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  /*! \brief A measure of how much mismatch there is between the real constellation,
90  and the decoded symbol positions. */
91  int64_t training_error;
92 
93  /*! \brief The proportional part of the carrier tracking filter. */
94  int32_t carrier_track_p;
95  /*! \brief The integral part of the carrier tracking filter. */
96  int32_t carrier_track_i;
97  /*! \brief The root raised cosine (RRC) pulse shaping filter buffer. */
98  int16_t rrc_filter[V17_RX_FILTER_STEPS];
99 
100  /*! \brief A pointer to the current constellation. */
102 #else
103  /*! \brief The scaling factor assessed by the AGC algorithm. */
104  float agc_scaling;
105  /*! \brief The previous value of agc_scaling, needed to reuse old training. */
107 
108  /*! \brief The current delta factor for updating the equalizer coefficients. */
109  float eq_delta;
110  /*! \brief The adaptive equalizer coefficients. */
111  complexf_t eq_coeff[V17_EQUALIZER_LEN];
112  /*! \brief A saved set of adaptive equalizer coefficients for use after restarts. */
113  complexf_t eq_coeff_save[V17_EQUALIZER_LEN];
114  /*! \brief The equalizer signal buffer. */
115  complexf_t eq_buf[V17_EQUALIZER_LEN];
116 
117  /*! \brief A measure of how much mismatch there is between the real constellation,
118  and the decoded symbol positions. */
120 
121  /*! \brief The proportional part of the carrier tracking filter. */
123  /*! \brief The integral part of the carrier tracking filter. */
125  /*! \brief The root raised cosine (RRC) pulse shaping filter buffer. */
126  float rrc_filter[V17_RX_FILTER_STEPS];
127 
128  /*! \brief A pointer to the current constellation. */
130 #endif
131  godard_ted_state_t godard;
132 
133  /*! \brief Current offset into the RRC pulse shaping filter buffer. */
135 
136  /*! \brief The current state of the differential decoder */
137  int diff;
138  /*! \brief The register for the data scrambler. */
139  uint32_t scramble_reg;
140  /*! \brief Scrambler tap */
142 
143  /*! \brief True if the short training sequence is to be used. */
145  /*! \brief The section of the training data we are currently in. */
147  /*! \brief A count of how far through the current training step we are. */
149  /*! \brief The value of the last signal sample, using the a simple HPF for signal power estimation. */
150  int16_t last_sample;
151  /*! \brief >0 if a signal above the minimum is present. It may or may not be a V.17 signal. */
153  /*! \brief Whether or not a carrier drop was detected and the signal delivery is pending. */
155  /*! \brief A count of the current consecutive samples below the carrier off threshold. */
157  /*! \brief A highest magnitude sample seen. */
158  int16_t high_sample;
159 
160  /*! \brief The current phase of the carrier (i.e. the DDS parameter). */
161  uint32_t carrier_phase;
162  /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */
164  /*! \brief The carrier update rate saved for reuse when using short training. */
166 
167  /*! \brief A power meter, to measure the HPF'ed signal power in the channel. */
169  /*! \brief The power meter level at which carrier on is declared. */
171  /*! \brief The power meter level at which carrier off is declared. */
173 
174  /*! \brief Current read offset into the equalizer buffer. */
175  int eq_step;
176  /*! \brief Current write offset into the equalizer buffer. */
178  /*! \brief Symbol count to the next equalizer update. */
179  int eq_skip;
180 
181  /*! \brief The current half of the baud. */
183 
184  /*! \brief The previous symbol phase angles for the coarse carrier aquisition step. */
185  int32_t last_angles[2];
186  /*! \brief History list of phase angle differences for the coarse carrier aquisition step. */
187  int32_t diff_angles[16];
188 
189  /*! \brief A pointer to the current space map. There is a space map for
190  each trellis state. */
192  /*! \brief The number of bits in each symbol at the current bit rate. */
194 
195  /*! \brief Current pointer to the trellis buffers */
197  /*! \brief The trellis. */
198  int full_path_to_past_state_locations[V17_TRELLIS_STORAGE_DEPTH][8];
199  /*! \brief The trellis. */
200  int past_state_locations[V17_TRELLIS_STORAGE_DEPTH][8];
201 #if defined(SPANDSP_USE_FIXED_POINTx)
202  /*! \brief Euclidean distances (actually the squares of the distances)
203  from the last states of the trellis. */
204  uint32_t distances[8];
205 #else
206  /*! \brief Euclidean distances (actually the squares of the distances)
207  from the last states of the trellis. */
208  float distances[8];
209 #endif
210  /*! \brief Error and flow logging control */
212 };
213 
214 #endif
215 /*- End of file ------------------------------------------------------------*/
Definition: private/power_meter.h:33
Definition: private/godard.h:29
int trellis_ptr
Current pointer to the trellis buffers.
Definition: private/v17rx.h:196
power_meter_t power
A power meter, to measure the HPF&#39;ed signal power in the channel.
Definition: private/v17rx.h:168
Definition: complex.h:88
uint32_t carrier_phase
The current phase of the carrier (i.e. the DDS parameter).
