1912 lines
46 KiB
C++
1912 lines
46 KiB
C++
/*
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* Copyright 2008, 2011 Free Software Foundation, Inc.
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*
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* SPDX-License-Identifier: AGPL-3.0+
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*
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* This software is distributed under the terms of the GNU Affero Public License.
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* See the COPYING file in the main directory for details.
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*
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* This use of this software may be subject to additional restrictions.
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* See the LEGAL file in the main directory for details.
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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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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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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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#ifdef HAVE_CONFIG_H
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#include "config.h"
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#endif
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#include "sigProcLib.h"
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#include "GSMCommon.h"
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#include "Logger.h"
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#include "Resampler.h"
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extern "C" {
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#include "convolve.h"
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#include "scale.h"
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#include "mult.h"
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}
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using namespace GSM;
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#define TABLESIZE 1024
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#define DELAYFILTS 64
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/* Clipping detection threshold */
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#define CLIP_THRESH 30000.0f
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/** Lookup tables for trigonometric approximation */
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static float sincTable[TABLESIZE+1]; // add 1 element for wrap around
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/** Constants */
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static const float M_PI_F = (float)M_PI;
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/* Precomputed rotation vectors */
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static signalVector *GMSKRotation4 = NULL;
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static signalVector *GMSKReverseRotation4 = NULL;
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static signalVector *GMSKRotation1 = NULL;
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static signalVector *GMSKReverseRotation1 = NULL;
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/* Precomputed fractional delay filters */
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static signalVector *delayFilters[DELAYFILTS];
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static const Complex<float> psk8_table[8] = {
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Complex<float>(-0.70710678, 0.70710678),
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Complex<float>( 0.0, -1.0),
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Complex<float>( 0.0, 1.0),
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Complex<float>( 0.70710678, -0.70710678),
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Complex<float>(-1.0, 0.0),
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Complex<float>(-0.70710678, -0.70710678),
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Complex<float>( 0.70710678, 0.70710678),
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Complex<float>( 1.0, 0.0),
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};
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/* Downsampling filterbank - 4 SPS to 1 SPS */
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#define DOWNSAMPLE_IN_LEN 624
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#define DOWNSAMPLE_OUT_LEN 156
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static Resampler *dnsampler = NULL;
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/*
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* RACH and midamble correlation waveforms. Store the buffer separately
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* because we need to allocate it explicitly outside of the signal vector
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* constructor. This is because C++ (prior to C++11) is unable to natively
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* perform 16-byte memory alignment required by many SSE instructions.
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*/
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struct CorrelationSequence {
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CorrelationSequence() : sequence(NULL), buffer(NULL), toa(0.0)
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{
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}
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~CorrelationSequence()
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{
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delete sequence;
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}
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signalVector *sequence;
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void *buffer;
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float toa;
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complex gain;
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};
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/*
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* Gaussian and empty modulation pulses. Like the correlation sequences,
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* store the runtime (Gaussian) buffer separately because of needed alignment
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* for SSE instructions.
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*/
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struct PulseSequence {
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PulseSequence() : c0(NULL), c1(NULL), c0_inv(NULL), empty(NULL)
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{
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}
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~PulseSequence()
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{
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delete c0;
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delete c1;
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delete c0_inv;
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delete empty;
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}
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signalVector *c0;
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signalVector *c1;
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signalVector *c0_inv;
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signalVector *empty;
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};
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static CorrelationSequence *gMidambles[] = {NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL};
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static CorrelationSequence *gEdgeMidambles[] = {NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL};
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static CorrelationSequence *gRACHSequences[] = {NULL,NULL,NULL};
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static PulseSequence *GSMPulse1 = NULL;
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static PulseSequence *GSMPulse4 = NULL;
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void sigProcLibDestroy()
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{
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for (int i = 0; i < 8; i++) {
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delete gMidambles[i];
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delete gEdgeMidambles[i];
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gMidambles[i] = NULL;
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gEdgeMidambles[i] = NULL;
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}
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for (int i = 0; i < DELAYFILTS; i++) {
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delete delayFilters[i];
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delayFilters[i] = NULL;
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}
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for (int i = 0; i < 3; i++) {
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delete gRACHSequences[i];
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gRACHSequences[i] = NULL;
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}
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delete GMSKRotation1;
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delete GMSKReverseRotation1;
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delete GMSKRotation4;
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delete GMSKReverseRotation4;
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delete GSMPulse1;
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delete GSMPulse4;
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delete dnsampler;
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GMSKRotation1 = NULL;
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GMSKRotation4 = NULL;
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GMSKReverseRotation4 = NULL;
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GMSKReverseRotation1 = NULL;
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GSMPulse1 = NULL;
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GSMPulse4 = NULL;
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}
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static float vectorNorm2(const signalVector &x)
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{
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signalVector::const_iterator xPtr = x.begin();
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float Energy = 0.0;
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for (;xPtr != x.end();xPtr++) {
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Energy += xPtr->norm2();
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}
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return Energy;
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}
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/*
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* Initialize 4 sps and 1 sps rotation tables
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*/
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static void initGMSKRotationTables()
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{
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size_t len1 = 157, len4 = 625;
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GMSKRotation4 = new signalVector(len4);
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GMSKReverseRotation4 = new signalVector(len4);
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signalVector::iterator rotPtr = GMSKRotation4->begin();
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signalVector::iterator revPtr = GMSKReverseRotation4->begin();
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auto phase = 0.0;
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while (rotPtr != GMSKRotation4->end()) {
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*rotPtr++ = complex(cos(phase), sin(phase));
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*revPtr++ = complex(cos(-phase), sin(-phase));
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phase += M_PI / 2.0 / 4.0;
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}
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GMSKRotation1 = new signalVector(len1);
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GMSKReverseRotation1 = new signalVector(len1);
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rotPtr = GMSKRotation1->begin();
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revPtr = GMSKReverseRotation1->begin();
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phase = 0.0;
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while (rotPtr != GMSKRotation1->end()) {
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*rotPtr++ = complex(cos(phase), sin(phase));
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*revPtr++ = complex(cos(-phase), sin(-phase));
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phase += M_PI / 2.0;
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}
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}
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static void GMSKRotate(signalVector &x, int sps)
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{
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#if HAVE_NEON
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size_t len;
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signalVector *a, *b, *out;
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a = &x;
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out = &x;
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len = out->size();
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if (len == 157)
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len--;
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if (sps == 1)
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b = GMSKRotation1;
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else
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b = GMSKRotation4;
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mul_complex((float *) out->begin(),
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(float *) a->begin(),
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(float *) b->begin(), len);
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#else
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signalVector::iterator rotPtr, xPtr = x.begin();
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if (sps == 1)
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rotPtr = GMSKRotation1->begin();
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else
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rotPtr = GMSKRotation4->begin();
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if (x.isReal()) {
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while (xPtr < x.end()) {
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*xPtr = *rotPtr++ * (xPtr->real());
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xPtr++;
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}
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}
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else {
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while (xPtr < x.end()) {
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*xPtr = *rotPtr++ * (*xPtr);
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xPtr++;
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}
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}
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#endif
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}
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static bool GMSKReverseRotate(signalVector &x, int sps)
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{
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signalVector::iterator rotPtr, xPtr= x.begin();
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if (sps == 1)
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rotPtr = GMSKReverseRotation1->begin();
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else if (sps == 4)
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rotPtr = GMSKReverseRotation4->begin();
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else
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return false;
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if (x.isReal()) {
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while (xPtr < x.end()) {
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*xPtr = *rotPtr++ * (xPtr->real());
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xPtr++;
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}
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}
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else {
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while (xPtr < x.end()) {
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*xPtr = *rotPtr++ * (*xPtr);
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xPtr++;
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}
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}
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return true;
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}
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/** Convolution type indicator */
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enum ConvType {
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START_ONLY,
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NO_DELAY,
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CUSTOM,
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UNDEFINED,
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};
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static signalVector *convolve(const signalVector *x, const signalVector *h,
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signalVector *y, ConvType spanType,
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size_t start = 0, size_t len = 0)
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{
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int rc;
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size_t head = 0, tail = 0;
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bool alloc = false, append = false;
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const signalVector *_x = NULL;
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if (!x || !h)
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return NULL;
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switch (spanType) {
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case START_ONLY:
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start = 0;
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head = h->size() - 1;
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len = x->size();
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if (x->getStart() < head)
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append = true;
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break;
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case NO_DELAY:
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start = h->size() / 2;
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head = start;
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tail = start;
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len = x->size();
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append = true;
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break;
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case CUSTOM:
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if (start < h->size() - 1) {
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head = h->size() - start;
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append = true;
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}
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if (start + len > x->size()) {
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tail = start + len - x->size();
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append = true;
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}
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break;
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default:
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return NULL;
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}
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/*
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* Error if the output vector is too small. Create the output vector
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* if the pointer is NULL.
