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Improved fading model generation

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master
Xavier Arteaga 5 years ago committed by Xavier Arteaga
parent a44a61d781
commit cca3cccfbe
3 changed files with 162 additions and 74 deletions
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29
lib/include/srslte/phy/channel/fading.h
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@ -26,6 +26,7 @@
#include <srslte/srslte.h>
#define SRSLTE_CHANNEL_FADING_MAXTAPS 9
#define SRSLTE_CHANNEL_FADING_NTERMS 16
typedef enum {
srslte_channel_fading_model_none = 0,
@ -40,22 +41,26 @@ typedef struct {
srslte_channel_fading_model_t model; // None, EPA, EVA, ETU
float doppler; // Maximum doppler: 5, 70, 300
// Internal tap parametrization
uint32_t N; // FFT size
uint32_t path_delay; // Path delay
double coeff_w[SRSLTE_CHANNEL_FADING_MAXTAPS]; // Angular Speed, random
double coeff_a[SRSLTE_CHANNEL_FADING_MAXTAPS]; // Modulation Coefficient
double coeff_p[SRSLTE_CHANNEL_FADING_MAXTAPS]; // Initial phase, random
// Internal tap parametrisation
uint32_t N; // FFT size
uint32_t path_delay; // Path delay
uint32_t state_len; // Length of the impulse response saved in the state
float coeff_alpha[SRSLTE_CHANNEL_FADING_MAXTAPS][SRSLTE_CHANNEL_FADING_NTERMS]; // Angle of arrival
float coeff_a[SRSLTE_CHANNEL_FADING_MAXTAPS][SRSLTE_CHANNEL_FADING_NTERMS]; // Random phase
float coeff_b[SRSLTE_CHANNEL_FADING_MAXTAPS][SRSLTE_CHANNEL_FADING_NTERMS]; // Random phase
cf_t* h_tap[SRSLTE_CHANNEL_FADING_MAXTAPS]; // Static tap signal in frequency domain
// Utils
srslte_dft_plan_t fft; // DFT to frequency domain
srslte_dft_plan_t ifft; // DFT to time domain
cf_t* temp; // Temporal buffer, length fft_size
cf_t* h_freq; // Channel frequency response, length fft_size
cf_t* y_freq; // Intermediate frequency domain buffer
srslte_dft_plan_t fft; // DFT to frequency domain
srslte_dft_plan_t ifft; // DFT to time domain
cf_t* temp; // Temporal buffer, length fft_size
cf_t* h_freq; // Channel frequency response, length fft_size
cf_t* y_freq; // Intermediate frequency domain buffer
float sin_table[1024]; // Table of sinus values
// State variables
cf_t* state; // Length fft_size/2
cf_t* state; // To save impulse response of the filter
} srslte_channel_fading_t;
#ifdef __cplusplus

182
lib/src/phy/channel/fading.c
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@ -22,16 +22,11 @@
#include "srslte/phy/channel/fading.h"
#include "srslte/phy/utils/random.h"
#include "srslte/phy/utils/vector.h"
#include <complex.h>
#include <math.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#define COEFF_A_MIN 100
#define COEFF_A_MAX 2000
/*
* Tables provided in 36.104 R10 section B.2 Multi-path fading propagation conditions
*/
@ -82,48 +77,115 @@ static inline int parse_model(srslte_channel_fading_t* q, const char* str)
return ret;
}
static inline float get_doppler_dispersion(double t, double a, double w, double p)
#ifdef LV_HAVE_SSE
#include <immintrin.h>
static inline __m128 _sine(const float* table, __m128 arg)
{
return (float)(a * sin(w * t + p));
__m128 ret;
int idx[4];
float sine[4];
__m128 turns =
_mm_round_ps(_mm_mul_ps(arg, _mm_set1_ps(1.0f / (2.0f * (float)M_PI))), (_MM_FROUND_TO_ZERO + _MM_FROUND_NO_EXC));
