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01dc85f74299a99cdbefb3fca535fc097583d9b5
openairinterface5g/openair1/PHY/NR_UE_TRANSPORT/pss_nr.c
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laurent 01dc85f742 fix review comments
2022-09-22 18:53:14 +02:00

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/*
* Licensed to the OpenAirInterface (OAI) Software Alliance under one or more
* contributor license agreements. See the NOTICE file distributed with
* this work for additional information regarding copyright ownership.
* The OpenAirInterface Software Alliance licenses this file to You under
* the OAI Public License, Version 1.1 (the "License"); you may not use this file
* except in compliance with the License.
* You may obtain a copy of the License at
*
* http://www.openairinterface.org/?page_id=698
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS,
* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
* See the License for the specific language governing permissions and
* limitations under the License.
*-------------------------------------------------------------------------------
* For more information about the OpenAirInterface (OAI) Software Alliance:
* contact@openairinterface.org
*/
/**********************************************************************
*
* FILENAME : pss_nr.c
*
* MODULE : synchronisation signal
*
* DESCRIPTION : generation of pss
* 3GPP TS 38.211 7.4.2.2 Primary synchronisation signal
*
************************************************************************/
#include <stdio.h>
#include <assert.h>
#include <errno.h>
#include <math.h>
#include <nr-uesoftmodem.h>
#include "PHY/defs_nr_UE.h"
#include "PHY/NR_REFSIG/ss_pbch_nr.h"
#include "common/utils/LOG/vcd_signal_dumper.h"
#define DEFINE_VARIABLES_PSS_NR_H
#include "PHY/NR_REFSIG/pss_nr.h"
#undef DEFINE_VARIABLES_PSS_NR_H
#include "PHY/NR_REFSIG/sss_nr.h"
#include "PHY/NR_UE_TRANSPORT/cic_filter_nr.h"
//#define DBG_PSS_NR
/*******************************************************************
*
* NAME : generate_pss_nr
*
* PARAMETERS : N_ID_2 : element 2 of physical layer cell identity
* value : { 0, 1, 2}
*
* RETURN : generate binary pss sequence (this is a m-sequence)
*
* DESCRIPTION : 3GPP TS 38.211 7.4.2.2 Primary synchronisation signal
* Sequence generation
*
*********************************************************************/
void generate_pss_nr(NR_DL_FRAME_PARMS *fp,int N_ID_2)
{
AssertFatal(fp->ofdm_symbol_size > 127,"Illegal ofdm_symbol_size %d\n",fp->ofdm_symbol_size);
AssertFatal(N_ID_2>=0 && N_ID_2 <=2,"Illegal N_ID_2 %d\n",N_ID_2);
int16_t d_pss[LENGTH_PSS_NR];
int16_t x[LENGTH_PSS_NR];
int16_t *primary_synchro_time = primary_synchro_time_nr[N_ID_2];
unsigned int length = fp->ofdm_symbol_size;
unsigned int size = length * IQ_SIZE; /* i & q */
int16_t *primary_synchro = primary_synchro_nr[N_ID_2]; /* pss in complex with alternatively i then q */
int16_t *primary_synchro2 = primary_synchro_nr2[N_ID_2]; /* pss in complex with alternatively i then q */
#define INITIAL_PSS_NR (7)
const int x_initial[INITIAL_PSS_NR] = {0, 1, 1 , 0, 1, 1, 1};
assert(N_ID_2 < NUMBER_PSS_SEQUENCE);
assert(size <= SYNCF_TMP_SIZE);
assert(size <= SYNC_TMP_SIZE);
bzero(synchroF_tmp, size);
bzero(synchro_tmp, size);
for (int i=0; i < INITIAL_PSS_NR; i++) {
