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gr-gsm/lib/receiver/receiver_impl.cc

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/* -*- c++ -*- */
/*
* @file
* @author Piotr Krysik <ptrkrysik@gmail.com>
* @section LICENSE
*
* Gr-gsm 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.
*
* Gr-gsm 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 gr-gsm; 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 <gnuradio/io_signature.h>
#include <gnuradio/math.h>
#include <math.h>
#include <boost/circular_buffer.hpp>
#include <algorithm>
#include <numeric>
#include <viterbi_detector.h>
#include <string.h>
#include <iostream>
#include <iomanip>
#include <boost/scoped_ptr.hpp>
#include <sch.h>
#include "receiver_impl.h"
#include <grgsm/endian.h>
//files included for debuging
//#include "plotting/plotting.hpp"
//#include <pthread.h>
#define SYNC_SEARCH_RANGE 30
namespace gr
{
namespace gsm
{
typedef std::list<float> list_float;
typedef std::vector<float> vector_float;
typedef boost::circular_buffer<float> circular_buffer_float;
receiver::sptr
receiver::make(int osr, const std::vector<int> &cell_allocation, const std::vector<int> &tseq_nums)
{
return gnuradio::get_initial_sptr
(new receiver_impl(osr, cell_allocation, tseq_nums));
}
/*
* The private constructor
*/
receiver_impl::receiver_impl(int osr, const std::vector<int> &cell_allocation, const std::vector<int> &tseq_nums)
: gr::sync_block("receiver",
gr::io_signature::make(1, -1, sizeof(gr_complex)),
gr::io_signature::make(0, 0, 0)),
d_OSR(osr),
d_chan_imp_length(CHAN_IMP_RESP_LENGTH),
d_counter(0),
d_fcch_start_pos(0),
d_freq_offset_setting(0),
d_state(fcch_search),
d_burst_nr(osr),
d_failed_sch(0),
d_signal_dbm(-120),
d_tseq_nums(tseq_nums),
d_cell_allocation(cell_allocation)
{
int i;
//don't send samples to the receiver until there are at least samples for one
set_output_multiple(floor((TS_BITS + 2 * GUARD_PERIOD) * d_OSR)); // burst and two gurad periods (one gurard period is an arbitrary overlap)
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++)
{
gr_complex startpoint = (train_seq[i][0]==0) ? gr_complex(1.0, 0.0) : gr_complex(-1.0, 0.0); //if first bit of the seqeunce ==0 first symbol ==1
//if first bit of the seqeunce ==1 first symbol ==-1
gmsk_mapper(train_seq[i], N_TRAIN_BITS, d_norm_training_seq[i], startpoint);
}
message_port_register_out(pmt::mp("C0"));
message_port_register_out(pmt::mp("CX"));
message_port_register_out(pmt::mp("measurements"));
configure_receiver(); //configure the receiver - tell it where to find which burst type
}
/*
* Our virtual destructor.
