// Helper function to keep code base small
void window_read_bench(struct rusage *_start,
struct rusage *_finish,
unsigned long int *_num_iterations,
unsigned int _n)
{
// normalize number of iterations
if (*_num_iterations < 1) *_num_iterations = 1;
// initialize port
windowcf w = windowcf_create(_n);
unsigned long int i;
float complex * r;
// start trials:
// write to buffer, read from buffer
getrusage(RUSAGE_SELF, _start);
for (i=0; i<(*_num_iterations); i++) {
windowcf_push(w,1.0f); windowcf_read(w, &r);
windowcf_push(w,1.0f); windowcf_read(w, &r);
windowcf_push(w,1.0f); windowcf_read(w, &r);
windowcf_push(w,1.0f); windowcf_read(w, &r);
}
getrusage(RUSAGE_SELF, _finish);
*_num_iterations *= 4;
windowcf_destroy(w);
}
// frame detection
void wlanframesync_execute_rxshort0(wlanframesync _q)
{
_q->timer++;
if (_q->timer < 16)
return;
// reset timer
_q->timer = 0;
// read contents of input buffer
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
// re-estimate S0 gain
wlanframesync_estimate_gain_S0(_q, &rc[16], _q->G0a);
float complex s_hat;
wlanframesync_S0_metrics(_q, _q->G0a, &s_hat);
//float g = agc_crcf_get_gain(_q->agc_rx);
s_hat *= _q->g0;
// save first 'short' symbol statistic
_q->s0a_hat = s_hat;
#if DEBUG_WLANFRAMESYNC_PRINT
float tau_hat = cargf(s_hat) * 16.0f / (2*M_PI);
printf("********** S0[a] received ************\n");
printf(" s_hat : %12.8f <%12.8f>\n", cabsf(s_hat), cargf(s_hat));
printf(" tau_hat : %12.8f\n", tau_hat);
#endif
_q->state = WLANFRAMESYNC_STATE_RXSHORT1;
}
void ofdmoqamframe64sync_execute_plcplong1(ofdmoqamframe64sync _q, float complex _x)
{
// cross-correlator
float complex rxy;
firfilt_cccf_push(_q->crosscorr, _x);
firfilt_cccf_execute(_q->crosscorr, &rxy);
rxy *= _q->g;
#if DEBUG_OFDMOQAMFRAME64SYNC
windowcf_push(_q->debug_rxy, rxy);
#endif
_q->timer++;
if (_q->timer < _q->num_subcarriers-8) {
return;
} else if (_q->timer > _q->num_subcarriers+8) {
#if DEBUG_OFDMOQAMFRAME64SYNC_PRINT
printf("warning: ofdmoqamframe64sync could not find second PLCP long sequence; resetting synchronizer\n");
#endif
ofdmoqamframe64sync_reset(_q);
return;
}
if (cabsf(rxy) > 0.7f*(_q->rxy_thresh)*(_q->num_subcarriers)) {
#if DEBUG_OFDMOQAMFRAME64SYNC_PRINT
printf("rxy[1] : %12.8f at input[%3u]\n", cabsf(rxy), _q->num_samples);
#endif
//
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
memmove(_q->S1b, rc, 64*sizeof(float complex));
// estimate frequency offset
float complex rxy_hat=0.0f;
unsigned int j;
for (j=0; j<64; j++) {
rxy_hat += _q->S1a[j] * conjf(_q->S1b[j]) * hamming(j,64);
}
float nu_hat1 = -cargf(rxy_hat);
if (nu_hat1 > M_PI) nu_hat1 -= 2.0f*M_PI;
if (nu_hat1 < -M_PI) nu_hat1 += 2.0f*M_PI;
nu_hat1 /= 64.0f;
#if DEBUG_OFDMOQAMFRAME64SYNC_PRINT
printf("nu_hat[0] = %12.8f\n", _q->nu_hat);
printf("nu_hat[1] = %12.8f\n", nu_hat1);
#endif
nco_crcf_adjust_frequency(_q->nco_rx, nu_hat1);
/*
printf("exiting prematurely\n");
ofdmoqamframe64sync_destroy(_q);
exit(1);
*/
_q->state = OFDMOQAMFRAME64SYNC_STATE_RXSYMBOLS;
}
}
// frame detection
void wlanframesync_execute_rxshort1(wlanframesync _q)
{
_q->timer++;
if (_q->timer < 16)
return;
// reset timer
_q->timer = 0;
// read contents of input buffer
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
// estimate S0 gain
wlanframesync_estimate_gain_S0(_q, &rc[16], _q->G0b);
float complex s_hat;
wlanframesync_S0_metrics(_q, _q->G0b, &s_hat);
//float g = agc_crcf_get_gain(_q->agc_rx);
s_hat *= _q->g0;
// save second 'short' symbol statistic
_q->s0b_hat = s_hat;
#if DEBUG_WLANFRAMESYNC_PRINT
float tau_hat = cargf(s_hat) * 16.0f / (2*M_PI);
printf("********** S0[b] received ************\n");
printf(" s_hat : %12.8f <%12.8f>\n", cabsf(s_hat), cargf(s_hat));
printf(" tau_hat : %12.8f\n", tau_hat);
// new timing offset estimate
tau_hat = cargf(_q->s0a_hat + _q->s0b_hat) * 16.0f / (2*M_PI);
printf(" tau_hat * : %12.8f\n", tau_hat);
#endif
#if 0
// compute carrier frequency offset estimate using ML method
float complex t0 = 0.0f;
