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airprobe/src/lib/gsm_receiver_cf.cc

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/* -*- c++ -*- */
/*
* Copyright 2004 Free Software Foundation, Inc.
*
* This file is part of GNU Radio
*
* GNU Radio is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 3, or (at your option)
* any later version.
*
* GNU Radio 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with GNU Radio; see the file COPYING. If not, write to
* the Free Software Foundation, Inc., 51 Franklin Street,
* Boston, MA 02110-1301, USA.
*/
#ifdef HAVE_CONFIG_H
#include "config.h"
#endif
#include <gr_io_signature.h>
#include <gr_math.h>
#include <math.h>
#include <Assert.h>
#include <list>
#include <boost/circular_buffer.hpp>
#include <algorithm>
#include <gsm_receiver_cf.h>
#include <viterbi_detector.h>
#include <sch.h>
#define FCCH_BUFFER_SIZE (FCCH_HITS_NEEDED)
#define SYNC_SEARCH_RANGE 30
#define TRAIN_SEARCH_RANGE 40
//TODO !! - move this methods to some else place
// - move it to some else place !!
typedef std::list<float> list_float;
typedef std::vector<float> vector_float;
typedef boost::circular_buffer<float> circular_buffer_float;
gsm_receiver_cf_sptr
gsm_make_receiver_cf(gr_feval_dd *tuner, int osr)
{
return gsm_receiver_cf_sptr(new gsm_receiver_cf(tuner, osr));
}
static const int MIN_IN = 1; // mininum number of input streams
static const int MAX_IN = 1; // maximum number of input streams
static const int MIN_OUT = 0; // minimum number of output streams
static const int MAX_OUT = 1; // maximum number of output streams
/*
* The private constructor
*/
gsm_receiver_cf::gsm_receiver_cf(gr_feval_dd *tuner, int osr)
: gr_block("gsm_receiver",
gr_make_io_signature(MIN_IN, MAX_IN, sizeof(gr_complex)),
gr_make_io_signature(MIN_OUT, MAX_OUT, 142 * sizeof(float))),
d_OSR(osr),
d_chan_imp_length(CHAN_IMP_RESP_LENGTH),
d_tuner(tuner),
d_counter(0),
d_fcch_start_pos(0),
d_freq_offset(0),
d_state(first_fcch_search),
d_burst_nr(osr)
// d_fcch_count(0), //!!
// d_x_temp(0),//!!
// d_x2_temp(0)//!!
{
int i;
gmsk_mapper(SYNC_BITS, N_SYNC_BITS, d_sch_training_seq, gr_complex(0.0,-1.0));
for (i = 0; i < TRAIN_SEQ_NUM; i++) {
gmsk_mapper(train_seq[i], N_TRAIN_BITS, d_norm_training_seq[i], gr_complex(1.0,0.0));
}
}
/*
* Virtual destructor.
*/
gsm_receiver_cf::~gsm_receiver_cf()
{
}
void gsm_receiver_cf::forecast(int noutput_items, gr_vector_int &ninput_items_required)
{
ninput_items_required[0] = noutput_items * (TS_BITS + 2 * SAFETY_MARGIN) * d_OSR;
}
int
gsm_receiver_cf::general_work(int noutput_items,
gr_vector_int &ninput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
const gr_complex *in = (const gr_complex *) input_items[0];
float *out = (float *) output_items[0];
int produced_out = 0;
float prev_freq_offset;
switch (d_state) {
//bootstrapping
case first_fcch_search:
if (find_fcch_burst(in, ninput_items[0])) {
set_frequency(d_freq_offset);
produced_out = 0;
d_state = next_fcch_search;
} else {
produced_out = 0;
d_state = first_fcch_search;
}
break;
case next_fcch_search:
prev_freq_offset = d_freq_offset;
if (find_fcch_burst(in, ninput_items[0])) {
if (abs(d_freq_offset) > 100) {
set_frequency(d_freq_offset);
}
produced_out = 0;
d_state = sch_search;
} else {
produced_out = 0;
d_state = next_fcch_search;
}
break;
