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srsLTE/lib/src/phy/phch/npbch.c

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/**
* Copyright 2013-2022 Software Radio Systems Limited
*
* This file is part of srsRAN.
*
* srsRAN is free software: you can redistribute it and/or modify
* it under the terms of the GNU Affero General Public License as
* published by the Free Software Foundation, either version 3 of
* the License, or (at your option) any later version.
*
* srsRAN 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 Affero General Public License for more details.
*
* A copy of the GNU Affero General Public License can be found in
* the LICENSE file in the top-level directory of this distribution
* and at http://www.gnu.org/licenses/.
*
*/
#include <assert.h>
#include <complex.h>
#include <math.h>
#include <stdbool.h>
#include <stdint.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include "prb_dl.h"
#include "srsran/phy/common/phy_common.h"
#include "srsran/phy/phch/npbch.h"
#include "srsran/phy/phch/ra_nbiot.h"
#include "srsran/phy/utils/bit.h"
#include "srsran/phy/utils/debug.h"
#include "srsran/phy/utils/vector.h"
#define SRSRAN_NBIOT_NPBCH_NUM_REFS_PER_SYMB 4
// Table 5.3.1.1-1 in 36.212 v13.3.0
const uint8_t srsran_npbch_crc_mask[4][16] = {{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1, 1},
{0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0},
{0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1, 0, 1}};
/** Initializes the NPBCH transmitter and receiver.
* At the receiver, the field nof_ports in the cell structure indicates the
* maximum number of BS transmitter ports to look for.
*/
int srsran_npbch_init(srsran_npbch_t* q)
{
int ret = SRSRAN_ERROR_INVALID_INPUTS;
if (q != NULL) {
bzero(q, sizeof(srsran_npbch_t));
ret = SRSRAN_ERROR;
q->nof_symbols = SRSRAN_NPBCH_NUM_RE;
if (srsran_modem_table_lte(&q->mod, SRSRAN_MOD_QPSK)) {
fprintf(stderr, "Error initiating modem table.\n");
goto clean;
}
int poly[3] = {0x6D, 0x4F, 0x57};
if (srsran_viterbi_init(&q->decoder, SRSRAN_VITERBI_37, poly, SRSRAN_MIB_NB_CRC_LEN, true)) {
fprintf(stderr, "Error initiating Viterbi.\n");
goto clean;
}
if (srsran_crc_init(&q->crc, SRSRAN_LTE_CRC16, 16)) {
fprintf(stderr, "Error initiating CRC object.\n");
goto clean;
}
q->encoder.K = 7;
q->encoder.R = 3;
q->encoder.tail_biting = true;
memcpy(q->encoder.poly, poly, 3 * sizeof(int));
q->d = srsran_vec_cf_malloc(q->nof_symbols);
if (!q->d) {
fprintf(stderr, "Error allocating memory.\n");
goto clean;
}
for (uint32_t i = 0; i < SRSRAN_MAX_PORTS; i++) {
q->ce[i] = srsran_vec_cf_malloc(q->nof_symbols);
if (!q->ce[i]) {
fprintf(stderr, "Error allocating memory.\n");
goto clean;
}
q->x[i] = srsran_vec_cf_malloc(q->nof_symbols);
if (!q->x[i]) {
fprintf(stderr, "Error allocating memory.\n");
goto clean;
}
