/* * (C) 2013 by Andreas Eversberg * (C) 2015 by Alexander Chemeris * (C) 2016 by Tom Tsou * (C) 2017 by Harald Welte * * All Rights Reserved * * SPDX-License-Identifier: GPL-2.0+ * * 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 2 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. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include #include /*! \mainpage libosmocoding Documentation * * \section sec_intro Introduction * This library is a collection of definitions, tables and functions * implementing the GSM/GPRS/EGPRS channel coding (and decoding) as * specified in 3GPP TS 05.03 / 45.003. * * libosmocoding is developed as part of the Osmocom (Open Source Mobile * Communications) project, a community-based, collaborative development * project to create Free and Open Source implementations of mobile * communications systems. For more information about Osmocom, please * see https://osmocom.org/ * * \section sec_copyright Copyright and License * Copyright © 2013 by Andreas Eversberg\n * Copyright © 2015 by Alexander Chemeris\n * Copyright © 2016 by Tom Tsou\n * Documentation Copyright © 2017 by Harald Welte\n * All rights reserved. \n\n * The source code of libosmocoding is licensed under the terms of the GNU * General Public License as published by the Free Software Foundation; * either version 2 of the License, or (at your option) any later * version.\n * See or COPYING included in the source * code package istelf.\n * The information detailed here is provided AS IS with NO WARRANTY OF * ANY KIND, INCLUDING THE WARRANTY OF DESIGN, MERCHANTABILITY AND * FITNESS FOR A PARTICULAR PURPOSE. * \n\n * * \section sec_tracker Homepage + Issue Tracker * libosmocoding is distributed as part of libosmocore and shares its * project page at http://osmocom.org/projects/libosmocore * * An Issue Tracker can be found at * https://osmocom.org/projects/libosmocore/issues * * \section sec_contact Contact and Support * Community-based support is available at the OpenBSC mailing list * \n * Commercial support options available upon request from * */ /*! \addtogroup coding * @{ * * GSM TS 05.03 coding * * This module is the "master module" of libosmocoding. It uses the * various other modules (mapping, parity, interleaving) in order to * implement the complete channel coding (and decoding) chain for the * various channel types as defined in TS 05.03 / 45.003. * * \file gsm0503_coding.c */ /* * EGPRS coding limits */ /* Max header size with parity bits */ #define EGPRS_HDR_UPP_MAX 54 /* Max encoded header size */ #define EGPRS_HDR_C_MAX 162 /* Max punctured header size */ #define EGPRS_HDR_HC_MAX 160 /* Max data block size with parity bits */ #define EGPRS_DATA_U_MAX 612 /* Max encoded data block size */ #define EGPRS_DATA_C_MAX 1836 /* Max single block punctured data size */ #define EGPRS_DATA_DC_MAX 1248 /* Dual block punctured data size */ #define EGPRS_DATA_C1 612 #define EGPRS_DATA_C2 EGPRS_DATA_C1 /*! union across the three different EGPRS Uplink header types */ union gprs_rlc_ul_hdr_egprs { struct gprs_rlc_ul_header_egprs_1 type1; struct gprs_rlc_ul_header_egprs_2 type2; struct gprs_rlc_ul_header_egprs_3 type3; }; /*! union across the three different EGPRS Downlink header types */ union gprs_rlc_dl_hdr_egprs { struct gprs_rlc_dl_header_egprs_1 type1; struct gprs_rlc_dl_header_egprs_2 type2; struct gprs_rlc_dl_header_egprs_3 type3; }; /*! Structure describing a Modulation and Coding Scheme */ struct gsm0503_mcs_code { /*! Modulation and Coding Scheme (MSC) number */ uint8_t mcs; /*! Length of Uplink Stealing Flag (USF) in bits */ uint8_t usf_len; /* Header coding */ /*! Length of header (bits) */ uint8_t hdr_len; /*! Length of header convolutional code */ uint8_t hdr_code_len; /*! Length of header code puncturing sequence */ uint8_t hdr_punc_len; /*! header convolutional code */ const struct osmo_conv_code *hdr_conv; /*! header puncturing sequence */ const uint8_t *hdr_punc; /* Data coding */ /*! length of data (bits) */ uint16_t data_len; /*! length of data convolutional code */ uint16_t data_code_len; /*! length of data code puncturing sequence */ uint16_t data_punc_len; /*! data convolutional code */ const struct osmo_conv_code *data_conv; /*! data puncturing sequences */ const uint8_t *data_punc[3]; }; /* * EGPRS UL coding parameters */ const struct gsm0503_mcs_code gsm0503_mcs_ul_codes[EGPRS_NUM_MCS] = { { .mcs = EGPRS_MCS0, }, { .mcs = EGPRS_MCS1, .hdr_len = 31, .hdr_code_len = 117, .hdr_punc_len = 80, .hdr_conv = &gsm0503_mcs1_ul_hdr, .hdr_punc = gsm0503_puncture_mcs1_ul_hdr, .data_len = 178, .data_code_len = 588, .data_punc_len = 372, .data_conv = &gsm0503_mcs1, .data_punc = { gsm0503_puncture_mcs1_p1, gsm0503_puncture_mcs1_p2, NULL, }, }, { .mcs = EGPRS_MCS2, .hdr_len = 31, .hdr_code_len = 117, .hdr_punc_len = 80, .hdr_conv = &gsm0503_mcs1_ul_hdr, .hdr_punc = gsm0503_puncture_mcs1_ul_hdr, .data_len = 226, .data_code_len = 732, .data_punc_len = 372, .data_conv = &gsm0503_mcs2, .data_punc = { gsm0503_puncture_mcs2_p1, gsm0503_puncture_mcs2_p2, NULL, }, }, { .mcs = EGPRS_MCS3, .hdr_len = 31, .hdr_code_len = 117, .hdr_punc_len = 80, .hdr_conv = &gsm0503_mcs1_ul_hdr, .hdr_punc = gsm0503_puncture_mcs1_ul_hdr, .data_len = 298, .data_code_len = 948, .data_punc_len = 372, .data_conv = &gsm0503_mcs3, .data_punc = { gsm0503_puncture_mcs3_p1, gsm0503_puncture_mcs3_p2, gsm0503_puncture_mcs3_p3, }, }, { .mcs = EGPRS_MCS4, .hdr_len = 31, .hdr_code_len = 117, .hdr_punc_len = 80, .hdr_conv = &gsm0503_mcs1_ul_hdr, .hdr_punc = gsm0503_puncture_mcs1_ul_hdr, .data_len = 354, .data_code_len = 1116, .data_punc_len = 372, .data_conv = &gsm0503_mcs4, .data_punc = { gsm0503_puncture_mcs4_p1, gsm0503_puncture_mcs4_p2, gsm0503_puncture_mcs4_p3, }, }, { .mcs = EGPRS_MCS5, .hdr_len = 37, .hdr_code_len = 135, .hdr_punc_len = 136, .hdr_conv = &gsm0503_mcs5_ul_hdr, .hdr_punc = NULL, .data_len = 450, .data_code_len = 1404, .data_punc_len = 1248, .data_conv = &gsm0503_mcs5, .data_punc = { gsm0503_puncture_mcs5_p1, gsm0503_puncture_mcs5_p2, NULL, }, }, { .mcs = EGPRS_MCS6, .hdr_len = 37, .hdr_code_len = 135, .hdr_punc_len = 136, .hdr_conv = &gsm0503_mcs5_ul_hdr, .hdr_punc = NULL, .data_len = 594, .data_code_len = 1836, .data_punc_len = 1248, .data_conv = &gsm0503_mcs6, .data_punc = { gsm0503_puncture_mcs6_p1, gsm0503_puncture_mcs6_p2, NULL, }, }, { .mcs = EGPRS_MCS7, .hdr_len = 46, .hdr_code_len = 162, .hdr_punc_len = 160, .hdr_conv = &gsm0503_mcs7_ul_hdr, .hdr_punc = gsm0503_puncture_mcs7_ul_hdr, .data_len = 900, .data_code_len = 1404, .data_punc_len = 612, .data_conv = &gsm0503_mcs7, .data_punc = { gsm0503_puncture_mcs7_p1, gsm0503_puncture_mcs7_p2, gsm0503_puncture_mcs7_p3, } }, { .mcs = EGPRS_MCS8, .hdr_len = 46, .hdr_code_len = 162, .hdr_punc_len = 160, .hdr_conv = &gsm0503_mcs7_ul_hdr, .hdr_punc = gsm0503_puncture_mcs7_ul_hdr, .data_len = 1092, .data_code_len = 1692, .data_punc_len = 612, .data_conv = &gsm0503_mcs8, .data_punc = { gsm0503_puncture_mcs8_p1, gsm0503_puncture_mcs8_p2, gsm0503_puncture_mcs8_p3, } }, { .mcs = EGPRS_MCS9, .hdr_len = 46, .hdr_code_len = 162, .hdr_punc_len = 160, .hdr_conv = &gsm0503_mcs7_ul_hdr, .hdr_punc = gsm0503_puncture_mcs7_ul_hdr, .data_len = 1188, .data_code_len = 1836, .data_punc_len = 612, .data_conv = &gsm0503_mcs9, .data_punc = { gsm0503_puncture_mcs9_p1, gsm0503_puncture_mcs9_p2, gsm0503_puncture_mcs9_p3, } }, }; /* * EGPRS DL coding parameters */ const struct gsm0503_mcs_code gsm0503_mcs_dl_codes[EGPRS_NUM_MCS] = { { .mcs = EGPRS_MCS0, }, { .mcs = EGPRS_MCS1, .usf_len = 3, .hdr_len = 28, .hdr_code_len = 108, .hdr_punc_len = 68, .hdr_conv = &gsm0503_mcs1_dl_hdr, .hdr_punc = gsm0503_puncture_mcs1_dl_hdr, .data_len = 178, .data_code_len = 588, .data_punc_len = 372, .data_conv = &gsm0503_mcs1, .data_punc = { gsm0503_puncture_mcs1_p1, gsm0503_puncture_mcs1_p2, NULL, }, }, { .mcs = EGPRS_MCS2, .usf_len = 3, .hdr_len = 28, .hdr_code_len = 108, .hdr_punc_len = 68, .hdr_conv = &gsm0503_mcs1_dl_hdr, .hdr_punc = gsm0503_puncture_mcs1_dl_hdr, .data_len = 226, .data_code_len = 732, .data_punc_len = 372, .data_conv = &gsm0503_mcs2, .data_punc = { gsm0503_puncture_mcs2_p1, gsm0503_puncture_mcs2_p2, NULL, }, }, { .mcs = EGPRS_MCS3, .usf_len = 3, .hdr_len = 28, .hdr_code_len = 108, .hdr_punc_len = 68, .hdr_conv = &gsm0503_mcs1_dl_hdr, .hdr_punc = gsm0503_puncture_mcs1_dl_hdr, .data_len = 298, .data_code_len = 948, .data_punc_len = 372, .data_conv = &gsm0503_mcs3, .data_punc = { gsm0503_puncture_mcs3_p1, gsm0503_puncture_mcs3_p2, gsm0503_puncture_mcs3_p3, }, }, { .mcs = EGPRS_MCS4, .usf_len = 3, .hdr_len = 28, .hdr_code_len = 108, .hdr_punc_len = 68, .hdr_conv = &gsm0503_mcs1_dl_hdr, .hdr_punc = gsm0503_puncture_mcs1_dl_hdr, .data_len = 354, .data_code_len = 1116, .data_punc_len = 372, .data_conv = &gsm0503_mcs4, .data_punc = { gsm0503_puncture_mcs4_p1, gsm0503_puncture_mcs4_p2, gsm0503_puncture_mcs4_p3, }, }, { .mcs = EGPRS_MCS5, .usf_len = 3, .hdr_len = 25, .hdr_code_len = 99, .hdr_punc_len = 100, .hdr_conv = &gsm0503_mcs5_dl_hdr, .hdr_punc = NULL, .data_len = 450, .data_code_len = 1404, .data_punc_len = 1248, .data_conv = &gsm0503_mcs5, .data_punc = { gsm0503_puncture_mcs5_p1, gsm0503_puncture_mcs5_p2, NULL, }, }, { .mcs = EGPRS_MCS6, .usf_len = 3, .hdr_len = 25, .hdr_code_len = 99, .hdr_punc_len = 100, .hdr_conv = &gsm0503_mcs5_dl_hdr, .hdr_punc = NULL, .data_len = 594, .data_code_len = 1836, .data_punc_len = 1248, .data_conv = &gsm0503_mcs6, .data_punc = { gsm0503_puncture_mcs6_p1, gsm0503_puncture_mcs6_p2, NULL, }, }, { .mcs = EGPRS_MCS7, .usf_len = 3, .hdr_len = 37, .hdr_code_len = 135, .hdr_punc_len = 124, .hdr_conv = &gsm0503_mcs7_dl_hdr, .hdr_punc = gsm0503_puncture_mcs7_dl_hdr, .data_len = 900, .data_code_len = 1404, .data_punc_len = 612, .data_conv = &gsm0503_mcs7, .data_punc = { gsm0503_puncture_mcs7_p1, gsm0503_puncture_mcs7_p2, gsm0503_puncture_mcs7_p3, } }, { .mcs = EGPRS_MCS8, .usf_len = 3, .hdr_len = 37, .hdr_code_len = 135, .hdr_punc_len = 124, .hdr_conv = &gsm0503_mcs7_dl_hdr, .hdr_punc = gsm0503_puncture_mcs7_dl_hdr, .data_len = 1092, .data_code_len = 1692, .data_punc_len = 612, .data_conv = &gsm0503_mcs8, .data_punc = { gsm0503_puncture_mcs8_p1, gsm0503_puncture_mcs8_p2, gsm0503_puncture_mcs8_p3, } }, { .mcs = EGPRS_MCS9, .usf_len = 3, .hdr_len = 37, .hdr_code_len = 135, .hdr_punc_len = 124, .hdr_conv = &gsm0503_mcs7_dl_hdr, .hdr_punc = gsm0503_puncture_mcs7_dl_hdr, .data_len = 1188, .data_code_len = 1836, .data_punc_len = 612, .data_conv = &gsm0503_mcs9, .data_punc = { gsm0503_puncture_mcs9_p1, gsm0503_puncture_mcs9_p2, gsm0503_puncture_mcs9_p3, } }, }; /*! Convolutional Decode + compute BER for punctured codes * \param[in] code Description of Convolutional Code * \param[in] input Input soft-bits (-127...127) * \param[out] output bits * \param[out] n_errors Number of bit-errors * \param[out] n_bits_total Number of bits * \param[in] data_punc Puncturing mask array. Can be NULL. */ static int osmo_conv_decode_ber_punctured(const struct osmo_conv_code *code, const sbit_t *input, ubit_t *output, int *n_errors, int *n_bits_total, const uint8_t *data_punc) { int res, coded_len; ubit_t recoded[EGPRS_DATA_C_MAX]; res = osmo_conv_decode(code, input, output); if (!n_bits_total && !n_errors) return res; coded_len = osmo_conv_encode(code, output, recoded); OSMO_ASSERT(ARRAY_SIZE(recoded) >= coded_len); /* Count bit errors */ if (n_errors) { *n_errors = 0; for (unsigned int i = 0; i < coded_len; i++) { /* punctured bits do not count as bit errors */ if (data_punc != NULL && data_punc[i]) continue; if (recoded[i] == 1 && input[i] < 0) continue; if (recoded[i] == 0 && input[i] > 0) continue; *n_errors += 1; } } if (n_bits_total) *n_bits_total = coded_len; return res; } /*! Convolutional Decode + compute BER for non-punctured codes * \param[in] code Description of Convolutional Code * \param[in] input Input soft-bits (-127...127) * \param[out] output bits * \param[out] n_errors Number of