diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/nmt/Makefile.am | 1 | ||||
| -rw-r--r-- | src/nmt/frame.c | 176 | ||||
| -rw-r--r-- | src/nmt/hagelbarger.c | 87 | ||||
| -rw-r--r-- | src/nmt/hagelbarger.h | 4 | ||||
| -rw-r--r-- | src/nmt/nmt.c | 91 | ||||
| -rw-r--r-- | src/test/Makefile.am | 10 | ||||
| -rw-r--r-- | src/test/test_hagelbarger.c | 29 |
7 files changed, 238 insertions, 160 deletions
diff --git a/src/nmt/Makefile.am b/src/nmt/Makefile.am index 91d5cff..1f738b9 100644 --- a/src/nmt/Makefile.am +++ b/src/nmt/Makefile.am @@ -8,6 +8,7 @@ nmt_SOURCES = \ countries.c \ transaction.c \ dsp.c \ + hagelbarger.c \ frame.c \ dms.c \ sms.c \ diff --git a/src/nmt/frame.c b/src/nmt/frame.c index bde6e8d..8cad3ca 100644 --- a/src/nmt/frame.c +++ b/src/nmt/frame.c @@ -27,6 +27,7 @@ #include "../common/timer.h" #include "nmt.h" #include "frame.h" +#include "hagelbarger.h" uint64_t nmt_encode_channel(int channel, int power) { @@ -969,161 +970,25 @@ static void assemble_frame(frame_t *frame, uint8_t *digits, int debug) } } -/* encode digits of a frame to 166 bits */ -static void encode_digits(const uint8_t *digits, char *bits) -{ - uint8_t x[64]; - int i; - uint8_t digit; - - /* copy bit sync and frame sync */ - memcpy(bits, "10101010101010111100010010", 26); - bits += 26; - - for (i = 0; i < 16; i++) { - digit = *digits++; - x[(i << 2) + 0] = (digit >> 3) & 1; - x[(i << 2) + 1] = (digit >> 2) & 1; - x[(i << 2) + 2] = (digit >> 1) & 1; - x[(i << 2) + 3] = digit & 1; - } - - /* parity check bits */ - for (i = 0; i < 3; i++) - bits[(i << 1)] = '1' - x[i]; - for (i = 3; i < 64; i++) - bits[(i << 1)] = '1' - (x[i] ^ x[i - 3]); - for (i = 64; i < 67; i++) - bits[(i << 1)] = '1' - x[i - 3]; - for (i = 67; i < 70; i++) - bits[(i << 1)] = '1'; - - /* information bits */ - for (i = 0; i < 6; i++) - bits[(i << 1) + 1] = '0'; - for (i = 6; i < 70; i++) - bits[(i << 1) + 1] = x[i - 6] + '0'; -} - -/* debug parity check */ -//#define DEBUG_DECODE - -/* decode digits from 140 bits (not including sync) */ -// FIXME: do real convolutional decoding -static int decode_digits(uint8_t *digits, const char *bits, int callack) -{ - uint8_t x[64]; - int i, short_frame = 0; - - /* information bits */ - for (i = 0; i < 6; i++) { - if (bits[(i << 1) + 1] != '0') { -#ifdef DEBUG_DECODE - PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at information bit #%d.\n", i); -#endif - return -1; - } - } - for (i = 6; i < 70; i++) - x[i - 6] = bits[(i << 1) + 1] - '0'; - - /* create digits */ - for (i = 0; i < 16; i++) { - digits[i] = ((x[(i << 2) + 0] & 1) << 3) - | ((x[(i << 2) + 1] & 1) << 2) - | ((x[(i << 2) + 2] & 1) << 1) - | (x[(i << 2) + 3] & 1); - } - - /* check for short frame */ - if (callack && (digits[3] == 1 || digits[3] == 15)) { - digits[13] = 0; - digits[14] = 0; - digits[15] = 0; - short_frame = 1; -#ifdef DEBUG_DECODE - PDEBUG(DFRAME, DEBUG_DEBUG, "Received shortened frame\n"); -#endif - } - - /* parity check bits */ - for (i = 0; i < 3; i++) { - if (bits[(i << 1)] != '1' - x[i]) { -#ifdef DEBUG_DECODE - PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); -#endif - return -1; - } - } -#if 0 -#warning this check does not work, since we get error even at bit 50 - for (i = 3; i < ((short_frame) ? 52 : 64); i++) { - if (bits[(i << 1)] != '1' - (x[i] ^ x[i - 3])) { - /* According to NMT Doc 450-3, bits after Y(114) shall - * be omitted for short frame. It would make more sense - * to stop after Y(116), so only the last three digits - * are omitted and not the last bit of digit13 also. - * Tests have showed that it we receive correctly up to - * Y(116), but we ignore an error, if only up to Y(114) - * is received. - */ - if (short_frame && i == 51) { - PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad after bit Y(114), ignoring.