// Helper function to keep code base small
void symsync_crcf_bench(struct rusage * _start,
struct rusage * _finish,
unsigned long int * _num_iterations,
unsigned int _k,
unsigned int _m)
{
unsigned long int i;
unsigned int npfb = 16; // number of filters in bank
unsigned int k = _k; // samples/symbol
unsigned int m = _m; // filter delay [symbols]
float beta = 0.3f; // filter excess bandwidth factor
// create symbol synchronizer
symsync_crcf q = symsync_crcf_create_rnyquist(LIQUID_RNYQUIST_RRC,
k, m, beta, npfb);
//
unsigned int num_samples = 64;
*_num_iterations /= num_samples;
unsigned int num_written;
float complex x[num_samples];
float complex y[num_samples];
// generate pseudo-random data
msequence ms = msequence_create_default(6);
for (i=0; i<num_samples; i++)
x[i] = ((float)msequence_generate_symbol(ms, 6) - 31.5) / 24.0f;
msequence_destroy(ms);
// start trials
getrusage(RUSAGE_SELF, _start);
for (i=0; i<(*_num_iterations); i++) {
symsync_crcf_execute(q, x, num_samples, y, &num_written);
symsync_crcf_execute(q, x, num_samples, y, &num_written);
symsync_crcf_execute(q, x, num_samples, y, &num_written);
symsync_crcf_execute(q, x, num_samples, y, &num_written);
}
getrusage(RUSAGE_SELF, _finish);
*_num_iterations *= 4 * num_samples;
symsync_crcf_destroy(q);
}
int main(int argc, char*argv[]) {
srand(time(NULL));
// options
unsigned int k = 2; // samples/symbol (input)
unsigned int k_out = 2; // samples/symbol (output)
unsigned int m = 5; // filter delay (symbols)
float beta = 0.5f; // filter excess bandwidth factor
unsigned int num_filters = 32; // number of filters in the bank
unsigned int num_symbols = 400; // number of data symbols
float SNRdB = 30.0f; // signal-to-noise ratio
// transmit/receive filter types
liquid_firfilt_type ftype_tx = LIQUID_FIRFILT_RRC;
liquid_firfilt_type ftype_rx = LIQUID_FIRFILT_RRC;
float bt = 0.02f; // loop filter bandwidth
float tau = -0.2f; // fractional symbol offset
float r = 1.00f; // resampled rate
// use random data or 101010 phasing pattern
int random_data=1;
int dopt;
while ((dopt = getopt(argc,argv,"hT:k:K:m:b:B:s:w:n:t:r:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'T':
if (strcmp(optarg,"gmsk")==0) {
ftype_tx = LIQUID_FIRFILT_GMSKTX;
ftype_rx = LIQUID_FIRFILT_GMSKRX;
} else {
ftype_tx = liquid_getopt_str2firfilt(optarg);
ftype_rx = liquid_getopt_str2firfilt(optarg);
}
if (ftype_tx == LIQUID_FIRFILT_UNKNOWN) {
fprintf(stderr,"error: %s, unknown filter type '%s'\n", argv[0], optarg);
exit(1);
}
break;
case 'k': k = atoi(optarg); break;
case 'K': k_out = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 'b': beta = atof(optarg); break;
case 'B': num_filters = atoi(optarg); break;
case 's': SNRdB = atof(optarg); break;
case 'w': bt = atof(optarg); break;
case 'n': num_symbols = atoi(optarg); break;
case 't': tau = atof(optarg); break;
case 'r': r = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if (k < 2) {
fprintf(stderr,"error: k (samples/symbol) must be at least 2\n");
exit(1);
} else if (m < 1) {
fprintf(stderr,"error: m (filter delay) must be greater than 0\n");
exit(1);
} else if (beta <= 0.0f || beta > 1.0f) {
fprintf(stderr,"error: beta (excess bandwidth factor) must be in (0,1]\n");
exit(1);
} else if (num_filters == 0) {
fprintf(stderr,"error: number of polyphase filters must be greater than 0\n");
exit(1);
} else if (bt <= 0.0f) {
fprintf(stderr,"error: timing PLL bandwidth must be greater than 0\n");
exit(1);
} else if (num_symbols == 0) {
fprintf(stderr,"error: number of symbols must be greater than 0\n");
exit(1);
} else if (tau < -1.0f || tau > 1.0f) {
fprintf(stderr,"error: timing phase offset must be in [-1,1]\n");
exit(1);
} else if (r < 0.5f || r > 2.0f) {
fprintf(stderr,"error: timing frequency offset must be in [0.5,2]\n");
exit(1);
}
// compute delay
while (tau < 0) tau += 1.0f; // ensure positive tau
float g = k*tau; // number of samples offset
int ds=floorf(g); // additional symbol delay
float dt = (g - (float)ds); // fractional sample offset
if (dt > 0.5f) { // force dt to be in [0.5,0.5]
dt -= 1.0f;
ds++;
}
unsigned int i, n=0;
unsigned int num_samples = k*num_symbols;