bit-errors * \param[out] n_bits_total Number of bits */ static int osmo_conv_decode_ber(const struct osmo_conv_code *code, const sbit_t *input, ubit_t *output, int *n_errors, int *n_bits_total) { return osmo_conv_decode_ber_punctured(code, input, output, n_errors, n_bits_total, NULL); } /*! convenience wrapper for decoding coded bits * \param[out] l2_data caller-allocated buffer for L2 Frame * \param[in] cB 456 coded (soft) bits as per TS 05.03 4.1.3 * \param[out] n_errors Number of detected errors * \param[out] n_bits_total Number of total coded bits * \returns 0 on success; -1 on CRC error */ static int _xcch_decode_cB(uint8_t *l2_data, const sbit_t *cB, int *n_errors, int *n_bits_total) { ubit_t conv[224]; int rv; osmo_conv_decode_ber(&gsm0503_xcch, cB, conv, n_errors, n_bits_total); rv = osmo_crc64gen_check_bits(&gsm0503_fire_crc40, conv, 184, conv + 184); if (rv) return -1; osmo_ubit2pbit_ext(l2_data, 0, conv, 0, 184, 1); return 0; } /*! convenience wrapper for encoding to coded bits * \param[out] cB caller-allocated buffer for 456 coded bits as per TS 05.03 4.1.3 * \param[in] l2_data to-be-encoded L2 Frame * \returns 0 */ static int _xcch_encode_cB(ubit_t *cB, const uint8_t *l2_data) { ubit_t conv[224]; osmo_pbit2ubit_ext(conv, 0, l2_data, 0, 184, 1); osmo_crc64gen_set_bits(&gsm0503_fire_crc40, conv, 184, conv + 184); osmo_conv_encode(&gsm0503_xcch, conv, cB); return 0; } /* * GSM xCCH block transcoding */ /*! Decoding of xCCH data from bursts to L2 frame * \param[out] l2_data caller-allocated output data buffer * \param[in] bursts four GSM bursts in soft-bits * \param[out] n_errors Number of detected errors * \param[out] n_bits_total Number of total coded bits */ int gsm0503_xcch_decode(uint8_t *l2_data, const sbit_t *bursts, int *n_errors, int *n_bits_total) { sbit_t iB[456], cB[456]; int i; for (i = 0; i < 4; i++) gsm0503_xcch_burst_unmap(&iB[i * 114], &bursts[i * 116], NULL, NULL); gsm0503_xcch_deinterleave(cB, iB); return _xcch_decode_cB(l2_data, cB, n_errors, n_bits_total); } /*! Encoding of xCCH data from L2 frame to bursts * \param[out] bursts caller-allocated burst data (unpacked bits) * \param[in] l2_data L2 input data (MAC block) * \returns 0 */ int gsm0503_xcch_encode(ubit_t *bursts, const uint8_t *l2_data) { ubit_t iB[456], cB[456], hl = 1, hn = 1; int i; _xcch_encode_cB(cB, l2_data); gsm0503_xcch_interleave(cB, iB); for (i = 0; i < 4; i++) gsm0503_xcch_burst_map(&iB[i * 114], &bursts[i * 116], &hl, &hn); return 0; } /* * EGPRS PDTCH UL block decoding */ /* * Type 3 - MCS-1,2,3,4 * Unmapping and deinterleaving */ static int egprs_type3_unmap(const sbit_t *bursts, sbit_t *hc, sbit_t *dc) { int i; sbit_t iB[456], q[8]; for (i = 0; i < 4; i++) { gsm0503_xcch_burst_unmap(&iB[i * 114], &bursts[i * 116], q + i * 2, q + i * 2 + 1); } gsm0503_mcs1_ul_deinterleave(hc, dc, iB); return 0; } /* * Type 2 - MCS-5,6 * Unmapping and deinterleaving */ static int egprs_type2_unmap(const sbit_t *bursts, sbit_t *hc, sbit_t *dc) { int i; sbit_t burst[348]; sbit_t hi[EGPRS_HDR_HC_MAX]; sbit_t di[EGPRS_DATA_DC_MAX]; for (i = 0; i < 4; i++) { memcpy(burst, &bursts[i * 348], 348); gsm0503_mcs5_burst_swap(burst); gsm0503_mcs5_ul_burst_unmap(di, burst, hi, i); } gsm0503_mcs5_ul_deinterleave(hc, dc, hi, di); return 0; } /* * Type 1 - MCS-7,8,9 * Unmapping and deinterleaving - Note that MCS-7 interleaver is unique */ static int egprs_type1_unmap(const sbit_t *bursts, sbit_t *hc, sbit_t *c1, sbit_t *c2, int msc) { int i; sbit_t burst[348]; sbit_t hi[EGPRS_HDR_HC_MAX]; sbit_t di[EGPRS_DATA_C1 * 2]; for (i = 0; i < 4; i++) { memcpy(burst, &bursts[i * 348], 348); gsm0503_mcs5_burst_swap(burst); gsm0503_mcs7_ul_burst_unmap(di, burst, hi, i); } if (msc == EGPRS_MCS7) gsm0503_mcs7_ul_deinterleave(hc, c1, c2, hi, di); else gsm0503_mcs8_ul_deinterleave(hc, c1, c2, hi, di); return 0; } /* * Decode EGPRS UL header section * * 1. Depuncture * 2. Convolutional decoding * 3. CRC check */ static int _egprs_decode_hdr(const sbit_t *hc, int mcs, union gprs_rlc_ul_hdr_egprs *hdr) { sbit_t C[EGPRS_HDR_C_MAX]; ubit_t upp[EGPRS_HDR_UPP_MAX]; int i, j, rc; const struct gsm0503_mcs_code *code; code = &gsm0503_mcs_ul_codes[mcs]; /* Skip depuncturing on MCS-5,6 header */ if ((mcs == EGPRS_MCS5) || (mcs == EGPRS_MCS6)) { memcpy(C, hc, code->hdr_code_len); goto hdr_conv_decode; } if (!code->hdr_punc) { /* Invalid MCS-X header puncture matrix */ return -1; } i = code->hdr_code_len - 1; j = code->hdr_punc_len - 1; for (; i >= 0; i--) { if (!code->hdr_punc[i]) C[i] = hc[j--]; else C[i] = 0; } hdr_conv_decode: osmo_conv_decode_ber(code->hdr_conv, C, upp, NULL, NULL); rc = osmo_crc8gen_check_bits(&gsm0503_mcs_crc8_hdr, upp, code->hdr_len, upp + code->hdr_len); if (rc) return -1; osmo_ubit2pbit_ext((pbit_t *) hdr, 0, upp, 0, code->hdr_len, 1); return 0; } /* * Blind MCS header decoding based on burst length and CRC validation. * Ignore 'q' value coding identification. This approach provides * the strongest chance of header recovery. */ static int egprs_decode_hdr(union gprs_rlc_ul_hdr_egprs *hdr, const sbit_t *bursts, uint16_t nbits) { int rc; sbit_t hc[EGPRS_HDR_HC_MAX]; if (nbits == GSM0503_GPRS_BURSTS_NBITS) { /* MCS-1,2,3,4 */ egprs_type3_unmap(bursts, hc, NULL); rc = _egprs_decode_hdr(hc, EGPRS_MCS1, hdr); if (!rc) return EGPRS_HDR_TYPE3; } else if (nbits == GSM0503_EGPRS_BURSTS_NBITS) { /* MCS-5,6 */ egprs_type2_unmap(bursts, hc, NULL); rc = _egprs_decode_hdr(hc, EGPRS_MCS5, hdr); if (!rc) return EGPRS_HDR_TYPE2; /* MCS-7,8,9 */ egprs_type1_unmap(bursts, hc, NULL, NULL, EGPRS_MCS7); rc = _egprs_decode_hdr(hc, EGPRS_MCS7, hdr); if (!rc) return EGPRS_HDR_TYPE1; } return -1; } /* * Parse EGPRS UL header for coding and puncturing scheme (CPS) * * Type 1 - MCS-7,8,9 * Type 2 - MCS-5,6 * Type 3 - MCS-1,2,3,4 */ static int egprs_parse_ul_cps(struct egprs_cps *cps, union gprs_rlc_ul_hdr_egprs *hdr, int type) { uint8_t bits; switch (type) { case EGPRS_HDR_TYPE1: bits = hdr->type1.cps; break; case EGPRS_HDR_TYPE2: bits = (hdr->type2.cps_lo << 2) | hdr->type2.cps_hi; break; case EGPRS_HDR_TYPE3: bits = (hdr->type3.cps_lo << 2) | hdr->type3.cps_hi; break; default: return -1; } return egprs_get_cps(cps, type, bits); } /* * Decode EGPRS UL data section * * 1. Depuncture * 2. Convolutional decoding * 3. CRC check * 4. Block combining (MCS-7,8,9 only) */ static int egprs_decode_data(uint8_t *l2_data, const sbit_t *c, int mcs, int p, int blk, int *n_errors, int *n_bits_total) { ubit_t u[EGPRS_DATA_U_MAX]; sbit_t C[EGPRS_DATA_C_MAX]; int i, j, rc, data_len; const struct gsm0503_mcs_code *code; if (blk && mcs < EGPRS_MCS7) { /* Invalid MCS-X block state */ return -1; } code = &gsm0503_mcs_ul_codes[mcs]; if (!code->data_punc[p]) { /* Invalid MCS-X data puncture matrix */ return -1; } /* * MCS-1,6 - single block processing * MCS-7,9 - dual block processing */ if (mcs >= EGPRS_MCS7) data_len = code->data_len / 2; else data_len = code->data_len; i = code->data_code_len - 1; j = code->data_punc_len - 1; for (; i >= 0; i--) { if (!code->data_punc[p][i]) C[i] = c[j--]; else C[i] = 0; } osmo_conv_decode_ber_punctured(code->data_conv, C, u, n_errors, n_bits_total, code->data_punc[p]); rc = osmo_crc16gen_check_bits(&gsm0503_mcs_crc12, u, data_len, u + data_len); if (rc) return -1; /* Offsets output pointer on the second block of Type 1 MCS */ osmo_ubit2pbit_ext(l2_data, code->hdr_len + blk * data_len, u, 0, data_len, 1); /* Return the number of bytes required for the bit message */ return OSMO_BYTES_FOR_BITS(code->hdr_len + code->data_len); } /*! Decode EGPRS UL message * 1. Header section decoding * 2. Extract CPS settings * 3. Burst unmapping and deinterleaving * 4. Data section decoding * \param[out] l2_data caller-allocated buffer for L2 Frame * \param[in] bursts burst input data as soft unpacked bits * \param[in] nbits number of bits in \a bursts * \param usf_p Uplink State Flag, FIXME: not implemented * \param[out] n_errors number of detected bit-errors * \param[out] n_bits_total total number of decoded bits * \returns number of bytes decoded; negative on error */ int gsm0503_pdtch_egprs_decode(uint8_t *l2_data, const sbit_t *bursts, uint16_t nbits, uint8_t *usf_p, int *n_errors, int *n_bits_total) { sbit_t dc[EGPRS_DATA_DC_MAX]; sbit_t c1[EGPRS_DATA_C1], c2[EGPRS_DATA_C2]; int type, rc; struct egprs_cps cps; union gprs_rlc_ul_hdr_egprs *hdr; if (n_errors) *n_errors = 0; if (n_bits_total) *n_bits_total = 0; if ((nbits != GSM0503_GPRS_BURSTS_NBITS) && (nbits != GSM0503_EGPRS_BURSTS_NBITS)) { /* Invalid EGPRS bit length */ return -EOVERFLOW; } hdr = (union gprs_rlc_ul_hdr_egprs *) l2_data; type = egprs_decode_hdr(hdr, bursts, nbits); if (egprs_parse_ul_cps(&cps, hdr, type) < 0) return -EIO; switch (cps.mcs) { case EGPRS_MCS0: return -ENOTSUP; case EGPRS_MCS1: case EGPRS_MCS2: case EGPRS_MCS3: case EGPRS_MCS4: egprs_type3_unmap(bursts, NULL, dc); break; case EGPRS_MCS5: case EGPRS_MCS6: egprs_type2_unmap(bursts, NULL, dc); break; case EGPRS_MCS7: case EGPRS_MCS8: case EGPRS_MCS9: egprs_type1_unmap(bursts, NULL, c1, c2, cps.mcs); break; default: /* Invalid MCS-X */ return -EINVAL; } /* Decode MCS-X block, where X = cps.mcs */ if (cps.mcs < EGPRS_MCS7) { rc = egprs_decode_data(l2_data, dc, cps.mcs, cps.p[0], 0, n_errors, n_bits_total); if (rc < 0) return -EFAULT; } else { /* Bit counters for the second block */ int n_errors2, n_bits_total2; /* MCS-7,8,9 block 1 */ rc = egprs_decode_data(l2_data, c1, cps.mcs, cps.p[0], 0, n_errors, n_bits_total); if (rc < 0) return -EFAULT; /* MCS-7,8,9 block 2 */ rc = egprs_decode_data(l2_data, c2, cps.mcs, cps.p[1], 1, &n_errors2, &n_bits_total2); if (n_errors) *n_errors += n_errors2; if (n_bits_total) *n_bits_total += n_bits_total2; if (rc < 0) return -EFAULT; } return rc; } /* * GSM PDTCH block transcoding */ /*! Decode GPRS PDTCH * \param[out] l2_data caller-allocated buffer for L2 Frame * \param[in] bursts burst input data as soft unpacked bits * \param[out] usf_p Uplink State Flag, only relevant for DL blocks * \param[out] n_errors number of detected bit-errors * \param[out] n_bits_total total number of decoded bits * \returns number of bytes decoded; negative on error */ int gsm0503_pdtch_decode(uint8_t *l2_data, const sbit_t *bursts, uint8_t *usf_p, int *n_errors, int *n_bits_total) { sbit_t iB[456], cB[676], hl_hn[8]; ubit_t conv[456]; int i, j, k, rv, best = 0, cs = 0, usf = 0; /* make GCC happy */ for (i = 0; i < 4; i++) gsm0503_xcch_burst_unmap(&iB[i * 114], &bursts[i * 116], hl_hn + i * 2, hl_hn + i * 2 + 1); for (i = 0; i < 4; i++) { for (j = 0, k = 0; j < 8; j++) k += abs(((int)gsm0503_pdtch_hl_hn_sbit[i][j]) - ((int)hl_hn[j])); if (i == 0 || k < best) { best = k; cs = i + 1; } } gsm0503_xcch_deinterleave(cB, iB); switch (cs) { case 1: osmo_conv_decode_ber(&gsm0503_xcch, cB, conv, n_errors, n_bits_total); /* the three USF bits d(0),d(1),d(2) are *not* precoded */ if (usf_p) *usf_p = (conv[0] << 2) | (conv[1] << 1) | (conv[2] << 0); rv = osmo_crc64gen_check_bits(&gsm0503_fire_crc40, conv, 184, conv + 184); if (rv) return -1; osmo_ubit2pbit_ext(l2_data, 0, conv, 0, 184, 1); return 23; case 2: /* reorder, set punctured bits to 0 (unknown state) */ for (i = 587, j = 455; i >= 0; i--) { if (!gsm0503_puncture_cs2[i]) cB[i] = cB[j--]; else cB[i] = 0; } /* decode as if puncturing was not employed (note '_np') */ osmo_conv_decode_ber_punctured(&gsm0503_cs2_np, cB, conv, n_errors, NULL, gsm0503_puncture_cs2); /* indicate the actual amount of coded bits (excluding punctured ones) */ if (n_bits_total != NULL) *n_bits_total = 456; /* 5.1.2.2 a) the three USF bits d(0),d(1),d(2) are precoded into six bits */ for (i = 0; i < 8; i++) { for (j = 0, k = 0; j < 6; j++) k += abs(((int)gsm0503_usf2six[i][j]) - ((int)conv[j])); if (i == 0 || k < best) { best = k; usf = i; } } conv[3] = usf & 1; conv[4] = (usf >> 1) & 1; conv[5] = (usf >> 2) & 1; if (usf_p) *usf_p = usf; rv = osmo_crc16gen_check_bits(&gsm0503_cs234_crc16, conv + 3, 271, conv + 3 + 271); if (rv) return -1; osmo_ubit2pbit_ext(l2_data, 0, conv, 3, 271, 1); return 34; case 3: /* reorder, set punctured bits to 0 (unknown state) */ for (i = 675, j = 455; i >= 0; i--) { if (!gsm0503_puncture_cs3[i]) cB[i] = cB[j--]; else cB[i] = 0; } /* decode as if puncturing was not employed (note '_np') */ osmo_conv_decode_ber_punctured(&gsm0503_cs3_np, cB, conv, n_errors, NULL, gsm0503_puncture_cs3); /* indicate the actual amount of coded bits (excluding punctured ones) */ if (n_bits_total != NULL) *n_bits_total = 456; /* 5.1.3.2 a) the three USF bits d(0),d(1),d(2) are precoded into six bits */ for (i = 0; i < 8; i++) { for (j = 0, k = 0; j < 6; j++) k += abs(((int)gsm0503_usf2six[i][j]) - ((int)conv[j])); if (i == 0 || k < best) { best = k; usf = i; } } conv[3] = usf & 1; conv[4] = (usf >> 1) & 1; conv[5] = (usf >> 2) & 1; if (usf_p) *usf_p = usf; rv = osmo_crc16gen_check_bits(&gsm0503_cs234_crc16, conv + 3, 315, conv + 3 + 315); if (rv) return -1; osmo_ubit2pbit_ext(l2_data, 0, conv, 3, 315, 1); return 40; case 4: for (i = 12; i < 456; i++) conv[i] = (cB[i] < 0) ? 