spandsp  3.0.0
private/v17rx.h
1 /*
2  * SpanDSP - a series of DSP components for telephony
3  *
4  * private/v17rx.h - ITU V.17 modem receive part
5  *
6  * Written by Steve Underwood <steveu@coppice.org>
7  *
8  * Copyright (C) 2003 Steve Underwood
9  *
10  * All rights reserved.
11  *
12  * This program is free software; you can redistribute it and/or modify
13  * it under the terms of the GNU Lesser General Public License version 2.1,
14  * as published by the Free Software Foundation.
15  *
16  * This program is distributed in the hope that it will be useful,
17  * but WITHOUT ANY WARRANTY; without even the implied warranty of
18  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
19  * GNU Lesser General Public License for more details.
20  *
21  * You should have received a copy of the GNU Lesser General Public
22  * License along with this program; if not, write to the Free Software
23  * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
24  */
25 
26 #if !defined(_SPANDSP_PRIVATE_V17RX_H_)
27 #define _SPANDSP_PRIVATE_V17RX_H_
28 
29 /* Target length for the equalizer is about 63 taps, to deal with the worst stuff
30  in V.56bis. */
31 /*! The length of the equalizer buffer */
32 #define V17_EQUALIZER_LEN 33
33 
34 /*! Samples before the target position in the equalizer buffer */
35 #define V17_EQUALIZER_PRE_LEN 16
36 
37 /*! The number of taps in the pulse shaping/bandpass filter */
38 #define V17_RX_FILTER_STEPS 27
39 
40 /* We can store more trellis depth that we look back over, so that we can push out a group
41  of symbols in one go, giving greater processing efficiency, at the expense of a bit more
42  latency through the modem. */
43 /* Right now we don't take advantage of this optimisation. */
44 /*! The depth of the trellis buffer */
45 #define V17_TRELLIS_STORAGE_DEPTH 16
46 /*! How far we look back into history for trellis decisions */
47 #define V17_TRELLIS_LOOKBACK_DEPTH 16
48 
49 /*!
50  V.17 modem receive side descriptor. This defines the working state for a
51  single instance of a V.17 modem receiver.
52 */
54 {
55  /*! \brief The bit rate of the modem. Valid values are 7200 9600, 12000 and 14400. */
56  int bit_rate;
57  /*! \brief The callback function used to put each bit received. */
59  /*! \brief A user specified opaque pointer passed to the put_but routine. */
61 
62  /*! \brief The callback function used to report modem status changes. */
64  /*! \brief A user specified opaque pointer passed to the status function. */
66 
67  /*! \brief A callback function which may be enabled to report every symbol's
68  constellation position. */
69  qam_report_handler_t qam_report;
70  /*! \brief A user specified opaque pointer passed to the qam_report callback
71  routine. */
73 
74 #if defined(SPANDSP_USE_FIXED_POINTx)
75  /*! \brief The scaling factor assessed by the AGC algorithm. */
76  int16_t agc_scaling;
77  /*! \brief The previous value of agc_scaling, needed to reuse old training. */
78  int16_t agc_scaling_save;
79 
80  /*! \brief The current delta factor for updating the equalizer coefficients. */
81  int16_t eq_delta;
82  /*! \brief The adaptive equalizer coefficients. */
83  complexi16_t eq_coeff[V17_EQUALIZER_LEN];
84  /*! \brief A saved set of adaptive equalizer coefficients for use after restarts. */
85  complexi16_t eq_coeff_save[V17_EQUALIZER_LEN];
86  /*! \brief The equalizer signal buffer. */
87  complexi16_t eq_buf[V17_EQUALIZER_LEN];
88 
89  /*! Low band edge filter for symbol sync. */
90  int32_t symbol_sync_low[2];
91  /*! High band edge filter for symbol sync. */
92  int32_t symbol_sync_high[2];
93  /*! DC filter for symbol sync. */
94  int32_t symbol_sync_dc_filter[2];
95  /*! Baud phase for symbol sync. */
96  int32_t baud_phase;
97 
98  /*! \brief A measure of how much mismatch there is between the real constellation,
99  and the decoded symbol positions. */
100  int32_t training_error;
101 
102  /*! \brief The proportional part of the carrier tracking filter. */
103  int32_t carrier_track_p;
104  /*! \brief The integral part of the carrier tracking filter. */
105  int32_t carrier_track_i;
106  /*! \brief The root raised cosine (RRC) pulse shaping filter buffer. */
107  int16_t rrc_filter[V17_RX_FILTER_STEPS];
108 
109  /*! \brief A pointer to the current constellation. */
111 #else
112  /*! \brief The scaling factor assessed by the AGC algorithm. */
113  float agc_scaling;
114  /*! \brief The previous value of agc_scaling, needed to reuse old training. */
116 
117  /*! \brief The current delta factor for updating the equalizer coefficients. */
118  float eq_delta;
119  /*! \brief The adaptive equalizer coefficients. */
120  complexf_t eq_coeff[V17_EQUALIZER_LEN];
121  /*! \brief A saved set of adaptive equalizer coefficients for use after restarts. */
122  complexf_t eq_coeff_save[V17_EQUALIZER_LEN];
123  /*! \brief The equalizer signal buffer. */