unsigned int num_samples_resamp = (unsigned int) ceilf(num_samples*r*1.1f) + 4;
float complex s[num_symbols]; // data symbols
float complex x[num_samples]; // interpolated samples
float complex y[num_samples_resamp]; // resampled data (resamp_crcf)
float complex z[k_out*num_symbols + 64];// synchronized samples
float complex sym_out[num_symbols + 64];// synchronized symbols
for (i=0; i<num_symbols; i++) {
if (random_data) {
// random signal (QPSK)
s[i] = cexpf(_Complex_I*0.5f*M_PI*((rand() % 4) + 0.5f));
} else {
s[i] = (i%2) ? 1.0f : -1.0f; // 101010 phasing pattern
}
}
//
// create and run interpolator
//
// design interpolating filter
unsigned int h_len = 2*k*m+1;
float h[h_len];
liquid_firdes_rnyquist(ftype_tx,k,m,beta,dt,h);
firinterp_crcf q = firinterp_crcf_create(k,h,h_len);
for (i=0; i<num_symbols; i++) {
firinterp_crcf_execute(q, s[i], &x[n]);
n+=k;
}
assert(n == num_samples);
firinterp_crcf_destroy(q);
//
// run resampler
//
unsigned int resamp_len = 10*k; // resampling filter semi-length (filter delay)
float resamp_bw = 0.45f; // resampling filter bandwidth
float resamp_As = 60.0f; // resampling filter stop-band attenuation
unsigned int resamp_npfb = 64; // number of filters in bank
resamp_crcf f = resamp_crcf_create(r, resamp_len, resamp_bw, resamp_As, resamp_npfb);
unsigned int num_samples_resampled = 0;
unsigned int num_written;
for (i=0; i<num_samples; i++) {
#if 0
// bypass arbitrary resampler
y[i] = x[i];
num_samples_resampled = num_samples;
#else
// TODO : compensate for resampler filter delay
resamp_crcf_execute(f, x[i], &y[num_samples_resampled], &num_written);
num_samples_resampled += num_written;
#endif
}
resamp_crcf_destroy(f);
//
// add noise
//
float nstd = powf(10.0f, -SNRdB/20.0f);
for (i=0; i<num_samples_resampled; i++)
y[i] += nstd*(randnf() + _Complex_I*randnf());
//
// create and run symbol synchronizer
//
symsync_crcf d = symsync_crcf_create_rnyquist(ftype_rx, k, m, beta, num_filters);
symsync_crcf_set_lf_bw(d,bt);
symsync_crcf_set_output_rate(d,k_out);
unsigned int num_samples_sync=0;
unsigned int nn;
unsigned int num_symbols_sync = 0;
float tau_hat[num_samples];
for (i=ds; i<num_samples_resampled; i++) {
tau_hat[num_samples_sync] = symsync_crcf_get_tau(d);
symsync_crcf_execute(d, &y[i], 1, &z[num_samples_sync], &nn);
// decimate
unsigned int j;
for (j=0; j<nn; j++) {
if ( (num_samples_sync%k_out)==0 )
sym_out[num_symbols_sync++] = z[num_samples_sync];
num_samples_sync++;
}
}
symsync_crcf_destroy(d);
// print last several symbols to screen
printf("output symbols:\n");
printf(" ...\n");
for (i=num_symbols_sync-10; i<num_symbols_sync; i++)
printf(" sym_out(%2u) = %8.4f + j*%8.4f;\n", i+1, crealf(sym_out[i]), cimagf(sym_out[i]));
//
// export output file
//
FILE* fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s, auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"close all;\nclear all;\n\n");
fprintf(fid,"k=%u;\n",k);
fprintf(fid,"m=%u;\n",m);
fprintf(fid,"beta=%12.8f;\n",beta);
fprintf(fid,"k_out=%u;\n",k_out);
fprintf(fid,"num_filters=%u;\n",num_filters);
fprintf(fid,"num_symbols=%u;\n",num_symbols);
for (i=0; i<h_len; i++)
fprintf(fid,"h(%3u) = %12.5f;\n", i+1, h[i]);
for (i=0; i<num_symbols; i++)
fprintf(fid,"s(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(s[i]), cimagf(s[i]));
for (i=0; i<num_samples; i++)
fprintf(fid,"x(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(x[i]), cimagf(x[i]));
for (i=0; i<num_samples_resampled; i++)
fprintf(fid,"y(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(y[i]), cimagf(y[i]));
for (i=0; i<num_samples_sync; i++)
fprintf(fid,"z(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(z[i]), cimagf(z[i]));
for (i=0; i<num_symbols_sync; i++)
fprintf(fid,"sym_out(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(sym_out[i]), cimagf(sym_out[i]));
for (i=0; i<num_samples_sync; i++)
fprintf(fid,"tau_hat(%3u) = %12.8f;\n", i+1, tau_hat[i]);
fprintf(fid,"\n\n");
fprintf(fid,"%% scale QPSK in-phase by sqrt(2)\n");
fprintf(fid,"z = z*sqrt(2);\n");
fprintf(fid,"\n\n");
fprintf(fid,"tz = [0:length(z)-1]/k_out;\n");
