// Helper function to keep code base small
void modem_modulate_bench(struct rusage *_start,
struct rusage *_finish,
unsigned long int *_num_iterations,
modulation_scheme _ms)
{
// normalize number of iterations
switch (_ms) {
case LIQUID_MODEM_UNKNOWN:
fprintf(stderr,"error: modem_modulate_bench(), unknown modem scheme\n");
exit(1);
case LIQUID_MODEM_BPSK: *_num_iterations *= 64; break;
case LIQUID_MODEM_QPSK: *_num_iterations *= 64; break;
case LIQUID_MODEM_OOK: *_num_iterations *= 64; break;
case LIQUID_MODEM_SQAM32: *_num_iterations *= 16; break;
case LIQUID_MODEM_SQAM128: *_num_iterations *= 16; break;
case LIQUID_MODEM_V29: *_num_iterations *= 100; break;
case LIQUID_MODEM_ARB16OPT: *_num_iterations *= 100; break;
case LIQUID_MODEM_ARB32OPT: *_num_iterations *= 100; break;
case LIQUID_MODEM_ARB64OPT: *_num_iterations *= 100; break;
case LIQUID_MODEM_ARB128OPT: *_num_iterations *= 100; break;
case LIQUID_MODEM_ARB256OPT: *_num_iterations *= 100; break;
case LIQUID_MODEM_ARB64VT: *_num_iterations *= 100; break;
default:;
*_num_iterations *= 32;
}
if (*_num_iterations < 1) *_num_iterations = 1;
// initialize modulator
modem mod = modem_create(_ms);
float complex x;
unsigned int symbol_in = 0;
unsigned long int i;
// start trials
getrusage(RUSAGE_SELF, _start);
for (i=0; i<(*_num_iterations); i++) {
modem_modulate(mod, symbol_in, &x);
modem_modulate(mod, symbol_in, &x);
modem_modulate(mod, symbol_in, &x);
modem_modulate(mod, symbol_in, &x);
}
getrusage(RUSAGE_SELF, _finish);
*_num_iterations *= 4;
modem_destroy(mod);
}
// write header symbol
void ofdmflexframegen_write_header(ofdmflexframegen _q,
float complex * _buffer)
{
#if DEBUG_OFDMFLEXFRAMEGEN
printf("writing header symbol\n");
#endif
// load data onto data subcarriers
unsigned int i;
int sctype;
for (i=0; i<_q->M; i++) {
//
sctype = _q->p[i];
//
if (sctype == OFDMFRAME_SCTYPE_DATA) {
// load...
if (_q->header_symbol_index < OFDMFLEXFRAME_H_SYM) {
// modulate header symbol onto data subcarrier
modem_modulate(_q->mod_header, _q->header_mod[_q->header_symbol_index++], &_q->X[i]);
//printf(" writing symbol %3u / %3u (x = %8.5f + j%8.5f)\n", _q->header_symbol_index, OFDMFLEXFRAME_H_SYM, crealf(_q->X[i]), cimagf(_q->X[i]));
} else {
//printf(" random header symbol\n");
// load random symbol
unsigned int sym = modem_gen_rand_sym(_q->mod_payload);
modem_modulate(_q->mod_payload, sym, &_q->X[i]);
}
} else {
// ignore subcarrier (ofdmframegen handles nulls and pilots)
_q->X[i] = 0.0f;
}
}
// write symbol
ofdmframegen_writesymbol(_q->fg, _q->X, _buffer);
// check state
if (_q->symbol_number == _q->num_symbols_header) {
_q->symbol_number = 0;
_q->state = OFDMFLEXFRAMEGEN_STATE_PAYLOAD;
}
}
std::complex < double > MAskFunction::calc(const double &inpt)
{
(void)inpt;
// Create result object, the result of mod will be placed in this.
liquid_float_complex res{0.0f, 0.0f};
// Modulate a random symbol.
modem_modulate(_mod, modem_gen_rand_sym(_mod), &res);
return std::complex<double>((double)res.real, (double)res.imag);
}
// write payload symbol
void ofdmflexframegen_write_payload(ofdmflexframegen _q,
float complex * _buffer)
{
#if DEBUG_OFDMFLEXFRAMEGEN
printf("writing payload symbol\n");
#endif
// load data onto data subcarriers
unsigned int i;
int sctype;
for (i=0; i<_q->M; i++) {
//
sctype = _q->p[i];
//
if (sctype == OFDMFRAME_SCTYPE_DATA) {
// load...
if (_q->payload_symbol_index < _q->payload_mod_len) {
// modulate payload symbol onto data subcarrier
modem_modulate(_q->mod_payload, _q->payload_mod[_q->payload_symbol_index++], &_q->X[i]);
} else {
//printf(" random payload symbol\n");
// load random symbol
unsigned int sym = modem_gen_rand_sym(_q->mod_payload);
modem_modulate(_q->mod_payload, sym, &_q->X[i]);
}
} else {
// ignore subcarrier (ofdmframegen handles nulls and pilots)
_q->X[i] = 0.0f;
}
}
// write symbol
ofdmframegen_writesymbol(_q->fg, _q->X, _buffer);
// check to see if this is the last symbol in the payload
if (_q->symbol_number == _q->num_symbols_payload)
_q->frame_complete = 1;
}
// Help function to keep code base small
void modem_test_demodsoft(modulation_scheme _ms)
{
// generate mod/demod
modem mod = modem_create(_ms);
modem demod = modem_create(_ms);
//
unsigned int bps = modem_get_bps(demod);
// run the test
unsigned int i, s, M=1<<bps;
unsigned int sym_soft;
unsigned char soft_bits[bps];
float complex x;
for (i=0; i<M; i++) {
// modulate symbol
modem_modulate(mod, i, &x);
// demodulate using soft-decision
modem_demodulate_soft(demod, x, &s, soft_bits);
// check hard-decision output
CONTEND_EQUALITY(s, i);
// check soft bits
liquid_pack_soft_bits(soft_bits, bps, &sym_soft);
CONTEND_EQUALITY(sym_soft, i);
// check phase error, evm, etc.
//CONTEND_DELTA( modem_get_demodulator_phase_error(demod), 0.0f, 1e-3f);
//CONTEND_DELTA( modem_get_demodulator_evm(demod), 0.0f, 1e-3f);
}
// clean it up
modem_destroy(mod);
modem_destroy(demod);
}
int main(int argc, char*argv[])
{
// set random number generator seed
srand(time(NULL));
// options
unsigned int M = 64; // number of subcarriers
unsigned int cp_len = 16; // cyclic prefix length
modulation_scheme ms = LIQUID_MODEM_BPSK;
float SNRdB = 6.5f; // signal-to-noise ratio [dB]
unsigned int hc_len = 1; // channel impulse response length
unsigned int num_symbols = 40; // number of OFDM symbols
// get options
int dopt;
while((dopt = getopt(argc,argv,"hs:M:C:m:n:c:")) != EOF){
switch (dopt) {
case 'h': usage(); return 0;
case 's': SNRdB = atof(optarg); break;
case 'M': M = atoi(optarg); break;
case 'C': cp_len = atoi(optarg); break;
case 'm':
ms = liquid_getopt_str2mod(optarg);
if (ms == LIQUID_MODEM_UNKNOWN) {
fprintf(stderr,"error: %s, unknown/unsupported mod. scheme: %s\n", argv[0], optarg);
exit(-1);
}
break;
case 'n': num_symbols = atoi(optarg); break;
case 'c': hc_len = atoi(optarg); break;
default:
exit(-1);
}
}
unsigned int i;
// validate options
if (M < 4) {
fprintf(stderr,"error: %s, must have at least 4 subcarriers\n", argv[0]);
exit(1);
} else if (hc_len == 0) {
fprintf(stderr,"error: %s, must have at least 1 channel tap\n", argv[0]);
exit(1);
}
// derived values
unsigned int symbol_len = M + cp_len;
float nstd = powf(10.0f, -SNRdB/20.0f);
float fft_gain = 1.0f / sqrtf(M); // 'gain' due to taking FFT
// buffers
unsigned int sym_in[M]; // input data symbols
unsigned int sym_out[M]; // output data symbols
float complex x[M]; // time-domain buffer
float complex X[M]; // freq-domain buffer
float complex buffer[symbol_len]; //
// create modulator/demodulator objects
modem mod = modem_create(ms);
modem demod = modem_create(ms);
unsigned int bps = modem_get_bps(mod); // modem bits/symbol
// create channel filter (random taps)
float complex hc[hc_len];
hc[0] = 1.0f;
for (i=1; i<hc_len; i++)
hc[i] = 0.1f * (randnf() + _Complex_I*randnf());
firfilt_cccf fchannel = firfilt_cccf_create(hc, hc_len);
//
unsigned int n;
unsigned int num_bit_errors = 0;
for (n=0; n<num_symbols; n++) {
// generate random data symbols and modulate onto subcarriers
for (i=0; i<M; i++) {
sym_in[i] = rand() % (1<<bps);
modem_modulate(mod, sym_in[i], &X[i]);
}
// run inverse transform
fft_run(M, X, x, LIQUID_FFT_BACKWARD, 0);
// scale by FFT gain so E{|x|^2} = 1
for (i=0; i<M; i++)
x[i] *= fft_gain;
// apply channel impairments
for (i=0; i<M + cp_len; i++) {
// push samples through channel filter, starting with cyclic prefix
firfilt_cccf_push(fchannel, x[(M-cp_len+i)%M]);
// compute output