*/
receiver_impl::~receiver_impl()
{
}
int
receiver_impl::work(int noutput_items,
gr_vector_const_void_star &input_items,
gr_vector_void_star &output_items)
{
// std::vector<const gr_complex *> iii = (std::vector<const gr_complex *>) input_items; // jak zrobić to rzutowanie poprawnie
gr_complex * input = (gr_complex *) input_items[0];
std::vector<tag_t> freq_offset_tags;
uint64_t start = nitems_read(0);
uint64_t stop = start + noutput_items;
pmt::pmt_t key = pmt::string_to_symbol("setting_freq_offset");
get_tags_in_range(freq_offset_tags, 0, start, stop, key);
bool freq_offset_tag_in_fcch = false;
uint64_t tag_offset=-1; //-1 - just some clearly invalid value
if(!freq_offset_tags.empty()){
tag_t freq_offset_tag = freq_offset_tags[0];
tag_offset = freq_offset_tag.offset - start;
burst_type b_type = d_channel_conf.get_burst_type(d_burst_nr);
if(d_state == synchronized && b_type == fcch_burst){
uint64_t last_sample_nr = ceil((GUARD_PERIOD + 2.0 * TAIL_BITS + 156.25) * d_OSR) + 1;
if(tag_offset < last_sample_nr){
freq_offset_tag_in_fcch = true;
}
d_freq_offset_setting = pmt::to_double(freq_offset_tag.value);
} else {
d_freq_offset_setting = pmt::to_double(freq_offset_tag.value);
}
}
switch (d_state)
{
//bootstrapping
case fcch_search:
{
double freq_offset_tmp;
if (find_fcch_burst(input, noutput_items,freq_offset_tmp))
{
pmt::pmt_t msg = pmt::make_tuple(pmt::mp("freq_offset"),pmt::from_double(freq_offset_tmp-d_freq_offset_setting),pmt::mp("fcch_search"));
message_port_pub(pmt::mp("measurements"), msg);
d_state = sch_search;
}
else
{
d_state = fcch_search;
}
break;
}
case sch_search:
{
vector_complex channel_imp_resp(CHAN_IMP_RESP_LENGTH*d_OSR);
int t1, t2, t3;
int burst_start = 0;
unsigned char output_binary[BURST_SIZE];
if (reach_sch_burst(noutput_items)) //wait for a SCH burst
{
burst_start = get_sch_chan_imp_resp(input, &channel_imp_resp[0]); //get channel impulse response from it
detect_burst(input, &channel_imp_resp[0], burst_start, output_binary); //detect bits using MLSE detection
if (decode_sch(&output_binary[3], &t1, &t2, &t3, &d_ncc, &d_bcc) == 0) //decode SCH burst
{
d_burst_nr.set(t1, t2, t3, 0); //set counter of bursts value
d_burst_nr++;
consume_each(burst_start + BURST_SIZE * d_OSR + 4*d_OSR); //consume samples up to next guard period
d_state = synchronized;
}
else
{
d_state = fcch_search; //if there is error in the sch burst go back to fcch search phase
}
}
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:
{
vector_complex channel_imp_resp(CHAN_IMP_RESP_LENGTH*d_OSR);
int offset = 0;
int to_consume = 0;
unsigned char output_binary[BURST_SIZE];
burst_type b_type;
for(int input_nr=0; input_nr<d_cell_allocation.size(); input_nr++)
{
double signal_pwr = 0;
input = (gr_complex *)input_items[input_nr];
for(int ii=GUARD_PERIOD;ii<TS_BITS;ii++)
{
signal_pwr += abs(input[ii])*abs(input[ii]);
}
signal_pwr = signal_pwr/(TS_BITS);
d_signal_dbm = round(10*log10(signal_pwr/50));
if(input_nr==0){
d_c0_signal_dbm = d_signal_dbm;
}
if(input_nr==0) //for c0 channel burst type is controlled by channel configuration
{
b_type = d_channel_conf.get_burst_type(d_burst_nr); //get burst type for given burst number
}
else
{
b_type = normal_or_noise; //for the rest it can be only normal burst or noise (at least at this moment of development)
}
switch (b_type)
{
case fcch_burst: //if it's FCCH burst
{
const unsigned first_sample = ceil((GUARD_PERIOD + 2 * TAIL_BITS) * d_OSR) + 1;
const unsigned last_sample = first_sample + USEFUL_BITS * d_OSR - TAIL_BITS * d_OSR;
double freq_offset_tmp = compute_freq_offset(input, first_sample, last_sample); //extract frequency offset from it
send_burst(d_burst_nr, fc_fb, GSMTAP_BURST_FCCH, input_nr);
