int main(int argc, char*argv[])
{
srand( time(NULL) );
// options
float SNRdB = 20.0f; // signal-to-noise ratio
float noise_floor = -20.0f; // noise floor
float dphi = 0.01f; // carrier frequency offset
float theta = 0.0f; // carrier phase offset
float dt = -0.2f; // fractional sample timing offset
crc_scheme check = LIQUID_CRC_32; // data validity check
fec_scheme fec0 = LIQUID_FEC_NONE; // fec (inner)
fec_scheme fec1 = LIQUID_FEC_NONE; // fec (outer)
unsigned int payload_len = 200; // payload length
int debug_enabled = 0;
// get options
int dopt;
while((dopt = getopt(argc,argv,"hdS:F:P:T:")) != EOF){
switch (dopt) {
case 'h': usage(); return 0;
case 'd': debug_enabled = 1; break;
case 'S': SNRdB = atof(optarg); break;
case 'F': dphi = atof(optarg); break;
case 'P': theta = atof(optarg); break;
case 'T': dt = atof(optarg); break;
default:
exit(-1);
}
}
// derived values
float nstd = powf(10.0f, noise_floor/20.0f); // noise std. dev.
float gamma = powf(10.0f, (SNRdB+noise_floor)/20.0f); // channel gain
// create frame generator
fskframegen fg = fskframegen_create();
fskframegen_print(fg);
// create frame synchronizer using default properties
fskframesync fs = fskframesync_create(callback,NULL);
fskframesync_print(fs);
if (debug_enabled)
fskframesync_debug_enable(fs);
// data payload
unsigned int i;
// initialize header and payload data
for (i=0; i<8; i++)
header[i] = i;
for (i=0; i<200; i++)
payload[i] = rand() & 0xff;
// allocate memory for the frame samples
unsigned int buf_len = 64;
float complex buf_tx[buf_len]; // receive buffer
float complex buf_rx[buf_len]; // transmit buffer
// assemble the frame
fskframegen_assemble(fg, header, payload, payload_len, check, fec0, fec1);
// spectral periodogram
unsigned int nfft = 4200;
spgramcf periodogram = spgramcf_create_default(nfft);
// write frame in blocks
int frame_complete = 0;
while (!frame_complete)
{
frame_complete = fskframegen_write_samples(fg, buf_tx, buf_len);
// add noise, channel gain
for (i=0; i<buf_len; i++)
buf_rx[i] = buf_tx[i]*gamma + nstd*(randnf() + randnf()*_Complex_I)*M_SQRT1_2;
// synchronize/receive the frame
fskframesync_execute_block(fs, buf_rx, buf_len);
// estimate power spectral density
spgramcf_write(periodogram, buf_rx, buf_len);
}
// compute power spectral density of received signal
float psd[nfft];
spgramcf_get_psd(periodogram, psd);
// clean up allocated objects
spgramcf_destroy(periodogram);
fskframegen_destroy(fg);
fskframesync_destroy(fs);
//
// export results
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s : auto-generated file\n", OUTPUT_FILENAME);
fprintf(fid,"clear all\n");
fprintf(fid,"close all\n");
fprintf(fid,"nfft = %u;\n", nfft);
// save power spectral density
fprintf(fid,"psd = zeros(1,nfft);\n");
for (i=0; i<nfft; i++)
fprintf(fid,"psd(%4u) = %12.8f;\n", i+1, psd[i]);
// plot PSD
fprintf(fid,"figure('Color','white');\n");
fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"plot(f,psd,'LineWidth',1.5,'Color',[0.5 0 0]);\n");
fprintf(fid,"axis([-0.5 0.5 -30 30]);\n");
fprintf(fid,"xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid,"ylabel('PSD [dB]');\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("results written to '%s'\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
int main(int argc, char*argv[])
{
// options
int ftype = LIQUID_FIRFILT_ARKAISER;
int ms = LIQUID_MODEM_QPSK;
unsigned int k = 2; // samples per symbol
unsigned int m = 7; // filter delay (symbols)
float beta = 0.20f; // filter excess bandwidth factor
unsigned int num_symbols = 4000; // number of data symbols
unsigned int hc_len = 4; // channel filter length
float noise_floor = -60.0f; // noise floor [dB]
float SNRdB = 30.0f; // signal-to-noise ratio [dB]
float bandwidth = 0.02f; // loop filter bandwidth
float tau = -0.2f; // fractional symbol offset