x[i] = x_initial[i];
}
for (int i=0; i < (LENGTH_PSS_NR - INITIAL_PSS_NR); i++) {
x[i+INITIAL_PSS_NR] = (x[i + 4] + x[i])%(2);
}
for (int n=0; n < LENGTH_PSS_NR; n++) {
int m = (n + 43*N_ID_2)%(LENGTH_PSS_NR);
d_pss[n] = 1 - 2*x[m];
}
/* PSS is directly mapped to subcarrier without modulation 38.211 */
for (int i=0; i < LENGTH_PSS_NR; i++) {
#if 1
primary_synchro[2*i] = (d_pss[i] * SHRT_MAX)>>SCALING_PSS_NR; /* Maximum value for type short int ie int16_t */
primary_synchro[2*i+1] = 0;
primary_synchro2[i] = d_pss[i];
#else
primary_synchro[2*i] = d_pss[i] * AMP;
primary_synchro[2*i+1] = 0;
primary_synchro2[i] = d_pss[i];
#endif
}
#ifdef DBG_PSS_NR
if (N_ID_2 == 0) {
char output_file[255];
char sequence_name[255];
sprintf(output_file, "pss_seq_%d_%u.m", N_ID_2, length);
sprintf(sequence_name, "pss_seq_%d_%u", N_ID_2, length);
printf("file %s sequence %s\n", output_file, sequence_name);
LOG_M(output_file, sequence_name, primary_synchro, LENGTH_PSS_NR, 1, 1);
}
#endif
/* call of IDFT should be done with ordered input as below
*
* n input samples
* <------------------------------------------------>
* 0 n
* are written into input buffer for IFFT
* -------------------------------------------------
* |xxxxxxx N/2 xxxxxxxx|
* --------------------------------------------------
* ^ ^ ^ ^ ^
* | | | | |
* n/2 end of n=0 start of n/2-1
* pss pss
*
* Frequencies
* positives negatives
* 0 (+N/2)(-N/2)
* |-----------------------><-------------------------|
*
* sample 0 is for continuous frequency which is used here
*/
unsigned int k = fp->first_carrier_offset + fp->ssb_start_subcarrier + 56; //and
if (k>= fp->ofdm_symbol_size) k-=fp->ofdm_symbol_size;
for (int i=0; i < LENGTH_PSS_NR; i++) {
synchroF_tmp[2*k] = primary_synchro[2*i];
synchroF_tmp[2*k+1] = primary_synchro[2*i+1];
k++;
if (k == length) k=0;
}
/* IFFT will give temporal signal of Pss */
idft((int16_t)get_idft(length),
synchroF_tmp, /* complex input */
synchro_tmp, /* complex output */
1); /* scaling factor */
/* then get final pss in time */
for (unsigned int i=0; i<length; i++) {
((int32_t *)primary_synchro_time)[i] = ((int32_t *)synchro_tmp)[i];
}
#ifdef DBG_PSS_NR
if (N_ID_2 == 0) {
char output_file[255];
char sequence_name[255];
sprintf(output_file, "%s%d_%u%s","pss_seq_t_", N_ID_2, length, ".m");
sprintf(sequence_name, "%s%d_%u","pss_seq_t_", N_ID_2, length);
printf("file %s sequence %s\n", output_file, sequence_name);
LOG_M(output_file, sequence_name, primary_synchro_time, length, 1, 1);
sprintf(output_file, "%s%d_%u%s","pss_seq_f_", N_ID_2, length, ".m");
sprintf(sequence_name, "%s%d_%u","pss_seq_f_", N_ID_2, length);
LOG_M(output_file, sequence_name, synchroF_tmp, length, 1, 1);
}
#endif
#if 0
/* it allows checking that process of idft on a signal and then dft gives same signal with limited errors */
if ((N_ID_2 == 0) && (length == 256)) {
LOG_M("pss_f00.m","pss_f00",synchro_tmp,length,1,1);
bzero(synchroF_tmp, size);
/* get pss in the time domain by applying an inverse FFT */
dft((int16_t)get_dft(length),
synchro_tmp, /* complex input */
synchroF_tmp, /* complex output */
1); /* scaling factor */
if ((N_ID_2 == 0) && (length == 256)) {
LOG_M("pss_f_0.m","pss_f_0",synchroF_tmp,length,1,1);
}
/* check Pss */
k = length - (LENGTH_PSS_NR/2);
#define LIMIT_ERROR_FFT (10)
