spandsp  0.0.6
private/v27ter_rx.h
1 /*
2  * SpanDSP - a series of DSP components for telephony
3  *
4  * private/v27ter_rx.h - ITU V.27ter 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_V27TER_RX_H_)
27 #define _SPANDSP_PRIVATE_V27TER_RX_H_
28 
29 /* Target length for the equalizer is about 43 taps for 4800bps and 32 taps for 2400bps
30  to deal with the worst stuff in V.56bis. */
31 /*! The length of the equalizer buffer. Must be a power of 2 */
32 #define V27TER_EQUALIZER_LEN 32
33 /*! Samples before the target central position in the equalizer buffer */
34 #define V27TER_EQUALIZER_PRE_LEN 16
35 
36 /*! The number of taps in the 4800bps pulse shaping/bandpass filter */
37 #define V27TER_RX_4800_FILTER_STEPS 27
38 /*! The number of taps in the 2400bps pulse shaping/bandpass filter */
39 #define V27TER_RX_2400_FILTER_STEPS 27
40 
41 #if V27TER_RX_4800_FILTER_STEPS > V27TER_RX_2400_FILTER_STEPS
42 #define V27TER_RX_FILTER_STEPS V27TER_RX_4800_FILTER_STEPS
43 #else
44 #define V27TER_RX_FILTER_STEPS V27TER_RX_2400_FILTER_STEPS
45 #endif
46 
47 /*!
48  V.27ter modem receive side descriptor. This defines the working state for a
49  single instance of a V.27ter modem receiver.
50 */
52 {
53  /*! \brief The bit rate of the modem. Valid values are 2400 and 4800. */
54  int bit_rate;
55  /*! \brief The callback function used to put each bit received. */
57  /*! \brief A user specified opaque pointer passed to the put_bit routine. */
59 
60  /*! \brief The callback function used to report modem status changes. */
62  /*! \brief A user specified opaque pointer passed to the status function. */
64 
65  /*! \brief A callback function which may be enabled to report every symbol's
66  constellation position. */
67  qam_report_handler_t qam_report;
68  /*! \brief A user specified opaque pointer passed to the qam_report callback
69  routine. */
71 
72  /*! \brief The route raised cosine (RRC) pulse shaping filter buffer. */
73 #if defined(SPANDSP_USE_FIXED_POINT)
74  int16_t rrc_filter[V27TER_RX_FILTER_STEPS];
75 #else
76  float rrc_filter[V27TER_RX_FILTER_STEPS];
77 #endif
78  /*! \brief Current offset into the RRC pulse shaping filter buffer. */
80 
81  /*! \brief The register for the training and data scrambler. */
82  unsigned int scramble_reg;
83  /*! \brief A counter for the number of consecutive bits of repeating pattern through
84  the scrambler. */
86  /*! \brief The current step in the table of BC constellation positions. */
88  /*! \brief TRUE if the previous trained values are to be reused. */
89  int old_train;
90  /*! \brief The section of the training data we are currently in. */
92  /*! \brief A count of how far through the current training step we are. */
94  /*! \brief A measure of how much mismatch there is between the real constellation,
95  and the decoded symbol positions. */
97  /*! \brief The value of the last signal sample, using the a simple HPF for signal power estimation. */
98  int16_t last_sample;
99  /*! \brief >0 if a signal above the minimum is present. It may or may not be a V.27ter signal. */
101  /*! \brief Whether or not a carrier drop was detected and the signal delivery is pending. */
103  /*! \brief A count of the current consecutive samples below the carrier off threshold. */
105  /*! \brief A highest magnitude sample seen. */
106  int16_t high_sample;
107 
108  /*! \brief The position of the current symbol in the constellation, used for
109  differential decoding. */
111 
112  /*! \brief The current phase of the carrier (i.e. the DDS parameter). */
113  uint32_t carrier_phase;
114  /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */
116  /*! \brief The carrier update rate saved for reuse when using short training. */
118 #if defined(SPANDSP_USE_FIXED_POINTx)
119  /*! \brief The proportional part of the carrier tracking filter. */
120  float carrier_track_p;
121  /*! \brief The integral part of the carrier tracking filter. */
122  float carrier_track_i;
123 #else
124  /*! \brief The proportional part of the carrier tracking filter. */
126  /*! \brief The integral part of the carrier tracking filter. */
128 #endif
129 
130  /*! \brief A power meter, to measure the HPF'ed signal power in the channel. */