float rate = 1.001f; // sample rate offset
float dphi = 0.01f; // carrier frequency offset [radians/sample]
float phi = 2.1f; // carrier phase offset [radians]
unsigned int nfft = 2400; // spectral periodogram FFT size
unsigned int num_samples = 200000; // number of samples
int dopt;
while ((dopt = getopt(argc,argv,"hk:m:b:s:w:n:t:r:")) != 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 's': SNRdB = atof(optarg); break;
case 'w': bandwidth = atof(optarg); break;
case 'n': num_symbols = atoi(optarg); break;
case 't': tau = atof(optarg); break;
case 'r': rate = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if (k < 2) {
fprintf(stderr,"error: k (samples/symbol) must be greater than 1\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 (bandwidth <= 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 (rate > 1.02f || rate < 0.98f) {
fprintf(stderr,"error: timing rate offset must be in [1.02,0.98]\n");
exit(1);
}
unsigned int i;
// buffers
unsigned int buf_len = 400; // buffer size
float complex x [buf_len]; // original signal
float complex y [buf_len*2]; // channel output (larger to accommodate resampler)
float complex syms[buf_len]; // recovered symbols
// window for saving last few symbols
windowcf sym_buf = windowcf_create(buf_len);
// create stream generator
symstreamcf gen = symstreamcf_create_linear(ftype,k,m,beta,ms);
// create channel emulator and add impairments
channel_cccf channel = channel_cccf_create();
channel_cccf_add_awgn (channel, noise_floor, SNRdB);
channel_cccf_add_carrier_offset(channel, dphi, phi);
channel_cccf_add_multipath (channel, NULL, hc_len);
channel_cccf_add_resamp (channel, 0.0f, rate);
// create symbol tracking synchronizer
symtrack_cccf symtrack = symtrack_cccf_create(ftype,k,m,beta,ms);
symtrack_cccf_set_bandwidth(symtrack,0.05f);
// create spectral periodogram for estimating spectrum
spgramcf periodogram = spgramcf_create_default(nfft);
unsigned int total_samples = 0;
unsigned int ny;
unsigned int total_symbols = 0;
while (total_samples < num_samples)
{
// write samples to buffer
symstreamcf_write_samples(gen, x, buf_len);
// apply channel
channel_cccf_execute(channel, x, buf_len, y, &ny);
// push resulting sample through periodogram
spgramcf_write(periodogram, y, ny);
// run resulting stream through synchronizer
unsigned int num_symbols_sync;
symtrack_cccf_execute_block(symtrack, y, ny, syms, &num_symbols_sync);
total_symbols += num_symbols_sync;
// write resulting symbols to window buffer for plotting
windowcf_write(sym_buf, syms, num_symbols_sync);
// accumulated samples
total_samples += buf_len;
}
printf("total samples: %u\n", total_samples);
printf("total symbols: %u\n", total_symbols);
// write accumulated power spectral density estimate
float psd[nfft];
spgramcf_get_psd(periodogram, psd);
//
// export output file
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s, auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n");
// read buffer and write last symbols to file
float complex * rc;
windowcf_read(sym_buf, &rc);
fprintf(fid,"syms = zeros(1,%u);\n", buf_len);
for (i=0; i<buf_len; i++)
fprintf(fid,"syms(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
// power spectral density estimate
fprintf(fid,"nfft = %u;\n", nfft);
fprintf(fid,"f=[0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"psd = zeros(1,nfft);\n");
for (i=0; i<nfft; i++)
fprintf(fid,"psd(%3u) = %12.8f;\n", i+1, psd[i]);
fprintf(fid,"figure('Color','white','position',[500 500 1400 400]);\n");
fprintf(fid,"subplot(1,3,1);\n");
fprintf(fid,"plot(real(syms),imag(syms),'x','MarkerSize',4);\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," title('Last %u symbols');\n", buf_len);
fprintf(fid,"subplot(1,3,2:3);\n");
fprintf(fid," plot(f, psd, 'LineWidth',1.5,'Color',[0 0.5 0.2]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," pmin = 10*floor(0.1*min(psd - 5));\n");
