Initial commit - gsm-receiver with removed quick hacks
diff --git a/lib/receiver_impl.cc b/lib/receiver_impl.cc
new file mode 100644
index 0000000..689079b
--- /dev/null
+++ b/lib/receiver_impl.cc
@@ -0,0 +1,770 @@
+/* -*- c++ -*- */
+/*
+ * Copyright 2014 <+YOU OR YOUR COMPANY+>.
+ *
+ * This 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.
+ *
+ * This software 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 this software; 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 "receiver_impl.h"
+
+#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 <sch.h>
+#include <iostream>
+#include <iomanip>
+
+#include <assert.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(feval_dd * tuner, int osr)
+ {
+ return gnuradio::get_initial_sptr
+ (new receiver_impl(tuner, osr));
+ }
+
+ /*
+ * The private constructor
+ */
+ receiver_impl::receiver_impl(feval_dd * tuner, int osr)
+ : gr::block("receiver",
+ gr::io_signature::make(1, 1, sizeof(gr_complex)),
+ gr::io_signature::make(0, 1, 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_failed_sch(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++) {
+ gr_complex startpoint;
+ if (i == 6 || i == 7) { //this is nasty hack
+ startpoint = gr_complex(-1.0, 0.0); //if I don't change it here all bits of normal bursts for BTSes with bcc=6 will have reversed values
+ } else {
+ startpoint = gr_complex(1.0, 0.0); //I've checked this hack for bcc==0,1,2,3,4,6
+ } //I don't know what about bcc==5 and 7 yet
+ //TODO:find source of this situation - this is purely mathematical problem I guess
+
+ gmsk_mapper(train_seq[i], N_TRAIN_BITS, d_norm_training_seq[i], startpoint);
+ }
+ }
+
+ /*
+ * Our virtual destructor.
+ */
+ receiver_impl::~receiver_impl()
+ {
+ }
+
+ void receiver_impl::forecast(int noutput_items, gr_vector_int &ninput_items_required)
+ {
+ ninput_items_required[0] = noutput_items * floor((TS_BITS + 2 * GUARD_PERIOD) * d_OSR);
+ }
+
+
+ int
+ receiver_impl::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 *input = (const gr_complex *) input_items[0];
+ //float *out = (float *) output_items[0];
+ int produced_out = 0; //how many output elements were produced - this isn't used yet
+ //probably the gsm receiver will be changed into sink so this variable won't be necessary
+ switch (d_state) {
+ //bootstrapping
+ case first_fcch_search:
+ if (find_fcch_burst(input, ninput_items[0])) { //find frequency correction burst in the input buffer
+ set_frequency(d_freq_offset); //if fcch search is successful set frequency offset
+ //produced_out = 0;
+ d_state = next_fcch_search;
+ } else {
+ //produced_out = 0;
+ d_state = first_fcch_search;
+ }
+ break;
+
+ case next_fcch_search: { //this state is used because it takes some time (a bunch of buffered samples)
+ COUT("fcch");
+ float prev_freq_offset = d_freq_offset; //before previous set_frequqency cause change
+ if (find_fcch_burst(input, ninput_items[0])) {
+ if (abs(prev_freq_offset - d_freq_offset) > FCCH_MAX_FREQ_OFFSET) {
+ set_frequency(d_freq_offset); //call set_frequncy only frequency offset change is greater than some value
+ }
+ //produced_out = 0;
+ d_state = sch_search;
+ } else {
+ //produced_out = 0;
+ d_state = next_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(ninput_items[0])) { //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
+ COUT("sch burst_start: " << burst_start);
+ COUT("bcc: " << d_bcc << " ncc: " << d_ncc << " t1: " << t1 << " t2: " << t2 << " t3: " << t3);
+ d_burst_nr.set(t1, t2, t3, 0); //set counter of bursts value
+
+ //configure the receiver - tell him where to find which burst type
+ d_channel_conf.set_multiframe_type(TIMESLOT0, multiframe_51); //in the timeslot nr.0 bursts changes according to t3 counter
