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 #if defined(SPANDSP_USE_FIXED_POINT)
73  /*! \brief The scaling factor assessed by the AGC algorithm. */
74  int16_t agc_scaling;
75  /*! \brief The previous value of agc_scaling, needed to reuse old training. */
76  int16_t agc_scaling_save;
77 
78  /*! \brief The current delta factor for updating the equalizer coefficients. */
79  float eq_delta;
80  /*! \brief The adaptive equalizer coefficients. */
81  /*complexi16_t*/ complexf_t eq_coeff[V27TER_EQUALIZER_LEN];
82  /*! \brief A saved set of adaptive equalizer coefficients for use after restarts. */
83  /*complexi16_t*/ complexf_t eq_coeff_save[V27TER_EQUALIZER_LEN];
84  /*! \brief The equalizer signal buffer. */
85  /*complexi16_t*/ complexf_t eq_buf[V27TER_EQUALIZER_LEN];
86 
87  /*! \brief A measure of how much mismatch there is between the real constellation,
88  and the decoded symbol positions. */
89  float training_error;
90 
91  /*! \brief The proportional part of the carrier tracking filter. */
92  float carrier_track_p;
93  /*! \brief The integral part of the carrier tracking filter. */
94  float carrier_track_i;
95  /*! \brief The root raised cosine (RRC) pulse shaping filter buffer. */
96  int16_t rrc_filter[V27TER_RX_FILTER_STEPS];
97 #else
98  /*! \brief The scaling factor assessed by the AGC algorithm. */
99  float agc_scaling;
100  /*! \brief The previous value of agc_scaling, needed to reuse old training. */
102 
103  /*! \brief The current delta factor for updating the equalizer coefficients. */
104  float eq_delta;
105  /*! \brief The adaptive equalizer coefficients. */
106  complexf_t eq_coeff[V27TER_EQUALIZER_LEN];
107  /*! \brief A saved set of adaptive equalizer coefficients for use after restarts. */
108  complexf_t eq_coeff_save[V27TER_EQUALIZER_LEN];
109  /*! \brief The equalizer signal buffer. */
110  complexf_t eq_buf[V27TER_EQUALIZER_LEN];
111 
112  /*! \brief A measure of how much mismatch there is between the real constellation,
113  and the decoded symbol positions. */
115 
116  /*! \brief The proportional part of the carrier tracking filter. */
118  /*! \brief The integral part of the carrier tracking filter. */
120  /*! \brief The root raised cosine (RRC) pulse shaping filter buffer. */
121  float rrc_filter[V27TER_RX_FILTER_STEPS];
122 #endif
123  /*! \brief Current offset into the RRC pulse shaping filter buffer. */
125 
126  /*! \brief The register for the training and data scrambler. */
127  uint32_t scramble_reg;
128  /*! \brief A counter for the number of consecutive bits of repeating pattern through
129  the scrambler. */
131  /*! \brief The current step in the table of BC constellation positions. */
133  /*! \brief TRUE if the previous trained values are to be reused. */
135  /*! \brief The section of the training data we are currently in. */
137  /*! \brief A count of how far through the current training step we are. */
139  /*! \brief The value of the last signal sample, using the a simple HPF for signal power estimation. */
140  int16_t last_sample;
141  /*! \brief >0 if a signal above the minimum is present. It may or may not be a V.27ter signal. */
143  /*! \brief Whether or not a carrier drop was detected and the signal delivery is pending. */
145  /*! \brief A count of the current consecutive samples below the carrier off threshold. */
147  /*! \brief A highest magnitude sample seen. */
148  int16_t high_sample;
149 
150  /*! \brief The position of the current symbol in the constellation, used for
151  differential decoding. */
153 
154  /*! \brief The current phase of the carrier (i.e. the DDS parameter). */
155  uint32_t carrier_phase;
156  /*! \brief The update rate for the phase of the carrier (i.e. the DDS increment). */
158  /*! \brief The carrier update rate saved for reuse when using short training. */
160 
161  /*! \brief A power meter, to measure the HPF'ed signal power in the channel. */
163  /*! \brief The power meter level at which carrier on is declared. */
165  /*! \brief The power meter level at which carrier off is declared. */
167 
168  /*! \brief Current read offset into the equalizer buffer. */
169  int eq_step;
170  /*! \brief Current write offset into the equalizer buffer. */
172  /*! \brief Symbol counter to the next equalizer update. */
173  int eq_skip;
174 
175  /*! \brief The current half of the baud. */
177 
178  /*! \brief Integration variable for damping the Gardner algorithm tests. */
180  /*! \brief Current step size of Gardner algorithm integration. */
182  /*! \brief The total symbol timing correction since the carrier came up.
