CFO correction using LUT

examples/mib_scan_usrp.c

@@ -65,6 +65,7 @@ pbch_t pbch;
 lte_fft_t fft;
 chest_t chest;
 sync_t sfind, strack;
+cfo_t cfocorr;
 
 float *cfo_v;
 int *idx_v, *idx_valid, *t;
@@ -182,6 +183,10 @@ int base_init(int frame_length) {
 		fprintf(stderr, "Error initializing FFT\n");
 		return -1;
 	}
+	if (cfo_init(&cfocorr, FLEN)) {
+		fprintf(stderr, "Error initiating CFO\n");
+		return -1;
+	}
 
 	idx_v = malloc(nof_frames_track * sizeof(int));
 	if (!idx_v) {
@@ -229,10 +234,12 @@ void base_free() {
 #ifndef DISABLE_UHD
 	cuhd_close(&uhd);
 #endif
+
 	sync_free(&sfind);
 	sync_free(&strack);
 	lte_fft_free(&fft);
 	chest_free(&chest);
+	cfo_free(&cfocorr);
 
 	free(input_buffer);
 	free(fft_buffer);
@@ -506,7 +513,7 @@ int main(int argc, char **argv) {
 
 				// Correct CFO
 				INFO("Correcting CFO=%.4f\n", cfo[freq]);
-				nco_cexp_f_direct(&input_buffer[FLEN], (-cfo[freq])/128, FLEN);
+				cfo_correct(&cfocorr, &input_buffer[FLEN], (-cfo[freq])/128);
 
 				if (nslot == 0) {
 					if (mib_decoder_run(&input_buffer[FLEN+find_idx], &mib)) {

examples/mib_test.c

@@ -49,6 +49,7 @@ pbch_t pbch;
 lte_fft_t fft;
 chest_t chest;
 sync_t synch;
+cfo_t cfocorr;
 
 void usage(char *prog) {
 	printf("Usage: %s [onlt] -i input_file\n", prog);
@@ -122,6 +123,11 @@ int base_init() {
 		}
 	}
 
+	if (cfo_init(&cfocorr, FLEN)) {
+		fprintf(stderr, "Error initiating CFO\n");
+		return -1;
+	}
+
 	if (chest_init(&chest, LINEAR, CPNORM, 6, NOF_PORTS)) {
 		fprintf(stderr, "Error initializing equalizer\n");
 		return -1;
@@ -265,8 +271,10 @@ int main(int argc, char **argv) {
 			fprintf(stderr, "Error reading %d samples\n", FLEN);
 			break;
 		}
+
 		INFO("Correcting CFO=%.4f\n", cfo);
-		nco_cexp_f_direct(input_buffer, -cfo/128, FLEN);
+		cfo_correct(&cfocorr, input_buffer, -cfo/128);
+
 		switch(state) {
 		case SYNC:
 			INFO("State Sync, Slot idx=%d\n", frame_cnt);

examples/mib_track.c

@@ -64,6 +64,7 @@ pbch_t pbch;
 lte_fft_t fft;
 chest_t chest;
 sync_t sfind, strack;
+cfo_t cfocorr;
 
 plot_real_t poutfft;
 plot_complex_t pce;
@@ -200,6 +201,11 @@ int base_init(int frame_length) {
 		return -1;
 	}
 
+	if (cfo_init(&cfocorr, FLEN)) {
+		fprintf(stderr, "Error initiating CFO\n");
+		return -1;
+	}
+
 	if (lte_fft_init(&fft, CPNORM, 6)) {
 		fprintf(stderr, "Error initializing FFT\n");
 		return -1;
@@ -223,6 +229,7 @@ void base_free() {
 	sync_free(&strack);
 	lte_fft_free(&fft);
 	chest_free(&chest);
+	cfo_free(&cfocorr);
 
 	free(input_buffer);
 	free(fft_buffer);
@@ -385,7 +392,8 @@ int main(int argc, char **argv) {
 
 			// Correct CFO
 			INFO("Correcting CFO=%.4f\n", cfo);
-			nco_cexp_f_direct(input_buffer, (-cfo)/128, FLEN);
+
+			cfo_correct(&cfocorr, input_buffer, -cfo/128);
 
 			if (nslot == 0) {
 				INFO("Finding MIB at idx %d\n", find_idx);

examples/synch_test.c

@@ -106,6 +106,7 @@ int main(int argc, char **argv) {
 	filesink_t fsink;
 	pss_synch_t pss[3]; // One for each N_id_2
 	sss_synch_t sss[3]; // One for each N_id_2
+	cfo_t cfocorr;
 	int peak_pos[3];
 	float *cfo;
 	float peak_value[3];
@@ -155,6 +156,11 @@ int main(int argc, char **argv) {
 		exit(-1);
 	}
 