__m128 argmod = _mm_sub_ps(arg, _mm_mul_ps(turns, _mm_set1_ps(2.0f * (float)M_PI)));
__m128 indexps = _mm_mul_ps(argmod, _mm_set1_ps(1024.0f / (2.0f * (float)M_PI)));
__m128i indexi32 = _mm_abs_epi32(_mm_cvtps_epi32(indexps));
_mm_store_si128((__m128i*)idx, indexi32);
for (int i = 0; i < 4; i++) {
sine[i] = table[idx[i]];
}
ret = _mm_load_ps(sine);
return ret;
}
static inline __m128 _cosine(float* table, __m128 arg)
{
arg = _mm_add_ps(arg, _mm_set1_ps((float)M_PI_2));
return _sine(table, arg);
}
#endif /*LV_HAVE_SSE*/
static inline cf_t
get_doppler_dispersion(srslte_channel_fading_t* q, float t, float F_d, float* alpha, float* a, float* b)
{
#ifdef LV_HAVE_SSE
const float recN = 1.0f / sqrtf(SRSLTE_CHANNEL_FADING_NTERMS);
cf_t ret = 0;
__m128 _reacc = _mm_setzero_ps();
__m128 _imacc = _mm_setzero_ps();
__m128 _arg = _mm_set1_ps((float)M_PI * F_d);
__m128 _t = _mm_set1_ps(t);
__m128 _arg_ = (_mm_mul_ps(_arg, _t));
for (int i = 0; i < SRSLTE_CHANNEL_FADING_NTERMS; i += 4) {
__m128 _alpha = _mm_loadu_ps(&alpha[i]);
__m128 _a = _mm_loadu_ps(&a[i]);
__m128 _b = _mm_loadu_ps(&b[i]);
__m128 _arg1 = _mm_mul_ps(_arg_, _cosine(q->sin_table, _alpha));
__m128 _re = _cosine(q->sin_table, _mm_add_ps(_arg1, _a));
__m128 _im = _sine(q->sin_table, _mm_add_ps(_arg1, _b));
_reacc = _mm_add_ps(_reacc, _re);
_imacc = _mm_add_ps(_imacc, _im);
}
__m128 _tmp = _mm_hadd_ps(_reacc, _imacc);
_tmp = _mm_hadd_ps(_tmp, _tmp);
float r[4];
_mm_store_ps(r, _tmp);
__real__ ret = r[0];
__imag__ ret = r[1];
return ret * recN;
#else
const float recN = 1.0f / sqrtf(SRSLTE_CHANNEL_FADING_NTERMS);
cf_t r = 0;
for (uint32_t i = 0; i < SRSLTE_CHANNEL_FADING_NTERMS; i++) {
float arg = (float)M_PI * F_d * cosf(alpha[i]) * t;
__real__ r += cosf(arg + a[i]);
__imag__ r += sinf(arg + b[i]);
}
return recN * r;
#endif /*LV_HAVE_SSE*/
}
static inline void
generate_tap(float delay_ns, float power_db, float srate, float phase, cf_t* buf, uint32_t N, uint32_t path_delay)
static inline void generate_tap(float delay_ns, float power_db, float srate, cf_t* buf, uint32_t N, uint32_t path_delay)
{
float amplitude = srslte_convert_dB_to_power(power_db);
float O = (delay_ns * 1e-9f * srate + path_delay) / (float)N;
cf_t a0 = amplitude * cexpf(-_Complex_I * phase) / N;
cf_t a0 = amplitude / N;
srslte_vec_gen_sine(a0, -O, buf, N);
}
static inline void generate_taps(srslte_channel_fading_t* q, double time)
static inline void generate_taps(srslte_channel_fading_t* q, float time)
{
// Initialise freq response
bzero(q->h_freq, sizeof(cf_t) * q->N);
// Generate taps
for (int i = 0; i < nof_taps[q->model]; i++) {
// Compute phase for thee doppler dispersion
float phase = get_doppler_dispersion(time, q->coeff_a[i], q->coeff_w[i], q->coeff_p[i]);
// Generate tab
generate_tap(excess_tap_delay_ns[q->model][i],
relative_power_db[q->model][i],
q->srate,
phase,
q->temp,
q->N,
q->path_delay);
// Add to frequency response
srslte_vec_sum_ccc(q->h_freq, q->temp, q->h_freq, q->N);
}
// Compute phase for the doppler dispersion
cf_t a = get_doppler_dispersion(q, time, q->doppler, q->coeff_alpha[i], q->coeff_a[i], q->coeff_b[i]);
if (i) {
// Copy tap frequency response
srslte_vec_sc_prod_ccc(q->h_tap[i], a, q->temp, q->N);
// Add to frequency response, shifts FFT at same time
srslte_vec_sum_ccc(q->h_freq, &q->temp[q->N / 2], q->h_freq, q->N / 2);
srslte_vec_sum_ccc(&q->h_freq[q->N / 2], q->temp, &q->h_freq[q->N / 2], q->N / 2);