for (i=0; i<48; i++) {
t0 += conjf(rc[i]) * wlanframe_s0[i] *
rc[i+16] * conjf(wlanframe_s0[i+16]);
}
float nu_hat = cargf(t0) / (float)(_q->M2);
#else
// compute carrier frequency offset estimate using freq. domain method
float nu_hat = wlanframesync_estimate_cfo_S0(_q->G0a, _q->G0b);
#endif
// set NCO frequency
nco_crcf_set_frequency(_q->nco_rx, nu_hat);
#if DEBUG_WLANFRAMESYNC_PRINT
printf(" nu_hat[0]: %12.8f\n", nu_hat);
#endif
// set state
_q->state = WLANFRAMESYNC_STATE_RXLONG0;
}
void wlanframesync_execute_rxlong0(wlanframesync _q)
{
// set timer to 16, wait for phase to be relatively small
_q->timer++;
if (_q->timer < 16)
return;
// reset timer
_q->timer = 0;
// run fft
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
// estimate S1 gain, adding backoff in gain estimation
wlanframesync_estimate_gain_S1(_q, &rc[16-2], _q->G1a);
// compute S1 metrics
float complex s_hat;
wlanframesync_S1_metrics(_q, _q->G1a, &s_hat);
s_hat *= _q->g0; // scale output by raw gain estimate
// rotate by complex phasor relative to timing backoff
//s_hat *= cexpf(_Complex_I * 2.0f * 2.0f * M_PI / 64.0f);
s_hat *= cexpf(_Complex_I * 0.19635f);
// save first 'long' symbol statistic
_q->s1a_hat = s_hat;
#if DEBUG_WLANFRAMESYNC_PRINT
printf(" s_hat : %12.8f <%12.8f>\n", cabsf(s_hat), cargf(s_hat));
#endif
float s_hat_abs = cabsf(s_hat);
float s_hat_arg = cargf(s_hat);
if (s_hat_arg > M_PI) s_hat_arg -= 2.0f*M_PI;
if (s_hat_arg < -M_PI) s_hat_arg += 2.0f*M_PI;
// check conditions for s_hat:
// 1. magnitude should be large (near unity) when aligned
// 2. phase should be very near zero (time aligned)
if (s_hat_abs > WLANFRAMESYNC_S1A_ABS_THRESH &&
fabsf(s_hat_arg) < WLANFRAMESYNC_S1A_ARG_THRESH)
{
#if DEBUG_WLANFRAMESYNC_PRINT
printf(" acquisition S1[a]\n");
#endif
// set state
_q->state = WLANFRAMESYNC_STATE_RXLONG1;
// reset timer
_q->timer = 0;
}
}
// export debugging file
void ampmodem_debug_print(ampmodem _q,
const char * _filename)
{
FILE * fid = fopen(_filename,"w");
if (!fid) {
fprintf(stderr,"error: ofdmframe_debug_print(), could not open '%s' for writing\n", _filename);
return;
}
fprintf(fid,"%% %s : auto-generated file\n", DEBUG_AMPMODEM_FILENAME);
#if DEBUG_AMPMODEM
fprintf(fid,"close all;\n");
fprintf(fid,"clear all;\n");
fprintf(fid,"n = %u;\n", DEBUG_AMPMODEM_BUFFER_LEN);
unsigned int i;
float complex * rc;
float * r;
// plot received signal
fprintf(fid,"x = zeros(1,n);\n");
windowcf_read(_q->debug_x, &rc);
for (i=0; i<DEBUG_AMPMODEM_BUFFER_LEN; i++)
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(0:(n-1),real(x),0:(n-1),imag(x));\n");
fprintf(fid,"xlabel('sample index');\n");
fprintf(fid,"ylabel('received signal, x');\n");
// plot phase/freq error
fprintf(fid,"phase_error = zeros(1,n);\n");
windowf_read(_q->debug_phase_error, &r);
for (i=0; i<DEBUG_AMPMODEM_BUFFER_LEN; i++)
fprintf(fid,"phase_error(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"freq_error = zeros(1,n);\n");
windowf_read(_q->debug_freq_error, &r);
for (i=0; i<DEBUG_AMPMODEM_BUFFER_LEN; i++)
fprintf(fid,"freq_error(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1),\n");
fprintf(fid," plot(0:(n-1),phase_error);\n");
fprintf(fid," xlabel('sample index');\n");
fprintf(fid," ylabel('phase error');\n");
fprintf(fid,"subplot(2,1,2),\n");
fprintf(fid," plot(0:(n-1),freq_error);\n");
fprintf(fid," xlabel('sample index');\n");
fprintf(fid," ylabel('freq error');\n");
#else
fprintf(fid,"disp('no debugging info available');\n");
#endif
fclose(fid);
printf("ampmodem/debug: results written to '%s'\n", _filename);
}
// push buffered p/n sequence through synchronizer
void gmskframesync_pushpn(gmskframesync _q)
{
unsigned int i;
// reset filterbanks
firpfb_rrrf_reset(_q->mf);
firpfb_rrrf_reset(_q->dmf);
// read buffer
float complex * rc;
windowcf_read(_q->buffer, &rc);
// compute delay and filterbank index
// tau_hat < 0 : delay = 2*k*m-1, index = round( tau_hat *npfb), flag = 0
// tau_hat > 0 : delay = 2*k*m-2, index = round((1-tau_hat)*npfb), flag = 0
