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Add RRC filtering

pull/4/head
pabr 2017-03-02 11:07:52 +01:00
rodzic 2f3730e663
commit 80f68be185
1 zmienionych plików z 71 dodań i 43 usunięć
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114
src/apps/leandvb.cc
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@ -50,7 +50,9 @@ struct config {
bool hard_metric;
bool resample;
float resample_rej; // Approx. filter rejection in dB
bool rrc; // Apply root raised-cosine filter
enum { INTERP_NEAREST, INTERP_LINEAR, INTERP_RRC } interp;
int interp_ss; // Discrete steps between samples, 0=auto
float rrc_rej; // Approx. interpolation filter rejection in dB
float rolloff; // Roll-off 0..1
bool hdlc; // Expect HDLC frames instead of MPEG packets
@ -89,7 +91,9 @@ struct config {
hard_metric(false),
resample(false),
resample_rej(10),
rrc(false),
interp(config::INTERP_LINEAR),
interp_ss(0),
rrc_rej(10),
rolloff(0.35),
hdlc(false),
@ -253,7 +257,6 @@ int run(config &cfg) {
if ( cfg.verbose ) fprintf(stderr, "Roll-off %g\n", cfg.rolloff);
fir_filter<cf32,float> *r_resample = NULL;
fir_filter<cf32,float> *r_rrc = NULL;
int decim = 1;
@ -283,33 +286,13 @@ int run(config &cfg) {
#endif
int ncoeffs = filtergen::lowpass(order, Fcut, &coeffs);
filtergen::normalize_dcgain(ncoeffs, coeffs, 1);
if ( cfg.debug ) {
for ( int i=0; i<ncoeffs; ++i ) fprintf(stderr, "%f, ", coeffs[i]);
fprintf(stderr, "\n");
}
if ( cfg.debug ) filtergen::dump_filter("lowpass", ncoeffs, coeffs);
r_resample = new fir_filter<cf32,float>
(&sch, ncoeffs, coeffs, *p_preprocessed, *p_resampled, decim);
p_preprocessed = p_resampled;
cfg.Fs /= decim;
}
if ( cfg.rrc ) {
#if 1
fprintf(stderr, "RRC not implemented (ignoring).\n");
#else
float *coeffs;
int ncoeffs = filtergen::root_raised_cosine
(cfg.Fm/cfg.Fs, rolloff, &coeffs);
if ( cfg.verbose )
fprintf(stderr, "Inserting RRC filter, %d coeffs.\n", ncoeffs);
pipebuf<cf32> *p_rrc =
new pipebuf<cf32>(&sch, "rrc", BUF_BASEBAND);
r_rrc = new fir_filter<cf32,float>
(&sch, ncoeffs, coeffs, *p_preprocessed, *p_rrc);
p_preprocessed = p_rrc;
#endif
}
// DECIMATION
// (Unless already done in resampler)
@ -356,8 +339,39 @@ int run(config &cfg) {
pipebuf<f32> p_ss(&sch, "SS", BUF_SLOW);
pipebuf<f32> p_mer(&sch, "MER", BUF_SLOW);
pipebuf<cf32> p_sampled(&sch, "PSK symbols", BUF_BASEBAND);
// TBD retype preprocess as unsigned char
cstln_receiver<f32> demod(&sch, *p_preprocessed, p_symbols,
interpolator_interface<f32> *interpolator;
switch ( cfg.interp ) {
case config::INTERP_NEAREST:
interpolator = new nearest_interpolator<float>();
break;
case config::INTERP_LINEAR:
interpolator = new linear_interpolator<float>();
break;
case config::INTERP_RRC: {
float *coeffs;
if ( cfg.interp_ss == 0 ) {
// At least 16 discrete sampling points between symbols
cfg.interp_ss = max(1, (int)(16*cfg.Fm / cfg.Fs));
if ( cfg.verbose )
fprintf(stderr, "RRC interpolator: %d steps\n", cfg.interp_ss);
}
float Frrc = cfg.Fs * cfg.interp_ss; // Sample freq of the RRC filter
float transition = (cfg.Fm/2) * cfg.rolloff;
int order = cfg.rrc_rej * Frrc / (22*transition);
int ncoeffs = filtergen::root_raised_cosine
(order, cfg.Fm/Frrc, cfg.rolloff, &coeffs);
if ( cfg.verbose )