q->symbols[i] = srsran_vec_cf_malloc(q->nof_symbols * SRSRAN_NPBCH_NUM_FRAMES);
if (!q->symbols[i]) {
fprintf(stderr, "Error allocating memory.\n");
goto clean;
}
}
q->llr = srsran_vec_f_malloc(q->nof_symbols * SRSRAN_NPBCH_NUM_FRAMES * 2);
if (!q->llr) {
fprintf(stderr, "Error allocating memory.\n");
goto clean;
}
q->temp = srsran_vec_f_malloc(q->nof_symbols * SRSRAN_NPBCH_NUM_FRAMES * 2);
if (!q->temp) {
fprintf(stderr, "Error allocating memory.\n");
goto clean;
}
q->rm_b = srsran_vec_u8_malloc(q->nof_symbols * SRSRAN_NPBCH_NUM_FRAMES * 2);
if (!q->rm_b) {
fprintf(stderr, "Error allocating memory.\n");
goto clean;
}
ret = SRSRAN_SUCCESS;
}
clean:
if (ret == SRSRAN_ERROR) {
srsran_npbch_free(q);
}
return ret;
}
void srsran_npbch_free(srsran_npbch_t* q)
{
if (q->d) {
free(q->d);
}
for (uint32_t i = 0; i < SRSRAN_MAX_PORTS; i++) {
if (q->ce[i]) {
free(q->ce[i]);
}
if (q->x[i]) {
free(q->x[i]);
}
if (q->symbols[i]) {
free(q->symbols[i]);
}
}
if (q->llr) {
free(q->llr);
}
if (q->temp) {
free(q->temp);
}
if (q->rm_b) {
free(q->rm_b);
}
for (uint32_t i = 0; i < SRSRAN_NPBCH_NUM_BLOCKS; i++) {
srsran_sequence_free(&q->seq_r14[i]);
}
srsran_sequence_free(&q->seq);
srsran_modem_table_free(&q->mod);
srsran_viterbi_free(&q->decoder);
}
int srsran_npbch_set_cell(srsran_npbch_t* q, srsran_nbiot_cell_t cell)
{
int ret = SRSRAN_ERROR_INVALID_INPUTS;
if (q != NULL && srsran_nbiot_cell_isvalid(&cell)) {
// set ports configuration
if (cell.nof_ports == 0) {
q->search_all_ports = true;
cell.nof_ports = SRSRAN_NBIOT_MAX_PORTS;
} else {
q->search_all_ports = false;
}
if (q->cell.n_id_ncell != cell.n_id_ncell || q->cell.base.nof_prb == 0) {
q->cell = cell;
if (srsran_sequence_npbch(&q->seq, q->cell.base.cp, q->cell.n_id_ncell)) {
fprintf(stderr, "Error initiating NPBCH sequence.\n");
return SRSRAN_ERROR;
}
// pre-compute the 8 rotation sequences for R14
if (q->cell.is_r14) {
for (uint32_t i = 0; i < SRSRAN_NPBCH_NUM_BLOCKS; i++) {
if (srsran_sequence_npbch_r14(&q->seq_r14[i], q->cell.n_id_ncell, i)) {
return SRSRAN_ERROR;
}
}
}
}
ret = SRSRAN_SUCCESS;
}
return ret;
}
/** Packs the MIB-NB, according to TS 36.331 v13.2.0 Section 6.7.2
*/
void srsran_npbch_mib_pack(uint32_t hfn, uint32_t sfn, srsran_mib_nb_t mib, uint8_t* payload)
{
uint8_t* msg = payload;
bzero(msg, SRSRAN_MIB_NB_LEN);
// System Frame Number (SFN), 4 MSB
srsran_bit_unpack(sfn >> 6, &msg, 4);
// Hyper Frame Number (HFB), 2 LSB
srsran_bit_unpack(hfn, &msg, 2);
// schedulingInfoSIB1, integer 0-15, 4 bits
srsran_bit_unpack(mib.sched_info_sib1, &msg, 4);
// system info value tag, integer 0-31, 5 bits
srsran_bit_unpack(mib.sys_info_tag, &msg, 5);
// access barring enabled, 1 bit
srsran_bit_unpack(mib.ac_barring, &msg, 1);
// operation mode info, 2 for mode + 5 for config, 7 bits in total
srsran_bit_unpack(mib.mode, &msg, 2);
// 11 spare bits
}
/** Unpacks MIB-NB from NPBCH message.