assert(_q->tau_hat < 0.5f && _q->tau_hat > -0.5f);
unsigned int delay = 2*_q->k*_q->m - 1; // samples to buffer before computing output
_q->pfb_soft = -_q->tau_hat*_q->npfb;
_q->pfb_index = (int) roundf(_q->pfb_soft);
while (_q->pfb_index < 0) {
delay -= 1;
_q->pfb_index += _q->npfb;
_q->pfb_soft += _q->npfb;
}
_q->pfb_timer = 0;
// set coarse carrier frequency offset
nco_crcf_set_frequency(_q->nco_coarse, _q->dphi_hat);
unsigned int buffer_len = (_q->preamble_len + _q->m) * _q->k;
for (i=0; i<buffer_len; i++) {
if (i < delay) {
float complex y;
nco_crcf_mix_down(_q->nco_coarse, rc[i], &y);
nco_crcf_step(_q->nco_coarse);
// update instantanenous frequency estimate
gmskframesync_update_fi(_q, y);
// push initial samples into filterbanks
firpfb_rrrf_push(_q->mf, _q->fi_hat);
firpfb_rrrf_push(_q->dmf, _q->fi_hat);
} else {
// run remaining samples through p/n sequence recovery
gmskframesync_execute_rxpreamble(_q, rc[i]);
}
}
// set state (still need a few more samples before entire p/n
// sequence has been received)
_q->state = STATE_RXPREAMBLE;
}
// frame detection
void ofdmframesync_execute_S0a(ofdmframesync _q)
{
//printf("t : %u\n", _q->timer);
_q->timer++;
if (_q->timer < _q->M2)
return;
// reset timer
_q->timer = 0;
//
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
// TODO : re-estimate nominal gain
// estimate S0 gain
ofdmframesync_estimate_gain_S0(_q, &rc[_q->cp_len], _q->G0);
float complex s_hat;
ofdmframesync_S0_metrics(_q, _q->G0, &s_hat);
s_hat *= _q->g0;
_q->s_hat_0 = s_hat;
#if DEBUG_OFDMFRAMESYNC_PRINT
float tau_hat = cargf(s_hat) * (float)(_q->M2) / (2*M_PI);
printf("********** S0[0] received ************\n");
printf(" s_hat : %12.8f <%12.8f>\n", cabsf(s_hat), cargf(s_hat));
printf(" tau_hat : %12.8f\n", tau_hat);
#endif
#if 0
// TODO : also check for phase of s_hat (should be small)
if (cabsf(s_hat) < 0.3f) {
// false alarm
#if DEBUG_OFDMFRAMESYNC_PRINT
printf("false alarm S0[0]\n");
#endif
ofdmframesync_reset(_q);
return;
}
#endif
_q->state = OFDMFRAMESYNC_STATE_PLCPSHORT1;
}
void ofdmoqamframe64sync_execute_plcplong0(ofdmoqamframe64sync _q, float complex _x)
{
// cross-correlator
float complex rxy;
firfilt_cccf_push(_q->crosscorr, _x);
firfilt_cccf_execute(_q->crosscorr, &rxy);
rxy *= _q->g;
#if DEBUG_OFDMOQAMFRAME64SYNC
windowcf_push(_q->debug_rxy, rxy);
#endif
_q->timer++;
if (_q->timer > 10*(_q->num_subcarriers)) {
#if DEBUG_OFDMOQAMFRAME64SYNC_PRINT
printf("warning: ofdmoqamframe64sync could not find first PLCP long sequence; resetting synchronizer\n");
#endif
ofdmoqamframe64sync_reset(_q);
return;
}
if (cabsf(rxy) > (_q->rxy_thresh)*(_q->num_subcarriers)) {
#if DEBUG_OFDMOQAMFRAME64SYNC_PRINT
printf("rxy[0] : %12.8f at input[%3u]\n", cabsf(rxy), _q->num_samples);
#endif
// run analyzers
//firpfbch_analyzer_run(_q->ca0, _q->S1a);
//firpfbch_analyzer_run(_q->ca1, _q->S1b);
_q->sample_phase = (_q->num_samples + (_q->num_subcarriers)/2) % _q->num_subcarriers;
//_q->sample_phase = (_q->num_samples) % _q->num_subcarriers;
#if DEBUG_OFDMOQAMFRAME64SYNC_PRINT
printf("sample phase : %u\n",_q->sample_phase);
#endif
//
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
memmove(_q->S1a, rc, 64*sizeof(float complex));
_q->state = OFDMOQAMFRAME64SYNC_STATE_PLCPLONG1;
_q->timer = 0;
}
}
void do_spectrum() {
std::complex<float> *data_in;
windowcf_read(w, &data_in);
fftplan q = fft_create_plan(SPECTRUM_FFT_LENGTH,data_in,spectrum_fft_output,LIQUID_FFT_FORWARD,0);
fft_execute(q);
fft_destroy_plan(q);
spectrum_fft_magnitude[0] = 0.0; //Do not consider DC comp
int maxIdx = 0;
float maxVal = 0;
double total_power = 0;
double psd = 0;
for (int i = 1; i < SPECTRUM_FFT_LENGTH/2; i++) {
spectrum_fft_magnitude[i] = std::norm(spectrum_fft_output[i]);
total_power += spectrum_fft_magnitude[i];
if (spectrum_fft_magnitude[i] > maxVal) {
maxIdx = i;
maxVal = spectrum_fft_magnitude[i];
}
}
// TODO normalize so window size does not affect this threshold.
