| /* |
| * Copyright 2008, 2011 Free Software Foundation, Inc. |
| * |
| * This software is distributed under the terms of the GNU Affero Public License. |
| * See the COPYING file in the main directory for details. |
| * |
| * This use of this software may be subject to additional restrictions. |
| * See the LEGAL file in the main directory for details. |
| |
| This program is free software: you can redistribute it and/or modify |
| it under the terms of the GNU Affero General Public License as published by |
| the Free Software Foundation, either version 3 of the License, or |
| (at your option) any later version. |
| |
| This program is distributed in the hope that it will be useful, |
| but WITHOUT ANY WARRANTY; without even the implied warranty of |
| MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| GNU Affero General Public License for more details. |
| |
| You should have received a copy of the GNU Affero General Public License |
| along with this program. If not, see <http://www.gnu.org/licenses/>. |
| |
| */ |
| |
| #ifdef HAVE_CONFIG_H |
| #include "config.h" |
| #endif |
| |
| #include "sigProcLib.h" |
| #include "GSMCommon.h" |
| #include "Logger.h" |
| #include "Resampler.h" |
| |
| extern "C" { |
| #include "convolve.h" |
| #include "scale.h" |
| #include "mult.h" |
| } |
| |
| using namespace GSM; |
| |
| #define TABLESIZE 1024 |
| #define DELAYFILTS 64 |
| |
| /* Clipping detection threshold */ |
| #define CLIP_THRESH 30000.0f |
| |
| /** Lookup tables for trigonometric approximation */ |
| static float sincTable[TABLESIZE+1]; // add 1 element for wrap around |
| |
| /** Constants */ |
| static const float M_PI_F = (float)M_PI; |
| |
| /* Precomputed rotation vectors */ |
| static signalVector *GMSKRotation4 = NULL; |
| static signalVector *GMSKReverseRotation4 = NULL; |
| static signalVector *GMSKRotation1 = NULL; |
| static signalVector *GMSKReverseRotation1 = NULL; |
| |
| /* Precomputed fractional delay filters */ |
| static signalVector *delayFilters[DELAYFILTS]; |
| |
| static const Complex<float> psk8_table[8] = { |
| Complex<float>(-0.70710678, 0.70710678), |
| Complex<float>( 0.0, -1.0), |
| Complex<float>( 0.0, 1.0), |
| Complex<float>( 0.70710678, -0.70710678), |
| Complex<float>(-1.0, 0.0), |
| Complex<float>(-0.70710678, -0.70710678), |
| Complex<float>( 0.70710678, 0.70710678), |
| Complex<float>( 1.0, 0.0), |
| }; |
| |
| /* Downsampling filterbank - 4 SPS to 1 SPS */ |
| #define DOWNSAMPLE_IN_LEN 624 |
| #define DOWNSAMPLE_OUT_LEN 156 |
| |
| static Resampler *dnsampler = NULL; |
| |
| /* |
| * RACH and midamble correlation waveforms. Store the buffer separately |
| * because we need to allocate it explicitly outside of the signal vector |
| * constructor. This is because C++ (prior to C++11) is unable to natively |
| * perform 16-byte memory alignment required by many SSE instructions. |
| */ |
| struct CorrelationSequence { |
| CorrelationSequence() : sequence(NULL) |
| { |
| } |
| |
| ~CorrelationSequence() |
| { |
| delete sequence; |
| } |
| |
| signalVector *sequence; |
| void *buffer; |
| float toa; |
| complex gain; |
| }; |
| |
| /* |
| * Gaussian and empty modulation pulses. Like the correlation sequences, |
| * store the runtime (Gaussian) buffer separately because of needed alignment |
| * for SSE instructions. |
| */ |
| struct PulseSequence { |
| PulseSequence() : c0(NULL), c1(NULL), c0_inv(NULL), empty(NULL) |
| { |
| } |
| |
| ~PulseSequence() |
| { |
| delete c0; |
| delete c1; |
| delete c0_inv; |
| delete empty; |