for (int i=0; i < LENGTH_PSS_NR; i++) {
if (abs(synchroF_tmp[2*k] - primary_synchro[2*i]) > LIMIT_ERROR_FFT) {
printf("Pss Error[%d] Compute %d Reference %d \n", k, synchroF_tmp[2*k], primary_synchro[2*i]);
}
if (abs(synchroF_tmp[2*k+1] - primary_synchro[2*i+1]) > LIMIT_ERROR_FFT) {
printf("Pss Error[%d] Compute %d Reference %d\n", (2*k+1), synchroF_tmp[2*k+1], primary_synchro[2*i+1]);
}
k++;
if (k >= length) {
k-=length;
}
}
}
#endif
}
/*******************************************************************
*
* NAME : init_context_pss_nr
*
* PARAMETERS : structure NR_DL_FRAME_PARMS give frame parameters
*
* RETURN : generate binary pss sequences (this is a m-sequence)
*
* DESCRIPTION : 3GPP TS 38.211 7.4.2.2 Primary synchronisation signal
* Sequence generation
*
*********************************************************************/
void init_context_pss_nr(NR_DL_FRAME_PARMS *frame_parms_ue)
{
int ofdm_symbol_size = frame_parms_ue->ofdm_symbol_size;
int sizePss = LENGTH_PSS_NR * IQ_SIZE; /* complex value i & q signed 16 bits */
int size = ofdm_symbol_size * IQ_SIZE; /* i and q samples signed 16 bits */
int16_t *p = NULL;
AssertFatal(ofdm_symbol_size > 127, "illegal ofdm_symbol_size %d\n",ofdm_symbol_size);
for (int i = 0; i < NUMBER_PSS_SEQUENCE; i++) {
p = malloc16(sizePss); /* pss in complex with alternatively i then q */
if (p != NULL) {
primary_synchro_nr[i] = p;
bzero( primary_synchro_nr[i], sizePss);
}
else {
LOG_E(PHY,"Fatal memory allocation problem \n");
assert(0);
}
p = malloc(LENGTH_PSS_NR*2);
if (p != NULL) {
primary_synchro_nr2[i] = p;
bzero( primary_synchro_nr2[i],LENGTH_PSS_NR*2);
}
p = malloc16(size);
if (p != NULL) {
primary_synchro_time_nr[i] = p;
bzero( primary_synchro_time_nr[i], size);
}
else {
LOG_E(PHY,"Fatal memory allocation problem \n");
assert(0);
}
generate_pss_nr(frame_parms_ue,i);
}
}
/*******************************************************************
*
* NAME : free_context_pss_nr
*
* PARAMETERS : none
*
* RETURN : none
*
* DESCRIPTION : free context related to pss
*
*********************************************************************/
void free_context_pss_nr(void)
{
for (int i = 0; i < NUMBER_PSS_SEQUENCE; i++) {
free_and_zero(primary_synchro_nr[i]);
free_and_zero(primary_synchro_nr2[i]);
free_and_zero(primary_synchro_time_nr[i]);
}
}
/*******************************************************************
*
* NAME : init_context_synchro_nr
*
* PARAMETERS : none
*
* RETURN : generate context for pss and sss
*
* DESCRIPTION : initialise contexts and buffers for synchronisation
*
*********************************************************************/
void init_context_synchro_nr(NR_DL_FRAME_PARMS *frame_parms_ue)
{
#ifndef STATIC_SYNC_BUFFER
/* initialise global buffers for synchronisation */
synchroF_tmp = malloc16(SYNCF_TMP_SIZE);
if (synchroF_tmp == NULL) {
LOG_E(PHY,"Fatal memory allocation problem \n");
assert(0);
}
synchro_tmp = malloc16(SYNC_TMP_SIZE);
if (synchro_tmp == NULL) {
LOG_E(PHY,"Fatal memory allocation problem \n");
assert(0);
}
#endif
init_context_pss_nr(frame_parms_ue);
init_context_sss_nr(AMP);
}
/*******************************************************************
*
* NAME : free_context_synchro_nr
*
* PARAMETERS : none
*
* RETURN : free context for pss and sss
*