fprintf(fid," pmax = 10*ceil (0.1*max(psd + 5));\n");
fprintf(fid," axis([-0.5 0.5 pmin pmax]);\n");
fprintf(fid," xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid," ylabel('Power Spectral Density [dB]');\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
// destroy objects
symstreamcf_destroy (gen);
spgramcf_destroy (periodogram);
channel_cccf_destroy (channel);
symtrack_cccf_destroy(symtrack);
windowcf_destroy (sym_buf);
// clean it up
printf("done.\n");
return 0;
}
int main(int argc, char*argv[])
{
// options
unsigned int m = 3; // number of bits/symbol
unsigned int k = 0; // filter samples/symbol
unsigned int num_symbols = 8000; // number of data symbols
float SNRdB = 40.0f; // signal-to-noise ratio [dB]
float bandwidth = 0.20; // frequency spacing
unsigned int nfft = 1200; // FFT size for compute spectrum
int dopt;
while ((dopt = getopt(argc,argv,"hm:k:b:n:s:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'm': m = atoi(optarg); break;
case 'k': k = atoi(optarg); break;
case 'b': bandwidth = atof(optarg); break;
case 'n': num_symbols = atoi(optarg); break;
case 's': SNRdB = atof(optarg); break;
default:
exit(1);
}
}
unsigned int i;
unsigned int j;
// derived values
if (k == 0)
k = 2 << m; // set samples per symbol if not otherwise specified
unsigned int M = 1 << m;
float nstd = powf(10.0f, -SNRdB/20.0f);
// validate input
if (k < M) {
fprintf(stderr,"errors: %s, samples/symbol must be at least modulation size (M=%u)\n", __FILE__,M);
exit(1);
} else if (k > 2048) {
fprintf(stderr,"errors: %s, samples/symbol exceeds maximum (2048)\n", __FILE__);
exit(1);
} else if (M > 1024) {
fprintf(stderr,"errors: %s, modulation size (M=%u) exceeds maximum (1024)\n", __FILE__, M);
exit(1);
} else if (bandwidth <= 0.0f || bandwidth >= 0.5f) {
fprintf(stderr,"errors: %s, bandwidht must be in (0,0.5)\n", __FILE__);
exit(1);
}
// create modulator/demodulator pair
fskmod mod = fskmod_create(m,k,bandwidth);
fskdem dem = fskdem_create(m,k,bandwidth);
fskdem_print(dem);
//
float complex buf_tx[k]; // transmit buffer
float complex buf_rx[k]; // transmit buffer
// spectral periodogram
spgramcf periodogram = spgramcf_create_default(nfft);
// modulate, demodulate, count errors
unsigned int num_symbol_errors = 0;
for (i=0; i<num_symbols; i++) {
// generate random symbol
unsigned int sym_in = rand() % M;
// modulate
fskmod_modulate(mod, sym_in, buf_tx);
// add noise
for (j=0; j<k; j++)
buf_rx[j] = buf_tx[j] + nstd*(randnf() + _Complex_I*randnf())*M_SQRT1_2;
// demodulate
unsigned int sym_out = fskdem_demodulate(dem, buf_rx);
// count errors
num_symbol_errors += (sym_in == sym_out) ? 0 : 1;
// estimate power spectral density
spgramcf_write(periodogram, buf_rx, k);
}
printf("symbol errors: %u / %u\n", num_symbol_errors, num_symbols);
// compute power spectral density of received signal
float psd[nfft];
spgramcf_get_psd(periodogram, psd);
spgramcf_destroy(periodogram);
//
// export results
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s : auto-generated file\n", OUTPUT_FILENAME);
fprintf(fid,"clear all\n");
fprintf(fid,"close all\n");
fprintf(fid,"k = %u;\n", k);
fprintf(fid,"M = %u;\n", M);
fprintf(fid,"num_symbols = %u;\n", num_symbols);
fprintf(fid,"nfft = %u;\n", nfft);
// save power spectral density
fprintf(fid,"psd = zeros(1,nfft);\n");
for (i=0; i<nfft; i++)
fprintf(fid,"psd(%4u) = %12.8f;\n", i+1, psd[i]);
// plot PSD
fprintf(fid,"figure('Color','white');\n");
fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"plot(f,psd,'LineWidth',1.5,'Color',[0.5 0 0]);\n");
fprintf(fid,"axis([-0.5 0.5 -40 20]);\n");
fprintf(fid,"xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid,"ylabel('PSD [dB]');\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("results written to '%s'\n", OUTPUT_FILENAME);
return 0;
}