\n"); - digits[13] = 0; - break; - } -#ifdef DEBUG_DECODE - PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); -#endif - return -1; - } - } -#endif - /* Tests showed corrupt frame at parity #50 (i == 50) - * We just ignore whatever we receive after 48 bits of checksum. - * This is not the correct approach, but in case of a corrupt - * frame 10.a, we would drop it, if it failes later checks. - */ - for (i = 3; i < ((short_frame) ? 48 : 64); i++) { - if (bits[(i << 1)] != '1' - (x[i] ^ x[i - 3])) { -#ifdef DEBUG_DECODE - PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); -#endif - return -1; - } - } - if (short_frame) - return 0; - for (i = 64; i < 67; i++) { - if (bits[(i << 1)] != '1' - x[i - 3]) { -#ifdef DEBUG_DECODE - PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); -#endif - return -1; - } - } - for (i = 67; i < 70; i++) { - if (bits[(i << 1)] != '1') { -#ifdef DEBUG_DECODE - PDEBUG(DFRAME, DEBUG_DEBUG, "Frame bad at parity bit #%d.\n", i); -#endif - return -1; - } - } - - return 0; -} - /* encode frame to bits * debug can be turned on or off */ const char *encode_frame(frame_t *frame, int debug) { - uint8_t digits[16]; + uint8_t digits[16], message[9], code[18]; static char bits[166]; + int i; assemble_frame(frame, digits, debug); - encode_digits(digits, bits); + + /* hagelbarger code */ + message[8] = 0x00; + for (i = 0; i < 8; i++) + message[i] = (digits[i * 2] << 4) | digits[i * 2 + 1]; + hagelbarger_encode(message, code, 72); + memcpy(bits, "10101010101010111100010010", 26); + for (i = 0; i < 140; i++) + bits[i + 26] = ((code[i / 8] >> (7 - (i & 7))) & 1) + '0'; return bits; } @@ -1131,12 +996,19 @@ const char *encode_frame(frame_t *frame, int debug) /* decode bits to frame */ int decode_frame(frame_t *frame, const char *bits, enum nmt_direction direction, int callack) { - uint8_t digits[16]; - int rc; + uint8_t digits[16], message[8], code[19]; + int i; + + /* hagelbarger code */ + memset(code, 0x00, sizeof(code)); + for (i = 0; i < 140; i++) + code[i / 8] |= (bits[i] & 1) << (7 - (i & 7)); + hagelbarger_decode(code, message, 64); + for (i = 0; i < 8; i++) { + digits[i * 2] = message[i] >> 4; + digits[i * 2 + 1] = message[i] & 0x0f; + } - rc = decode_digits(digits, bits, callack); - if (rc < 0) - return rc; disassemble_frame(frame, digits, direction, callack); return 0; diff --git a/src/nmt/hagelbarger.c b/src/nmt/hagelbarger.c new file mode 100644 index 0000000..f6ac2cd --- /dev/null +++ b/src/nmt/hagelbarger.c @@ -0,0 +1,87 @@ +/* Hagelbarger (6,19) code + * + * A burst up to 6 encoded bits may be corrupt, to correct them. + * After corrupt bits, a minimum of 19 bits must be correct to correct + * another burst of corrupted bits. + * + * There is no parity check, so it is required to check all information + * elements of each message. Messages that contain signals or digits are + * protected by repeating the digits in the information element. + * + * (C) 2017 by Andreas Eversberg <jolly@eversberg.eu> + * All Rights Reserved + * + * 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 + * the Free Software Foundation, either version 3 of the License, or + * (at your option) any later version. + * + * This program 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 this program. If not, see <http://www.gnu.org/licenses/>. + */ + +#include "stdint.h" + +/* To encode NMT message: (MSB first) + * Use input with 9 bytes, the last byte must be 0x00. + * Use output with 18 bytes, ignore the last four (lower) bits of last byte. + * Use length of 72. + */ +void hagelbarger_encode(const uint8_t *input, uint8_t *output, int length) +{ + uint8_t reg = 0x00, data, check; + int