receiver_impl.h
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/* -*- c++ -*- */
/*
* @file
* @author (C) 2009-2017 by 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.
*/
#ifndef INCLUDED_GSM_RECEIVER_IMPL_H
#define INCLUDED_GSM_RECEIVER_IMPL_H
#include <gsm/receiver/receiver.h>
#include <gsm/gsmtap.h>
#include <gsm/gsm_constants.h>
#include <receiver_config.h>
#include <vector>
#include "time_sample_ref.h"
namespace gr {
namespace gsm {
class receiver_impl : public receiver
{
private:
unsigned int d_samples_consumed;
bool d_rx_time_received;
time_sample_ref d_time_samp_ref;
int d_c0_burst_start;
float d_c0_signal_dbm;
/**@name Configuration of the receiver */
//@{
const int d_OSR; ///< oversampling ratio
bool d_process_uplink;
const int d_chan_imp_length; ///< channel impulse length
float d_signal_dbm;
std::vector<int> d_tseq_nums; ///< stores training sequence numbers for channels different than C0
std::vector<int> d_cell_allocation; ///< stores cell allocation - absolute rf channel numbers (ARFCNs) assigned to the given cell. The variable should at least contain C0 channel number.
//@}
gr_complex d_sch_training_seq[N_SYNC_BITS]; ///<encoded training sequence of a SCH burst
gr_complex d_norm_training_seq[TRAIN_SEQ_NUM][N_TRAIN_BITS]; ///<encoded training sequences of a normal and dummy burst
float d_last_time;
/** Counts samples consumed by the receiver
*
* It is used in beetween find_fcch_burst and reach_sch_burst calls.
* My intention was to synchronize this counter with some internal sample
* counter of the USRP. Simple access to such USRP's counter isn't possible
* so this variable isn't used in the "synchronized" state of the receiver yet.
*/
unsigned d_counter;
/**@name Variables used to store result of the find_fcch_burst fuction */
//@{
bool d_freq_offset_tag_in_fcch; ///< frequency offset tag presence
unsigned d_fcch_start_pos; ///< position of the first sample of the fcch burst
float d_freq_offset_setting; ///< frequency offset set in frequency shifter located upstream
//@}
std::list<double> d_freq_offset_vals;
/**@name Identifiers of the BTS extracted from the SCH burst */
//@{
int d_ncc; ///< network color code
int d_bcc; ///< base station color code
//@}
/**@name Internal state of the gsm receiver */
//@{
enum states {
fcch_search, sch_search, // synchronization search part
synchronized // receiver is synchronized in this state
} d_state;
//@}
/**@name Variables which make internal state in the "synchronized" state */
//@{
burst_counter d_burst_nr; ///< frame number and timeslot number
channel_configuration d_channel_conf; ///< mapping of burst_counter to burst_type
//@}
unsigned d_failed_sch; ///< number of subsequent erroneous SCH bursts
/** Function whis is used to search a FCCH burst and to compute frequency offset before
* "synchronized" state of the receiver
*
* @param input vector with input signal
* @param nitems number of samples in the input vector
* @return
*/
bool find_fcch_burst(const gr_complex *input, const int nitems, double & computed_freq_offset);
/** Computes frequency offset from FCCH burst samples
*
* @param[in] input vector with input samples
* @param[in] first_sample number of the first sample of the FCCH busrt
* @param[in] last_sample number of the last sample of the FCCH busrt
* @param[out] computed_freq_offset contains frequency offset estimate if FCCH burst was located
* @return true if frequency offset was faound
*/
double compute_freq_offset(const gr_complex * input, unsigned first_sample, unsigned last_sample);
/** Computes angle between two complex numbers
*
* @param val1 first complex number
* @param val2 second complex number
* @return
*/
inline float compute_phase_diff(gr_complex val1, gr_complex val2);
/** Function whis is used to get near to SCH burst
*
* @param nitems number of samples in the gsm_receiver's buffer
* @return true if SCH burst is near, false otherwise
*/
bool reach_sch_burst(const int nitems);
/** Extracts channel impulse response from a SCH burst and computes first sample number of this burst
*
* @param input vector with input samples
* @param chan_imp_resp complex vector where channel impulse response will be stored
* @return number of first sample of the burst
*/
int get_sch_chan_imp_resp(const gr_complex *input, gr_complex * chan_imp_resp);
/** MLSE detection of a burst bits
*
* Detects bits of burst using viterbi algorithm.