+	if (cfo_init(&cfocorr, frame_length)) {
+		fprintf(stderr, "Error initiating CFO\n");
+		return -1;
+	}
+
 	/* We have 2 options here:
 	 * a) We create 3 pss objects, each initialized with a different N_id_2
 	 * b) We create 1 pss object which scans for each N_id_2 one after another.
@@ -192,7 +198,7 @@ int main(int argc, char **argv) {
 
 		gettimeofday(&tdata[1], NULL);
 		if (force_cfo != CFO_AUTO) {
-			nco_cexp_f_direct(input, -force_cfo/128, frame_length);
+			cfo_correct(&cfocorr, input, -force_cfo/128);
 		}
 
 		if (force_N_id_2 != -1) {

lte/include/lte.h

@@ -38,7 +38,7 @@
 #include "lte/utils/dft.h"
 #include "lte/utils/matrix.h"
 #include "lte/utils/mux.h"
-#include "lte/utils/nco.h"
+#include "lte/utils/cexptab.h"
 #include "lte/utils/pack.h"
 #include "lte/utils/vector.h"
 
@@ -83,6 +83,6 @@
 #include "lte/sync/sfo.h"
 #include "lte/sync/sss.h"
 #include "lte/sync/sync.h"
-
+#include "lte/sync/cfo.h"
 
 #endif

lte/include/lte/sync/cfo.h

@@ -0,0 +1,55 @@
+/**
+ *
+ * \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/.
+ *
+ */
+
+
+#ifndef _cfo_
+#define _cfo_
+
+#include <complex.h>
+
+typedef _Complex float cf_t;
+
+/** If the frequency is changed more than the tolerance, a new table is generated */
+#define CFO_TOLERANCE 0.00001
+
+#define CFO_CEXPTAB_SIZE 4096
+
+typedef struct {
+	float last_freq;
+	float tol;
+	int nsamples;
+	cexptab_t tab;
+	cf_t *cur_cexp;
+}cfo_t;
+
+int cfo_init(cfo_t *h, int nsamples);
+void cfo_free(cfo_t *h);
+
+void cfo_set_tol(cfo_t *h, float tol);
+void cfo_correct(cfo_t *h, cf_t *x, float freq);
+
+#endif

lte/include/lte/utils/cexptab.h

@@ -26,28 +26,22 @@
  */
 
 
-#ifndef NCO_
-#define NCO_
+#ifndef _cexptab_
+#define _cexptab_
 
 #include <complex.h>
 
+typedef _Complex float cf_t;
+
 typedef struct {
 	int size;
-	float *cost;
-	float *sint;
-}nco_t;
+	cf_t *tab;
+}cexptab_t;
 
-void nco_init(nco_t *nco, int size);
-void nco_destroy(nco_t *nco);
+int cexptab_init(cexptab_t *nco, int size);
+void cexptab_free(cexptab_t *nco);
 
-float nco_sin(nco_t *nco, float phase);
-float nco_cos(nco_t *nco, float phase);
-void nco_sincos(nco_t *nco, float phase, float *sin, float *cos);
-_Complex float nco_cexp(nco_t *nco, float arg);
-
-void nco_sin_f(nco_t *nco, float *x, float freq, int len);
-void nco_cos_f(nco_t *nco, float *x, float freq, int len);
-void nco_cexp_f(nco_t *nco, _Complex float *x, float freq, int len);
-void nco_cexp_f_direct(_Complex float *x, float freq, int len);
+void cexptab_gen(cexptab_t *nco, cf_t *x, float freq, int len);
+void cexptab_gen_direct(cf_t *x, float freq, int len);
 
 #endif

lte/lib/sync/src/cfo.c

@@ -0,0 +1,80 @@
+/**
+ *
+ * \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 <strings.h>
+#include <stdlib.h>
+#include <math.h>
+
+#include "lte/utils/cexptab.h"
+#include "lte/sync/cfo.h"
+#include "lte/utils/vector.h"
+#include "lte/utils/debug.h"
+
+int cfo_init(cfo_t *h, int nsamples) {
+	int ret = -1;
+	bzero(h, sizeof(cfo_t));
+
+	if (cexptab_init(&h->tab, CFO_CEXPTAB_SIZE)) {
+		goto clean;
+	}
+	h->cur_cexp = malloc(sizeof(cf_t) * nsamples);
+	if (!h->cur_cexp) {
+		goto clean;
+	}
+	h->tol = CFO_TOLERANCE;
+	h->last_freq = 0;
+	h->nsamples = nsamples;
+	cexptab_gen(&h->tab, h->cur_cexp, h->last_freq, h->nsamples);
+
+	ret = 0;
+clean:
+	if (ret == -1) {
+		cfo_free(h);
+	}
+	return ret;
+}
+
+void cfo_free(cfo_t *h) {
+	cexptab_free(&h->tab);
+	if (h->cur_cexp) {
+		free(h->cur_cexp);
+	}
+	bzero(h, sizeof(cf_t));
+}
+
+void cfo_set_tol(cfo_t *h, float tol) {
+	h->tol = tol;
+}
+
+void cfo_correct(cfo_t *h, cf_t *x, float freq) {
+	if (fabs(h->last_freq - freq) > h->tol) {
+		h->last_freq = freq;
+		cexptab_gen(&h->tab, h->cur_cexp, h->last_freq, h->nsamples);
+		INFO("CFO generating new table for frequency %.4f\n", freq);
+	}
+	vec_prod_ccc(h->cur_cexp, x, x, h->nsamples);
+}