Definition: private/v17rx.h:161
complexf_t eq_coeff[33]
The adaptive equalizer coefficients.
Definition: private/v17rx.h:111
complexf_t eq_coeff_save[33]
A saved set of adaptive equalizer coefficients for use after restarts.
Definition: private/v17rx.h:113
int full_path_to_past_state_locations[16][8]
The trellis.
Definition: private/v17rx.h:198
int32_t carrier_phase_rate
The update rate for the phase of the carrier (i.e. the DDS increment).
Definition: private/v17rx.h:163
Definition: private/v17rx.h:53
uint32_t scramble_reg
The register for the data scrambler.
Definition: private/v17rx.h:139
int32_t last_angles[2]
The previous symbol phase angles for the coarse carrier aquisition step.
Definition: private/v17rx.h:185
int32_t carrier_on_power
The power meter level at which carrier on is declared.
Definition: private/v17rx.h:170
int32_t carrier_off_power
The power meter level at which carrier off is declared.
Definition: private/v17rx.h:172
int eq_put_step
Current write offset into the equalizer buffer.
Definition: private/v17rx.h:177
int16_t last_sample
The value of the last signal sample, using the a simple HPF for signal power estimation.
Definition: private/v17rx.h:150
complexf_t eq_buf[33]
The equalizer signal buffer.
Definition: private/v17rx.h:115
int training_count
A count of how far through the current training step we are.
Definition: private/v17rx.h:148
void * status_user_data
A user specified opaque pointer passed to the status function.
Definition: private/v17rx.h:65
int eq_skip
Symbol count to the next equalizer update.
Definition: private/v17rx.h:179
float eq_delta
The current delta factor for updating the equalizer coefficients.
Definition: private/v17rx.h:109
int diff
The current state of the differential decoder.
Definition: private/v17rx.h:137
int carrier_drop_pending
Whether or not a carrier drop was detected and the signal delivery is pending.
Definition: private/v17rx.h:154
void(* span_modem_status_func_t)(void *user_data, int status)
Definition: async.h:131
void(* span_put_bit_func_t)(void *user_data, int bit)
Definition: async.h:123
int32_t diff_angles[16]
History list of phase angle differences for the coarse carrier aquisition step.
Definition: private/v17rx.h:187
void * qam_user_data
A user specified opaque pointer passed to the qam_report callback routine.
Definition: private/v17rx.h:72
int scrambler_tap
Scrambler tap.
Definition: private/v17rx.h:141
float agc_scaling
The scaling factor assessed by the AGC algorithm.
Definition: private/v17rx.h:104
int bit_rate
The bit rate of the modem. Valid values are 7200 9600, 12000 and 14400.
Definition: private/v17rx.h:56
float distances[8]
Euclidean distances (actually the squares of the distances) from the last states of the trellis...
Definition: private/v17rx.h:208
float training_error
A measure of how much mismatch there is between the real constellation, and the decoded symbol positi...
Definition: private/v17rx.h:119
float carrier_track_p
The proportional part of the carrier tracking filter.
Definition: private/v17rx.h:122
int baud_half
The current half of the baud.
Definition: private/v17rx.h:182
span_modem_status_func_t status_handler
The callback function used to report modem status changes.
Definition: private/v17rx.h:63
int32_t carrier_phase_rate_save
The carrier update rate saved for reuse when using short training.
Definition: private/v17rx.h:165
int bits_per_symbol
The number of bits in each symbol at the current bit rate.
Definition: private/v17rx.h:193
Definition: complex.h:42
bool short_train
True if the short training sequence is to be used.
Definition: private/v17rx.h:144
int16_t high_sample
A highest magnitude sample seen.
Definition: private/v17rx.h:158
int eq_step
Current read offset into the equalizer buffer.
Definition: private/v17rx.h:175
int low_samples
A count of the current consecutive samples below the carrier off threshold.
Definition: private/v17rx.h:156
Definition: private/logging.h:33
float agc_scaling_save
The previous value of agc_scaling, needed to reuse old training.
Definition: private/v17rx.h:106
int past_state_locations[16][8]
The trellis.
Definition: private/v17rx.h:200
int space_map
A pointer to the current space map. There is a space map for each trellis state.
Definition: private/v17rx.h:191
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:152
int training_stage
The section of the training data we are currently in.
Definition: private/v17rx.h:146
float carrier_track_i
The integral part of the carrier tracking filter.
Definition: private/v17rx.h:124
int rrc_filter_step
Current offset into the RRC pulse shaping filter buffer.
Definition: private/v17rx.h:134
void * put_bit_user_data
A user specified opaque pointer passed to the put_but routine.
Definition: private/v17rx.h:60
float rrc_filter[27]
The root raised cosine (RRC) pulse shaping filter buffer.
Definition: private/v17rx.h:126
span_put_bit_func_t put_bit
The callback function used to put each bit received.
Definition: private/v17rx.h:58
logging_state_t logging
Error and flow logging control.
Definition: private/v17rx.h:211
const complexf_t * constellation
A pointer to the current constellation.
Definition: private/v17rx.h:129
qam_report_handler_t qam_report
A callback function which may be enabled to report every symbol&#39;s constellation position.
Definition: private/v17rx.h:69