fprintf(fid,"iz = 1:k_out:length(z);\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(tz, real(z), '-',...\n");
fprintf(fid," tz(iz), real(z(iz)),'or');\n");
fprintf(fid,"xlabel('Time');\n");
fprintf(fid,"ylabel('Output Signal (real)');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"legend('output time series','optimum timing','location','northeast');\n");
fprintf(fid,"iz0 = iz( 1:round(length(iz)*0.5) );\n");
fprintf(fid,"iz1 = iz( round(length(iz)*0.5):length(iz) );\n");
fprintf(fid,"figure;\n");
fprintf(fid,"hold on;\n");
fprintf(fid,"plot(real(z(iz0)),imag(z(iz0)),'x','MarkerSize',4,'Color',[0.6 0.6 0.6]);\n");
fprintf(fid,"plot(real(z(iz1)),imag(z(iz1)),'o','MarkerSize',4,'Color',[0 0.25 0.5]);\n");
fprintf(fid,"hold off;\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"axis([-1 1 -1 1]*2.0);\n");
fprintf(fid,"xlabel('In-phase');\n");
fprintf(fid,"ylabel('Quadrature');\n");
fprintf(fid,"legend(['first 50%%'],['last 50%%'],'location','northeast');\n");
fprintf(fid,"figure;\n");
fprintf(fid,"tt = 0:(length(tau_hat)-1);\n");
fprintf(fid,"b = floor(num_filters*tau_hat + 0.5);\n");
fprintf(fid,"stairs(tt,tau_hat*num_filters);\n");
fprintf(fid,"hold on;\n");
fprintf(fid,"plot(tt,b,'-k','Color',[0 0 0]);\n");
fprintf(fid,"hold off;\n");
fprintf(fid,"xlabel('time');\n");
fprintf(fid,"ylabel('filterbank index');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"axis([0 length(tau_hat) -1 num_filters]);\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
// clean it up
printf("done.\n");
return 0;
}
int main(int argc, char*argv[]) {
srand(time(NULL));
// options
unsigned int k=2; // samples/symbol (input)
unsigned int m=3; // filter delay (symbols)
float beta=0.5f; // filter excess bandwidth factor
unsigned int npfb=32; // number of filters in the bank
unsigned int p=3; // equalizer length (symbols, hp_len = 2*k*p+1)
float mu = 0.05f; // equalizer learning rate
unsigned int num_symbols=500; // number of data symbols
unsigned int hc_len=5; // channel filter length
float SNRdB = 30.0f; // signal-to-noise ratio
liquid_firfilt_type ftype = LIQUID_FIRFILT_ARKAISER;
float bt=0.05f; // symbol synchronizer loop filter bandwidth
float tau=-0.1f; // fractional symbol offset
int dopt;
while ((dopt = getopt(argc,argv,"uhk:m:b:n:B:w:p:W:s:c:t:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
// transmit filter properties
case 'k': k = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 'b': beta = atof(optarg); break;
case 'n': num_symbols = atoi(optarg); break;
// symsync properties
case 'B': npfb = atoi(optarg); break;
case 'w': bt = atof(optarg); break;
// equalizer properties
case 'p': p = atoi(optarg); break;
case 'W': mu = atof(optarg); break;
// equalizer properties
case 's': SNRdB = atof(optarg); break;
case 'c': hc_len = atoi(optarg); break;
case 't': tau = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if (k < 2) {
fprintf(stderr,"error: %s,k (samples/symbol) must be at least 2\n", argv[0]);
exit(1);
} else if (m < 1) {
fprintf(stderr,"error: %s,m (filter delay) must be greater than 0\n", argv[0]);
exit(1);
} else if (beta <= 0.0f || beta > 1.0f) {
fprintf(stderr,"error: %s,beta (excess bandwidth factor) must be in (0,1]\n", argv[0]);
exit(1);
} else if (num_symbols == 0) {
fprintf(stderr,"error: %s,number of symbols must be greater than 0\n", argv[0]);
exit(1);
} else if (npfb == 0) {
fprintf(stderr,"error: %s,number of polyphase filters must be greater than 0\n", argv[0]);
exit(1);
} else if (bt < 0.0f) {
fprintf(stderr,"error: %s,timing PLL bandwidth cannot be negative\n", argv[0]);
exit(1);
} else if (p == 0) {
fprintf(stderr,"error: %s, equalizer order must be at least 1\n", argv[0]);
exit(1);
} else if (mu < 0.0f || mu > 1.0f) {
fprintf(stderr,"error: %s, equalizer learning rate must be in [0,1]\n", argv[0]);
exit(1);
} else if (hc_len < 1) {
fprintf(stderr,"error: %s, channel response must have at least 1 tap\n", argv[0]);
exit(1);
} else if (tau < -1.0f || tau > 1.0f) {
fprintf(stderr,"error: %s,timing phase offset must be in [-1,1]\n", argv[0]);
exit(1);
}
// derived values
unsigned int ht_len = 2*k*m+1; // transmit filter order