fprintf(stderr, "RRC interpolator: %d coeffs.\n", ncoeffs);
if ( cfg.debug ) filtergen::dump_filter("rrc", ncoeffs, coeffs);
interpolator = new fir_interpolator<float,float>
(ncoeffs, coeffs, cfg.interp_ss);
break;
}
default:
fatal("Interpolator not implemented");
}
cstln_receiver<f32> demod(&sch, interpolator,
*p_preprocessed, p_symbols,
&p_freq, &p_ss, &p_mer, &p_sampled);
if ( cfg.standard == config::DVB_S ) {
if ( cfg.constellation != cstln_lut<256>::QPSK &&
@ -402,11 +416,6 @@ int run(config &cfg) {
r_resample->freq_tol = cfg.Fm/(cfg.Fs*decim) * 0.1;
}
if ( r_rrc ) {
r_rrc->freq_tap = &demod.freq_tap;
r_rrc->freq_tol = cfg.Fm/cfg.Fs * 0.1;
}
if ( r_cnr ) {
r_cnr->freq_tap = &demod.freq_tap;
r_cnr->tap_multiplier = 1.0 / decim;
@ -571,13 +580,21 @@ int run(config &cfg) {
}
#endif // GUI
if ( cfg.debug )
fprintf(stderr,
"Output:\n"
" '_': packet received without errors\n"
" '.': error-corrected packet\n"
" '!': packet with remaining errors\n");
if ( cfg.debug ) {
if ( ! cfg.hdlc )
fprintf(stderr,
"Output:\n"
" '_': packet received without errors\n"
" '.': error-corrected packet\n"
" '!': packet with remaining errors\n");
else
fprintf(stderr,
"Output:\n"
" '_': frame with correct checksum\n"
" '!': frame with invalid checksum\n"
" '^': framing error\n");
}
sch.run();
sch.shutdown();
@ -851,7 +868,6 @@ void usage(const char *name, FILE *f, int c) {
" --resample Resample baseband (CPU-intensive)\n"
" --resample-rej K Aliasing rejection (default: 10)\n"
" --decim N Decimate baseband (causes aliasing)\n"
" --roll-off A Roll-off (default: 0.35)\n"
" --cnr Measure CNR (requires samplerate>3*symbolrate)\n"
" --fd-pp NUM Dump preprocessed IQ data to file descriptor\n"
);
@ -864,6 +880,10 @@ void usage(const char *name, FILE *f, int c) {
" --const C QPSK (default), BPSK .. 32APSK (DVB-S2 only)\n"
" --cr N/D Code rate 1/2 (default) .. 7/8 .. 9/10\n"
" --fastlock Synchronize more aggressively (CPU-intensive)\n"
" --interp linear, rrc\n"
" --interp-ss N Sub-sampling steps\n"
" --interp-rej K RRC filter rejection (defaut:10)\n"
" --roll-off A RRC roll-off (default: 0.35)\n"
" --viterbi Use Viterbi (CPU-intensive)\n"
" --hard-metric Use Hamming distances with Viterbi\n"
);
@ -967,15 +987,23 @@ int main(int argc, const char *argv[]) {
cfg.resample_rej = atof(argv[++i]);
else if ( ! strcmp(argv[i], "--decim") && i+1<argc )
cfg.decim = atoi(argv[++i]);
else if ( ! strcmp(argv[i], "--rrc") )
cfg.rrc = true;
else if ( ! strcmp(argv[i], "--interp") && i+1<argc ) {
++i;
if (!strcmp(argv[i],"nearest")) cfg.interp = config::INTERP_NEAREST;
else if (!strcmp(argv[i],"linear" )) cfg.interp = config::INTERP_LINEAR;
else if (!strcmp(argv[i],"rrc" )) cfg.interp = config::INTERP_RRC;
else usage(argv[0], stderr, 1);
}
else if ( ! strcmp(argv[i], "--interp-ss") && i+1<argc )
cfg.interp_ss = atoi(argv[++i]);
else if ( ! strcmp(argv[i], "--rrc-rej") && i+1<argc )
cfg.rrc_rej = atof(argv[++i]);
else if ( ! strcmp(argv[i], "--roll-off") && i+1<argc )
cfg.rolloff = atof(argv[++i]);
else if ( ! strcmp(argv[i], "--hq") ) {
cfg.fastlock = true;
cfg.viterbi = true;
cfg.resample = true;
cfg.rrc = true;
cfg.interp = config::INTERP_RRC;
}
else if ( ! strcmp(argv[i], "--hs") )
cfg.highspeed = true;