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*/
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if (y && (len > y->size()))
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return NULL;
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if (!y) {
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y = new signalVector(len, convolve_h_alloc, free);
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alloc = true;
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}
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/* Prepend or post-pend the input vector if the parameters require it */
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if (append)
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_x = new signalVector(*x, head, tail);
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else
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_x = x;
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/*
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* Four convolve types:
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* 1. Complex-Real (aligned)
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* 2. Complex-Complex (aligned)
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* 3. Complex-Real (!aligned)
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* 4. Complex-Complex (!aligned)
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*/
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if (h->isReal() && h->isAligned()) {
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rc = convolve_real((float *) _x->begin(), _x->size(),
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(float *) h->begin(), h->size(),
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(float *) y->begin(), y->size(),
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start, len);
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} else if (!h->isReal() && h->isAligned()) {
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rc = convolve_complex((float *) _x->begin(), _x->size(),
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(float *) h->begin(), h->size(),
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(float *) y->begin(), y->size(),
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start, len);
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} else if (h->isReal() && !h->isAligned()) {
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rc = base_convolve_real((float *) _x->begin(), _x->size(),
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(float *) h->begin(), h->size(),
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(float *) y->begin(), y->size(),
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start, len);
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} else if (!h->isReal() && !h->isAligned()) {
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rc = base_convolve_complex((float *) _x->begin(), _x->size(),
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(float *) h->begin(), h->size(),
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(float *) y->begin(), y->size(),
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start, len);
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} else {
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rc = -1;
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}
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if (append)
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delete _x;
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if (rc < 0) {
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if (alloc)
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delete y;
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return NULL;
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}
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return y;
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}
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/*
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* Generate static EDGE linear equalizer. This equalizer is not adaptive.
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* Filter taps are generated from the inverted 1 SPS impulse response of
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* the EDGE pulse shape captured after the downsampling filter.
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*/
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static bool generateInvertC0Pulse(PulseSequence *pulse)
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{
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if (!pulse)
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return false;
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pulse->c0_inv = new signalVector((complex *) convolve_h_alloc(5), 0, 5, convolve_h_alloc, free);
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pulse->c0_inv->isReal(true);
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pulse->c0_inv->setAligned(false);
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signalVector::iterator xP = pulse->c0_inv->begin();
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*xP++ = 0.15884;
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*xP++ = -0.43176;
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*xP++ = 1.00000;
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*xP++ = -0.42608;
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*xP++ = 0.14882;
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return true;
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}
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static bool generateC1Pulse(int sps, PulseSequence *pulse)
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{
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int len;
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if (!pulse)
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return false;
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switch (sps) {
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case 4:
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len = 8;
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break;
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default:
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return false;
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}
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pulse->c1 = new signalVector((complex *) convolve_h_alloc(len), 0, len, convolve_h_alloc, free);
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pulse->c1->isReal(true);
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/* Enable alignment for SSE usage */
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pulse->c1->setAligned(true);
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signalVector::iterator xP = pulse->c1->begin();
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switch (sps) {
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case 4:
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/* BT = 0.30 */
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*xP++ = 0.0;
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*xP++ = 8.16373112e-03;
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*xP++ = 2.84385729e-02;
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*xP++ = 5.64158904e-02;
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*xP++ = 7.05463553e-02;
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*xP++ = 5.64158904e-02;
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*xP++ = 2.84385729e-02;
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*xP++ = 8.16373112e-03;
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}
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return true;
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}
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static PulseSequence *generateGSMPulse(int sps)
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{
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int len;
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float arg, avg, center;
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PulseSequence *pulse;
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if ((sps != 1) && (sps != 4))
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return NULL;
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/* Store a single tap filter used for correlation sequence generation */
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pulse = new PulseSequence();
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pulse->empty = new signalVector(1);
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pulse->empty->isReal(true);
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*(pulse->empty->begin()) = 1.0f;
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/*
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* For 4 samples-per-symbol use a precomputed single pulse Laurent
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* approximation. This should yields below 2 degrees of phase error at
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* the modulator output. Use the existing pulse approximation for all
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* other oversampling factors.
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*/
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switch (sps) {
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case 4:
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len = 16;
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break;
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case 1:
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default:
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len = 4;
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}
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pulse->c0 = new signalVector((complex *) convolve_h_alloc(len), 0, len, convolve_h_alloc, free);
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pulse->c0->isReal(true);
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/* Enable alingnment for SSE usage */
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pulse->c0->setAligned(true);
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signalVector::iterator xP = pulse->c0->begin();
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if (sps == 4) {
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*xP++ = 0.0;
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*xP++ = 4.46348606e-03;
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*xP++ = 2.84385729e-02;
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*xP++ = 1.03184855e-01;
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*xP++ = 2.56065552e-01;
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*xP++ = 4.76375085e-01;
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*xP++ = 7.05961177e-01;
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*xP++ = 8.71291644e-01;
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*xP++ = 9.29453645e-01;
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*xP++ = 8.71291644e-01;
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*xP++ = 7.05961177e-01;
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*xP++ = 4.76375085e-01;
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*xP++ = 2.56065552e-01;
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*xP++ = 1.03184855e-01;
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*xP++ = 2.84385729e-02;
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*xP++ = 4.46348606e-03;
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generateC1Pulse(sps, pulse);
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} else {
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center = (float) (len - 1.0) / 2.0;
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/* GSM pulse approximation */
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for (int i = 0; i < len; i++) {
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arg = ((float) i - center) / (float) sps;
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*xP++ = 0.96 * exp(-1.1380 * arg * arg -
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0.527 * arg * arg * arg * arg);
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}
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avg = sqrtf(vectorNorm2(*pulse->c0) / sps);
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xP = pulse->c0->begin();
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for (int i = 0; i < len; i++)
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*xP++ /= avg;
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}
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/*
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* Current form of the EDGE equalization filter non-realizable at 4 SPS.
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* Load the onto both 1 SPS and 4 SPS objects for convenience. Note that
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* the EDGE demodulator downsamples to 1 SPS prior to equalization.
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*/
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generateInvertC0Pulse(pulse);
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return pulse;
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}
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/* Convert -1..+1 soft bits to 0..1 soft bits */
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void vectorSlicer(float *dest, const float *src, size_t len)
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{
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size_t i;
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for (i = 0; i < len; i++) {
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dest[i] = 0.5 * (src[i] + 1.0f);
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if (dest[i] > 1.0)
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dest[i] = 1.0;
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else if (dest[i] < 0.0)
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dest[i] = 0.0;
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}
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}
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static signalVector *rotateBurst(const BitVector &wBurst,
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|
int guardPeriodLength, int sps)
|
|
{
|
|
int burst_len;
|
|
signalVector *pulse, rotated;
|
|
signalVector::iterator itr;
|
|
|
|
pulse = GSMPulse1->empty;
|
|
burst_len = sps * (wBurst.size() + guardPeriodLength);
|
|
rotated = signalVector(burst_len);
|
|
itr = rotated.begin();
|
|
|
|
for (unsigned i = 0; i < wBurst.size(); i++) {
|
|
*itr = 2.0 * (wBurst[i] & 0x01) - 1.0;
|
|
itr += sps;
|
|
}
|
|
|
|
GMSKRotate(rotated, sps);
|
|
rotated.isReal(false);
|
|
|
|
/* Dummy filter operation */
|
|
return convolve(&rotated, pulse, NULL, START_ONLY);
|
|
}
|
|
|
|
static void rotateBurst2(signalVector &burst, double phase)
|
|
{
|
|
Complex<float> rot = Complex<float>(cos(phase), sin(phase));
|
|
|
|
for (size_t i = 0; i < burst.size(); i++)
|
|
burst[i] = burst[i] * rot;
|
|
}
|
|
|
|
/*
|
|
* Ignore the guard length argument in the GMSK modulator interface
|
|
* because it results in 624/628 sized bursts instead of the preferred
|
|
* burst length of 625. Only 4 SPS is supported.