| } |
| |
| signalVector *c0; |
| signalVector *c1; |
| signalVector *c0_inv; |
| signalVector *empty; |
| }; |
| |
| static CorrelationSequence *gMidambles[] = {NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL}; |
| static CorrelationSequence *gEdgeMidambles[] = {NULL,NULL,NULL,NULL,NULL,NULL,NULL,NULL}; |
| static CorrelationSequence *gRACHSequences[] = {NULL,NULL,NULL}; |
| static PulseSequence *GSMPulse1 = NULL; |
| static PulseSequence *GSMPulse4 = NULL; |
| |
| void sigProcLibDestroy() |
| { |
| for (int i = 0; i < 8; i++) { |
| delete gMidambles[i]; |
| delete gEdgeMidambles[i]; |
| gMidambles[i] = NULL; |
| gEdgeMidambles[i] = NULL; |
| } |
| |
| for (int i = 0; i < DELAYFILTS; i++) { |
| delete delayFilters[i]; |
| delayFilters[i] = NULL; |
| } |
| |
| for (int i = 0; i < 3; i++) { |
| delete gRACHSequences[i]; |
| gRACHSequences[i] = NULL; |
| } |
| |
| delete GMSKRotation1; |
| delete GMSKReverseRotation1; |
| delete GMSKRotation4; |
| delete GMSKReverseRotation4; |
| delete GSMPulse1; |
| delete GSMPulse4; |
| delete dnsampler; |
| |
| GMSKRotation1 = NULL; |
| GMSKRotation4 = NULL; |
| GMSKReverseRotation4 = NULL; |
| GMSKReverseRotation1 = NULL; |
| GSMPulse1 = NULL; |
| GSMPulse4 = NULL; |
| } |
| |
| static float vectorNorm2(const signalVector &x) |
| { |
| signalVector::const_iterator xPtr = x.begin(); |
| float Energy = 0.0; |
| for (;xPtr != x.end();xPtr++) { |
| Energy += xPtr->norm2(); |
| } |
| return Energy; |
| } |
| |
| /* |
| * Initialize 4 sps and 1 sps rotation tables |
| */ |
| static void initGMSKRotationTables() |
| { |
| size_t len1 = 157, len4 = 625; |
| |
| GMSKRotation4 = new signalVector(len4); |
| GMSKReverseRotation4 = new signalVector(len4); |
| signalVector::iterator rotPtr = GMSKRotation4->begin(); |
| signalVector::iterator revPtr = GMSKReverseRotation4->begin(); |
| auto phase = 0.0; |
| while (rotPtr != GMSKRotation4->end()) { |
| *rotPtr++ = complex(cos(phase), sin(phase)); |
| *revPtr++ = complex(cos(-phase), sin(-phase)); |
| phase += M_PI / 2.0 / 4.0; |
| } |
| |
| GMSKRotation1 = new signalVector(len1); |
| GMSKReverseRotation1 = new signalVector(len1); |
| rotPtr = GMSKRotation1->begin(); |
| revPtr = GMSKReverseRotation1->begin(); |
| phase = 0.0; |
| while (rotPtr != GMSKRotation1->end()) { |
| *rotPtr++ = complex(cos(phase), sin(phase)); |
| *revPtr++ = complex(cos(-phase), sin(-phase)); |
| phase += M_PI / 2.0; |
| } |
| } |
| |
| static void GMSKRotate(signalVector &x, int sps) |
| { |
| #if HAVE_NEON |
| size_t len; |
| signalVector *a, *b, *out; |
| |
| a = &x; |
| out = &x; |
| len = out->size(); |
| |
| if (len == 157) |
| len--; |
| |
| if (sps == 1) |
| b = GMSKRotation1; |
| else |
| b = GMSKRotation4; |
| |
| mul_complex((float *) out->begin(), |
| (float *) a->begin(), |
| (float *) b->begin(), len); |
| #else |
| signalVector::iterator rotPtr, xPtr = x.begin(); |
| |
| if (sps == 1) |
| rotPtr = GMSKRotation1->begin(); |
| else |
| rotPtr = GMSKRotation4->begin(); |
| |
| if (x.isReal()) { |
| while (xPtr < x.end()) { |
| *xPtr = *rotPtr++ * (xPtr->real()); |
| xPtr++; |
| } |
| } |
| else { |
| while (xPtr < x.end()) { |
| *xPtr = *rotPtr++ * (*xPtr); |
| xPtr++; |
| } |
| } |
| #endif |
| } |
| |
| static bool GMSKReverseRotate(signalVector &x, int sps) |
| { |
| signalVector::iterator rotPtr, xPtr= x.begin(); |
| |
| if (sps == 1) |
| rotPtr = GMSKReverseRotation1->begin(); |
| else if (sps == 4) |
| rotPtr = GMSKReverseRotation4->begin(); |
| else |
| return false; |
| |
