mirror of https://gerrit.osmocom.org/osmo-tetra
812 lines
20 KiB
C
812 lines
20 KiB
C
/* GMR-1 SDR - pi2-CBPSK, pi4-CBPSK & pi4-CQPSK modulation support */
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/* See GMR-1 05.004 (ETSI TS 101 376-5-4 V1.2.1) - Section 5.1 & 5.2 */
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/* (C) 2011-2016 by Sylvain Munaut <tnt@246tNt.com>
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* All Rights Reserved
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*
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* This program is free software; you can redistribute it and/or modify
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* it under the terms of the GNU Affero General Public License as published by
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* the Free Software Foundation; either version 3 of the License, or
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* (at your option) any later version.
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*
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* This program is distributed in the hope that it will be useful,
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* but WITHOUT ANY WARRANTY; without even the implied warranty of
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* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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* GNU Affero General Public License for more details.
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*
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* You should have received a copy of the GNU Affero General Public License
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* along with this program. If not, see <http://www.gnu.org/licenses/>.
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*/
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/*! \addtogroup pi4cxpsk
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* @{
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*/
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/*! \file sdr/pi4cxpsk.c
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* \brief Osmocom GMR-1 pi2-CBPSK, pi4-CBPSK and pi4-CQPSK modulation support implementation
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*/
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#include <complex.h>
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#include <math.h>
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#include <errno.h>
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#include <stdint.h>
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#include <stdlib.h>
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#include <stdio.h>
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#include <osmocom/core/bits.h>
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#include <osmocom/dsp/cxvec.h>
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#include <osmocom/dsp/cxvec_math.h>
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#if 0
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#include <osmocom/gmr1/sdr/defs.h>
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#include <osmocom/gmr1/sdr/pi4cxpsk.h>
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#else
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#include "defs.h"
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#include "pi4cxpsk.h"
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#endif
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/*
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* Symbol notation
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*
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* idx data modulating
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* bits phase
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*
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* pi4-CBPSK:
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*
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* 0 0 0 * pi/2 = 1+0j
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* 1 1 2 * pi/2 = -1+0j
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*
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* pi4-CQPSK:
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*
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* 0 00 0 * pi/2 = 1+0j
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* 1 01 1 * pi/2 = 0+1j
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* 2 11 2 * pi/2 = -1+0j
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* 3 10 3 * pi/2 = 0-1j
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*
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* - idx : Symbol number
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* - data bits : The encoded data bits
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* - modulating phase : Phase used during modulation (in adition to the pi/4
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* continuous rotation)
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*/
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/*! \brief pi{2,4}-CBPSK symbols descriptions */
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static struct gmr1_pi4cxpsk_symbol gmr1_piNcbpsk_syms_bits[] = {
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{ 0, {0}, 0*M_PIf/2, 1+0*I },
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{ 1, {1}, 2*M_PIf/2, -1+0*I },
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};
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/*! \brief pi2-CBPSK modulation description */
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struct gmr1_pi4cxpsk_modulation gmr1_pi2cbpsk = {
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.rotation = M_PIf/2,
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.nbits = 1,
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.syms = gmr1_piNcbpsk_syms_bits,
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.bits = gmr1_piNcbpsk_syms_bits,
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};
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/*! \brief pi4-CBPSK modulation description */
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struct gmr1_pi4cxpsk_modulation gmr1_pi4cbpsk = {
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.rotation = M_PIf/4,
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.nbits = 1,
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.syms = gmr1_piNcbpsk_syms_bits,
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.bits = gmr1_piNcbpsk_syms_bits,
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};
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/*! \brief pi4-CQPSK symbols descriptions in symbol order */
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static struct gmr1_pi4cxpsk_symbol gmr1_pi4cqpsk_syms[] = {
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{ 0, {0,0}, 0*M_PIf/2, 1+0*I },
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{ 1, {0,1}, 1*M_PIf/2, 0+1*I },
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{ 2, {1,1}, 2*M_PIf/2, -1+0*I },
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{ 3, {1,0}, 3*M_PIf/2, 0-1*I },
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};
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/*! \brief pi4-CQPSK symbols descriptions in bits order */
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static struct gmr1_pi4cxpsk_symbol gmr1_pi4cqpsk_bits[] = {
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{ 0, {0,0}, 0*M_PIf/2, 1+0*I },
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{ 1, {0,1}, 1*M_PIf/2, 0+1*I },
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{ 3, {1,0}, 3*M_PIf/2, 0-1*I },
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{ 2, {1,1}, 2*M_PIf/2, -1+0*I },
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};
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/*! \brief pi4-CQPSK modulation description */
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struct gmr1_pi4cxpsk_modulation gmr1_pi4cqpsk = {
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.rotation = M_PIf/4,
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.nbits = 2,
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.syms = gmr1_pi4cqpsk_syms,
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.bits = gmr1_pi4cqpsk_bits,
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};
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/*! \brief Generate a reference signal for all sync sequences of a burst type
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* \param[in] burst_type Burst format description
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* \returns 0 for success. -ernno for errors
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*
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* The reference waveforms are stored inside the burst_type itself.