* msg buffer must be 34 byte length at least
*/
void srsran_npbch_mib_unpack(uint8_t* msg, srsran_mib_nb_t* mib)
{
if (mib) {
mib->sfn = (srsran_bit_pack(&msg, 4) << 6) & 0x3C0;
mib->hfn = srsran_bit_pack(&msg, 2) & 0x3;
mib->sched_info_sib1 = srsran_bit_pack(&msg, 4) & 0x0000ffff;
mib->sys_info_tag = srsran_bit_pack(&msg, 5) & 0x0001ffff;
mib->ac_barring = srsran_bit_pack(&msg, 1) & 0x1;
mib->mode = srsran_bit_pack(&msg, 2) & 0x0000000B;
}
}
void srsran_mib_nb_printf(FILE* stream, srsran_nbiot_cell_t cell, srsran_mib_nb_t* mib)
{
fprintf(stream, " - N_id_ncell: %d\n", cell.n_id_ncell);
fprintf(stream, " - Release: %s\n", cell.is_r14 ? "r14" : "r13");
fprintf(stream, " - Nof ports: %d\n", cell.nof_ports);
fprintf(stream, " - SFN: %d\n", mib->sfn);
fprintf(stream, " - HFN (2 LSB): %d\n", mib->hfn);
fprintf(stream, " - Sched. Info SIB1 %d\n", mib->sched_info_sib1);
fprintf(stream, " - First frame %d\n", srsran_ra_nbiot_get_starting_sib1_frame(cell.n_id_ncell, mib));
fprintf(stream, " - #repetitions %d\n", srsran_ra_n_rep_sib1_nb(mib));
fprintf(stream, " - TBS %d\n", srsran_ra_nbiot_get_sib1_tbs(mib));
fprintf(stream, " - System Info Val %d\n", mib->sys_info_tag);
fprintf(stream, " - AC barring %s\n", mib->ac_barring ? "Yes" : "No");
fprintf(stream, " - Operating mode %s\n", srsran_nbiot_mode_string(mib->mode));
}
int srsran_npbch_put_subframe(srsran_npbch_t* q,
uint8_t bch_payload[SRSRAN_MIB_NB_LEN],
cf_t* sf[SRSRAN_MAX_PORTS],
uint32_t frame_idx)
{
return srsran_npbch_encode(q, bch_payload, sf, frame_idx);
}
/** Converts the MIB-NB message to symbols mapped to the first subframe,
* The MIB-NB is split over 8 blocks, each of which is repeated 8 times, always in SF0,
* it therefore lasts for 640ms.
*/
int srsran_npbch_encode(srsran_npbch_t* q,
uint8_t bch_payload[SRSRAN_MIB_NB_LEN],
cf_t* sf[SRSRAN_MAX_PORTS],
uint32_t frame_idx)
{
int block_idx = (frame_idx / SRSRAN_NPBCH_NUM_REP) % SRSRAN_NPBCH_NUM_BLOCKS;
cf_t* x[SRSRAN_MAX_LAYERS];
if (q != NULL && bch_payload != NULL && q->cell.nof_ports != 0) {
for (int i = 0; i < q->cell.nof_ports; i++) {
if (sf[i] == NULL) {
return SRSRAN_ERROR_INVALID_INPUTS;
}
}
// Set pointers for layermapping & precoding
int nof_bits = 2 * q->nof_symbols;
// number of layers equals number of ports
for (int i = 0; i < q->cell.nof_ports; i++) {
x[i] = q->x[i];
}
memset(&x[q->cell.nof_ports], 0, sizeof(cf_t*) * (SRSRAN_MAX_LAYERS - q->cell.nof_ports));
// generate new BCH message every 64 frames
if ((frame_idx % SRSRAN_NPBCH_NUM_FRAMES) == 0) {
INFO("Encoding new NPBCH signal in frame %d.", frame_idx);
memcpy(q->data, bch_payload, sizeof(uint8_t) * SRSRAN_MIB_NB_LEN);
// encode and rate-match
srsran_crc_attach(&q->crc, q->data, SRSRAN_MIB_NB_LEN);
srsran_npbch_crc_set_mask(q->data, q->cell.nof_ports);