pmt::pmt_t msg = pmt::make_tuple(pmt::mp("freq_offset"),pmt::from_double(freq_offset_tmp-d_freq_offset_setting),pmt::mp("synchronized"));
message_port_pub(pmt::mp("measurements"), msg);
break;
}
case sch_burst: //if it's SCH burst
{
int t1, t2, t3, d_ncc, d_bcc;
d_c0_burst_start = get_sch_chan_imp_resp(input, &channel_imp_resp[0]); //get channel impulse response
detect_burst(input, &channel_imp_resp[0], d_c0_burst_start, output_binary); //MLSE detection of bits
send_burst(d_burst_nr, output_binary, GSMTAP_BURST_SCH, input_nr);
if (decode_sch(&output_binary[3], &t1, &t2, &t3, &d_ncc, &d_bcc) == 0) //and decode SCH data
{
// d_burst_nr.set(t1, t2, t3, 0); //but only to check if burst_start value is correct
d_failed_sch = 0;
offset = d_c0_burst_start - floor((GUARD_PERIOD) * d_OSR); //compute offset from burst_start - burst should start after a guard period
to_consume += offset; //adjust with offset number of samples to be consumed
}
else
{
d_failed_sch++;
if (d_failed_sch >= MAX_SCH_ERRORS)
{
d_state = fcch_search;
pmt::pmt_t msg = pmt::make_tuple(pmt::mp("freq_offset"),pmt::from_double(0.0),pmt::mp("sync_loss"));
message_port_pub(pmt::mp("measurements"), msg);
//DCOUT("Re-Synchronization!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!");
}
}
break;
}
case normal_burst:
{
float normal_corr_max; //if it's normal burst
d_c0_burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], &normal_corr_max, d_bcc); //get channel impulse response for given training sequence number - d_bcc
detect_burst(input, &channel_imp_resp[0], d_c0_burst_start, output_binary); //MLSE detection of bits
send_burst(d_burst_nr, output_binary, GSMTAP_BURST_NORMAL, input_nr);
break;
}
case dummy_or_normal:
{
unsigned int normal_burst_start, dummy_burst_start;
float dummy_corr_max, normal_corr_max;
dummy_burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], &dummy_corr_max, TS_DUMMY);
normal_burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], &normal_corr_max, d_bcc);
if (normal_corr_max > dummy_corr_max)
{
d_c0_burst_start = normal_burst_start;
detect_burst(input, &channel_imp_resp[0], normal_burst_start, output_binary);
send_burst(d_burst_nr, output_binary, GSMTAP_BURST_NORMAL, input_nr);
}
else
{
d_c0_burst_start = dummy_burst_start;
send_burst(d_burst_nr, dummy_burst, GSMTAP_BURST_DUMMY, input_nr);
}
break;
}
case rach_burst:
break;
case dummy:
send_burst(d_burst_nr, dummy_burst, GSMTAP_BURST_DUMMY, input_nr);
break;
case normal_or_noise:
{
unsigned int burst_start;
float normal_corr_max_tmp;
float normal_corr_max=-1e6;
int max_tn;
std::vector<gr_complex> v(input, input + noutput_items);
if(d_signal_dbm>=d_c0_signal_dbm-13)
{
if(d_tseq_nums.size()==0) //there is no information about training sequence
{ //however the receiver can detect it
get_norm_chan_imp_resp(input, &channel_imp_resp[0], &normal_corr_max, 0);
float ts_max=normal_corr_max; //with use of a very simple algorithm based on finding
int ts_max_num=0; //maximum correlation
for(int ss=1; ss<=7; ss++)
{
get_norm_chan_imp_resp(input, &channel_imp_resp[0], &normal_corr_max, ss);
if(ts_max<normal_corr_max)
{
ts_max = normal_corr_max;
ts_max_num = ss;
}
}
d_tseq_nums.push_back(ts_max_num);
}
int tseq_num;
if(input_nr<=d_tseq_nums.size()){
tseq_num = d_tseq_nums[input_nr-1];
} else {
tseq_num = d_tseq_nums.back();
}
burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], &normal_corr_max, tseq_num);
// if(abs(d_c0_burst_start-burst_start)<=2){ //unused check/filter based on timing
if((normal_corr_max/sqrt(signal_pwr))>=0.9){
detect_burst(input, &channel_imp_resp[0], burst_start, output_binary);
send_burst(d_burst_nr, output_binary, GSMTAP_BURST_NORMAL, input_nr);