1 : 0; /* 5.1.4.2 a) the three USF bits d(0),d(1),d(2) are precoded into twelve bits */ for (i = 0; i < 8; i++) { for (j = 0, k = 0; j < 12; j++) k += abs(((int)gsm0503_usf2twelve_sbit[i][j]) - ((int)cB[j])); if (i == 0 || k < best) { best = k; usf = i; } } conv[9] = usf & 1; conv[10] = (usf >> 1) & 1; conv[11] = (usf >> 2) & 1; if (usf_p) *usf_p = usf; rv = osmo_crc16gen_check_bits(&gsm0503_cs234_crc16, conv + 9, 431, conv + 9 + 431); if (rv) { *n_bits_total = 456 - 12; *n_errors = *n_bits_total; return -1; } *n_bits_total = 456 - 12; *n_errors = 0; osmo_ubit2pbit_ext(l2_data, 0, conv, 9, 431, 1); return 54; default: *n_bits_total = 0; *n_errors = 0; break; } return -1; } /* * EGPRS PDTCH DL block encoding */ static int egprs_type3_map(ubit_t *bursts, const ubit_t *hc, const ubit_t *dc, int usf) { int i; ubit_t iB[456]; const ubit_t *hl_hn = gsm0503_pdtch_hl_hn_ubit[3]; gsm0503_mcs1_dl_interleave(gsm0503_usf2twelve_ubit[usf], hc, dc, iB); for (i = 0; i < 4; i++) { gsm0503_xcch_burst_map(&iB[i * 114], &bursts[i * 116], hl_hn + i * 2, hl_hn + i * 2 + 1); } return 0; } static int egprs_type2_map(ubit_t *bursts, const ubit_t *hc, const ubit_t *dc, int usf) { int i; const ubit_t *up; ubit_t hi[EGPRS_HDR_HC_MAX]; ubit_t di[EGPRS_DATA_DC_MAX]; gsm0503_mcs5_dl_interleave(hc, dc, hi, di); up = gsm0503_mcs5_usf_precode_table[usf]; for (i = 0; i < 4; i++) { gsm0503_mcs5_dl_burst_map(di, &bursts[i * 348], hi, up, i); gsm0503_mcs5_burst_swap((sbit_t *) &bursts[i * 348]); } return 0; } static int egprs_type1_map(ubit_t *bursts, const ubit_t *hc, const ubit_t *c1, const ubit_t *c2, int usf, int mcs) { int i; const ubit_t *up; ubit_t hi[EGPRS_HDR_HC_MAX]; ubit_t di[EGPRS_DATA_C1 * 2]; if (mcs == EGPRS_MCS7) gsm0503_mcs7_dl_interleave(hc, c1, c2, hi, di); else gsm0503_mcs8_dl_interleave(hc, c1, c2, hi, di); up = gsm0503_mcs5_usf_precode_table[usf]; for (i = 0; i < 4; i++) { gsm0503_mcs7_dl_burst_map(di, &bursts[i * 348], hi, up, i); gsm0503_mcs5_burst_swap((sbit_t *) &bursts[i * 348]); } return 0; } static int egprs_encode_hdr(ubit_t *hc, const uint8_t *l2_data, int mcs) { int i, j; ubit_t upp[EGPRS_HDR_UPP_MAX], C[EGPRS_HDR_C_MAX]; const struct gsm0503_mcs_code *code; code = &gsm0503_mcs_dl_codes[mcs]; osmo_pbit2ubit_ext(upp, 0, l2_data, code->usf_len, code->hdr_len, 1); osmo_crc8gen_set_bits(&gsm0503_mcs_crc8_hdr, upp, code->hdr_len, upp + code->hdr_len); osmo_conv_encode(code->hdr_conv, upp, C); /* MCS-5,6 header direct puncture instead of table */ if ((mcs == EGPRS_MCS5) || (mcs == EGPRS_MCS6)) { memcpy(hc, C, code->hdr_code_len); hc[99] = hc[98]; return 0; } if (!code->hdr_punc) { /* Invalid MCS-X header puncture matrix */ return -1; } for (i = 0, j = 0; i < code->hdr_code_len; i++) { if (!code->hdr_punc[i]) hc[j++] = C[i]; } return 0; } static int egprs_encode_data(ubit_t *c, const uint8_t *l2_data, int mcs, int p, int blk) { int i, j, data_len; ubit_t u[EGPRS_DATA_U_MAX], C[EGPRS_DATA_C_MAX]; const struct gsm0503_mcs_code *code; code = &gsm0503_mcs_dl_codes[mcs]; /* * Dual block - MCS-7,8,9 * Single block - MCS-1,2,3,4,5,6 */ if (mcs >= EGPRS_MCS7) data_len = code->data_len / 2; else data_len = code->data_len; osmo_pbit2ubit_ext(u, 0, l2_data, code->usf_len + code->hdr_len + blk * data_len, data_len, 1); osmo_crc16gen_set_bits(&gsm0503_mcs_crc12, u, data_len, u + data_len); osmo_conv_encode(code->data_conv, u, C); if (!code->data_punc[p]) { /* Invalid MCS-X data puncture matrix */ return -1; } for (i = 0, j = 0; i < code->data_code_len; i++) { if (!code->data_punc[p][i]) c[j++] = C[i]; } return 0; } /* * Parse EGPRS DL header for coding and puncturing scheme (CPS) * * Type 1 - MCS-7,8,9 * Type 2 - MCS-5,6 * Type 3 - MCS-1,2,3,4 */ static int egprs_parse_dl_cps(struct egprs_cps *cps, const union gprs_rlc_dl_hdr_egprs *hdr, int type) { uint8_t bits; switch (type) { case EGPRS_HDR_TYPE1: bits = hdr->type1.cps; break; case EGPRS_HDR_TYPE2: bits = hdr->type2.cps; break; case EGPRS_HDR_TYPE3: bits = hdr->type3.cps; break; default: return -1; } return egprs_get_cps(cps, type, bits); } /*! EGPRS DL message encoding * \param[out] bursts caller-allocated buffer for unpacked burst bits * \param[in] l2_data L2 (MAC) block to be encoded * \param[in] l2_len length of l2_data in bytes, used to determine MCS * \returns number of bits encoded; negative on error */ int gsm0503_pdtch_egprs_encode(ubit_t *bursts, const uint8_t *l2_data, uint8_t l2_len) { ubit_t hc[EGPRS_DATA_C_MAX], dc[EGPRS_DATA_DC_MAX]; ubit_t c1[EGPRS_DATA_C1], c2[EGPRS_DATA_C2]; uint8_t mcs; struct egprs_cps cps; union gprs_rlc_dl_hdr_egprs *hdr; switch (l2_len) { case 27: mcs = EGPRS_MCS1; break; case 33: mcs = EGPRS_MCS2; break; case 42: mcs = EGPRS_MCS3; break; case 49: mcs = EGPRS_MCS4; break; case 60: mcs = EGPRS_MCS5; break; case 78: mcs = EGPRS_MCS6; break; case 118: mcs = EGPRS_MCS7; break; case 142: mcs = EGPRS_MCS8; break; case 154: mcs = EGPRS_MCS9; break; default: return -1; } /* Read header for USF and puncturing matrix selection. */ hdr = (union gprs_rlc_dl_hdr_egprs *) l2_data; switch (mcs) { case EGPRS_MCS1: case EGPRS_MCS2: case EGPRS_MCS3: case EGPRS_MCS4: /* Check for valid CPS and matching MCS to message size */ if ((egprs_parse_dl_cps(&cps, hdr, EGPRS_HDR_TYPE3) < 0) || (cps.mcs != mcs)) goto bad_header; egprs_encode_hdr(hc, l2_data, mcs); egprs_encode_data(dc, l2_data, mcs, cps.p[0], 0); egprs_type3_map(bursts, hc, dc, hdr->type3.usf); break; case EGPRS_MCS5: case EGPRS_MCS6: if ((egprs_parse_dl_cps(&cps, hdr, EGPRS_HDR_TYPE2) < 0) || (cps.mcs != mcs)) goto bad_header; egprs_encode_hdr(hc, l2_data, mcs); egprs_encode_data(dc, l2_data, mcs, cps.p[0], 0); egprs_type2_map(bursts, hc, dc, hdr->type2.usf); break; case EGPRS_MCS7: case EGPRS_MCS8: case EGPRS_MCS9: if ((egprs_parse_dl_cps(&cps, hdr, EGPRS_HDR_TYPE1) < 0) || (cps.mcs != mcs)) goto bad_header; egprs_encode_hdr(hc, l2_data, mcs); egprs_encode_data(c1, l2_data, mcs, cps.p[0], 0); egprs_encode_data(c2, l2_data, mcs, cps.p[1], 1); egprs_type1_map(bursts, hc, c1, c2, hdr->type1.usf, mcs); break; } return mcs >= EGPRS_MCS5 ? GSM0503_EGPRS_BURSTS_NBITS : GSM0503_GPRS_BURSTS_NBITS; bad_header: /* Invalid EGPRS MCS-X header */ return -1; } /*! GPRS DL message encoding * \param[out] bursts caller-allocated buffer for unpacked burst bits * \param[in] l2_data L2 (MAC) block to be encoded * \param[in] l2_len length of l2_data in bytes, used to determine CS * \returns number of bits encoded; negative on error */ int gsm0503_pdtch_encode(ubit_t *bursts, const uint8_t *l2_data, uint8_t l2_len) { ubit_t iB[456], cB[676]; const ubit_t *hl_hn; ubit_t conv[334]; int i, j, usf; switch (l2_len) { case 23: osmo_pbit2ubit_ext(conv, 0, l2_data, 0, 184, 1); osmo_crc64gen_set_bits(&gsm0503_fire_crc40, conv, 184, conv + 184); osmo_conv_encode(&gsm0503_xcch, conv, cB); hl_hn = gsm0503_pdtch_hl_hn_ubit[0]; break; case 34: osmo_pbit2ubit_ext(conv, 3, l2_data, 0, 271, 1); usf = l2_data[0] & 0x7; osmo_crc16gen_set_bits(&gsm0503_cs234_crc16, conv + 3, 271, conv + 3 + 271); memcpy(conv, gsm0503_usf2six[usf], 6); osmo_conv_encode(&gsm0503_cs2_np, conv, cB); for (i = 0, j = 0; i < 588; i++) if (!gsm0503_puncture_cs2[i]) cB[j++] = cB[i]; hl_hn = gsm0503_pdtch_hl_hn_ubit[1]; break; case 40: osmo_pbit2ubit_ext(conv, 3, l2_data, 0, 315, 1); usf = l2_data[0] & 0x7; osmo_crc16gen_set_bits(&gsm0503_cs234_crc16, conv + 3, 315, conv + 3 + 315); memcpy(conv, gsm0503_usf2six[usf], 6); osmo_conv_encode(&gsm0503_cs3_np, conv, cB); for (i = 0, j = 0; i < 676; i++) if (!gsm0503_puncture_cs3[i]) cB[j++] = cB[i]; hl_hn = gsm0503_pdtch_hl_hn_ubit[2]; break; case 54: osmo_pbit2ubit_ext(cB, 9, l2_data, 0, 431, 1); usf = l2_data[0] & 0x7; osmo_crc16gen_set_bits(&gsm0503_cs234_crc16, cB + 9, 431, cB + 9 + 431); memcpy(cB, gsm0503_usf2twelve_ubit[usf], 12); hl_hn = gsm0503_pdtch_hl_hn_ubit[3]; break; default: return -1; } gsm0503_xcch_interleave(cB, iB); for (i = 0; i < 4; i++) { gsm0503_xcch_burst_map(&iB[i * 114], &bursts[i * 116], hl_hn + i * 2, hl_hn + i * 2 + 1); } return GSM0503_GPRS_BURSTS_NBITS; } /* * GSM TCH/F FR/EFR transcoding */ /*! assemble a FR codec frame in format as used inside RTP * \param[out] tch_data Codec frame in RTP format * \param[in] b_bits Codec frame in 'native' format * \param[in] net_order FIXME */ static void tch_fr_reassemble(uint8_t *tch_data, const ubit_t *b_bits, int net_order) { int i, j, k, l, o; tch_data[0] = 0xd << 4; memset(tch_data + 1, 0, 32); if (net_order) { for (i = 0, j = 4; i < 260; i++, j++) tch_data[j >> 3] |= (b_bits[i] << (7 - (j & 7))); return; } /* reassemble d-bits */ i = 0; /* counts bits */ j = 4; /* counts output bits */ k = gsm0503_gsm_fr_map[0]-1; /* current number bit in element */ l = 0; /* counts element bits */ o = 0; /* offset input bits */ while (i < 260) { tch_data[j >> 3] |= (b_bits[k + o] << (7 - (j & 7))); if (--k < 0) { o += gsm0503_gsm_fr_map[l]; k = gsm0503_gsm_fr_map[++l]-1; } i++; j++; } } static void tch_fr_disassemble(ubit_t *b_bits, const uint8_t *tch_data, int net_order) { int i, j, k, l, o; if (net_order) { for (i = 0, j = 4; i < 260; i++, j++) b_bits[i] = (tch_data[j >> 3] >> (7 - (j & 7))) & 1; return; } i = 0; /* counts bits */ j = 4; /* counts input bits */ k = gsm0503_gsm_fr_map[0] - 1; /* current number bit in element */ l = 0; /* counts element bits */ o = 0; /* offset output bits */ while (i < 260) { b_bits[k + o] = (tch_data[j >> 3] >> (7 - (j & 7))) & 1; if (--k < 0) { o += gsm0503_gsm_fr_map[l]; k = gsm0503_gsm_fr_map[++l] - 1; } i++; j++; } } /* assemble a HR codec frame in the canonical format of ETSI TS 101 318 */ static void tch_hr_reassemble(uint8_t *tch_data, const ubit_t *b_bits) { int i; memset(tch_data, 0, GSM_HR_BYTES); for (i = 0; i < 112; i++) tch_data[i >> 3] |= (b_bits[i] << (7 - (i & 7))); } static void tch_hr_disassemble(ubit_t *b_bits, const uint8_t *tch_data) { int i; for (i = 0; i < 112; i++) b_bits[i] = (tch_data[i >> 3] >> (7 - (i & 7))) & 1; } /* assemble a EFR codec frame in format as used inside RTP */ static void tch_efr_reassemble(uint8_t *tch_data, const ubit_t *b_bits) { int i, j; tch_data[0] = 0xc << 4; memset(tch_data + 1, 0, 30); for (i = 0, j = 4; i < 244; i++, j++) tch_data[j >> 3] |= (b_bits[i] << (7 - (j & 7))); } static void tch_efr_disassemble(ubit_t *b_bits, const uint8_t *tch_data) { int i, j; for (i = 0, j = 4; i < 244; i++, j++) b_bits[i] = (tch_data[j >> 3] >> (7 - (j & 7))) & 1; } /* assemble a AMR codec frame in format as used inside RTP */ static void tch_amr_reassemble(uint8_t *tch_data, const ubit_t *d_bits, int len) { int i, j; memset(tch_data, 0, (len + 7) >> 3); for (i = 0, j = 0; i < len; i++, j++) tch_data[j >> 3] |= (d_bits[i] << (7 - (j & 7))); } static void tch_amr_disassemble(ubit_t *d_bits, const uint8_t *tch_data, int len) { int i, j; for (i = 0, j = 0; i < len; i++, j++) d_bits[i] = (tch_data[j >> 3] >> (7 - (j & 7))) & 1; } /* Append STI and MI bits to the SID_UPDATE frame, see also * 3GPP TS 26.101, chapter 4.2.3 AMR Core Frame with comfort noise bits */ static void tch_amr_sid_update_append(ubit_t *sid_update, uint8_t sti, uint8_t mi) { /* Zero out the space that had been used by the CRC14 */ memset(sid_update + 35, 0, 14); /* Append STI and MI parameters */ sid_update[35] = sti & 1; sid_update[36] = mi & 1; sid_update[37] = mi >> 1 & 1; sid_update[38] = mi >> 2 & 1; } /* Extract a SID UPDATE fram the sbits of an FR AMR frame */ static void extract_afs_sid_update(sbit_t *sid_update, const sbit_t *sbits) { unsigned int i; sbits += 32; for (i = 0; i < 53; i++) { sid_update[0] = sbits[0]; sid_update[1] = sbits[1]; sid_update[2] = sbits[2]; sid_update[3] = sbits[3]; sid_update += 4; sbits += 8; } } /* re-arrange according to TS 05.03 Table 2 (receiver) */ static void tch_fr_d_to_b(ubit_t *b_bits, const ubit_t *d_bits) { int i; for (i = 0; i < 260; i++) b_bits[gsm610_bitorder[i]] = d_bits[i]; } /* re-arrange according to TS 05.03 Table 2 (transmitter) */ static void tch_fr_b_to_d(ubit_t *d_bits, const ubit_t *b_bits) { int i; for (i = 0; i < 260; i++) d_bits[i] = b_bits[gsm610_bitorder[i]]; } /* re-arrange according to TS 05.03 Table 3a (receiver) */ static void tch_hr_d_to_b(ubit_t *b_bits, const ubit_t *d_bits) { int i; const uint16_t *map; if (!d_bits[93] && !d_bits[94]) map = gsm620_unvoiced_bitorder; else map = gsm620_voiced_bitorder; for (i = 0; i < 112; i++) b_bits[map[i]] = d_bits[i]; } /* re-arrange according to TS 05.03 Table 3a (transmitter) */ static void tch_hr_b_to_d(ubit_t *d_bits, const ubit_t *b_bits) { int i; const uint16_t *map; if (!b_bits[34] && !b_bits[35]) map = gsm620_unvoiced_bitorder; else map = gsm620_voiced_bitorder; for (i = 0; i < 112; i++) d_bits[i] = b_bits[map[i]]; } /* re-arrange according to TS 05.03 Table 6 (receiver) */ static void tch_efr_d_to_w(ubit_t *b_bits, const ubit_t *d_bits) { int i; for (i = 0; i < 260; i++) b_bits[gsm660_bitorder[i]] = d_bits[i]; } /* re-arrange according to TS 05.03 Table 6 (transmitter) */ static void tch_efr_w_to_d(ubit_t *d_bits, const ubit_t *b_bits) { int i; for (i = 0; i < 260; i++) d_bits[i] = b_bits[gsm660_bitorder[i]]; } /* extract the 65 protected class1a+1b bits */ static void tch_efr_protected(const ubit_t *s_bits, ubit_t *b_bits) { int i; for (i = 0; i < 65; i++) b_bits[i] = s_bits[gsm0503_gsm_efr_protected_bits[i] - 1]; } static void tch_fr_unreorder(ubit_t *d, ubit_t *p, const ubit_t *u) { int i; for (i = 0; i < 91; i++) { d[i << 1] = u[i]; d[(i << 1) + 1] = u[184 - i]; } for (i = 0; i < 3; i++) p[i] = u[91 + i]; } static void tch_fr_reorder(ubit_t *u, const ubit_t *d, const ubit_t *p) { int i; for (i = 0; i < 91; i++) { u[i] = d[i << 1]; u[184 - i] = d[(i << 1) + 1]; } for (i = 0; i < 3; i++) u[91 + i] = p[i]; } static void tch_hr_unreorder(ubit_t *d, ubit_t *p, const ubit_t *u) { memcpy(d, u, 95); memcpy(p, u + 95, 3); } static void tch_hr_reorder(ubit_t *u, const ubit_t *d, const ubit_t *p) { memcpy(u, d, 95); memcpy(u + 95, p, 3); } static void tch_efr_reorder(ubit_t *w, const ubit_t *s, const ubit_t *p) { memcpy(w, s, 71); w[71] = w[72] = s[69]; memcpy(w + 73, s + 71, 50); w[123] = w[124] = s[119]; memcpy(w + 125, s + 121, 53); w[178] = w[179] = s[172]; memcpy(w + 180, s + 174, 50); w[230] = w[231] = s[222]; memcpy(w + 232, s + 224, 20); memcpy(w + 252, p, 8); } static void tch_efr_unreorder(ubit_t *s, ubit_t *p, const ubit_t *w) { int sum; memcpy(s, w, 71); sum = s[69] + w[71] + w[72]; s[69] = (sum >= 2); memcpy(s + 71, w + 73, 50); sum = s[119] + w[123] + w[124]; s[119] = (sum >= 2); memcpy(s + 121, w + 125, 53); sum = s[172] + w[178] + w[179]; s[172] = (sum >= 2); memcpy(s + 174, w + 180, 50); sum = s[222] + w[230] + w[231]; s[222] = (sum >= 2); memcpy(s + 224, w + 232, 20); memcpy(p, w + 252, 8); } static void tch_amr_merge(ubit_t *u, const ubit_t *d, const ubit_t *p, int len, int prot) { memcpy(u, d, prot); memcpy(u + prot, p, 6); memcpy(u + prot + 6, d + prot, len - prot); } static void tch_amr_unmerge(ubit_t *d, ubit_t *p, const ubit_t *u, int len, int prot) { memcpy(d, u, prot); memcpy(p, u + prot, 6); memcpy(d + prot, u + prot + 6, len - prot); } /*! Perform channel decoding of a FR/EFR channel according TS 05.03 * \param[out] tch_data Codec frame in RTP payload format * \param[in] bursts buffer containing the symbols of 8 bursts * \param[in] net_order FIXME * \param[in] efr Is this channel using EFR (1) or FR (0) * \param[out] n_errors Number of detected bit errors * \param[out] n_bits_total Total number of bits * \returns length of bytes used in \a tch_data output buffer; negative on error */ int gsm0503_tch_fr_decode(uint8_t *tch_data, const sbit_t *bursts, int net_order, int efr, int *n_errors, int *n_bits_total) { sbit_t iB[912], cB[456], h; ubit_t conv[185], s[244], w[260], b[65], d[260], p[8]; int i, rv, len, steal = 0; /* map from 8 bursts to interleaved data bits (iB) */ for (i = 0; i < 8; i++) { gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], &h, i >> 2); steal -= h; } /* we now have the bits of the four bursts (interface 4 in * Figure 1a of TS 05.03 */ gsm0503_tch_fr_deinterleave(cB, iB); /* we now have the coded bits c(B): interface 3 in Fig. 1a */ if (steal > 0) { rv = _xcch_decode_cB(tch_data, cB, n_errors, n_bits_total); if (rv) { /* Error decoding FACCH frame */ return -1; } return GSM_MACBLOCK_LEN; } osmo_conv_decode_ber(&gsm0503_tch_fr, cB, conv, n_errors, n_bits_total); /* we now have the data bits 'u': interface 2 in Fig. 1a */ /* input: 'conv', output: d[ata] + p[arity] */ tch_fr_unreorder(d, p, conv); for (i = 0; i < 78; i++) d[i + 182] = (cB[i + 378] < 0) ? 1 : 0; /* check if parity of first 50 (class 1) 'd'-bits match 'p' */ rv = osmo_crc8gen_check_bits(&gsm0503_tch_fr_crc3, d, 50, p); if (rv) { /* Error checking CRC8 for the FR part of an EFR/FR frame */ return -1; } if (efr) { tch_efr_d_to_w(w, d); /* we now have the preliminary-coded bits w(k) */ tch_efr_unreorder(s, p, w); /* we now have the data delivered to the preliminary * channel encoding unit s(k) */ /* extract the 65 most important bits according TS 05.03 3.1.1.1 */ tch_efr_protected(s, b); /* perform CRC-8 on 65 most important bits (50 bits of * class 1a + 15 bits of class 1b) */ rv = osmo_crc8gen_check_bits(&gsm0503_tch_efr_crc8, b, 65, p); if (rv) { /* Error checking CRC8 for the EFR part of an EFR frame */ return -1; } tch_efr_reassemble(tch_data, s); len = GSM_EFR_BYTES; } else { tch_fr_d_to_b(w, d); tch_fr_reassemble(tch_data, w, net_order); len = GSM_FR_BYTES; } return len; } /*! Perform channel encoding on a TCH/FS channel according to TS 05.03 * \param[out] bursts caller-allocated output buffer for bursts bits * \param[in] tch_data Codec input data in RTP payload format * \param[in] len Length of \a tch_data in bytes * \param[in] net_order FIXME * \returns 0 in case of success; negative on error */ int gsm0503_tch_fr_encode(ubit_t *bursts, const uint8_t *tch_data, int len, int net_order) { ubit_t iB[912], cB[456], h; ubit_t conv[185], w[260], b[65], s[244], d[260], p[8]; int i; switch (len) { case GSM_EFR_BYTES: /* TCH EFR */ tch_efr_disassemble(s, tch_data); tch_efr_protected(s, b); osmo_crc8gen_set_bits(&gsm0503_tch_efr_crc8, b, 65, p); tch_efr_reorder(w, s, p); tch_efr_w_to_d(d, w); goto coding_efr_fr; case GSM_FR_BYTES: /* TCH FR */ tch_fr_disassemble(w, tch_data, net_order); tch_fr_b_to_d(d, w); coding_efr_fr: osmo_crc8gen_set_bits(&gsm0503_tch_fr_crc3, d, 50, p); tch_fr_reorder(conv, d, p); memcpy(cB + 378, d + 182, 78); osmo_conv_encode(&gsm0503_tch_fr, conv, cB); h = 0; break; case 0: /* no data, induce BFI in the receiver */ /* Do the same thing that sysmoBTS PHY does when fed a 0-length * payload for DL: set all u(k) bits to 0, and do the same * with all class 2 bits. This operation is NOT the same as * an FR codec frame of all zero bits: with all-zeros d(k) input * the CRC3 function will produce 111 output, whereas we * transmit 000 in those parity bits too. The result will be * an induced BFI (bad frame indication) condition in the * receiver, for both TCH/FS and TCH/EFS decoders. */ memset(conv, 0, sizeof(conv)); memset(cB + 378, 0, 78); osmo_conv_encode(&gsm0503_tch_fr, conv, cB); h = 0; break; case GSM_MACBLOCK_LEN: /* FACCH */ _xcch_encode_cB(cB, tch_data); h = 1; break; default: return -1; } gsm0503_tch_fr_interleave(cB, iB); for (i = 0; i < 8; i++) { gsm0503_tch_burst_map(&iB[i * 114], &bursts[i * 116], &h, i >> 2); } return 0; } /*! Perform channel decoding of a HR(v1) channel according TS 05.03 * \param[out] tch_data Codec frame in TS 101 318 canonical format * \param[in] bursts buffer containing the symbols of 6 bursts * \param[in] odd Odd (1) or even (0) frame number * \param[out] n_errors Number of detected bit errors * \param[out] n_bits_total Total number of bits * \returns length of bytes used in \a tch_data output buffer; negative on error */ int gsm0503_tch_hr_decode2(uint8_t *tch_data, const sbit_t *bursts, int odd, int *n_errors, int *n_bits_total) { sbit_t iB[912], cB[456], h; ubit_t conv[98], b[112], d[112], p[3]; int i, rv, steal = 0; /* Only unmap the stealing bits */ if (!odd) { for (i = 0; i < 4; i++) { gsm0503_tch_burst_unmap(NULL, &bursts[i * 116], &h, 0); steal -= h; } for (i = 2; i < 6; i++) { gsm0503_tch_burst_unmap(NULL, &bursts[i * 116], &h, 1); steal -= h; } } /* If we found a stole FACCH, but only at correct alignment */ if (steal > 0) { for (i = 0; i < 6; i++) { gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], NULL, i >> 2); } for (i = 2; i < 4; i++) { gsm0503_tch_burst_unmap(&iB[i * 114 + 456], &bursts[i * 116], NULL, 1); } gsm0503_tch_fr_deinterleave(cB, iB); rv = _xcch_decode_cB(tch_data, cB, n_errors, n_bits_total); if (rv) { /* Error decoding FACCH frame */ return -1; } return GSM_MACBLOCK_LEN; } for (i = 0; i < 4; i++) { gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], NULL, i >> 1); } gsm0503_tch_hr_deinterleave(cB, iB); osmo_conv_decode_ber(&gsm0503_tch_hr, cB, conv, n_errors, n_bits_total); tch_hr_unreorder(d, p, conv); for (i = 0; i < 17; i++) d[i + 95] = (cB[i + 211] < 0) ? 1 : 0; rv = osmo_crc8gen_check_bits(&gsm0503_tch_fr_crc3, d + 73, 22, p); if (rv) { /* Error checking CRC8 for an HR frame */ return -1; } tch_hr_d_to_b(b, d); tch_hr_reassemble(tch_data, b); return GSM_HR_BYTES; } /*! Perform channel decoding of a HR(v1) channel according TS 05.03, * deprecated legacy API. * \param[out] tch_data Codec frame in pseudo-RFC5993 format * \param[in] bursts buffer containing the symbols of 6 bursts * \param[in] odd Odd (1) or even (0) frame number * \param[out] n_errors Number of detected bit errors * \param[out] n_bits_total Total number of bits * \returns length of bytes used in \a tch_data output buffer; negative on error * * The HR1 codec frame format returned by this function is pseudo-RFC5993, * not true RFC 5993, as there is no SID classification being done * and the FT bits in the ToC octet are always set to 0 - but this * arguably-bogus format is the legacy public API. */ int gsm0503_tch_hr_decode(uint8_t *tch_data, const sbit_t *bursts, int odd, int *n_errors, int *n_bits_total) { int rc; rc = gsm0503_tch_hr_decode2(tch_data, bursts, odd, n_errors, n_bits_total); if (rc != GSM_HR_BYTES) return rc; memmove(tch_data + 1, tch_data, GSM_HR_BYTES); tch_data[0] = 0x00; /* FT=0, note absence of SID classification */ return GSM_HR_BYTES_RTP_RFC5993; } /*! Perform channel encoding on a TCH/HS channel according to TS 05.03 * \param[out] bursts caller-allocated output buffer for bursts bits * \param[in] tch_data Codec input data in RTP payload format * \param[in] len Length of \a tch_data in bytes * \returns 0 in case of success; negative on error */ int gsm0503_tch_hr_encode(ubit_t *bursts, const uint8_t *tch_data, int len) { ubit_t iB[912], cB[456], h; ubit_t conv[98], b[112], d[112], p[3]; int i; switch (len) { case GSM_HR_BYTES_RTP_RFC5993: /* TCH HR with RFC 5993 prefix */ tch_data++; /* fall-through */ case GSM_HR_BYTES: /* TCH HR in "pure" form */ tch_hr_disassemble(b, tch_data); tch_hr_b_to_d(d, b); osmo_crc8gen_set_bits(&gsm0503_tch_fr_crc3, d + 73, 22, p); tch_hr_reorder(conv, d, p); memcpy(cB + 211, d + 95, 17); hr_conv_coding: osmo_conv_encode(&gsm0503_tch_hr, conv, cB); h = 0; gsm0503_tch_hr_interleave(cB, iB); for (i = 0; i < 4; i++) { gsm0503_tch_burst_map(&iB[i * 114], &bursts[i * 116], &h, i >> 1); } break; case 0: /* no data, induce BFI in the receiver */ /* see comments in gsm0503_tch_fr_encode() - same deal here */ memset(conv, 0, sizeof(conv)); memset(cB + 211, 0, 17); goto hr_conv_coding; case GSM_MACBLOCK_LEN: /* FACCH */ _xcch_encode_cB(cB, tch_data); h = 1; gsm0503_tch_fr_interleave(cB, iB); for (i = 0; i < 6; i++) { gsm0503_tch_burst_map(&iB[i * 114], &bursts[i * 116], &h, i >> 2); } for (i = 2; i < 4; i++) { gsm0503_tch_burst_map(&iB[i * 114 + 456], &bursts[i * 116], &h, 1); } break; default: return -1; } return 0; } /* TCH/AFS: parse codec ID (CMI or CMC/CMR) from coded in-band data (16 bit) */ static uint8_t gsm0503_tch_afs_decode_inband(const sbit_t *cB) { unsigned int id = 0, best = 0; unsigned int i, j, k; for (i = 0; i < 4; i++) { /* FIXME: why not using remaining (16 - 8) soft-bits here? */ for (j = 0, k = 0; j < 8; j++) k += abs(((int)gsm0503_afs_ic_sbit[i][j]) - ((int)cB[j])); if (i == 0 || k < best) { best = k; id = i; } } return id; } /*! Perform channel decoding of a TCH/AFS channel according TS 05.03 * \param[out] tch_data Codec frame in RTP payload format * \param[in] bursts buffer containing the symbols of 8 bursts * \param[in] codec_mode_req is this CMR (1) or CMC (0) * \param[in] codec array of active codecs (active codec set) * \param[in] codecs number of codecs in \a codec * \param ft Frame Type; Input if \a codec_mode_req = 1, Output * otherwise * \param[out] cmr Output in \a codec_mode_req = 1 * \param[out] n_errors Number of detected bit errors * \param[out] n_bits_total Total number of bits * \returns (>=4) length of bytes used in \a tch_data output buffer; ([0,3]) * codec out of range; negative on error */ int gsm0503_tch_afs_decode(uint8_t *tch_data, const sbit_t *bursts, int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft, uint8_t *cmr, int *n_errors, int *n_bits_total) { return gsm0503_tch_afs_decode_dtx(tch_data, bursts, codec_mode_req, codec, codecs, ft, cmr, n_errors, n_bits_total, NULL); } /*! Perform channel decoding of a TCH/AFS channel according TS 05.03 * \param[out] tch_data Codec frame in RTP payload format * \param[in] bursts buffer containing the symbols of 8 bursts * \param[in] codec_mode_req is this CMR (1) or CMC (0) * \param[in] codec array of active codecs (active codec set) * \param[in] codecs number of codecs in \a codec * \param ft Frame Type; Input if \a codec_mode_req = 1, Output * otherwise * \param[out] cmr Output in \a codec_mode_req = 1 * \param[out] n_errors Number of detected bit errors * \param[out] n_bits_total Total number of bits * \param[inout] dtx DTX frame type output, previous DTX frame type input * \returns (>=4) length of bytes used in \a tch_data output buffer; ([0,3]) * codec out of range; negative on error */ int gsm0503_tch_afs_decode_dtx(uint8_t *tch_data, const sbit_t *bursts, int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft, uint8_t *cmr, int *n_errors, int *n_bits_total, uint8_t *dtx) { sbit_t iB[912], cB[456], h; ubit_t d[244], p[6], conv[250]; int i, rv, len, steal = 0, id = -1; *n_errors = 0; *n_bits_total = 0; static ubit_t sid_first_dummy[64] = { 0 }; sbit_t sid_update_enc[256]; for (i=0; i<8; i++) { gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], &h, i >> 2); steal -= h; } gsm0503_tch_fr_deinterleave(cB, iB); if (steal > 0) { /* If not NULL, dtx indicates type of previously decoded TCH/AFS frame. * It's normally updated by gsm0503_detect_afs_dtx_frame2(), which is not * reached in case of FACCH. Reset it here to avoid FACCH/F frames being * misinterpreted as AMR's special DTX frames. */ if (dtx != NULL) *dtx = AMR_OTHER; rv = _xcch_decode_cB(tch_data, cB, n_errors, n_bits_total); if (rv) { /* Error decoding FACCH frame */ return -1; } return GSM_MACBLOCK_LEN; } /* Determine the DTX frame type (SID_UPDATE, ONSET etc...) */ if (dtx) { const enum gsm0503_amr_dtx_frames dtx_prev = *dtx; *dtx = gsm0503_detect_afs_dtx_frame2(n_errors, n_bits_total, &id, cB); switch (*dtx) { case AMR_OTHER: /* NOTE: The AFS_SID_UPDATE frame is splitted into * two half rate frames. If the id marker frame * (AFS_SID_UPDATE) is detected the following frame * contains the actual comfort noised data part of * (AFS_SID_UPDATE_CN). */ if (dtx_prev != AFS_SID_UPDATE) break; /* TODO: parse CMI _and_ CMC/CMR (16 + 16 bit) */ *dtx = AFS_SID_UPDATE_CN; extract_afs_sid_update(sid_update_enc, cB); osmo_conv_decode_ber(&gsm0503_tch_axs_sid_update, sid_update_enc, conv, n_errors, n_bits_total); rv = osmo_crc16gen_check_bits(&gsm0503_amr_crc14, conv, 35, conv + 35); if (rv != 0) { /* Error checking CRC14 for an AMR SID_UPDATE frame */ return -1; } tch_amr_sid_update_append(conv, 1, (codec_mode_req) ? codec[*ft] : codec[id > 0 ? id : 0]); tch_amr_reassemble(tch_data, conv, 39); len = 5; goto out; case AFS_SID_FIRST: /* TODO: parse CMI or CMC/CMR (16 bit) */ tch_amr_sid_update_append(sid_first_dummy, 0, (codec_mode_req) ? codec[*ft] : codec[id > 0 ? id : 0]); tch_amr_reassemble(tch_data, sid_first_dummy, 39); len = 5; goto out; case AFS_SID_UPDATE: /* TODO: parse CMI _and_ CMC/CMR (16 + 16 bit) */ case AFS_ONSET: len = 0; goto out; default: break; } } /* Parse codec ID (CMI or CMC/CMR) and check if it fits into range of codecs */ if ((id = gsm0503_tch_afs_decode_inband(&cB[0])) >= codecs) { /* Codec mode out of range, return id */ return id; } switch ((codec_mode_req) ? codec[*ft] : codec[id]) { case 7: /* TCH/AFS12.2 */ osmo_conv_decode_ber(&gsm0503_tch_afs_12_2, cB + 8, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 244, 81); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 81, p); if (rv) { /* Error checking CRC8 for an AMR 12.2 frame */ return -1; } tch_amr_reassemble(tch_data, d, 244); len = 31; break; case 6: /* TCH/AFS10.2 */ osmo_conv_decode_ber(&gsm0503_tch_afs_10_2, cB + 8, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 204, 65); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 65, p); if (rv) { /* Error checking CRC8 for an AMR 10.2 frame */ return -1; } tch_amr_reassemble(tch_data, d, 204); len = 26; break; case 5: /* TCH/AFS7.95 */ osmo_conv_decode_ber(&gsm0503_tch_afs_7_95, cB + 8, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 159, 75); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 75, p); if (rv) { /* Error checking CRC8 for an AMR 7.95 frame */ return -1; } tch_amr_reassemble(tch_data, d, 159); len = 20; break; case 4: /* TCH/AFS7.4 */ osmo_conv_decode_ber(&gsm0503_tch_afs_7_4, cB + 8, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 148, 61); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 61, p); if (rv) { /* Error checking CRC8 for an AMR 7.4 frame */ return -1; } tch_amr_reassemble(tch_data, d, 148); len = 19; break; case 3: /* TCH/AFS6.7 */ osmo_conv_decode_ber(&gsm0503_tch_afs_6_7, cB + 8, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 134, 55); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 55, p); if (rv) { /* Error checking CRC8 for an AMR 6.7 frame */ return -1; } tch_amr_reassemble(tch_data, d, 134); len = 17; break; case 2: /* TCH/AFS5.9 */ osmo_conv_decode_ber(&gsm0503_tch_afs_5_9, cB + 8, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 118, 55); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 55, p); if (rv) { /* Error checking CRC8 for an AMR 5.9 frame */ return -1; } tch_amr_reassemble(tch_data, d, 118); len = 15; break; case 1: /* TCH/AFS5.15 */ osmo_conv_decode_ber(&gsm0503_tch_afs_5_15, cB + 8, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 103, 49); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 49, p); if (rv) { /* Error checking CRC8 for an AMR 5.15 frame */ return -1; } tch_amr_reassemble(tch_data, d, 103); len = 13; break; case 0: /* TCH/AFS4.75 */ osmo_conv_decode_ber(&gsm0503_tch_afs_4_75, cB + 8, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 95, 39); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 39, p); if (rv) { /* Error checking CRC8 for an AMR 4.75 frame */ return -1; } tch_amr_reassemble(tch_data, d, 95); len = 12; break; default: /* Unknown frame type */ *n_bits_total = 448; *n_errors = *n_bits_total; return -1; } out: /* Change codec request / indication, if frame is valid */ if (id != -1) { if (codec_mode_req) *cmr = id; else *ft = id; } return len; } /*! Perform channel encoding on a TCH/AFS channel according to TS 05.03 * \param[out] bursts caller-allocated output buffer for bursts bits * \param[in] tch_data Codec input data in RTP payload format * \param[in] len Length of \a tch_data in bytes or 0 to generate a bad frame * \param[in] codec_mode_req Use CMR (1) or FT (0) * \param[in] codec Array of codecs (active codec set) * \param[in] codecs Number of entries in \a codec * \param[in] ft Frame Type to be used for encoding (index to \a codec) * \param[in] cmr Codec Mode Request (used in codec_mode_req = 1 only) * \returns 0 in case of success; negative on error */ int gsm0503_tch_afs_encode(ubit_t *bursts, const uint8_t *tch_data, int len, int codec_mode_req, const uint8_t *codec, int codecs, uint8_t ft, uint8_t cmr) { ubit_t iB[912], cB[456], h; ubit_t d[244], p[6], conv[250]; int i; uint8_t id; if (len == GSM_MACBLOCK_LEN) { /* FACCH */ _xcch_encode_cB(cB, tch_data); h = 1; goto facch; } h = 0; id = codec_mode_req ? cmr : ft; if (OSMO_UNLIKELY(id >= ARRAY_SIZE(gsm0503_afs_ic_ubit))) return -1; if (OSMO_UNLIKELY(ft >= codecs)) return -1; switch (codec[ft]) { case 7: /* TCH/AFS12.2 */ if (!len) { /* No data, induce BFI in the receiver by inverted CRC bits. * The data bit are all 0, so the correct parity bits would be 111111. */ memset(d, 0, 244); memset(p, 0, 6); } else { if (len != 31) goto invalid_length; tch_amr_disassemble(d, tch_data, 244); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 81, p); } tch_amr_merge(conv, d, p, 244, 81); osmo_conv_encode(&gsm0503_tch_afs_12_2, conv, cB + 8); break; case 6: /* TCH/AFS10.2 */ if (!len) { /* See comment above. */ memset(d, 0, 204); memset(p, 0, 6); } else { if (len != 26) goto invalid_length; tch_amr_disassemble(d, tch_data, 204); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 65, p); } tch_amr_merge(conv, d, p, 204, 65); osmo_conv_encode(&gsm0503_tch_afs_10_2, conv, cB + 8); break; case 5: /* TCH/AFS7.95 */ if (!len) { /* See comment above. */ memset(d, 0, 159); memset(p, 0, 6); } else { if (len != 20) goto invalid_length; tch_amr_disassemble(d, tch_data, 159); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 75, p); } tch_amr_merge(conv, d, p, 159, 75); osmo_conv_encode(&gsm0503_tch_afs_7_95, conv, cB + 8); break; case 4: /* TCH/AFS7.4 */ if (!len) { /* See comment above. */ memset(d, 0, 148); memset(p, 0, 6); } else { if (len != 19) goto invalid_length; tch_amr_disassemble(d, tch_data, 148); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 61, p); } tch_amr_merge(conv, d, p, 148, 61); osmo_conv_encode(&gsm0503_tch_afs_7_4, conv, cB + 8); break; case 3: /* TCH/AFS6.7 */ if (!len) { /* See comment above. */ memset(d, 0, 134); memset(p, 0, 6); } else { if (len != 17) goto invalid_length; tch_amr_disassemble(d, tch_data, 134); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); } tch_amr_merge(conv, d, p, 134, 55); osmo_conv_encode(&gsm0503_tch_afs_6_7, conv, cB + 8); break; case 2: /* TCH/AFS5.9 */ if (!len) { /* See comment above. */ memset(d, 0, 118); memset(p, 0, 6); } else { if (len != 15) goto invalid_length; tch_amr_disassemble(d, tch_data, 118); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); } tch_amr_merge(conv, d, p, 