firfilt_cccf_execute(fchannel, &buffer[i]);
// add noise
buffer[i] += nstd*( randnf() + _Complex_I*randnf() ) * M_SQRT1_2;
}
// run forward transform
fft_run(M, &buffer[cp_len], X, LIQUID_FFT_FORWARD, 0);
// TODO : apply equalizer to 'X' here
// demodulate and compute bit errors
for (i=0; i<M; i++) {
// scale by fft size
X[i] *= fft_gain;
modem_demodulate(demod, X[i], &sym_out[i]);
num_bit_errors += liquid_count_ones(sym_in[i] ^ sym_out[i]);
}
}
// destroy objects
modem_destroy(mod);
modem_destroy(demod);
firfilt_cccf_destroy(fchannel);
// print results
unsigned int total_bits = M*bps*num_symbols;
float ber = (float)num_bit_errors / (float)total_bits;
printf(" bit errors : %6u / %6u (%12.4e)\n", num_bit_errors, total_bits, ber);
printf("done.\n");
return 0;
}
int main(int argc, char*argv[]) {
// create mod/demod objects
float gnuplot_version=0.0;
enum {GNUPLOT_TERM_PNG=0,
GNUPLOT_TERM_JPG,
GNUPLOT_TERM_EPS
} gnuplot_term = 0;
char input_filename[256] = "datafile.dat";
char output_filename[256] = "modem.gnu";
//char figure_title[256] = "constellation";
modulation_scheme ms = LIQUID_MODEM_QPSK;
int dopt;
while ((dopt = getopt(argc,argv,"uhg:t:d:f:m:")) != EOF) {
switch (dopt) {
case 'u':
case 'h':
usage();
return 0;
case 'g': gnuplot_version = atof(optarg); break;
case 't': gnuplot_term = atoi(optarg); break;
case 'd': strncpy(input_filename,optarg,256); break;
case 'f': strncpy(output_filename,optarg,256); break;
case 'm':
ms = liquid_getopt_str2mod(optarg);
if (ms == LIQUID_MODEM_UNKNOWN) {
fprintf(stderr,"error: %s, unknown/unsupported modulation scheme \"%s\"\n", argv[0], optarg);
return 1;
}
break;
default:
exit(1);
}
}
// TODO : validate input
if (ms == LIQUID_MODEM_UNKNOWN || ms >= LIQUID_MODEM_NUM_SCHEMES) {
fprintf(stderr,"error: %s, invalid modulation scheme \n", argv[0]);
return 1;
}
// derived options/values
unsigned int bps = modulation_types[ms].bps;
int plot_labels = (gnuplot_version > 4.1) && (bps < 8);
int plot_long_labels = 0;
unsigned int i;
// generate modem, compute constellation, derive plot style accordingly
unsigned int M = 1<<bps;
float complex constellation[M];
modem q = modem_create(ms);
for (i=0; i<M; i++)
modem_modulate(q, i, &constellation[i]);
modem_destroy(q);
float range = 1.5f;
enum {AXES_POLAR, AXES_CART} axes = AXES_POLAR;
switch (ms) {
// Phase-shift keying (PSK)
case LIQUID_MODEM_PSK2:
case LIQUID_MODEM_PSK4:
case LIQUID_MODEM_PSK8:
case LIQUID_MODEM_PSK16:
case LIQUID_MODEM_PSK32:
case LIQUID_MODEM_PSK64:
case LIQUID_MODEM_PSK128:
case LIQUID_MODEM_PSK256:
// Differential phase-shift keying (DPSK)
case LIQUID_MODEM_DPSK2:
case LIQUID_MODEM_DPSK4:
case LIQUID_MODEM_DPSK8:
case LIQUID_MODEM_DPSK16:
case LIQUID_MODEM_DPSK32:
case LIQUID_MODEM_DPSK64:
case LIQUID_MODEM_DPSK128:
case LIQUID_MODEM_DPSK256:
range = 1.2f;
axes = AXES_POLAR;
break;
// amplitude-shift keying (ASK)
case LIQUID_MODEM_ASK2: range = 1.2f; axes = AXES_CART; break;
case LIQUID_MODEM_ASK4: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ASK8: range = 1.75f; axes = AXES_CART; break;
case LIQUID_MODEM_ASK16: range = 2.00f; axes = AXES_CART; break;
case LIQUID_MODEM_ASK32: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ASK64: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ASK128: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ASK256: range = 1.5f; axes = AXES_CART; break;
// rectangular quadrature amplitude-shift keying (QAM)
case LIQUID_MODEM_QAM4: range = 1.75f; axes = AXES_CART; break;
case LIQUID_MODEM_QAM8: range = 1.75f; axes = AXES_CART; break;
case LIQUID_MODEM_QAM16: range = 1.75f; axes = AXES_CART; break;
case LIQUID_MODEM_QAM32: range = 1.75f; axes = AXES_CART; break;
case LIQUID_MODEM_QAM64: range = 1.75f; axes = AXES_CART; break;
case LIQUID_MODEM_QAM128: range = 1.75f; axes = AXES_CART; break;
case LIQUID_MODEM_QAM256: range = 1.75f; axes = AXES_CART; break;
// amplitude phase-shift keying (APSK)
case LIQUID_MODEM_APSK4: range = 1.5f; axes = AXES_POLAR; break;
case LIQUID_MODEM_APSK8: range = 1.5f; axes = AXES_POLAR; break;
case LIQUID_MODEM_APSK16: range = 1.5f; axes = AXES_POLAR; break;
case LIQUID_MODEM_APSK32: range = 1.5f; axes = AXES_POLAR; break;
case LIQUID_MODEM_APSK64: range = 1.5f; axes = AXES_POLAR; break;
case LIQUID_MODEM_APSK128: range = 1.5f; axes = AXES_POLAR; break;
case LIQUID_MODEM_APSK256: range = 1.5f; axes = AXES_POLAR; break;
// specific modems
case LIQUID_MODEM_BPSK: range = 1.5f; axes = AXES_POLAR; break;
case LIQUID_MODEM_QPSK: range = 1.5f; axes = AXES_POLAR; break;
case LIQUID_MODEM_OOK: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_SQAM32: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_SQAM128: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_V29: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ARB16OPT: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ARB32OPT: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ARB64OPT: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ARB128OPT: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ARB256OPT: range = 1.5f; axes = AXES_CART; break;
case LIQUID_MODEM_ARB64VT: range = 2.0f; axes = AXES_CART; break;
default:
fprintf(stderr,"error: %s, invalid modulation scheme\n", argv[0]);
exit(1);
}
// determine minimum distance between any two points
float dmin = 0.0f;
for (i=0; i<M; i++) {
unsigned int j;
for (j=i+1; j<M; j++) {
float d = cabsf(constellation[i] - constellation[j]);
if ( (d < dmin) || (i==0 && j==1) )
dmin = d;
}
}
plot_long_labels = dmin < 0.34 ? 0 : 1;
// write output file
FILE * fid = fopen(output_filename,"w");
if (fid == NULL) {
fprintf(stderr,"error: %s, could not open file \"%s\" for writing.\n", argv[0],output_filename);
exit(1);
}
// print header
fprintf(fid,"# %s : auto-generated file (do not edit)\n", output_filename);
fprintf(fid,"# invoked as :");
for (i=0; i<argc; i++)
fprintf(fid," %s",argv[i]);
fprintf(fid,"\n");
fprintf(fid,"reset\n");
fprintf(fid,"set terminal postscript eps enhanced color solid rounded\n");
// TODO : set range according to scheme
fprintf(fid,"set xrange [-%4.2f:%4.2f]\n",range,range);
fprintf(fid,"set yrange [-%4.2f:%4.2f]\n",range,range);
fprintf(fid,"set size square\n");
//fprintf(fid,"set title \"%s\"\n", figure_title);
fprintf(fid,"set xlabel \"I\"\n");
fprintf(fid,"set ylabel \"Q\"\n");
fprintf(fid,"set nokey # disable legned\n");
// TODO : set grid type (e.g. polar) according to scheme
//
if (axes == AXES_POLAR)
fprintf(fid,"set grid polar\n");
else
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,"set pointsize 1.0\n");
if (!plot_labels) {
// do not print labels
fprintf(fid,"plot '%s' using 1:2 with points pointtype 7 linecolor rgb '#004080'\n",input_filename);
} else {
// print labels
fprintf(fid,"xoffset = %8.6f\n", plot_long_labels ? 0.0 : 0.045f);
fprintf(fid,"yoffset = %8.6f\n", plot_long_labels ? 0.06f : 0.045f);
unsigned int label_line = plot_long_labels ? 3 : 4;
fprintf(fid,"plot '%s' using 1:2 with points pointtype 7 linecolor rgb '#004080',\\\n",input_filename);
fprintf(fid," '%s' using ($1+xoffset):($2+yoffset):%u with labels font 'arial,10'\n", input_filename,label_line);
}
// close it up
fclose(fid);
return 0;
}
int main(int argc, char*argv[])
{
// create mod/demod objects
modulation_scheme ms = LIQUID_MODEM_ARB64VT;
modulation_scheme mref = LIQUID_MODEM_QAM64;
float alpha = 1.0f;
int dopt;
while ((dopt = getopt(argc,argv,"uhp:m:r:a:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'm':
