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23 #ifndef INCLUDED_GR_MPSK_RECEIVER_CC_H
24 #define INCLUDED_GR_MPSK_RECEIVER_CC_H
27 #include <gr_complex.h>
30 class gri_mmse_fir_interpolator_cc;
32 class gr_mpsk_receiver_cc;
33 typedef boost::shared_ptr<gr_mpsk_receiver_cc> gr_mpsk_receiver_cc_sptr;
36 gr_mpsk_receiver_cc_sptr
37 gr_make_mpsk_receiver_cc (unsigned int M, float theta,
38 float alpha, float beta,
39 float fmin, float fmax,
40 float mu, float gain_mu,
41 float omega, float gain_omega, float omega_rel);
44 * \brief This block takes care of receiving M-PSK modulated signals through phase, frequency, and symbol
49 * This block takes care of receiving M-PSK modulated signals through phase, frequency, and symbol
50 * synchronization. It performs carrier frequency and phase locking as well as symbol timing recovery.
51 * It works with (D)BPSK, (D)QPSK, and (D)8PSK as tested currently. It should also work for OQPSK and
54 * The phase and frequency synchronization are based on a Costas loop that finds the error of the incoming
55 * signal point compared to its nearest constellation point. The frequency and phase of the NCO are
56 * updated according to this error. There are optimized phase error detectors for BPSK and QPSK, but 8PSK
57 * is done using a brute-force computation of the constellation points to find the minimum.
59 * The symbol synchronization is done using a modified Mueller and Muller circuit from the paper:
61 * G. R. Danesfahani, T.G. Jeans, "Optimisation of modified Mueller and Muller
62 * algorithm," Electronics Letters, Vol. 31, no. 13, 22 June 1995, pp. 1032 - 1033.
64 * This circuit interpolates the downconverted sample (using the NCO developed by the Costas loop)
65 * every mu samples, then it finds the sampling error based on this and the past symbols and the decision
66 * made on the samples. Like the phase error detector, there are optimized decision algorithms for BPSK
67 * and QPKS, but 8PSK uses another brute force computation against all possible symbols. The modifications
68 * to the M&M used here reduce self-noise.
72 class gr_mpsk_receiver_cc : public gr_block
75 ~gr_mpsk_receiver_cc ();
76 void forecast(int noutput_items, gr_vector_int &ninput_items_required);
77 int general_work (int noutput_items,
78 gr_vector_int &ninput_items,
79 gr_vector_const_void_star &input_items,
80 gr_vector_void_star &output_items);
83 // Member functions related to the symbol tracking portion of the receiver
84 //! (M&M) Returns current value of mu
85 float mu() const { return d_mu;}
87 //! (M&M) Returns current value of omega
88 float omega() const { return d_omega;}
90 //! (M&M) Returns mu gain factor
91 float gain_mu() const { return d_gain_mu;}
93 //! (M&M) Returns omega gain factor
94 float gain_omega() const { return d_gain_omega;}
96 //! (M&M) Sets value of mu
97 void set_mu (float mu) { d_mu = mu; }
99 //! (M&M) Sets value of omega and its min and max values
100 void set_omega (float omega) {
102 d_min_omega = omega*(1.0 - d_omega_rel);
103 d_max_omega = omega*(1.0 + d_omega_rel);
104 d_omega_mid = 0.5*(d_min_omega+d_max_omega);
107 //! (M&M) Sets value for mu gain factor
108 void set_gain_mu (float gain_mu) { d_gain_mu = gain_mu; }
110 //! (M&M) Sets value for omega gain factor
111 void set_gain_omega (float gain_omega) { d_gain_omega = gain_omega; }
115 // Member function related to the phase/frequency tracking portion of the receiver
116 //! (CL) Returns the value for alpha (the phase gain term)
117 float alpha() const { return d_alpha; }
119 //! (CL) Returns the value of beta (the frequency gain term)
120 float beta() const { return d_beta; }
122 //! (CL) Returns the current value of the frequency of the NCO in the Costas loop
123 float freq() const { return d_freq; }
125 //! (CL) Returns the current value of the phase of the NCO in the Costal loop
126 float phase() const { return d_phase; }
128 //! (CL) Sets the value for alpha (the phase gain term)
129 void set_alpha(float alpha) { d_alpha = alpha; }
131 //! (CL) Setss the value of beta (the frequency gain term)
132 void set_beta(float beta) { d_beta = beta; }
134 //! (CL) Sets the current value of the frequency of the NCO in the Costas loop
135 void set_freq(float freq) { d_freq = freq; }
137 //! (CL) Setss the current value of the phase of the NCO in the Costal loop
138 void set_phase(float phase) { d_phase = phase; }
144 * \brief Constructor to synchronize incoming M-PSK symbols
146 * \param M modulation order of the M-PSK modulation
147 * \param theta any constant phase rotation from the real axis of the constellation
148 * \param alpha gain parameter to adjust the phase in the Costas loop (~0.01)
149 * \param beta gain parameter to adjust the frequency in the Costas loop (~alpha^2/4)
150 * \param fmin minimum normalized frequency value the loop can achieve
151 * \param fmax maximum normalized frequency value the loop can achieve
152 * \param mu initial parameter for the interpolator [0,1]
153 * \param gain_mu gain parameter of the M&M error signal to adjust mu (~0.05)
154 * \param omega initial value for the number of symbols between samples (~number of samples/symbol)
155 * \param gain_omega gain parameter to adjust omega based on the error (~omega^2/4)
156 * \param omega_rel sets the maximum (omega*(1+omega_rel)) and minimum (omega*(1+omega_rel)) omega (~0.005)
158 * The constructor also chooses which phase detector and decision maker to use in the work loop based on the
161 gr_mpsk_receiver_cc (unsigned int M, float theta,
162 float alpha, float beta,
163 float fmin, float fmax,
164 float mu, float gain_mu,
165 float omega, float gain_omega, float omega_rel);
167 void make_constellation();
168 void mm_sampler(const gr_complex symbol);
169 void mm_error_tracking(gr_complex sample);
170 void phase_error_tracking(gr_complex sample);
174 * \brief Phase error detector for MPSK modulations.