118, 55); osmo_conv_encode(&gsm0503_tch_afs_5_9, conv, cB + 8); break; case 1: /* TCH/AFS5.15 */ if (!len) { /* See comment above. */ memset(d, 0, 103); memset(p, 0, 6); } else { if (len != 13) goto invalid_length; tch_amr_disassemble(d, tch_data, 103); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 49, p); } tch_amr_merge(conv, d, p, 103, 49); osmo_conv_encode(&gsm0503_tch_afs_5_15, conv, cB + 8); break; case 0: /* TCH/AFS4.75 */ if (!len) { /* See comment above. */ memset(d, 0, 95); memset(p, 0, 6); } else { if (len != 12) goto invalid_length; tch_amr_disassemble(d, tch_data, 95); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 39, p); } tch_amr_merge(conv, d, p, 95, 39); osmo_conv_encode(&gsm0503_tch_afs_4_75, conv, cB + 8); break; default: /* FIXME: FT %ft is not supported */ return -1; } memcpy(cB, gsm0503_afs_ic_ubit[id], 8); facch: gsm0503_tch_fr_interleave(cB, iB); for (i = 0; i < 8; i++) { gsm0503_tch_burst_map(&iB[i * 114], &bursts[i * 116], &h, i >> 2); } return 0; invalid_length: /* FIXME: payload length %len does not comply with codec type %ft */ return -1; } /* TCH/AHS: parse codec ID (CMI or CMC/CMR) from coded in-band data (16 bit) */ static uint8_t gsm0503_tch_ahs_decode_inband(const sbit_t *cB) { unsigned int id = 0, best = 0; unsigned int i, j, k; for (i = 0, k = 0; i < 4; i++) { /* FIXME: why not using remaining (16 - 4) soft-bits here? */ for (j = 0, k = 0; j < 4; j++) k += abs(((int)gsm0503_ahs_ic_sbit[i][j]) - ((int)cB[j])); if (i == 0 || k < best) { best = k; id = i; } } return id; } /*! Perform channel decoding of a TCH/AHS channel according TS 05.03 * \param[out] tch_data Codec frame in RTP payload format * \param[in] bursts buffer containing the symbols of 6 bursts * \param[in] odd Is this an odd (1) or even (0) frame number? * \param[in] codec_mode_req is this CMR (1) or CMC (0) * \param[in] codec array of active codecs (active codec set) * \param[in] codecs number of codecs in \a codec * \param ft Frame Type; Input if \a codec_mode_req = 1, Output * otherwise * \param[out] cmr Output in \a codec_mode_req = 1 * \param[out] n_errors Number of detected bit errors * \param[out] n_bits_total Total number of bits * \returns (>=4) length of bytes used in \a tch_data output buffer; ([0,3]) * codec out of range; negative on error */ int gsm0503_tch_ahs_decode(uint8_t *tch_data, const sbit_t *bursts, int odd, int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft, uint8_t *cmr, int *n_errors, int *n_bits_total) { return gsm0503_tch_ahs_decode_dtx(tch_data, bursts, odd, codec_mode_req, codec, codecs, ft, cmr, n_errors, n_bits_total, NULL); } /*! Perform channel decoding of a TCH/AHS channel according TS 05.03 * \param[out] tch_data Codec frame in RTP payload format * \param[in] bursts buffer containing the symbols of 6 bursts * \param[in] odd Is this an odd (1) or even (0) frame number? * \param[in] codec_mode_req is this CMR (1) or CMC (0) * \param[in] codec array of active codecs (active codec set) * \param[in] codecs number of codecs in \a codec * \param ft Frame Type; Input if \a codec_mode_req = 1, Output * otherwise * \param[out] cmr Output in \a codec_mode_req = 1 * \param[out] n_errors Number of detected bit errors * \param[out] n_bits_total Total number of bits * \param[inout] dtx DTX frame type output, previous DTX frame type input * \returns (>=4) length of bytes used in \a tch_data output buffer; ([0,3]) * codec out of range; negative on error */ int gsm0503_tch_ahs_decode_dtx(uint8_t *tch_data, const sbit_t *bursts, int odd, int codec_mode_req, uint8_t *codec, int codecs, uint8_t *ft, uint8_t *cmr, int *n_errors, int *n_bits_total, uint8_t *dtx) { sbit_t iB[912], cB[456], h; ubit_t d[244], p[6], conv[135]; int i, rv, len, steal = 0, id = -1; static ubit_t sid_first_dummy[64] = { 0 }; /* only unmap the stealing bits */ if (!odd) { for (i = 0; i < 4; i++) { gsm0503_tch_burst_unmap(NULL, &bursts[i * 116], &h, 0); steal -= h; } for (i = 2; i < 5; i++) { gsm0503_tch_burst_unmap(NULL, &bursts[i * 116], &h, 1); steal -= h; } } /* if we found a stole FACCH, but only at correct alignment */ if (steal > 0) { /* If not NULL, dtx indicates type of previously decoded TCH/AHS frame. * It's normally updated by gsm0503_detect_ahs_dtx_frame2(), which is not * reached in case of FACCH. Reset it here to avoid FACCH/H frames being * misinterpreted as AMR's special DTX frames. */ if (dtx != NULL) *dtx = AMR_OTHER; for (i = 0; i < 6; i++) { gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], NULL, i >> 2); } for (i = 2; i < 4; i++) { gsm0503_tch_burst_unmap(&iB[i * 114 + 456], &bursts[i * 116], NULL, 1); } gsm0503_tch_fr_deinterleave(cB, iB); rv = _xcch_decode_cB(tch_data, cB, n_errors, n_bits_total); if (rv) { /* Error decoding FACCH frame */ return -1; } return GSM_MACBLOCK_LEN; } for (i = 0; i < 4; i++) { gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], NULL, i >> 1); } gsm0503_tch_hr_deinterleave(cB, iB); /* Determine the DTX frame type (SID_UPDATE, ONSET etc...) */ if (dtx) { int n_bits_total_sid; int n_errors_sid; *dtx = gsm0503_detect_ahs_dtx_frame2(n_errors, n_bits_total, &id, cB); /* TODO: detect and handle AHS_SID_UPDATE + AHS_SID_UPDATE_INH */ switch (*dtx) { case AHS_SID_UPDATE: /* TODO: parse CMI _and_ CMC/CMR (16 + 16 bit) */ /* cB[] contains 16 bits of coded in-band data and 212 bits containing * the identification marker. We need to unmap/deinterleave 114 odd * bits from the last two blocks, 114 even bits from the first two * blocks and combine them together. */ gsm0503_tch_burst_unmap(&iB[0 * 114], &bursts[2 * 116], NULL, 0); gsm0503_tch_burst_unmap(&iB[1 * 114], &bursts[3 * 116], NULL, 0); gsm0503_tch_burst_unmap(&iB[2 * 114], &bursts[0 * 116], NULL, 1); gsm0503_tch_burst_unmap(&iB[3 * 114], &bursts[1 * 116], NULL, 1); gsm0503_tch_hr_deinterleave(cB, iB); /* cB[] is expected to contain 16 bits of coded in-band data and * 212 bits containing the coded data (53 bits coded at 1/4 rate). */ *dtx = AHS_SID_UPDATE_CN; osmo_conv_decode_ber(&gsm0503_tch_axs_sid_update, cB + 16, conv, &n_errors_sid, &n_bits_total_sid); /* gsm0503_detect_ahs_dtx_frame2() calculates BER for the marker, * osmo_conv_decode_ber() calculates BER for the coded data. */ if (n_errors != NULL) *n_errors += n_errors_sid; if (n_bits_total != NULL) *n_bits_total += n_bits_total_sid; rv = osmo_crc16gen_check_bits(&gsm0503_amr_crc14, conv, 35, conv + 35); if (rv != 0) { /* Error checking CRC14 for an AMR SID_UPDATE frame */ return -1; } tch_amr_sid_update_append(conv, 1, (codec_mode_req) ? codec[*ft] : codec[id > 0 ? id : 0]); tch_amr_reassemble(tch_data, conv, 39); len = 5; goto out; case AHS_SID_FIRST_P2: tch_amr_sid_update_append(sid_first_dummy, 0, (codec_mode_req) ? codec[*ft] : codec[id > 0 ? id : 0]); tch_amr_reassemble(tch_data, sid_first_dummy, 39); len = 5; goto out; case AHS_ONSET: case AHS_SID_FIRST_INH: /* TODO: parse CMI or CMC/CMR (16 bit) */ case AHS_SID_UPDATE_INH: /* TODO: parse CMI or CMC/CMR (16 bit) */ case AHS_SID_FIRST_P1: /* TODO: parse CMI or CMC/CMR (16 bit) */ len = 0; goto out; default: break; } } /* Parse codec ID (CMI or CMC/CMR) and check if it fits into range of codecs */ if ((id = gsm0503_tch_ahs_decode_inband(&cB[0])) >= codecs) { /* Codec mode out of range, return id */ return id; } switch ((codec_mode_req) ? codec[*ft] : codec[id]) { case 5: /* TCH/AHS7.95 */ osmo_conv_decode_ber(&gsm0503_tch_ahs_7_95, cB + 4, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 123, 67); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 67, p); if (rv) { /* Error checking CRC8 for an AMR 7.95 frame */ return -1; } for (i = 0; i < 36; i++) d[i + 123] = (cB[i + 192] < 0) ? 1 : 0; tch_amr_reassemble(tch_data, d, 159); len = 20; break; case 4: /* TCH/AHS7.4 */ osmo_conv_decode_ber(&gsm0503_tch_ahs_7_4, cB + 4, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 120, 61); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 61, p); if (rv) { /* Error checking CRC8 for an AMR 7.4 frame */ return -1; } for (i = 0; i < 28; i++) d[i + 120] = (cB[i + 200] < 0) ? 1 : 0; tch_amr_reassemble(tch_data, d, 148); len = 19; break; case 3: /* TCH/AHS6.7 */ osmo_conv_decode_ber(&gsm0503_tch_ahs_6_7, cB + 4, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 110, 55); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 55, p); if (rv) { /* Error checking CRC8 for an AMR 6.7 frame */ return -1; } for (i = 0; i < 24; i++) d[i + 110] = (cB[i + 204] < 0) ? 1 : 0; tch_amr_reassemble(tch_data, d, 134); len = 17; break; case 2: /* TCH/AHS5.9 */ osmo_conv_decode_ber(&gsm0503_tch_ahs_5_9, cB + 4, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 102, 55); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 55, p); if (rv) { /* Error checking CRC8 for an AMR 5.9 frame */ return -1; } for (i = 0; i < 16; i++) d[i + 102] = (cB[i + 212] < 0) ? 1 : 0; tch_amr_reassemble(tch_data, d, 118); len = 15; break; case 1: /* TCH/AHS5.15 */ osmo_conv_decode_ber(&gsm0503_tch_ahs_5_15, cB + 4, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 91, 49); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 49, p); if (rv) { /* Error checking CRC8 for an AMR 5.15 frame */ return -1; } for (i = 0; i < 12; i++) d[i + 91] = (cB[i + 216] < 0) ? 1 : 0; tch_amr_reassemble(tch_data, d, 103); len = 13; break; case 0: /* TCH/AHS4.75 */ osmo_conv_decode_ber(&gsm0503_tch_ahs_4_75, cB + 4, conv, n_errors, n_bits_total); tch_amr_unmerge(d, p, conv, 83, 39); rv = osmo_crc8gen_check_bits(&gsm0503_amr_crc6, d, 39, p); if (rv) { /* Error checking CRC8 for an AMR 4.75 frame */ return -1; } for (i = 0; i < 12; i++) d[i + 83] = (cB[i + 216] < 0) ? 1 : 0; tch_amr_reassemble(tch_data, d, 95); len = 12; break; default: /* Unknown frame type */ *n_bits_total = 159; *n_errors = *n_bits_total; return -1; } out: /* Change codec request / indication, if frame is valid */ if (id != -1) { if (codec_mode_req) *cmr = id; else *ft = id; } return len; } /*! Perform channel encoding on a TCH/AHS channel according to TS 05.03 * \param[out] bursts caller-allocated output buffer for bursts bits * \param[in] tch_data Codec input data in RTP payload format * \param[in] len Length of \a tch_data in bytes or 0 to generate a bad frame * \param[in] codec_mode_req Use CMR (1) or FT (0) * \param[in] codec Array of codecs (active codec set) * \param[in] codecs Number of entries in \a codec * \param[in] ft Frame Type to be used for encoding (index to \a codec) * \param[in] cmr Codec Mode Request (used in codec_mode_req = 1 only) * \returns 0 in case of success; negative on error */ int gsm0503_tch_ahs_encode(ubit_t *bursts, const uint8_t *tch_data, int len, int codec_mode_req, const uint8_t *codec, int codecs, uint8_t ft, uint8_t cmr) { ubit_t iB[912], cB[456], h; ubit_t d[244], p[6], conv[135]; int i; uint8_t id; if (len == GSM_MACBLOCK_LEN) { /* FACCH */ _xcch_encode_cB(cB, tch_data); h = 1; gsm0503_tch_fr_interleave(cB, iB); for (i = 0; i < 6; i++) gsm0503_tch_burst_map(&iB[i * 114], &bursts[i * 116], &h, i >> 2); for (i = 2; i < 4; i++) gsm0503_tch_burst_map(&iB[i * 114 + 456], &bursts[i * 116], &h, 1); return 0; } h = 0; id = codec_mode_req ? cmr : ft; if (OSMO_UNLIKELY(id >= ARRAY_SIZE(gsm0503_ahs_ic_ubit))) return -1; if (OSMO_UNLIKELY(ft >= codecs)) return -1; switch (codec[ft]) { case 5: /* TCH/AHS7.95 */ if (!len) { /* No data, induce BFI in the receiver by inverted CRC bits. * The data bit are all 0, so the correct parity bits would be 111111. */ memset(d, 0, 159); memset(p, 0, 6); } else { if (len != 20) goto invalid_length; tch_amr_disassemble(d, tch_data, 159); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 67, p); } tch_amr_merge(conv, d, p, 123, 67); osmo_conv_encode(&gsm0503_tch_ahs_7_95, conv, cB + 4); memcpy(cB + 192, d + 123, 36); break; case 4: /* TCH/AHS7.4 */ if (!len) { /* See comment above. */ memset(d, 0, 148); memset(p, 0, 6); } else { if (len != 19) goto invalid_length; tch_amr_disassemble(d, tch_data, 148); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 61, p); } tch_amr_merge(conv, d, p, 120, 61); osmo_conv_encode(&gsm0503_tch_ahs_7_4, conv, cB + 4); memcpy(cB + 200, d + 120, 28); break; case 3: /* TCH/AHS6.7 */ if (!len) { /* See comment above. */ memset(d, 0, 134); memset(p, 0, 6); } else { if (len != 17) goto invalid_length; tch_amr_disassemble(d, tch_data, 134); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); } tch_amr_merge(conv, d, p, 110, 55); osmo_conv_encode(&gsm0503_tch_ahs_6_7, conv, cB + 4); memcpy(cB + 204, d + 110, 24); break; case 2: /* TCH/AHS5.9 */ if (!len) { /* See comment above. */ memset(d, 0, 118); memset(p, 0, 6); } else { if (len != 15) goto invalid_length; tch_amr_disassemble(d, tch_data, 118); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 55, p); } tch_amr_merge(conv, d, p, 102, 55); osmo_conv_encode(&gsm0503_tch_ahs_5_9, conv, cB + 4); memcpy(cB + 212, d + 102, 16); break; case 1: /* TCH/AHS5.15 */ if (!len) { /* See comment above. */ memset(d, 0, 103); memset(p, 0, 6); } else { if (len != 13) goto invalid_length; tch_amr_disassemble(d, tch_data, 103); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 49, p); } tch_amr_merge(conv, d, p, 91, 49); osmo_conv_encode(&gsm0503_tch_ahs_5_15, conv, cB + 4); memcpy(cB + 216, d + 91, 12); break; case 0: /* TCH/AHS4.75 */ if (!len) { /* See comment above. */ memset(d, 0, 95); memset(p, 0, 6); } else { if (len != 12) goto invalid_length; tch_amr_disassemble(d, tch_data, 95); osmo_crc8gen_set_bits(&gsm0503_amr_crc6, d, 39, p); } tch_amr_merge(conv, d, p, 83, 39); osmo_conv_encode(&gsm0503_tch_ahs_4_75, conv, cB + 4); memcpy(cB + 216, d + 83, 12); break; default: /* FIXME: FT %ft is not supported */ return -1; } memcpy(cB, gsm0503_ahs_ic_ubit[id], 4); gsm0503_tch_hr_interleave(cB, iB); for (i = 0; i < 4; i++) gsm0503_tch_burst_map(&iB[i * 114], &bursts[i * 116], &h, i >> 1); return 0; invalid_length: /* FIXME: payload length %len does not comply with codec type %ft */ return -1; } /* * GSM RACH transcoding */ /* * GSM RACH apply BSIC to parity * * p(j) = p(j) xor b(j) j = 0, ..., 5 * b(0) = MSB of PLMN colour code * b(5) = LSB of BS colour code */ static inline void rach_apply_bsic(ubit_t *d, uint8_t bsic, uint8_t start) { int i; /* Apply it */ for (i = 0; i < 6; i++) d[start + i] ^= ((bsic >> (5 - i)) & 1); } static inline int16_t rach_decode_ber(const sbit_t *burst, uint8_t bsic, bool is_11bit, int *n_errors, int *n_bits_total) { ubit_t conv[17]; uint8_t ra[2] = { 0 }, nbits = is_11bit ? 11 : 8; int rv; osmo_conv_decode_ber(is_11bit ? &gsm0503_rach_ext : &gsm0503_rach, burst, conv, n_errors, n_bits_total); rach_apply_bsic(conv, bsic, nbits); rv = osmo_crc8gen_check_bits(&gsm0503_rach_crc6, conv, nbits, conv + nbits); if (rv) return -1; osmo_ubit2pbit_ext(ra, 0, conv, 0, nbits, 1); return is_11bit ? ((ra[0] << 3) | (ra[1] & 0x07)) : ra[0]; } /*! Decode the Extended (11-bit) RACH according to 3GPP TS 45.003 * \param[out] ra output buffer for RACH data * \param[in] burst Input burst data * \param[in] bsic BSIC used in this cell * \returns 0 on success; negative on error (e.g. CRC error) */ int gsm0503_rach_ext_decode(uint16_t *ra, const sbit_t *burst, uint8_t bsic) { int16_t r = rach_decode_ber(burst, bsic, true, NULL, NULL); if (r < 0) return r; *ra = r; return 0; } /*! Decode the (8-bit) RACH according to TS 05.03 * \param[out] ra output buffer for RACH data * \param[in] burst Input burst data * \param[in] bsic BSIC used in this cell * \returns 0 on success; negative on error (e.g. CRC error) */ int gsm0503_rach_decode(uint8_t *ra, const sbit_t *burst, uint8_t bsic) { int16_t r = rach_decode_ber(burst, bsic, false, NULL, NULL); if (r < 0) return r; *ra = r; return 0; } /*! Decode the Extended (11-bit) RACH according to 3GPP TS 45.003 * \param[out] ra output buffer for RACH data * \param[in] burst Input burst data * \param[in] bsic BSIC used in this cell * \param[out] n_errors Number of detected bit errors * \param[out] n_bits_total Total number of bits * \returns 0 on success; negative on error (e.g. CRC error) */ int gsm0503_rach_ext_decode_ber(uint16_t *ra, const sbit_t *burst, uint8_t bsic, int *n_errors, int *n_bits_total) { int16_t r = rach_decode_ber(burst, bsic, true, n_errors, n_bits_total); if (r < 0) return r; *ra = r; return 0; } /*! Decode the (8-bit) RACH according to TS 05.03 * \param[out] ra output buffer for RACH data * \param[in] burst Input burst data * \param[in] bsic BSIC used in this cell * \param[out] n_errors Number of detected bit errors * \param[out] n_bits_total Total number of bits * \returns 0 on success; negative on error (e.g. CRC error) */ int gsm0503_rach_decode_ber(uint8_t *ra, const sbit_t *burst, uint8_t bsic, int *n_errors, int *n_bits_total) { int16_t r = rach_decode_ber(burst, bsic, false, n_errors, n_bits_total); if (r < 0) return r; *ra = r; return 0; } /*! Encode the (8-bit) RACH according to TS 05.03 * \param[out] burst Caller-allocated output burst buffer * \param[in] ra Input RACH data * \param[in] bsic BSIC used in this cell * \returns 0 on success; negative on error */ int gsm0503_rach_encode(ubit_t *burst, const uint8_t *ra, uint8_t bsic) { return gsm0503_rach_ext_encode(burst, *ra, bsic, false); } /*! Encode the Extended (11-bit) or regular (8-bit) RACH according to 3GPP TS 45.003 * \param[out] burst Caller-allocated output burst buffer * \param[in] ra11 Input RACH data * \param[in] bsic BSIC used in this cell * \param[in] is_11bit whether given RA is 11 bit or not * \returns 0 on success; negative on error */ int gsm0503_rach_ext_encode(ubit_t *burst, uint16_t ra11, uint8_t bsic, bool is_11bit) { ubit_t conv[17]; uint8_t ra[2] = { 0 }, nbits = 8; if (is_11bit) { ra[0] = (uint8_t) (ra11 >> 3); ra[1] = (uint8_t) (ra11 & 0x07); nbits = 11; } else ra[0] = (uint8_t)ra11; osmo_pbit2ubit_ext(conv, 0, ra, 0, nbits, 1); osmo_crc8gen_set_bits(&gsm0503_rach_crc6, conv, nbits, conv + nbits); rach_apply_bsic(conv, bsic, nbits); osmo_conv_encode(is_11bit ? &gsm0503_rach_ext : &gsm0503_rach, conv, burst); return 0; } /* * GSM SCH transcoding */ /*! Decode the SCH according to TS 05.03 * \param[out] sb_info output buffer for SCH data * \param[in] burst Input burst data * \returns 0 on success; negative on error (e.g. CRC error) */ int gsm0503_sch_decode(uint8_t *sb_info, const sbit_t *burst) { ubit_t conv[35]; int rv; osmo_conv_decode(&gsm0503_sch, burst, conv); rv = osmo_crc16gen_check_bits(&gsm0503_sch_crc10, conv, 25, conv + 25); if (rv) return -1; osmo_ubit2pbit_ext(sb_info, 0, conv, 0, 25, 1); return 0; } /*! Encode the SCH according to TS 05.03 * \param[out] burst Caller-allocated output burst buffer * \param[in] sb_info Input SCH data * \returns 0 on success; negative on error */ int gsm0503_sch_encode(ubit_t *burst, const uint8_t *sb_info) { ubit_t conv[35]; osmo_pbit2ubit_ext(conv, 0, sb_info, 0, 25, 1); osmo_crc16gen_set_bits(&gsm0503_sch_crc10, conv, 25, conv + 25); osmo_conv_encode(&gsm0503_sch, conv, burst); return 0; } /* * GSM CSD transcoding */ static inline void _tch_csd_burst_map(ubit_t *burst, const ubit_t *iB) { unsigned int i; /* hu(B): copy *even* numbered bits if not stolen by FACCH */ if (burst[58] == 0) { for (i = 0; i < 57; i += 2) burst[i] |= iB[i]; for (i = 58; i < 114; i += 2) burst[i + 2] |= iB[i]; } /* hl(B): copy *odd* numbered bits if not stolen by FACCH */ if (burst[57] == 0) { for (i = 1; i < 57; i += 2) burst[i] |= iB[i]; for (i = 57; i < 114; i += 2) burst[i + 2] |= iB[i]; } } /*! Perform channel encoding of a TCH/F9.6 channel as per section 3.3. * \param[out] bursts Caller-allocated buffer for symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[in] data Data to be encoded (240 unpacked bits). * \returns 0 in case of success; negative on error. */ int gsm0503_tch_fr96_encode(ubit_t *bursts, const ubit_t *data) { ubit_t iB[22 * 114], cB[4 * 114]; ubit_t conv[4 * 60 + 4]; /* 3.3.2 Block code: b1(60) + b2(60) + b3(60) + b4(60) + pad(4) */ memcpy(&conv[0], &data[0], 4 * 60); /* pad(4) is set to 0 by osmo_conv_encode() below */ /* 3.3.3 Convolutional encoder */ osmo_conv_encode(&gsm0503_tch_f96, &conv[0], &cB[0]); /* 3.3.4 Interleaving */ memset(&iB[0], 0, sizeof(iB)); gsm0503_tch_f96_interleave(&cB[0], &iB[0]); /* 3.3.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 22; i++) _tch_csd_burst_map(&bursts[i * 116], &iB[i * 114]); return 0; } /*! Perform channel decoding of a TCH/F9.6 channel as per section 3.3. * \param[out] data Caller-allocated buffer for decoded data (240 unpacked bits). * \param[in] bursts Buffer containing the symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[out] n_errors Number of detected bit errors. * \param[out] n_bits_total Total number of bits. * \returns Number of unpacked bits used in the output buffer; negative on error. */ int gsm0503_tch_fr96_decode(ubit_t *data, const sbit_t *bursts, int *n_errors, int *n_bits_total) { sbit_t iB[22 * 114], cB[4 * 114]; ubit_t conv[4 * 60 + 4]; /* 3.3.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 22; i++) { memcpy(&iB[i * 114], &bursts[i * 116], 57); memcpy(&iB[i * 114 + 57], &bursts[i * 116 + 59], 57); } /* 3.3.4 Interleaving */ gsm0503_tch_f96_deinterleave(&cB[0], &iB[0]); /* 3.3.3 Convolutional encoder */ osmo_conv_decode_ber(&gsm0503_tch_f96, &cB[0], &conv[0], n_errors, n_bits_total); /* 3.3.2 Block code: b1(60) + b2(60) + b3(60) + b4(60) + pad(4) */ memcpy(&data[0], &conv[0], 4 * 60); return 4 * 60; } /*! Perform channel encoding of a TCH/F4.8 channel as per section 3.4. * \param[out] bursts Caller-allocated buffer for symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[in] data Data to be encoded (120 unpacked bits). * \returns 0 in case of success; negative on error */ int gsm0503_tch_fr48_encode(ubit_t *bursts, const ubit_t *data) { ubit_t iB[22 * 114], cB[4 * 114]; ubit_t conv[2 * 60 + 32]; /* 3.4.2 Block code: * * Sixteen bits equal to 0 are added to the 60 information bits, the result * being a block of 76 bits, {u(0),u(1),...,u(75)}, with: * * u(19k+p) = d(15k+p) for k = 0,1,2,3 and p = 0,1,...,14; * u(19k+p) = 0 for k = 0,1,2,3 and p = 15,16,17,18. * * Two such blocks forming a block of 152 bits: u1 + u2. */ for (unsigned int k = 0; k < 2 * 4; k++) { memcpy(&conv[19 * k], &data[15 * k], 15); memset(&conv[19 * k + 15], 0, 4); } /* 3.4.3 Convolutional encoder */ osmo_conv_encode(&gsm0503_tch_f48, &conv[0], &cB[0]); /* 3.4.4 Interleaving: as specified for the TCH/F9.6 in subclause 3.3.4 */ memset(&iB[0], 0, sizeof(iB)); gsm0503_tch_f96_interleave(&cB[0], &iB[0]); /* 3.4.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 22; i++) _tch_csd_burst_map(&bursts[i * 116], &iB[i * 114]); return 0; } /*! Perform channel decoding of a TCH/F4.8 channel as per section 3.4. * \param[out] data Caller-allocated buffer for decoded data (120 unpacked bits). * \param[in] bursts Buffer containing the symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[out] n_errors Number of detected bit errors. * \param[out] n_bits_total Total number of bits. * \returns Number of unpacked bits used in the output buffer; negative on error. */ int gsm0503_tch_fr48_decode(ubit_t *data, const sbit_t *bursts, int *n_errors, int *n_bits_total) { sbit_t iB[22 * 114], cB[4 * 114]; ubit_t conv[2 * 60 + 32]; /* 3.4.