ms = liquid_getopt_str2mod(optarg);
if (ms == LIQUID_MODEM_UNKNOWN) {
fprintf(stderr,"error: %s, unknown/unsupported modulation scheme '%s'\n", argv[0], optarg);
return 1;
}
break;
case 'r':
mref = liquid_getopt_str2mod(optarg);
if (mref == LIQUID_MODEM_UNKNOWN) {
fprintf(stderr,"error: %s, unknown/unsupported modulation scheme '%s'\n", argv[0], optarg);
return 1;
}
break;
case 'a': alpha = atof(optarg); break;
default:
exit(1);
}
}
// validate input
unsigned int i;
unsigned int j;
// initialize reference points
modem qref = modem_create(mref);
unsigned int kref = modem_get_bps(qref);
unsigned int p = 1 << kref;
float complex cref[p];
for (i=0; i<p; i++) {
modem_modulate(qref, i, &cref[i]);
cref[i] *= alpha;
}
modem_destroy(qref);
// generate the constellation
modem q = modem_create(ms);
unsigned int bps = modem_get_bps(q);
unsigned int M = 1 << bps;
float complex constellation[M];
for (i=0; i<M; i++)
modem_modulate(q, i, &constellation[i]);
modem_destroy(q);
// perform search
unsigned char * link = NULL;
unsigned int num_unassigned=M;
unsigned char unassigned[M];
unsigned int s=0; // number of points per reference
// run search until all points are found
do {
// increment number of points per reference
s++;
// reallocte memory for links
link = (unsigned char*) realloc(link, p*s);
// search for nearest constellation points to reference points
modem_arbref_search(constellation, M, cref, p, link, s);
// find unassigned constellation points
num_unassigned = modem_arbref_search_unassigned(link,M,p,s,unassigned);
printf("%3u : number of unassigned points: %3u / %3u\n", s, num_unassigned, M);
} while (num_unassigned > 0);
// print table
printf("\n");
printf("unsigned char modem_demodulate_gentab[%u][%u] = {\n", p, s);
for (i=0; i<p; i++) {
printf(" {");
for (j=0; j<s; j++) {
printf("%3u%s", link[i*s+j], j==(s-1) ? "" : ",");
}
printf("}%s", i==(p-1) ? "};\n" : ",\n");
}
//
// export output file
//
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,"bps = %u;\n", bps);
fprintf(fid,"M = %u;\n", M);
fprintf(fid,"p = %u;\n", p);
fprintf(fid,"s = %u;\n", s);
// save constellation points
for (i=0; i<M; i++) {
fprintf(fid,"c(%3u) = %12.4e + j*%12.4e;\n", i+1,
crealf(constellation[i]),
cimagf(constellation[i]));
}
// save reference points
for (i=0; i<p; i++)
fprintf(fid,"cref(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(cref[i]), cimagf(cref[i]));
// save reference matrix
fprintf(fid,"link = zeros(p,s);\n");
for (i=0; i<p; i++) {
for (j=0; j<s; j++) {
fprintf(fid,"link(%3u,%3u) = %u;\n", i+1, j+1, link[i*s+j]+1);
}
}
// plot results
fprintf(fid,"figure;\n");
fprintf(fid,"plot(real(c), imag(c), 'bx',\n");
fprintf(fid," real(cref), imag(cref),'or');\n");
// draw lines between reference points and associated constellation points
fprintf(fid,"hold on;\n");
fprintf(fid," for i=1:p,\n");
fprintf(fid," for j=1:s,\n");
fprintf(fid," plot([real(cref(i)) real(c(link(i,j)))], [imag(cref(i)) imag(c(link(i,j)))], '-', 'Color', 0.8*[1 1 1]);\n");
fprintf(fid," end;\n");
fprintf(fid," end;\n");
fprintf(fid,"hold off;\n");
fprintf(fid,"xlabel('in-phase');\n");
fprintf(fid,"ylabel('quadrature phase');\n");
fprintf(fid,"%%legend('constellation','reference','links',0);\n");
fprintf(fid,"title(['Arbitrary ' num2str(M) '-QAM']);\n");
fprintf(fid,"axis([-1 1 -1 1]*1.9);\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("results written to '%s'\n", OUTPUT_FILENAME);
printf("done.\n");
// free allocated memory
free(link);
return 0;
}
int main(int argc, char*argv[])
{
// options
float noise_floor= -40.0f; // noise floor [dB]
float SNRdB = 20.0f; // signal-to-noise ratio [dB]
float bt = 0.05f; // loop bandwidth
unsigned int num_symbols= 100; // number of iterations
unsigned int d = 5; // print every d iterations
unsigned int k = 2; // interpolation factor (samples/symbol)
unsigned int m = 3; // filter delay (symbols)
float beta = 0.3f; // filter excess bandwidth factor
float dt = 0.0f; // filter fractional sample delay
// derived values
unsigned int num_samples=num_symbols*k;
float gamma = powf(10.0f, (SNRdB+noise_floor)/20.0f); // channel gain
float nstd = powf(10.0f, noise_floor / 20.0f);
// arrays
float complex x[num_samples];
float complex y[num_samples];
float rssi[num_samples];
// create objects
modem mod = modem_create(LIQUID_MODEM_QPSK);
firinterp_crcf interp = firinterp_crcf_create_prototype(LIQUID_FIRFILT_RRC,k,m,beta,dt);
agc_crcf p = agc_crcf_create();
agc_crcf_set_bandwidth(p, bt);
unsigned int i;
// print info
printf("automatic gain control // loop bandwidth: %4.2e\n",bt);
unsigned int sym;
float complex s;
for (i=0; i<num_symbols; i++) {
// generate random symbol
sym = modem_gen_rand_sym(mod);
modem_modulate(mod, sym, &s);
s *= gamma;
firinterp_crcf_execute(interp, s, &x[i*k]);
}
// add noise
for (i=0; i<num_samples; i++)
x[i] += nstd*(randnf() + _Complex_I*randnf()) * M_SQRT1_2;
// run agc
for (i=0; i<num_samples; i++) {
agc_crcf_execute(p, x[i], &y[i]);
rssi[i] = agc_crcf_get_rssi(p);
}
// destroy objects
modem_destroy(mod);
agc_crcf_destroy(p);
firinterp_crcf_destroy(interp);
// print results to screen
printf("received signal strength indication (rssi):\n");
for (i=0; i<num_samples; i+=d) {
printf("%4u : %8.2f\n", i, rssi[i]);
}
//
// export results
//
FILE* fid = fopen(OUTPUT_FILENAME,"w");
if (!fid) {
fprintf(stderr,"error: %s, could not open '%s' for writing\n", argv[0], OUTPUT_FILENAME);
exit(1);
}
fprintf(fid,"%% %s: auto-generated file\n\n",OUTPUT_FILENAME);
fprintf(fid,"n = %u;\n", num_samples);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n\n");
for (i=0; i<num_samples; i++) {
fprintf(fid," x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
fprintf(fid," y(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
fprintf(fid,"rssi(%4u) = %12.4e;\n", i+1, rssi[i]);
}
fprintf(fid,"\n\n");
fprintf(fid,"n = length(x);\n");
fprintf(fid,"t = 0:(n-1);\n");
fprintf(fid,"figure('position',[100 100 800 600]);\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(t,rssi,'-k','LineWidth',2);\n");
fprintf(fid," xlabel('sample index');\n");
fprintf(fid," ylabel('rssi [dB]');\n");
fprintf(fid," grid on;\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(t,real(y),t,imag(y));\n");
fprintf(fid," xlabel('sample index');\n");
fprintf(fid," ylabel('agc output');\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[]) {
srand( time(NULL) );
// parameters
float phase_offset = M_PI/10;
float frequency_offset = 0.001f;
float SNRdB = 30.0f;
float pll_bandwidth = 0.02f;
modulation_scheme ms = LIQUID_MODEM_QPSK;
unsigned int n=256; // number of iterations
int dopt;
while ((dopt = getopt(argc,argv,"uhs:b:n:P:F:m:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 's': SNRdB = atof(optarg); break;
case 'b': pll_bandwidth = atof(optarg); break;
case 'n': n = atoi(optarg); break;
case 'P': phase_offset = atof(optarg); break;
case 'F': frequency_offset= atof(optarg); break;
case 'm':
ms = liquid_getopt_str2mod(optarg);
if (ms == LIQUID_MODEM_UNKNOWN) {
fprintf(stderr,"error: %s, unknown/unsupported modulation scheme \"%s\"\n", argv[0], optarg);
return 1;
}
break;
default:
exit(1);
}
}
unsigned int d=n/32; // print every "d" lines
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid, "%% %s : auto-generated file\n", OUTPUT_FILENAME);
fprintf(fid, "clear all;\n");
fprintf(fid, "phi=zeros(1,%u);\n",n);
fprintf(fid, "r=zeros(1,%u);\n",n);
// objects