* @param input vector with input samples
* @param chan_imp_resp vector with the channel impulse response
* @param burst_start number of the first sample of the burst
* @param output_binary vector with output bits
*/
void detect_burst(const gr_complex * input, gr_complex * chan_imp_resp, int burst_start, unsigned char * output_binary);
/** Encodes differentially input bits and maps them into MSK states
*
* @param input vector with input bits
* @param nitems number of samples in the "input" vector
* @param gmsk_output bits mapped into MSK states
* @param start_point first state
*/
void gmsk_mapper(const unsigned char * input, int nitems, gr_complex * gmsk_output, gr_complex start_point);
/** Correlates MSK mapped sequence with input signal
*
* @param sequence MKS mapped sequence
* @param length length of the sequence
* @param input_signal vector with input samples
* @return correlation value
*/
gr_complex correlate_sequence(const gr_complex * sequence, int length, const gr_complex * input);
/** Computes autocorrelation of input vector for positive arguments
*
* @param input vector with input samples
* @param out output vector
* @param nitems length of the input vector
*/
inline void autocorrelation(const gr_complex * input, gr_complex * out, int nitems);
/** Filters input signal through channel impulse response
*
* @param input vector with input samples
* @param nitems number of samples to pass through filter
* @param filter filter taps - channel impulse response
* @param filter_length nember of filter taps
* @param output vector with filtered samples
*/
inline void mafi(const gr_complex * input, int nitems, gr_complex * filter, int filter_length, gr_complex * output);
/** Extracts channel impulse response from a normal burst and computes first sample number of this burst
*
* @param input vector with input samples
* @param chan_imp_resp complex vector where channel impulse response will be stored
* @param search_range possible absolute offset of a channel impulse response start
* @param bcc base station color code - number of a training sequence
* @return first sample number of normal burst
*/
int get_norm_chan_imp_resp(const gr_complex *input, gr_complex * chan_imp_resp, float *corr_max, int bcc);
/**
* Sends burst through a C0 (for burst from C0 channel) or Cx (for other bursts) message port
*
* @param burst_nr - frame number of the burst
* @param burst_binary - content of the burst
* @b_type - type of the burst
*/
void send_burst(burst_counter burst_nr, const unsigned char * burst_binary, uint8_t burst_type, size_t input_nr, unsigned int burst_start=-1);
/**
* Configures burst types in different channels
*/
void configure_receiver();
/* State machine handlers */
void fcch_search_handler(gr_complex *input, int noutput_items);
void sch_search_handler(gr_complex *input, int noutput_items);
void synchronized_handler(gr_complex *input,
gr_vector_const_void_star &input_items, int noutput_items);
public:
receiver_impl(int osr, const std::vector<int> &cell_allocation, const std::vector<int> &tseq_nums, bool process_uplink);
~receiver_impl();
int work(int noutput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items);
virtual void set_cell_allocation(const std::vector<int> &cell_allocation);
virtual void set_tseq_nums(const std::vector<int> & tseq_nums);
virtual void reset();
};
} // namespace gsm
} // namespace gr
#endif /* INCLUDED_GSM_RECEIVER_IMPL_H */
burst_counter
Definition receiver_config.h:67
channel_configuration
Definition receiver_config.h:131
gr::gsm::receiver_impl
Definition receiver_impl.h:36
gr::gsm::receiver_impl::reset
virtual void reset()
gr::gsm::receiver_impl::work
int work(int noutput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
gr::gsm::receiver_impl::set_tseq_nums
virtual void set_tseq_nums(const std::vector< int > &tseq_nums)
gr::gsm::receiver_impl::receiver_impl
receiver_impl(int osr, const std::vector< int > &cell_allocation, const std::vector< int > &tseq_nums, bool process_uplink)
gr::gsm::receiver_impl::~receiver_impl
~receiver_impl()
gr::gsm::receiver_impl::set_cell_allocation
virtual void set_cell_allocation(const std::vector< int > &cell_allocation)
gr::gsm::receiver
<+description of block+>
Definition receiver.h:41
gr::gsm::time_sample_ref
Definition time_sample_ref.h:35
gsm_constants.h
TRAIN_SEQ_NUM
#define TRAIN_SEQ_NUM
Definition gsm_constants.h:93
N_TRAIN_BITS
#define N_TRAIN_BITS
Definition gsm_constants.h:36
burst_type
burst_type
Definition gsm_constants.h:63
N_SYNC_BITS
#define N_SYNC_BITS
Definition gsm_constants.h:37
gsmtap.h
gr
Definition constants.h:29
receiver.h
receiver_config.h
time_sample_ref.h