| if (x.isReal()) { |
| while (xPtr < x.end()) { |
| *xPtr = *rotPtr++ * (xPtr->real()); |
| xPtr++; |
| } |
| } |
| else { |
| while (xPtr < x.end()) { |
| *xPtr = *rotPtr++ * (*xPtr); |
| xPtr++; |
| } |
| } |
| |
| return true; |
| } |
| |
| /** Convolution type indicator */ |
| enum ConvType { |
| START_ONLY, |
| NO_DELAY, |
| CUSTOM, |
| UNDEFINED, |
| }; |
| |
| static signalVector *convolve(const signalVector *x, const signalVector *h, |
| signalVector *y, ConvType spanType, |
| size_t start = 0, size_t len = 0) |
| { |
| int rc; |
| size_t head = 0, tail = 0; |
| bool alloc = false, append = false; |
| const signalVector *_x = NULL; |
| |
| if (!x || !h) |
| return NULL; |
| |
| switch (spanType) { |
| case START_ONLY: |
| start = 0; |
| head = h->size() - 1; |
| len = x->size(); |
| |
| if (x->getStart() < head) |
| append = true; |
| break; |
| case NO_DELAY: |
| start = h->size() / 2; |
| head = start; |
| tail = start; |
| len = x->size(); |
| append = true; |
| break; |
| case CUSTOM: |
| if (start < h->size() - 1) { |
| head = h->size() - start; |
| append = true; |
| } |
| if (start + len > x->size()) { |
| tail = start + len - x->size(); |
| append = true; |
| } |
| break; |
| default: |
| return NULL; |
| } |
| |
| /* |
| * Error if the output vector is too small. Create the output vector |
| * if the pointer is NULL. |
| */ |
| if (y && (len > y->size())) |
| return NULL; |
| if (!y) { |
| y = new signalVector(len, convolve_h_alloc, free); |
| alloc = true; |
| } |
| |
| /* Prepend or post-pend the input vector if the parameters require it */ |
| if (append) |
| _x = new signalVector(*x, head, tail); |
| else |
| _x = x; |
| |
| /* |
| * Four convovle types: |
| * 1. Complex-Real (aligned) |
| * 2. Complex-Complex (aligned) |
| * 3. Complex-Real (!aligned) |
| * 4. Complex-Complex (!aligned) |
| */ |
| if (h->isReal() && h->isAligned()) { |
| rc = convolve_real((float *) _x->begin(), _x->size(), |
| (float *) h->begin(), h->size(), |
| (float *) y->begin(), y->size(), |
| start, len); |
| } else if (!h->isReal() && h->isAligned()) { |
| rc = convolve_complex((float *) _x->begin(), _x->size(), |
| (float *) h->begin(), h->size(), |
| (float *) y->begin(), y->size(), |
| start, len); |
| } else if (h->isReal() && !h->isAligned()) { |
| rc = base_convolve_real((float *) _x->begin(), _x->size(), |
| (float *) h->begin(), h->size(), |
| (float *) y->begin(), y->size(), |
| start, len); |
| } else if (!h->isReal() && !h->isAligned()) { |
| rc = base_convolve_complex((float *) _x->begin(), _x->size(), |
| (float *) h->begin(), h->size(), |
| (float *) y->begin(), y->size(), |
| start, len); |
| } else { |
| rc = -1; |
| } |
| |
| if (append) |
| delete _x; |
| |
| if (rc < 0) { |
| if (alloc) |
| delete y; |
| return NULL; |
| } |
| |
| return y; |
| } |
| |
| /* |
| * Generate static EDGE linear equalizer. This equalizer is not adaptive. |
| * Filter taps are generated from the inverted 1 SPS impulse response of |
| * the EDGE pulse shape captured after the downsampling filter. |
| */ |
| static bool generateInvertC0Pulse(PulseSequence *pulse) |
| { |
| if (!pulse) |
| return false; |
| |
| pulse->c0_inv = new signalVector((complex *) convolve_h_alloc(5), 0, 5, convolve_h_alloc, free); |
| pulse->c0_inv->isReal(true); |
| pulse->c0_inv->setAligned(false); |
| |
| signalVector::iterator xP = pulse->c0_inv->begin(); |
| *xP++ = 0.15884; |
| *xP++ = -0.43176; |
| *xP++ = 1.00000; |
| *xP++ = -0.42608; |
| *xP++ = 0.14882; |
| |
| return true; |
| } |
| |