i; + + for (i = 0; i < length; i++) { + /* get data from input (MSB first) */ + data = (input[i / 8] >> (7 - (i & 7))) & 1; + /* push data into shift register (LSB first) */ + reg = (reg << 1) | data; + /* get data bit from register */ + data = (reg >> 6) & 1; + /* calc check bit from register */ + check = (reg + (reg >> 3) + 1) & 1; + /* put check bit and data bit to output (MSB first) */ + output[i / 4] = (output[i / 4] << 2) | (check << 1) | data; + } +} + +/* To decode NMT message: (MSB first) + * Use input with 19 bytes, the unused last 12 (lower) bits must be zero. + * Use output with 8 bytes. + * Use length of 64. + */ +void hagelbarger_decode(const uint8_t *input, uint8_t *output, int length) +{ + uint16_t reg_data = 0x00, reg_check = 0x00, data, check, r_parity, s_parity; + int i; + + length += 10; + + for (i = 0; i < length; i++) { + /* get check bit from input (MSB first) */ + check = (input[i / 4] >> (7 - (i & 3) * 2)) & 1; + /* get data bit from input (MSB first) */ + data = (input[i / 4] >> (6 - (i & 3) * 2)) & 1; + /* push check bit into shift register (LSB first) */ + reg_check = (reg_check << 1) | check; + /* push data bit into shift register (LSB first) */ + reg_data = (reg_data << 1) | data; + /* calculate parity */ + r_parity = (reg_data + (reg_data >> 3) + (reg_check >> 6) + 1) & 1; + s_parity = ((reg_data >> 3) + (reg_data >> 6) + (reg_check >> 9) + 1) & 1; + /* flip message bit, if both parity checks fail */ + /* use 4th bit that will be shifted to 5th bit next loop */ + if (r_parity && s_parity) + reg_data ^= 0x0008; + /* put message bit to output (MSB first) */ + if (i >= 10) + output[(i - 10) / 8] = (output[(i - 10) / 8] << 1) | ((reg_data >> 4) & 1); + } +} + diff --git a/src/nmt/hagelbarger.h b/src/nmt/hagelbarger.h new file mode 100644 index 0000000..9076afc --- /dev/null +++ b/src/nmt/hagelbarger.h @@ -0,0 +1,4 @@ + +void hagelbarger_encode(const uint8_t *input, uint8_t *output, int length); +void hagelbarger_decode(const uint8_t *input, uint8_t *output, int length); + diff --git a/src/nmt/nmt.c b/src/nmt/nmt.c index 09f40e9..809a168 100644 --- a/src/nmt/nmt.c +++ b/src/nmt/nmt.c @@ -829,15 +829,21 @@ static void rx_mo_dialing(nmt_t *nmt, frame_t *frame) /* max digits received */ if (len + 1 == sizeof(nmt->dialing)) break; - /* received odd digit, but be already have odd number of digits */ if ((len & 1)) { - if (nmt->rx_frame_count > 1) + /* received odd digit, but be already have odd number of digits */ + if (nmt->rx_frame_count > 1) /* we lost even digit */ goto missing_digit; break; - } else if (len) { - if (nmt->rx_frame_count > 3) + } else if (len) { /* complain only after first digit */ + /* received odd digit, and we have even number of digits */ + if (nmt->rx_frame_count > 3) /* we lost even digit */ goto missing_digit; } + if ((frame->digit >> 12) != 0x00) /* digit 0x0 0x0, x, x, x */ + goto not_right_position; + if (((frame->digit >> 8) & 0xf) != ((frame->digit >> 4) & 0xf) + || ((frame->digit >> 4) & 0xf) != (frame->digit & 0xf)) + goto not_consistent_digit; nmt->dialing[len] = nmt_value2digit(frame->digit); nmt->dialing[len + 1] = '\0'; PDEBUG_CHAN(DNMT, DEBUG_INFO, "Received (odd) digit %c.\n", nmt->dialing[len]); @@ -857,15 +863,24 @@ static void rx_mo_dialing(nmt_t *nmt, frame_t *frame) /* max digits received */ if (len + 1 == sizeof(nmt->dialing)) break; - /* received odd digit, but be already have odd number of digits */ + /* received even digit, but no digit yet, so we lost first odd digit */ + if (!len) + goto missing_digit; if (!