case sch_search: {
gr_complex chan_imp_resp[CHAN_IMP_RESP_LENGTH*d_OSR];
int t1, t2, t3;
int burst_start = 0;
unsigned char output_binary[BURST_SIZE];
if (find_sch_burst(in, ninput_items[0], out)) {
burst_start = get_sch_chan_imp_resp(in, chan_imp_resp);
detect_burst(in, chan_imp_resp, burst_start, output_binary);
if (decode_sch(&output_binary[3], &t1, &t2, &t3, &d_ncc, &d_bcc) == 0) {
DCOUT("sch burst_start: " << burst_start);
d_burst_nr.set(t1, t2, t3, 0);
DCOUT("bcc: " << d_bcc << " ncc: " << d_ncc << " t1: " << t1 << " t2: " << t2 << " t3: " << t3);
d_channel_conf.set_multiframe_type(TSC0, multiframe_51);
d_channel_conf.set_burst_types(TSC0, FCCH_FRAMES, sizeof(FCCH_FRAMES) / sizeof(unsigned), fcch_burst);
d_channel_conf.set_burst_types(TSC0, SCH_FRAMES, sizeof(SCH_FRAMES) / sizeof(unsigned), sch_burst);
d_channel_conf.set_burst_types(TSC0, BCCH_FRAMES, sizeof(BCCH_FRAMES) / sizeof(unsigned), normal_burst);
d_burst_nr++;
consume_each(burst_start + BURST_SIZE * d_OSR);
d_state = synchronized;
} else {
d_state = next_fcch_search;
}
} else {
d_state = sch_search;
}
break;
}
//in this state receiver is synchronized and it processes bursts according to burst type for given burst number
case synchronized: {
gr_complex chan_imp_resp[d_chan_imp_length*d_OSR];
burst_type b_type = d_channel_conf.get_burst_type(d_burst_nr);
int burst_start;
int offset = 0;
int to_consume = 0;
unsigned char output_binary[BURST_SIZE];
switch (b_type) {
case fcch_burst: {
int ii;
int first_sample = ceil((GUARD_PERIOD + 2 * TAIL_BITS) * d_OSR) + 1;
int last_sample = first_sample + USEFUL_BITS * d_OSR;
double phase_sum = 0;
for (ii = first_sample; ii < last_sample; ii++) {
double phase_diff = compute_phase_diff(in[ii], in[ii-1]) - (M_PI / 2) / d_OSR;
phase_sum += phase_diff;
}
double freq_offset = compute_freq_offset(phase_sum, last_sample - first_sample);
if (abs(freq_offset) > FCCH_MAX_FREQ_OFFSET) {
d_freq_offset -= freq_offset;
set_frequency(d_freq_offset);
DCOUT("adjusting frequency, new frequency offset: " << d_freq_offset << "\n");
}
}
break;
case sch_burst: {
int t1, t2, t3, d_ncc, d_bcc;
burst_start = get_sch_chan_imp_resp(in, chan_imp_resp);
detect_burst(in, &d_channel_imp_resp[0], burst_start, output_binary);
if (decode_sch(&output_binary[3], &t1, &t2, &t3, &d_ncc, &d_bcc) == 0) {
// d_burst_nr.set(t1, t2, t3, 0);
DCOUT("bcc: " << d_bcc << " ncc: " << d_ncc << " t1: " << t1 << " t2: " << t2 << " t3: " << t3);
offset = burst_start - floor((GUARD_PERIOD) * d_OSR);
DCOUT(offset);
to_consume += offset;
}
}
break;
case normal_burst:
// std::cout << "# name: norm_complex\n" ;
// std::cout << "# type: complex matrix\n" ;
// std::cout << "# rows: 1\n" ;
// std::cout << "# columns: " << floor(d_OSR*(TS_BITS+GUARD_PERIOD)) << "\n";
burst_start = get_norm_chan_imp_resp(in, chan_imp_resp, TRAIN_SEARCH_RANGE);
// std::cout << burst_start << "\n" ;
detect_burst(in, &d_channel_imp_resp[0], burst_start, output_binary);
// printf("burst = [ ");
//
for (int i = 0; i < BURST_SIZE ; i++) {
printf(" %d", output_binary[i]);
}
printf("];\n");
//
// for(int i=0; i<floor(d_OSR*(TS_BITS+GUARD_PERIOD)); i++){
// std::cout << in[i] << "\n";
// }
break;
case rach_burst:
break;
case dummy:
break;
case empty:
break;
}
d_burst_nr++;
to_consume += TS_BITS * d_OSR + d_burst_nr.get_offset();