}
}
break;
}
case empty: //if it's empty burst
break; //do nothing
}
if(input_nr==0)
{
d_burst_nr++; //go to next burst
to_consume += TS_BITS * d_OSR + d_burst_nr.get_offset(); //consume samples of the burst up to next guard period
}
if(input_nr==input_items.size()-1)
{
consume_each(to_consume);
}
//and add offset which is introduced by
//0.25 fractional part of a guard period
}
}
break;
}
return 0;
}
bool receiver_impl::find_fcch_burst(const gr_complex *input, const int nitems, double & computed_freq_offset)
{
circular_buffer_float phase_diff_buffer(FCCH_HITS_NEEDED * d_OSR); //circular buffer used to scan throug signal to find
//best match for FCCH burst
float phase_diff = 0;
gr_complex conjprod;
int start_pos = -1;
int hit_count = 0;
int miss_count = 0;
float min_phase_diff;
float max_phase_diff;
double best_sum = 0;
float lowest_max_min_diff = 99999;
int to_consume = 0;
int sample_number = 0;
bool end = false;
bool result = false;
circular_buffer_float::iterator buffer_iter;
/**@name Possible states of FCCH search algorithm*/
//@{
enum states
{
init, ///< initialize variables
search, ///< search for positive samples
found_something, ///< search for FCCH and the best position of it
fcch_found, ///< when FCCH was found
search_fail ///< when there is no FCCH in the input vector
} fcch_search_state;
//@}
fcch_search_state = init;
while (!end)
{
switch (fcch_search_state)
{
case init: //initialize variables
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: // search for positive samples
sample_number++;
if (sample_number > nitems - FCCH_HITS_NEEDED * d_OSR) //if it isn't possible to find FCCH because
{
//there's too few samples left to look into,
to_consume = sample_number; //don't do anything with those samples which are left
//and consume only those which were checked
fcch_search_state = search_fail;
}
else
{
phase_diff = compute_phase_diff(input[sample_number], input[sample_number-1]);
if (phase_diff > 0) //if a positive phase difference was found
{
to_consume = sample_number;
fcch_search_state = found_something; //switch to state in which searches for FCCH
}
else
{
fcch_search_state = search;
}
}
break;
case found_something: // search for FCCH and the best position of it
{
if (phase_diff > 0)
{
hit_count++; //positive phase differencies increases hits_count
}
else
{
miss_count++; //negative increases miss_count
}
if ((miss_count >= FCCH_MAX_MISSES * d_OSR) && (hit_count <= FCCH_HITS_NEEDED * d_OSR))
{
//if miss_count exceeds limit before hit_count
fcch_search_state = init; //go to 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))
{
//if hit_count and miss_count exceeds limit then FCCH was found
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; //store start pos
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; //store best value of phase offset sum
}
}
}
sample_number++;
if (sample_number >= nitems) //if there's no single sample left to check
{
fcch_search_state = search_fail;//FCCH search failed
continue;
}
phase_diff = compute_phase_diff(input[sample_number], input[sample_number-1]);
phase_diff_buffer.push_back(phase_diff);
fcch_search_state = found_something;
}
break;
case fcch_found:
{
to_consume = start_pos + FCCH_HITS_NEEDED * d_OSR + 1; //consume one FCCH burst
d_fcch_start_pos = d_counter + start_pos;
//compute frequency offset
double phase_offset = best_sum / FCCH_HITS_NEEDED;
double freq_offset = phase_offset * 1625000.0/6 / (2 * M_PI); //1625000.0/6 - GMSK symbol rate in GSM
computed_freq_offset = 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 receiver_impl::compute_freq_offset(const gr_complex * input, unsigned first_sample, unsigned last_sample)
{