176 * \param sample the I&Q sample from which to determine the phase error
178 * This function determines the phase error for any MPSK signal by creating a set of PSK constellation points
179 * and doing a brute-force search to see which point minimizes the Euclidean distance. This point is then used
180 * to derotate the sample to the real-axis and a atan (using the fast approximation function) to determine the
181 * phase difference between the incoming sample and the real constellation point
183 * This should be cleaned up and made more efficient.
185 * \returns the approximated phase error.
187 float phase_error_detector_generic(gr_complex sample) const; // generic for M but more costly
190 * \brief Phase error detector for BPSK modulation.
192 * \param sample the I&Q sample from which to determine the phase error
194 * This function determines the phase error using a simple BPSK phase error detector by multiplying the real
195 * and imaginary (the error signal) components together. As the imaginary part goes to 0, so does this error.
197 * \returns the approximated phase error.
199 float phase_error_detector_bpsk(gr_complex sample) const; // optimized for BPSK
202 * \brief Phase error detector for QPSK modulation.
204 * \param sample the I&Q sample from which to determine the phase error
206 * This function determines the phase error using the limiter approach in a standard 4th order Costas loop
208 * \returns the approximated phase error.
210 float phase_error_detector_qpsk(gr_complex sample) const;
215 * \brief Decision maker for a generic MPSK constellation.
217 * \param sample the baseband I&Q sample from which to make the decision
219 * This decision maker is a generic implementation that does a brute-force search
220 * for the constellation point that minimizes the error between it and the incoming signal.
222 * \returns the index to d_constellation that minimizes the error/
224 unsigned int decision_generic(gr_complex sample) const;
228 * \brief Decision maker for BPSK constellation.
230 * \param sample the baseband I&Q sample from which to make the decision
232 * This decision maker is a simple slicer function that makes a decision on the symbol based on its
233 * placement on the real axis of greater than 0 or less than 0; the quadrature component is always 0.
235 * \returns the index to d_constellation that minimizes the error/
237 unsigned int decision_bpsk(gr_complex sample) const;
241 * \brief Decision maker for QPSK constellation.
243 * \param sample the baseband I&Q sample from which to make the decision
245 * This decision maker is a simple slicer function that makes a decision on the symbol based on its
246 * placement versus both axes and returns which quadrant the symbol is in.
248 * \returns the index to d_constellation that minimizes the error/
250 unsigned int decision_qpsk(gr_complex sample) const;
256 // Members related to carrier and phase tracking
259 float d_freq, d_max_freq, d_min_freq;
263 * \brief Decision maker function pointer
265 * \param sample the baseband I&Q sample from which to make the decision
267 * This is a function pointer that is set in the constructor to point to the proper decision function
268 * for the specified constellation order.
270 * \return index into d_constellation point that is the closest to the recieved sample
272 unsigned int (gr_mpsk_receiver_cc::*d_decision)(gr_complex sample) const; // pointer to decision function
275 std::vector<gr_complex> d_constellation;
276 unsigned int d_current_const_point;
278 // Members related to symbol timing
279 float d_mu, d_gain_mu;
280 float d_omega, d_gain_omega, d_omega_rel, d_max_omega, d_min_omega, d_omega_mid;
281 gr_complex d_p_2T, d_p_1T, d_p_0T;
282 gr_complex d_c_2T, d_c_1T, d_c_0T;
285 * \brief Phase error detector function pointer
287 * \param sample the I&Q sample from which to determine the phase error
289 * This is a function pointer that is set in the constructor to point to the proper phase error detector
290 * function for the specified constellation order.
292 float (gr_mpsk_receiver_cc::*d_phase_error_detector)(gr_complex sample) const;
295 //! get interpolated value
296 gri_mmse_fir_interpolator_cc *d_interp;
298 //! delay line length.
299 static const unsigned int DLLEN = 8;
301 //! delay line plus some length for overflow protection
302 gr_complex d_dl[2*DLLEN] __attribute__ ((aligned(8)));
304 //! index to delay line
305 unsigned int d_dl_idx;
307 friend gr_mpsk_receiver_cc_sptr
308 gr_make_mpsk_receiver_cc (unsigned int M, float theta,
309 float alpha, float beta,
310 float fmin, float fmax,
311 float mu, float gain_mu,
312 float omega, float gain_omega, float omega_rel);