consume_each(to_consume);
}
break;
}
return produced_out;
}
bool gsm_receiver_cf::find_fcch_burst(const gr_complex *in, const int nitems)
{
circular_buffer_float phase_diff_buffer(FCCH_BUFFER_SIZE * d_OSR);
float phase_diff = 0;
gr_complex conjprod;
int hit_count = 0;
int miss_count = 0;
int start_pos = -1;
float min_phase_diff;
float max_phase_diff;
double best_sum;
float lowest_max_min_diff = 99999;
int to_consume = 0;
int sample_number = 0;
bool end = false;
bool result = false;
double freq_offset;
circular_buffer_float::iterator buffer_iter;
enum states {
init, search, found_something, fcch_found, search_fail
} fcch_search_state;
fcch_search_state = init;
while (!end) {
switch (fcch_search_state) {
case init:
hit_count = 0;
miss_count = 0;
start_pos = -1;
lowest_max_min_diff = 99999;
phase_diff_buffer.clear();
fcch_search_state = search;
break;
case search:
sample_number++;
if (sample_number > nitems - FCCH_BUFFER_SIZE * d_OSR) {
to_consume = sample_number;
fcch_search_state = search_fail;
} else {
phase_diff = compute_phase_diff(in[sample_number], in[sample_number-1]);
if (phase_diff > 0) {
to_consume = sample_number;
fcch_search_state = found_something;
} else {
fcch_search_state = search;
}
}
break;
case found_something:
if (phase_diff > 0) {
hit_count++;
} else {
miss_count++;
}
if ((miss_count >= FCCH_MAX_MISSES * d_OSR) && (hit_count <= FCCH_HITS_NEEDED * d_OSR)) {
fcch_search_state = init;
continue;
} else if (((miss_count >= FCCH_MAX_MISSES * d_OSR) && (hit_count > FCCH_HITS_NEEDED * d_OSR)) || (hit_count > 2 * FCCH_HITS_NEEDED * d_OSR)) {
fcch_search_state = fcch_found;
continue;
} else if ((miss_count < FCCH_MAX_MISSES * d_OSR) && (hit_count > FCCH_HITS_NEEDED * d_OSR)) {
//find difference between minimal and maximal element in the buffer
//for FCCH this value should be low
//this part is searching for a region where this value is lowest
min_phase_diff = * (min_element(phase_diff_buffer.begin(), phase_diff_buffer.end()));
max_phase_diff = * (max_element(phase_diff_buffer.begin(), phase_diff_buffer.end()));
if (lowest_max_min_diff > max_phase_diff - min_phase_diff) {
lowest_max_min_diff = max_phase_diff - min_phase_diff;
start_pos = sample_number - FCCH_HITS_NEEDED * d_OSR - FCCH_MAX_MISSES * d_OSR;
best_sum = 0;
for (buffer_iter = phase_diff_buffer.begin();
buffer_iter != (phase_diff_buffer.end());
buffer_iter++) {
best_sum += *buffer_iter - (M_PI / 2) / d_OSR;
}
}
}
sample_number++;
if (sample_number >= nitems) {
fcch_search_state = search_fail;
continue;
}
phase_diff = compute_phase_diff(in[sample_number], in[sample_number-1]);
phase_diff_buffer.push_back(phase_diff);
fcch_search_state = found_something;
break;
case fcch_found:
DCOUT("fcch found on position: " << d_counter + start_pos);
to_consume = start_pos + FCCH_HITS_NEEDED * d_OSR + 1;
d_fcch_start_pos = d_counter + start_pos;
freq_offset = compute_freq_offset(best_sum, FCCH_HITS_NEEDED);
d_freq_offset -= freq_offset;
DCOUT("freq_offset: " << d_freq_offset);
end = true;
result = true;
break;
case search_fail:
end = true;
result = false;
break;
}
}
d_counter += to_consume;
consume_each(to_consume);
return result;
}
double gsm_receiver_cf::compute_freq_offset(double best_sum, unsigned denominator)
{
float phase_offset, freq_offset;
phase_offset = best_sum / denominator;