double phase_sum = 0;
unsigned ii;
for (ii = first_sample; ii < last_sample; ii++)
{
double phase_diff = compute_phase_diff(input[ii], input[ii-1]) - (M_PI / 2) / d_OSR;
phase_sum += phase_diff;
}
double phase_offset = phase_sum / (last_sample - first_sample);
double freq_offset = phase_offset * 1625000.0 / (12.0 * M_PI);
return freq_offset;
}
inline float receiver_impl::compute_phase_diff(gr_complex val1, gr_complex val2)
{
gr_complex conjprod = val1 * conj(val2);
return fast_atan2f(imag(conjprod), real(conjprod));
}
bool receiver_impl::reach_sch_burst(const int nitems)
{
//it just consumes samples to get near to a SCH burst
int to_consume = 0;
bool result = false;
unsigned sample_nr_near_sch_start = d_fcch_start_pos + (FRAME_BITS - SAFETY_MARGIN) * d_OSR;
//consume samples until d_counter will be equal to sample_nr_near_sch_start
if (d_counter < sample_nr_near_sch_start)
{
if (d_counter + nitems >= sample_nr_near_sch_start)
{
to_consume = sample_nr_near_sch_start - d_counter;
}
else
{
to_consume = nitems;
}
result = false;
}
else
{
to_consume = 0;
result = true;
}
d_counter += to_consume;
consume_each(to_consume);
return result;
}
int receiver_impl::get_sch_chan_imp_resp(const gr_complex *input, 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 = 0;
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], N_SYNC_BITS - 10, &input[ii]);
correlation_buffer.push_back(correlation);
power_buffer.push_back(std::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 receiver_impl::detect_burst(const gr_complex * input, 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(&input[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);
}
}
void receiver_impl::gmsk_mapper(const unsigned char * input, int nitems, 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 < nitems; 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;
}
}
gr_complex receiver_impl::correlate_sequence(const gr_complex * sequence, int length, const gr_complex * input)
{
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[sample_number]);
}
result = result / gr_complex(length, 0);
return result;
}
//computes autocorrelation for positive arguments
inline void receiver_impl::autocorrelation(const gr_complex * input, gr_complex * out, int nitems)
{
int i, k;
for (k = nitems - 1; k >= 0; k--)
{
out[k] = gr_complex(0, 0);
for (i = k; i < nitems; i++)
{
out[k] += input[i] * conj(input[i-k]);
}
}
}
inline void receiver_impl::mafi(const gr_complex * input, int nitems, gr_complex * filter, int filter_length, gr_complex * output)
{
int ii = 0, n, a;
for (n = 0; n < nitems; n++)
{
a = n * d_OSR;
output[n] = 0;
ii = 0;
while (ii < filter_length)
{
if ((a + ii) >= nitems*d_OSR){
break;
}
output[n] += input[a+ii] * filter[ii];
ii++;
}
}
}
//especially computations of strongest_window_nr
int receiver_impl::get_norm_chan_imp_resp(const gr_complex *input, gr_complex * chan_imp_resp, float *corr_max, int bcc)
{
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 = 0;
float max_correlation = 0;
float energy = 0;
int search_center = (int)((TRAIN_POS + GUARD_PERIOD) * d_OSR);
int search_start_pos = search_center + 1 - 5*d_OSR;
// int search_start_pos = search_center - d_chan_imp_length * d_OSR;
int search_stop_pos = search_center + d_chan_imp_length * d_OSR + 5 * d_OSR;
for(int ii = search_start_pos; ii < search_stop_pos; ii++)
{
gr_complex correlation = correlate_sequence(&d_norm_training_seq[bcc][TRAIN_BEGINNING], N_TRAIN_BITS - 10, &input[ii]);
correlation_buffer.push_back(correlation);
power_buffer.push_back(std::pow(abs(correlation), 2));
}
// plot(power_buffer);
//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 - 2)*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()-((d_chan_imp_length)*d_OSR)) - window_energy_buffer.begin();