srsran_convcoder_encode(&q->encoder, q->data, q->data_enc, SRSRAN_MIB_NB_CRC_LEN);
srsran_rm_conv_tx(q->data_enc, SRSRAN_MIB_NB_ENC_LEN, q->rm_b, SRSRAN_NPBCH_NUM_BLOCKS * nof_bits);
}
// Scramble and modulate a new block every 8 frames
if (frame_idx % SRSRAN_NPBCH_NUM_REP == 0) {
INFO("Modulating MIB-NB block %d in frame %d.", block_idx, frame_idx);
srsran_scrambling_b_offset(&q->seq, &q->rm_b[block_idx * nof_bits], block_idx * nof_bits, nof_bits);
srsran_mod_modulate(&q->mod, &q->rm_b[block_idx * nof_bits], q->d, nof_bits);
// layer mapping & precoding
if (q->cell.nof_ports > 1) {
srsran_layermap_diversity(q->d, x, q->cell.nof_ports, q->nof_symbols);
srsran_precoding_diversity(x, q->symbols, q->cell.nof_ports, q->nof_symbols / q->cell.nof_ports, 1.0);
} else {
memcpy(q->symbols[0], q->d, q->nof_symbols * sizeof(cf_t));
}
}
// Write exactly SRSRAN_NPBCH_NUM_RE (assumes symbols have been modulated before)
for (int i = 0; i < q->cell.nof_ports; i++) {
if (q->cell.is_r14) {
DEBUG("Applying phase rotation on port %d in frame %d.", i, frame_idx);
srsran_npbch_rotate(q, frame_idx, q->symbols[i], q->symbols[i], q->nof_symbols, false);
}
DEBUG("Putting MIB-NB block %d on port %d in frame %d.", block_idx, i, frame_idx);
if (srsran_npbch_cp(q->symbols[i], sf[i], q->cell, true) != SRSRAN_NPBCH_NUM_RE) {
INFO("Error while mapping NPBCH symbols.");
return SRSRAN_ERROR;
}
}
return SRSRAN_SUCCESS;
} else {
return SRSRAN_ERROR_INVALID_INPUTS;
}
}
int srsran_npbch_rotate(srsran_npbch_t* q,
uint32_t nf,
cf_t* input_signal,
cf_t* output_signal,
int num_samples,
bool back)
{
// Generate frame specific scrambling sequence for symbol rotation
DEBUG("%sotating NPBCH in SFN=%d", back ? "De-R" : "R", nf);
for (int i = 0; i < num_samples; i++) {
int c_2i = q->seq_r14[nf % 8].c[2 * i];
int c_2ip1 = q->seq_r14[nf % 8].c[2 * i + 1];
#if 1
cf_t phi_f = 0;
if (c_2i == 0 && c_2ip1 == 0)
phi_f = 1;
else if (c_2i == 0 && c_2ip1 == 1)
phi_f = -1;
else if (c_2i == 1 && c_2ip1 == 0)
phi_f = _Complex_I;
else if (c_2i == 1 && c_2ip1 == 1)
phi_f = -_Complex_I;
#else
cf_t phi_f = (c_2i == 0) ? 1 : _Complex_I;
if (c_2ip1 == 0)
phi_f *= -1;
#endif
output_signal[i] = back ? input_signal[i] / phi_f : input_signal[i] * phi_f;
if (SRSRAN_VERBOSE_ISDEBUG()) {
printf("i=%d c_2i=%d, c_2i+1=%d -> phi_f=", i, c_2i, c_2ip1);
srsran_vec_fprint_c(stdout, &phi_f, 1);
printf("input:\n");
srsran_vec_fprint_c(stdout, &input_signal[i], 1);
printf("output:\n");
srsran_vec_fprint_c(stdout, &output_signal[i], 1);
printf("\n\n");
}
}
return SRSRAN_SUCCESS;
}
/* Decodes the NPBCH channel
*
* The NPBCH spans over 640 ms. This function is called every 10 ms. It tries to decode the MIB
* given the symbols of a subframe (1 ms). Successive calls will use more subframes
* to help the decoding process.
