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costas tuning updates

This commit is contained in:
Max 2014-11-30 11:25:24 -05:00
parent 2051a96198
commit d6807f5575
1 changed files with 63 additions and 3 deletions
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66
op25/gr-op25_repeater/lib/gardner_costas_cc_impl.cc
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@ -34,6 +34,8 @@
#include <cstdio>
#include <string.h>
#include "p25_frame.h"
#define ENABLE_COSTAS_CQPSK_HACK 0
static const float M_TWOPI = 2 * M_PI;
@ -45,6 +47,58 @@ static const int NUM_COMPLEX=100;
namespace gr {
namespace op25_repeater {
// count no. of 1 bits in masked, xor'ed, FS, return true if < threshold
static inline bool check_frame_sync(uint64_t ch, int err_threshold, int len) {
int errs=0;
for (int i=0; i < len; i++) {
errs += (ch & 1);
ch = ch >> 1;
}
if (errs <= err_threshold) return true;
return false;
}
static inline std::complex<float> sgn(std::complex<float>c) {
if (c == std::complex<float>(0.0,0.0))
return std::complex<float>(0.0, 0.0);
return c/abs(c);
}
uint8_t gardner_costas_cc_impl::slicer(float sym) {
uint8_t dibit = 0;
static const float PI_4 = M_PI / 4.0;
static const float d_slice_levels[4] = {-2.0*PI_4, 0.0*PI_4, 2.0*PI_4, 4.0*PI_4};
if (d_slice_levels[3] < 0) {
dibit = 1;
if (d_slice_levels[3] <= sym && sym < d_slice_levels[0])
dibit = 3;
} else {
dibit = 3;
if (d_slice_levels[2] <= sym && sym < d_slice_levels[3])
dibit = 1;
}
if (d_slice_levels[0] <= sym && sym < d_slice_levels[1])
dibit = 2;
if (d_slice_levels[1] <= sym && sym < d_slice_levels[2])
dibit = 0;
nid_accum <<= 2;
nid_accum |= dibit;
if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ P25_FRAME_SYNC_MAGIC, 0, 48)) {
// fprintf(stderr, "P25P1 Framing detect\n");
}
if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ 0x001050551155LL, 0, 48)) {
fprintf(stderr, "tuning error -1200\n");
}
if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ 0xFFEFAFAAEEAALL, 0, 48)) {
fprintf(stderr, "tuning error +1200\n");
}
if(check_frame_sync((nid_accum & P25_FRAME_SYNC_MASK) ^ 0xAA8A0A008800LL, 0, 48)) {
fprintf(stderr, "tuning error +/- 2400\n");
}
return dibit;
}
gardner_costas_cc::sptr
gardner_costas_cc::make(float samples_per_symbol, float gain_mu, float gain_omega, float alpha, float beta, float max_freq, float min_freq)
{
@ -70,7 +124,8 @@ namespace gr {
d_dl_index(0),
d_alpha(alpha), d_beta(beta),
d_interp_counter(0),
d_theta(M_PI / 4.0), d_phase(0), d_freq(0), d_max_freq(max_freq)
d_theta(M_PI / 4.0), d_phase(0), d_freq(0), d_max_freq(max_freq),
nid_accum(0)
{
set_omega(samples_per_symbol);
set_relative_rate (1.0 / d_omega);
@ -140,7 +195,7 @@ gardner_costas_cc_impl::phase_error_tracking(gr_complex sample)
#endif /* ENABLE_COSTAS_CQPSK_HACK */
// Make phase and frequency corrections based on sampled value
phase_error = -phase_error_detector_qpsk(sample);
phase_error = phase_error_detector_qpsk(sample);
d_freq += d_beta*phase_error*abs(sample); // adjust frequency based on error
d_phase += d_freq + d_alpha*phase_error*abs(sample); // adjust phase based on error
@ -214,8 +269,13 @@ gardner_costas_cc_impl::general_work (int noutput_items,
float error_real = (d_last_sample.real() - interp_samp.real()) * interp_samp_mid.real();
float error_imag = (d_last_sample.imag() - interp_samp.imag()) * interp_samp_mid.imag();
gr_complex diffdec = interp_samp * conj(d_last_sample);
(void)slicer(std::arg(diffdec));
d_last_sample = interp_samp; // save for next time
#if 1
float symbol_error = error_real + error_imag; // Gardner loop error
#else
float symbol_error = ((sgn(interp_samp) - sgn(d_last_sample)) * conj(interp_samp_mid)).real();
#endif
if (isnan(symbol_error)) symbol_error = 0.0;
if (symbol_error < -1.0) symbol_error = -1.0;
if (symbol_error > 1.0) symbol_error = 1.0;
@ -227,7 +287,7 @@ gardner_costas_cc_impl::general_work (int noutput_items,
#endif
d_mu += d_omega + d_gain_mu * symbol_error; // update mu based on loop error
phase_error_tracking(diffdec);
phase_error_tracking(diffdec * PT_45);
out[o++] = interp_samp;
}