* DESCRIPTION : deallocate memory of synchronisation
*
*********************************************************************/
void free_context_synchro_nr(void)
{
#ifndef STATIC_SYNC_BUFFER
if (synchroF_tmp != NULL) {
free(synchroF_tmp);
synchroF_tmp = NULL;
}
else {
LOG_E(PHY,"Fatal memory deallocation problem \n");
assert(0);
}
if (synchro_tmp != NULL) {
free(synchro_tmp);
synchro_tmp = NULL;
}
else {
LOG_E(PHY,"Fatal memory deallocation problem \n");
assert(0);
}
#endif
free_context_pss_nr();
}
/*******************************************************************
*
* NAME : set_frame_context_pss_nr
*
* PARAMETERS : configuration for UE with new FFT size
*
* RETURN : 0 if OK else error
*
* DESCRIPTION : initialisation of UE contexts
*
*********************************************************************/
void set_frame_context_pss_nr(NR_DL_FRAME_PARMS *frame_parms_ue, int rate_change)
{
/* set new value according to rate_change */
frame_parms_ue->ofdm_symbol_size = (frame_parms_ue->ofdm_symbol_size / rate_change);
frame_parms_ue->samples_per_subframe = (frame_parms_ue->samples_per_subframe / rate_change);
free_context_pss_nr();
/* pss reference have to be rebuild with new parameters ie ofdm symbol size */
init_context_synchro_nr(frame_parms_ue);
#ifdef SYNCHRO_DECIMAT
set_pss_nr(frame_parms_ue->ofdm_symbol_size);
#endif
}
/*******************************************************************
*
* NAME : restore_frame_context_pss_nr
*
* PARAMETERS : configuration for UE and eNB with new FFT size
*
* RETURN : 0 if OK else error
*
* DESCRIPTION : initialisation of UE and eNode contexts
*
*********************************************************************/
void restore_frame_context_pss_nr(NR_DL_FRAME_PARMS *frame_parms_ue, int rate_change)
{
frame_parms_ue->ofdm_symbol_size = frame_parms_ue->ofdm_symbol_size * rate_change;
frame_parms_ue->samples_per_subframe = frame_parms_ue->samples_per_subframe * rate_change;
free_context_pss_nr();
/* pss reference have to be rebuild with new parameters ie ofdm symbol size */
init_context_synchro_nr(frame_parms_ue);
#ifdef SYNCHRO_DECIMAT
set_pss_nr(frame_parms_ue->ofdm_symbol_size);
#endif
}
/********************************************************************
*
* NAME : decimation_synchro_nr
*
* INPUT : UE context
* for first and second pss sequence
* - position of pss in the received UE buffer
* - number of pss sequence
*
* RETURN : 0 if OK else error
*
* DESCRIPTION : detect pss sequences in the received UE buffer
*
********************************************************************/
void decimation_synchro_nr(PHY_VARS_NR_UE *PHY_vars_UE, int rate_change, int **rxdata)
{
NR_DL_FRAME_PARMS *frame_parms = &(PHY_vars_UE->frame_parms);
int samples_for_frame = 2*frame_parms->samples_per_frame;
#if TEST_SYNCHRO_TIMING_PSS
opp_enabled = 1;
start_meas(&generic_time[TIME_RATE_CHANGE]);
#endif
/* build with cic filter does not work properly. Performances are significantly deteriorated */
#ifdef CIC_DECIMATOR
cic_decimator((int16_t *)&(PHY_vars_UE->common_vars.rxdata[0][0]), (int16_t *)&(rxdata[0][0]),
samples_for_frame, rate_change, CIC_FILTER_STAGE_NUMBER, 0, FIR_RATE_CHANGE);
#else
fir_decimator((int16_t *)&(PHY_vars_UE->common_vars.rxdata[0][0]), (int16_t *)&(rxdata[0][0]),
samples_for_frame, rate_change, 0);