*
* Returns 1 if successfully decoded MIB-NB, 0 if not and -1 on error
*/
int srsran_npbch_decode_nf(srsran_npbch_t* q,
cf_t* sf_symbols,
cf_t* ce[SRSRAN_MAX_PORTS],
float noise_estimate,
uint8_t bch_payload[SRSRAN_MIB_NB_LEN],
uint32_t* nof_tx_ports,
int* sfn_offset,
int nf)
{
cf_t* x[SRSRAN_MAX_LAYERS] = {NULL};
int ret = SRSRAN_ERROR_INVALID_INPUTS;
if (q != NULL && sf_symbols != NULL && q->cell.nof_ports != 0) {
for (int i = 0; i < q->cell.nof_ports; i++) {
if (ce[i] == NULL) {
return ret;
}
}
ret = SRSRAN_ERROR;
// Set pointers for layermapping & precoding
int nof_bits = 2 * q->nof_symbols;
// number of layers equals number of ports
for (int i = 0; i < SRSRAN_MAX_PORTS; i++) {
x[i] = q->x[i];
}
// extract symbols
int nof_ext_syms = srsran_npbch_cp(sf_symbols, q->symbols[0], q->cell, false);
if (q->nof_symbols != nof_ext_syms) {
fprintf(stderr, "There was an error getting the PBCH symbols\n");
return ret;
}
if (q->cell.is_r14) {
// de-rotate symbols
srsran_npbch_rotate(q, nf, q->symbols[0], q->symbols[0], q->nof_symbols, true);
}
// extract channel estimates
for (int i = 0; i < q->cell.nof_ports; i++) {
if (q->nof_symbols != srsran_npbch_cp(ce[i], q->ce[i], q->cell, false)) {
fprintf(stderr, "There was an error getting the PBCH symbols\n");
return ret;
}
}
q->frame_idx++;
ret = 0;
// Try decoding for 1 to cell.nof_ports antennas
uint32_t nant = q->cell.nof_ports;
if (q->search_all_ports) {
nant = 1;
}
do {
if (nant != 3) {
DEBUG("Trying %d TX antennas with %d frames", nant, q->frame_idx);
// in control channels, only diversity is supported
if (nant == 1) {
// no need for layer demapping
srsran_predecoding_single(q->symbols[0], q->ce[0], q->d, NULL, q->nof_symbols, 1.0, noise_estimate);
} else {
srsran_predecoding_diversity(q->symbols[0], q->ce, x, nant, q->nof_symbols, 1.0);
srsran_layerdemap_diversity(x, q->d, nant, q->nof_symbols / nant);
}
// demodulate symbols
srsran_demod_soft_demodulate(SRSRAN_MOD_QPSK, q->d, &q->llr[nof_bits * (q->frame_idx - 1)], q->nof_symbols);
// only one subframe
DEBUG("Trying to decode NPBCH ..");
// TODO: simplified decoding only using first MIB block
ret = srsran_npbch_decode_frame(q, 0, nf, 1, nof_bits, nant);
if (ret == SRSRAN_SUCCESS) {
if (sfn_offset) {
*sfn_offset = (int)0;
}
if (nof_tx_ports) {
*nof_tx_ports = nant;
}
if (bch_payload) {
memcpy(bch_payload, q->data, sizeof(uint8_t) * SRSRAN_MIB_NB_LEN);
}
INFO("Successfully decoded NPBCH sfn_offset=%d", q->frame_idx - 1);
q->frame_idx = 0;
return ret;
}
}
nant++;
} while (nant <= q->cell.nof_ports);
q->frame_idx = 0;
}
return ret;
}
int srsran_npbch_decode(srsran_npbch_t* q,
cf_t* sf_symbols,
cf_t* ce[SRSRAN_MAX_PORTS],
float noise_estimate,
uint8_t bch_payload[SRSRAN_MIB_NB_LEN],
uint32_t* nof_tx_ports,
int* sfn_offset)
{
return srsran_npbch_decode_nf(q, sf_symbols, ce, noise_estimate, bch_payload, nof_tx_ports, sfn_offset, 0);
}
void srsran_npbch_decode_reset(srsran_npbch_t* q)
{
q->frame_idx = 0;
}
