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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
48 * This block takes care of receiving M-PSK modulated signals through phase, frequency, and symbol
49 * synchronization. It performs carrier frequency and phase locking as well as symbol timing recovery.
50 * It works with (D)BPSK, (D)QPSK, and (D)8PSK as tested currently. It should also work for OQPSK and
53 * The phase and frequency synchronization are based on a Costas loop that finds the error of the incoming
54 * signal point compared to its nearest constellation point. The frequency and phase of the NCO are
55 * updated according to this error. There are optimized phase error detectors for BPSK and QPSK, but 8PSK
56 * is done using a brute-force computation of the constellation points to find the minimum.
58 * The symbol synchronization is done using a modified Mueller and Muller circuit from the paper:
60 * G. R. Danesfahani, T.G. Jeans, "Optimisation of modified Mueller and Muller
61 * algorithm," Electronics Letters, Vol. 31, no. 13, 22 June 1995, pp. 1032 - 1033.
63 * This circuit interpolates the downconverted sample (using the NCO developed by the Costas loop)
64 * every mu samples, then it finds the sampling error based on this and the past symbols and the decision
65 * made on the samples. Like the phase error detector, there are optimized decision algorithms for BPSK
66 * and QPKS, but 8PSK uses another brute force computation against all possible symbols. The modifications
67 * to the M&M used here reduce self-noise.
71 class gr_mpsk_receiver_cc : public gr_block
74 ~gr_mpsk_receiver_cc ();
75 void forecast(int noutput_items, gr_vector_int &ninput_items_required);
76 int general_work (int noutput_items,
77 gr_vector_int &ninput_items,
78 gr_vector_const_void_star &input_items,
79 gr_vector_void_star &output_items);
82 // Member functions related to the symbol tracking portion of the receiver
83 //! (M&M) Returns current value of mu
84 float mu() const { return d_mu;}
86 //! (M&M) Returns current value of omega
87 float omega() const { return d_omega;}
89 //! (M&M) Returns mu gain factor
90 float gain_mu() const { return d_gain_mu;}
92 //! (M&M) Returns omega gain factor
93 float gain_omega() const { return d_gain_omega;}
95 //! (M&M) Sets value of mu
96 void set_mu (float mu) { d_mu = mu; }
98 //! (M&M) Sets value of omega and its min and max values
99 void set_omega (float omega) {
101 d_min_omega = omega*(1.0 - d_omega_rel);
102 d_max_omega = omega*(1.0 + d_omega_rel);
103 d_omega_mid = 0.5*(d_min_omega+d_max_omega);
106 //! (M&M) Sets value for mu gain factor
107 void set_gain_mu (float gain_mu) { d_gain_mu = gain_mu; }
109 //! (M&M) Sets value for omega gain factor
110 void set_gain_omega (float gain_omega) { d_gain_omega = gain_omega; }
114 // Member function related to the phase/frequency tracking portion of the receiver
115 //! (CL) Returns the value for alpha (the phase gain term)
116 float alpha() const { return d_alpha; }
118 //! (CL) Returns the value of beta (the frequency gain term)
119 float beta() const { return d_beta; }
121 //! (CL) Returns the current value of the frequency of the NCO in the Costas loop
122 float freq() const { return d_freq; }
124 //! (CL) Returns the current value of the phase of the NCO in the Costal loop
125 float phase() const { return d_phase; }
127 //! (CL) Sets the value for alpha (the phase gain term)
128 void set_alpha(float alpha) { d_alpha = alpha; }
130 //! (CL) Setss the value of beta (the frequency gain term)
131 void set_beta(float beta) { d_beta = beta; }
133 //! (CL) Sets the current value of the frequency of the NCO in the Costas loop
134 void set_freq(float freq) { d_freq = freq; }
136 //! (CL) Setss the current value of the phase of the NCO in the Costal loop
137 void set_phase(float phase) { d_phase = phase; }
143 * \brief Constructor to synchronize incoming M-PSK symbols
145 * \param M modulation order of the M-PSK modulation
146 * \param theta any constant phase rotation from the real axis of the constellation
147 * \param alpha gain parameter to adjust the phase in the Costas loop (~0.01)
148 * \param beta gain parameter to adjust the frequency in the Costas loop (~alpha^2/4)
149 * \param fmin minimum normalized frequency value the loop can achieve
150 * \param fmax maximum normalized frequency value the loop can achieve
151 * \param mu initial parameter for the interpolator [0,1]
152 * \param gain_mu gain parameter of the M&M error signal to adjust mu (~0.05)
153 * \param omega initial value for the number of symbols between samples (~number of samples/symbol)
154 * \param gain_omega gain parameter to adjust omega based on the error (~omega^2/4)
155 * \param omega_rel sets the maximum (omega*(1+omega_rel)) and minimum (omega*(1+omega_rel)) omega (~0.005)
157 * The constructor also chooses which phase detector and decision maker to use in the work loop based on the
160 gr_mpsk_receiver_cc (unsigned int M, float theta,
161 float alpha, float beta,
162 float fmin, float fmax,
163 float mu, float gain_mu,
164 float omega, float gain_omega, float omega_rel);
166 void make_constellation();
167 void mm_sampler(const gr_complex symbol);
168 void mm_error_tracking(gr_complex sample);
169 void phase_error_tracking(gr_complex sample);
173 * \brief Phase error detector for MPSK modulations.