#endif
set_frame_context_pss_nr(frame_parms, rate_change);
#if TEST_SYNCHRO_TIMING_PSS
stop_meas(&generic_time[TIME_RATE_CHANGE]);
printf("Rate change execution duration %5.2f \n", generic_time[TIME_RATE_CHANGE].p_time/(cpuf*1000.0));
#endif
}
/*******************************************************************
*
* NAME : pss_synchro_nr
*
* PARAMETERS : int rate_change
*
* RETURN : position of detected pss
*
* DESCRIPTION : pss search can be done with sampling decimation.*
*
*********************************************************************/
int pss_synchro_nr(PHY_VARS_NR_UE *PHY_vars_UE, int is, int rate_change)
{
NR_DL_FRAME_PARMS *frame_parms = &(PHY_vars_UE->frame_parms);
int synchro_position;
int **rxdata = NULL;
int fo_flag = PHY_vars_UE->UE_fo_compensation; // flag to enable freq offset estimation and compensation
VCD_SIGNAL_DUMPER_DUMP_FUNCTION_BY_NAME(VCD_SIGNAL_DUMPER_FUNCTIONS_PSS_SYNCHRO_NR, VCD_FUNCTION_IN);
#ifdef DBG_PSS_NR
LOG_M("rxdata0_rand.m","rxd0_rand", &PHY_vars_UE->common_vars.rxdata[0][0], frame_parms->samples_per_frame, 1, 1);
#endif
if (rate_change != 1) {
rxdata = (int32_t**)malloc16(frame_parms->nb_antennas_rx*sizeof(int32_t*));
for (int aa=0; aa < frame_parms->nb_antennas_rx; aa++) {
rxdata[aa] = (int32_t*) malloc16_clear( (frame_parms->samples_per_frame+8192)*sizeof(int32_t));
}
#ifdef SYNCHRO_DECIMAT
decimation_synchro_nr(PHY_vars_UE, rate_change, rxdata);
#endif
}
else {
rxdata = PHY_vars_UE->common_vars.rxdata;
}
#ifdef DBG_PSS_NR
LOG_M("rxdata0_des.m","rxd0_des", &rxdata[0][0], frame_parms->samples_per_frame,1,1);
#endif
#if TEST_SYNCHRO_TIMING_PSS
opp_enabled = 1;
start_meas(&generic_time[TIME_PSS]);
#endif
VCD_SIGNAL_DUMPER_DUMP_FUNCTION_BY_NAME(VCD_SIGNAL_DUMPER_FUNCTIONS_PSS_SEARCH_TIME_NR, VCD_FUNCTION_IN);
synchro_position = pss_search_time_nr(rxdata,
frame_parms,
fo_flag,
is,
(int *)&PHY_vars_UE->common_vars.eNb_id,
(int *)&PHY_vars_UE->common_vars.freq_offset);
VCD_SIGNAL_DUMPER_DUMP_FUNCTION_BY_NAME(VCD_SIGNAL_DUMPER_FUNCTIONS_PSS_SEARCH_TIME_NR, VCD_FUNCTION_OUT);
#if TEST_SYNCHRO_TIMING_PSS
stop_meas(&generic_time[TIME_PSS]);
int duration_ms = generic_time[TIME_PSS].p_time/(cpuf*1000.0);
#ifndef NR_UNIT_TEST
printf("PSS execution duration %4d microseconds \n", duration_ms);
#endif
#endif
#ifdef SYNCHRO_DECIMAT
if (rate_change != 1) {
if (rxdata[0] != NULL) {
for (int aa=0;aa<frame_parms->nb_antennas_rx;aa++) {
free(rxdata[aa]);
}
free(rxdata);
}
restore_frame_context_pss_nr(frame_parms, rate_change);
}
#endif
VCD_SIGNAL_DUMPER_DUMP_FUNCTION_BY_NAME(VCD_SIGNAL_DUMPER_FUNCTIONS_PSS_SYNCHRO_NR, VCD_FUNCTION_OUT);
return synchro_position;
}
/*******************************************************************
*
* NAME : pss_search_time_nr
*
* PARAMETERS : received buffer
* frame parameters
*
* RETURN : position of detected pss
*
* DESCRIPTION : Synchronisation on pss sequence is based on a time domain correlation between received samples and pss sequence
* A maximum likelihood detector finds the timing offset (position) that corresponds to the maximum correlation
* Length of received buffer should be a minimum of 2 frames (see TS 38.213 4.1 Cell search)
* Search pss in the received buffer is done each 4 samples which ensures a memory alignment to 128 bits (32 bits x 4).