(len & 1)) { - if (len && nmt->rx_frame_count > 1) + /* received even digit, but be already have even number of digits */ + if (nmt->rx_frame_count > 1) /* we lost odd digit */ goto missing_digit; break; } else { - if (nmt->rx_frame_count > 3) + /* received even digit, and we have odd number of digits */ + if (nmt->rx_frame_count > 3) /* we lost odd digit */ goto missing_digit; } + if ((frame->digit >> 12) != 0xff) /* digit 0xf 0xf, x, x, x */ + goto not_right_position; + if (((frame->digit >> 8) & 0xf) != ((frame->digit >> 4) & 0xf) + || ((frame->digit >> 4) & 0xf) != (frame->digit & 0xf)) + goto not_consistent_digit; nmt->dialing[len] = nmt_value2digit(frame->digit); nmt->dialing[len + 1] = '\0'; PDEBUG_CHAN(DNMT, DEBUG_INFO, "Received (even) digit %c.\n", nmt->dialing[len]); @@ -906,6 +921,15 @@ static void rx_mo_dialing(nmt_t *nmt, frame_t *frame) missing_digit: PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Missing digit, aborting.\n"); nmt_release(nmt); + return; + +not_right_position: + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Position information of digit does not match, ignoring due to corrupt frame.\n"); + return; + +not_consistent_digit: + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Digit repetition in frame does not match, ignoring due to corrupt frame.\n"); + return; } static void tx_mo_complete(nmt_t *nmt, frame_t *frame) @@ -1102,6 +1126,13 @@ static void rx_mt_autoanswer(nmt_t *nmt, frame_t *frame) break; if (!match_subscriber(trans, frame)) break; + if (((frame->line_signal >> 16) & 0xf) != ((frame->line_signal >> 12) & 0xf) + || ((frame->line_signal >> 12) & 0xf) != ((frame->line_signal >> 8) & 0xf) + || ((frame->line_signal >> 8) & 0xf) != ((frame->line_signal >> 4) & 0xf) + || ((frame->line_signal >> 4) & 0xf) != (frame->line_signal & 0xf)) { + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Line signal repetition in frame does not match, ignoring due to corrupt frame.\n"); + break; + } if ((frame->line_signal & 0xf) != 12) break; PDEBUG_CHAN(DNMT, DEBUG_INFO, "Received acknowledge to autoanswer.\n"); @@ -1153,6 +1184,13 @@ static void rx_mt_ringing(nmt_t *nmt, frame_t *frame) break; if (!match_subscriber(trans, frame)) break; + if (((frame->line_signal >> 16) & 0xf) != ((frame->line_signal >> 12) & 0xf) + || ((frame->line_signal >> 12) & 0xf) != ((frame->line_signal >> 8) & 0xf) + || ((frame->line_signal >> 8) & 0xf) != ((frame->line_signal >> 4) & 0xf) + || ((frame->line_signal >> 4) & 0xf) != (frame->line_signal & 0xf)) { + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Line signal repetition in frame does not match, ignoring due to corrupt frame.\n"); + break; + } if ((frame->line_signal & 0xf) != 14) break; PDEBUG_CHAN(DNMT, DEBUG_INFO, "Received 'answer' from phone.\n"); @@ -1240,6 +1278,13 @@ static void rx_mt_release(nmt_t *nmt, frame_t *frame) break; if (!match_subscriber(trans, frame)) break; + if (((frame->line_signal >> 16) & 0xf) != ((frame->line_signal >> 12) & 0xf) + || ((frame->line_signal >> 12) & 0xf) != ((frame->line_signal >> 8) & 0xf) + || ((frame->line_signal >> 8) & 0xf) != ((frame->line_signal >> 4) & 0xf) + || ((frame->line_signal >> 4) & 0xf) != (frame->line_signal & 0xf)) { + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Line signal repetition in frame does not match, ignoring due to corrupt frame.\n"); + break; + } if ((frame->line_signal & 0xf) != 1) break; PDEBUG_CHAN(DNMT, DEBUG_INFO, "Received release guard.\n"); @@ -1312,6 +1357,13 @@ static void rx_active(nmt_t *nmt, frame_t *frame) break; if (!match_subscriber(trans, frame)) break; + if (((frame->line_signal >> 16) & 0xf) != ((frame->line_signal >> 12) & 0xf) + || ((frame->line_signal >> 12) & 0xf) != ((frame->line_signal >> 8) & 0xf) + || ((frame->line_signal >> 8) & 0xf) != ((frame->line_signal >> 4) & 0xf) + || ((frame->line_signal >> 4) & 0xf) != (frame->line_signal & 0xf)) { + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Line signal repetition in frame does not match, ignoring due to corrupt frame.