psd = maxVal / total_power;
if (shm_settings.auto_magnitude_thresholding == 0) {
if (psd > shm_settings.spectrum_magnitude_threshold && (current_sample_count - old_spectrum_sample_count > shm_settings.spectrum_cooldown_samples)) {
shm_results_spectrum.most_recent_ping_magnitude = maxVal;
shm_results_spectrum.most_recent_ping_frequency = (double) SAMPLING_FREQUENCY / (double) SPECTRUM_FFT_LENGTH * (double) maxIdx;
shm_results_spectrum.most_recent_ping_count++;
old_spectrum_sample_count = current_sample_count;
shm_setg(hydrophones_results_spectrum, shm_results_spectrum);
}
prev_psd = psd;
}
else {
//IMPLEMENTE AUTO THRESHOLDING AND ASSOCIATED PING STUFF
}
}
void ofdmframesync_execute_rxsymbols(ofdmframesync _q)
{
// wait for timeout
_q->timer--;
if (_q->timer == 0) {
// run fft
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
memmove(_q->x, &rc[_q->cp_len-_q->backoff], (_q->M)*sizeof(float complex));
FFT_EXECUTE(_q->fft);
// recover symbol in internal _q->X buffer
ofdmframesync_rxsymbol(_q);
#if DEBUG_OFDMFRAMESYNC
if (_q->debug_enabled) {
unsigned int i;
for (i=0; i<_q->M; i++) {
if (_q->p[i] == OFDMFRAME_SCTYPE_DATA)
windowcf_push(_q->debug_framesyms, _q->X[i]);
}
}
#endif
// invoke callback
if (_q->callback != NULL) {
int retval = _q->callback(_q->X, _q->p, _q->M, _q->userdata);
if (retval != 0)
ofdmframesync_reset(_q);
}
// reset timer
_q->timer = _q->M + _q->cp_len;
}
}
void do_track(){
if (local_track_freq != shm_settings.track_frequency_target) {
if (ff.sosMap.count(shm_settings.track_frequency_target)) { //frequency key exists
if (track_filterA != NULL)
iirfilt_crcf_destroy(track_filterA);
if (track_filterB != NULL)
iirfilt_crcf_destroy(track_filterB);
if (track_filterC != NULL)
iirfilt_crcf_destroy(track_filterC);
float *b = &((ff.sosMap[shm_settings.track_frequency_target]->b)[0]);
float *a = &((ff.sosMap[shm_settings.track_frequency_target]->a)[0]);
track_filterA = iirfilt_crcf_create_sos(b,a,NUMBER_OF_SECTIONS);
track_filterB = iirfilt_crcf_create_sos(b,a,NUMBER_OF_SECTIONS);
track_filterC = iirfilt_crcf_create_sos(b,a,NUMBER_OF_SECTIONS);
shm_results_track.track_state = 0;
local_track_freq = shm_settings.track_frequency_target;
float normalized_frequency = (float) shm_settings.track_frequency_target / (float) SAMPLING_FREQUENCY;
nco_crcf_set_frequency(nco,2*M_PI*normalized_frequency);
}
else { //frequency key does not exist. Trigger error state
shm_results_track.track_state = -1;
std::cerr << shm_settings.track_frequency_target << " WARN TRACK FREQ NOT IN SOS TABLE" << std::endl;
}
shm_setg(hydrophones_results_track, shm_results_track);
}
std::complex<float> *chA_ptr, *chA_filtered_ptr;
std::complex<float> *chB_ptr, *chB_filtered_ptr;
std::complex<float> *chC_ptr, *chC_filtered_ptr;
float *mag_ptr;
windowcf_read(wchA,&chA_ptr);
windowcf_read(wchB,&chB_ptr);
windowcf_read(wchC,&chC_ptr);
std::complex<float> filtOutA, filtOutB, filtOutC;
for (int i = 0; i < SAMPLING_DEPTH; i++) {
iirfilt_crcf_execute(track_filterA,chA_ptr[i],&filtOutA);
iirfilt_crcf_execute(track_filterB,chB_ptr[i],&filtOutB);
iirfilt_crcf_execute(track_filterC,chC_ptr[i],&filtOutC);
windowcf_read(wchA_filtered,&chA_filtered_ptr);
windowcf_read(wchB_filtered,&chB_filtered_ptr);
windowcf_read(wchC_filtered,&chC_filtered_ptr);
windowcf_push(wchA_filtered,filtOutA);
windowcf_push(wchB_filtered,filtOutB);
windowcf_push(wchC_filtered,filtOutC);
float b_sqrd = std::pow(std::real(filtOutB),2);
pwr_sum += b_sqrd;
windowf_read(wmag_buffer,&mag_ptr);
pwr_sum -= mag_ptr[0];
windowf_push(wmag_buffer,b_sqrd);
double normalized_pwr = pwr_sum / (double)TRACK_LENGTH;
if (normalized_pwr > shm_settings.track_magnitude_threshold &&
(track_sample_idx - shm_results_track.tracked_ping_time) >= shm_settings.track_cooldown_samples) {
std::complex<float> dtft_coeff_A = goertzelNonInteger(chA_filtered_ptr,TRACK_LENGTH,shm_settings.track_frequency_target,SAMPLING_FREQUENCY);
std::complex<float> dtft_coeff_B = goertzelNonInteger(chB_filtered_ptr,TRACK_LENGTH,shm_settings.track_frequency_target,SAMPLING_FREQUENCY);
std::complex<float> dtft_coeff_C = goertzelNonInteger(chC_filtered_ptr,TRACK_LENGTH,shm_settings.track_frequency_target,SAMPLING_FREQUENCY);
float phaseA = std::arg(dtft_coeff_A);
float phaseB = std::arg(dtft_coeff_B);
float phaseC = std::arg(dtft_coeff_C);
shm_results_track.diff_phase_y = phase_difference(phaseC,phaseB);
shm_results_track.diff_phase_x = phase_difference(phaseA,phaseB);
float kx = SOUND_SPEED * shm_results_track.diff_phase_x / (NIPPLE_DISTANCE * 2 * M_PI * shm_settings.track_frequency_target);
float ky = SOUND_SPEED * shm_results_track.diff_phase_y / (NIPPLE_DISTANCE * 2 * M_PI * shm_settings.track_frequency_target);
float kz_2 = 1 - kx * kx - ky * ky;
if (kz_2 < 0) {
std::cerr << "WARNING: z mag is negative! " << kz_2 << std::endl;
kz_2 = 0;
}
shm_results_track.tracked_ping_heading_radians = std::atan2(ky, kx);
shm_results_track.tracked_ping_elevation_radians = std::acos(std::sqrt(kz_2));
shm_results_track.tracked_ping_count++;
shm_results_track.tracked_ping_frequency = shm_results_spectrum.most_recent_ping_frequency;
shm_results_track.tracked_ping_time = track_sample_idx;
std::cout << "PING DETECTED @ n=" << track_sample_idx << " w/ pwr="<< normalized_pwr<< std::endl;
std::cout << "@ HEADING=" << shm_results_track.tracked_ping_heading_radians*(180.0f/M_PI) << std::endl;
shm_setg(hydrophones_results_track, shm_results_track);
}
track_sample_idx++;
}
}
// receive the 'SIGNAL' field
void wlanframesync_execute_rxsignal(wlanframesync _q)
{
_q->timer++;
if (_q->timer < 80)
return;
// reset timer
_q->timer = 0;
// run fft
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
memmove(_q->x, &rc[16-2], 64*sizeof(float complex));
// compute fft, storing result into _q->X
FFT_EXECUTE(_q->fft);
// recover symbol, correcting for gain, pilot phase, etc.