lte/lib/utils/src/cexptab.c

@@ -0,0 +1,80 @@
+/**
+ *
+ * \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 <stdlib.h>
+#include <math.h>
+#include <string.h>
+#include <assert.h>
+#include <complex.h>
+
+#include "lte/utils/cexptab.h"
+
+int cexptab_init(cexptab_t *h, int size) {
+	int i;
+
+	h->size = size;
+	h->tab = malloc(sizeof(cf_t) * size);
+	if (h->tab) {
+		for (i = 0; i < size; i++) {
+			h->tab[i] = cexpf(_Complex_I * 2 * M_PI * (float) i / size);
+		}
+		return 0;
+	} else {
+		return -1;
+	}
+}
+
+void cexptab_free(cexptab_t *h) {
+	if (h->tab) {
+		free(h->tab);
+	}
+	bzero(h, sizeof(cexptab_t));
+}
+
+void cexptab_gen(cexptab_t *h, cf_t *x, float freq, int len) {
+	int i;
+	unsigned int idx;
+	float phase_inc = freq * h->size;
+	float phase=0;
+
+	for (i = 0; i < len; i++) {
+		idx = (unsigned int) phase;
+		x[i] = h->tab[idx];
+		phase += phase_inc;
+		if (phase >= (float) h->size) {
+			phase -= (float) h->size;
+		}
+	}
+}
+
+void cexptab_gen_direct(cf_t *x, float freq, int len) {
+	int i;
+	for (i = 0; i < len; i++) {
+		x[i] = cexpf(_Complex_I * 2 * M_PI * freq * i);
+	}
+}
+

lte/lib/utils/src/nco.c

@@ -1,131 +0,0 @@
-/**
- *
- * \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 <stdlib.h>
-#include <math.h>
-#include <string.h>
-#include <assert.h>
-#include <complex.h>
-
-#include "lte/utils/nco.h"
-
-void nco_init(nco_t *nco, int size) {
-	int i;
-
-	nco->size=size;
-	nco->cost=malloc(size*sizeof(float));
-	nco->sint=malloc(size*sizeof(float));
-	assert(nco->cost && nco->sint);
-
-	for (i=0;i<size;i++) {
-		nco->cost[i] = cosf(2*M_PI*i/size);
-		nco->sint[i] = sinf(2*M_PI*i/size);
-	}
-}
-
-void nco_destroy(nco_t *nco) {
-	if (nco->cost) {
-		free(nco->cost);
-	}
-	if (nco->sint) {
-		free(nco->sint);
-	}
-	nco->size=0;
-	bzero(nco, sizeof(nco_t));
-}
-
-unsigned int nco_idx(float phase, int size) {
-	while(phase>=2*M_PI) {
-		phase-=2*M_PI;
-	}
-	unsigned int idx = (unsigned int) (phase*size/(2*M_PI));
-	return idx;
-}
-
-inline float nco_sin(nco_t *nco, float phase) {
-	return nco->sint[nco_idx(phase,nco->size)];
-}
-inline float nco_cos(nco_t *nco, float phase) {
-	return nco->cost[nco_idx(phase,nco->size)];
-}
-inline void nco_sincos(nco_t *nco, float phase, float *sin, float *cos) {
-	unsigned int idx = nco_idx(phase,nco->size);
-	*sin = nco->sint[idx];
-	*cos = nco->cost[idx];
-}
-
-inline _Complex float nco_cexp(nco_t *nco, float arg) {
-	float s,c;
-	nco_sincos(nco,arg,&s,&c);
-	return c+I*s;
-}
-
-void nco_sin_f(nco_t *nco, float *x, float freq, int len) {
-	int i;
-	unsigned int idx;
-
-	idx=0;
-	for (i=0;i<len;i++) {
-		idx=((unsigned int) (freq*i*nco->size/len))%nco->size;
-		x[i] = nco->sint[idx];
-	}
-}
-
-
-void nco_cos_f(nco_t *nco, float *x, float freq, int len) {
-	int i;
-	unsigned int idx;
-
-	idx=0;
-	for (i=0;i<len;i++) {
-		idx=((unsigned int) (freq*i*nco->size/len))%nco->size;
-		x[i] = nco->cost[idx];
-	}
-}
-
-
-void nco_cexp_f(nco_t *nco, _Complex float *x, float freq, int len) {
-	int i;
-	unsigned int idx;
-
-	idx=0;
-	for (i=0;i<len;i++) {
-		idx=((unsigned int) (freq*i*nco->size/len))%nco->size;
-		x[i] = nco->cost[idx] + I*nco->sint[idx];
-	}
-}
-
-void nco_cexp_f_direct(_Complex float *x, float freq, int len) {
-	int i;
-	for (i=0;i<len;i++) {
-		x[i] *= cexpf(_Complex_I * 2 * M_PI * freq * i);
-	}
-}
-