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*/
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static int
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_gmr1_pi4cxpsk_sync_gen_ref(struct gmr1_pi4cxpsk_burst *burst_type)
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{
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int i, j;
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/* Scan all possible training sequences */
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for (i=0; (i < GMR1_MAX_SYNC) && (burst_type->sync[i] != NULL); i++)
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{
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struct gmr1_pi4cxpsk_sync *csync;
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/* Scan all 'chunks' */
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for (csync=burst_type->sync[i]; csync->pos>=0; csync++)
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{
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int is_real = 1;
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/* Already done ? */
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if (csync->_ref)
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continue;
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/* Allocate it */
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csync->_ref = osmo_cxvec_alloc(csync->len);
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if (!csync->_ref)
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return -ENOMEM;
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/* Fill it */
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for (j=0; j<csync->len; j++) {
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int s;
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float complex mv;
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s = csync->syms[j];
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mv = burst_type->mod->syms[s].mod_val;
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if (cimagf(mv) != 0.0f)
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is_real = 0;
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csync->_ref->data[j] = mv;
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}
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csync->_ref->len = csync->len;
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if (is_real)
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csync->_ref->flags |= CXVEC_FLG_REAL_ONLY;
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}
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}
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return 0;
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}
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/*! \brief Find the sync sequence inside a burst
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* \param[in] burst_type Burst format description
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* \param[in] burst The input complex vector
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* \param[in] sps Input sample per symbol (how much to decimate)
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* \param[out] toa Pointer to estimated fractional TOA return variable
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* \param[out] pwr Pointer to power return variable
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* \returns >=0 index of found sync sequence. -errno for errors
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*
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* The burst input is expected to be longer than the burst. The extra amount
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* of samples will be the search window.
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*/
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static int
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_gmr1_pi4cxpsk_sync_find(struct gmr1_pi4cxpsk_burst *burst_type,
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struct osmo_cxvec *burst, int sps,
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float *toa, float *pwr)
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{
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struct osmo_cxvec _win, *win = &_win;
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struct osmo_cxvec *corr, *corr_tmp;
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int i, j, w;
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float p_toa = 0.0f, p_pwr = 0.0f, p_idx = -1;
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int rv;
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/* Window size */
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w = burst->len - (burst_type->len * sps) + 1;
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/* Corr vectors */
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corr = osmo_cxvec_alloc(w);
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corr_tmp = osmo_cxvec_alloc(w);
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if (!corr || !corr_tmp) {
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rv = -ENOMEM;
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goto err;
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}
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/* Scan all possible training sequences */
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for (i=0; (i < GMR1_MAX_SYNC) && (burst_type->sync[i] != NULL); i++)
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{
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struct gmr1_pi4cxpsk_sync *csync;
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float s_toa, s_pwr;
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float complex s_peak;
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int first = 1, tl = 0;
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/* Correlate all 'chunks' */
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for (csync=burst_type->sync[i]; csync->pos>=0; csync++)
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{
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int b, l;
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/* Extract the window of data to correlate with */
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b = csync->pos * sps;
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l = (csync->len * sps) + w - 1;
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osmo_cxvec_init_from_data(win, &burst->data[b], l);
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/* Correlate */
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osmo_cxvec_correlate(csync->_ref, win, sps, first ? corr : corr_tmp);
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/* If not the first, then combine results */
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if (!first)
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for (j=0; j<w; j++)
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corr->data[j] += corr_tmp->data[j];
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first = 0;
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/* Add length of this 'chunk' */
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tl += csync->_ref->len;
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}
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/* Only considered properly aligned correlation */
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for (j=0; j<corr->len; j++)
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corr->data[j] = (crealf(corr->data[j]) > 0.0f) ? crealf(corr->data[j]) : 0.0f;
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/* Find peak */
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s_toa = osmo_cxvec_peak_energy_find(corr, 3, PEAK_EARLY_LATE, &s_peak);