wlanframesync_rxsymbol(_q);
// demodulate, decode, ...
memset(_q->signal_int, 0x00, 6*sizeof(unsigned char));
_q->signal_int[0] |= crealf(_q->X[38]) > 0.0f ? 0x80 : 0x00;
_q->signal_int[0] |= crealf(_q->X[39]) > 0.0f ? 0x40 : 0x00;
_q->signal_int[0] |= crealf(_q->X[40]) > 0.0f ? 0x20 : 0x00;
_q->signal_int[0] |= crealf(_q->X[41]) > 0.0f ? 0x10 : 0x00;
_q->signal_int[0] |= crealf(_q->X[42]) > 0.0f ? 0x08 : 0x00;
// 43 : pilot
_q->signal_int[0] |= crealf(_q->X[44]) > 0.0f ? 0x04 : 0x00;
_q->signal_int[0] |= crealf(_q->X[45]) > 0.0f ? 0x02 : 0x00;
_q->signal_int[0] |= crealf(_q->X[46]) > 0.0f ? 0x01 : 0x00;
_q->signal_int[1] |= crealf(_q->X[47]) > 0.0f ? 0x80 : 0x00;
_q->signal_int[1] |= crealf(_q->X[48]) > 0.0f ? 0x40 : 0x00;
_q->signal_int[1] |= crealf(_q->X[49]) > 0.0f ? 0x20 : 0x00;
_q->signal_int[1] |= crealf(_q->X[50]) > 0.0f ? 0x10 : 0x00;
_q->signal_int[1] |= crealf(_q->X[51]) > 0.0f ? 0x08 : 0x00;
_q->signal_int[1] |= crealf(_q->X[52]) > 0.0f ? 0x04 : 0x00;
_q->signal_int[1] |= crealf(_q->X[53]) > 0.0f ? 0x02 : 0x00;
_q->signal_int[1] |= crealf(_q->X[54]) > 0.0f ? 0x01 : 0x00;
_q->signal_int[2] |= crealf(_q->X[55]) > 0.0f ? 0x80 : 0x00;
_q->signal_int[2] |= crealf(_q->X[56]) > 0.0f ? 0x40 : 0x00;
// 57 : pilot
_q->signal_int[2] |= crealf(_q->X[58]) > 0.0f ? 0x20 : 0x00;
_q->signal_int[2] |= crealf(_q->X[59]) > 0.0f ? 0x10 : 0x00;
_q->signal_int[2] |= crealf(_q->X[60]) > 0.0f ? 0x08 : 0x00;
_q->signal_int[2] |= crealf(_q->X[61]) > 0.0f ? 0x04 : 0x00;
_q->signal_int[2] |= crealf(_q->X[62]) > 0.0f ? 0x02 : 0x00;
_q->signal_int[2] |= crealf(_q->X[63]) > 0.0f ? 0x01 : 0x00;
// 0 : NULL
_q->signal_int[3] |= crealf(_q->X[ 1]) > 0.0f ? 0x80 : 0x00;
_q->signal_int[3] |= crealf(_q->X[ 2]) > 0.0f ? 0x40 : 0x00;
_q->signal_int[3] |= crealf(_q->X[ 3]) > 0.0f ? 0x20 : 0x00;
_q->signal_int[3] |= crealf(_q->X[ 4]) > 0.0f ? 0x10 : 0x00;
_q->signal_int[3] |= crealf(_q->X[ 5]) > 0.0f ? 0x08 : 0x00;
_q->signal_int[3] |= crealf(_q->X[ 6]) > 0.0f ? 0x04 : 0x00;
// 7 : pilot
_q->signal_int[3] |= crealf(_q->X[ 8]) > 0.0f ? 0x02 : 0x00;
_q->signal_int[3] |= crealf(_q->X[ 9]) > 0.0f ? 0x01 : 0x00;
_q->signal_int[4] |= crealf(_q->X[10]) > 0.0f ? 0x80 : 0x00;
_q->signal_int[4] |= crealf(_q->X[11]) > 0.0f ? 0x40 : 0x00;
_q->signal_int[4] |= crealf(_q->X[12]) > 0.0f ? 0x20 : 0x00;
_q->signal_int[4] |= crealf(_q->X[13]) > 0.0f ? 0x10 : 0x00;
_q->signal_int[4] |= crealf(_q->X[14]) > 0.0f ? 0x08 : 0x00;
_q->signal_int[4] |= crealf(_q->X[15]) > 0.0f ? 0x04 : 0x00;
_q->signal_int[4] |= crealf(_q->X[16]) > 0.0f ? 0x02 : 0x00;
_q->signal_int[4] |= crealf(_q->X[17]) > 0.0f ? 0x01 : 0x00;
_q->signal_int[5] |= crealf(_q->X[18]) > 0.0f ? 0x80 : 0x00;
_q->signal_int[5] |= crealf(_q->X[19]) > 0.0f ? 0x40 : 0x00;
_q->signal_int[5] |= crealf(_q->X[20]) > 0.0f ? 0x20 : 0x00;
// 21 : pilot
_q->signal_int[5] |= crealf(_q->X[22]) > 0.0f ? 0x10 : 0x00;
_q->signal_int[5] |= crealf(_q->X[23]) > 0.0f ? 0x08 : 0x00;
_q->signal_int[5] |= crealf(_q->X[24]) > 0.0f ? 0x04 : 0x00;
_q->signal_int[5] |= crealf(_q->X[25]) > 0.0f ? 0x02 : 0x00;
_q->signal_int[5] |= crealf(_q->X[26]) > 0.0f ? 0x01 : 0x00;
// decode SIGNAL field
wlanframesync_decode_signal(_q);
// validate proper decoding
if (!_q->signal_valid) {
// reset synchronizer and return
wlanframesync_reset(_q);
return;
}
// set state
_q->state = WLANFRAMESYNC_STATE_RXDATA;
}
int main(int argc, char*argv[])
{
// options
int ftype = LIQUID_FIRFILT_ARKAISER;
int ms = LIQUID_MODEM_QPSK;
unsigned int k = 2; // samples per symbol
unsigned int m = 7; // filter delay (symbols)
float beta = 0.20f; // filter excess bandwidth factor
unsigned int num_symbols = 4000; // number of data symbols
unsigned int hc_len = 4; // channel filter length
float noise_floor = -60.0f; // noise floor [dB]
float SNRdB = 30.0f; // signal-to-noise ratio [dB]
float bandwidth = 0.02f; // loop filter bandwidth
float tau = -0.2f; // fractional symbol offset
float rate = 1.001f; // sample rate offset
float dphi = 0.01f; // carrier frequency offset [radians/sample]
float phi = 2.1f; // carrier phase offset [radians]