} else {
// Copy tap frequency response
srslte_vec_sc_prod_ccc(&q->h_tap[i][q->N / 2], a, q->h_freq, q->N / 2);
srslte_vec_sc_prod_ccc(&q->h_tap[i][0], a, &q->h_freq[q->N / 2], q->N / 2);
}
}
// at this stage, q->h_freq should contain the frequency response
}
static void filter_segment(srslte_channel_fading_t* q, const cf_t* input, cf_t* output, uint32_t nsamples)
static inline void filter_segment(srslte_channel_fading_t* q, const cf_t* input, cf_t* output, uint32_t nsamples)
{
// Fill Input vector
memcpy(q->temp, input, sizeof(cf_t) * nsamples);
@ -139,14 +201,14 @@ static void filter_segment(srslte_channel_fading_t* q, const cf_t* input, cf_t*
srslte_dft_run_c_zerocopy(&q->ifft, q->y_freq, q->temp);
// Add state
srslte_vec_sum_ccc(q->temp, q->state, q->temp, q->N);
srslte_vec_sum_ccc(q->temp, q->state, q->temp, q->state_len);
// Copy output
memcpy(output, q->temp, sizeof(cf_t) * nsamples);
// Copy state
memcpy(q->state, &q->temp[nsamples], sizeof(cf_t) * (q->N - nsamples));
bzero(&q->state[q->N - nsamples], sizeof(cf_t) * nsamples);
q->state_len = q->N - nsamples;
memcpy(q->state, &q->temp[q->state_len], sizeof(cf_t) * q->state_len);
}
int srslte_channel_fading_init(srslte_channel_fading_t* q, double srate, const char* model, uint32_t seed)
@ -164,19 +226,35 @@ int srslte_channel_fading_init(srslte_channel_fading_t* q, double srate, const c
q->srate = (float)srate;
// Populate internal parameters
q->N = SRSLTE_MAX((uint32_t)1 << (uint32_t)(
round(log2(excess_tap_delay_ns[q->model][nof_taps[q->model] - 1] * 1e-9 * srate)) + 3),
64);
uint32_t fft_min_pow =
(uint32_t)round(log2(excess_tap_delay_ns[q->model][nof_taps[q->model] - 1] * 1e-9 * srate)) + 3;
q->N = SRSLTE_MAX(1U << fft_min_pow, (uint32_t)(srate / (15e3f * 4.0f)));
q->path_delay = q->N / 4;
q->state_len = 0;
// Initialise random number
srslte_random_t* random = srslte_random_init(seed);
// Initialise values
for (int i = 0; i < nof_taps[q->model]; i++) {
q->coeff_a[i] = srslte_random_uniform_real_dist(random, COEFF_A_MIN, COEFF_A_MAX);
q->coeff_w[i] = 2.0 * M_PI * q->doppler / q->coeff_a[i];
q->coeff_p[i] = srslte_random_uniform_real_dist(random, 0, (float)M_PI / 2.0f);
// Initialise values for each tap
for (uint32_t i = 0; i < nof_taps[q->model]; i++) {
// Random Jakes model Coeffients
for (uint32_t j = 0; (float)j < SRSLTE_CHANNEL_FADING_NTERMS; j++) {
q->coeff_a[i][j] = srslte_random_uniform_real_dist(random, 0, 2.0f * (float)M_PI);
q->coeff_b[i][j] = srslte_random_uniform_real_dist(random, 0, 2.0f * (float)M_PI);
q->coeff_alpha[i][j] = ((float)M_PI * ((float)i - (float)0.5f)) / (2.0f * nof_taps[q->model]);
}
// Allocate tap frequency response
q->h_tap[i] = srslte_vec_malloc(sizeof(cf_t) * q->N);
// Generate tap frequency response
generate_tap(
excess_tap_delay_ns[q->model][i], relative_power_db[q->model][i], q->srate, q->h_tap[i], q->N, q->path_delay);
}
// Generate sine Table
for (uint32_t i = 0; i < 1024; i++) {
q->sin_table[i] = sinf((float)i * 2.0f * (float)M_PI / 1024);
}
// Free random
@ -195,30 +273,30 @@ int srslte_channel_fading_init(srslte_channel_fading_t* q, double srate, const c
}
// Allocate memory
q->temp = srslte_vec_malloc(sizeof(cf_t) * q->N);
q->temp = srslte_vec_cf_malloc(q->N);
if (!q->temp) {
fprintf(stderr, "Error: allocating h_freq\n");
goto clean_exit;
}