|
|
*/
|
|
static signalVector *modulateBurstLaurent(const BitVector &bits)
|
|
{
|
|
int burst_len, sps = 4;
|
|
float phase;
|
|
signalVector *c0_pulse, *c1_pulse, *c0_shaped, *c1_shaped;
|
|
signalVector::iterator c0_itr, c1_itr;
|
|
|
|
c0_pulse = GSMPulse4->c0;
|
|
c1_pulse = GSMPulse4->c1;
|
|
|
|
if (bits.size() > 156)
|
|
return NULL;
|
|
|
|
burst_len = 625;
|
|
|
|
signalVector c0_burst(burst_len, c0_pulse->size());
|
|
c0_burst.isReal(true);
|
|
c0_itr = c0_burst.begin();
|
|
|
|
signalVector c1_burst(burst_len, c1_pulse->size());
|
|
c1_itr = c1_burst.begin();
|
|
|
|
/* Padded differential tail bits */
|
|
*c0_itr = 2.0 * (0x00 & 0x01) - 1.0;
|
|
c0_itr += sps;
|
|
|
|
/* Main burst bits */
|
|
for (unsigned i = 0; i < bits.size(); i++) {
|
|
*c0_itr = 2.0 * (bits[i] & 0x01) - 1.0;
|
|
c0_itr += sps;
|
|
}
|
|
|
|
/* Padded differential tail bits */
|
|
*c0_itr = 2.0 * (0x00 & 0x01) - 1.0;
|
|
|
|
/* Generate C0 phase coefficients */
|
|
GMSKRotate(c0_burst, sps);
|
|
c0_burst.isReal(false);
|
|
|
|
c0_itr = c0_burst.begin();
|
|
c0_itr += sps * 2;
|
|
c1_itr += sps * 2;
|
|
|
|
/* Start magic */
|
|
phase = 2.0 * ((0x01 & 0x01) ^ (0x01 & 0x01)) - 1.0;
|
|
*c1_itr = *c0_itr * Complex<float>(0, phase);
|
|
c0_itr += sps;
|
|
c1_itr += sps;
|
|
|
|
/* Generate C1 phase coefficients */
|
|
for (unsigned i = 2; i < bits.size(); i++) {
|
|
phase = 2.0 * ((bits[i - 1] & 0x01) ^ (bits[i - 2] & 0x01)) - 1.0;
|
|
*c1_itr = *c0_itr * Complex<float>(0, phase);
|
|
|
|
c0_itr += sps;
|
|
c1_itr += sps;
|
|
}
|
|
|
|
/* End magic */
|
|
int i = bits.size();
|
|
phase = 2.0 * ((bits[i-1] & 0x01) ^ (bits[i-2] & 0x01)) - 1.0;
|
|
*c1_itr = *c0_itr * Complex<float>(0, phase);
|
|
|
|
/* Primary (C0) and secondary (C1) pulse shaping */
|
|
c0_shaped = convolve(&c0_burst, c0_pulse, NULL, START_ONLY);
|
|
c1_shaped = convolve(&c1_burst, c1_pulse, NULL, START_ONLY);
|
|
|
|
/* Sum shaped outputs into C0 */
|
|
c0_itr = c0_shaped->begin();
|
|
c1_itr = c1_shaped->begin();
|
|
for (unsigned i = 0; i < c0_shaped->size(); i++ )
|
|
*c0_itr++ += *c1_itr++;
|
|
|
|
delete c1_shaped;
|
|
return c0_shaped;
|
|
}
|
|
|
|
static signalVector *rotateEdgeBurst(const signalVector &symbols, int sps)
|
|
{
|
|
signalVector *burst;
|
|
signalVector::iterator burst_itr;
|
|
|
|
burst = new signalVector(symbols.size() * sps);
|
|
burst_itr = burst->begin();
|
|
|
|
for (size_t i = 0; i < symbols.size(); i++) {
|
|
float phase = i * 3.0f * M_PI / 8.0f;
|
|
Complex<float> rot = Complex<float>(cos(phase), sin(phase));
|
|
|
|
*burst_itr = symbols[i] * rot;
|
|
burst_itr += sps;
|
|
}
|
|
|
|
return burst;
|
|
}
|
|
|
|
static signalVector *derotateEdgeBurst(const signalVector &symbols, int sps)
|
|
{
|
|
signalVector *burst;
|
|
signalVector::iterator burst_itr;
|
|
|
|
if (symbols.size() % sps)
|
|
return NULL;
|
|
|
|
burst = new signalVector(symbols.size() / sps);
|
|
burst_itr = burst->begin();
|
|
|
|
for (size_t i = 0; i < burst->size(); i++) {
|
|
float phase = (float) (i % 16) * 3.0f * M_PI / 8.0f;
|
|
Complex<float> rot = Complex<float>(cosf(phase), -sinf(phase));
|
|
|
|
*burst_itr = symbols[sps * i] * rot;
|
|
burst_itr++;
|
|
}
|
|
|
|
return burst;
|
|
}
|
|
|
|
static signalVector *mapEdgeSymbols(const BitVector &bits)
|
|
{
|
|
if (bits.size() % 3)
|
|
return NULL;
|
|
|
|
signalVector *symbols = new signalVector(bits.size() / 3);
|
|
|
|
for (size_t i = 0; i < symbols->size(); i++) {
|
|
unsigned index = (((unsigned) bits[3 * i + 0] & 0x01) << 0) |
|
|
(((unsigned) bits[3 * i + 1] & 0x01) << 1) |
|
|
(((unsigned) bits[3 * i + 2] & 0x01) << 2);
|
|
|
|
(*symbols)[i] = psk8_table[index];
|
|
}
|
|
|
|
return symbols;
|
|
}
|
|
|
|
/*
|
|
* EDGE 8-PSK rotate and pulse shape
|
|
*
|
|
* Delay the EDGE downlink bursts by one symbol in order to match GMSK pulse
|
|
* shaping group delay. The difference in group delay arises from the dual
|
|
* pulse filter combination of the GMSK Laurent representation whereas 8-PSK
|
|
* uses a single pulse linear filter.
|
|
*/
|
|
static signalVector *shapeEdgeBurst(const signalVector &symbols)
|
|
{
|
|
size_t nsyms, nsamps = 625, sps = 4;
|
|
signalVector::iterator burst_itr;
|
|
|
|
nsyms = symbols.size();
|
|
|
|
if (nsyms * sps > nsamps)
|
|
nsyms = 156;
|
|
|
|
signalVector burst(nsamps, GSMPulse4->c0->size());
|
|
|
|
/* Delay burst by 1 symbol */
|
|
burst_itr = burst.begin() + sps;
|
|
for (size_t i = 0; i < nsyms; i++) {
|
|
float phase = i * 3.0f * M_PI / 8.0f;
|
|
Complex<float> rot = Complex<float>(cos(phase), sin(phase));
|
|
|
|
*burst_itr = symbols[i] * rot;
|
|
burst_itr += sps;
|
|
}
|
|
|
|
/* Single Gaussian pulse approximation shaping */
|
|
return convolve(&burst, GSMPulse4->c0, NULL, START_ONLY);
|
|
}
|
|
|
|
/*
|
|
* Generate a random GSM normal burst.
|
|
*/
|
|
signalVector *genRandNormalBurst(int tsc, int sps, int tn)
|
|
{
|
|
if ((tsc < 0) || (tsc > 7) || (tn < 0) || (tn > 7))
|
|
return NULL;
|
|
if ((sps != 1) && (sps != 4))
|
|
return NULL;
|
|
|
|
int i = 0;
|
|
BitVector bits(148);
|
|
|
|
/* Tail bits */
|
|
for (; i < 3; i++)
|
|
bits[i] = 0;
|
|
|
|
/* Random bits */
|
|
for (; i < 60; i++)
|
|
bits[i] = rand() % 2;
|
|
|
|
/* Stealing bit */
|
|
bits[i++] = 0;
|
|
|
|
/* Training sequence */
|
|
for (int n = 0; i < 87; i++, n++)
|
|
bits[i] = gTrainingSequence[tsc][n];
|
|
|
|
/* Stealing bit */
|
|
bits[i++] = 0;
|
|
|
|
/* Random bits */
|
|
for (; i < 145; i++)
|
|
bits[i] = rand() % 2;
|
|
|
|
/* Tail bits */
|
|
for (; i < 148; i++)
|
|
bits[i] = 0;
|
|
|
|
int guard = 8 + !(tn % 4);
|
|
return modulateBurst(bits, guard, sps);
|
|
}
|
|
|
|
/*
|
|
* Generate a random GSM access burst.