unsigned int hp_len = 2*k*p+1; // equalizer order
float nstd = powf(10.0f, -SNRdB/20.0f);
float dt = tau; // fractional sample offset
unsigned int ds = 0; // full sample delay
unsigned int i;
unsigned int num_samples = k*num_symbols;
float complex s[num_symbols]; // data symbols
float complex x[num_samples]; // interpolated samples
float complex y[num_samples]; // channel output
float complex z[k*num_symbols + 64]; // synchronized samples
float complex sym_out[num_symbols + 64]; // synchronized symbols
for (i=0; i<num_symbols; i++) {
s[i] = (rand() % 2 ? M_SQRT1_2 : -M_SQRT1_2) +
(rand() % 2 ? M_SQRT1_2 : -M_SQRT1_2) * _Complex_I;
}
//
// create and run interpolator
//
// design interpolating filter
float ht[ht_len];
liquid_firdes_prototype(ftype,k,m,beta,dt,ht);
firinterp_crcf q = firinterp_crcf_create(k, ht, ht_len);
for (i=0; i<num_symbols; i++)
firinterp_crcf_execute(q, s[i], &x[i*k]);
firinterp_crcf_destroy(q);
//
// channel
//
// generate channel impulse response, filter
float complex hc[hc_len];
hc[0] = 1.0f;
for (i=1; i<hc_len; i++)
hc[i] = 0.07f*(randnf() + randnf()*_Complex_I);
firfilt_cccf fchannel = firfilt_cccf_create(hc, hc_len);
// push through channel
for (i=0; i<num_samples; i++) {
firfilt_cccf_push(fchannel, x[i]);
firfilt_cccf_execute(fchannel, &y[i]);
// add noise
y[i] += nstd*(randnf() + randnf()*_Complex_I)*M_SQRT1_2;
}
firfilt_cccf_destroy(fchannel);
//
// symbol timing recovery
//
// create symbol synchronizer
symsync_crcf d = symsync_crcf_create_rnyquist(ftype, k, m, beta, npfb);
symsync_crcf_set_lf_bw(d,bt);
symsync_crcf_set_output_rate(d,k);
unsigned int num_samples_sync=0;
unsigned int nw;
for (i=ds; i<num_samples; i++) {
// push through symbol synchronizer
symsync_crcf_execute(d, &y[i], 1, &z[num_samples_sync], &nw);
num_samples_sync += nw;
}
printf("num samples : %6u (%6u synchronized)\n", num_samples, num_samples_sync);
symsync_crcf_destroy(d);
//
// equalizer/decimator
//
// create equalizer as low-pass filter
float complex hp[hp_len];
eqlms_cccf eq = eqlms_cccf_create_lowpass(hp_len, 0.4f);
eqlms_cccf_set_bw(eq, mu);
// push through equalizer and decimate
unsigned int num_symbols_sync = 0;
float complex d_hat = 0.0f;
for (i=0; i<num_samples_sync; i++) {
// push sample into equalizer
eqlms_cccf_push(eq, z[i]);
// decimate by k
if ( (i%k) != 0) continue;
// compute output
eqlms_cccf_execute(eq, &d_hat);
sym_out[num_symbols_sync++] = d_hat;
// check if buffer is full
if ( i < hp_len ) continue;
// estimate transmitted signal
float complex d_prime = (crealf(d_hat) > 0.0f ? M_SQRT1_2 : -M_SQRT1_2) +
(cimagf(d_hat) > 0.0f ? M_SQRT1_2 : -M_SQRT1_2) * _Complex_I;
// update equalizer
eqlms_cccf_step(eq, d_prime, d_hat);
}
// get equalizer weights
eqlms_cccf_get_weights(eq, hp);
// destroy equalizer object
eqlms_cccf_destroy(eq);
// print last several symbols to screen
printf("output symbols:\n");
for (i=num_symbols_sync-10; i<num_symbols_sync; i++)
printf(" sym_out(%2u) = %8.4f + j*%8.4f;\n", i+1, crealf(sym_out[i]), cimagf(sym_out[i]));
//
// export output file
//
FILE* fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s, auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"close all;\nclear all;\n\n");
fprintf(fid,"k=%u;\n",k);
fprintf(fid,"m=%u;\n",m);
fprintf(fid,"beta=%12.8f;\n",beta);
fprintf(fid,"npfb=%u;\n",npfb);
fprintf(fid,"num_symbols=%u;\n",num_symbols);
for (i=0; i<ht_len; i++)
fprintf(fid,"ht(%3u) = %12.5f;\n", i+1, ht[i]);
for (i=0; i<hc_len; i++)
fprintf(fid,"hc(%3u) = %12.5f + j*%12.8f;\n", i+1, crealf(hc[i]), cimagf(hc[i]));
for (i=0; i<hp_len; i++)
fprintf(fid,"hp(%3u) = %12.5f + j*%12.8f;\n", i+1, crealf(hp[i]), cimagf(hp[i]));
for (i=0; i<num_symbols; i++)
fprintf(fid,"s(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(s[i]), cimagf(s[i]));
for (i=0; i<num_samples; i++)
fprintf(fid,"x(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(x[i]), cimagf(x[i]));
for (i=0; i<num_samples; i++)
fprintf(fid,"y(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(y[i]), cimagf(y[i]));
for (i=0; i<num_samples_sync; i++)
fprintf(fid,"z(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(z[i]), cimagf(z[i]));
