srsRAN/lib/ch_estimation/src/refsignal.c

/*
 * Copyright (c) 2013, Ismael Gomez-Miguelez <gomezi@tcd.ie>.
 * This file is part of OSLD-lib (http://https://github.com/ismagom/osld-lib)
 *
 * OSLD-lib 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.
 *
 * OSLD-lib 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.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with OSLD-lib.  If not, see <http://www.gnu.org/licenses/>.
 */

#include <math.h>
#include <string.h>
#include <strings.h>
#include <stdlib.h>

#include "lte/base.h"
#include "ch_estimation/refsignal.h"
#include "utils/vector.h"
#include "utils/debug.h"
#include "lte/sequence.h"

#define idx(x, y) (l*nof_refs_x_symbol+i)

int refsignal_v(int port_id, int ns, int symbol_id) {
	int v=-1;
	switch(port_id) {
	case 0:
		if (symbol_id == 0) {
			v=0;
		} else {
			v=3;
		}
		break;
	case 1:
		if (symbol_id == 0) {
			v=3;
		} else {
			v=0;
		}
		break;
	case 2:
		v=3*(ns%2);
		break;
	case 3:
		v=3+3*(ns%2);
		break;
	}
	return v;
}

int refsignal_k(int m, int v, int cell_id) {
	return 6*m+((v+(cell_id%6))%6);
}

/** Initializes refsignal_t object according to 3GPP 36.211 6.10.1
 *
 */
int refsignal_init_LTEDL(refsignal_t *q, int port_id, int nslot,
		int cell_id, lte_cp_t cp, int nof_prb) {

	unsigned int c_init;
	int ns, l, lp[2];
	int N_cp;
	int i;
	int ret = -1;
	sequence_t seq;
	int v;
	int mp;
	int nof_refs_x_symbol, nof_ref_symbols;

	bzero(q, sizeof(refsignal_t));
	bzero(&seq, sizeof(sequence_t));

	if (CP_ISNORM(cp)) {
		N_cp = 1;
	} else {
		N_cp = 0;
	}

	if (port_id < 0 || port_id > (MAX_PORTS - 1)) {
		fprintf(stderr, "Invalid port id %d\n", port_id);
		return -1;
	}

	if (port_id < 2) {
		nof_ref_symbols = 2;
		lp[0] = 0;
		lp[1] = CP_NSYMB(cp) - 3;
	} else {
		nof_ref_symbols = 1;
		lp[0] = 1;
	}
	nof_refs_x_symbol = 2 * nof_prb;

	q->nof_refs = nof_refs_x_symbol * nof_ref_symbols;
	q->nsymbols = nof_ref_symbols;
	q->symbols_ref = malloc(sizeof(int) * nof_ref_symbols);
	q->voffset = cell_id%6;
	if (!q->symbols_ref) {
		return -1;
	}

	memcpy(q->symbols_ref, lp, sizeof(int) * nof_ref_symbols);

	DEBUG("Initializing %d CRS for LTE DL slot=%d, %d RE in %d symbols\n",
			q->nof_refs, nslot, nof_refs_x_symbol, nof_ref_symbols);

	q->refs = vec_malloc(q->nof_refs * sizeof(ref_t));
	if (!q->refs) {
		goto free_and_exit;
	}
	q->ch_est = vec_malloc(q->nof_refs * sizeof(cf_t));
	if (!q->ch_est) {
		goto free_and_exit;
	}

	ns = nslot;
	for (l = 0; l < nof_ref_symbols; l++) {

		c_init = 1024 * (7 * (ns + 1) + lp[l] + 1) * (2 * cell_id + 1)
				+ 2 * cell_id + N_cp;

		if (sequence_LTEPRS(&seq, 2 * 2 * MAX_PRB, c_init)) {
			goto free_and_exit;
		}

		v = refsignal_v(port_id, ns, lp[l]);

		for (i = 0; i < nof_refs_x_symbol; i++) {
			mp = i + MAX_PRB - nof_prb;

			/* generate signal */
			__real__ q->refs[idx(l,i)].simbol = (1 - 2 * (float) seq.c[2 * mp]) / sqrt(2);
			__imag__ q->refs[idx(l,i)].simbol = (1 - 2 * (float) seq.c[2 * mp + 1]) / sqrt(2);

			/* mapping to resource elements */
			q->refs[idx(l,i)].freq_idx = refsignal_k(i, v, cell_id)+GUARD_RE(nof_prb);
			q->refs[idx(l,i)].time_idx = lp[l];

			/* print only first slot */
			if (ns == 0) {
				DEBUG("(%-2d,%2d) is mapped to (%-2d,%2d) (mp=%d, v=%d)\n",
						l,i,q->refs[idx(l,i)].time_idx, q->refs[idx(l,i)].freq_idx-GUARD_RE(nof_prb), mp, v);
			}
		}
	}

	ret = 0;
free_and_exit:
	sequence_free(&seq);
	if (ret == -1) {
		refsignal_free(q);
	}
	return ret;
}

void refsignal_free(refsignal_t *q) {
	if (q->symbols_ref) {
		free(q->symbols_ref);
	}
	if (q->refs) {
		free(q->refs);
	}
	if (q->ch_est) {
		free(q->ch_est);
	}
	bzero(q, sizeof(refsignal_t));
}