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 22; i++) { memcpy(&iB[i * 114], &bursts[i * 116], 57); memcpy(&iB[i * 114 + 57], &bursts[i * 116 + 59], 57); } /* 3.4.4 Interleaving: as specified for the TCH/F9.6 in subclause 3.3.4 */ gsm0503_tch_f96_deinterleave(&cB[0], &iB[0]); /* 3.4.3 Convolutional encoder */ osmo_conv_decode_ber(&gsm0503_tch_f48, &cB[0], &conv[0], n_errors, n_bits_total); /* 3.4.2 Block code: * * Sixteen bits equal to 0 are added to the 60 information bits, the result * being a block of 76 bits, {u(0),u(1),...,u(75)}, with: * * u(19k+p) = d(15k+p) for k = 0,1,2,3 and p = 0,1,...,14; * u(19k+p) = 0 for k = 0,1,2,3 and p = 15,16,17,18. * * Two such blocks forming a block of 152 bits: u1 + u2. */ for (unsigned int k = 0; k < 2 * 4; k++) memcpy(&data[15 * k], &conv[19 * k], 15); return 2 * 60; } /*! Perform channel encoding of a TCH/H4.8 channel as per section 3.5. * The algorithm is identical to TCH/F9.6, so it's just a wrapper. * \param[out] bursts Caller-allocated buffer for symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[in] data Data to be encoded (240 unpacked bits). * \returns 0 in case of success; negative on error */ int gsm0503_tch_hr48_encode(ubit_t *bursts, const ubit_t *data) { return gsm0503_tch_fr96_encode(bursts, data); } /*! Perform channel decoding of a TCH/H4.8 channel as per section 3.5. * The algorithm is identical to TCH/F9.6, so it's just a wrapper. * \param[out] data Caller-allocated buffer for decoded data (240 unpacked bits). * \param[in] bursts Buffer containing the symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[out] n_errors Number of detected bit errors. * \param[out] n_bits_total Total number of bits. * \returns Number of unpacked bits used in the output buffer; negative on error. */ int gsm0503_tch_hr48_decode(ubit_t *data, const sbit_t *bursts, int *n_errors, int *n_bits_total) { return gsm0503_tch_fr96_decode(data, bursts, n_errors, n_bits_total); } /*! Perform channel encoding of a TCH/F2.4 channel as per section 3.6. * \param[out] bursts Caller-allocated buffer for symbols of 8 bursts, * 8 * 2 * 58 == 928 bits total. * \param[in] data Data to be encoded (72 unpacked bits). * \returns 0 in case of success; negative on error */ int gsm0503_tch_fr24_encode(ubit_t *bursts, const ubit_t *data) { ubit_t iB[8 * 114], cB[4 * 114]; const ubit_t h = 0; /* 3.6.{1-3} Block code and Convolutional encoder */ osmo_conv_encode(&gsm0503_tch_f24, &data[0], &cB[0]); /* 3.6.4 Interleaving: as specified for the TCH/FS in subclause 3.1.3 */ gsm0503_tch_fr_interleave(&cB[0], &iB[0]); /* 3.6.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 8; i++) gsm0503_tch_burst_map(&iB[i * 114], &bursts[i * 116], &h, i >> 2); return 0; } /*! Perform channel decoding of a TCH/F2.4 channel as per section 3.6. * \param[out] data Caller-allocated buffer for decoded data (72 unpacked bits). * \param[in] bursts Buffer containing the symbols of 8 bursts, * 8 * 2 * 58 == 928 bits total. * \param[out] n_errors Number of detected bit errors. * \param[out] n_bits_total Total number of bits. * \returns Number of unpacked bits used in the output buffer; negative on error. */ int gsm0503_tch_fr24_decode(ubit_t *data, const sbit_t *bursts, int *n_errors, int *n_bits_total) { sbit_t iB[8 * 114], cB[4 * 114]; /* 3.6.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 8; i++) gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], NULL, i >> 2); /* 3.6.4 Interleaving: as specified for the TCH/FS in subclause 3.1.3 */ gsm0503_tch_fr_deinterleave(&cB[0], &iB[0]); /* 3.6.{1-3} Block code and Convolutional encoder */ osmo_conv_decode_ber(&gsm0503_tch_f24, &cB[0], &data[0], n_errors, n_bits_total); return 72; } /*! Perform channel encoding of a TCH/H2.4 channel as per section 3.7. * \param[out] bursts Caller-allocated buffer for symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[in] data Data to be encoded (144 unpacked bits). * \returns 0 in case of success; negative on error */ int gsm0503_tch_hr24_encode(ubit_t *bursts, const ubit_t *data) { ubit_t iB[22 * 114], cB[4 * 114]; /* 3.7.{1-3} Block code and Convolutional encoder */ osmo_conv_encode(&gsm0503_tch_h24, &data[ 0], &cB[ 0]); osmo_conv_encode(&gsm0503_tch_h24, &data[72], &cB[228]); /* 3.7.4 Interleaving: as specified for the TCH/F9.6 in subclause 3.3.4 */ memset(&iB[0], 0, sizeof(iB)); gsm0503_tch_f96_interleave(&cB[0], &iB[0]); /* 3.7.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 22; i++) _tch_csd_burst_map(&bursts[i * 116], &iB[i * 114]); return 0; } /*! Perform channel decoding of a TCH/H2.4 channel as per section 3.7. * \param[out] data Caller-allocated buffer for decoded data (144 unpacked bits). * \param[in] bursts Buffer containing the symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[out] n_errors Number of detected bit errors. * \param[out] n_bits_total Total number of bits. * \returns Number of unpacked bits used in the output buffer; negative on error. */ int gsm0503_tch_hr24_decode(ubit_t *data, const sbit_t *bursts, int *n_errors, int *n_bits_total) { int n_errors_l[2], n_bits_total_l[2]; sbit_t iB[22 * 114], cB[4 * 114]; /* 3.7.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 22; i++) { memcpy(&iB[i * 114], &bursts[i * 116], 57); memcpy(&iB[i * 114 + 57], &bursts[i * 116 + 59], 57); } /* 3.7.4 Interleaving: as specified for the TCH/F9.6 in subclause 3.3.4 */ gsm0503_tch_f96_deinterleave(&cB[0], &iB[0]); /* 3.7.{1-3} Block code and Convolutional encoder */ osmo_conv_decode_ber(&gsm0503_tch_h24, &cB[ 0], &data[ 0], &n_errors_l[0], &n_bits_total_l[0]); osmo_conv_decode_ber(&gsm0503_tch_h24, &cB[228], &data[72], &n_errors_l[1], &n_bits_total_l[1]); if (n_errors) *n_errors = n_errors_l[0] + n_errors_l[1]; if (n_bits_total) *n_bits_total = n_bits_total_l[0] + n_bits_total_l[1]; return 2 * 72; } /*! Perform channel encoding of a TCH/F14.4 channel as per section 3.8. * \param[out] bursts Caller-allocated buffer for symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[in] data Data to be encoded (290 unpacked bits). * \returns 0 in case of success; negative on error */ int gsm0503_tch_fr144_encode(ubit_t *bursts, const ubit_t *data) { ubit_t iB[22 * 114], cB[4 * 114]; ubit_t conv[290 + 4]; /* 3.8.2 Block code: b(290) + pad(4) */ memcpy(&conv[0], &data[0], 290); /* pad(4) is set to 0 by osmo_conv_encode() below */ /* 3.8.3 Convolutional encoder */ osmo_conv_encode(&gsm0503_tch_f144, &conv[0], &cB[0]); /* 3.8.4 Interleaving */ memset(&iB[0], 0, sizeof(iB)); gsm0503_tch_f96_interleave(&cB[0], &iB[0]); /* 3.8.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 22; i++) _tch_csd_burst_map(&bursts[i * 116], &iB[i * 114]); return 0; } /*! Perform channel decoding of a TCH/14.4 channel as per section 3.8. * \param[out] data Caller-allocated buffer for decoded data (290 unpacked bits). * \param[in] bursts Buffer containing the symbols of 22 bursts, * 22 * 2 * 58 == 2552 bits total. * \param[out] n_errors Number of detected bit errors. * \param[out] n_bits_total Total number of bits. * \returns Number of unpacked bits used in the output buffer; negative on error. */ int gsm0503_tch_fr144_decode(ubit_t *data, const sbit_t *bursts, int *n_errors, int *n_bits_total) { sbit_t iB[22 * 114], cB[4 * 114]; ubit_t conv[294]; /* 3.8.5 Mapping on a burst: as specified for TCH/FS in subclause 3.1.4 */ for (unsigned int i = 0; i < 22; i++) { memcpy(&iB[i * 114], &bursts[i * 116], 57); memcpy(&iB[i * 114 + 57], &bursts[i * 116 + 59], 57); } /* 3.8.4 Interleaving: as specified for the TCH/F9.6 in subclause 3.3.4 */ gsm0503_tch_f96_deinterleave(&cB[0], &iB[0]); /* 3.8.3 Convolutional encoder */ osmo_conv_decode_ber(&gsm0503_tch_f144, &cB[0], &conv[0], n_errors, n_bits_total); /* 3.8.2 Block code: b(290) + pad(4) */ memcpy(&data[0], &conv[0], 290); return 290; } /* * FACCH/[FH] transcoding */ /*! Perform channel encoding of a FACCH/F data as per section 4.2. * \param[out] bursts Caller-allocated buffer for symbols of 8 bursts, * 8 * 2 * 58 == 928 bits total. * \param[in] data FACCH MAC block to be encoded (GSM_MACBLOCK_LEN). * \returns 0 in case of success; negative on error */ int gsm0503_tch_fr_facch_encode(ubit_t *bursts, const uint8_t *data) { ubit_t iB[8 * 114], cB[4 * 114]; const ubit_t h = 1; /* 4.2.1-3 as specified for the SACCH in 4.1.1-3 */ _xcch_encode_cB(&cB[0], &data[0]); /* 4.2.4 Interleaving: as specified for the TCH/FS in subclause 3.1.3 */ gsm0503_tch_fr_interleave(&cB[0], &iB[0]); /* 4.2.5 Mapping on a Burst: * - hu(B)=1 the even numbered bits in the first 4 bursts and * - hl(B)=1 the odd numbered bits of the last 4 bursts are stolen. */ for (unsigned int i = 0; i < 8; i++) gsm0503_tch_burst_map(&iB[i * 114], &bursts[i * 116], &h, i >> 2); return 0; } /*! Perform channel decoding of a FACCH/F data as per section 4.2. * \param[out] data Caller-allocated buffer for decoded FACCH (GSM_MACBLOCK_LEN). * \param[in] bursts Buffer containing the symbols of 8 bursts, * 8 * 2 * 58 == 928 bits total. * \param[out] n_errors Number of detected bit errors. * \param[out] n_bits_total Total number of bits. * \returns Number of bytes used in the output buffer; negative on error. */ int gsm0503_tch_fr_facch_decode(uint8_t *data, const sbit_t *bursts, int *n_errors, int *n_bits_total) { sbit_t iB[8 * 114], cB[4 * 114]; int steal = 0; /* FACCH decision: sum of 4 first hu(B) and 4 last hl(B) soft-bits */ for (unsigned int i = 0; i < 4; i++) steal -= bursts[i * 116 + 58]; /* hu(B) */ for (unsigned int i = 4; i < 8; i++) steal -= bursts[i * 116 + 57]; /* hl(B) */ if (steal <= 0) return -1; /* 4.2.5 Mapping on a Burst: * - hu(B)=1 the even numbered bits in the first 4 bursts and * - hl(B)=1 the odd numbered bits of the last 4 bursts are stolen. */ for (unsigned int i = 0; i < 8; i++) gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], NULL, i >> 2); /* 4.2.4 Interleaving: as specified for the TCH/FS in subclause 3.1.3 */ gsm0503_tch_fr_deinterleave(&cB[0], &iB[0]); /* 4.2.1-3 as specified for the SACCH in 4.1.1-3 */ if (_xcch_decode_cB(&data[0], &cB[0], n_errors, n_bits_total) != 0) return -1; return GSM_MACBLOCK_LEN; } /*! Perform channel encoding of a FACCH/H data as per section 4.3. * \param[out] bursts Caller-allocated buffer for symbols of 6 bursts, * 6 * 2 * 58 == 696 bits total. * \param[in] data FACCH MAC block to be encoded (GSM_MACBLOCK_LEN). * \returns 0 in case of success; negative on error */ int gsm0503_tch_hr_facch_encode(ubit_t *bursts, const uint8_t *data) { ubit_t iB[8 * 114], cB[4 * 114]; const ubit_t h = 1; /* 4.3.1-3 as specified for the SACCH in 4.1.1-3 */ _xcch_encode_cB(&cB[0], &data[0]); /* 4.3.4 Interleaving */ gsm0503_tch_fr_interleave(&cB[0], &iB[0]); /* 4.3.5 Mapping on a Burst: * - hu(B)=1 the even numbered bits of the first 2 bursts, * - hu(B)=1 & hl(B)=1 all bits of the middle 2 bursts and * - hl(B)=1 the odd numbered bits of the last 2 bursts are stolen. */ for (unsigned int i = 0; i < 6; i++) gsm0503_tch_burst_map(&iB[i * 114], &bursts[i * 116], &h, i >> 2); for (unsigned int i = 2; i < 4; i++) gsm0503_tch_burst_map(&iB[i * 114 + 456], &bursts[i * 116], &h, 1); return 0; } /*! Perform channel decoding of a FACCH/H data as per section 4.3. * \param[out] data Caller-allocated buffer for decoded FACCH (GSM_MACBLOCK_LEN). * \param[in] bursts Buffer containing the symbols of 6 bursts, * 6 * 2 * 58 == 696 bits total. * \param[out] n_errors Number of detected bit errors. * \param[out] n_bits_total Total number of bits. * \returns Number of bytes used in the output buffer; negative on error. */ int gsm0503_tch_hr_facch_decode(uint8_t *data, const sbit_t *bursts, int *n_errors, int *n_bits_total) { sbit_t iB[8 * 114], cB[4 * 114]; int steal = 0; /* FACCH decision: sum of 4 first hu(B) and 4 last hl(B) soft-bits */ for (unsigned int i = 0; i < 4; i++) steal -= bursts[i * 116 + 58]; /* hu(B) */ for (unsigned int i = 2; i < 6; i++) steal -= bursts[i * 116 + 57]; /* hl(B) */ if (steal <= 0) return -1; /* 4.3.5 Mapping on a Burst: * - hu(B)=1 the even numbered bits of the first 2 bursts, * - hu(B)=1 & hl(B)=1 all bits of the middle 2 bursts and * - hl(B)=1 the odd numbered bits of the last 2 bursts are stolen. */ for (unsigned int i = 0; i < 6; i++) gsm0503_tch_burst_unmap(&iB[i * 114], &bursts[i * 116], NULL, i >> 2); for (unsigned int i = 2; i < 4; i++) gsm0503_tch_burst_unmap(&iB[i * 114 + 456], &bursts[i * 116], NULL, 1); /* 4.3.4 Interleaving */ gsm0503_tch_fr_deinterleave(&cB[0], &iB[0]); /* 4.3.1-3 as specified for the SACCH in 4.1.1-3 */ if (_xcch_decode_cB(&data[0], &cB[0], n_errors, n_bits_total) != 0) return -1; return GSM_MACBLOCK_LEN; } /*! @} */