for (i=0; i<num_symbols_sync; i++)
fprintf(fid,"sym_out(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(sym_out[i]), cimagf(sym_out[i]));
#if 0
fprintf(fid,"\n\n");
fprintf(fid,"%% scale QPSK in-phase by sqrt(2)\n");
fprintf(fid,"z = z*sqrt(2);\n");
fprintf(fid,"\n\n");
fprintf(fid,"tz = [0:length(z)-1]/k;\n");
fprintf(fid,"iz = 1:k:length(z);\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(tz, real(z), '-',...\n");
fprintf(fid," tz(iz), real(z(iz)),'or');\n");
fprintf(fid,"xlabel('Time');\n");
fprintf(fid,"ylabel('Output Signal (real)');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"legend('output time series','optimim timing',1);\n");
#endif
// compute composite response
fprintf(fid,"hd = real(conv(ht/k,conv(hc,hp)));\n");
// plot frequency response
fprintf(fid,"nfft = 1024;\n");
fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"Ht = 20*log10(abs(fftshift(fft(ht/k,nfft))));\n");
fprintf(fid,"Hc = 20*log10(abs(fftshift(fft(hc, nfft))));\n");
fprintf(fid,"Hp = 20*log10(abs(fftshift(fft(hp, nfft))));\n");
fprintf(fid,"Hd = 20*log10(abs(fftshift(fft(hd, nfft))));\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(f,Ht, f,Hc, f,Hp, f,Hd,'-k','LineWidth',2);\n");
fprintf(fid,"axis([-0.5 0.5 -20 10]);\n");
fprintf(fid,"axis([-0.5 0.5 -6 6 ]);\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"legend('transmit','channel','equalizer','composite','location','northeast');\n");
fprintf(fid,"i0 = [1:round(length(sym_out)/2)];\n");
fprintf(fid,"i1 = [round(length(sym_out)/2):length(sym_out)];\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(real(sym_out(i0)),imag(sym_out(i0)),'x','MarkerSize',4,'Color',[0.60 0.60 0.60],...\n");
fprintf(fid," real(sym_out(i1)),imag(sym_out(i1)),'x','MarkerSize',4,'Color',[0.00 0.25 0.50]);\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"axis([-1 1 -1 1]*1.2);\n");
fprintf(fid,"xlabel('In-phase');\n");
fprintf(fid,"ylabel('Quadrature');\n");
fprintf(fid,"legend(['first 50%%'],['last 50%%'],'location','northeast');\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
// clean it up
printf("done.\n");
return 0;
}
int main(int argc, char*argv[])
{
srand(time(NULL));
// options
unsigned int k = 2; // samples/symbol (input)
unsigned int m = 3; // filter delay (symbols)
float beta = 0.5f; // filter excess bandwidth factor
unsigned int num_filters = 32; // number of filters in the bank
float SNRdB = 30.0f; // signal-to-noise ratio
float bt = 0.02f; // loop filter bandwidth
unsigned int num_symbols = 400; // number of data symbols
float tau = -0.20f; // fractional symbol offset
// Nyquist filter type
liquid_firfilt_type ftype = LIQUID_FIRFILT_KAISER;
int dopt;
while ((dopt = getopt(argc,argv,"uhk:m:b:B:s:w:n:t:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'k': k = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 'b': beta = atof(optarg); break;
case 'B': num_filters = atoi(optarg); break;
case 's': SNRdB = atof(optarg); break;
case 'w': bt = atof(optarg); break;
case 'n': num_symbols = atoi(optarg); break;
case 't': tau = atof(optarg); break;
default:
exit(1);
}
}
unsigned int i;
// validate input
if (k < 2) {
fprintf(stderr,"error: k (samples/symbol) must be at least 2\n");
exit(1);
} else if (m < 1) {
fprintf(stderr,"error: m (filter delay) must be greater than 0\n");
exit(1);
} else if (beta <= 0.0f || beta > 1.0f) {
fprintf(stderr,"error: beta (excess bandwidth factor) must be in (0,1]\n");
exit(1);
} else if (num_filters == 0) {
fprintf(stderr,"error: number of polyphase filters must be greater than 0\n");
exit(1);
} else if (bt <= 0.0f) {
fprintf(stderr,"error: timing PLL bandwidth must be greater than 0\n");
exit(1);
} else if (num_symbols == 0) {
fprintf(stderr,"error: number of symbols must be greater than 0\n");
exit(1);
} else if (tau < -1.0f || tau > 1.0f) {
fprintf(stderr,"error: timing phase offset must be in [-1,1]\n");
exit(1);
}
// derived values
unsigned int num_samples = k*num_symbols;
float complex x[num_samples]; // interpolated samples
float complex y[num_samples]; // received signal (with noise)
float tau_hat[num_samples]; // instantaneous timing offset estimate