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s_peak /= (float)tl;
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s_pwr = osmo_normsqf(s_peak);
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if (s_pwr > p_pwr) {
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/* Record the new winner */
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p_pwr = s_pwr;
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p_toa = s_toa;
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p_idx = i;
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/* Debug winner */
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DEBUG_SIGNAL("pi4cxpsk_corr", corr);
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}
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}
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/* Return winner */
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if (toa)
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*toa = p_toa;
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if (pwr)
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*pwr = p_pwr;
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rv = p_idx;
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/* Clean up */
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err:
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osmo_cxvec_free(corr_tmp);
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osmo_cxvec_free(corr);
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return rv;
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}
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/*! \brief Perform final alignement (1 sps and proper length/alignement)
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* \param[in] burst_type Burst format description
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* \param[in] burst The input complex vector
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* \param[in] sps Input sample per symbol (how much to decimate)
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* \param[in] toa Estimated fractional TOA to align to
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* \returns 0 for success. -errno for errors
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*
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* In the end, each complex inside the burst corresponds to a sample,
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* aligned according to the burst description.
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*/
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static int
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_gmr1_pi4cxpsk_align(struct gmr1_pi4cxpsk_burst *burst_type,
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struct osmo_cxvec *burst, int sps, float toa)
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{
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int i, rv = 0;
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if (sps >= 4) {
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/* Easy case: we can just round everything and not use
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* fractional TOA. At worse we have a +-1/8 symbol alignement
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* error, which doesn't matter */
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int d;
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d = roundf(toa);
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for (i=0; i<burst_type->len; i++)
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burst->data[i] = burst->data[i*sps+d];
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burst->len = burst_type->len;
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} else {
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/* Hard case: we need to interpolate every point */
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struct osmo_cxvec *conv = NULL, *src = burst;
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int ofs_int;
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float ofs_frac;
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ofs_int = roundf(toa);
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ofs_frac = toa - ofs_int;
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src = burst;
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/* Fractional part (if reasonable) */
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if (fabs(ofs_frac) > 0.1f) {
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const int N = 21;
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float complex _data[N];
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struct osmo_cxvec _sinc_pulse, *sinc_pulse = &_sinc_pulse;
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/* Build sinc pulse */
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for (i=0; i<N; i++)
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_data[i] = osmo_sinc(
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M_PIf * ((float)(i - (N>>1)) + ofs_frac)
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);
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osmo_cxvec_init_from_data(sinc_pulse, _data, N);
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sinc_pulse->flags |= CXVEC_FLG_REAL_ONLY;
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/* Apply it */
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conv = osmo_cxvec_convolve(sinc_pulse, burst, CONV_NO_DELAY, NULL);
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src = conv;
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}
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/* Integer part */
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for (i=0; i<burst_type->len; i++) {
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int j = (i*sps) + ofs_int;
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if (j < 0 || j >= src->len)
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burst->data[i] = 0.0f;
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else
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burst->data[i] = src->data[j];
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}
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burst->len = burst_type->len;
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/* Cleanup */
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if (conv)
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osmo_cxvec_free(conv);
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}
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DEBUG_SIGNAL("pi4cxpsk_align", burst);
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return rv;
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}
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/*! \brief Estimate fine frequency error based on sync sequence chunks phase
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* \param[in] burst_type Burst format description
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* \param[in] burst The input complex vector (1 sample per symbol)
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* \param[in] sync_id ID of the sync sequence to use
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* \param[out] freq_error Pointer to the return frequency error variable (rad/sym)
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* \returns 0 for success. -errno for errors
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*
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* The method needs several chunks to estimate the frequency error. If
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* there is only one, 0.0f is returned.