* This is required by SIMD (single instruction Multiple Data) Extensions of Intel processors
* Correlation computation is based on a a dot product which is realized thank to SIMS extensions
*
* (x frames)
* <--------------------------------------------------------------------------->
*
*
* -----------------------------------------------------------------------------
* | Received UE data buffer |
* ----------------------------------------------------------------------------
* -------------
* <--------->| pss |
* position -------------
* ^
* |
* peak position
* given by maximum of correlation result
* position matches beginning of first ofdm symbol of pss sequence
*
* Remark: memory position should be aligned on a multiple of 4 due to I & Q samples of int16
* An OFDM symbol is composed of x number of received samples depending of Rf front end sample rate.
*
* I & Q storage in memory
*
* First samples Second samples
* ------------------------- ------------------------- ...
* | I1 | Q1 | I2 | Q2 |
* --------------------------------------------------- ...
* ^ 16 bits 16 bits ^
* | |
* --------------------------------------------------- ...
* | sample 1 | sample 2 |
* ---------------------------------------------------- ...
* ^
*
*********************************************************************/
#define DOT_PRODUCT_SCALING_SHIFT (17)
int pss_search_time_nr(int **rxdata, ///rx data in time domain
NR_DL_FRAME_PARMS *frame_parms,
int fo_flag,
int is,
int *eNB_id,
int *f_off)
{
unsigned int n, ar, peak_position, pss_source;
int64_t peak_value;
int64_t result;
int64_t avg[NUMBER_PSS_SEQUENCE]={0};
double ffo_est=0;
// performing the correlation on a frame length plus one symbol for the first of the two frame
// to take into account the possibility of PSS in between the two frames
unsigned int length;
if (is==0)
length = frame_parms->samples_per_frame + (2*frame_parms->ofdm_symbol_size);
else
length = frame_parms->samples_per_frame;
AssertFatal(length>0,"illegal length %d\n",length);
peak_value = 0;
peak_position = 0;
pss_source = 0;
int maxval=0;
for (int i=0;i<2*(frame_parms->ofdm_symbol_size);i++) {
maxval = max(maxval,primary_synchro_time_nr[0][i]);
maxval = max(maxval,-primary_synchro_time_nr[0][i]);
maxval = max(maxval,primary_synchro_time_nr[1][i]);
maxval = max(maxval,-primary_synchro_time_nr[1][i]);
maxval = max(maxval,primary_synchro_time_nr[2][i]);
maxval = max(maxval,-primary_synchro_time_nr[2][i]);
}
int shift = log2_approx(maxval);//*(frame_parms->ofdm_symbol_size+frame_parms->nb_prefix_samples)*2);
/* Search pss in the received buffer each 4 samples which ensures a memory alignment on 128 bits (32 bits x 4 ) */
/* This is required by SIMD (single instruction Multiple Data) Extensions of Intel processors. */
/* Correlation computation is based on a a dot product which is realized thank to SIMS extensions */
for (int pss_index = 0; pss_index < NUMBER_PSS_SEQUENCE; pss_index++) {
for (n=0; n < length; n+=4) { //
int64_t pss_corr_ue=0;
/* calculate dot product of primary_synchro_time_nr and rxdata[ar][n]
* (ar=0..nb_ant_rx) and store the sum in temp[n]; */