132  /*! \brief The power meter level at which carrier on is declared. */
134  /*! \brief The power meter level at which carrier off is declared. */
136 
137  /*! \brief Current read offset into the equalizer buffer. */
138  int eq_step;
139  /*! \brief Current write offset into the equalizer buffer. */
141  /*! \brief Symbol counter to the next equalizer update. */
142  int eq_skip;
143 
144  /*! \brief The current half of the baud. */
146 
147 #if defined(SPANDSP_USE_FIXED_POINT)
148  /*! \brief The scaling factor accessed by the AGC algorithm. */
149  int16_t agc_scaling;
150  /*! \brief The previous value of agc_scaling, needed to reuse old training. */
151  int16_t agc_scaling_save;
152 
153  /*! \brief The current delta factor for updating the equalizer coefficients. */
154  float eq_delta;
155  /*! \brief The adaptive equalizer coefficients. */
156  /*complexi16_t*/ complexf_t eq_coeff[V27TER_EQUALIZER_LEN];
157  /*! \brief A saved set of adaptive equalizer coefficients for use after restarts. */
158  /*complexi16_t*/ complexf_t eq_coeff_save[V27TER_EQUALIZER_LEN];
159  /*! \brief The equalizer signal buffer. */
160  /*complexi16_t*/ complexf_t eq_buf[V27TER_EQUALIZER_LEN];
161 #else
162  /*! \brief The scaling factor accessed by the AGC algorithm. */
163  float agc_scaling;
164  /*! \brief The previous value of agc_scaling, needed to reuse old training. */
166 
167  /*! \brief The current delta factor for updating the equalizer coefficients. */
168  float eq_delta;
169  /*! \brief The adaptive equalizer coefficients. */
170  complexf_t eq_coeff[V27TER_EQUALIZER_LEN];
171  /*! \brief A saved set of adaptive equalizer coefficients for use after restarts. */
172  complexf_t eq_coeff_save[V27TER_EQUALIZER_LEN];
173  /*! \brief The equalizer signal buffer. */
174  complexf_t eq_buf[V27TER_EQUALIZER_LEN];
175 #endif
176 
177  /*! \brief Integration variable for damping the Gardner algorithm tests. */
179  /*! \brief Current step size of Gardner algorithm integration. */
181  /*! \brief The total symbol timing correction since the carrier came up.
182  This is only for performance analysis purposes. */
184 
185  /*! \brief Starting phase angles for the coarse carrier aquisition step. */
186  int32_t start_angles[2];
187  /*! \brief History list of phase angles for the coarse carrier aquisition step. */
188  int32_t angles[16];
189  /*! \brief Error and flow logging control */
191 };
192 
193 #endif
194 /*- End of file ------------------------------------------------------------*/
qam_report_handler_t qam_report
A callback function which may be enabled to report every symbol's constellation position.
Definition: private/v27ter_rx.h:67
modem_rx_status_func_t status_handler
The callback function used to report modem status changes.
Definition: private/v27ter_rx.h:61
complexf_t eq_buf[32]
The equalizer signal buffer.
Definition: private/v27ter_rx.h:174
void * status_user_data
A user specified opaque pointer passed to the status function.
Definition: private/v27ter_rx.h:63
put_bit_func_t put_bit
The callback function used to put each bit received.
Definition: private/v27ter_rx.h:56
int constellation_state
The position of the current symbol in the constellation, used for differential decoding.
Definition: private/v27ter_rx.h:110
int32_t angles[16]
History list of phase angles for the coarse carrier aquisition step.
Definition: private/v27ter_rx.h:188
complexf_t eq_coeff[32]
The adaptive equalizer coefficients.
Definition: private/v27ter_rx.h:170
int old_train
TRUE if the previous trained values are to be reused.
Definition: private/v27ter_rx.h:89
power_meter_t power
A power meter, to measure the HPF'ed signal power in the channel.
Definition: private/v27ter_rx.h:131
int training_stage
The section of the training data we are currently in.
Definition: private/v27ter_rx.h:91
int training_count
A count of how far through the current training step we are.
Definition: private/v27ter_rx.h:93
void(* put_bit_func_t)(void *user_data, int bit)
Definition: async.h:99
int total_baud_timing_correction
The total symbol timing correction since the carrier came up. This is only for performance analysis p...