| static bool generateC1Pulse(int sps, PulseSequence *pulse) |
| { |
| int len; |
| |
| if (!pulse) |
| return false; |
| |
| switch (sps) { |
| case 4: |
| len = 8; |
| break; |
| default: |
| return false; |
| } |
| |
| pulse->c1 = new signalVector((complex *) convolve_h_alloc(len), 0, len, convolve_h_alloc, free); |
| pulse->c1->isReal(true); |
| |
| /* Enable alignment for SSE usage */ |
| pulse->c1->setAligned(true); |
| |
| signalVector::iterator xP = pulse->c1->begin(); |
| |
| switch (sps) { |
| case 4: |
| /* BT = 0.30 */ |
| *xP++ = 0.0; |
| *xP++ = 8.16373112e-03; |
| *xP++ = 2.84385729e-02; |
| *xP++ = 5.64158904e-02; |
| *xP++ = 7.05463553e-02; |
| *xP++ = 5.64158904e-02; |
| *xP++ = 2.84385729e-02; |
| *xP++ = 8.16373112e-03; |
| } |
| |
| return true; |
| } |
| |
| static PulseSequence *generateGSMPulse(int sps) |
| { |
| int len; |
| float arg, avg, center; |
| PulseSequence *pulse; |
| |
| if ((sps != 1) && (sps != 4)) |
| return NULL; |
| |
| /* Store a single tap filter used for correlation sequence generation */ |
| pulse = new PulseSequence(); |
| pulse->empty = new signalVector(1); |
| pulse->empty->isReal(true); |
| *(pulse->empty->begin()) = 1.0f; |
| |
| /* |
| * For 4 samples-per-symbol use a precomputed single pulse Laurent |
| * approximation. This should yields below 2 degrees of phase error at |
| * the modulator output. Use the existing pulse approximation for all |
| * other oversampling factors. |
| */ |
| switch (sps) { |
| case 4: |
| len = 16; |
| break; |
| case 1: |
| default: |
| len = 4; |
| } |
| |
| pulse->c0 = new signalVector((complex *) convolve_h_alloc(len), 0, len, convolve_h_alloc, free); |
| pulse->c0->isReal(true); |
| |
| /* Enable alingnment for SSE usage */ |
| pulse->c0->setAligned(true); |
| |
| signalVector::iterator xP = pulse->c0->begin(); |
| |
| if (sps == 4) { |
| *xP++ = 0.0; |
| *xP++ = 4.46348606e-03; |
| *xP++ = 2.84385729e-02; |
| *xP++ = 1.03184855e-01; |
| *xP++ = 2.56065552e-01; |
| *xP++ = 4.76375085e-01; |
| *xP++ = 7.05961177e-01; |
| *xP++ = 8.71291644e-01; |
| *xP++ = 9.29453645e-01; |
| *xP++ = 8.71291644e-01; |
| *xP++ = 7.05961177e-01; |
| *xP++ = 4.76375085e-01; |
| *xP++ = 2.56065552e-01; |
| *xP++ = 1.03184855e-01; |
| *xP++ = 2.84385729e-02; |
| *xP++ = 4.46348606e-03; |
| generateC1Pulse(sps, pulse); |
| } else { |
| center = (float) (len - 1.0) / 2.0; |
| |
| /* GSM pulse approximation */ |
| for (int i = 0; i < len; i++) { |
| arg = ((float) i - center) / (float) sps; |
| *xP++ = 0.96 * exp(-1.1380 * arg * arg - |
| 0.527 * arg * arg * arg * arg); |
| } |
| |
| avg = sqrtf(vectorNorm2(*pulse->c0) / sps); |
| xP = pulse->c0->begin(); |
| for (int i = 0; i < len; i++) |
| *xP++ /= avg; |
| } |
| |
| /* |
| * Current form of the EDGE equalization filter non-realizable at 4 SPS. |
| * Load the onto both 1 SPS and 4 SPS objects for convenience. Note that |
| * the EDGE demodulator downsamples to 1 SPS prior to equalization. |
| */ |
| generateInvertC0Pulse(pulse); |
| |
| return pulse; |
| } |
| |
| /* Convert -1..+1 soft bits to 0..1 soft bits */ |
| void vectorSlicer(float *dest, const float *src, size_t len) |
| { |
| size_t i; |
| for (i = 0; i < len; i++) { |
| dest[i] = 0.5 * (src[i] + 1.0f); |
| if (dest[i] > 1.0) |
| dest[i] = 1.0; |
| else if (dest[i] < 0.0) |
| dest[i] = 0.0; |
| } |
| } |
| |
| static signalVector *rotateBurst(const BitVector &wBurst, |
| 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 represenation 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; |
| } |