183  This is only for performance analysis purposes. */
185 
186  /*! \brief The previous symbol phase angles for the coarse carrier aquisition step. */
187  int32_t last_angles[2];
188  /*! \brief History list of phase angle differences for the coarse carrier aquisition step. */
189  int32_t diff_angles[16];
190 
191  /*! \brief Error and flow logging control */
193 };
194 
195 #endif
196 /*- End of file ------------------------------------------------------------*/
qam_report_handler_t qam_report
A callback function which may be enabled to report every symbol&#39;s constellation position.
Definition: private/v27ter_rx.h:67
complexf_t eq_buf[32]
The equalizer signal buffer.
Definition: private/v27ter_rx.h:110
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:152
int32_t diff_angles[16]
History list of phase angle differences for the coarse carrier aquisition step.
Definition: private/v27ter_rx.h:189
int32_t last_angles[2]
The previous symbol phase angles for the coarse carrier aquisition step.
Definition: private/v27ter_rx.h:187
complexf_t eq_coeff[32]
The adaptive equalizer coefficients.
Definition: private/v27ter_rx.h:106
int old_train
TRUE if the previous trained values are to be reused.
Definition: private/v27ter_rx.h:134
power_meter_t power
A power meter, to measure the HPF&#39;ed signal power in the channel.
Definition: private/v27ter_rx.h:162
int training_stage
The section of the training data we are currently in.
Definition: private/v27ter_rx.h:136
int training_count
A count of how far through the current training step we are.
Definition: private/v27ter_rx.h:138
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:184
int eq_put_step
Current write offset into the equalizer buffer.
Definition: private/v27ter_rx.h:171
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:114
void(* put_bit_func_t)(void *user_data, int bit)
Definition: async.h:105
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:140
void(* modem_status_func_t)(void *user_data, int status)
Definition: async.h:114
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:181
complexf_t eq_coeff_save[32]
A saved set of adaptive equalizer coefficients for use after restarts.
Definition: private/v27ter_rx.h:108
int eq_step
Current read offset into the equalizer buffer.
Definition: private/v27ter_rx.h:169
int gardner_integrate
Integration variable for damping the Gardner algorithm tests.
Definition: private/v27ter_rx.h:179
int32_t carrier_phase_rate
The update rate for the phase of the carrier (i.e. the DDS increment).
Definition: private/v27ter_rx.h:157
int16_t high_sample
A highest magnitude sample seen.
Definition: private/v27ter_rx.h:148
int training_bc
The current step in the table of BC constellation positions.
Definition: private/v27ter_rx.h:132
uint32_t scramble_reg
The register for the training and data scrambler.
Definition: private/v27ter_rx.h:127
int eq_skip
Symbol counter to the next equalizer update.
Definition: private/v27ter_rx.h:173
float agc_scaling
The scaling factor assessed by the AGC algorithm.
Definition: private/v27ter_rx.h:99
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:104
int32_t carrier_phase_rate_save
The carrier update rate saved for reuse when using short training.
Definition: private/v27ter_rx.h:159
float rrc_filter[27]
The root raised cosine (RRC) pulse shaping filter buffer.
Definition: private/v27ter_rx.h:121
int low_samples
A count of the current consecutive samples below the carrier off threshold.
Definition: private/v27ter_rx.h:146
uint32_t carrier_phase
The current phase of the carrier (i.e. the DDS parameter).
Definition: private/v27ter_rx.h:155
Definition: private/logging.h:33
float carrier_track_i
The integral part of the carrier tracking filter.
Definition: private/v27ter_rx.h:119
int32_t carrier_on_power
The power meter level at which carrier on is declared.
Definition: private/v27ter_rx.h:164
float carrier_track_p
The proportional part of the carrier tracking filter.
Definition: private/v27ter_rx.h:117
Definition: private/v27ter_rx.h:51
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:142
int32_t carrier_off_power
The power meter level at which carrier off is declared.
Definition: private/v27ter_rx.h:166
float agc_scaling_save
The previous value of agc_scaling, needed to reuse old training.
Definition: private/v27ter_rx.h:101
int baud_half
The current half of the baud.
Definition: private/v27ter_rx.h:176
Definition: power_meter.h:48
modem_status_func_t status_handler
The callback function used to report modem status changes.
Definition: private/v27ter_rx.h:61
logging_state_t logging
Error and flow logging control.
Definition: private/v27ter_rx.h:192
int carrier_drop_pending
Whether or not a carrier drop was detected and the signal delivery is pending.
Definition: private/v27ter_rx.h:144
int scrambler_pattern_count
A counter for the number of consecutive bits of repeating pattern through the scrambler.
Definition: private/v27ter_rx.h:130
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:124