|
|
*/
|
|
signalVector *genRandAccessBurst(int delay, int sps, int tn)
|
|
{
|
|
if ((tn < 0) || (tn > 7))
|
|
return NULL;
|
|
if ((sps != 1) && (sps != 4))
|
|
return NULL;
|
|
if (delay > 68)
|
|
return NULL;
|
|
|
|
int i = 0;
|
|
BitVector bits(88 + delay);
|
|
|
|
/* delay */
|
|
for (; i < delay; i++)
|
|
bits[i] = 0;
|
|
|
|
/* head and synch bits */
|
|
for (int n = 0; i < 49+delay; i++, n++)
|
|
bits[i] = gRACHBurst[n];
|
|
|
|
/* Random bits */
|
|
for (; i < 85+delay; i++)
|
|
bits[i] = rand() % 2;
|
|
|
|
/* Tail bits */
|
|
for (; i < 88+delay; i++)
|
|
bits[i] = 0;
|
|
|
|
int guard = 68-delay + !(tn % 4);
|
|
return modulateBurst(bits, guard, sps);
|
|
}
|
|
|
|
signalVector *generateEmptyBurst(int sps, int tn)
|
|
{
|
|
if ((tn < 0) || (tn > 7))
|
|
return NULL;
|
|
|
|
if (sps == 4)
|
|
return new signalVector(625);
|
|
else if (sps == 1)
|
|
return new signalVector(148 + 8 + !(tn % 4));
|
|
else
|
|
return NULL;
|
|
}
|
|
|
|
signalVector *generateDummyBurst(int sps, int tn)
|
|
{
|
|
if (((sps != 1) && (sps != 4)) || (tn < 0) || (tn > 7))
|
|
return NULL;
|
|
|
|
return modulateBurst(gDummyBurst, 8 + !(tn % 4), sps);
|
|
}
|
|
|
|
/*
|
|
* Generate a random 8-PSK EDGE burst. Only 4 SPS is supported with
|
|
* the returned burst being 625 samples in length.
|
|
*/
|
|
signalVector *generateEdgeBurst(int tsc)
|
|
{
|
|
int tail = 9 / 3;
|
|
int data = 174 / 3;
|
|
int train = 78 / 3;
|
|
|
|
if ((tsc < 0) || (tsc > 7))
|
|
return NULL;
|
|
|
|
signalVector burst(148);
|
|
const BitVector *midamble = &gEdgeTrainingSequence[tsc];
|
|
|
|
/* Tail */
|
|
int n, i = 0;
|
|
for (; i < tail; i++)
|
|
burst[i] = psk8_table[7];
|
|
|
|
/* Body */
|
|
for (; i < tail + data; i++)
|
|
burst[i] = psk8_table[rand() % 8];
|
|
|
|
/* TSC */
|
|
for (n = 0; i < tail + data + train; i++, n++) {
|
|
unsigned index = (((unsigned) (*midamble)[3 * n + 0] & 0x01) << 0) |
|
|
(((unsigned) (*midamble)[3 * n + 1] & 0x01) << 1) |
|
|
(((unsigned) (*midamble)[3 * n + 2] & 0x01) << 2);
|
|
|
|
burst[i] = psk8_table[index];
|
|
}
|
|
|
|
/* Body */
|
|
for (; i < tail + data + train + data; i++)
|
|
burst[i] = psk8_table[rand() % 8];
|
|
|
|
/* Tail */
|
|
for (; i < tail + data + train + data + tail; i++)
|
|
burst[i] = psk8_table[7];
|
|
|
|
return shapeEdgeBurst(burst);
|
|
}
|
|
|
|
/*
|
|
* Modulate 8-PSK burst. When empty pulse shaping (rotation only)
|
|
* is enabled, the output vector length will be bit sequence length
|
|
* times the SPS value. When pulse shaping is enabled, the output
|
|
* vector length is fixed at 625 samples (156.25 symbols at 4 SPS).
|
|
* Pulse shaped bit sequences that go beyond one burst are truncated.
|
|
* Pulse shaping at anything but 4 SPS is not supported.
|
|
*/
|
|
signalVector *modulateEdgeBurst(const BitVector &bits,
|
|
int sps, bool empty)
|
|
{
|
|
signalVector *shape, *burst;
|
|
|
|
if ((sps != 4) && !empty)
|
|
return NULL;
|
|
|
|
burst = mapEdgeSymbols(bits);
|
|
if (!burst)
|
|
return NULL;
|
|
|
|
if (empty)
|
|
shape = rotateEdgeBurst(*burst, sps);
|
|
else
|
|
shape = shapeEdgeBurst(*burst);
|
|
|
|
delete burst;
|
|
return shape;
|
|
}
|
|
|
|
static signalVector *modulateBurstBasic(const BitVector &bits,
|
|
int guard_len, int sps)
|
|
{
|
|
int burst_len;
|
|
signalVector *pulse;
|
|
signalVector::iterator burst_itr;
|
|
|
|
if (sps == 1)
|
|
pulse = GSMPulse1->c0;
|
|
else
|
|
pulse = GSMPulse4->c0;
|
|
|
|
burst_len = sps * (bits.size() + guard_len);
|
|
|
|
signalVector burst(burst_len, pulse->size());
|
|
burst.isReal(true);
|
|
burst_itr = burst.begin();
|
|
|
|
/* Raw bits are not differentially encoded */
|
|
for (unsigned i = 0; i < bits.size(); i++) {
|
|
*burst_itr = 2.0 * (bits[i] & 0x01) - 1.0;
|
|
burst_itr += sps;
|
|
}
|
|
|
|
GMSKRotate(burst, sps);
|
|
burst.isReal(false);
|
|
|
|
/* Single Gaussian pulse approximation shaping */
|
|
return convolve(&burst, pulse, NULL, START_ONLY);
|
|
}
|
|
|
|
/* Assume input bits are not differentially encoded */
|
|
signalVector *modulateBurst(const BitVector &wBurst, int guardPeriodLength,
|
|
int sps, bool emptyPulse)
|
|
{
|
|
if (emptyPulse)
|
|
return rotateBurst(wBurst, guardPeriodLength, sps);
|
|
else if (sps == 4)
|
|
return modulateBurstLaurent(wBurst);
|
|
else
|
|
return modulateBurstBasic(wBurst, guardPeriodLength, sps);
|
|
}
|
|
|
|
static void generateSincTable()
|
|
{
|
|
for (int i = 0; i < TABLESIZE; i++) {
|
|
auto x = (double) i / TABLESIZE * 8 * M_PI;
|
|
auto y = sin(x) / x;
|
|
sincTable[i] = std::isnan(y) ? 1.0 : y;
|
|
}
|
|
}
|
|
|
|
static float sinc(float x)
|
|
{
|
|
if (fabs(x) >= 8 * M_PI)
|
|
return 0.0;
|
|
|
|
int index = (int) floorf(fabs(x) / (8 * M_PI) * TABLESIZE);
|
|
|
|
return sincTable[index];
|
|
}
|
|
|
|
/*
|
|
* Create fractional delay filterbank with Blackman-harris windowed
|
|
* sinc function generator. The number of filters generated is specified
|
|
* by the DELAYFILTS value.
|
|
*/
|
|
static void generateDelayFilters()
|
|
{
|
|
int h_len = 20;
|
|
complex *data;
|
|
signalVector *h;
|
|
signalVector::iterator itr;
|
|
|
|
float k, sum;
|
|
float a0 = 0.35875;
|
|
float a1 = 0.48829;
|
|
float a2 = 0.14128;
|
|
float a3 = 0.01168;
|
|
|
|
for (int i = 0; i < DELAYFILTS; i++) {
|
|
data = (complex *) convolve_h_alloc(h_len);
|
|
h = new signalVector(data, 0, h_len, convolve_h_alloc, free);
|
|
h->setAligned(true);
|
|
h->isReal(true);
|
|
|
|
sum = 0.0;
|
|
itr = h->end();
|
|
for (int n = 0; n < h_len; n++) {
|
|
k = (float) n;
|
|
*--itr = (complex) sinc(M_PI_F *
|
|
(k - (float) h_len / 2.0 - (float) i / DELAYFILTS));
|
|
*itr *= a0 -
|
|
a1 * cos(2 * M_PI * n / (h_len - 1)) +
|
|
a2 * cos(4 * M_PI * n / (h_len - 1)) -
|
|
a3 * cos(6 * M_PI * n / (h_len - 1));
|
|
|
|
sum += itr->real();
|
|
}
|
|
|
|
itr = h->begin();
|
|
for (int n = 0; n < h_len; n++)
|
|
*itr++ /= sum;
|
|
|
|
delayFilters[i] = h;
|
|
}
|
|
}
|
|
|
|
signalVector *delayVector(const signalVector *in, signalVector *out, float delay)
|
|
{
|
|
int whole, index;
|
|
float frac;
|
|
signalVector *h, *shift, *fshift = NULL;
|
|
|
|
whole = floor(delay);
|
|
frac = delay - whole;
|
|
|
|
/* Sinc interpolated fractional shift (if allowable) */
|
|
if (fabs(frac) > 1e-2) {
|
|
index = floorf(frac * (float) DELAYFILTS);
|
|
h = delayFilters[index];
|
|
|
|
fshift = convolve(in, h, NULL, NO_DELAY);
|
|
if (!fshift)
|
|
return NULL;
|
|
}
|
|
|
|
if (!fshift)
|
|
shift = new signalVector(*in);
|
|
else
|
|
shift = fshift;
|
|
|
|
/* Integer sample shift */
|
|
if (whole < 0) {
|
|
whole = -whole;
|
|
signalVector::iterator wBurstItr = shift->begin();
|
|
signalVector::iterator shiftedItr = shift->begin() + whole;
|
|
|
|
while (shiftedItr < shift->end())
|
|
*wBurstItr++ = *shiftedItr++;
|
|
|
|
while (wBurstItr < shift->end())
|
|
*wBurstItr++ = 0.0;
|
|
} else if (whole >= 0) {
|
|
signalVector::iterator wBurstItr = shift->end() - 1;
|
|
signalVector::iterator shiftedItr = shift->end() - 1 - whole;
|
|
|
|
while (shiftedItr >= shift->begin())
|
|
*wBurstItr-- = *shiftedItr--;
|
|
|
|
while (wBurstItr >= shift->begin())
|
|
*wBurstItr-- = 0.0;
|
|
}
|
|
|
|
if (!out)
|
|
return shift;
|
|
|
|
out->clone(*shift);
|
|
delete shift;
|
|
return out;
|
|
}
|
|
|
|
static complex interpolatePoint(const signalVector &inSig, float ix)
|
|
{
|
|
int start = (int) (floor(ix) - 10);
|
|
if (start < 0) start = 0;
|
|
int end = (int) (floor(ix) + 11);
|
|
if ((unsigned) end > inSig.size()-1) end = inSig.size()-1;
|
|
|
|
complex pVal = 0.0;
|
|
if (!inSig.isReal()) {
|
|
for (int i = start; i < end; i++)
|
|
pVal += inSig[i] * sinc(M_PI_F*(i-ix));
|
|
}
|
|
else {
|
|
for (int i = start; i < end; i++)
|
|
pVal += inSig[i].real() * sinc(M_PI_F*(i-ix));
|
|
}
|
|
|
|
return pVal;
|
|
}
|
|
|
|
static complex fastPeakDetect(const signalVector &rxBurst, float *index)
|
|
{
|
|
float val, max = 0.0f;
|
|
complex amp;
|
|
int _index = -1;
|
|
|
|
for (size_t i = 0; i < rxBurst.size(); i++) {
|
|
val = rxBurst[i].norm2();
|
|
if (val > max) {
|
|
max = val;
|
|
_index = i;
|
|
amp = rxBurst[i];
|
|
}
|
|
}
|
|
|
|
if (index)
|
|
*index = (float) _index;
|
|
|
|
return amp;
|
|
}
|
|
|
|
static complex peakDetect(const signalVector &rxBurst,
|
|
float *peakIndex, float *avgPwr)
|
|
{
|
|
complex maxVal = 0.0;
|
|
float maxIndex = -1;
|
|
float sumPower = 0.0;
|
|
|
|
for (unsigned int i = 0; i < rxBurst.size(); i++) {
|
|
float samplePower = rxBurst[i].norm2();
|
|
if (samplePower > maxVal.real()) {
|
|
maxVal = samplePower;
|
|
maxIndex = i;
|
|
}
|
|
sumPower += samplePower;
|
|
}
|
|
|
|
// interpolate around the peak
|
|
// to save computation, we'll use early-late balancing
|
|
float earlyIndex = maxIndex-1;
|
|
float lateIndex = maxIndex+1;
|
|
|
|
float incr = 0.5;
|
|
while (incr > 1.0/1024.0) {
|
|
complex earlyP = interpolatePoint(rxBurst,earlyIndex);
|
|
complex lateP = interpolatePoint(rxBurst,lateIndex);
|
|
if (earlyP < lateP)
|
|
earlyIndex += incr;
|
|
else if (earlyP > lateP)
|
|
earlyIndex -= incr;
|
|
else break;
|
|
incr /= 2.0;
|
|
lateIndex = earlyIndex + 2.0;
|
|
}
|
|
|
|
maxIndex = earlyIndex + 1.0;
|
|
maxVal = interpolatePoint(rxBurst,maxIndex);
|
|
|
|
if (peakIndex!=NULL)
|
|
*peakIndex = maxIndex;
|
|
|
|
if (avgPwr!=NULL)
|
|
*avgPwr = (sumPower-maxVal.norm2()) / (rxBurst.size()-1);
|
|
|
|
return maxVal;
|
|
|
|
}
|
|
|
|
void scaleVector(signalVector &x,
|
|
complex scale)
|
|
{
|
|
#ifdef HAVE_NEON
|
|
int len = x.size();
|
|
|
|
scale_complex((float *) x.begin(),
|
|
(float *) x.begin(),
|
|
(float *) &scale, len);
|
|
#else
|
|
signalVector::iterator xP = x.begin();
|
|
signalVector::iterator xPEnd = x.end();
|
|
if (!x.isReal()) {
|
|
while (xP < xPEnd) {
|
|
*xP = *xP * scale;
|
|
xP++;
|
|
}
|
|
}
|
|
else {
|
|
while (xP < xPEnd) {
|
|
*xP = xP->real() * scale;
|
|
xP++;
|
|
}
|
|
}
|
|
#endif
|
|
}
|
|
|
|
/** in-place conjugation */
|
|
static void conjugateVector(signalVector &x)
|
|
{
|
|
if (x.isReal()) return;
|
|
signalVector::iterator xP = x.begin();
|
|
signalVector::iterator xPEnd = x.end();
|
|
while (xP < xPEnd) {
|
|
*xP = xP->conj();
|
|
xP++;
|
|
}
|
|
}
|
|
|
|
static bool generateMidamble(int sps, int tsc)
|
|
{
|
|
bool status = true;
|
|
float toa;
|
|
complex *data = NULL;
|
|
signalVector *autocorr = NULL, *midamble = NULL;
|
|
signalVector *midMidamble = NULL, *_midMidamble = NULL;
|
|
|
|
if ((tsc < 0) || (tsc > 7))
|
|
return false;
|
|
|
|
delete gMidambles[tsc];
|
|
|
|
/* Use middle 16 bits of each TSC. Correlation sequence is not pulse shaped */
|
|
midMidamble = modulateBurst(gTrainingSequence[tsc].segment(5,16), 0, sps, true);
|
|
if (!midMidamble)
|
|
return false;
|
|
|
|
/* Simulated receive sequence is pulse shaped */
|
|
midamble = modulateBurst(gTrainingSequence[tsc], 0, sps, false);
|
|
if (!midamble) {
|
|
status = false;
|
|
goto release;
|
|
}
|
|
|
|
// NOTE: Because ideal TSC 16-bit midamble is 66 symbols into burst,
|
|
// the ideal TSC has an + 180 degree phase shift,
|
|
// due to the pi/2 frequency shift, that
|
|
// needs to be accounted for.
|
|
// 26-midamble is 61 symbols into burst, has +90 degree phase shift.
|
|
scaleVector(*midMidamble, complex(-1.0, 0.0));
|
|
scaleVector(*midamble, complex(0.0, 1.0));
|
|
|
|
conjugateVector(*midMidamble);
|
|
|
|
/* For SSE alignment, reallocate the midamble sequence on 16-byte boundary */
|
|
data = (complex *) convolve_h_alloc(midMidamble->size());
|
|
_midMidamble = new signalVector(data, 0, midMidamble->size(), convolve_h_alloc, free);
|
|
_midMidamble->setAligned(true);
|
|
midMidamble->copyTo(*_midMidamble);
|
|
|
|
autocorr = convolve(midamble, _midMidamble, NULL, NO_DELAY);
|
|
if (!autocorr) {
|
|
status = false;
|
|
goto release;
|
|
}
|
|
|
|
gMidambles[tsc] = new CorrelationSequence;
|
|
gMidambles[tsc]->sequence = _midMidamble;
|
|
gMidambles[tsc]->gain = peakDetect(*autocorr, &toa, NULL);
|
|
|
|
/* For 1 sps only
|
|
* (Half of correlation length - 1) + midpoint of pulse shape + remainder
|
|
* 13.5 = (16 / 2 - 1) + 1.5 + (26 - 10) / 2
|
|
*/
|
|
if (sps == 1)
|
|
gMidambles[tsc]->toa = toa - 13.5;
|
|
else
|
|
gMidambles[tsc]->toa = 0;
|
|
|
|
release:
|
|
delete autocorr;
|
|
delete midamble;
|
|
delete midMidamble;
|
|
|
|
if (!status) {
|
|
delete _midMidamble;
|
|
free(data);
|
|
gMidambles[tsc] = NULL;
|
|
}
|
|
|
|
return status;
|
|
}
|
|
|
|
static CorrelationSequence *generateEdgeMidamble(int tsc)
|
|
{
|
|
complex *data = NULL;
|
|
signalVector *midamble = NULL, *_midamble = NULL;
|
|
CorrelationSequence *seq;
|
|
|
|
if ((tsc < 0) || (tsc > 7))
|
|
return NULL;
|
|
|
|
/* Use middle 48 bits of each TSC. Correlation sequence is not pulse shaped */
|
|
const BitVector *bits = &gEdgeTrainingSequence[tsc];
|
|
midamble = modulateEdgeBurst(bits->segment(15, 48), 1, true);
|
|
if (!midamble)
|
|
return NULL;
|
|
|
|
conjugateVector(*midamble);
|
|
|
|
data = (complex *) convolve_h_alloc(midamble->size());
|
|
_midamble = new signalVector(data, 0, midamble->size(), convolve_h_alloc, free);
|
|
_midamble->setAligned(true);
|
|
midamble->copyTo(*_midamble);
|
|
|
|
/* Channel gain is an empirically measured value */
|
|
seq = new CorrelationSequence;
|
|
seq->sequence = _midamble;
|
|
seq->gain = Complex<float>(-19.6432, 19.5006) / 1.18;
|
|
seq->toa = 0;
|
|
|
|
delete midamble;
|
|
|
|
return seq;
|
|
}
|
|
|
|
static bool generateRACHSequence(CorrelationSequence **seq, const BitVector &bv, int sps)
|
|
{
|
|
bool status = true;
|
|
float toa;
|
|
complex *data = NULL;
|
|
signalVector *autocorr = NULL;
|
|
signalVector *seq0 = NULL, *seq1 = NULL, *_seq1 = NULL;
|
|
|
|
if (*seq != NULL)
|
|
delete *seq;
|
|
|
|
seq0 = modulateBurst(bv, 0, sps, false);
|
|
if (!seq0)
|
|
return false;
|
|
|
|
seq1 = modulateBurst(bv.segment(0, 40), 0, sps, true);
|
|
if (!seq1) {
|
|
status = false;
|
|
goto release;
|
|
}
|
|
|
|
conjugateVector(*seq1);
|
|
|
|
/* For SSE alignment, reallocate the midamble sequence on 16-byte boundary */
|
|
data = (complex *) convolve_h_alloc(seq1->size());
|
|
_seq1 = new signalVector(data, 0, seq1->size(), convolve_h_alloc, free);
|
|
_seq1->setAligned(true);
|
|
seq1->copyTo(*_seq1);
|
|
|
|
autocorr = convolve(seq0, _seq1, autocorr, NO_DELAY);
|
|
if (!autocorr) {
|
|
status = false;
|
|
goto release;
|
|
}
|
|
|
|
*seq = new CorrelationSequence;
|
|
(*seq)->sequence = _seq1;
|
|
(*seq)->gain = peakDetect(*autocorr, &toa, NULL);
|
|
|
|
/* For 1 sps only
|
|
* (Half of correlation length - 1) + midpoint of pulse shaping filer
|
|
* 20.5 = (40 / 2 - 1) + 1.5
|
|
*/
|
|
if (sps == 1)
|
|
(*seq)->toa = toa - 20.5;
|
|
else
|
|
(*seq)->toa = 0.0;
|
|
|
|
release:
|
|
delete autocorr;
|
|
delete seq0;
|
|
delete seq1;
|
|
|
|
if (!status) {
|
|
delete _seq1;
|
|
free(data);
|
|
*seq = NULL;
|
|
}
|
|
|
|
return status;
|
|
}
|
|
|
|
/*
|
|
* Peak-to-average computation +/- range from peak in symbols
|
|
*/
|
|
#define COMPUTE_PEAK_MIN 2
|
|
#define COMPUTE_PEAK_MAX 5
|
|
|
|
/*
|
|
* Minimum number of values needed to compute peak-to-average
|
|
*/
|
|
#define COMPUTE_PEAK_CNT 5
|
|
|
|
static float computePeakRatio(signalVector *corr,
|
|
int sps, float toa, complex amp)
|
|
{
|
|
int num = 0;
|
|
complex *peak;
|
|
float rms, avg = 0.0;
|
|
|
|
/* Check for bogus results */
|
|
if ((toa < 0.0) || (toa > corr->size()))
|
|
return 0.0;
|
|
|
|
peak = corr->begin() + (int) rint(toa);
|
|
|
|
for (int i = COMPUTE_PEAK_MIN * sps; i <= COMPUTE_PEAK_MAX * sps; i++) {
|
|
if (peak - i >= corr->begin()) {
|
|
avg += (peak - i)->norm2();
|
|
num++;
|
|
}
|
|
if (peak + i < corr->end()) {
|
|
avg += (peak + i)->norm2();
|
|
num++;
|
|
}
|
|
}
|
|
|
|
if (num < COMPUTE_PEAK_CNT)
|
|
return 0.0;
|
|
|
|
rms = sqrtf(avg / (float) num) + 0.00001;
|
|
|
|
return (amp.abs()) / rms;
|
|
}
|
|
|
|
float energyDetect(const signalVector &rxBurst, unsigned windowLength)
|
|
{
|
|
|
|
signalVector::const_iterator windowItr = rxBurst.begin(); //+rxBurst.size()/2 - 5*windowLength/2;
|
|
float energy = 0.0;
|
|
if (windowLength == 0) return 0.0;
|
|
if (windowLength > rxBurst.size()) windowLength = rxBurst.size();
|
|
for (unsigned i = 0; i < windowLength; i++) {
|
|
energy += windowItr->norm2();
|
|
windowItr+=4;
|
|
}
|
|
return energy/windowLength;
|
|
}
|
|
|
|
static signalVector *downsampleBurst(const signalVector &burst)
|
|
{
|
|
signalVector in(DOWNSAMPLE_IN_LEN, dnsampler->len());
|
|
signalVector *out = new signalVector(DOWNSAMPLE_OUT_LEN);
|
|
burst.copyToSegment(in, 0, DOWNSAMPLE_IN_LEN);
|
|
|
|
if (dnsampler->rotate((float *) in.begin(), DOWNSAMPLE_IN_LEN,
|
|
(float *) out->begin(), DOWNSAMPLE_OUT_LEN) < 0) {
|
|
delete out;
|
|
out = NULL;
|
|
}
|
|
|
|
return out;
|
|
};
|
|
|
|
/*
|
|
* Computes C/I (Carrier-to-Interference ratio) in dB (deciBels).
|
|
* It is computed from the training sequence of each received burst,
|
|
* by comparing the "ideal" training sequence with the actual one.