//strongest_window_nr = strongest_window_nr-d_OSR;
if(strongest_window_nr<0){
strongest_window_nr = 0;
}
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;
}
*corr_max = max_correlation;
//DCOUT("strongest_window_nr_new: " << strongest_window_nr);
burst_start = search_start_pos + strongest_window_nr - TRAIN_POS * d_OSR; //compute first sample posiiton which corresponds to the first sample of the impulse response
//DCOUT("burst_start: " << burst_start);
return burst_start;
}
void receiver_impl::send_burst(burst_counter burst_nr, const unsigned char * burst_binary, uint8_t burst_type, unsigned int input_nr)
{
boost::scoped_ptr<gsmtap_hdr> tap_header(new gsmtap_hdr());
tap_header->version = GSMTAP_VERSION;
tap_header->hdr_len = sizeof(gsmtap_hdr)/4;
tap_header->type = GSMTAP_TYPE_UM_BURST;
tap_header->timeslot = static_cast<uint8_t>(d_burst_nr.get_timeslot_nr());
tap_header->frame_number = htobe32(d_burst_nr.get_frame_nr());
tap_header->sub_type = burst_type;
tap_header->arfcn = htobe16(d_cell_allocation[input_nr]) ;
tap_header->signal_dbm = static_cast<int8_t>(d_signal_dbm);
tap_header->snr_db = 0;
int8_t header_plus_burst[sizeof(gsmtap_hdr)+BURST_SIZE];
memcpy(header_plus_burst, tap_header.get(), sizeof(gsmtap_hdr));
memcpy(header_plus_burst+sizeof(gsmtap_hdr), burst_binary, BURST_SIZE);
pmt::pmt_t blob_header_plus_burst = pmt::make_blob(header_plus_burst,sizeof(gsmtap_hdr)+BURST_SIZE);
pmt::pmt_t msg = pmt::cons(pmt::PMT_NIL, blob_header_plus_burst);
if(input_nr==0){
message_port_pub(pmt::mp("C0"), msg);
} else {
message_port_pub(pmt::mp("CX"), msg);
}
}
void receiver_impl::configure_receiver()
{
d_channel_conf.set_multiframe_type(TIMESLOT0, multiframe_51);
d_channel_conf.set_burst_types(TIMESLOT0, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
d_channel_conf.set_burst_types(TIMESLOT0, TEST_CCH_FRAMES, sizeof(TEST_CCH_FRAMES) / sizeof(unsigned), dummy_or_normal);
d_channel_conf.set_burst_types(TIMESLOT0, FCCH_FRAMES, sizeof(FCCH_FRAMES) / sizeof(unsigned), fcch_burst);
d_channel_conf.set_burst_types(TIMESLOT0, SCH_FRAMES, sizeof(SCH_FRAMES) / sizeof(unsigned), sch_burst);
d_channel_conf.set_multiframe_type(TIMESLOT1, multiframe_51);
d_channel_conf.set_burst_types(TIMESLOT1, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
d_channel_conf.set_multiframe_type(TIMESLOT2, multiframe_51);
d_channel_conf.set_burst_types(TIMESLOT2, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
d_channel_conf.set_multiframe_type(TIMESLOT3, multiframe_51);
d_channel_conf.set_burst_types(TIMESLOT3, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
d_channel_conf.set_multiframe_type(TIMESLOT4, multiframe_51);
d_channel_conf.set_burst_types(TIMESLOT4, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
d_channel_conf.set_multiframe_type(TIMESLOT5, multiframe_51);
d_channel_conf.set_burst_types(TIMESLOT5, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
d_channel_conf.set_multiframe_type(TIMESLOT6, multiframe_51);
d_channel_conf.set_burst_types(TIMESLOT6, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
d_channel_conf.set_multiframe_type(TIMESLOT7, multiframe_51);
d_channel_conf.set_burst_types(TIMESLOT7, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
}
void receiver_impl::set_cell_allocation(const std::vector<int> &cell_allocation)
{
d_cell_allocation = cell_allocation;
}
void receiver_impl::set_tseq_nums(const std::vector<int> & tseq_nums)
{
d_tseq_nums = tseq_nums;
}
void receiver_impl::reset()
{
d_state = fcch_search;
}
} /* namespace gsm */
} /* namespace gr */
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