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srsLTE
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Added filtering function to PSS

This commit is contained in:
Ismael Gomez 2017-11-29 11:58:18 +01:00
parent 2fd2f15157
commit 2772471e41
2 changed files with 118 additions and 74 deletions
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16
lib/include/srslte/phy/sync/pss.h
View File

@ -71,8 +71,6 @@
/* Low-level API */
typedef struct SRSLTE_API {
srslte_dft_plan_t dftp_input;
#ifdef CONVOLUTION_FFT
srslte_conv_fft_cc_t conv_fft;
srslte_filt_cc_t filter;
@ -97,6 +95,13 @@ typedef struct SRSLTE_API {
float ema_alpha;
float *conv_output_avg;
float peak_value;
bool filter_pss_enable;
srslte_dft_plan_t dftp_input;
srslte_dft_plan_t idftp_input;
cf_t tmp_fft[SRSLTE_SYMBOL_SZ_MAX];
cf_t tmp_fft2[SRSLTE_SYMBOL_SZ_MAX];
}srslte_pss_synch_t;
typedef enum { PSS_TX, PSS_RX } pss_direction_t;
@ -128,6 +133,13 @@ SRSLTE_API void srslte_pss_synch_free(srslte_pss_synch_t *q);
SRSLTE_API void srslte_pss_synch_reset(srslte_pss_synch_t *q);
SRSLTE_API void srslte_pss_synch_filter_enable(srslte_pss_synch_t *q,
bool enable);
SRSLTE_API void srslte_pss_synch_filter(srslte_pss_synch_t *q,
cf_t *input,
cf_t *output);
SRSLTE_API int srslte_pss_generate(cf_t *signal,
uint32_t N_id_2);

52
lib/src/phy/sync/pss.c
View File

@ -30,12 +30,8 @@
#include <stdlib.h>
#include <complex.h>
#include <math.h>
#include <srslte/phy/sync/pss.h>
#include "srslte/phy/sync/pss.h"
#include "srslte/phy/dft/dft.h"
#include "srslte/phy/utils/vector.h"
#include "srslte/phy/utils/convolution.h"
#include "srslte/phy/utils/debug.h"
@ -123,6 +119,8 @@ int srslte_pss_synch_init_fft_offset_decim(srslte_pss_synch_t *q,
buffer_size = fft_size + frame_size + 1;
q->filter_pss_enable = true;
if(q->decimate > 1) {
int filter_order = 3;
srslte_filt_decim_cc_init(&q->filter,q->decimate,filter_order);
@ -137,7 +135,17 @@ int srslte_pss_synch_init_fft_offset_decim(srslte_pss_synch_t *q,
}
srslte_dft_plan_set_mirror(&q->dftp_input, true);
srslte_dft_plan_set_dc(&q->dftp_input, true);
srslte_dft_plan_set_norm(&q->dftp_input, true);
srslte_dft_plan_set_norm(&q->dftp_input, false);
if (srslte_dft_plan(&q->idftp_input, fft_size, SRSLTE_DFT_BACKWARD, SRSLTE_DFT_COMPLEX)) {
fprintf(stderr, "Error creating DFT plan \n");
goto clean_and_exit;
}
srslte_dft_plan_set_mirror(&q->idftp_input, true);
srslte_dft_plan_set_dc(&q->idftp_input, true);
srslte_dft_plan_set_norm(&q->idftp_input, true);
bzero(q->tmp_fft2, sizeof(cf_t)*SRSLTE_SYMBOL_SZ_MAX);
q->tmp_input = srslte_vec_malloc((buffer_size + frame_size*(q->decimate - 1)) * sizeof(cf_t));
if (!q->tmp_input) {
@ -248,6 +256,13 @@ int srslte_pss_synch_resize(srslte_pss_synch_t *q, uint32_t frame_size, uint32_t
return SRSLTE_ERROR;
}
if (srslte_dft_replan(&q->idftp_input, fft_size)) {
fprintf(stderr, "Error creating DFT plan \n");
return SRSLTE_ERROR;
}
bzero(q->tmp_fft2, sizeof(cf_t)*SRSLTE_SYMBOL_SZ_MAX);
bzero(&q->tmp_input[q->frame_size], q->fft_size * sizeof(cf_t));
bzero(q->conv_output, sizeof(cf_t) * buffer_size);
bzero(q->conv_output_avg, sizeof(float) * buffer_size);
@ -314,6 +329,7 @@ void srslte_pss_synch_free(srslte_pss_synch_t *q) {
}
srslte_dft_plan_free(&q->dftp_input);
srslte_dft_plan_free(&q->idftp_input);
if(q->decimate > 1)
{
@ -560,19 +576,35 @@ int srslte_pss_synch_chest(srslte_pss_synch_t *q, cf_t *input, cf_t ce[SRSLTE_PS
return ret;
}
// Frequency-domain filtering of the central 64 sub-carriers
void srslte_pss_synch_filter(srslte_pss_synch_t *q, cf_t *input, cf_t *output)
{
srslte_dft_run_c(&q->dftp_input, input, q->tmp_fft);
memcpy(&q->tmp_fft2[q->fft_size/2-SRSLTE_PSS_LEN/2],
&q->tmp_fft[q->fft_size/2-SRSLTE_PSS_LEN/2],
sizeof(cf_t)*SRSLTE_PSS_LEN);
srslte_dft_run_c(&q->idftp_input, q->tmp_fft2, output);
}
/* Returns the CFO estimation given a PSS received sequence
*
* Source: An Efficient CFO Estimation Algorithm for the Downlink of 3GPP-LTE
* Feng Wang and Yu Zhu
*/
float srslte_pss_synch_cfo_compute(srslte_pss_synch_t* q, cf_t *pss_recv) {
cf_t y0, y1, yr;
cf_t y0, y1;
y0 = srslte_vec_dot_prod_ccc(q->pss_signal_time[q->N_id_2], pss_recv, q->fft_size/2);
y1 = srslte_vec_dot_prod_ccc(&q->pss_signal_time[q->N_id_2][q->fft_size/2], &pss_recv[q->fft_size/2], q->fft_size/2);
cf_t *pss_ptr = pss_recv;
yr = conjf(y0) * y1;
if (q->filter_pss_enable) {
srslte_pss_synch_filter(q, pss_recv, q->tmp_fft);
pss_ptr = q->tmp_fft;
}
return atan2f(__imag__ yr, __real__ yr) / M_PI;
y0 = srslte_vec_dot_prod_ccc(q->pss_signal_time[q->N_id_2], pss_ptr, q->fft_size/2);
y1 = srslte_vec_dot_prod_ccc(&q->pss_signal_time[q->N_id_2][q->fft_size/2], &pss_ptr[q->fft_size/2], q->fft_size/2);
return carg(conjf(y0) * y1)/M_PI;
}