175 * \param sample the I&Q sample from which to determine the phase error
177 * This function determines the phase error for any MPSK signal by creating a set of PSK constellation points
178 * and doing a brute-force search to see which point minimizes the Euclidean distance. This point is then used
179 * to derotate the sample to the real-axis and a atan (using the fast approximation function) to determine the
180 * phase difference between the incoming sample and the real constellation point
182 * This should be cleaned up and made more efficient.
184 * \returns the approximated phase error.
186 float phase_error_detector_generic(gr_complex sample) const; // generic for M but more costly
189 * \brief Phase error detector for BPSK modulation.
191 * \param sample the I&Q sample from which to determine the phase error
193 * This function determines the phase error using a simple BPSK phase error detector by multiplying the real
194 * and imaginary (the error signal) components together. As the imaginary part goes to 0, so does this error.
196 * \returns the approximated phase error.
198 float phase_error_detector_bpsk(gr_complex sample) const; // optimized for BPSK
201 * \brief Phase error detector for QPSK modulation.
203 * \param sample the I&Q sample from which to determine the phase error
205 * This function determines the phase error using the limiter approach in a standard 4th order Costas loop
207 * \returns the approximated phase error.
209 float phase_error_detector_qpsk(gr_complex sample) const;
214 * \brief Decision maker for a generic MPSK constellation.
216 * \param sample the baseband I&Q sample from which to make the decision
218 * This decision maker is a generic implementation that does a brute-force search
219 * for the constellation point that minimizes the error between it and the incoming signal.
221 * \returns the index to d_constellation that minimizes the error/
223 unsigned int decision_generic(gr_complex sample) const;
227 * \brief Decision maker for BPSK constellation.
229 * \param sample the baseband I&Q sample from which to make the decision
231 * This decision maker is a simple slicer function that makes a decision on the symbol based on its
232 * placement on the real axis of greater than 0 or less than 0; the quadrature component is always 0.
234 * \returns the index to d_constellation that minimizes the error/
236 unsigned int decision_bpsk(gr_complex sample) const;
240 * \brief Decision maker for QPSK constellation.
242 * \param sample the baseband I&Q sample from which to make the decision
244 * This decision maker is a simple slicer function that makes a decision on the symbol based on its
245 * placement versus both axes and returns which quadrant the symbol is in.
247 * \returns the index to d_constellation that minimizes the error/
249 unsigned int decision_qpsk(gr_complex sample) const;
255 // Members related to carrier and phase tracking
258 float d_freq, d_max_freq, d_min_freq;
262 * \brief Decision maker function pointer
264 * \param sample the baseband I&Q sample from which to make the decision
266 * This is a function pointer that is set in the constructor to point to the proper decision function
267 * for the specified constellation order.
269 * \return index into d_constellation point that is the closest to the recieved sample
271 unsigned int (gr_mpsk_receiver_cc::*d_decision)(gr_complex sample) const; // pointer to decision function
274 std::vector<gr_complex> d_constellation;
275 unsigned int d_current_const_point;
277 // Members related to symbol timing
278 float d_mu, d_gain_mu;
279 float d_omega, d_gain_omega, d_omega_rel, d_max_omega, d_min_omega, d_omega_mid;
280 gr_complex d_p_2T, d_p_1T, d_p_0T;
281 gr_complex d_c_2T, d_c_1T, d_c_0T;
284 * \brief Phase error detector function pointer
286 * \param sample the I&Q sample from which to determine the phase error
288 * This is a function pointer that is set in the constructor to point to the proper phase error detector
289 * function for the specified constellation order.
291 float (gr_mpsk_receiver_cc::*d_phase_error_detector)(gr_complex sample) const;
294 //! get interpolated value
295 gri_mmse_fir_interpolator_cc *d_interp;
297 //! delay line length.
298 static const unsigned int DLLEN = 8;
300 //! delay line plus some length for overflow protection
301 gr_complex d_dl[2*DLLEN] __attribute__ ((aligned(8)));
303 //! index to delay line
304 unsigned int d_dl_idx;
306 friend gr_mpsk_receiver_cc_sptr
307 gr_make_mpsk_receiver_cc (unsigned int M, float theta,
308 float alpha, float beta,
309 float fmin, float fmax,
310 float mu, float gain_mu,
311 float omega, float gain_omega, float omega_rel);