This block takes care of receiving M-PSK modulated signals through phase, frequency, and symbol synchronization.This block takes care of receiving M-PSK modulated signals through phase, frequency, and symbol synchronization. It performs carrier frequency and phase locking as well as symbol timing recovery. It works with (D)BPSK, (D)QPSK, and (D)8PSK as tested currently. It should also work for OQPSK and PI/4 DQPSK. More...
#include <digital_mpsk_receiver_cc.h>
Public Member Functions | |
| ~digital_mpsk_receiver_cc () | |
| void | forecast (int noutput_items, gr_vector_int &ninput_items_required) |
| Estimate input requirements given output request. | |
| int | general_work (int noutput_items, gr_vector_int &ninput_items, gr_vector_const_void_star &input_items, gr_vector_void_star &output_items) |
| compute output items from input items | |
| float | mu () const |
| (M&M) Returns current value of mu | |
| float | omega () const |
| (M&M) Returns current value of omega | |
| float | gain_mu () const |
| (M&M) Returns mu gain factor | |
| float | gain_omega () const |
| (M&M) Returns omega gain factor | |
| void | set_mu (float mu) |
| (M&M) Sets value of mu | |
| void | set_omega (float omega) |
| (M&M) Sets value of omega and its min and max values | |
| void | set_gain_mu (float gain_mu) |
| (M&M) Sets value for mu gain factor | |
| void | set_gain_omega (float gain_omega) |
| (M&M) Sets value for omega gain factor | |
Protected Member Functions | |
| digital_mpsk_receiver_cc (unsigned int M, float theta, float loop_bw, float fmin, float fmax, float mu, float gain_mu, float omega, float gain_omega, float omega_rel) | |
| Constructor to synchronize incoming M-PSK symbols. | |
| void | make_constellation () |
| void | mm_sampler (const gr_complex symbol) |
| void | mm_error_tracking (gr_complex sample) |
| void | phase_error_tracking (gr_complex sample) |
| float | phase_error_detector_generic (gr_complex sample) const |
| Phase error detector for MPSK modulations. | |
| float | phase_error_detector_bpsk (gr_complex sample) const |
| Phase error detector for BPSK modulation. | |
| float | phase_error_detector_qpsk (gr_complex sample) const |
| Phase error detector for QPSK modulation. | |
| unsigned int | decision_generic (gr_complex sample) const |
| Decision maker for a generic MPSK constellation. | |
| unsigned int | decision_bpsk (gr_complex sample) const |
| Decision maker for BPSK constellation. | |
| unsigned int | decision_qpsk (gr_complex sample) const |
| Decision maker for QPSK constellation. | |
Friends | |
| DIGITAL_API digital_mpsk_receiver_cc_sptr | digital_make_mpsk_receiver_cc (unsigned int M, float theta, float loop_bw, float fmin, float fmax, float mu, float gain_mu, float omega, float gain_omega, float omega_rel) |
Detailed Description
This block takes care of receiving M-PSK modulated signals through phase, frequency, and symbol synchronization.
This block takes care of receiving M-PSK modulated signals through phase, frequency, and symbol synchronization. It performs carrier frequency and phase locking as well as symbol timing recovery. It works with (D)BPSK, (D)QPSK, and (D)8PSK as tested currently. It should also work for OQPSK and PI/4 DQPSK.
The phase and frequency synchronization are based on a Costas loop that finds the error of the incoming signal point compared to its nearest constellation point. The frequency and phase of the NCO are updated according to this error. There are optimized phase error detectors for BPSK and QPSK, but 8PSK is done using a brute-force computation of the constellation points to find the minimum.
The symbol synchronization is done using a modified Mueller and Muller circuit from the paper:
G. R. Danesfahani, T.G. Jeans, "Optimisation of modified Mueller and Muller algorithm," Electronics Letters, Vol. 31, no. 13, 22 June 1995, pp. 1032 - 1033.
This circuit interpolates the downconverted sample (using the NCO developed by the Costas loop) every mu samples, then it finds the sampling error based on this and the past symbols and the decision made on the samples. Like the phase error detector, there are optimized decision algorithms for BPSK and QPKS, but 8PSK uses another brute force computation against all possible symbols. The modifications to the M&M used here reduce self-noise.
Constructor & Destructor Documentation
| digital_mpsk_receiver_cc::~digital_mpsk_receiver_cc | ( | ) |
| digital_mpsk_receiver_cc::digital_mpsk_receiver_cc | ( | unsigned int | M, |
| float | theta, | ||
| float | loop_bw, | ||
| float | fmin, | ||
| float | fmax, | ||
| float | mu, | ||
| float | gain_mu, | ||
| float | omega, | ||
| float | gain_omega, | ||
| float | omega_rel | ||
| ) | [protected] |
Constructor to synchronize incoming M-PSK symbols.
- Parameters:
-
M modulation order of the M-PSK modulation theta any constant phase rotation from the real axis of the constellation loop_bw Loop bandwidth to set gains of phase/freq tracking loop fmin minimum normalized frequency value the loop can achieve fmax maximum normalized frequency value the loop can achieve mu initial parameter for the interpolator [0,1] gain_mu gain parameter of the M&M error signal to adjust mu (~0.05) omega initial value for the number of symbols between samples (~number of samples/symbol) gain_omega gain parameter to adjust omega based on the error (~omega^2/4) omega_rel sets the maximum (omega*(1+omega_rel)) and minimum (omega*(1+omega_rel)) omega (~0.005)
The constructor also chooses which phase detector and decision maker to use in the work loop based on the value of M.
Member Function Documentation
| unsigned int digital_mpsk_receiver_cc::decision_bpsk | ( | gr_complex | sample | ) | const [protected] |
Decision maker for BPSK constellation.
