GNU Radio's GSM Package
receiver_impl.h
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1/* -*- c++ -*- */
2/*
3 * @file
4 * @author (C) 2009-2017 by Piotr Krysik <ptrkrysik@gmail.com>
5 * @section LICENSE
6 *
7 * Gr-gsm is free software; you can redistribute it and/or modify
8 * it under the terms of the GNU General Public License as published by
9 * the Free Software Foundation; either version 3, or (at your option)
10 * any later version.
11 *
12 * Gr-gsm is distributed in the hope that it will be useful,
13 * but WITHOUT ANY WARRANTY; without even the implied warranty of
14 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
15 * GNU General Public License for more details.
16 *
17 * You should have received a copy of the GNU General Public License
18 * along with gr-gsm; see the file COPYING. If not, write to
19 * the Free Software Foundation, Inc., 51 Franklin Street,
20 * Boston, MA 02110-1301, USA.
21 */
22
23#ifndef INCLUDED_GSM_RECEIVER_IMPL_H
24#define INCLUDED_GSM_RECEIVER_IMPL_H
25
27#include <gsm/gsmtap.h>
28#include <gsm/gsm_constants.h>
29#include <receiver_config.h>
30#include <vector>
31#include "time_sample_ref.h"
32
33namespace gr {
34 namespace gsm {
35 class receiver_impl : public receiver
36 {
37 private:
38 unsigned int d_samples_consumed;
39 bool d_rx_time_received;
40 time_sample_ref d_time_samp_ref;
41 int d_c0_burst_start;
42 float d_c0_signal_dbm;
43
44 /**@name Configuration of the receiver */
45 //@{
46 const int d_OSR; ///< oversampling ratio
47 bool d_process_uplink;
48 const int d_chan_imp_length; ///< channel impulse length
49 float d_signal_dbm;
50 std::vector<int> d_tseq_nums; ///< stores training sequence numbers for channels different than C0
51 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.
52 //@}
53
54 gr_complex d_sch_training_seq[N_SYNC_BITS]; ///<encoded training sequence of a SCH burst
55 gr_complex d_norm_training_seq[TRAIN_SEQ_NUM][N_TRAIN_BITS]; ///<encoded training sequences of a normal and dummy burst
56
57 float d_last_time;
58
59 /** Counts samples consumed by the receiver
60 *
61 * It is used in beetween find_fcch_burst and reach_sch_burst calls.
62 * My intention was to synchronize this counter with some internal sample
63 * counter of the USRP. Simple access to such USRP's counter isn't possible
64 * so this variable isn't used in the "synchronized" state of the receiver yet.
65 */
66 unsigned d_counter;
67
68 /**@name Variables used to store result of the find_fcch_burst fuction */
69 //@{
70 bool d_freq_offset_tag_in_fcch; ///< frequency offset tag presence
71 unsigned d_fcch_start_pos; ///< position of the first sample of the fcch burst
72 float d_freq_offset_setting; ///< frequency offset set in frequency shifter located upstream
73 //@}
74 std::list<double> d_freq_offset_vals;
75
76 /**@name Identifiers of the BTS extracted from the SCH burst */
77 //@{
78 int d_ncc; ///< network color code
79 int d_bcc; ///< base station color code
80 //@}
81
82 /**@name Internal state of the gsm receiver */
83 //@{
84 enum states {
85 fcch_search, sch_search, // synchronization search part
86 synchronized // receiver is synchronized in this state
87 } d_state;
88 //@}
89
90 /**@name Variables which make internal state in the "synchronized" state */
91 //@{
92 burst_counter d_burst_nr; ///< frame number and timeslot number
93 channel_configuration d_channel_conf; ///< mapping of burst_counter to burst_type
94 //@}
95
96 unsigned d_failed_sch; ///< number of subsequent erroneous SCH bursts
97
98 /** Function whis is used to search a FCCH burst and to compute frequency offset before
99 * "synchronized" state of the receiver
100 *
101 * @param input vector with input signal
102 * @param nitems number of samples in the input vector
103 * @return
104 */
105 bool find_fcch_burst(const gr_complex *input, const int nitems, double & computed_freq_offset);
106
107 /** Computes frequency offset from FCCH burst samples
108 *
109 * @param[in] input vector with input samples
110 * @param[in] first_sample number of the first sample of the FCCH busrt
111 * @param[in] last_sample number of the last sample of the FCCH busrt
112 * @param[out] computed_freq_offset contains frequency offset estimate if FCCH burst was located
113 * @return true if frequency offset was faound
114 */
115 double compute_freq_offset(const gr_complex * input, unsigned first_sample, unsigned last_sample);
116 /** Computes angle between two complex numbers
117 *
118 * @param val1 first complex number
119 * @param val2 second complex number
120 * @return
121 */
122 inline float compute_phase_diff(gr_complex val1, gr_complex val2);
123
124 /** Function whis is used to get near to SCH burst
125 *
126 * @param nitems number of samples in the gsm_receiver's buffer
127 * @return true if SCH burst is near, false otherwise
128 */
129 bool reach_sch_burst(const int nitems);
130
131 /** Extracts channel impulse response from a SCH burst and computes first sample number of this burst
132 *
133 * @param input vector with input samples
134 * @param chan_imp_resp complex vector where channel impulse response will be stored
135 * @return number of first sample of the burst
136 */
137 int get_sch_chan_imp_resp(const gr_complex *input, gr_complex * chan_imp_resp);
138
139 /** MLSE detection of a burst bits
140 *
141 * Detects bits of burst using viterbi algorithm.