unsigned int nfft = 2400; // spectral periodogram FFT size
unsigned int num_samples = 200000; // number of samples
int dopt;
while ((dopt = getopt(argc,argv,"hk:m:b:s:w:n:t:r:")) != EOF) {
switch (dopt) {
case 'h': usage(); return 0;
case 'k': k = atoi(optarg); break;
case 'm': m = atoi(optarg); break;
case 'b': beta = atof(optarg); break;
case 's': SNRdB = atof(optarg); break;
case 'w': bandwidth = atof(optarg); break;
case 'n': num_symbols = atoi(optarg); break;
case 't': tau = atof(optarg); break;
case 'r': rate = atof(optarg); break;
default:
exit(1);
}
}
// validate input
if (k < 2) {
fprintf(stderr,"error: k (samples/symbol) must be greater than 1\n");
exit(1);
} else if (m < 1) {
fprintf(stderr,"error: m (filter delay) must be greater than 0\n");
exit(1);
} else if (beta <= 0.0f || beta > 1.0f) {
fprintf(stderr,"error: beta (excess bandwidth factor) must be in (0,1]\n");
exit(1);
} else if (bandwidth <= 0.0f) {
fprintf(stderr,"error: timing PLL bandwidth must be greater than 0\n");
exit(1);
} else if (num_symbols == 0) {
fprintf(stderr,"error: number of symbols must be greater than 0\n");
exit(1);
} else if (tau < -1.0f || tau > 1.0f) {
fprintf(stderr,"error: timing phase offset must be in [-1,1]\n");
exit(1);
} else if (rate > 1.02f || rate < 0.98f) {
fprintf(stderr,"error: timing rate offset must be in [1.02,0.98]\n");
exit(1);
}
unsigned int i;
// buffers
unsigned int buf_len = 400; // buffer size
float complex x [buf_len]; // original signal
float complex y [buf_len*2]; // channel output (larger to accommodate resampler)
float complex syms[buf_len]; // recovered symbols
// window for saving last few symbols
windowcf sym_buf = windowcf_create(buf_len);
// create stream generator
symstreamcf gen = symstreamcf_create_linear(ftype,k,m,beta,ms);
// create channel emulator and add impairments
channel_cccf channel = channel_cccf_create();
channel_cccf_add_awgn (channel, noise_floor, SNRdB);
channel_cccf_add_carrier_offset(channel, dphi, phi);
channel_cccf_add_multipath (channel, NULL, hc_len);
channel_cccf_add_resamp (channel, 0.0f, rate);
// create symbol tracking synchronizer
symtrack_cccf symtrack = symtrack_cccf_create(ftype,k,m,beta,ms);
symtrack_cccf_set_bandwidth(symtrack,0.05f);
// create spectral periodogram for estimating spectrum
spgramcf periodogram = spgramcf_create_default(nfft);
unsigned int total_samples = 0;
unsigned int ny;
unsigned int total_symbols = 0;
while (total_samples < num_samples)
{
// write samples to buffer
symstreamcf_write_samples(gen, x, buf_len);
// apply channel
channel_cccf_execute(channel, x, buf_len, y, &ny);
// push resulting sample through periodogram
spgramcf_write(periodogram, y, ny);
// run resulting stream through synchronizer
unsigned int num_symbols_sync;
symtrack_cccf_execute_block(symtrack, y, ny, syms, &num_symbols_sync);
total_symbols += num_symbols_sync;
// write resulting symbols to window buffer for plotting
windowcf_write(sym_buf, syms, num_symbols_sync);
// accumulated samples
total_samples += buf_len;
}
printf("total samples: %u\n", total_samples);
printf("total symbols: %u\n", total_symbols);
// write accumulated power spectral density estimate
float psd[nfft];
spgramcf_get_psd(periodogram, psd);
//
// export output file
//
FILE * fid = fopen(OUTPUT_FILENAME,"w");
fprintf(fid,"%% %s, auto-generated file\n\n", OUTPUT_FILENAME);
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n");
// read buffer and write last symbols to file
float complex * rc;
windowcf_read(sym_buf, &rc);
fprintf(fid,"syms = zeros(1,%u);\n", buf_len);
for (i=0; i<buf_len; i++)
fprintf(fid,"syms(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
// power spectral density estimate
fprintf(fid,"nfft = %u;\n", nfft);
fprintf(fid,"f=[0:(nfft-1)]/nfft - 0.5;\n");
fprintf(fid,"psd = zeros(1,nfft);\n");
for (i=0; i<nfft; i++)
fprintf(fid,"psd(%3u) = %12.8f;\n", i+1, psd[i]);
fprintf(fid,"figure('Color','white','position',[500 500 1400 400]);\n");
fprintf(fid,"subplot(1,3,1);\n");
fprintf(fid,"plot(real(syms),imag(syms),'x','MarkerSize',4);\n");
fprintf(fid," axis square;\n");
fprintf(fid," grid on;\n");