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*/
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static int
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_gmr1_pi4cxpsk_freq_err(struct gmr1_pi4cxpsk_burst *burst_type,
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struct osmo_cxvec *burst, int sync_id,
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float *freq_error)
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{
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struct gmr1_pi4cxpsk_sync *csync;
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int n, i, j;
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/* Count the chunks */
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for (n=0,csync=burst_type->sync[sync_id]; csync->pos>=0; n++,csync++);
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/* Do we have several ? */
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if (n > 1)
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{
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float complex corr[n];
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float pos[n], f;
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/* Correlate all 'chunks' */
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for (i=0; i<n; i++)
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{
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csync = &burst_type->sync[sync_id][i];
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corr[i] = 0.0f;
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pos[i] = (float)csync->pos + (float)csync->len / 2.0f;
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for (j=0; j<csync->len; j++)
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corr[i] +=
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conjf(csync->_ref->data[j]) *
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burst->data[csync->pos+j];
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}
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/* From the data points, extract a single value */
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f = 0.0f;
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for (i=1; i<n; i++)
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f += cargf(corr[i] * conjf(corr[0])) / (pos[i] - pos[0]);
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f /= n - 1;
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*freq_error = f;
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}
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else
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{
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/* FIXME: How the hell to do this reliably ??? */
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*freq_error = 0.0f;
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}
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return 0;
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}
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/*! \brief Compute the current phase of a burst (compared to a 0 reference)
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* \param[in] burst_type Burst format description
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* \param[in] burst The input complex vector (1 sample per symbol)
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* \param[in] sync_id ID of the sync sequence to use
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* \param[out] phasor Pointer to the return phase variable
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* \returns 0 for success. -errno for errors
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*/
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static int
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_gmr1_pi4cxpsk_phase(struct gmr1_pi4cxpsk_burst *burst_type,
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struct osmo_cxvec *burst, int sync_id,
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float complex *phasor)
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{
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struct gmr1_pi4cxpsk_sync *csync;
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float complex corr = 0.0f;
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int i;
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/* Correlate all 'chunks' */
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for (csync=burst_type->sync[sync_id]; csync->pos>=0; csync++)
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for (i=0; i<csync->len; i++)
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corr += conjf(csync->_ref->data[i]) *
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burst->data[csync->pos+i];
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*phasor = corr / cabsf(corr);
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return 0;
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}
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/*! \brief Convert complex vector into soft symbols based on phase
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* \param[in] burst_type Burst format description
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* \param[in] burst The input complex vector
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* \returns Newly malloc'd array of float of same legnth as burst
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*
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* Phase must have been aligned properly obviously
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*/
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static float *
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_gmr1_pi4cxpsk_soft_symbols(struct gmr1_pi4cxpsk_burst *burst_type,
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struct osmo_cxvec *burst)
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{
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float *ssyms;
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float d;
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int i;
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ssyms = malloc(sizeof(float) * burst->len);
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if (!ssyms)
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return NULL;
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d = (2.0f * M_PIf) / (1<<burst_type->mod->nbits);
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for (i=0; i<burst->len; i++)
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ssyms[i] = cargf(burst->data[i]) / d;
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return ssyms;
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}
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/*! \brief Convert a soft symbols array into softbits
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* \param[in] burst_type Burst format description
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* \param[in] ssyms Soft symbols array
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* \param[out] ebits Encoded soft bits return array
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* \returns 0 for success. -errno for errors
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*/
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static int
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_gmr1_pi4cxpsk_soft_bits(struct gmr1_pi4cxpsk_burst *burst_type,
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float *ssyms, sbit_t *ebits)
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{
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struct gmr1_pi4cxpsk_modulation *mod = burst_type->mod;
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struct gmr1_pi4cxpsk_data *dc;
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int mask = (1<<mod->nbits) - 1;
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int i,j,k;
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k=0;
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for (dc = burst_type->data; dc->pos>=0; dc++) {
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for (i=dc->pos; i<dc->pos+dc->len; i++)
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{
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float sv, svr;
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int sp, ss, d;
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sv = ssyms[i];
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svr = roundf(sv);
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sp = (int)svr & mask;
|
|
ss = (svr > sv ? (sp-1) : (sp+1)) & mask;
|
|
|
|
d = roundf((2.0f * fabs(svr - sv)) * 64.0f);
|
|
|
|
for (j=0; j<mod->nbits; j++) {
|
|
uint8_t vp = mod->syms[sp].data[j];
|
|
uint8_t vs = mod->syms[ss].data[j];
|
|
sbit_t v = 127 - ((vp^vs) ? d : (d>>1));
|
|
ebits[k++] = vp ? -v : v;
|
|
}
|
|
}
|
|
}
|
|
|
|
return 0;
|
|
}
|
|
|
|
/*! \brief All-in-one pi4-CxPSK demodulation method
|
|
* \param[in] burst_type Burst format description
|
|
* \param[in] burst_in Complex signal of the burst
|
|
* \param[in] sps Oversampling used in the input complex signal
|
|
* \param[in] freq_shift Frequency shift to pre-apply to burst_in (rad/sym)
|
|
* \param[out] ebits Encoded soft bits return array
|
|
* \param[out] sync_id_p Pointer to sync sequence id return variable
|
|
* \param[out] toa_p Pointer to TOA return variable
|
|
* \param[out] freq_err_p Pointer to frequency error return variable (rad/sym)
|
|
* \returns 0 for success. -errno for errors
|
|
*
|
|
* burst_in is expected to be longer than necessary. Any extra length will be
|
|
* used as 'search window' to find proper alignement. Good practice is to have
|
|
* a few samples too much in front and a few samples after the expected TOA.