freq_offset = phase_offset * 1625000.0 / (12.0 * M_PI);
// d_fcch_count++;
// d_x_temp += freq_offset;
// d_x2_temp += freq_offset * freq_offset;
// d_mean = d_x_temp / d_fcch_count;
// DCOUT("freq_offset: " << freq_offset); //" best_sum: " << best_sum
// DCOUT("wariance: " << sqrt((d_x2_temp / d_fcch_count - d_mean * d_mean)) << " fcch_count:" << d_fcch_count << " d_mean: " << d_mean);
return freq_offset;
}
void gsm_receiver_cf::set_frequency(double freq_offset)
{
d_tuner->calleval(freq_offset);
}
inline float gsm_receiver_cf::compute_phase_diff(gr_complex val1, gr_complex val2)
{
gr_complex conjprod = val1 * conj(val2);
return gr_fast_atan2f(imag(conjprod), real(conjprod));
}
bool gsm_receiver_cf::find_sch_burst(const gr_complex *in, const int nitems , float *out)
{
int to_consume = 0;
bool end = false;
bool result = false;
int sample_nr_near_sch_start = d_fcch_start_pos + (FRAME_BITS - SAFETY_MARGIN) * d_OSR;
// vector_complex correlation_buffer;
// vector_float power_buffer;
// vector_float window_energy_buffer;
enum states {
start, reach_sch, search_not_finished, sch_found
} sch_search_state;
sch_search_state = start;
while (!end) {
switch (sch_search_state) {
case start:
if (d_counter < sample_nr_near_sch_start) {
sch_search_state = reach_sch;
} else {
sch_search_state = sch_found;
}
break;
case reach_sch:
if (d_counter + nitems >= sample_nr_near_sch_start) {
to_consume = sample_nr_near_sch_start - d_counter;
} else {
to_consume = nitems;
}
sch_search_state = search_not_finished;
break;
case search_not_finished:
result = false;
end = true;
break;
case sch_found:
to_consume = 0;
result = true;
end = true;
break;
}
}
d_counter += to_consume;
consume_each(to_consume);
return result;
}
int gsm_receiver_cf::get_sch_chan_imp_resp(const gr_complex *in, gr_complex * chan_imp_resp)
{
vector_complex correlation_buffer;
vector_float power_buffer;
vector_float window_energy_buffer;
int strongest_window_nr;
int burst_start = 0;
int chan_imp_resp_center;
float max_correlation = 0;
float energy = 0;
for (int ii = SYNC_POS * d_OSR; ii < (SYNC_POS + SYNC_SEARCH_RANGE) *d_OSR; ii++) {
gr_complex correlation = correlate_sequence(&d_sch_training_seq[5], &in[ii], N_SYNC_BITS - 10);
correlation_buffer.push_back(correlation);
power_buffer.push_back(pow(abs(correlation), 2));
}
//compute window energies
vector_float::iterator iter = power_buffer.begin();
bool loop_end = false;
while (iter != power_buffer.end()) {
vector_float::iterator iter_ii = iter;
energy = 0;
for (int ii = 0; ii < (d_chan_imp_length) *d_OSR; ii++, iter_ii++) {
if (iter_ii == power_buffer.end()) {
loop_end = true;
break;
}
energy += (*iter_ii);
}
if (loop_end) {
break;
}
iter++;
window_energy_buffer.push_back(energy);
}
strongest_window_nr = max_element(window_energy_buffer.begin(), window_energy_buffer.end()) - window_energy_buffer.begin();
d_channel_imp_resp.clear();
max_correlation = 0;
for (int ii = 0; ii < (d_chan_imp_length) *d_OSR; ii++) {
gr_complex correlation = correlation_buffer[strongest_window_nr + ii];
if (abs(correlation) > max_correlation) {
chan_imp_resp_center = ii;
max_correlation = abs(correlation);
}
d_channel_imp_resp.push_back(correlation);
chan_imp_resp[ii] = correlation;
}
burst_start = strongest_window_nr + chan_imp_resp_center - 48 * d_OSR - 2 * d_OSR + 2 + SYNC_POS * d_OSR;