fprintf(fid," axis([-1 1 -1 1]*1.6);\n");
fprintf(fid," xlabel('In-phase');\n");
fprintf(fid," ylabel('Quadrature');\n");
fprintf(fid," title('Last %u symbols');\n", buf_len);
fprintf(fid,"subplot(1,3,2:3);\n");
fprintf(fid," plot(f, psd, 'LineWidth',1.5,'Color',[0 0.5 0.2]);\n");
fprintf(fid," grid on;\n");
fprintf(fid," pmin = 10*floor(0.1*min(psd - 5));\n");
fprintf(fid," pmax = 10*ceil (0.1*max(psd + 5));\n");
fprintf(fid," axis([-0.5 0.5 pmin pmax]);\n");
fprintf(fid," xlabel('Normalized Frequency [f/F_s]');\n");
fprintf(fid," ylabel('Power Spectral Density [dB]');\n");
fclose(fid);
printf("results written to %s.\n", OUTPUT_FILENAME);
// destroy objects
symstreamcf_destroy (gen);
spgramcf_destroy (periodogram);
channel_cccf_destroy (channel);
symtrack_cccf_destroy(symtrack);
windowcf_destroy (sym_buf);
// clean it up
printf("done.\n");
return 0;
}
void ofdmoqamframe64sync_debug_print(ofdmoqamframe64sync _q)
{
FILE * fid = fopen(DEBUG_OFDMOQAMFRAME64SYNC_FILENAME,"w");
if (!fid) {
printf("error: ofdmoqamframe64_debug_print(), could not open file for writing\n");
return;
}
fprintf(fid,"%% %s : auto-generated file\n", DEBUG_OFDMOQAMFRAME64SYNC_FILENAME);
fprintf(fid,"close all;\n");
fprintf(fid,"clear all;\n");
fprintf(fid,"n = %u;\n", DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN);
unsigned int i;
float complex * rc;
float * r;
// gain vectors
fprintf(fid,"g = %12.4e;\n", _q->g);
for (i=0; i<_q->num_subcarriers; i++) {
fprintf(fid,"G(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->G[i]), cimagf(_q->G[i]));
//fprintf(fid,"G0(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->G0[i]), cimagf(_q->G0[i]));
//fprintf(fid,"G1(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->G1[i]), cimagf(_q->G1[i]));
}
for (i=0; i<4; i++) {
fprintf(fid,"phi(%3u) = %12.8f;\n", i+1, _q->y_phase[i]);
}
fprintf(fid,"figure;\n");
fprintf(fid,"f = -32:31;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(f,fftshift(abs(G)));\n");
fprintf(fid," xlabel('subcarrier index');\n");
fprintf(fid," ylabel('|G|');\n");
fprintf(fid," grid on;\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(f,fftshift(arg(G)));\n");
fprintf(fid," xlabel('subcarrier index');\n");
fprintf(fid," ylabel('arg\\{G\\}');\n");
fprintf(fid," grid on;\n");
// CFO estimate
fprintf(fid,"nu_hat = %12.4e;\n", _q->nu_hat);
// short, long, training sequences
for (i=0; i<_q->num_subcarriers; i++) {
fprintf(fid,"S0(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->S0[i]), cimagf(_q->S0[i]));
fprintf(fid,"S1(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->S1[i]), cimagf(_q->S1[i]));
fprintf(fid,"S2(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->S2[i]), cimagf(_q->S2[i]));
}
fprintf(fid,"x = zeros(1,n);\n");
windowcf_read(_q->debug_x, &rc);
for (i=0; i<DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN; i++)
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(0:(n-1),real(x),0:(n-1),imag(x));\n");
fprintf(fid,"xlabel('sample index');\n");
fprintf(fid,"ylabel('received signal, x');\n");
fprintf(fid,"rxx = zeros(1,n);\n");
windowcf_read(_q->debug_rxx, &rc);
for (i=0; i<DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN; i++)
fprintf(fid,"rxx(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(0:(n-1),abs(rxx),'-k','LineWidth',2);\n");
fprintf(fid,"xlabel('sample index');\n");
fprintf(fid,"ylabel('|r_{xx}|');\n");
fprintf(fid,"rxy = zeros(1,n);\n");
windowcf_read(_q->debug_rxy, &rc);
for (i=0; i<DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN; i++)
fprintf(fid,"rxy(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(0:(n-1),abs(rxy));\n");
fprintf(fid,"xlabel('sample index');\n");
fprintf(fid,"ylabel('|r_{xy}|');\n");
// decoded long sequences
fprintf(fid,"S1 = zeros(1,64);\n");
fprintf(fid,"S1a = zeros(1,64);\n");
fprintf(fid,"S1b = zeros(1,64);\n");
fprintf(fid,"Y0 = zeros(1,64);\n");
fprintf(fid,"Y1 = zeros(1,64);\n");
for (i=0; i<64; i++) {
fprintf(fid,"S1(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->S1[i]), cimagf(_q->S1[i]));
fprintf(fid,"S1a(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->S1a[i]), cimagf(_q->S1a[i]));