124  complexf_t eq_buf[V17_EQUALIZER_LEN];
125 
126  /*! Low band edge filter for symbol sync. */
127  float symbol_sync_low[2];
128  /*! High band edge filter for symbol sync. */
130  /*! DC filter for symbol sync. */
132  /*! Baud phase for symbol sync. */
133  float baud_phase;
134 
135  /*! \brief A measure of how much mismatch there is between the real constellation,
136  and the decoded symbol positions. */
138 
139  /*! \brief The proportional part of the carrier tracking filter. */
141  /*! \brief The integral part of the carrier tracking filter. */
143  /*! \brief The root raised cosine (RRC) pulse shaping filter buffer. */
144  float rrc_filter[V17_RX_FILTER_STEPS];
145 
146  /*! \brief A pointer to the current constellation. */
148 #endif
149  /*! \brief Current offset into the RRC pulse shaping filter buffer. */
151 
152  /*! \brief The current state of the differential decoder */
153  int diff;
154  /*! \brief The register for the data scrambler. */
155  uint32_t scramble_reg;
156  /*! \brief Scrambler tap */
158 
159  /*! \brief True if the short training sequence is to be used. */
161  /*! \brief The section of the training data we are currently in. */
163  /*! \brief A count of how far through the current training step we are. */
165  /*! \brief The value of the last signal sample, using the a simple HPF for signal power estimation. */
166  int16_t last_sample;
167  /*! \brief >0 if a signal above the minimum is present. It may or may not be a V.17 signal. */
169  /*! \brief Whether or not a carrier drop was detected and the signal delivery is pending. */
171  /*! \brief A count of the current consecutive samples below the carrier off threshold. */
173  /*! \brief A highest magnitude sample seen. */
174  int16_t high_sample;
175 
176  /*! \brief The current phase of the carrier (i.e. the DDS parameter). */
177  uint32_t carrier_phase;
178  /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */
180  /*! \brief The carrier update rate saved for reuse when using short training. */
182 
183  /*! \brief A power meter, to measure the HPF'ed signal power in the channel. */
185  /*! \brief The power meter level at which carrier on is declared. */
187  /*! \brief The power meter level at which carrier off is declared. */
189 
190  /*! \brief Current read offset into the equalizer buffer. */
191  int eq_step;
192  /*! \brief Current write offset into the equalizer buffer. */
194  /*! \brief Symbol count to the next equalizer update. */
195  int eq_skip;
196 
197  /*! \brief The current half of the baud. */
199 
200  /*! \brief The total symbol timing correction since the carrier came up.
201  This is only for performance analysis purposes. */
203 
204  /*! \brief The previous symbol phase angles for the coarse carrier aquisition step. */
205  int32_t last_angles[2];
206  /*! \brief History list of phase angle differences for the coarse carrier aquisition step. */
207  int32_t diff_angles[16];
208 
209  /*! \brief A pointer to the current space map. There is a space map for
210  each trellis state. */
212  /*! \brief The number of bits in each symbol at the current bit rate. */
214 
215  /*! \brief Current pointer to the trellis buffers */
217  /*! \brief The trellis. */
218  int full_path_to_past_state_locations[V17_TRELLIS_STORAGE_DEPTH][8];
219  /*! \brief The trellis. */
220  int past_state_locations[V17_TRELLIS_STORAGE_DEPTH][8];
221 #if defined(SPANDSP_USE_FIXED_POINTx)
222  /*! \brief Euclidean distances (actually the squares of the distances)
223  from the last states of the trellis. */
224  uint32_t distances[8];
225 #else
226  /*! \brief Euclidean distances (actually the squares of the distances)
227  from the last states of the trellis. */
228  float distances[8];
229 #endif
230  /*! \brief Error and flow logging control */
232 };
233 
234 #endif
235 /*- End of file ------------------------------------------------------------*/
void(* modem_status_func_t)(void *user_data, int status)
Definition: async.h:113
void(* put_bit_func_t)(void *user_data, int bit)
Definition: async.h:107
Definition: complex.h:43
Definition: complex.h:89
Definition: private/logging.h:34
Definition: private/power_meter.h:34
Definition: private/v17rx.h:54
float symbol_sync_low[2]
Definition: private/v17rx.h:127
qam_report_handler_t qam_report
A callback function which may be enabled to report every symbol's constellation position.
Definition: private/v17rx.h:69
complexf_t eq_coeff_save[33]
A saved set of adaptive equalizer coefficients for use after restarts.
Definition: private/v17rx.h:122
int32_t carrier_off_power
The power meter level at which carrier off is declared.
Definition: private/v17rx.h:188
int32_t carrier_phase_rate_save
The carrier update rate saved for reuse when using short training.
Definition: private/v17rx.h:181
int space_map
A pointer to the current space map. There is a space map for each trellis state.