float complex sym_out[num_symbols + 64];// synchronized symbols
// create sequence of Nyquist-interpolated QPSK symbols
firinterp_crcf interp = firinterp_crcf_create_nyquist(ftype,k,m,beta,tau);
for (i=0; i<num_symbols; i++) {
// generate random QPSK symbol
float complex s = ( rand() % 2 ? M_SQRT1_2 : -M_SQRT1_2 ) +
( rand() % 2 ? M_SQRT1_2 : -M_SQRT1_2 ) * _Complex_I;
// interpolate symbol
firinterp_crcf_execute(interp, s, &x[i*k]);
}
firinterp_crcf_destroy(interp);
// add noise
float nstd = powf(10.0f, -SNRdB/20.0f);
for (i=0; i<num_samples; i++)
y[i] = x[i] + nstd*(randnf() + _Complex_I*randnf());
// create and run symbol synchronizer
symsync_crcf decim = symsync_crcf_create_kaiser(k, m, beta, num_filters);
symsync_crcf_set_lf_bw(decim,bt); // set loop filter bandwidth
// NOTE: we could just synchronize entire block (see following line);
// however we would like to save the instantaneous timing offset
// estimate for plotting purposes
//symsync_crcf_execute(d, y, num_samples, sym_out, &num_symbols_sync);
unsigned int num_symbols_sync = 0;
unsigned int num_written=0;
for (i=0; i<num_samples; i++) {
// save instantaneous timing offset estimate
tau_hat[i] = symsync_crcf_get_tau(decim);
// execute one sample at a time
symsync_crcf_execute(decim, &y[i], 1, &sym_out[num_symbols_sync], &num_written);
// increment number of symbols synchronized
num_symbols_sync += num_written;
}
symsync_crcf_destroy(decim);
// print last several symbols to screen
printf("output symbols:\n");
for (i=num_symbols_sync-10; i<num_symbols_sync; i++)
printf(" sym_out(%2u) = %8.4f + j*%8.4f;\n", i+1, crealf(sym_out[i]), cimagf(sym_out[i]));
//
// export output file
//
FILE* fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s, auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"close all;\nclear all;\n\n");
fprintf(fid,"k=%u;\n",k);
fprintf(fid,"m=%u;\n",m);
fprintf(fid,"beta=%12.8f;\n",beta);
fprintf(fid,"num_filters=%u;\n",num_filters);
fprintf(fid,"num_symbols=%u;\n",num_symbols);
for (i=0; i<num_samples; i++)
fprintf(fid,"x(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(x[i]), cimagf(x[i]));
for (i=0; i<num_samples; i++)
fprintf(fid,"y(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(y[i]), cimagf(y[i]));
for (i=0; i<num_samples; i++)
fprintf(fid,"tau_hat(%3u) = %12.8f;\n", i+1, tau_hat[i]);
for (i=0; i<num_symbols_sync; i++)
fprintf(fid,"sym_out(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(sym_out[i]), cimagf(sym_out[i]));
fprintf(fid,"i0 = 1:round( 0.5*num_symbols );\n");
fprintf(fid,"i1 = round( 0.5*num_symbols ):num_symbols;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"hold on;\n");
fprintf(fid,"plot(real(sym_out(i0)),imag(sym_out(i0)),'x','MarkerSize',4,'Color',[0.6 0.6 0.6]);\n");
fprintf(fid,"plot(real(sym_out(i1)),imag(sym_out(i1)),'o','MarkerSize',4,'Color',[0 0.25 0.5]);\n");
fprintf(fid,"hold off;\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"axis([-1 1 -1 1]*1.6);\n");
fprintf(fid,"xlabel('In-phase');\n");
fprintf(fid,"ylabel('Quadrature');\n");
fprintf(fid,"legend(['first 50%%'],['last 50%%'],1);\n");
fprintf(fid,"figure;\n");
fprintf(fid,"tt = 0:(length(tau_hat)-1);\n");
fprintf(fid,"b = floor(num_filters*tau_hat + 0.5);\n");
fprintf(fid,"stairs(tt,tau_hat*num_filters);\n");
fprintf(fid,"hold on;\n");
fprintf(fid,"plot(tt,b,'-k','Color',[0 0 0]);\n");
fprintf(fid,"hold off;\n");
fprintf(fid,"xlabel('time');\n");
fprintf(fid,"ylabel('filterbank index');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"axis([0 length(tau_hat) -1 num_filters]);\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
// clean it up
printf("done.\n");
return 0;
}
int main(int argc, char*argv[]) {
srand(time(NULL));
// options
unsigned int k=2; // samples/symbol (input)
unsigned int k_out=2; // samples/symbol (output)
unsigned int m=4; // filter delay (symbols)
float beta=0.3f; // filter excess bandwidth factor
unsigned int num_filters=64; // number of filters in the bank
unsigned int num_symbols=500; // number of data symbols
float SNRdB = 30.0f; // signal-to-noise ratio
liquid_rnyquist_type ftype_tx = LIQUID_RNYQUIST_RRC;