|
|
*/
|
|
int
|
|
gmr1_pi4cxpsk_demod(struct gmr1_pi4cxpsk_burst *burst_type,
|
|
struct osmo_cxvec *burst_in, int sps, float freq_shift,
|
|
sbit_t *ebits,
|
|
int *sync_id_p, float *toa_p, float *freq_err_p)
|
|
{
|
|
struct osmo_cxvec *burst = NULL;
|
|
float toa, fine_freq_error;
|
|
float complex phasor;
|
|
float *ssyms = NULL;
|
|
int sync_id;
|
|
int rv = 0;
|
|
|
|
/* Generate reference sync bursts */
|
|
rv = _gmr1_pi4cxpsk_sync_gen_ref(burst_type);
|
|
if (rv)
|
|
goto err;
|
|
|
|
/* Normalize the burst and counter rotate by pi/4 */
|
|
burst = osmo_cxvec_sig_normalize(burst_in, 1, (freq_shift - burst_type->mod->rotation) / sps, NULL);
|
|
if (!burst) {
|
|
rv = -ENOMEM;
|
|
goto err;
|
|
}
|
|
|
|
DEBUG_SIGNAL("pi4cxpsk_burst", burst);
|
|
|
|
/* Find the training sequence */
|
|
sync_id = _gmr1_pi4cxpsk_sync_find(burst_type, burst, sps, &toa, NULL);
|
|
if (sync_id < 0) {
|
|
rv = sync_id;
|
|
goto err;
|
|
}
|
|
|
|
if (sync_id_p)
|
|
*sync_id_p = sync_id;
|
|
|
|
if (toa_p)
|
|
*toa_p = toa;
|
|
|
|
/* Align and decimate the burst */
|
|
rv = _gmr1_pi4cxpsk_align(burst_type, burst, sps, toa);
|
|
if (rv)
|
|
goto err;
|
|
|
|
#if 0
|
|
/* Use sync sequence to find fine freq error */
|
|
rv = _gmr1_pi4cxpsk_freq_err(burst_type, burst, sync_id, &fine_freq_error);
|
|
if (rv)
|
|
goto err;
|
|
|
|
if (freq_err_p)
|
|
*freq_err_p = fine_freq_error;
|
|
|
|
/* Compensate fine freq error (in-place) */
|
|
if (fine_freq_error != 0.0f)
|
|
osmo_cxvec_rotate(burst, -fine_freq_error, burst);
|
|
|
|
/* Find current phase using sync sequence */
|
|
_gmr1_pi4cxpsk_phase(burst_type, burst, sync_id, &phasor);
|
|
|
|
/* Align phase for detection */
|
|
osmo_cxvec_scale(burst, conjf(phasor), burst);
|
|
#endif
|
|
DEBUG_SIGNAL("pi4cxpsk_final", burst);
|
|
|
|
/* Convert phase to soft symbols */
|
|
ssyms = _gmr1_pi4cxpsk_soft_symbols(burst_type, burst);
|
|
if (!ssyms) {
|
|
rv = -ENOMEM;
|
|
goto err;
|
|
}
|
|
|
|
/* Convert to data bits */
|
|
rv = _gmr1_pi4cxpsk_soft_bits(burst_type, ssyms, ebits);
|
|
if (rv)
|
|
goto err;
|
|
|
|
/* Cleanup */
|
|
err:
|
|
free(ssyms);
|
|
osmo_cxvec_free(burst);
|
|
|
|
return rv;
|
|
}
|
|
|
|
/*! \brief Try to identify burst type by matching training sequences
|
|
* \param[in] burst_types Array of burst types to test (NULL terminated)
|
|
* \param[in] e_toa Expected time of arrival
|
|
* \param[in] burst_in Complex signal of the burst
|
|
* \param[in] sps Oversampling used in the input complex signal
|
|
* \param[in] freq_shift Frequency shift to pre-apply to burst_in (rad/sym)
|
|
* \param[out] bt_id_p Pointer to burst type ID return variable
|
|
* \param[out] sync_id_p Pointer to sync sequence id return variable
|
|
* \param[out] toa_p Pointer to TOA return variable
|
|
* \returns -errno for errors, 0 for success
|
|
*
|
|
* The various burst types must be compatible in length and modulation !