return burst_start;
}
void gsm_receiver_cf::detect_burst(const gr_complex * in, gr_complex * chan_imp_resp, int burst_start, unsigned char * output_binary)
{
float output[BURST_SIZE];
gr_complex rhh_temp[CHAN_IMP_RESP_LENGTH*d_OSR];
gr_complex rhh[CHAN_IMP_RESP_LENGTH];
gr_complex filtered_burst[BURST_SIZE];
int start_state = 3;
unsigned int stop_states[2] = {4, 12};
autocorrelation(chan_imp_resp, rhh_temp, d_chan_imp_length*d_OSR);
for (int ii = 0; ii < (d_chan_imp_length); ii++) {
rhh[ii] = conj(rhh_temp[ii*d_OSR]);
}
mafi(&in[burst_start], BURST_SIZE, chan_imp_resp, d_chan_imp_length*d_OSR, filtered_burst);
viterbi_detector(filtered_burst, BURST_SIZE, rhh, start_state, stop_states, 2, output);
for (int i = 0; i < BURST_SIZE ; i++) {
output_binary[i] = (output[i] > 0);
}
}
//TODO consider placing this funtion in a separate class for signal processing
void gsm_receiver_cf::gmsk_mapper(const unsigned char * input, int ninput, gr_complex * gmsk_output, gr_complex start_point)
{
gr_complex j = gr_complex(0.0, 1.0);
int current_symbol;
int encoded_symbol;
int previous_symbol = 2 * input[0] - 1;
gmsk_output[0] = start_point;
for (int i = 1; i < ninput; i++) {
//change bits representation to NRZ
current_symbol = 2 * input[i] - 1;
//differentially encode
encoded_symbol = current_symbol * previous_symbol;
//and do gmsk mapping
gmsk_output[i] = j * gr_complex(encoded_symbol, 0.0) * gmsk_output[i-1];
previous_symbol = current_symbol;
}
}
//TODO consider use of some generalized function for correlation and placing it in a separate class for signal processing
gr_complex gsm_receiver_cf::correlate_sequence(const gr_complex * sequence, const gr_complex * input_signal, int length)
{
gr_complex result(0.0, 0.0);
int sample_number = 0;
for (int ii = 0; ii < length; ii++) {
sample_number = (ii * d_OSR) ;
result += sequence[ii] * conj(input_signal[sample_number]);
}
result = result / gr_complex(length, 0);
return result;
}
// gr_complex gsm_receiver_cf::compute_energy(const gr_complex * input_signal, int length)
// {
// float result = 0;
// int sample_number = 0;
//
// for (int ii = 0; ii < length; ii++) {
// result += input_signal[(ii * d_OSR)];
// }
//
// return result;
// }
//computes autocorrelation for positive values
//TODO consider placing this funtion in a separate class for signal processing
inline void gsm_receiver_cf::autocorrelation(const gr_complex * input, gr_complex * out, int length)
{
int i, k;
for (k = length - 1; k >= 0; k--) {
out[k] = gr_complex(0, 0);
for (i = k; i < length; i++) {
out[k] += input[i] * conj(input[i-k]);
}
}
}
//TODO consider use of some generalized function for filtering and placing it in a separate class for signal processing
//funkcja matched filter
inline void gsm_receiver_cf::mafi(const gr_complex * input, int input_length, gr_complex * filter, int filter_length, gr_complex * output)
{
int ii = 0, n, a;
for (n = 0; n < input_length; n++) {
a = n * d_OSR;
output[n] = 0;
ii = 0;
while (ii < filter_length) {
if ((a + ii) >= input_length*d_OSR)
break;
output[n] += input[a+ii] * filter[ii];
ii++;
}
}
}
int gsm_receiver_cf::get_norm_chan_imp_resp(const gr_complex *in, gr_complex * chan_imp_resp, unsigned search_range)
{
vector_complex correlation_buffer;
vector_float power_buffer;
vector_float window_energy_buffer;
