spandsp  0.0.6
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 #define V17_EQUALIZER_LEN 17
34 /*! Samples before the target position in the equalizer buffer */
35 //#define V17_EQUALIZER_PRE_LEN 16
36 #define V17_EQUALIZER_PRE_LEN 8
37 
38 /*! The number of taps in the pulse shaping/bandpass filter */
39 #define V17_RX_FILTER_STEPS 27
40 
41 /* We can store more trellis depth that we look back over, so that we can push out a group
42  of symbols in one go, giving greater processing efficiency, at the expense of a bit more
43  latency through the modem. */
44 /* Right now we don't take advantage of this optimisation. */
45 /*! The depth of the trellis buffer */
46 #define V17_TRELLIS_STORAGE_DEPTH 16
47 /*! How far we look back into history for trellis decisions */
48 #define V17_TRELLIS_LOOKBACK_DEPTH 16
49 
50 /*!
51  V.17 modem receive side descriptor. This defines the working state for a
52  single instance of a V.17 modem receiver.
53 */
55 {
56  /*! \brief The bit rate of the modem. Valid values are 7200 9600, 12000 and 14400. */
57  int bit_rate;
58  /*! \brief The callback function used to put each bit received. */
60  /*! \brief A user specified opaque pointer passed to the put_but routine. */
62 
63  /*! \brief The callback function used to report modem status changes. */
65  /*! \brief A user specified opaque pointer passed to the status function. */
67 
68  /*! \brief A callback function which may be enabled to report every symbol's
69  constellation position. */
70  qam_report_handler_t qam_report;
71  /*! \brief A user specified opaque pointer passed to the qam_report callback
72  routine. */
74 
75  /*! \brief The route raised cosine (RRC) pulse shaping filter buffer. */
76 #if defined(SPANDSP_USE_FIXED_POINT)
77  int16_t rrc_filter[V17_RX_FILTER_STEPS];
78 #else
79  float rrc_filter[V17_RX_FILTER_STEPS];
80 #endif
81  /*! \brief Current offset into the RRC pulse shaping filter buffer. */
83 
84  /*! \brief The state of the differential decoder */
85  int diff;
86  /*! \brief The register for the data scrambler. */
87  uint32_t scramble_reg;
88  /*! \brief Scrambler tap */
89  //int scrambler_tap;
90 
91  /*! \brief TRUE if the short training sequence is to be used. */
93  /*! \brief The section of the training data we are currently in. */
95  /*! \brief A count of how far through the current training step we are. */
97  /*! \brief A measure of how much mismatch there is between the real constellation,
98  and the decoded symbol positions. */
100  /*! \brief The value of the last signal sample, using the a simple HPF for signal power estimation. */
101  int16_t last_sample;
102  /*! \brief >0 if a signal above the minimum is present. It may or may not be a V.17 signal. */
104  /*! \brief Whether or not a carrier drop was detected and the signal delivery is pending. */
106  /*! \brief A count of the current consecutive samples below the carrier off threshold. */
108  /*! \brief A highest magnitude sample seen. */
109  int16_t high_sample;
110 
111  /*! \brief The current phase of the carrier (i.e. the DDS parameter). */
112  uint32_t carrier_phase;
113  /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */
115  /*! \brief The carrier update rate saved for reuse when using short training. */
117 #if defined(SPANDSP_USE_FIXED_POINTx)
118  /*! \brief The proportional part of the carrier tracking filter. */
119  float carrier_track_p;
120  /*! \brief The integral part of the carrier tracking filter. */
121  float carrier_track_i;
122 #else
123  /*! \brief The proportional part of the carrier tracking filter. */
125  /*! \brief The integral part of the carrier tracking filter. */
127 #endif
128 