\n"); + break; + } switch ((frame->line_signal & 0xf)) { case 5: PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Register Recall is not supported.\n"); @@ -1344,6 +1396,15 @@ static void rx_active(nmt_t *nmt, frame_t *frame) break; if ((nmt->mft_num & 1)) break; + if ((frame->digit >> 12) != 0x00) { + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Position information of digit does not match, ignoring due to corrupt frame.\n"); + break; + } + if (((frame->digit >> 8) & 0xf) != ((frame->digit >> 4) & 0xf) + || ((frame->digit >> 4) & 0xf) != (frame->digit & 0xf)) { + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Digit repetition in frame does not match, ignoring due to corrupt frame.\n"); + break; + } digit = nmt_value2digit(frame->digit); dtmf_set_tone(&nmt->dtmf, digit); PDEBUG_CHAN(DNMT, DEBUG_INFO, "Received (odd) digit %c.\n", digit); @@ -1358,6 +1419,15 @@ static void rx_active(nmt_t *nmt, frame_t *frame) break; if (!(nmt->mft_num & 1)) break; + if ((frame->digit >> 12) != 0xff) { + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Position information of digit does not match, ignoring due to corrupt frame.\n"); + break; + } + if (((frame->digit >> 8) & 0xf) != ((frame->digit >> 4) & 0xf) + || ((frame->digit >> 4) & 0xf) != (frame->digit & 0xf)) { + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Digit repetition in frame does not match, ignoring due to corrupt frame.\n"); + break; + } digit = nmt_value2digit(frame->digit); dtmf_set_tone(&nmt->dtmf, digit); PDEBUG_CHAN(DNMT, DEBUG_INFO, "Received (even) digit %c.\n", digit); @@ -1431,6 +1501,13 @@ void nmt_receive_frame(nmt_t *nmt, const char *bits, double quality, double leve return; if (!match_subscriber(nmt->trans, &frame)) return; + if (((frame.line_signal >> 16) & 0xf) != ((frame.line_signal >> 12) & 0xf) + || ((frame.line_signal >> 12) & 0xf) != ((frame.line_signal >> 8) & 0xf) + || ((frame.line_signal >> 8) & 0xf) != ((frame.line_signal >> 4) & 0xf) + || ((frame.line_signal >> 4) & 0xf) != (frame.line_signal & 0xf)) { + PDEBUG_CHAN(DNMT, DEBUG_NOTICE, "Line signal repetition in frame does not match, ignoring due to corrupt frame.\n"); + return; + } PDEBUG_CHAN(DNMT, DEBUG_INFO, "Received clearing by mobile phone in state %s.\n", nmt_state_name(nmt->state)); nmt_new_state(nmt, STATE_MO_RELEASE); nmt->tx_frame_count = 0; diff --git a/src/test/Makefile.am b/src/test/Makefile.am index 852c235..dbe6c73 100644 --- a/src/test/Makefile.am +++ b/src/test/Makefile.am @@ -7,7 +7,8 @@ noinst_PROGRAMS = \ test_emphasis \ test_dms \ test_sms \ - test_performance + test_performance \ + test_hagelbarger test_filter_SOURCES = test_filter.c dummy.c @@ -77,3 +78,10 @@ test_performance_LDADD = \ $(SOAPY_LIBS) \ -lm +test_hagelbarger_SOURCES = \ + $(top_builddir)/src/nmt/hagelbarger.c \ + test_hagelbarger.c + +test_hagelbarger_LDADD = \ + $(COMMON_LA) + diff --git a/src/test/test_hagelbarger.c b/src/test/test_hagelbarger.c new file mode 100644 index 0000000..d4117e3 --- /dev/null +++ b/src/test/test_hagelbarger.c @@ -0,0 +1,29 @@ +#include "stdio.h" +#include "stdint.h" +#include "string.h" +#include "../nmt/hagelbarger.h" + +int main(void) +{ + uint8_t message[9] = "JollyRog", code[20]; + + printf("Message: %s\n", message); + + /* clean tail at code bit 72 and above */ + memset(code, 0, sizeof(code)); + + /* encode message */ + hagelbarger_encode(message, code, 72); + + /* corrupt data */ + code[0] ^= 0xfc; + code[3] ^= 0xfc; + code[7] ^= 0xfc; + + /* decode */ + hagelbarger_decode(code, message, 64); + printf("Decoded: %s (must be the same as above)\n", message); + + return 0; +} + |