q->h_freq = srslte_vec_malloc(sizeof(cf_t) * q->N);
q->h_freq = srslte_vec_cf_malloc(q->N);
if (!q->h_freq) {
fprintf(stderr, "Error: allocating h_freq\n");
goto clean_exit;
}
q->y_freq = srslte_vec_malloc(sizeof(cf_t) * q->N);
q->y_freq = srslte_vec_cf_malloc(q->N);
if (!q->y_freq) {
fprintf(stderr, "Error: allocating y_freq\n");
goto clean_exit;
}
q->state = srslte_vec_malloc(sizeof(cf_t) * q->N);
q->state = srslte_vec_cf_malloc(q->N);
if (!q->state) {
fprintf(stderr, "Error: allocating y_freq\n");
goto clean_exit;
}
bzero(q->state, sizeof(cf_t) * q->N);
srslte_vec_cf_zero(q->state, q->N);
}
ret = SRSLTE_SUCCESS;
@ -245,6 +323,12 @@ void srslte_channel_fading_free(srslte_channel_fading_t* q)
free(q->y_freq);
}
for (int i = 0; i < nof_taps[q->model]; i++) {
if (q->h_tap[i]) {
free(q->h_tap[i]);
}
}
if (q->state) {
free(q->state);
}
@ -262,10 +346,10 @@ double srslte_channel_fading_execute(srslte_channel_fading_t* q,
if (q) {
while (counter < nsamples) {
// Generate taps
generate_taps(q, init_time);
generate_taps(q, (float)init_time);
// Do not process more than N / 4 samples
uint32_t n = SRSLTE_MIN(q->N / 4, nsamples - counter);
// Do not process more than N/2 samples
uint32_t n = SRSLTE_MIN(q->N / 2, nsamples - counter);
// Execute
filter_segment(q, &in[counter], &out[counter], n);

25
lib/src/phy/channel/test/fading_channel_test.c
Unescape Escape View File

@ -30,7 +30,7 @@
#include <sys/time.h>
#include <unistd.h>
#undef ENABLE_GUI /* Disable GUI by default */
//#undef ENABLE_GUI /* Disable GUI by default */
#ifdef ENABLE_GUI
#include "srsgui/srsgui.h"
static bool enable_gui = false;
@ -75,11 +75,11 @@ static void parse_args(int argc, char** argv)
case 'r':
random_seed = (uint32_t)strtol(argv[optind], NULL, 10);
break;
#ifdef ENABLE_GUI
case 'g':
enable_gui ^= true;
break;
#ifdef ENABLE_GUI
enable_gui = (enable_gui) ? false : true;
#endif /* ENABLE_GUI */
break;
default:
usage(argv[0]);
exit(-1);
@ -196,18 +196,18 @@ int main(int argc, char** argv)
if (enable_gui) {
srslte_dft_run_c_zerocopy(&fft, output_buffer, fft_buffer);
srslte_vec_prod_conj_ccc(fft_buffer, fft_buffer, fft_buffer, srate / 1000);
for (int i = 0; i < srate / 1000; i++) {
fft_mag[i] = srslte_convert_power_to_dB(__real__ fft_buffer[i]);
for (int j = 0; j < srate / 1000; j++) {
fft_mag[j] = srslte_convert_power_to_dB(__real__ fft_buffer[j]);
}
plot_real_setNewData(&plot_fft, fft_mag, srate / 1000);
for (int i = 0; i < channel_fading.N; i++) {
fft_mag[i] = srslte_convert_amplitude_to_dB(cabsf(channel_fading.h_freq[i]));
for (int j = 0; j < channel_fading.N; j++) {
fft_mag[j] = srslte_convert_amplitude_to_dB(cabsf(channel_fading.h_freq[j]));
}
plot_real_setNewData(&plot_h, fft_mag, channel_fading.N);
for (int i = 0; i < srate / 1000; i++) {
imp[i] = cabsf(output_buffer[i]);
for (int j = 0; j < srate / 1000; j++) {
imp[j] = cabsf(output_buffer[j]);
}
plot_real_setNewData(&plot_imp, imp, channel_fading.N);
@ -229,7 +229,7 @@ clean_exit:
#ifdef ENABLE_GUI
if (enable_gui) {
sdrgui_exit();
if (fft_mag) {
free(fft_mag);
}
@ -240,7 +240,6 @@ clean_exit:
free(fft_buffer);
}
srslte_dft_plan_free(&fft);
sdrgui_exit();
}
#endif /* ENABLE_GUI */
if (input_buffer) {
@ -250,5 +249,5 @@ clean_exit:
free(output_buffer);
}
srslte_channel_fading_free(&channel_fading);
exit(ret);
return ret;
}

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