Definition: private/v17rx.h:211
int signal_present
>0 if a signal above the minimum is present. It may or may not be a V.17 signal.
Definition: private/v17rx.h:168
int low_samples
A count of the current consecutive samples below the carrier off threshold.
Definition: private/v17rx.h:172
float symbol_sync_dc_filter[2]
Definition: private/v17rx.h:131
float training_error
A measure of how much mismatch there is between the real constellation, and the decoded symbol positi...
Definition: private/v17rx.h:137
int eq_put_step
Current write offset into the equalizer buffer.
Definition: private/v17rx.h:193
logging_state_t logging
Error and flow logging control.
Definition: private/v17rx.h:231
power_meter_t power
A power meter, to measure the HPF'ed signal power in the channel.
Definition: private/v17rx.h:184
uint32_t scramble_reg
The register for the data scrambler.
Definition: private/v17rx.h:155
put_bit_func_t put_bit
The callback function used to put each bit received.
Definition: private/v17rx.h:58
int trellis_ptr
Current pointer to the trellis buffers.
Definition: private/v17rx.h:216
void * put_bit_user_data
A user specified opaque pointer passed to the put_but routine.
Definition: private/v17rx.h:60
int carrier_drop_pending
Whether or not a carrier drop was detected and the signal delivery is pending.
Definition: private/v17rx.h:170
uint32_t carrier_phase
The current phase of the carrier (i.e. the DDS parameter).
Definition: private/v17rx.h:177
int training_count
A count of how far through the current training step we are.
Definition: private/v17rx.h:164
float baud_phase
Definition: private/v17rx.h:133
float distances[8]
Euclidean distances (actually the squares of the distances) from the last states of the trellis.
Definition: private/v17rx.h:228
int rrc_filter_step
Current offset into the RRC pulse shaping filter buffer.
Definition: private/v17rx.h:150
int32_t carrier_phase_rate
The update rate for the phase of the carrier (i.e. the DDS increment).
Definition: private/v17rx.h:179
int scrambler_tap
Scrambler tap.
Definition: private/v17rx.h:157
float agc_scaling_save
The previous value of agc_scaling, needed to reuse old training.
Definition: private/v17rx.h:115
int diff
The current state of the differential decoder.
Definition: private/v17rx.h:153
complexf_t eq_coeff[33]
The adaptive equalizer coefficients.
Definition: private/v17rx.h:120
int32_t diff_angles[16]
History list of phase angle differences for the coarse carrier aquisition step.
Definition: private/v17rx.h:207
int bit_rate
The bit rate of the modem. Valid values are 7200 9600, 12000 and 14400.
Definition: private/v17rx.h:56
const complexf_t * constellation
A pointer to the current constellation.
Definition: private/v17rx.h:147
float carrier_track_i
The integral part of the carrier tracking filter.
Definition: private/v17rx.h:142
int32_t last_angles[2]
The previous symbol phase angles for the coarse carrier aquisition step.
Definition: private/v17rx.h:205
int baud_half
The current half of the baud.
Definition: private/v17rx.h:198
float carrier_track_p
The proportional part of the carrier tracking filter.
Definition: private/v17rx.h:140
int16_t high_sample
A highest magnitude sample seen.
Definition: private/v17rx.h:174
int past_state_locations[16][8]
The trellis.
Definition: private/v17rx.h:220
float symbol_sync_high[2]
Definition: private/v17rx.h:129
float rrc_filter[27]
The root raised cosine (RRC) pulse shaping filter buffer.
Definition: private/v17rx.h:144
modem_status_func_t status_handler
The callback function used to report modem status changes.
Definition: private/v17rx.h:63
int total_baud_timing_correction
The total symbol timing correction since the carrier came up. This is only for performance analysis p...
Definition: private/v17rx.h:202
float agc_scaling
The scaling factor assessed by the AGC algorithm.
Definition: private/v17rx.h:113
int eq_step
Current read offset into the equalizer buffer.
Definition: private/v17rx.h:191
int32_t carrier_on_power
The power meter level at which carrier on is declared.
Definition: private/v17rx.h:186
int full_path_to_past_state_locations[16][8]
The trellis.
Definition: private/v17rx.h:218
void * qam_user_data
A user specified opaque pointer passed to the qam_report callback routine.
Definition: private/v17rx.h:72
int eq_skip
Symbol count to the next equalizer update.
Definition: private/v17rx.h:195
void * status_user_data
A user specified opaque pointer passed to the status function.
Definition: private/v17rx.h:65
int16_t last_sample
The value of the last signal sample, using the a simple HPF for signal power estimation.
Definition: private/v17rx.h:166
bool short_train
True if the short training sequence is to be used.
Definition: private/v17rx.h:160
int bits_per_symbol
The number of bits in each symbol at the current bit rate.
Definition: private/v17rx.h:213
int training_stage
The section of the training data we are currently in.
Definition: private/v17rx.h:162
complexf_t eq_buf[33]
The equalizer signal buffer.
Definition: private/v17rx.h:124
float eq_delta
The current delta factor for updating the equalizer coefficients.
Definition: private/v17rx.h:118