|
|
*/
|
|
static float computeCI(const signalVector *burst, CorrelationSequence *sync,
|
|
float toa, int start, complex xcorr)
|
|
{
|
|
float S, C;
|
|
int ps;
|
|
|
|
/* Integer position where the sequence starts */
|
|
ps = start + 1 - sync->sequence->size() + (int)roundf(toa);
|
|
|
|
/* Estimate Signal power */
|
|
S = 0.0f;
|
|
for (int i=0, j=ps; i<(int)sync->sequence->size(); i++,j++)
|
|
S += (*burst)[j].norm2();
|
|
S /= sync->sequence->size();
|
|
|
|
/* Esimate Carrier power */
|
|
C = xcorr.norm2() / ((sync->sequence->size() - 1) * sync->gain.abs());
|
|
|
|
/* Interference = Signal - Carrier, so C/I = C / (S - C) */
|
|
return 3.0103f * log2f(C / (S - C));
|
|
}
|
|
|
|
/*
|
|
* Detect a burst based on correlation and peak-to-average ratio
|
|
*
|
|
* For one sampler-per-symbol, perform fast peak detection (no interpolation)
|
|
* for initial gating. We do this because energy detection should be disabled.
|
|
* For higher oversampling values, we assume the energy detector is in place
|
|
* and we run full interpolating peak detection.
|
|
*/
|
|
static int detectBurst(const signalVector &burst,
|
|
signalVector &corr, CorrelationSequence *sync,
|
|
float thresh, int sps, int start, int len,
|
|
struct estim_burst_params *ebp)
|
|
{
|
|
const signalVector *corr_in;
|
|
signalVector *dec = NULL;
|
|
complex xcorr;
|
|
int rc = 1;
|
|
|
|
if (sps == 4) {
|
|
dec = downsampleBurst(burst);
|
|
corr_in = dec;
|
|
sps = 1;
|
|
} else {
|
|
corr_in = &burst;
|
|
}
|
|
|
|
/* Correlate */
|
|
if (!convolve(corr_in, sync->sequence, &corr,
|
|
CUSTOM, start, len)) {
|
|
rc = -1;
|
|
goto del_ret;
|
|
}
|
|
|
|
/* Running at the downsampled rate at this point */
|
|
sps = 1;
|
|
|
|
/* Peak detection - place restrictions at correlation edges */
|
|
ebp->amp = fastPeakDetect(corr, &ebp->toa);
|
|
|
|
if ((ebp->toa < 3 * sps) || (ebp->toa > len - 3 * sps)) {
|
|
rc = 0;
|
|
goto del_ret;
|
|
}
|
|
|
|
/* Peak-to-average ratio */
|
|
if (computePeakRatio(&corr, sps, ebp->toa, ebp->amp) < thresh) {
|
|
rc = 0;
|
|
goto del_ret;
|
|
}
|
|
|
|
/* Refine TOA and correlation value */
|
|
xcorr = peakDetect(corr, &ebp->toa, NULL);
|
|
|
|
/* Compute C/I */
|
|
ebp->ci = computeCI(corr_in, sync, ebp->toa, start, xcorr);
|
|
|
|
/* Normalize our channel gain */
|
|
ebp->amp = xcorr / sync->gain;
|
|
|
|
/* Compensate for residuate time lag */
|
|
ebp->toa = ebp->toa - sync->toa;
|
|
|
|
del_ret:
|
|
delete dec;
|
|
return rc;
|
|
}
|
|
|
|
static float maxAmplitude(const signalVector &burst)
|
|
{
|
|
float max = 0.0;
|
|
for (size_t i = 0; i < burst.size(); i++) {
|
|
if (fabs(burst[i].real()) > max)
|
|
max = fabs(burst[i].real());
|
|
if (fabs(burst[i].imag()) > max)
|
|
max = fabs(burst[i].imag());
|
|
}
|
|
|
|
return max;
|
|
}
|
|
|
|
/*
|
|
* RACH/Normal burst detection with clipping detection
|
|
*
|
|
* Correlation window parameters:
|
|
* target: Tail bits + burst length
|
|
* head: Search symbols before target
|
|
* tail: Search symbols after target
|
|
*/
|
|
static int detectGeneralBurst(const signalVector &rxBurst, float thresh, int sps,
|
|
int target, int head, int tail,
|
|
CorrelationSequence *sync,
|
|
struct estim_burst_params *ebp)
|
|
{
|
|
int rc, start, len;
|
|
bool clipping = false;
|
|
|
|
if ((sps != 1) && (sps != 4))
|
|
return -SIGERR_UNSUPPORTED;
|
|
|
|
// Detect potential clipping
|
|
// We still may be able to demod the burst, so we'll give it a try
|
|
// and only report clipping if we can't demod.
|
|
float maxAmpl = maxAmplitude(rxBurst);
|
|
if (maxAmpl > CLIP_THRESH) {
|
|
LOG(DEBUG) << "max burst amplitude: " << maxAmpl << " is above the clipping threshold: " << CLIP_THRESH << std::endl;
|
|
clipping = true;
|
|
}
|
|
|
|
start = target - head - 1;
|
|
len = head + tail;
|
|
signalVector corr(len);
|
|
|
|
rc = detectBurst(rxBurst, corr, sync,
|
|
thresh, sps, start, len, ebp);
|
|
if (rc < 0) {
|
|
return -SIGERR_INTERNAL;
|
|
} else if (!rc) {
|
|
ebp->amp = 0.0f;
|
|
ebp->toa = 0.0f;
|
|
ebp->ci = 0.0f;
|
|
return clipping?-SIGERR_CLIP:SIGERR_NONE;
|
|
}
|
|
|
|
/* Subtract forward search bits from delay */
|
|
ebp->toa -= head;
|
|
|
|
return 1;
|
|
}
|
|
|
|
|
|
/*
|
|
* RACH burst detection
|
|
*
|
|
* Correlation window parameters:
|
|
* target: Tail bits + RACH length (reduced from 41 to a multiple of 4)
|
|
* head: Search 8 symbols before target
|
|
* tail: Search 8 symbols + maximum expected delay
|
|
*/
|
|
static int detectRACHBurst(const signalVector &burst, float threshold, int sps,
|
|
unsigned max_toa, bool ext, struct estim_burst_params *ebp)
|
|
{
|
|
int rc, target, head, tail;
|
|
int i, num_seq;
|
|
|
|
target = 8 + 40;
|
|
head = 8;
|
|
tail = 8 + max_toa;
|
|
num_seq = ext ? 3 : 1;
|
|
|
|
for (i = 0; i < num_seq; i++) {
|
|
rc = detectGeneralBurst(burst, threshold, sps, target, head, tail,
|
|
gRACHSequences[i], ebp);
|
|
if (rc > 0) {
|
|
ebp->tsc = i;
|
|
break;
|
|
}
|
|
}
|
|
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* Normal burst detection
|
|
*
|
|
* Correlation window parameters:
|
|
* target: Tail + data + mid-midamble + 1/2 remaining midamblebits
|
|
* head: Search 6 symbols before target
|
|
* tail: Search 6 symbols + maximum expected delay
|
|
*/
|
|
static int analyzeTrafficBurst(const signalVector &burst, unsigned tsc, float threshold,
|
|
int sps, unsigned max_toa, struct estim_burst_params *ebp)
|
|
{
|
|
int rc, target, head, tail;
|
|
CorrelationSequence *sync;
|
|
|
|
if (tsc > 7)
|
|
return -SIGERR_UNSUPPORTED;
|
|
|
|
target = 3 + 58 + 16 + 5;
|
|
head = 6;
|
|
tail = 6 + max_toa;
|
|
sync = gMidambles[tsc];
|
|
|
|
ebp->tsc = tsc;
|
|
rc = detectGeneralBurst(burst, threshold, sps, target, head, tail, sync, ebp);
|
|
return rc;
|
|
}
|
|
|
|
static int detectEdgeBurst(const signalVector &burst, unsigned tsc, float threshold,
|
|
int sps, unsigned max_toa, struct estim_burst_params *ebp)
|
|
{
|
|
int rc, target, head, tail;
|
|
CorrelationSequence *sync;
|
|
|
|
if (tsc > 7)
|
|
return -SIGERR_UNSUPPORTED;
|
|
|
|
target = 3 + 58 + 16 + 5;
|
|
head = 6;
|
|
tail = 6 + max_toa;
|
|
sync = gEdgeMidambles[tsc];
|
|
|
|
ebp->tsc = tsc;
|
|
rc = detectGeneralBurst(burst, threshold, sps,
|
|
target, head, tail, sync, ebp);
|
|
return rc;
|
|
}
|
|
|
|
int detectAnyBurst(const signalVector &burst, unsigned tsc, float threshold,
|
|
int sps, CorrType type, unsigned max_toa,
|
|
struct estim_burst_params *ebp)
|
|
{
|
|
int rc = 0;
|
|
|
|
switch (type) {
|
|
case EDGE:
|
|
rc = detectEdgeBurst(burst, tsc, threshold, sps, max_toa, ebp);
|
|
if (rc > 0)
|
|
break;
|
|
else
|
|
type = TSC;
|
|
case TSC:
|
|
rc = analyzeTrafficBurst(burst, tsc, threshold, sps, max_toa, ebp);
|
|
break;
|
|
case EXT_RACH:
|
|
case RACH:
|
|
rc = detectRACHBurst(burst, threshold, sps, max_toa, type == EXT_RACH, ebp);
|
|
break;
|
|
default:
|
|
LOG(ERR) << "Invalid correlation type";
|
|
}
|
|
|
|
if (rc > 0)
|
|
return type;
|
|
|
|
return rc;
|
|
}
|
|
|
|
/*
|
|
* Soft 8-PSK decoding using Manhattan distance metric
|
|
*/
|
|
static SoftVector *softSliceEdgeBurst(signalVector &burst)
|
|
{
|
|
size_t nsyms = 148;
|
|
|
|
if (burst.size() < nsyms)
|
|
return NULL;
|
|
|
|
signalVector::iterator itr;
|
|
SoftVector *bits = new SoftVector(nsyms * 3);
|
|
|
|
/*
|
|
* Bits 0 and 1 - First and second bits of the symbol respectively
|
|
*/
|
|
rotateBurst2(burst, -M_PI / 8.0);
|
|
itr = burst.begin();
|
|
for (size_t i = 0; i < nsyms; i++) {
|
|
(*bits)[3 * i + 0] = -itr->imag();
|
|
(*bits)[3 * i + 1] = itr->real();
|
|
itr++;
|
|
}
|
|
|
|
/*
|
|
* Bit 2 - Collapse symbols into quadrant 0 (positive X and Y).