Definition: private/v27ter_rx.h:183
int eq_put_step
Current write offset into the equalizer buffer.
Definition: private/v27ter_rx.h:140
float training_error
A measure of how much mismatch there is between the real constellation, and the decoded symbol positi...
Definition: private/v27ter_rx.h:96
unsigned int scramble_reg
The register for the training and data scrambler.
Definition: private/v27ter_rx.h:82
int16_t last_sample
The value of the last signal sample, using the a simple HPF for signal power estimation.
Definition: private/v27ter_rx.h:98
int bit_rate
The bit rate of the modem. Valid values are 2400 and 4800.
Definition: private/v27ter_rx.h:54
int gardner_step
Current step size of Gardner algorithm integration.
Definition: private/v27ter_rx.h:180
complexf_t eq_coeff_save[32]
A saved set of adaptive equalizer coefficients for use after restarts.
Definition: private/v27ter_rx.h:172
int eq_step
Current read offset into the equalizer buffer.
Definition: private/v27ter_rx.h:138
int gardner_integrate
Integration variable for damping the Gardner algorithm tests.
Definition: private/v27ter_rx.h:178
int32_t carrier_phase_rate
The update rate for the phase of the carrier (i.e. the DDS increment).
Definition: private/v27ter_rx.h:115
int16_t high_sample
A highest magnitude sample seen.
Definition: private/v27ter_rx.h:106
int training_bc
The current step in the table of BC constellation positions.
Definition: private/v27ter_rx.h:87
int eq_skip
Symbol counter to the next equalizer update.
Definition: private/v27ter_rx.h:142
float agc_scaling
The scaling factor accessed by the AGC algorithm.
Definition: private/v27ter_rx.h:163
void * qam_user_data
A user specified opaque pointer passed to the qam_report callback routine.
Definition: private/v27ter_rx.h:70
Definition: complex.h:42
float eq_delta
The current delta factor for updating the equalizer coefficients.
Definition: private/v27ter_rx.h:168
int32_t carrier_phase_rate_save
The carrier update rate saved for reuse when using short training.
Definition: private/v27ter_rx.h:117
int low_samples
A count of the current consecutive samples below the carrier off threshold.
Definition: private/v27ter_rx.h:104
uint32_t carrier_phase
The current phase of the carrier (i.e. the DDS parameter).
Definition: private/v27ter_rx.h:113
Definition: private/logging.h:33
float carrier_track_i
The integral part of the carrier tracking filter.
Definition: private/v27ter_rx.h:127
int32_t carrier_on_power
The power meter level at which carrier on is declared.
Definition: private/v27ter_rx.h:133
float carrier_track_p
The proportional part of the carrier tracking filter.
Definition: private/v27ter_rx.h:125
Definition: private/v27ter_rx.h:51
int32_t start_angles[2]
Starting phase angles for the coarse carrier aquisition step.
Definition: private/v27ter_rx.h:186
int signal_present
>0 if a signal above the minimum is present. It may or may not be a V.27ter signal.
Definition: private/v27ter_rx.h:100
void(* modem_rx_status_func_t)(void *user_data, int status)
Definition: async.h:108
int32_t carrier_off_power
The power meter level at which carrier off is declared.
Definition: private/v27ter_rx.h:135
float agc_scaling_save
The previous value of agc_scaling, needed to reuse old training.
Definition: private/v27ter_rx.h:165
int baud_half
The current half of the baud.
Definition: private/v27ter_rx.h:145
Definition: power_meter.h:48
logging_state_t logging
Error and flow logging control.
Definition: private/v27ter_rx.h:190
int carrier_drop_pending
Whether or not a carrier drop was detected and the signal delivery is pending.
Definition: private/v27ter_rx.h:102
int scrambler_pattern_count
A counter for the number of consecutive bits of repeating pattern through the scrambler.
Definition: private/v27ter_rx.h:85
float rrc_filter[27]
The route raised cosine (RRC) pulse shaping filter buffer.
Definition: private/v27ter_rx.h:76
void * put_bit_user_data
A user specified opaque pointer passed to the put_bit routine.
Definition: private/v27ter_rx.h:58
int rrc_filter_step
Current offset into the RRC pulse shaping filter buffer.
Definition: private/v27ter_rx.h:79