] + '0'; // The encryption key ID
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kid[ 3] = hex_data[ 4][1] + '0';
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kid[ 4] = hex_data[ 4][2] + '0';
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kid[ 5] = hex_data[ 4][3] + '0';
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kid[ 6] = hex_data[ 4][4] + '0';
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kid[ 7] = hex_data[ 4][5] + '0';
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kid[ 8] = hex_data[ 3][0] + '0';
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kid[ 9] = hex_data[ 3][1] + '0';
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kid[10] = hex_data[ 3][2] + '0';
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kid[11] = hex_data[ 3][3] + '0';
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kid[12] = hex_data[ 3][4] + '0';
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kid[13] = hex_data[ 3][5] + '0';
|
|
|
|
kid[14] = hex_data[ 2][0] + '0';
|
|
kid[15] = hex_data[ 2][1] + '0';
|
|
tgid[ 0] = hex_data[ 2][2] + '0'; // Talk group ID
|
|
tgid[ 1] = hex_data[ 2][3] + '0';
|
|
tgid[ 2] = hex_data[ 2][4] + '0';
|
|
tgid[ 3] = hex_data[ 2][5] + '0';
|
|
|
|
tgid[ 4] = hex_data[ 1][0] + '0';
|
|
tgid[ 5] = hex_data[ 1][1] + '0';
|
|
tgid[ 6] = hex_data[ 1][2] + '0';
|
|
tgid[ 7] = hex_data[ 1][3] + '0';
|
|
tgid[ 8] = hex_data[ 1][4] + '0';
|
|
tgid[ 9] = hex_data[ 1][5] + '0';
|
|
|
|
tgid[10] = hex_data[ 0][0] + '0';
|
|
tgid[11] = hex_data[ 0][1] + '0';
|
|
tgid[12] = hex_data[ 0][2] + '0';
|
|
tgid[13] = hex_data[ 0][3] + '0';
|
|
tgid[14] = hex_data[ 0][4] + '0';
|
|
tgid[15] = hex_data[ 0][5] + '0';
|
|
|
|
state->p25kid = strtol(kid, NULL, 2);
|
|
|
|
skipDibit (opts, state, 5);
|
|
status = getDibit (opts, state);
|
|
//TODO: Do something useful with the status bits...
|
|
|
|
if (opts->p25enc == 1)
|
|
{
|
|
algidhex = strtol (algid, NULL, 2);
|
|
kidhex = strtol (kid, NULL, 2);
|
|
printf ("mi: %s algid: $%x kid: $%x\n", mi, algidhex, kidhex);
|
|
}
|
|
if (opts->p25lc == 1)
|
|
{
|
|
printf ("mfid: %s tgid: %s ", mfid, tgid);
|
|
if (opts->p25tg == 0)
|
|
{
|
|
printf ("\n");
|
|
}
|
|
}
|
|
|
|
j = 0;
|
|
if (strcmp (mfid, "10010000") == 0)
|
|
{
|
|
for (i = 4; i < 16; i++)
|
|
{
|
|
if (state->tgcount < 24)
|
|
{
|
|
state->tg[state->tgcount][j] = tgid[i];
|
|
}
|
|
tmpstr[j] = tgid[i];
|
|
j++;
|
|
}
|
|
tmpstr[12] = '0';
|
|
tmpstr[13] = '0';
|
|
tmpstr[14] = '0';
|
|
tmpstr[15] = '0';
|
|
}
|
|
else
|
|
{
|
|
for (i = 0; i < 16; i++)
|
|
{
|
|
if (state->tgcount < 24)
|
|
{
|
|
state->tg[state->tgcount][j] = tgid[i];
|
|
}
|
|
tmpstr[j] = tgid[i];
|
|
j++;
|
|
}
|
|
}
|
|
tmpstr[16] = 0;
|
|
talkgroup = strtol (tmpstr, NULL, 2);
|
|
state->lasttg = talkgroup;
|
|
if (state->tgcount < 24)
|
|
{
|
|
state->tgcount = state->tgcount + 1;
|
|
}
|
|
if (opts->p25tg == 1)
|
|
{
|
|
printf ("tg: %li\n", talkgroup);
|
|
}
|
|
}
|