|
|
* Decision area is then simplified to X=Y axis. Rotate again to
|
|
* place decision boundary on X-axis.
|
|
*/
|
|
itr = burst.begin();
|
|
for (size_t i = 0; i < burst.size(); i++) {
|
|
burst[i] = Complex<float>(fabs(itr->real()), fabs(itr->imag()));
|
|
itr++;
|
|
}
|
|
|
|
rotateBurst2(burst, -M_PI / 4.0);
|
|
itr = burst.begin();
|
|
for (size_t i = 0; i < nsyms; i++) {
|
|
(*bits)[3 * i + 2] = -itr->imag();
|
|
itr++;
|
|
}
|
|
|
|
signalVector soft(bits->size());
|
|
for (size_t i = 0; i < bits->size(); i++)
|
|
soft[i] = (*bits)[i];
|
|
|
|
return bits;
|
|
}
|
|
|
|
/*
|
|
* Convert signalVector to SoftVector by taking real part of the signal.
|
|
*/
|
|
static SoftVector *signalToSoftVector(signalVector *dec)
|
|
{
|
|
SoftVector *bits = new SoftVector(dec->size());
|
|
|
|
SoftVector::iterator bit_itr = bits->begin();
|
|
signalVector::iterator burst_itr = dec->begin();
|
|
|
|
for (; burst_itr < dec->end(); burst_itr++)
|
|
*bit_itr++ = burst_itr->real();
|
|
|
|
return bits;
|
|
}
|
|
|
|
/*
|
|
* Shared portion of GMSK and EDGE demodulators consisting of timing
|
|
* recovery and single tap channel correction. For 4 SPS (if activated),
|
|
* the output is downsampled prior to the 1 SPS modulation specific
|
|
* stages.
|
|
*/
|
|
static signalVector *demodCommon(const signalVector &burst, int sps,
|
|
complex chan, float toa)
|
|
{
|
|
signalVector *delay, *dec;
|
|
|
|
if ((sps != 1) && (sps != 4))
|
|
return NULL;
|
|
|
|
delay = delayVector(&burst, NULL, -toa * (float) sps);
|
|
scaleVector(*delay, (complex) 1.0 / chan);
|
|
|
|
if (sps == 1)
|
|
return delay;
|
|
|
|
dec = downsampleBurst(*delay);
|
|
|
|
delete delay;
|
|
return dec;
|
|
}
|
|
|
|
/*
|
|
* Demodulate GSMK burst. Prior to symbol rotation, operate at
|
|
* 4 SPS (if activated) to minimize distortion through the fractional
|
|
* delay filters. Symbol rotation and after always operates at 1 SPS.
|
|
*/
|
|
static SoftVector *demodGmskBurst(const signalVector &rxBurst,
|
|
int sps, complex channel, float TOA)
|
|
{
|
|
SoftVector *bits;
|
|
signalVector *dec;
|
|
|
|
dec = demodCommon(rxBurst, sps, channel, TOA);
|
|
if (!dec)
|
|
return NULL;
|
|
|
|
/* Shift up by a quarter of a frequency */
|
|
GMSKReverseRotate(*dec, 1);
|
|
/* Take real part of the signal */
|
|
bits = signalToSoftVector(dec);
|
|
delete dec;
|
|
|
|
return bits;
|
|
}
|
|
|
|
/*
|
|
* Demodulate an 8-PSK burst. Prior to symbol rotation, operate at
|
|
* 4 SPS (if activated) to minimize distortion through the fractional
|
|
* delay filters. Symbol rotation and after always operates at 1 SPS.
|
|
*
|
|
* Allow 1 SPS demodulation here, but note that other parts of the
|
|
* transceiver restrict EDGE operatoin to 4 SPS - 8-PSK distortion
|
|
* through the fractional delay filters at 1 SPS renders signal
|
|
* nearly unrecoverable.
|
|
*/
|
|
static SoftVector *demodEdgeBurst(const signalVector &burst,
|
|
int sps, complex chan, float toa)
|
|
{
|
|
SoftVector *bits;
|
|
signalVector *dec, *rot, *eq;
|
|
|
|
dec = demodCommon(burst, sps, chan, toa);
|
|
if (!dec)
|
|
return NULL;
|
|
|
|
/* Equalize and derotate */
|
|
eq = convolve(dec, GSMPulse4->c0_inv, NULL, NO_DELAY);
|
|
rot = derotateEdgeBurst(*eq, 1);
|
|
|
|
/* Soft slice and normalize */
|
|
bits = softSliceEdgeBurst(*rot);
|
|
|
|
delete dec;
|
|
delete eq;
|
|
delete rot;
|
|
|
|
return bits;
|
|
}
|
|
|
|
SoftVector *demodAnyBurst(const signalVector &burst, int sps, complex amp,
|
|
float toa, CorrType type)
|
|
{
|
|
if (type == EDGE)
|
|
return demodEdgeBurst(burst, sps, amp, toa);
|
|
else
|
|
return demodGmskBurst(burst, sps, amp, toa);
|
|
}
|
|
|
|
bool sigProcLibSetup()
|
|
{
|
|
generateSincTable();
|
|
initGMSKRotationTables();
|
|
|
|
GSMPulse1 = generateGSMPulse(1);
|
|
GSMPulse4 = generateGSMPulse(4);
|
|
|
|
generateRACHSequence(&gRACHSequences[0], gRACHSynchSequenceTS0, 1);
|
|
generateRACHSequence(&gRACHSequences[1], gRACHSynchSequenceTS1, 1);
|
|
generateRACHSequence(&gRACHSequences[2], gRACHSynchSequenceTS2, 1);
|
|
|
|
for (int tsc = 0; tsc < 8; tsc++) {
|
|
generateMidamble(1, tsc);
|
|
gEdgeMidambles[tsc] = generateEdgeMidamble(tsc);
|
|
}
|
|
|
|
generateDelayFilters();
|
|
|
|
dnsampler = new Resampler(1, 4);
|
|
if (!dnsampler->init()) {
|
|
LOG(ALERT) << "Rx resampler failed to initialize";
|
|
goto fail;
|
|
}
|
|
|
|
return true;
|
|
|
|
fail:
|
|
sigProcLibDestroy();
|
|
return false;
|
|
}
|