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 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;
}
}
// 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;
}
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() {
// 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;
}
// 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 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;
}