nco_crcf nco_tx = nco_crcf_create(LIQUID_VCO);
nco_crcf nco_rx = nco_crcf_create(LIQUID_VCO);
modem mod = modem_create(ms);
modem demod = modem_create(ms);
unsigned int bps = modem_get_bps(mod);
// initialize objects
nco_crcf_set_phase(nco_tx, phase_offset);
nco_crcf_set_frequency(nco_tx, frequency_offset);
nco_crcf_pll_set_bandwidth(nco_rx, pll_bandwidth);
float noise_power = powf(10.0f, -SNRdB/20.0f);
// print parameters
printf("PLL example :\n");
printf("modem : %u-%s\n", 1<<bps, modulation_types[ms].name);
printf("frequency offset: %6.3f, phase offset: %6.3f, SNR: %6.2fdB, pll b/w: %6.3f\n",
frequency_offset, phase_offset, SNRdB, pll_bandwidth);
// run loop
unsigned int i, M=1<<bps, sym_in, sym_out, num_errors=0;
float phase_error;
float complex x, r, v, noise;
for (i=0; i<n; i++) {
// generate random symbol
sym_in = rand() % M;
// modulate
modem_modulate(mod, sym_in, &x);
// channel
//r = nco_crcf_cexpf(nco_tx);
nco_crcf_mix_up(nco_tx, x, &r);
// add complex white noise
crandnf(&noise);
r += noise * noise_power;
//
//v = nco_crcf_cexpf(nco_rx);
nco_crcf_mix_down(nco_rx, r, &v);
// demodulate
modem_demodulate(demod, v, &sym_out);
num_errors += count_bit_errors(sym_in, sym_out);
// error estimation
//phase_error = cargf(r*conjf(v));
phase_error = modem_get_demodulator_phase_error(demod);
// perfect error estimation
//phase_error = nco_tx->theta - nco_rx->theta;
// print every line in a format that octave can read
fprintf(fid, "phi(%u) = %10.6E;\n", i+1, phase_error);
fprintf(fid, "r(%u) = %10.6E + j*%10.6E;\n",
i+1, crealf(v), cimagf(v));
if ((i+1)%d == 0 || i==n-1) {
printf(" %4u: e_hat : %6.3f, phase error : %6.3f, freq error : %6.3f\n",
i+1, // iteration
phase_error, // estimated phase error
nco_crcf_get_phase(nco_tx) - nco_crcf_get_phase(nco_rx),// true phase error
nco_crcf_get_frequency(nco_tx) - nco_crcf_get_frequency(nco_rx)// true frequency error
);
}
// update tx nco object
nco_crcf_step(nco_tx);
// update pll
nco_crcf_pll_step(nco_rx, phase_error);
// update rx nco object
nco_crcf_step(nco_rx);
}
fprintf(fid, "figure;\n");
fprintf(fid, "plot(1:length(phi),phi,'LineWidth',2,'Color',[0 0.25 0.5]);\n");
fprintf(fid, "xlabel('Symbol Index');\n");
fprintf(fid, "ylabel('Phase Error [radians]');\n");
fprintf(fid, "grid on;\n");
fprintf(fid, "t0 = round(0.25*length(r));\n");
fprintf(fid, "figure;\n");
fprintf(fid, "plot(r(1:t0),'x','Color',[0.6 0.6 0.6],r(t0:end),'x','Color',[0 0.25 0.5]);\n");
fprintf(fid, "grid on;\n");
fprintf(fid, "axis([-1.5 1.5 -1.5 1.5]);\n");
fprintf(fid, "axis('square');\n");
fprintf(fid, "xlabel('In-Phase');\n");
fprintf(fid, "ylabel('Quadrature');\n");
fprintf(fid, "legend(['first 25%%'],['last 75%%'],1);\n");
fclose(fid);
printf("results written to %s.\n",OUTPUT_FILENAME);
nco_crcf_destroy(nco_tx);
nco_crcf_destroy(nco_rx);
modem_destroy(mod);
modem_destroy(demod);
printf("bit errors: %u / %u\n", num_errors, bps*n);
printf("done.\n");
return 0;
}
// Helper function to keep code base small
void ofdmframesync_rxsymbol_bench(struct rusage *_start,
struct rusage *_finish,
unsigned long int *_num_iterations,
unsigned int _num_subcarriers,
unsigned int _cp_len)
{
// options
modulation_scheme ms = LIQUID_MODEM_QPSK;
unsigned int M = _num_subcarriers;
unsigned int cp_len = _cp_len;
unsigned int taper_len = 0;
// create synthesizer/analyzer objects
ofdmframegen fg = ofdmframegen_create(M, cp_len, taper_len, NULL);
//ofdmframegen_print(fg);
modem mod = modem_create(ms);
ofdmframesync fs = ofdmframesync_create(M,cp_len,taper_len,NULL,NULL,NULL);
unsigned int i;
float complex X[M]; // channelized symbol
float complex x[M+cp_len]; // time-domain symbol
// synchronize short sequence (first)
ofdmframegen_write_S0a(fg, x);
ofdmframesync_execute(fs, x, M+cp_len);
// synchronize short sequence (second)
ofdmframegen_write_S0b(fg, x);
ofdmframesync_execute(fs, x, M+cp_len);
// synchronize long sequence
ofdmframegen_write_S1(fg, x);
ofdmframesync_execute(fs, x, M+cp_len);
// modulate data symbols (use same symbol, ignore pilot phase)
unsigned int s;
for (i=0; i<M; i++) {
s = modem_gen_rand_sym(mod);
modem_modulate(mod,s,&X[i]);
}
ofdmframegen_writesymbol(fg, X, x);
// add noise
for (i=0; i<M+cp_len; i++)
x[i] += 0.02f*randnf()*cexpf(_Complex_I*2*M_PI*randf());
// normalize number of iterations
*_num_iterations /= M;
// start trials
getrusage(RUSAGE_SELF, _start);
for (i=0; i<(*_num_iterations); i++) {
// receive data symbols (ignoring pilots)
ofdmframesync_execute(fs, x, M+cp_len);
ofdmframesync_execute(fs, x, M+cp_len);
ofdmframesync_execute(fs, x, M+cp_len);
ofdmframesync_execute(fs, x, M+cp_len);
}
getrusage(RUSAGE_SELF, _finish);
*_num_iterations *= 4;
// destroy objects
ofdmframegen_destroy(fg);
ofdmframesync_destroy(fs);
modem_destroy(mod);
}
int main(int argc, char*argv[])
{
srand(time(NULL));
// options
unsigned int num_symbols=500; // number of symbols to observe
float SNRdB = 30.0f; // signal-to-noise ratio [dB]
unsigned int hc_len=5; // channel filter length
unsigned int k=2; // matched filter samples/symbol
unsigned int m=3; // matched filter delay (symbols)
float beta=0.3f; // matched filter excess bandwidth factor
unsigned int p=3; // equalizer length (symbols, hp_len = 2*k*p+1)
float mu = 0.08f; // learning rate
// modulation type/depth
modulation_scheme ms = LIQUID_MODEM_QPSK;
int dopt;
while ((dopt = getopt(argc,argv,"hn:s:c:k:m:b:p:u:M:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'n': num_symbols = atoi(optarg); break;
case 's': SNRdB = atof(optarg); break;
case 'c': hc_len = atoi(optarg); break;
case 'k': k = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 'b': beta = atof(optarg); break;
case 'p': p = atoi(optarg); break;
case 'u': mu = atof(optarg); break;
case 'M':
ms = liquid_getopt_str2mod(optarg);
if (ms == LIQUID_MODEM_UNKNOWN) {
fprintf(stderr,"error: %s, unknown/unsupported modulation scheme '%s'\n", argv[0], optarg);
return 1;
}
break;
default:
exit(1);
}
}
// validate input
if (num_symbols == 0) {
fprintf(stderr,"error: %s, number of symbols must be greater than zero\n", argv[0]);
exit(1);
} else if (hc_len == 0) {
fprintf(stderr,"error: %s, channel must have at least 1 tap\n", argv[0]);
exit(1);
} else if (k < 2) {
fprintf(stderr,"error: %s, samples/symbol must be at least 2\n", argv[0]);
exit(1);
} else if (m == 0) {
fprintf(stderr,"error: %s, filter semi-length must be at least 1 symbol\n", argv[0]);
exit(1);
} else if (beta < 0.0f || beta > 1.0f) {
fprintf(stderr,"error: %s, filter excess bandwidth must be in [0,1]\n", argv[0]);
exit(1);
} else if (p == 0) {
fprintf(stderr,"error: %s, equalizer semi-length must be at least 1 symbol\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);
}
// derived values
unsigned int hm_len = 2*k*m+1; // matched filter length
unsigned int hp_len = 2*k*p+1; // equalizer filter length
unsigned int num_samples = k*num_symbols;
// bookkeeping variables
float complex sym_tx[num_symbols]; // transmitted data sequence
float complex x[num_samples]; // interpolated time series
float complex y[num_samples]; // channel output
float complex z[num_samples]; // equalized output
float hm[hm_len]; // matched filter response
float complex hc[hc_len]; // channel filter coefficients
float complex hp[hp_len]; // equalizer filter coefficients
unsigned int i;
// generate matched filter response
liquid_firdes_rnyquist(LIQUID_FIRFILT_RRC, k, m, beta, 0.0f, hm);