129  /*! \brief A power meter, to measure the HPF'ed signal power in the channel. */
131  /*! \brief The power meter level at which carrier on is declared. */
133  /*! \brief The power meter level at which carrier off is declared. */
135 
136  /*! \brief Current read offset into the equalizer buffer. */
137  int eq_step;
138  /*! \brief Current write offset into the equalizer buffer. */
140  /*! \brief Symbol count to the next equalizer update. */
141  int eq_skip;
142 
143  /*! \brief The current half of the baud. */
145 
146 #if defined(SPANDSP_USE_FIXED_POINTx)
147  /*! \brief The scaling factor accessed by the AGC algorithm. */
148  float agc_scaling;
149  /*! \brief The previous value of agc_scaling, needed to reuse old training. */
150  float agc_scaling_save;
151 
152  /*! \brief The current delta factor for updating the equalizer coefficients. */
153  float eq_delta;
154  /*! \brief The adaptive equalizer coefficients. */
155  complexi16_t eq_coeff[V17_EQUALIZER_LEN];
156  /*! \brief A saved set of adaptive equalizer coefficients for use after restarts. */
157  complexi16_t eq_coeff_save[V17_EQUALIZER_LEN];
158  /*! \brief The equalizer signal buffer. */
159  complexi16_t eq_buf[V17_EQUALIZER_LEN];
160 
161  /*! Low band edge filter for symbol sync. */
162  int32_t symbol_sync_low[2];
163  /*! High band edge filter for symbol sync. */
164  int32_t symbol_sync_high[2];
165  /*! DC filter for symbol sync. */
166  int32_t symbol_sync_dc_filter[2];
167  /*! Baud phase for symbol sync. */
168  int32_t baud_phase;
169 #else
170  /*! \brief The scaling factor accessed by the AGC algorithm. */
171  float agc_scaling;
172  /*! \brief The previous value of agc_scaling, needed to reuse old training. */
174 
175  /*! \brief The current delta factor for updating the equalizer coefficients. */
176  float eq_delta;
177  /*! \brief The adaptive equalizer coefficients. */
178  complexf_t eq_coeff[V17_EQUALIZER_LEN];
179  /*! \brief A saved set of adaptive equalizer coefficients for use after restarts. */
180  complexf_t eq_coeff_save[V17_EQUALIZER_LEN];
181  /*! \brief The equalizer signal buffer. */
182  complexf_t eq_buf[V17_EQUALIZER_LEN];
183 
184  /*! Low band edge filter for symbol sync. */
185  float symbol_sync_low[2];
186  /*! High band edge filter for symbol sync. */
188  /*! DC filter for symbol sync. */
190  /*! Baud phase for symbol sync. */
191  float baud_phase;
192 #endif
193 
194  /*! \brief The total symbol timing correction since the carrier came up.
195  This is only for performance analysis purposes. */
197 
198  /*! \brief Starting phase angles for the coarse carrier aquisition step. */
199  int32_t start_angles[2];
200  /*! \brief History list of phase angles for the coarse carrier aquisition step. */
201  int32_t angles[16];
202  /*! \brief A pointer to the current constellation. */
203 #if defined(SPANDSP_USE_FIXED_POINTx)
205 #else
207 #endif
208  /*! \brief A pointer to the current space map. There is a space map for
209  each trellis state. */
211  /*! \brief The number of bits in each symbol at the current bit rate. */
213 
214  /*! \brief Current pointer to the trellis buffers */
216  /*! \brief The trellis. */
217  int full_path_to_past_state_locations[V17_TRELLIS_STORAGE_DEPTH][8];
218  /*! \brief The trellis. */
219  int past_state_locations[V17_TRELLIS_STORAGE_DEPTH][8];
220  /*! \brief Euclidean distances (actually the squares of the distances)
221  from the last states of the trellis. */
222 #if defined(SPANDSP_USE_FIXED_POINTx)
223  uint32_t distances[8];
224 #else
225  float distances[8];
226 #endif
227  /*! \brief Error and flow logging control */
229 };
230 
231 #endif
232 /*- End of file ------------------------------------------------------------*/