liquid_rnyquist_type ftype_rx = LIQUID_RNYQUIST_RRC;
float bt=0.01f; // loop filter bandwidth
float tau=-0.4f; // fractional symbol offset
float r = 1.00f; // resampled rate
char filename_base[256] = "figures.gen/filter_symsync_crcf";
int dopt;
while ((dopt = getopt(argc,argv,"hf:k:K:m:b:B:s:w:n:t:r:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'f': strncpy(filename_base,optarg,256); break;
case 'k': k = atoi(optarg); break;
case 'K': k_out = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 'b': beta = atof(optarg); break;
case 'B': num_filters = atoi(optarg); break;
case 's': SNRdB = atof(optarg); break;
case 'w': bt = atof(optarg); break;
case 'n': num_symbols = atoi(optarg); break;
case 't': tau = atof(optarg); break;
case 'r': r = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if (k < 2) {
fprintf(stderr,"error: k (samples/symbol) must be at least 2\n");
exit(1);
} else if (m < 1) {
fprintf(stderr,"error: m (filter delay) must be greater than 0\n");
exit(1);
} else if (beta <= 0.0f || beta > 1.0f) {
fprintf(stderr,"error: beta (excess bandwidth factor) must be in (0,1]\n");
exit(1);
} else if (num_filters == 0) {
fprintf(stderr,"error: number of polyphase filters must be greater than 0\n");
exit(1);
} else if (bt <= 0.0f) {
fprintf(stderr,"error: timing PLL bandwidth must be greater than 0\n");
exit(1);
} else if (num_symbols == 0) {
fprintf(stderr,"error: number of symbols must be greater than 0\n");
exit(1);
} else if (tau < -1.0f || tau > 1.0f) {
fprintf(stderr,"error: timing phase offset must be in [-1,1]\n");
exit(1);
} else if (r < 0.5f || r > 2.0f) {
fprintf(stderr,"error: timing frequency offset must be in [0.5,2]\n");
exit(1);
}
// compute delay
while (tau < 0) tau += 1.0f; // ensure positive tau
float g = k*tau; // number of samples offset
int ds=floorf(g); // additional symbol delay
float dt = (g - (float)ds); // fractional sample offset
if (dt > 0.5f) { // force dt to be in [0.5,0.5]
dt -= 1.0f;
ds++;
}
unsigned int i, n=0;
// derived values
unsigned int num_samples = k*num_symbols;
unsigned int num_samples_resamp = (unsigned int) ceilf(num_samples*r*1.1f) + 4;
// arrays
float complex s[num_symbols]; // data symbols
float complex x[num_samples]; // interpolated samples
float complex y[num_samples_resamp]; // resampled data (resamp_crcf)
float complex z[k_out*num_symbols + 64];// synchronized samples
float complex sym_out[num_symbols + 64];// synchronized symbols
// random signal (QPSK)
for (i=0; i<num_symbols; i++) {
s[i] = ( rand() % 2 ? M_SQRT1_2 : -M_SQRT1_2 ) +
( rand() % 2 ? M_SQRT1_2 : -M_SQRT1_2 ) * _Complex_I;
}
//
// create and run interpolator
//
// design interpolating filter
unsigned int h_len = 2*k*m+1;
float h[h_len];
liquid_firdes_rnyquist(ftype_tx,k,m,beta,dt,h);
interp_crcf q = interp_crcf_create(k,h,h_len);
for (i=0; i<num_symbols; i++) {
interp_crcf_execute(q, s[i], &x[n]);
n+=k;
}
assert(n == num_samples);
interp_crcf_destroy(q);
//
// run resampler
//
unsigned int resamp_len = 10*k; // resampling filter semi-length (filter delay)
float resamp_bw = 0.45f; // resampling filter bandwidth
float resamp_As = 60.0f; // resampling filter stop-band attenuation
unsigned int resamp_npfb = 64; // number of filters in bank
resamp_crcf f = resamp_crcf_create(r, resamp_len, resamp_bw, resamp_As, resamp_npfb);
unsigned int num_samples_resampled = 0;
unsigned int num_written;
for (i=0; i<num_samples; i++) {
#if 0
// bypass arbitrary resampler
y[i] = x[i];
num_samples_resampled = num_samples;
#else
// TODO : compensate for resampler filter delay
resamp_crcf_execute(f, x[i], &y[num_samples_resampled], &num_written);
num_samples_resampled += num_written;
#endif
}
resamp_crcf_destroy(f);
//
// add noise
//
float nstd = powf(10.0f, -SNRdB/20.0f);
for (i=0; i<num_samples_resampled; i++)
y[i] += nstd*(randnf() + _Complex_I*randnf());
//
// create and run symbol synchronizer
//
symsync_crcf d = symsync_crcf_create_rnyquist(ftype_rx, k, m, beta, num_filters);
symsync_crcf_set_lf_bw(d,bt);
symsync_crcf_set_output_rate(d,k_out);
unsigned int num_samples_sync=0;
unsigned int nn;
unsigned int num_symbols_sync = 0;