int srsran_npbch_decode_frame(srsran_npbch_t* q,
uint32_t src,
uint32_t dst,
uint32_t n,
uint32_t nof_bits,
uint32_t nof_ports)
{
srsran_vec_f_copy(&q->temp[dst * nof_bits], &q->llr[src * nof_bits], n * nof_bits);
// descramble
srsran_scrambling_f_offset(&q->seq, &q->temp[dst * nof_bits], dst * nof_bits, n * nof_bits);
for (int j = 0; j < dst * nof_bits; j++) {
q->temp[j] = SRSRAN_RX_NULL;
}
for (int j = (dst + n) * nof_bits; j < SRSRAN_NPBCH_NUM_BLOCKS * nof_bits; j++) {
q->temp[j] = SRSRAN_RX_NULL;
}
// unrate matching
srsran_rm_conv_rx(q->temp, SRSRAN_NPBCH_NUM_BLOCKS * nof_bits, q->rm_f, SRSRAN_MIB_NB_ENC_LEN);
// Normalize LLR
srsran_vec_sc_prod_fff(q->rm_f, 1.0 / ((float)2 * n), q->rm_f, SRSRAN_MIB_NB_ENC_LEN);
// decode
srsran_viterbi_decode_f(&q->decoder, q->rm_f, q->data, SRSRAN_MIB_NB_CRC_LEN);
if (srsran_npbch_crc_check(q, q->data, nof_ports) == 0) {
return SRSRAN_SUCCESS;
} else {
return SRSRAN_ERROR;
}
}
void srsran_npbch_crc_set_mask(uint8_t* data, int nof_ports)
{
int i;
for (i = 0; i < 16; i++) {
data[SRSRAN_MIB_NB_LEN + i] = (data[SRSRAN_MIB_NB_LEN + i] + srsran_npbch_crc_mask[nof_ports - 1][i]) % 2;
}
}
/* Checks CRC after applying the mask for the given number of ports.
*
* The bits buffer size must be at least 50 bytes.
*
* Returns 0 if the data is correct, -1 otherwise
*/
uint32_t srsran_npbch_crc_check(srsran_npbch_t* q, uint8_t* bits, uint32_t nof_ports)
{
uint8_t data[SRSRAN_MIB_NB_CRC_LEN];
memcpy(data, bits, SRSRAN_MIB_NB_CRC_LEN * sizeof(uint8_t));
srsran_npbch_crc_set_mask(data, nof_ports);
int ret = srsran_crc_checksum(&q->crc, data, SRSRAN_MIB_NB_CRC_LEN);
if (ret == 0) {
uint32_t chkzeros = 0;
for (int i = 0; i < SRSRAN_MIB_NB_LEN; i++) {
chkzeros += data[i];
}
if (chkzeros) {
return 0;
} else {
return SRSRAN_ERROR;
}
} else {
return ret;
}
}
/* NPBCH starts at the fourth symbol of the sub-frame,
* We need to assume two antenna ports for NRS and
* four ports for CRS
* Returns the number of symbols written/read
*/
int srsran_npbch_cp(cf_t* input, cf_t* output, srsran_nbiot_cell_t cell, bool put)
{
cf_t * in_ptr = input, *out_ptr = output;
uint32_t offset = 0; // the number of REs left out before start of the REF signal RE
uint32_t delta = 3 * cell.base.nof_prb * SRSRAN_NRE + cell.nbiot_prb * SRSRAN_NRE;
if (put) {
out_ptr += delta;
} else {
in_ptr += delta;
}
for (uint32_t l = 3; l < SRSRAN_CP_NORM_SF_NSYMB; l++) {
delta = 0;
if (l == 3 || l == 9 || l == 10) {
// copy entire symbol
prb_cp(&in_ptr, &out_ptr, 1);
} else {
// skip LTE CRS and NRS and always assume 4 reference symbols per OFDM symbol
offset = cell.n_id_ncell % 3;
prb_cp_ref(
&in_ptr, &out_ptr, offset, SRSRAN_NBIOT_NPBCH_NUM_REFS_PER_SYMB, SRSRAN_NBIOT_NPBCH_NUM_REFS_PER_SYMB, put);
delta = (cell.n_id_ncell % 3 == 2 ? 1 : 0);
}
if (put) {
out_ptr += delta;
} else {
in_ptr += delta;
}
}
int r;
if (put) {
r = abs((int)(input - in_ptr));
} else {
r = abs((int)(output - out_ptr));
}
return r;
}
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