firinterp_crcf interp = firinterp_crcf_create(k, hm, hm_len);
// create the modem objects
modem mod = modem_create(ms);
modem demod = modem_create(ms);
unsigned int M = 1 << modem_get_bps(mod);
// generate channel impulse response, filter
hc[0] = 1.0f;
for (i=1; i<hc_len; i++)
hc[i] = 0.09f*(randnf() + randnf()*_Complex_I);
firfilt_cccf fchannel = firfilt_cccf_create(hc, hc_len);
// generate random symbols
for (i=0; i<num_symbols; i++)
modem_modulate(mod, rand()%M, &sym_tx[i]);
// interpolate
for (i=0; i<num_symbols; i++)
firinterp_crcf_execute(interp, sym_tx[i], &x[i*k]);
// push through channel
float nstd = powf(10.0f, -SNRdB/20.0f);
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;
}
// push through equalizer
// create equalizer, intialized with square-root Nyquist filter
eqlms_cccf eq = eqlms_cccf_create_rnyquist(LIQUID_FIRFILT_RRC, k, p, beta, 0.0f);
eqlms_cccf_set_bw(eq, mu);
// get initialized weights
eqlms_cccf_get_weights(eq, hp);
// filtered error vector magnitude (emperical RMS error)
float evm_hat = 0.03f;
float complex d_hat = 0.0f;
for (i=0; i<num_samples; i++) {
// print filtered evm (emperical rms error)
if ( ((i+1)%50)==0 )
printf("%4u : rms error = %12.8f dB\n", i+1, 10*log10(evm_hat));
eqlms_cccf_push(eq, y[i]);
eqlms_cccf_execute(eq, &d_hat);
// store output
z[i] = d_hat;
// decimate by k
if ( (i%k) != 0 ) continue;
// estimate transmitted signal
unsigned int sym_out; // output symbol
float complex d_prime; // estimated input sample
modem_demodulate(demod, d_hat, &sym_out);
modem_get_demodulator_sample(demod, &d_prime);
// update equalizer
eqlms_cccf_step(eq, d_prime, d_hat);
// update filtered evm estimate
float evm = crealf( (d_prime-d_hat)*conjf(d_prime-d_hat) );
evm_hat = 0.98f*evm_hat + 0.02f*evm;
}
// get equalizer weights
eqlms_cccf_get_weights(eq, hp);
// destroy objects
eqlms_cccf_destroy(eq);
firinterp_crcf_destroy(interp);
firfilt_cccf_destroy(fchannel);
modem_destroy(mod);
modem_destroy(demod);
//
// export output
//
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");
fprintf(fid,"k = %u;\n", k);
fprintf(fid,"m = %u;\n", m);
fprintf(fid,"num_symbols = %u;\n", num_symbols);
fprintf(fid,"num_samples = num_symbols*k;\n");
// save transmit matched-filter response
fprintf(fid,"hm_len = 2*k*m+1;\n");
fprintf(fid,"hm = zeros(1,hm_len);\n");
for (i=0; i<hm_len; i++)
fprintf(fid,"hm(%4u) = %12.4e;\n", i+1, hm[i]);
// save channel impulse response
fprintf(fid,"hc_len = %u;\n", hc_len);
fprintf(fid,"hc = zeros(1,hc_len);\n");
for (i=0; i<hc_len; i++)
fprintf(fid,"hc(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(hc[i]), cimagf(hc[i]));
// save equalizer response
fprintf(fid,"hp_len = %u;\n", hp_len);
fprintf(fid,"hp = zeros(1,hp_len);\n");
for (i=0; i<hp_len; i++)
fprintf(fid,"hp(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(hp[i]), cimagf(hp[i]));
// save sample sets
fprintf(fid,"x = zeros(1,num_samples);\n");
fprintf(fid,"y = zeros(1,num_samples);\n");
fprintf(fid,"z = zeros(1,num_samples);\n");
for (i=0; i<num_samples; i++) {
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(x[i]), cimagf(x[i]));
fprintf(fid,"y(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(y[i]), cimagf(y[i]));
fprintf(fid,"z(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(z[i]), cimagf(z[i]));
}
// plot time response
fprintf(fid,"t = 0:(num_samples-1);\n");
fprintf(fid,"tsym = 1:k:num_samples;\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(t,real(z),...\n");
fprintf(fid," t(tsym),real(z(tsym)),'x');\n");
// plot constellation
fprintf(fid,"tsym0 = tsym(1:(length(tsym)/2));\n");
fprintf(fid,"tsym1 = tsym((length(tsym)/2):end);\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(real(z(tsym0)),imag(z(tsym0)),'x','Color',[1 1 1]*0.7,...\n");
fprintf(fid," real(z(tsym1)),imag(z(tsym1)),'x','Color',[1 1 1]*0.0);\n");
fprintf(fid,"xlabel('In-Phase');\n");
fprintf(fid,"ylabel('Quadrature');\n");
fprintf(fid,"axis([-1 1 -1 1]*1.5);\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"grid on;\n");
// compute composite response
fprintf(fid,"g = real(conv(conv(hm,hc),hp));\n");
// plot responses
fprintf(fid,"nfft = 1024;\n");
fprintf(fid,"f = [0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"Hm = 20*log10(abs(fftshift(fft(hm/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,"G = 20*log10(abs(fftshift(fft(g/k, nfft))));\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(f,Hm, f,Hc, f,Hp, f,G,'-k','LineWidth',2, [-0.5/k 0.5/k],[-6.026 -6.026],'or');\n");
fprintf(fid,"xlabel('Normalized Frequency');\n");
fprintf(fid,"ylabel('Power Spectral Density');\n");
fprintf(fid,"legend('transmit','channel','equalizer','composite','half-power points',1);\n");
fprintf(fid,"axis([-0.5 0.5 -12 8]);\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("results written to '%s'\n", OUTPUT_FILENAME);
return 0;
}
int main(int argc, char*argv[])
{
// options
unsigned int num_symbols=500; // number of symbols to observe
float SNRdB = 30.0f; // signal-to-noise ratio [dB]
unsigned int hc_len=5; // channel filter length
unsigned int k=2; // matched filter samples/symbol
unsigned int m=3; // matched filter delay (symbols)
float beta=0.3f; // matched filter excess bandwidth factor
unsigned int p=3; // equalizer length (symbols, gr_len = 2*k*p+1)
float mu = 0.09f; // LMS learning rate
// modulation type/depth
modulation_scheme ms = LIQUID_MODEM_QPSK;
// plotting options
unsigned int nfft = 512; // fft size
float gnuplot_version = 4.2;
char filename_base[256] = "figures.gen/eqlms_cccf_blind";
int dopt;
while ((dopt = getopt(argc,argv,"hf:g:n:s:c:k:m:b:p:u:M:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'f': strncpy(filename_base,optarg,256); break;
case 'g': gnuplot_version = atoi(optarg); break;
case 'n': num_symbols = atoi(optarg); break;
case 's': SNRdB = atof(optarg); break;
case 'c': hc_len = atoi(optarg); break;
case 'k': k = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 'b': beta = atof(optarg); break;
case 'p': p = atoi(optarg); break;
case 'u': mu = atof(optarg); break;
case 'M':
ms = liquid_getopt_str2mod(optarg);
if (ms == LIQUID_MODEM_UNKNOWN) {
fprintf(stderr,"error: %s, unknown/unsupported modulation scheme '%s'\n", argv[0], optarg);
return 1;
}
break;
default:
exit(1);
}
}
// validate input
if (num_symbols == 0) {
fprintf(stderr,"error: %s, number of symbols must be greater than zero\n", argv[0]);
exit(1);
} else if (hc_len == 0) {
fprintf(stderr,"error: %s, channel must have at least 1 tap\n", argv[0]);
exit(1);
} else if (k < 2) {
fprintf(stderr,"error: %s, samples/symbol must be at least 2\n", argv[0]);
exit(1);
} else if (m == 0) {
fprintf(stderr,"error: %s, filter semi-length must be at least 1 symbol\n", argv[0]);
exit(1);
} else if (beta < 0.0f || beta > 1.0f) {
fprintf(stderr,"error: %s, filter excess bandwidth must be in [0,1]\n", argv[0]);
exit(1);
} else if (p == 0) {
fprintf(stderr,"error: %s, equalizer semi-length must be at least 1 symbol\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);
}
// set 'random' seed on options
srand( hc_len + p + nfft );
// derived values
unsigned int gt_len = 2*k*m+1; // matched filter length
unsigned int gr_len = 2*k*p+1; // equalizer filter length
unsigned int num_samples = k*num_symbols;
// bookkeeping variables
float complex sym_tx[num_symbols]; // transmitted data sequence
float complex x[num_samples]; // interpolated time series
float complex y[num_samples]; // channel output