- Parameters:
-
sample the baseband I&Q sample from which to make the decision
This decision maker is a simple slicer function that makes a decision on the symbol based on its placement on the real axis of greater than 0 or less than 0; the quadrature component is always 0.
- Returns:
- the index to d_constellation that minimizes the error/
| unsigned int digital_mpsk_receiver_cc::decision_generic | ( | gr_complex | sample | ) | const [protected] |
Decision maker for a generic MPSK constellation.
- Parameters:
-
sample the baseband I&Q sample from which to make the decision
This decision maker is a generic implementation that does a brute-force search for the constellation point that minimizes the error between it and the incoming signal.
- Returns:
- the index to d_constellation that minimizes the error/
| unsigned int digital_mpsk_receiver_cc::decision_qpsk | ( | gr_complex | sample | ) | const [protected] |
Decision maker for QPSK constellation.
- Parameters:
-
sample the baseband I&Q sample from which to make the decision
This decision maker is a simple slicer function that makes a decision on the symbol based on its placement versus both axes and returns which quadrant the symbol is in.
- Returns:
- the index to d_constellation that minimizes the error/
| void digital_mpsk_receiver_cc::forecast | ( | int | noutput_items, |
| gr_vector_int & | ninput_items_required | ||
| ) | [virtual] |
Estimate input requirements given output request.
- Parameters:
-
noutput_items number of output items to produce ninput_items_required number of input items required on each input stream
Given a request to product noutput_items, estimate the number of data items required on each input stream. The estimate doesn't have to be exact, but should be close.
Reimplemented from gr_block.
| float digital_mpsk_receiver_cc::gain_mu | ( | ) | const [inline] |
(M&M) Returns mu gain factor
| float digital_mpsk_receiver_cc::gain_omega | ( | ) | const [inline] |
(M&M) Returns omega gain factor
| int digital_mpsk_receiver_cc::general_work | ( | int | noutput_items, |
| gr_vector_int & | ninput_items, | ||
| gr_vector_const_void_star & | input_items, | ||
| gr_vector_void_star & | output_items | ||
| ) | [virtual] |
compute output items from input items
- Parameters:
-
noutput_items number of output items to write on each output stream ninput_items number of input items available on each input stream input_items vector of pointers to the input items, one entry per input stream output_items vector of pointers to the output items, one entry per output stream
- Returns:
- number of items actually written to each output stream, or -1 on EOF. It is OK to return a value less than noutput_items. -1 <= return value <= noutput_items
general_work must call consume or consume_each to indicate how many items were consumed on each input stream.
Implements gr_block.
| void digital_mpsk_receiver_cc::make_constellation | ( | ) | [protected] |
| void digital_mpsk_receiver_cc::mm_error_tracking | ( | gr_complex | sample | ) | [protected] |
| void digital_mpsk_receiver_cc::mm_sampler | ( | const gr_complex | symbol | ) | [protected] |
| float digital_mpsk_receiver_cc::mu | ( | ) | const [inline] |
(M&M) Returns current value of mu
| float digital_mpsk_receiver_cc::omega | ( | ) | const [inline] |
(M&M) Returns current value of omega
| float digital_mpsk_receiver_cc::phase_error_detector_bpsk | ( | gr_complex | sample | ) | const [protected] |
Phase error detector for BPSK modulation.
- Parameters:
-
sample the I&Q sample from which to determine the phase error
This function determines the phase error using a simple BPSK phase error detector by multiplying the real and imaginary (the error signal) components together. As the imaginary part goes to 0, so does this error.
- Returns:
- the approximated phase error.
| float digital_mpsk_receiver_cc::phase_error_detector_generic | ( | gr_complex | sample | ) | const [protected] |
Phase error detector for MPSK modulations.
- Parameters:
-
sample the I&Q sample from which to determine the phase error
This function determines the phase error for any MPSK signal by creating a set of PSK constellation points and doing a brute-force search to see which point minimizes the Euclidean distance. This point is then used to derotate the sample to the real-axis and a atan (using the fast approximation function) to determine the phase difference between the incoming sample and the real constellation point
This should be cleaned up and made more efficient.
- Returns:
- the approximated phase error.
| float digital_mpsk_receiver_cc::phase_error_detector_qpsk | ( | gr_complex | sample | ) | const [protected] |
Phase error detector for QPSK modulation.
- Parameters:
-
sample the I&Q sample from which to determine the phase error
This function determines the phase error using the limiter approach in a standard 4th order Costas loop
- Returns:
- the approximated phase error.
| void digital_mpsk_receiver_cc::phase_error_tracking | ( | gr_complex | sample | ) | [protected] |
| void digital_mpsk_receiver_cc::set_gain_mu | ( | float | gain_mu | ) | [inline] |
(M&M) Sets value for mu gain factor
| void digital_mpsk_receiver_cc::set_gain_omega | ( | float | gain_omega | ) | [inline] |
(M&M) Sets value for omega gain factor
| void digital_mpsk_receiver_cc::set_mu | ( | float | mu | ) | [inline] |
(M&M) Sets value of mu
| void digital_mpsk_receiver_cc::set_omega | ( | float | omega | ) | [inline] |
(M&M) Sets value of omega and its min and max values
Friends And Related Function Documentation
| DIGITAL_API digital_mpsk_receiver_cc_sptr digital_make_mpsk_receiver_cc | ( | unsigned int | M, |
| float | theta, | ||
| float | loop_bw, | ||
| float | fmin, | ||
| float | fmax, | ||
| float | mu, | ||
| float | gain_mu, | ||
| float | omega, | ||
| float | gain_omega, | ||
| float | omega_rel | ||
| ) | [friend] |
The documentation for this class was generated from the following file:
