//
// Test AC gain control
//
void autotest_agc_crcf_ac_gain_control()
{
// set paramaters
float gamma = 0.1f; // nominal signal level
float bt = 0.1f; // bandwidth-time product
float tol = 0.001f; // error tolerance
float dphi = 0.1f; // NCO frequency
// create AGC object and initialize
agc_crcf q = agc_crcf_create();
agc_crcf_set_bandwidth(q, bt);
unsigned int i;
float complex x;
float complex y;
for (i=0; i<256; i++) {
x = gamma * cexpf(_Complex_I*i*dphi);
agc_crcf_execute(q, x, &y);
}
if (liquid_autotest_verbose)
printf("gamma : %12.8f, rssi : %12.8f\n", gamma, agc_crcf_get_signal_level(q));
// Check results
CONTEND_DELTA( agc_crcf_get_gain(q), 1.0f/gamma, tol);
// destroy AGC object
agc_crcf_destroy(q);
}
// helper function to keep code base small
void benchmark_agc_crcf(struct rusage * _start,
struct rusage * _finish,
unsigned long int * _num_iterations)
{
unsigned int i;
// initialize AGC object
agc_crcf q = agc_crcf_create();
agc_crcf_set_bandwidth(q,0.05f);
float complex x = 1e-6f; // input sample
float complex y; // output sample
getrusage(RUSAGE_SELF, _start);
for (i=0; i<(*_num_iterations); i++) {
agc_crcf_execute(q, x, &y);
agc_crcf_execute(q, x, &y);
agc_crcf_execute(q, x, &y);
agc_crcf_execute(q, x, &y);
agc_crcf_execute(q, x, &y);
agc_crcf_execute(q, x, &y);
agc_crcf_execute(q, x, &y);
agc_crcf_execute(q, x, &y);
}
getrusage(RUSAGE_SELF, _finish);
*_num_iterations *= 8;
// destroy object
agc_crcf_destroy(q);
}
//
// Test DC gain control
//
void autotest_agc_crcf_dc_gain_control()
{
// set paramaters
float gamma = 0.1f; // nominal signal level
float bt = 0.1f; // bandwidth-time product
float tol = 0.001f; // error tolerance
// create AGC object and initialize
agc_crcf q = agc_crcf_create();
agc_crcf_set_bandwidth(q, bt);
unsigned int i;
float complex x = gamma; // input sample
float complex y; // output sample
for (i=0; i<256; i++)
agc_crcf_execute(q, x, &y);
// Check results
CONTEND_DELTA( crealf(y), 1.0f, tol );
CONTEND_DELTA( cimagf(y), 0.0f, tol );
CONTEND_DELTA( agc_crcf_get_gain(q), 1.0f/gamma, tol );
// destroy AGC object
agc_crcf_destroy(q);
}
void wlanframesync_debug_enable(wlanframesync _q)
{
// create debugging objects if necessary
#if DEBUG_WLANFRAMESYNC
// agc, rssi
if (_q->agc_rx == NULL)
_q->agc_rx = agc_crcf_create();
agc_crcf_set_bandwidth(_q->agc_rx, 1e-2f);
agc_crcf_set_gain_limits(_q->agc_rx, 1.0f, 1e7f);
if (_q->debug_x == NULL)
_q->debug_x = windowcf_create(DEBUG_WLANFRAMESYNC_BUFFER_LEN);
if (_q->debug_rssi == NULL)
_q->debug_rssi = windowf_create(DEBUG_WLANFRAMESYNC_BUFFER_LEN);
if (_q->debug_framesyms == NULL)
_q->debug_framesyms = windowcf_create(DEBUG_WLANFRAMESYNC_BUFFER_LEN);
_q->debug_enabled = 1;
#else
fprintf(stderr,"wlanframesync_debug_enable(): compile-time debugging disabled\n");
#endif
}
//
// Test RSSI on sinusoidal input
//
void autotest_agc_crcf_rssi_sinusoid()
{
// set paramaters
float gamma = 0.3f; // nominal signal level
float bt = 0.05f; // agc bandwidth
float tol = 0.001f; // error tolerance
// signal properties
float dphi = 0.1f; // signal frequency
// create AGC object and initialize
agc_crcf q = agc_crcf_create();
agc_crcf_set_bandwidth(q, bt);
unsigned int i;
float complex x, y;
for (i=0; i<512; i++) {
// generate sample (complex sinusoid)
x = gamma * cexpf(_Complex_I*dphi*i);
// execute agc
agc_crcf_execute(q, x, &y);
}
// get received signal strength indication
float rssi = agc_crcf_get_signal_level(q);
if (liquid_autotest_verbose)
printf("gamma : %12.8f, rssi : %12.8f\n", gamma, rssi);
// Check results
CONTEND_DELTA( rssi, gamma, tol );
// destroy agc object
agc_crcf_destroy(q);
}
//
// Test RSSI on noise input
//
void autotest_agc_crcf_rssi_noise()
{
// set paramaters
float gamma = -30.0f; // nominal signal level [dB]
float bt = 0.01f; // agc bandwidth
float tol = 0.2f; // error tolerance [dB]
// signal properties
float nstd = powf(10.0f, gamma/20);
// create AGC object and initialize
agc_crcf q = agc_crcf_create();
agc_crcf_set_bandwidth(q, bt);
unsigned int i;
float complex x, y;
for (i=0; i<2000; i++) {
// generate sample (circular complex noise)
x = nstd*(randnf() + _Complex_I*randnf())*M_SQRT1_2;
// execute agc
agc_crcf_execute(q, x, &y);
}
// get received signal strength indication
float rssi = agc_crcf_get_rssi(q);
if (liquid_autotest_verbose)
printf("gamma : %12.8f, rssi : %12.8f\n", gamma, rssi);
// Check results
CONTEND_DELTA( rssi, gamma, tol );
// destroy agc object
agc_crcf_destroy(q);
}
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;
}
ofdmoqamframe64sync ofdmoqamframe64sync_create(unsigned int _m,
float _beta,
ofdmoqamframe64sync_callback _callback,
void * _userdata)
{
ofdmoqamframe64sync q = (ofdmoqamframe64sync) malloc(sizeof(struct ofdmoqamframe64sync_s));
q->num_subcarriers = 64;
// validate input
if (_m < 1) {
fprintf(stderr,"error: ofdmoqamframe64sync_create(), filter delay must be > 0\n");
exit(1);
} else if (_beta < 0.0f) {
fprintf(stderr,"error: ofdmoqamframe64sync_create(), filter excess bandwidth must be > 0\n");
exit(1);
}
q->m = _m;
q->beta = _beta;
// synchronizer parameters
q->rxx_thresh = 0.60f; // auto-correlation threshold
q->rxy_thresh = 0.60f; // cross-correlation threshold
q->zeta = 64.0f/sqrtf(52.0f); // scaling factor
// create analysis filter banks
q->ca0 = firpfbch_create(q->num_subcarriers, q->m, q->beta, 0.0f /*dt*/,FIRPFBCH_ROOTNYQUIST,0/*gradient*/);
q->ca1 = firpfbch_create(q->num_subcarriers, q->m, q->beta, 0.0f /*dt*/,FIRPFBCH_ROOTNYQUIST,0/*gradient*/);
q->X0 = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
q->X1 = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
q->Y0 = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
q->Y1 = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
// allocate memory for PLCP arrays
q->S0 = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
q->S1 = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
q->S2 = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
ofdmoqamframe64_init_S0(q->S0);
ofdmoqamframe64_init_S1(q->S1);
ofdmoqamframe64_init_S2(q->S2);
unsigned int i;
for (i=0; i<q->num_subcarriers; i++) {
q->S0[i] *= q->zeta;
q->S1[i] *= q->zeta;
q->S2[i] *= q->zeta;
}
q->S1a = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
q->S1b = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
// set pilot sequence
q->ms_pilot = msequence_create_default(8);
q->x_phase[0] = -21.0f;
q->x_phase[1] = -7.0f;
q->x_phase[2] = 7.0f;
q->x_phase[3] = 21.0f;
// create NCO for pilots
q->nco_pilot = nco_crcf_create(LIQUID_VCO);
q->pll_pilot = pll_create();
pll_set_bandwidth(q->pll_pilot,0.01f);
pll_set_damping_factor(q->pll_pilot,4.0f);
// create agc | signal detection object
q->sigdet = agc_crcf_create();
agc_crcf_set_bandwidth(q->sigdet,0.1f);
// create NCO for CFO compensation
q->nco_rx = nco_crcf_create(LIQUID_VCO);
// create auto-correlator objects
q->autocorr_length = OFDMOQAMFRAME64SYNC_AUTOCORR_LEN;
q->autocorr_delay = q->num_subcarriers / 4;
q->autocorr = autocorr_cccf_create(q->autocorr_length, q->autocorr_delay);
// create cross-correlator object
q->hxy = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
ofdmoqam cs = ofdmoqam_create(q->num_subcarriers,q->m,q->beta,
0.0f, // dt
OFDMOQAM_SYNTHESIZER,
0); // gradient
for (i=0; i<2*(q->m); i++)
ofdmoqam_execute(cs,q->S1,q->hxy);
// time reverse, complex conjugate (same as fftshift for
// this particular sequence)
memmove(q->X0, q->hxy, 64*sizeof(float complex));
for (i=0; i<64; i++)
q->hxy[i] = conjf(q->X0[64-i-1]);
// fftshift
//fft_shift(q->hxy,64);
q->crosscorr = firfilt_cccf_create(q->hxy, q->num_subcarriers);
ofdmoqam_destroy(cs);
// input buffer
q->input_buffer = windowcf_create((q->num_subcarriers));
// gain
q->g = 1.0f;
q->G0 = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
q->G1 = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
q->G = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
q->data = (float complex*) malloc((q->num_subcarriers)*sizeof(float complex));
// reset object
ofdmoqamframe64sync_reset(q);
#if DEBUG_OFDMOQAMFRAME64SYNC
q->debug_x = windowcf_create(DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN);
q->debug_rxx= windowcf_create(DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN);
q->debug_rxy= windowcf_create(DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN);
q->debug_framesyms= windowcf_create(DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN);
q->debug_pilotphase= windowf_create(DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN);
q->debug_pilotphase_hat= windowf_create(DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN);
q->debug_rssi= windowf_create(DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN);
#endif
q->callback = _callback;
q->userdata = _userdata;
return q;
}