float complex z[num_samples]; // equalized output
// least mean-squares (LMS) equalizer
float mse[num_symbols]; // equalizer mean-squared error
float complex gr[gr_len]; // equalizer filter coefficients
unsigned int i;
// generate matched filter response
float gtf[gt_len]; // matched filter response
liquid_firdes_rnyquist(LIQUID_RNYQUIST_RRC, k, m, beta, 0.0f, gtf);
// convert to complex coefficients
float complex gt[gt_len];
for (i=0; i<gt_len; i++)
gt[i] = gtf[i]; //+ 0.1f*(randnf() + _Complex_I*randnf());
// create interpolator
interp_cccf interp = interp_cccf_create(k, gt, gt_len);
// create the modem objects
modem mod = modem_create(ms);
modem demod = modem_create(ms);
unsigned int bps = modem_get_bps(mod);
unsigned int M = 1 << bps;
// generate channel impulse response, filter
#if 0
float complex hc[hc_len]; // channel filter coefficients
hc[0] = 1.0f;
for (i=1; i<hc_len; i++)
hc[i] = 0.09f*(randnf() + randnf()*_Complex_I);
#else
// use fixed channel
hc_len = 8;
float complex hc[hc_len]; // channel filter coefficients
hc[0] = 1.00000000+ 0.00000000*_Complex_I;
hc[1] = 0.08077553+ -0.00247592*_Complex_I;
hc[2] = 0.03625883+ -0.09219734*_Complex_I;
hc[3] = 0.05764082+ 0.03277601*_Complex_I;
hc[4] = -0.04773349+ -0.18766306*_Complex_I;
hc[5] = -0.00101735+ -0.00270737*_Complex_I;
hc[6] = -0.05796884+ -0.12665297*_Complex_I;
hc[7] = 0.03805391+ -0.07609370*_Complex_I;
#endif
firfilt_cccf fchannel = firfilt_cccf_create(hc, hc_len);
firfilt_cccf_print(fchannel);
// generate random symbols
for (i=0; i<num_symbols; i++)
modem_modulate(mod, rand()%M, &sym_tx[i]);
// interpolate
for (i=0; i<num_symbols; i++)
interp_cccf_execute(interp, sym_tx[i], &x[i*k]);
// push through channel
float nstd = powf(10.0f, -SNRdB/20.0f);
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;
}
// push through equalizers
float grf[gr_len];
liquid_firdes_rnyquist(LIQUID_RNYQUIST_RRC, k, p, beta, 0.0f, grf);
for (i=0; i<gr_len; i++) {
gr[i] = grf[i] / (float)k;
}
// create LMS equalizer
eqlms_cccf eq = eqlms_cccf_create(gr, gr_len);
eqlms_cccf_set_bw(eq, mu);
// filtered error vector magnitude (emperical MSE)
//float zeta=0.05f; // smoothing factor (small zeta -> smooth MSE)
float complex d_hat = 0.0f;
unsigned int num_symbols_rx=0;
for (i=0; i<num_samples; i++) {
// push samples into equalizers
eqlms_cccf_push(eq, y[i]);
// compute outputs
eqlms_cccf_execute(eq, &d_hat);
// store outputs
z[i] = d_hat;
// check to see if buffer is full
if ( i < gr_len) continue;
// decimate by k
if ( (i%k) != 0 ) continue;
// estimate transmitted signal
unsigned int sym_out; // output symbol
float complex d_prime; // estimated input sample
// LMS
modem_demodulate(demod, d_hat, &sym_out);
modem_get_demodulator_sample(demod, &d_prime);
// update equalizers
eqlms_cccf_step(eq, d_prime, d_hat);
#if 0
// update filtered evm estimate
float evm = crealf( (d_prime-d_hat)*conjf(d_prime-d_hat) );
if (num_symbols_rx == 0) {
mse[num_symbols_rx] = evm;
} else {
mse[num_symbols_rx] = mse[num_symbols_rx-1]*(1-zeta) + evm*zeta;
}
#else
// compute ISI for entire system
eqlms_cccf_get_weights(eq, gr);
mse[num_symbols_rx] = eqlms_cccf_isi(k, gt, gt_len, hc, hc_len, gr, gr_len);
#endif
// print filtered evm (emperical rms error)
if ( ((num_symbols_rx+1)%100) == 0 )
printf("%4u : mse = %12.8f dB\n",
num_symbols_rx+1,
20*log10f(mse[num_symbols_rx]));
// increment output symbol counter
num_symbols_rx++;
}
// get equalizer weights
eqlms_cccf_get_weights(eq, gr);
// destroy objects
eqlms_cccf_destroy(eq);
interp_cccf_destroy(interp);
firfilt_cccf_destroy(fchannel);
modem_destroy(mod);
modem_destroy(demod);
//
// 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 50%%',\\\n", LIQUID_DOC_COLOR_GRAY);
fprintf(fid," '-' using 1:2 with points pointtype 7 pointsize 0.7 linecolor rgb '%s' title 'last 50%%'\n", LIQUID_DOC_COLOR_RED);
// first half of symbols
for (i=2*p; i<num_symbols/2; i+=k)
fprintf(fid," %12.4e %12.4e\n", crealf(y[i]), cimagf(y[i]));
fprintf(fid,"e\n");
// second half of symbols
for ( ; i<num_symbols; i+=k)
fprintf(fid," %12.4e %12.4e\n", crealf(z[i]), cimagf(z[i]));
fprintf(fid,"e\n");
fclose(fid);
printf("results written to '%s'\n", filename);
//
// mse : mean-squared error
//
strncpy(filename, filename_base, 256);
strcat(filename, "_mse.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 0.3\n");
fprintf(fid,"set xrange [0:%u];\n", num_symbols);
fprintf(fid,"set yrange [1e-3:1e-1];\n");
fprintf(fid,"set format y '10^{%%L}'\n");
fprintf(fid,"set log y\n");
fprintf(fid,"set xlabel 'symbol index'\n");
fprintf(fid,"set ylabel 'mean-squared error'\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 lines linewidth 4 linetype 1 linecolor rgb '%s' title 'LMS MSE'\n", LIQUID_DOC_COLOR_RED);
// LMS
for (i=0; i<num_symbols_rx; i++)
fprintf(fid," %4u %16.8e\n", i, mse[i]);
fprintf(fid,"e\n");
fclose(fid);
printf("results written to '%s'\n", filename);
//
// psd : power spectral density
//
// scale transmit filter appropriately
for (i=0; i<gt_len; i++) gt[i] /= (float)k;
float complex Gt[nfft]; // transmit matched filter
float complex Hc[nfft]; // channel response
float complex Gr[nfft]; // equalizer response
liquid_doc_compute_psdcf(gt, gt_len, Gt, nfft, LIQUID_DOC_PSDWINDOW_NONE, 0);
liquid_doc_compute_psdcf(hc, hc_len, Hc, nfft, LIQUID_DOC_PSDWINDOW_NONE, 0);
liquid_doc_compute_psdcf(gr, gr_len, Gr, nfft, LIQUID_DOC_PSDWINDOW_NONE, 0);
fft_shift(Gt, nfft);
fft_shift(Hc, nfft);
fft_shift(Gr, nfft);
float freq[nfft];
for (i=0; i<nfft; i++)
freq[i] = (float)(i) / (float)nfft - 0.5f;
strncpy(filename, filename_base, 256);
strcat(filename, "_freq.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 0.6\n");
fprintf(fid,"set xrange [-0.5:0.5];\n");
fprintf(fid,"set yrange [-10:6]\n");
fprintf(fid,"set xlabel 'Normalized Frequency'\n");
fprintf(fid,"set ylabel 'Power Spectral Density [dB]'\n");
fprintf(fid,"set key top right nobox\n");
fprintf(fid,"set grid xtics ytics\n");
fprintf(fid,"set grid linetype 1 linecolor rgb '%s' lw 1\n",LIQUID_DOC_COLOR_GRID);
fprintf(fid,"plot '-' using 1:2 with lines linetype 1 linewidth 1.5 linecolor rgb '%s' title 'transmit',\\\n", LIQUID_DOC_COLOR_GRAY);
fprintf(fid," '-' using 1:2 with lines linetype 1 linewidth 1.5 linecolor rgb '%s' title 'channel',\\\n", LIQUID_DOC_COLOR_RED);
fprintf(fid," '-' using 1:2 with lines linetype 1 linewidth 1.5 linecolor rgb '%s' title 'equalizer',\\\n", LIQUID_DOC_COLOR_GREEN);
fprintf(fid," '-' using 1:2 with lines linetype 1 linewidth 4.0 linecolor rgb '%s' title 'composite',\\\n", LIQUID_DOC_COLOR_BLUE);
fprintf(fid," '-' using 1:2 with points pointtype 7 pointsize 0.6 linecolor rgb '%s' notitle\n", LIQUID_DOC_COLOR_BLUE);
// received signal
for (i=0; i<nfft; i++)
fprintf(fid,"%12.8f %12.4e\n", freq[i], 20*log10f(cabsf(Gt[i])) );
fprintf(fid,"e\n");
// channel
for (i=0; i<nfft; i++)
fprintf(fid,"%12.8f %12.4e\n", freq[i], 20*log10f(cabsf(Hc[i])) );
fprintf(fid,"e\n");
// equalizer
for (i=0; i<nfft; i++)
fprintf(fid,"%12.8f %12.4e\n", freq[i], 20*log10f(cabsf(Gr[i])) );
fprintf(fid,"e\n");
// composite
for (i=0; i<nfft; i++)
fprintf(fid,"%12.8f %12.4e\n", freq[i], 20*log10f( cabsf(Gt[i])*cabsf(Hc[i])*cabsf(Gr[i])) );
fprintf(fid,"e\n");
// composite
fprintf(fid,"%12.8f %12.4e\n", -0.5f/(float)k, 20*log10f(0.5f));
fprintf(fid,"%12.8f %12.4e\n", 0.5f/(float)k, 20*log10f(0.5f));
fprintf(fid,"e\n");
fclose(fid);
printf("results written to '%s'\n", filename);
//
// time...