int strongest_window_nr;
int burst_start = 0;
int chan_imp_resp_center;
float max_correlation = 0;
float energy = 0;
int search_start_pos = floor((TRAIN_POS + GUARD_PERIOD) * d_OSR);
int search_stop_pos = search_start_pos + search_range * d_OSR;
// std::cout << "# name: correlation\n" ;
// std::cout << "# type: complex matrix\n" ;
// std::cout << "# rows: 1\n" ;
// std::cout << "# columns: " << (search_stop_pos - search_start_pos) << "\n";
for (int ii = search_start_pos; ii < search_stop_pos; ii++) {
// for (int ii = SYNC_POS * d_OSR; ii < (SYNC_POS + SYNC_SEARCH_RANGE) *d_OSR; ii++) {
// for (int ii = 1; ii < (150) *d_OSR; ii++) {
gr_complex correlation = correlate_sequence(&d_norm_training_seq[d_bcc][5], &in[ii], N_TRAIN_BITS - 10);
// std::cout << correlation << "\n" ;
correlation_buffer.push_back(correlation);
power_buffer.push_back(pow(abs(correlation), 2));
}
//compute window energies
vector_float::iterator iter = power_buffer.begin();
bool loop_end = false;
while (iter != power_buffer.end()) {
vector_float::iterator iter_ii = iter;
energy = 0;
for (int ii = 0; ii < (d_chan_imp_length)*d_OSR; ii++, iter_ii++) {
if (iter_ii == power_buffer.end()) {
loop_end = true;
break;
}
energy += (*iter_ii);
}
if (loop_end) {
break;
}
iter++;
// std::cout << energy << "\n";
window_energy_buffer.push_back(energy);
}
strongest_window_nr = max_element(window_energy_buffer.begin(), window_energy_buffer.end()) - window_energy_buffer.begin();
d_channel_imp_resp.clear();
strongest_window_nr = 36;
max_correlation = 0;
for (int ii = 0; ii < (d_chan_imp_length)*d_OSR; ii++) {
gr_complex correlation = correlation_buffer[strongest_window_nr + ii];
if (abs(correlation) > max_correlation) {
chan_imp_resp_center = ii;
max_correlation = abs(correlation);
}
d_channel_imp_resp.push_back(correlation);
chan_imp_resp[ii] = correlation;
}
std::cout << "center: " << strongest_window_nr + chan_imp_resp_center << " stronegest window nr: " << strongest_window_nr << "\n";
burst_start = search_start_pos + strongest_window_nr + chan_imp_resp_center - 66 * d_OSR - 2 * d_OSR + 2;
return burst_start;
}
void gsm_receiver_cf::detect_norm_burst(const gr_complex * in, gr_complex * chan_imp_resp, int burst_start, unsigned char * output_binary)
{
float output[BURST_SIZE];
gr_complex rhh_temp[CHAN_IMP_RESP_LENGTH*d_OSR];
gr_complex rhh[CHAN_IMP_RESP_LENGTH];
gr_complex filtered_burst[BURST_SIZE];
int start_state = 3;
unsigned int stop_states[2] = {4, 12};
autocorrelation(chan_imp_resp, rhh_temp, d_chan_imp_length*d_OSR);
for (int ii = 0; ii < (d_chan_imp_length); ii++) {
rhh[ii] = conj(rhh_temp[ii*d_OSR]);
}
mafi_norm(&in[burst_start], BURST_SIZE, chan_imp_resp, d_chan_imp_length*d_OSR, filtered_burst);
viterbi_detector(filtered_burst, BURST_SIZE, rhh, start_state, stop_states, 2, output);
for (int i = 0; i < BURST_SIZE ; i++) {
output_binary[i] = (output[i] > 0);
}
}
inline void gsm_receiver_cf::mafi_norm(const gr_complex * input, int input_length, gr_complex * filter, int filter_length, gr_complex * output)
{
int ii = 0, n, a;
for (n = 0; n < input_length; n++) {
a = n * d_OSR;
output[n] = 0;
ii = 0;
while (ii < filter_length) {
if ((a + ii) >= input_length*d_OSR)
break;
output[n] += input[a+ii] * filter[ii]; //!!conj
ii++;
}
}
}
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