for (ar=0; ar<frame_parms->nb_antennas_rx; ar++) {
/* perform correlation of rx data and pss sequence ie it is a dot product */
result = dot_product64((short*)primary_synchro_time_nr[pss_index],
(short*)&(rxdata[ar][n+is*frame_parms->samples_per_frame]),
frame_parms->ofdm_symbol_size,
shift);
pss_corr_ue += squaredMod(*(c32_t*)&result);
//((short*)pss_corr_ue[pss_index])[2*n] += ((short*) &result)[0]; /* real part */
//((short*)pss_corr_ue[pss_index])[2*n+1] += ((short*) &result)[1]; /* imaginary part */
//((short*)&synchro_out)[0] += ((int*) &result)[0]; /* real part */
//((short*)&synchro_out)[1] += ((int*) &result)[1]; /* imaginary part */
}
/* calculate the absolute value of sync_corr[n] */
avg[pss_index]+=pss_corr_ue;
if (pss_corr_ue > peak_value) {
peak_value = pss_corr_ue;
peak_position = n;
pss_source = pss_index;
#ifdef DEBUG_PSS_NR
printf("pss_index %d: n %6u peak_value %15llu\n", pss_index, n, (unsigned long long)pss_corr_ue[n]);
#endif
}
}
}
if (fo_flag){
// fractional frequency offset computation according to Cross-correlation Synchronization Algorithm Using PSS
// Shoujun Huang, Yongtao Su, Ying He and Shan Tang, "Joint time and frequency offset estimation in LTE downlink," 7th International Conference on Communications and Networking in China, 2012.
int64_t result1,result2;
// Computing cross-correlation at peak on half the symbol size for first half of data
result1 = dot_product64((short*)primary_synchro_time_nr[pss_source],
(short*) &(rxdata[0][peak_position+is*frame_parms->samples_per_frame]),
frame_parms->ofdm_symbol_size>>1,
shift);
// Computing cross-correlation at peak on half the symbol size for data shifted by half symbol size
// as it is real and complex it is necessary to shift by a value equal to symbol size to obtain such shift
result2 = dot_product64((short*)primary_synchro_time_nr[pss_source]+(frame_parms->ofdm_symbol_size),
(short*) &(rxdata[0][peak_position+is*frame_parms->samples_per_frame])+frame_parms->ofdm_symbol_size,
frame_parms->ofdm_symbol_size>>1,
shift);
int64_t re1,re2,im1,im2;
re1=((int*) &result1)[0];
re2=((int*) &result2)[0];
im1=((int*) &result1)[1];
im2=((int*) &result2)[1];
// estimation of fractional frequency offset: angle[(result1)'*(result2)]/pi
ffo_est=atan2(re1*im2-re2*im1,re1*re2+im1*im2)/M_PI;
#ifdef DBG_PSS_NR
printf("ffo %lf\n",ffo_est);
#endif
}
// computing absolute value of frequency offset
*f_off = ffo_est*frame_parms->subcarrier_spacing;
for (int pss_index = 0; pss_index < NUMBER_PSS_SEQUENCE; pss_index++)
avg[pss_index]/=(length/4);
*eNB_id = pss_source;
LOG_I(PHY,"[UE] nr_synchro_time: Sync source = %d, Peak found at pos %d, val = %llu (%d dB) avg %d dB, ffo %lf\n", pss_source, peak_position, (unsigned long long)peak_value, dB_fixed64(peak_value),dB_fixed64(avg[pss_source]),ffo_est);
if (peak_value < 5*avg[pss_source])
return(-1);
#ifdef DBG_PSS_NR
static int debug_cnt = 0;
if (debug_cnt == 0) {
if (is)
LOG_M("rxdata1.m","rxd0",rxdata[frame_parms->samples_per_frame],length,1,1);
else
LOG_M("rxdata0.m","rxd0",rxdata[0],length,1,1);
} else {
debug_cnt++;
}
#endif
return(peak_position);
}
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