//
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; i++)
fprintf(fid,"%12.8f %12.4e\n", (float)i/(float)k, crealf(z[i]));
fprintf(fid,"e\n");
//
for (i=0; i<num_samples; i+=k)
fprintf(fid,"%12.8f %12.4e\n", (float)i/(float)k, 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; i++)
fprintf(fid,"%12.8f %12.4e\n", (float)i/(float)k, cimagf(z[i]));
fprintf(fid,"e\n");
//
for (i=0; i<num_samples; i+=k)
fprintf(fid,"%12.8f %12.4e\n", (float)i/(float)k, cimagf(z[i]));
fprintf(fid,"e\n");
fprintf(fid,"unset multiplot\n");
// close output file
fclose(fid);
printf("results written to '%s'\n", filename);
return 0;
}
int main(int argc, char*argv[]) {
srand( time(NULL) );
// options
int verbose = 1; // verbose output flag
float phi_max_abs = M_PI/4.0f; // absolute maximum phase offset
unsigned int num_phi = 21; // number of phase steps
unsigned int num_trials = 1000; // number of trials
float SNRdB = 12.0f; // signal-to-noise ratio [dB]
modulation_scheme ms = LIQUID_MODEM_QPSK;
char filename[256] = ""; // output filename
int dopt;
while ((dopt = getopt(argc,argv,"uhvqn:t:s:P:m:o:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'v': verbose = 1; break;
case 'q': verbose = 0; break;
case 'n': num_phi = atoi(optarg); break;
case 't': num_trials = atoi(optarg); break;
case 's': SNRdB = atof(optarg); break;
case 'P': phi_max_abs = atof(optarg); break;
case 'm':
ms = liquid_getopt_str2mod(optarg);
if (ms == LIQUID_MODEM_UNKNOWN) {
fprintf(stderr,"error: %s, unknown/unsupported modulation scheme \"%s\"\n", argv[0], optarg);
return 1;
}
break;
case 'o': strncpy(filename,optarg,255); break;
default:
exit(1);
}
}
// validate input
if (phi_max_abs <= 0.0f) {
fprintf(stderr,"error: %s, maximum absolute phase offset must be greater than 0\n", argv[0]);
exit(1);
} else if (num_phi < 3) {
fprintf(stderr,"error: %s, number of phase steps must be at least 3\n", argv[0]);
exit(1);
fprintf(stderr,"error: %s, number of trials must be greater than 0\n", argv[0]);
exit(1);
}
unsigned int bps = modulation_types[ms].bps;
// generate filenames
if ( strcmp(filename,"")==0 )
sprintf(filename,"figures.gen/modem_phase_error_%s%u.dat", modulation_types[ms].name, 1<<bps);
// derived values
float phi_min = 0.0f; //phi_max_abs;
float phi_max = phi_max_abs;
float phi_step = (phi_max - phi_min) / (float)(num_phi-1);
float nstd = powf(10.0f, -SNRdB/20.0f);
// arrays
float phi_hat_mean[num_phi]; // phase error estimate
float phi_hat_mean_smooth[num_phi]; // phase error estimate (smoothed)
// create modulator/demodulator
modem mod = modem_create(ms);
modem demod = modem_create(ms);
unsigned int M = 1 << bps;
//
unsigned int i;
unsigned int sym_in;
unsigned int sym_out;
unsigned int n=0; // trials counter
float complex x;
float phi_hat;
float phi=0.0f;
for (i=0; i<num_phi; i++) {
phi = phi_min + i*phi_step;
phi_hat_mean[i] = 0.0f;
// reset number of trials
n = 0;
do {
for (sym_in=0; sym_in<M; sym_in++) {
// modulate
modem_modulate(mod, sym_in, &x);
// channel (phase offset)
x *= cexpf(_Complex_I*phi);
x += nstd * (randnf() + _Complex_I*randnf()) * M_SQRT1_2;
// demodulate
modem_demodulate(demod, x, &sym_out);
// get error
phi_hat = modem_get_demodulator_phase_error(demod);
// accumulate average
phi_hat_mean[i] += phi_hat;
}
n += M;
} while (n < num_trials);
// scale by bps^2
//phi_hat_mean[i] *= bps*bps;
// normalize mean by number of trials
phi_hat_mean[i] /= (float) (n);
// print results
if (verbose)
printf("%6u / %6u : phi=%12.8f, phi-hat=%12.8f\n",
i+1, num_phi, phi, phi_hat_mean[i]);
}
// compute smoothed curve
float phi_hat_tmp[num_phi];
memmove(phi_hat_mean_smooth, phi_hat_mean, num_phi*sizeof(float));
unsigned int j;
for (j=0; j<5; j++) {
memmove(phi_hat_tmp, phi_hat_mean_smooth, num_phi*sizeof(float));
for (i=0; i<num_phi; i++) {
if (i==0 || i == num_phi-1) {
phi_hat_mean_smooth[i] = phi_hat_tmp[i];
} else {
phi_hat_mean_smooth[i] = 0.20f*phi_hat_tmp[i-1] +
0.60f*phi_hat_tmp[i ] +
0.20f*phi_hat_tmp[i+1];
}
}
}
// destroy objects
modem_destroy(mod);
modem_destroy(demod);
//
// export output file
//
FILE * fid = fopen(filename,"w");
if (!fid) {
fprintf(stderr,"error: %s, cannot open '%s' for writing\n", argv[0], filename);
exit(1);
}
fprintf(fid, "# %s : auto-generated file\n", filename);
fprintf(fid, "# \n");
// low SNR
fprintf(fid, "# %12s %12s %12s\n", "phi", "phi-hat", "phi-hat-smooth");
for (i=0; i<num_phi; i++) {
phi = phi_min + i*phi_step;
fprintf(fid," %12.8f %12.8f %12.8f\n", phi, phi_hat_mean[i], phi_hat_mean_smooth[i]);
}
fclose(fid);
if (verbose)
printf("results written to '%s'\n", filename);
return 0;
}
int main(int argc, char*argv[])
{
srand(time(NULL));
// options
unsigned int M = 64; // number of subcarriers
unsigned int cp_len = 16; // cyclic prefix length
unsigned int taper_len = 0; // taper length
unsigned int num_symbols = 1000; // number of data symbols
modulation_scheme ms = LIQUID_MODEM_QPSK;
// get options
int dopt;
while((dopt = getopt(argc,argv,"hM:C:T:N:")) != EOF){
switch (dopt) {
case 'h': usage(); return 0;
case 'M': M = atoi(optarg); break;
case 'C': cp_len = atoi(optarg); break;
case 'T': taper_len = atoi(optarg); break;
case 'N': num_symbols = atoi(optarg); break;
default:
exit(1);
}
}
unsigned int i;
// derived values
unsigned int frame_len = M + cp_len;
// initialize subcarrier allocation
unsigned char p[M];
ofdmframe_init_default_sctype(M, p);
// create frame generator
ofdmframegen fg = ofdmframegen_create(M, cp_len, taper_len, p);
ofdmframegen_print(fg);
modem mod = modem_create(ms);
float complex X[M]; // channelized symbols
float complex buffer[frame_len];// output time series
float * PAPR = (float*) malloc(num_symbols*sizeof(float));
// histogram display
float xmin = -1.29f + 0.70f*log2f(M);
float xmax = 8.97f + 0.34f*log2f(M);
unsigned int num_bins = 30;
float bin_width = (xmax - xmin) / (num_bins);
unsigned int hist[num_bins];
for (i=0; i<num_bins; i++)
hist[i] = 0;
// modulate data symbols
unsigned int j;
unsigned int s;
float PAPR_min = 0.0f;
float PAPR_max = 0.0f;
float PAPR_mean = 0.0f;
for (i=0; i<num_symbols; i++) {
// data symbol
for (j=0; j<M; j++) {
s = modem_gen_rand_sym(mod);
modem_modulate(mod,s,&X[j]);
}
// generate symbol
ofdmframegen_writesymbol(fg, X, buffer);
#if 0
// preamble
if (i==0) ofdmframegen_write_S0a(fg, buffer); // S0 symbol (first)
else if (i==1) ofdmframegen_write_S0b(fg, buffer); // S0 symbol (second)
else if (i==2) ofdmframegen_write_S1( fg, buffer); // S1 symbol
#endif
// compute PAPR
PAPR[i] = ofdmframe_PAPR(buffer, frame_len);
// compute bin index
unsigned int index;
float ihat = num_bins * (PAPR[i] - xmin) / (xmax - xmin);
if (ihat < 0.0f) index = 0;
else index = (unsigned int)ihat;
if (index >= num_bins)
index = num_bins-1;
hist[index]++;
// save min/max PAPR values
if (i==0 || PAPR[i] < PAPR_min) PAPR_min = PAPR[i];
if (i==0 || PAPR[i] > PAPR_max) PAPR_max = PAPR[i];
PAPR_mean += PAPR[i];
}
PAPR_mean /= (float)num_symbols;
// destroy objects
ofdmframegen_destroy(fg);
modem_destroy(mod);
// print results to screen
// find max(hist)
unsigned int hist_max = 0;
for (i=0; i<num_bins; i++)
hist_max = hist[i] > hist_max ? hist[i] : hist_max;
printf("%8s : %6s [%6s]\n", "PAPR[dB]", "count", "prob.");
for (i=0; i<num_bins; i++) {
printf("%8.2f : %6u [%6.4f]", xmin + i*bin_width, hist[i], (float)hist[i] / (float)num_symbols);
unsigned int k;
unsigned int n = round(60 * (float)hist[i] / (float)hist_max);
for (k=0; k<n; k++)
printf("#");
printf("\n");
}
printf("\n");
printf("min PAPR: %12.4f dB\n", PAPR_min);
printf("max PAPR: %12.4f dB\n", PAPR_max);
printf("mean PAPR: %12.4f dB\n", PAPR_mean);
//
// export output file
//
// count subcarrier types
unsigned int M_data = 0;
unsigned int M_pilot = 0;
unsigned int M_null = 0;
ofdmframe_validate_sctype(p, M, &M_null, &M_pilot, &M_data);
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\n");
fprintf(fid,"M = %u;\n", M);
