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srsLTE
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srsLTE/lte/examples/cell_search_utils.c

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/**
*
* \section COPYRIGHT
*
* Copyright 2013-2014 The libLTE Developers. See the
* COPYRIGHT file at the top-level directory of this distribution.
*
* \section LICENSE
*
* This file is part of the libLTE library.
*
* libLTE is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3 of
* the License, or (at your option) any later version.
*
* libLTE 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 Lesser General Public License for more details.
*
* A copy of the GNU Lesser 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 <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
#include <unistd.h>
#include <math.h>
#include <sys/time.h>
#include <unistd.h>
#include "liblte/phy/phy.h"
#include "liblte/rrc/rrc.h"
#include "cell_search_utils.h"
#ifndef DISABLE_UHD
#include "liblte/cuhd/cuhd.h"
int decode_pbch(void *uhd, ue_celldetect_result_t *found_cell, uint32_t nof_frames_total,
uint8_t bch_payload[BCH_PAYLOAD_LEN], uint32_t *nof_tx_ports, uint32_t *sfn_offset)
{
ue_mib_t uemib;
int n;
int ret = LIBLTE_ERROR;
uint32_t nof_frames = 0;
uint32_t flen = MIB_FRAME_SIZE_SEARCH;
cf_t *buffer = vec_malloc(sizeof(cf_t) * flen);
if (!buffer) {
perror("malloc");
goto free_and_exit;
}
if (ue_mib_init_1_92(&uemib, found_cell->cell_id, found_cell->cp)) {
fprintf(stderr, "Error initiating PBCH decoder\n");
goto free_and_exit;
}
INFO("Setting sampling frequency 1.92 MHz for PBCH decoding\n", 0);
cuhd_set_rx_srate(uhd, 1920000.0);
INFO("Starting receiver...\n", 0);
cuhd_start_rx_stream(uhd);
do {
if (cuhd_recv(uhd, buffer, flen, 1)<0) {
fprintf(stderr, "Error receiving from USRP\n");
goto free_and_exit;
}
DEBUG("Calling ue_mib_decode() %d/%d\n", nof_frames, nof_frames_total);
n = ue_mib_sync_and_decode_1_92(&uemib, buffer, flen);
if (n == LIBLTE_ERROR || n == LIBLTE_ERROR_INVALID_INPUTS) {
fprintf(stderr, "Error calling ue_mib_decode()\n");
goto free_and_exit;
}
if (n == MIB_FRAME_UNALIGNED) {
INFO("Realigning frame\n",0);
// Receive some randon number of samples to try to resynchronise the frame.
if (cuhd_recv(uhd, buffer, 1500, 1)<0) {
fprintf(stderr, "Error receiving from USRP\n");
goto free_and_exit;
}
bzero(buffer, flen * sizeof(cf_t));
}
nof_frames++;
} while (n != MIB_FOUND && nof_frames < 2*nof_frames_total);
if (n == MIB_FOUND) {
printf("\n\nMIB decoded in %d ms (%d half frames)\n", nof_frames*5, nof_frames);
ue_mib_get_payload(&uemib, bch_payload, nof_tx_ports, sfn_offset);
ret = LIBLTE_SUCCESS;
} else {
ret = LIBLTE_ERROR;
}
free_and_exit:
free(buffer);
cuhd_stop_rx_stream(uhd);
cuhd_flush_buffer(uhd);
ue_mib_free(&uemib);
return ret;
}
int detect_cell(cell_detect_cfg_t *config, void *uhd, ue_celldetect_result_t *found_cell, uint32_t N_id_2)
{
int ret = LIBLTE_ERROR;
ue_celldetect_t cd;
cf_t *buffer = vec_malloc(sizeof(cf_t) * 96000);
if (!buffer) {
perror("malloc");
goto free_and_exit;
}
if (ue_celldetect_init(&cd)) {
fprintf(stderr, "Error initiating UE cell detect\n");
goto free_and_exit;
}
if (config->nof_frames_detected) {
ue_celldetect_set_nof_frames_detected(&cd, config->nof_frames_detected);
}
if (config->nof_frames_total) {
ue_celldetect_set_nof_frames_total(&cd, config->nof_frames_total);
}
if (config->threshold) {
ue_celldetect_set_threshold(&cd, config->threshold);
}
INFO("Setting sampling frequency 960 KHz for PSS search\n", 0);
cuhd_set_rx_srate(uhd, 960000.0);
INFO("Starting receiver...\n", 0);