142 * @param input vector with input samples
143 * @param chan_imp_resp vector with the channel impulse response
144 * @param burst_start number of the first sample of the burst
145 * @param output_binary vector with output bits
146 */
147 void detect_burst(const gr_complex * input, gr_complex * chan_imp_resp, int burst_start, unsigned char * output_binary);
148
149 /** Encodes differentially input bits and maps them into MSK states
150 *
151 * @param input vector with input bits
152 * @param nitems number of samples in the "input" vector
153 * @param gmsk_output bits mapped into MSK states
154 * @param start_point first state
155 */
156 void gmsk_mapper(const unsigned char * input, int nitems, gr_complex * gmsk_output, gr_complex start_point);
157
158 /** Correlates MSK mapped sequence with input signal
159 *
160 * @param sequence MKS mapped sequence
161 * @param length length of the sequence
162 * @param input_signal vector with input samples
163 * @return correlation value
164 */
165 gr_complex correlate_sequence(const gr_complex * sequence, int length, const gr_complex * input);
166
167 /** Computes autocorrelation of input vector for positive arguments
168 *
169 * @param input vector with input samples
170 * @param out output vector
171 * @param nitems length of the input vector
172 */
173 inline void autocorrelation(const gr_complex * input, gr_complex * out, int nitems);
174
175 /** Filters input signal through channel impulse response
176 *
177 * @param input vector with input samples
178 * @param nitems number of samples to pass through filter
179 * @param filter filter taps - channel impulse response
180 * @param filter_length nember of filter taps
181 * @param output vector with filtered samples
182 */
183 inline void mafi(const gr_complex * input, int nitems, gr_complex * filter, int filter_length, gr_complex * output);
184
185 /** Extracts channel impulse response from a normal burst and computes first sample number of this burst
186 *
187 * @param input vector with input samples
188 * @param chan_imp_resp complex vector where channel impulse response will be stored
189 * @param search_range possible absolute offset of a channel impulse response start
190 * @param bcc base station color code - number of a training sequence
191 * @return first sample number of normal burst
192 */
193 int get_norm_chan_imp_resp(const gr_complex *input, gr_complex * chan_imp_resp, float *corr_max, int bcc);
194
195 /**
196 * Sends burst through a C0 (for burst from C0 channel) or Cx (for other bursts) message port
197 *
198 * @param burst_nr - frame number of the burst
199 * @param burst_binary - content of the burst
200 * @b_type - type of the burst
201 */
202 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);
203
204 /**
205 * Configures burst types in different channels
206 */
207 void configure_receiver();
208
209 /* State machine handlers */
210 void fcch_search_handler(gr_complex *input, int noutput_items);
211 void sch_search_handler(gr_complex *input, int noutput_items);
212 void synchronized_handler(gr_complex *input,
213 gr_vector_const_void_star &input_items, int noutput_items);
214
215 public:
216 receiver_impl(int osr, const std::vector<int> &cell_allocation, const std::vector<int> &tseq_nums, bool process_uplink);
218
219 int work(int noutput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items);
220 virtual void set_cell_allocation(const std::vector<int> &cell_allocation);
221 virtual void set_tseq_nums(const std::vector<int> & tseq_nums);
222 virtual void reset();
223 };
224 } // namespace gsm
225} // namespace gr
226
227#endif /* INCLUDED_GSM_RECEIVER_IMPL_H */
228
Definition: receiver_config.h:67
Definition: receiver_config.h:131
Definition: receiver_impl.h:36
virtual void reset()
int work(int noutput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items)
virtual void set_tseq_nums(const std::vector< int > &tseq_nums)
receiver_impl(int osr, const std::vector< int > &cell_allocation, const std::vector< int > &tseq_nums, bool process_uplink)
virtual void set_cell_allocation(const std::vector< int > &cell_allocation)
<+description of block+>
Definition: receiver.h:41
Definition: time_sample_ref.h:35
#define TRAIN_SEQ_NUM
Definition: gsm_constants.h:93
#define N_TRAIN_BITS
Definition: gsm_constants.h:36
burst_type
Definition: gsm_constants.h:63
#define N_SYNC_BITS
Definition: gsm_constants.h:37
Definition: constants.h:29