fprintf(fid,"M_data = %u;\n", M_data);
fprintf(fid,"M_pilot = %u;\n", M_pilot);
fprintf(fid,"M_null = %u;\n", M_null);
fprintf(fid,"cp_len = %u;\n", cp_len);
fprintf(fid,"num_symbols = %u;\n", num_symbols);
fprintf(fid,"PAPR = zeros(1,num_symbols);\n");
for (i=0; i<num_symbols; i++)
fprintf(fid," PAPR(%6u) = %12.4e;\n", i+1, PAPR[i]);
fprintf(fid,"\n");
fprintf(fid,"figure;\n");
fprintf(fid,"hist(PAPR,25);\n");
fprintf(fid,"\n");
fprintf(fid,"figure;\n");
fprintf(fid,"cdf = [(1:num_symbols)-0.5]/num_symbols;\n");
fprintf(fid,"semilogy(sort(PAPR),1-cdf);\n");
fprintf(fid,"xlabel('PAPR [dB]');\n");
fprintf(fid,"ylabel('Complementary CDF');\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
// free allocated array
free(PAPR);
printf("done.\n");
return 0;
}
int main(int argc, char*argv[])
{
// options
unsigned int bps=6; // bits per symbol
unsigned int n=1024; // number of data points to evaluate
int dopt;
while ((dopt = getopt(argc,argv,"uhp:")) != EOF) {
switch (dopt) {
case 'u':
case 'h': usage(); return 0;
case 'p': bps = atoi(optarg); break;
default:
exit(1);
}
}
// validate input
if (bps == 0) {
fprintf(stderr,"error: %s, bits/symbol must be greater than zero\n", argv[0]);
exit(1);
}
// derived values
unsigned int i;
unsigned int M = 1<<bps; // constellation size
// initialize constellation table
float complex constellation[M];
// initialize constellation (spiral)
for (i=0; i<M; i++) {
float r = (float)i / logf((float)M) + 4.0f;
float phi = (float)i / logf((float)M);
constellation[i] = r * cexpf(_Complex_I*phi);
}
// create mod/demod objects
modem mod = modem_create_arbitrary(constellation, M);
modem demod = modem_create_arbitrary(constellation, M);
modem_print(mod);
// run simulation
float complex x[n];
unsigned int num_errors = 0;
// run simple BER simulation
num_errors = 0;
unsigned int sym_in;
unsigned int sym_out;
for (i=0; i<n; i++) {
// generate and modulate random symbol
sym_in = modem_gen_rand_sym(mod);
modem_modulate(mod, sym_in, &x[i]);
// add noise
x[i] += 0.05 * randnf() * cexpf(_Complex_I*M_PI*randf());
// demodulate
modem_demodulate(demod, x[i], &sym_out);
// accumulate errors
num_errors += count_bit_errors(sym_in,sym_out);
}
printf("num bit errors: %4u / %4u\n", num_errors, bps*n);
// destroy modem objects
modem_destroy(mod);
modem_destroy(demod);
//
// export output file
//
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,"bps = %u;\n", bps);
fprintf(fid,"M = %u;\n", M);
for (i=0; i<n; i++) {
fprintf(fid,"x(%3u) = %12.4e + j*%12.4e;\n", i+1,
crealf(x[i]),
cimagf(x[i]));
}
// plot results
fprintf(fid,"figure;\n");
fprintf(fid,"plot(x,'x','MarkerSize',1);\n");
fprintf(fid,"xlabel('in-phase');\n");
fprintf(fid,"ylabel('quadrature phase');\n");
fprintf(fid,"title(['Arbitrary ' num2str(M) '-QAM']);\n");
fprintf(fid,"axis([-1 1 -1 1]*1.9);\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("results written to '%s'\n", OUTPUT_FILENAME);
printf("done.\n");
return 0;
}
// Helper function to keep code base small
void modem_test_demodstats(modulation_scheme _ms)
{
// generate mod/demod
modem mod = modem_create(_ms);
modem demod = modem_create(_ms);
// run the test
unsigned int i, s, M = 1 << modem_get_bps(mod);
float complex x;
float complex x_hat; // rotated symbol
float demodstats;
float phi = 0.01f;
for (i=0; i<M; i++) {
// reset modem objects
modem_reset(mod);
modem_reset(demod);
// modulate symbol
modem_modulate(mod, i, &x);
// ignore rare condition where modulated symbol is (0,0)
// (e.g. APSK-8)
if (cabsf(x) < 1e-3f) continue;
// add phase offsets
x_hat = x * cexpf( phi*_Complex_I);
// demod positive phase signal, and ensure demodulator
// maps to appropriate symbol
modem_demodulate(demod, x_hat, &s);
if (s != i)
AUTOTEST_WARN("modem_test_demodstats(), output symbol does not match");
demodstats = modem_get_demodulator_phase_error(demod);
CONTEND_EXPRESSION(demodstats > 0.0f);
}
// repeat with negative phase error
for (i=0; i<M; i++) {
// reset modem objects
modem_reset(mod);
modem_reset(demod);
// modulate symbol
modem_modulate(mod, i, &x);
// ignore rare condition where modulated symbol is (0,0)
// (e.g. APSK-8)
if (cabsf(x) < 1e-3f) continue;
// add phase offsets
x_hat = x * cexpf(-phi*_Complex_I);
// demod positive phase signal, and ensure demodulator
// maps to appropriate symbol
modem_demodulate(demod, x_hat, &s);
if (s != i)
AUTOTEST_WARN("modem_test_demodstats(), output symbol does not match");
demodstats = modem_get_demodulator_phase_error(demod);
CONTEND_EXPRESSION(demodstats < 0.0f);
}
// clean up allocated objects up
modem_destroy(mod);
modem_destroy(demod);
}
int main() {
// options
unsigned int num_channels=6; // for now, must be even number
unsigned int num_symbols=32; // num symbols
unsigned int m=2; // ofdm/oqam symbol delay
float beta = 0.99f; // excess bandwidth factor
float dt = 0.0f; // timing offset (fractional sample)
modulation_scheme ms = LIQUID_MODEM_QAM4; // modulation scheme
// number of frames (compensate for filter delay)
unsigned int num_frames = num_symbols + 2*m;
unsigned int num_samples = num_channels * num_frames;
// create synthesizer/analyzer objects
ofdmoqam cs = ofdmoqam_create(num_channels, m, beta, dt, LIQUID_SYNTHESIZER,0);
ofdmoqam ca = ofdmoqam_create(num_channels, m, beta, dt, LIQUID_ANALYZER,0);
// modem
modem mod = modem_create(ms);
FILE*fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s: auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\nclose all;\n\n");
fprintf(fid,"num_channels=%u;\n", num_channels);
fprintf(fid,"num_symbols=%u;\n", num_symbols);
fprintf(fid,"num_frames = %u;\n", num_frames);
fprintf(fid,"num_samples = num_frames*num_channels;\n");
fprintf(fid,"X = zeros(%u,%u);\n", num_channels, num_frames);
fprintf(fid,"y = zeros(1,%u);\n", num_samples);
fprintf(fid,"Y = zeros(%u,%u);\n", num_channels, num_frames);
unsigned int i, j, n=0;
unsigned int s[num_symbols][num_channels];
float complex X[num_channels]; // channelized symbols
float complex y[num_channels]; // interpolated time-domain samples
float complex Y[num_channels]; // received symbols
// generate random symbols
for (i=0; i<num_symbols; i++) {
for (j=0; j<num_channels; j++) {
s[i][j] = modem_gen_rand_sym(mod);
}
}
for (i=0; i<num_frames; i++) {
// generate frame data
for (j=0; j<num_channels; j++) {
if (i<num_symbols) {
modem_modulate(mod,s[i][j],&X[j]);
} else {
X[j] = 0.0f;
}
}
// execute synthesyzer
ofdmoqam_execute(cs, X, y);
// channel
// execute analyzer
ofdmoqam_execute(ca, y, Y);
// write output to file
for (j=0; j<num_channels; j++) {
// frequency data
fprintf(fid,"X(%4u,%4u) = %12.4e + j*%12.4e;\n", j+1, i+1, crealf(X[j]), cimagf(X[j]));
// time data
fprintf(fid,"y(%4u) = %12.4e + j*%12.4e;\n", n+1, crealf(y[j]), cimag(y[j]));
// received data
fprintf(fid,"Y(%4u,%4u) = %12.4e + j*%12.4e;\n", j+1, i+1, crealf(Y[j]), cimagf(Y[j]));
n++;
}
}
// print results
fprintf(fid,"\n\n");
fprintf(fid,"X0 = X(:,1:%u);\n", num_symbols);
fprintf(fid,"Y0 = Y(:,%u:%u);\n", 2*m+1, num_symbols + 2*m);
fprintf(fid,"for i=1:num_channels,\n");
fprintf(fid," figure;\n");
fprintf(fid," subplot(2,1,1);\n");
fprintf(fid," plot(1:num_symbols,real(X0(i,:)),'-x',1:num_symbols,real(Y0(i,:)),'-x');\n");
fprintf(fid," ylabel('Re');\n");
fprintf(fid," title(['channel ' num2str(i-1)]);\n");
fprintf(fid," subplot(2,1,2);\n");
fprintf(fid," plot(1:num_symbols,imag(X0(i,:)),'-x',1:num_symbols,imag(Y0(i,:)),'-x');\n");
fprintf(fid," ylabel('Im');\n");
fprintf(fid," pause(0.2);\n");
fprintf(fid,"end;\n");
// print results
fprintf(fid,"\n\n");
fprintf(fid,"t = 0:(num_samples-1);\n");
fprintf(fid," figure;\n");
fprintf(fid," plot(t,real(y),'-', t,imag(y),'-');\n");
fprintf(fid," xlabel('time');\n");
fprintf(fid," ylabel('signal');\n");
fclose(fid);
printf("results written to %s\n", OUTPUT_FILENAME);
// destroy objects
ofdmoqam_destroy(cs);
ofdmoqam_destroy(ca);
modem_destroy(mod);
printf("done.\n");
return 0;
}