|
|
*/
|
|
int
|
|
gmr1_pi4cxpsk_detect(struct gmr1_pi4cxpsk_burst **burst_types, float e_toa,
|
|
struct osmo_cxvec *burst_in, int sps, float freq_shift,
|
|
int *bt_id_p, int *sync_id_p, float *toa_p)
|
|
{
|
|
struct gmr1_pi4cxpsk_burst *bt;
|
|
struct osmo_cxvec *burst = NULL;
|
|
int id, p_id=-1, p_sid=-1;
|
|
float p_toa=0.0f, p_pwr=0.0f;
|
|
int rv = 0;
|
|
|
|
/* Normalize the burst and counter rotate */
|
|
burst = osmo_cxvec_sig_normalize(burst_in, 1, (freq_shift - burst_types[0]->mod->rotation) / sps, NULL);
|
|
if (!burst) {
|
|
rv = -ENOMEM;
|
|
goto err;
|
|
}
|
|
|
|
DEBUG_SIGNAL("pi4cxpsk_burst", burst);
|
|
|
|
/* Scan all burst types */
|
|
for (id=0; burst_types[id]; id++)
|
|
{
|
|
int sid;
|
|
float toa, pwr;
|
|
|
|
bt = burst_types[id];
|
|
|
|
/* Generate reference sync bursts */
|
|
rv = _gmr1_pi4cxpsk_sync_gen_ref(bt);
|
|
if (rv)
|
|
goto err;
|
|
|
|
/* Try this burst type */
|
|
sid = _gmr1_pi4cxpsk_sync_find(bt, burst, sps, &toa, &pwr);
|
|
if (sid < 0) {
|
|
rv = sid;
|
|
goto err;
|
|
}
|
|
|
|
/* If we have an expected, toa, we 'modulate' power */
|
|
if (e_toa >= 0.0f)
|
|
pwr /= fabs(e_toa - toa);
|
|
|
|
/* Check for better ? */
|
|
if (pwr > p_pwr) {
|
|
p_id = id;
|
|
p_sid = sid;
|
|
p_pwr = pwr;
|
|
p_toa = toa;
|
|
}
|
|
}
|
|
|
|
if (bt_id_p)
|
|
*bt_id_p = p_id;
|
|
if (sync_id_p)
|
|
*sync_id_p = p_sid;
|
|
if (toa_p)
|
|
*toa_p = p_toa;
|
|
|
|
/* Done */
|
|
err:
|
|
osmo_cxvec_free(burst);
|
|
|
|
return rv;
|
|
}
|
|
|
|
/*! \brief Estimates modulation order by comparing power of x^2 vs x^4
|
|
* \param[in] burst_in Complex signal of the burst
|
|
* \param[in] sps Oversampling used in the input complex signal
|
|
* \param[in] freq_shift Frequency shift to pre-apply to burst_in (rad/sym)
|
|
* \returns <0 for error. 2 for BPSK, 4 for QPSK.
|
|
*
|
|
* Since x^4 only make sense for pi/4 variant, the pi/4 counter rotation is
|
|
* always applied.