cuhd_start_rx_stream(uhd);
uint32_t flen = 4800;
int n;
bzero(found_cell, sizeof(ue_celldetect_result_t));
ue_celldetect_set_N_id_2(&cd, N_id_2);
do {
if (cuhd_recv(uhd, buffer, flen, 1)<0) {
fprintf(stderr, "Error receiving from USRP\n");
goto free_and_exit;
}
DEBUG("Scanning cell at N_id_2=%d\n",N_id_2);
n = ue_celldetect_scan(&cd, buffer, flen);
switch(n) {
case CS_FRAME_UNALIGNED:
INFO("Realigning frame\n",0);
if (cuhd_recv(uhd, buffer, flen/2, 1)<0) {
fprintf(stderr, "Error receiving from USRP\n");
goto free_and_exit;
}
break;
case CS_CELL_DETECTED:
ue_celldetect_get_cell(&cd, found_cell);
if (found_cell->peak > 0) {
printf("\n\tCELL ID: %d, CP: %s, Peak: %.2f, Mode: %d/%d\n",
found_cell->cell_id,
lte_cp_string(found_cell->cp),
found_cell->peak, found_cell->mode,
cd.nof_frames_detected);
}
ret = 1;
INFO("Cell found at N_id_2=%d\n",N_id_2);
break;
case CS_CELL_NOT_DETECTED:
ret = 0;
DEBUG("No cell found at N_id_2=%d\n",N_id_2);
break;
case LIBLTE_ERROR:
case LIBLTE_ERROR_INVALID_INPUTS:
ret = LIBLTE_ERROR;
fprintf(stderr, "Error calling cellsearch_scan()\n");
goto free_and_exit;
}
} while(n == 0 || n == CS_FRAME_UNALIGNED);
free_and_exit:
free(buffer);
ue_celldetect_free(&cd);
INFO("Stopping receiver...\n", 0);
cuhd_stop_rx_stream(uhd);
cuhd_flush_buffer(uhd);
return ret;
}
int detect_all_cells(cell_detect_cfg_t *config, void *uhd, ue_celldetect_result_t found_cell[3])
{
uint32_t N_id_2;
int ret;
int nof_detected_cells = 0;
for (N_id_2=0;N_id_2<3;N_id_2++) {
ret = detect_cell(config, uhd, &found_cell[N_id_2], N_id_2);
if (ret == 1) {
nof_detected_cells++;
} else if (ret == LIBLTE_ERROR) {
return LIBLTE_ERROR;
}
}
return nof_detected_cells;
}
int detect_and_decode_cell(cell_detect_cfg_t *config, void *uhd, int force_N_id_2, lte_cell_t *cell)
{
int ret;
uint32_t nof_tx_ports;
uint8_t bch_payload[BCH_PAYLOAD_LEN], bch_payload_unpacked[BCH_PAYLOAD_LEN];
ue_celldetect_result_t found_cells[3];
bzero(found_cells, 3*sizeof(ue_celldetect_result_t));
if (force_N_id_2 >= 0) {
ret = detect_cell(config, uhd, &found_cells[force_N_id_2], force_N_id_2);
} else {
ret = detect_all_cells(config, uhd, found_cells);
}
if (ret < 0) {
fprintf(stderr, "Error searching cell\n");
exit(-1);
}
int max_peak_cell = 0;
float max_peak_value = -1.0;
if (ret > 0) {
if (force_N_id_2 >= 0) {
max_peak_cell = force_N_id_2;
} else {
for (int i=0;i<3;i++) {
if (found_cells[i].peak > max_peak_value) {
max_peak_value = found_cells[i].peak;
max_peak_cell = i;
}
}
}
printf("Decoding PBCH for cell %d (N_id_2=%d)\n", found_cells[max_peak_cell].cell_id, max_peak_cell);
if (decode_pbch(uhd, &found_cells[max_peak_cell], 400, bch_payload, &nof_tx_ports, NULL)) {
fprintf(stderr, "Could not decode PBCH from CELL ID %d\n", found_cells[max_peak_cell].cell_id);
return LIBLTE_ERROR;
}
} else {
fprintf(stderr, "Could not find any cell in this frequency\n");
return LIBLTE_ERROR;
}
cell->cp = found_cells[max_peak_cell].cp;
cell->id = found_cells[max_peak_cell].cell_id;
cell->nof_ports = nof_tx_ports;
bit_unpack_vector(bch_payload, bch_payload_unpacked, BCH_PAYLOAD_LEN);
printf("nof_bits: %d\n", BCH_PAYLOAD_LEN);
vec_fprint_hex(stdout, bch_payload, BCH_PAYLOAD_LEN);
bcch_bch_unpack(bch_payload_unpacked, BCH_PAYLOAD_LEN, cell, NULL);
/* set sampling frequency */
int srate = lte_sampling_freq_hz(cell->nof_prb);
if (srate != -1) {
cuhd_set_rx_srate(uhd, (double) srate);
} else {
fprintf(stderr, "Invalid number of PRB %d\n", cell->nof_prb);
return LIBLTE_ERROR;
}
return LIBLTE_SUCCESS;
}
#endif
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