float tau_hat[num_samples];
for (i=ds; i<num_samples_resampled; i++) {
tau_hat[num_samples_sync] = symsync_crcf_get_tau(d);
symsync_crcf_execute(d, &y[i], 1, &z[num_samples_sync], &nn);
// decimate
unsigned int j;
for (j=0; j<nn; j++) {
if ( (num_samples_sync%k_out)==0 )
sym_out[num_symbols_sync++] = z[num_samples_sync];
num_samples_sync++;
}
}
symsync_crcf_destroy(d);
// print last several symbols to screen
printf("output symbols:\n");
for (i=num_symbols_sync-10; i<num_symbols_sync; i++)
printf(" sym_out(%2u) = %8.4f + j*%8.4f;\n", i+1, crealf(sym_out[i]), cimagf(sym_out[i]));
//
// export output
//
FILE * fid = NULL;
char filename[300];
//
// const: constellation
//
strncpy(filename, filename_base, 256);
strcat(filename, "_const.gnu");
fid = fopen(filename,"w");
if (!fid) {
fprintf(stderr,"error: %s, could not open file '%s' for writing\n", argv[0], filename);
return 1;
}
fprintf(fid,"# %s: auto-generated file\n\n", filename);
fprintf(fid,"reset\n");
fprintf(fid,"set terminal postscript eps enhanced color solid rounded\n");
fprintf(fid,"set size ratio 1\n");
fprintf(fid,"set xrange [-1.5:1.5];\n");
fprintf(fid,"set yrange [-1.5:1.5];\n");
fprintf(fid,"set xlabel 'In-phase'\n");
fprintf(fid,"set ylabel 'Quadrature phase'\n");
fprintf(fid,"set grid xtics ytics\n");
fprintf(fid,"set grid linetype 1 linecolor rgb '%s' linewidth 1\n",LIQUID_DOC_COLOR_GRID);
fprintf(fid,"plot '-' using 1:2 with points pointtype 7 pointsize 0.5 linecolor rgb '%s' title 'first %u symbols',\\\n", LIQUID_DOC_COLOR_GRAY, num_symbols/2);
fprintf(fid," '-' using 1:2 with points pointtype 7 pointsize 0.7 linecolor rgb '%s' title 'last %u symbols'\n", LIQUID_DOC_COLOR_RED, num_symbols/2);
// first half of symbols
for (i=2*m; i<num_symbols_sync/2; i++)
fprintf(fid," %12.4e %12.4e\n", crealf(sym_out[i]), cimagf(sym_out[i]));
fprintf(fid,"e\n");
// second half of symbols
for ( ; i<num_symbols_sync; i++)
fprintf(fid," %12.4e %12.4e\n", crealf(sym_out[i]), cimagf(sym_out[i]));
fprintf(fid,"e\n");
fclose(fid);
printf("results written to '%s'\n", filename);
//
// time series
//
strncpy(filename, filename_base, 256);
strcat(filename, "_time.gnu");
fid = fopen(filename,"w");
if (!fid) {
fprintf(stderr,"error: %s, could not open file '%s' for writing\n", argv[0], filename);
return 1;
}
fprintf(fid,"# %s: auto-generated file\n\n", filename);
fprintf(fid,"reset\n");
fprintf(fid,"set terminal postscript eps enhanced color solid rounded\n");
fprintf(fid,"set xrange [0:%u];\n",num_symbols);
fprintf(fid,"set yrange [-1.5:1.5]\n");
fprintf(fid,"set size ratio 0.3\n");
fprintf(fid,"set xlabel 'Symbol Index'\n");
fprintf(fid,"set key top right nobox\n");
//fprintf(fid,"set ytics -5,1,5\n");
fprintf(fid,"set grid xtics ytics\n");
fprintf(fid,"set pointsize 0.6\n");
fprintf(fid,"set grid linetype 1 linecolor rgb '%s' lw 1\n", LIQUID_DOC_COLOR_GRID);
fprintf(fid,"set multiplot layout 2,1 scale 1.0,1.0\n");
// real
fprintf(fid,"# real\n");
fprintf(fid,"set ylabel 'Real'\n");
fprintf(fid,"plot '-' using 1:2 with lines linetype 1 linewidth 1 linecolor rgb '#999999' notitle,\\\n");
fprintf(fid," '-' using 1:2 with points pointtype 7 linecolor rgb '%s' notitle'\n", LIQUID_DOC_COLOR_BLUE);
//
for (i=0; i<num_samples_sync; i++)
fprintf(fid,"%12.8f %12.4e\n", (float)i/(float)k_out, crealf(z[i]));
fprintf(fid,"e\n");
//
for (i=0; i<num_samples_sync; i+=k)
fprintf(fid,"%12.8f %12.4e\n", (float)i/(float)k_out, crealf(z[i]));
fprintf(fid,"e\n");
// imag
fprintf(fid,"# imag\n");
fprintf(fid,"set ylabel 'Imag'\n");
fprintf(fid,"plot '-' using 1:2 with lines linetype 1 linewidth 1 linecolor rgb '#999999' notitle,\\\n");
fprintf(fid," '-' using 1:2 with points pointtype 7 linecolor rgb '%s' notitle'\n", LIQUID_DOC_COLOR_GREEN);
//
for (i=0; i<num_samples_sync; i++)
fprintf(fid,"%12.8f %12.4e\n", (float)i/(float)k_out, cimagf(z[i]));
fprintf(fid,"e\n");
//
for (i=0; i<num_samples_sync; i+=k)
fprintf(fid,"%12.8f %12.4e\n", (float)i/(float)k_out, cimagf(z[i]));
fprintf(fid,"e\n");
fprintf(fid,"unset multiplot\n");
// close output file
fclose(fid);
printf("results written to '%s'\n", filename);
// clean it up
return 0;
}