|
|
*/
|
|
int
|
|
gmr1_pi4cxpsk_mod_order(struct osmo_cxvec *burst_in, int sps, float freq_shift)
|
|
{
|
|
struct osmo_cxvec *burst = NULL;
|
|
float complex sb = 0.0f, sq = 0.0f;
|
|
float pb, pq;
|
|
int rv, i;
|
|
|
|
/* Normalize the burst and counter rotate by pi/4 */
|
|
burst = osmo_cxvec_sig_normalize(burst_in, 1, (freq_shift - (M_PIf/4)) / sps, NULL);
|
|
if (!burst) {
|
|
rv = -ENOMEM;
|
|
goto err;
|
|
}
|
|
|
|
DEBUG_SIGNAL("pi4cxpsk_burst", burst);
|
|
|
|
/* Detect modulation order by estimating power of x^2 vs x^4 */
|
|
for (i=0; i<burst->len; i++) {
|
|
float complex v;
|
|
v = burst->data[i];
|
|
v = (v * v) / osmo_normsqf(v);
|
|
sb += v;
|
|
sq += v * v;
|
|
}
|
|
|
|
pb = osmo_normsqf(sb);
|
|
pq = osmo_normsqf(sq);
|
|
|
|
rv = pb < (pq / 2.0f) ? 4 : 2;
|
|
|
|
/* Done */
|
|
err:
|
|
osmo_cxvec_free(burst);
|
|
|
|
return rv;
|
|
}
|
|
|
|
/*! \brief Modulates (currently at 1 sps)
|
|
* \param[in] burst_type Burst format description
|
|
* \param[in] ebits Encoded hard bits to pack in the burst
|
|
* \param[in] sync_id The sequence id to use (0 if burst_type only has one)
|
|
* \param[out] burst_out Complex signal to fill with modulated symbols
|
|
* \returns 0 for success. -errno for errors
|
|
*
|
|
* burst_out is expected to be long enough to contains the resulting symbols
|
|
* see the burst_type structure for how long that is.
|
|
*/
|
|
int
|
|
gmr1_pi4cxpsk_mod(struct gmr1_pi4cxpsk_burst *burst_type,
|
|
ubit_t *ebits, int sync_id, struct osmo_cxvec *burst_out)
|
|
{
|
|
struct gmr1_pi4cxpsk_modulation *mod = burst_type->mod;
|
|
struct gmr1_pi4cxpsk_sync *sync;
|
|
struct gmr1_pi4cxpsk_data *data;
|
|
int rv, i, j, k;
|
|
|
|
/* Check the output vector is long enough */
|
|
if (burst_out->max_len < burst_type->len) {
|
|
rv = -ENOMEM;
|
|
goto err;
|
|
}
|
|
|
|
burst_out->len = burst_type->len;
|
|
|
|
/* Generate reference sync bursts */
|
|
rv = _gmr1_pi4cxpsk_sync_gen_ref(burst_type);
|
|
if (rv)
|
|
goto err;
|
|
|
|
/* Fill guard */
|
|
for (i=0; i<burst_type->guard_pre; i++)
|
|
burst_out->data[i] = 0.0f;
|
|
for (i=0; i<burst_type->guard_post; i++)
|
|
burst_out->data[burst_out->len - i - 1] = 0.0f;
|
|
|
|
/* Fill training sequence */
|
|
for (sync=burst_type->sync[sync_id]; sync->len; sync++)
|
|
{
|
|
for (i=0; i<sync->len; i++)
|
|
burst_out->data[sync->pos+i] = sync->_ref->data[i];
|
|
}
|
|
|
|
/* Fill ebits */
|
|
k = 0;
|
|
|
|
for (data=burst_type->data; data->len; data++)
|
|
{
|
|
for (i=0; i<data->len; i++)
|
|
{
|
|
int sym = 0;
|
|
|
|
for (j=0; j<mod->nbits; j++)
|
|
sym = (sym << 1) | ebits[k++];
|
|
|
|
burst_out->data[data->pos+i] = burst_type->mod->bits[sym].mod_val;
|
|
}
|
|
}
|
|
|
|
/* Apply the final pi/4 rotation */
|
|
osmo_cxvec_rotate(burst_out, burst_type->mod->rotation, burst_out);
|
|
|
|
rv = 0;
|
|
|
|
err:
|
|
return rv;
|
|
}
|
|
|
|
/*! @} */
|