+ configure_receiver();//TODO: this shouldn't be here - remove it when gsm receiver's interface will be ready
+ d_channel_conf.set_burst_types(TIMESLOT0, FCCH_FRAMES, sizeof(FCCH_FRAMES) / sizeof(unsigned), fcch_burst); //tell where to find fcch bursts
+ d_channel_conf.set_burst_types(TIMESLOT0, SCH_FRAMES, sizeof(SCH_FRAMES) / sizeof(unsigned), sch_burst); //sch bursts
+ d_channel_conf.set_burst_types(TIMESLOT0, BCCH_FRAMES, sizeof(BCCH_FRAMES) / sizeof(unsigned), normal_burst);//!and maybe normal bursts of the BCCH logical channel
+ d_burst_nr++;
+
+ consume_each(burst_start + BURST_SIZE * d_OSR); //consume samples up to next guard period
+ d_state = synchronized;
+ } else {
+ d_state = next_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 burst_start;
+ int offset = 0;
+ int to_consume = 0;
+ unsigned char output_binary[BURST_SIZE];
+
+ burst_type b_type = d_channel_conf.get_burst_type(d_burst_nr); //get burst type for given burst number
+
+ 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 = compute_freq_offset(input, first_sample, last_sample); //extract frequency offset from it
+
+ d_freq_offset_vals.push_front(freq_offset);
+ //process_normal_burst(d_burst_nr, fc_fb);
+ if (d_freq_offset_vals.size() >= 10) {
+ double sum = std::accumulate(d_freq_offset_vals.begin(), d_freq_offset_vals.end(), 0);
+ double mean_offset = sum / d_freq_offset_vals.size(); //compute mean
+ d_freq_offset_vals.clear();
+ if (abs(mean_offset) > FCCH_MAX_FREQ_OFFSET) {
+ d_freq_offset -= mean_offset; //and adjust frequency if it have changed beyond
+ set_frequency(d_freq_offset); //some limit
+ DCOUT("mean_offset: " << mean_offset);
+ DCOUT("Adjusting frequency, new frequency offset: " << d_freq_offset << "\n");
+ }
+ }
+ }
+ break;
+ case sch_burst: { //if it's SCH burst
+ int t1, t2, t3, d_ncc, d_bcc;
+ burst_start = get_sch_chan_imp_resp(input, &channel_imp_resp[0]); //get channel impulse response
+ detect_burst(input, &channel_imp_resp[0], burst_start, output_binary); //MLSE detection of bits
+ //process_normal_burst(d_burst_nr, output_binary);
+ 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;
+ DCOUT("bcc: " << d_bcc << " ncc: " << d_ncc << " t1: " << t1 << " t2: " << t2 << " t3: " << t3);
+ offset = burst_start - floor((GUARD_PERIOD) * d_OSR); //compute offset from burst_start - burst should start after a guard period
+ DCOUT(offset);
+ 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 = next_fcch_search; //TODO: this isn't good, the receiver is going wild when it goes back to next_fcch_search from here
+ // d_freq_offset_vals.clear();
+ DCOUT("many sch decoding errors");
+ }
+ }
+ }
+ break;
+
+ case normal_burst: //if it's normal burst
+ burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], d_bcc); //get channel impulse response for given training sequence number - d_bcc
+ detect_burst(input, &channel_imp_resp[0], burst_start, output_binary); //MLSE detection of bits
+ process_normal_burst(d_burst_nr, output_binary); //TODO: this shouldn't be here - remove it when gsm receiver's interface will be ready
+ break;
+
+ case dummy_or_normal: {
+ burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], TS_DUMMY);
+ detect_burst(input, &channel_imp_resp[0], burst_start, output_binary);
+
+ std::vector<unsigned char> v(20);
+ std::vector<unsigned char>::iterator it;
+ it = std::set_difference(output_binary + TRAIN_POS, output_binary + TRAIN_POS + 16, &train_seq[TS_DUMMY][5], &train_seq[TS_DUMMY][21], v.begin());
+ int different_bits = (it - v.begin());
+
+ if (different_bits > 2) {
+ burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], d_bcc);
+ detect_burst(input, &channel_imp_resp[0], burst_start, output_binary);
+ //if (!output_binary[0] && !output_binary[1] && !output_binary[2]) {
+ COUT("Normal burst");
+ process_normal_burst(d_burst_nr, output_binary); //TODO: this shouldn't be here - remove it when gsm receiver's interface will be ready
+ //}
+ } else {
+ //process_normal_burst(d_burst_nr, dummy_burst);
+ }
+ }
+ case rach_burst:
+ //implementation of this channel isn't possible in current gsm_receiver
+ //it would take some realtime processing, counter of samples from USRP to
+ //stay synchronized with this device and possibility to switch frequency from uplink
+ //to C0 (where sch is) back and forth
+
+ break;
+ case dummy: //if it's dummy
+ burst_start = get_norm_chan_imp_resp(input, &channel_imp_resp[0], TS_DUMMY); //read dummy
+ detect_burst(input, &channel_imp_resp[0], burst_start, output_binary); // but as far as I know it's pointless
+ break;
+ case empty: //if it's empty burst
+ break; //do nothing
+ }
+
+ 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
+ //and add offset which is introduced by
+ //0.25 fractional part of a guard period
+ //burst_number computes this offset
+ //but choice of this class to do this was random
+ consume_each(to_consume);
+ }
+ break;
+ }
+
+ return produced_out;
+ }
+
+
+ bool receiver_impl::find_fcch_burst(const gr_complex *input, const int nitems)
+ {
+ 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: {
+ DCOUT("fcch found on position: " << d_counter + start_pos);
+ 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 / (12.0 * M_PI);
+ 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 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;
+ }
+
+ void receiver_impl::set_frequency(double freq_offset)
+ {
+ d_tuner->calleval(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);
+ }
+ }
+
+ //TODO consider placing this funtion in a separate class for signal processing
+ 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;
+ }
+ }
+
+ //TODO consider use of some generalized function for correlation and placing it in a separate class for signal processing
+ 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
+ //TODO consider placing this funtion in a separate class for signal processing
+ 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]);
+ }
+ }
+ }
+
+ //TODO consider use of some generalized function for filtering and placing it in a separate class for signal processing
+ 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++;
+ }
+ }
+ }
+
+ //TODO: get_norm_chan_imp_resp is similar to get_sch_chan_imp_resp - consider joining this two functions
+ //TODO: this is place where most errors are introduced and can be corrected by improvements to this fuction
+ //especially computations of strongest_window_nr
+ int receiver_impl::get_norm_chan_imp_resp(const gr_complex *input, gr_complex * chan_imp_resp, 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;
+ // int search_start_pos = search_center - d_chan_imp_length * d_OSR;
+ int search_stop_pos = search_center + d_chan_imp_length * d_OSR + 2 * 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));
+ }
+
+ //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++) {
+ // 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);
+ }
+ //!why doesn't this work
+ int strongest_window_nr_new = max_element(window_energy_buffer.begin(), window_energy_buffer.end()) - window_energy_buffer.begin();
+ strongest_window_nr = 3; //! so I have to override it here
+
+ 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;
+ }
+ // We want to use the first sample of the impulseresponse, and the
+ // corresponding samples of the received signal.
+ // the variable sync_w should contain the beginning of the used part of
+ // training sequence, which is 3+57+1+6=67 bits into the burst. That is
+ // we have that sync_t16 equals first sample in bit number 67.
+
+ burst_start = search_start_pos + chan_imp_resp_center + strongest_window_nr - TRAIN_POS * d_OSR;
+
+ // GMSK modulator introduces ISI - each bit is expanded for 3*Tb
+ // and it's maximum value is in the last bit period, so burst starts
+ // 2*Tb earlier
+ burst_start -= 2 * d_OSR;
+ burst_start += 2;
+ COUT("Poczatek ###############################");
+ std::cout << " burst_start: " << burst_start << " center: " << ((float)(search_start_pos + strongest_window_nr + chan_imp_resp_center)) / d_OSR << " stronegest window nr: " << strongest_window_nr << "\n";
+ COUT("burst_start_new: " << (search_start_pos + strongest_window_nr_new - TRAIN_POS * d_OSR));
+ burst_start=(search_start_pos + strongest_window_nr_new - TRAIN_POS * d_OSR)
+ return burst_start;
+ }
+
+
+ void receiver_impl::process_normal_burst(burst_counter burst_nr, const unsigned char * burst_binary)
+ {
+ int ii;
+ //std::cout << "fn:" <<burst_nr.get_frame_nr() << " ts" << burst_nr.get_timeslot_nr() << " ";
+ for(ii=0;ii<148;ii++){
+ std::cout << std::setprecision(1) << static_cast<int>(burst_binary[ii]);
+ }
+ std::cout << std::endl;
+ }
+ //TODO: this shouldn't be here also - the same reason
+ void receiver_impl::configure_receiver()
+ {
+ d_channel_conf.set_multiframe_type(TSC0, multiframe_51);
+ d_channel_conf.set_burst_types(TIMESLOT0, TEST51, sizeof(TEST51) / sizeof(unsigned), dummy_or_normal);
+
+ d_channel_conf.set_burst_types(TSC0, TEST_CCH_FRAMES, sizeof(TEST_CCH_FRAMES) / sizeof(unsigned), dummy_or_normal);
+ d_channel_conf.set_burst_types(TSC0, FCCH_FRAMES, sizeof(FCCH_FRAMES) / sizeof(unsigned), fcch_burst);
+
+ // d_channel_conf.set_multiframe_type(TIMESLOT1, multiframe_26);
+ // d_channel_conf.set_burst_types(TIMESLOT1, TRAFFIC_CHANNEL_F, sizeof(TRAFFIC_CHANNEL_F) / sizeof(unsigned), dummy_or_normal);
+ // d_channel_conf.set_multiframe_type(TIMESLOT2, multiframe_26);
+ // d_channel_conf.set_burst_types(TIMESLOT2, TRAFFIC_CHANNEL_F, sizeof(TRAFFIC_CHANNEL_F) / sizeof(unsigned), dummy_or_normal);
+ // d_channel_conf.set_multiframe_type(TIMESLOT3, multiframe_26);
+ // d_channel_conf.set_burst_types(TIMESLOT3, TRAFFIC_CHANNEL_F, sizeof(TRAFFIC_CHANNEL_F) / sizeof(unsigned), dummy_or_normal);
+ // d_channel_conf.set_multiframe_type(TIMESLOT4, multiframe_26);
+ // d_channel_conf.set_burst_types(TIMESLOT4, TRAFFIC_CHANNEL_F, sizeof(TRAFFIC_CHANNEL_F) / sizeof(unsigned), dummy_or_normal);
+ // d_channel_conf.set_multiframe_type(TIMESLOT5, multiframe_26);
+ // d_channel_conf.set_burst_types(TIMESLOT5, TRAFFIC_CHANNEL_F, sizeof(TRAFFIC_CHANNEL_F) / sizeof(unsigned), dummy_or_normal);
+ // d_channel_conf.set_multiframe_type(TIMESLOT6, multiframe_26);
+ // d_channel_conf.set_burst_types(TIMESLOT6, TRAFFIC_CHANNEL_F, sizeof(TRAFFIC_CHANNEL_F) / sizeof(unsigned), dummy_or_normal);
+ // d_channel_conf.set_multiframe_type(TIMESLOT7, multiframe_26);
+ // d_channel_conf.set_burst_types(TIMESLOT7, TRAFFIC_CHANNEL_F, sizeof(TRAFFIC_CHANNEL_F) / sizeof(unsigned), dummy_or_normal);
+ 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);
+
+ }
+
+
+ } /* namespace gsm */
+} /* namespace gr */
+