fprintf(fid,"S1b(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->S1b[i]), cimagf(_q->S1b[i]));
fprintf(fid,"Y0(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->Y0[i]), cimagf(_q->Y0[i]));
fprintf(fid,"Y1(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->Y1[i]), cimagf(_q->Y1[i]));
}
fprintf(fid,"zeta = 64/sqrt(52/2);\n");
fprintf(fid,"S1 = S1 / zeta;\n");
fprintf(fid,"S1a = S1a / zeta;\n");
fprintf(fid,"S1b = S1b / zeta;\n");
fprintf(fid,"Y0 = Y0 / zeta;\n");
fprintf(fid,"Y1 = Y1 / zeta;\n");
fprintf(fid,"t0 = 1:2:64;\n");
fprintf(fid,"t1 = 2:2:64;\n");
fprintf(fid,"S = zeros(1,64);\n");
fprintf(fid,"S(t0) = real(S1a(t0)) + j*imag(S1b(t0));\n");
fprintf(fid,"S(t1) = real(S1b(t1)) + j*imag(S1a(t1));\n");
fprintf(fid,"Y = zeros(1,64);\n");
fprintf(fid,"Y(t0) = real(Y0(t0)) + j*imag(Y1(t0));\n");
fprintf(fid,"Y(t1) = real(Y1(t1)) + j*imag(Y0(t1));\n");
fprintf(fid,"figure;\n");
//fprintf(fid,"f = [(0:63)]/64 - 0.5;\n");
//fprintf(fid,"plot(S1,'x',S1a,'x',S1b,'x');\n");
fprintf(fid,"plot(S1,'x',S,'x',S1a,'x',S1b,'x');\n");
fprintf(fid,"legend('S1','S','S1a','S1b',0);\n");
fprintf(fid,"xlabel('I');\n");
fprintf(fid,"ylabel('Q');\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"axis([-1 1 -1 1]*1.3);\n");
fprintf(fid,"title('PLCP long sequences');\n");
// pilot phase
fprintf(fid,"pilotphase = zeros(1,n);\n");
windowf_read(_q->debug_pilotphase, &r);
for (i=0; i<DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN; i++)
fprintf(fid,"pilotphase(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"pilotphase_hat = zeros(1,n);\n");
windowf_read(_q->debug_pilotphase_hat, &r);
for (i=0; i<DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN; i++)
fprintf(fid,"pilotphase_hat(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"figure;\n");
fprintf(fid,"plot(0:(127),pilotphase([n-128+1]:n),'-k',0:(127),pilotphase_hat([n-128+1]:n),'-k','LineWidth',2);\n");
fprintf(fid,"xlabel('sample index');\n");
fprintf(fid,"ylabel('pilot phase');\n");
// rssi (received signal strength indication)
fprintf(fid,"rssi = zeros(1,n);\n");
windowf_read(_q->debug_rssi, &r);
for (i=0; i<DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN; i++)
fprintf(fid,"rssi(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"figure;\n");
fprintf(fid,"plot(0:(n-1),rssi,'-k','LineWidth',2);\n");
fprintf(fid,"xlabel('sample index');\n");
fprintf(fid,"ylabel('RSSI');\n");
// frame symbols
fprintf(fid,"framesyms = zeros(1,n);\n");
windowcf_read(_q->debug_framesyms, &rc);
for (i=0; i<DEBUG_OFDMOQAMFRAME64SYNC_BUFFER_LEN; i++)
fprintf(fid,"framesyms(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(real(framesyms),imag(framesyms),'x','MarkerSize',1);\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"axis([-1.5 1.5 -1.5 1.5]);\n");
fprintf(fid,"xlabel('in-phase');\n");
fprintf(fid,"ylabel('quadrature phase');\n");
fprintf(fid,"title('Frame Symbols');\n");
fclose(fid);
printf("ofdmoqamframe64sync/debug: results written to %s\n", DEBUG_OFDMOQAMFRAME64SYNC_FILENAME);
}
// print debugging information
void flexframesync_debug_print(flexframesync _q,
const char * _filename)
{
#if DEBUG_FLEXFRAMESYNC
if (!_q->debug_objects_created) {
fprintf(stderr,"error: flexframesync_debug_print(), debugging objects don't exist; enable debugging first\n");
return;
}
unsigned int i;
float complex * rc;
FILE* fid = fopen(_filename,"w");
fprintf(fid,"%% %s: auto-generated file", _filename);
fprintf(fid,"\n\n");
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n\n");
fprintf(fid,"n = %u;\n", DEBUG_BUFFER_LEN);
// main figure
fprintf(fid,"figure('Color','white','position',[100 100 800 600]);\n");
// write x
fprintf(fid,"x = zeros(1,n);\n");
windowcf_read(_q->debug_x, &rc);
for (i=0; i<DEBUG_BUFFER_LEN; i++)
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"\n\n");
fprintf(fid,"subplot(3,2,1:2);\n");
fprintf(fid,"plot(1:length(x),real(x), 1:length(x),imag(x));\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"xlabel('sample index');\n");
fprintf(fid,"ylabel('received signal, x');\n");
// write p/n sequence
fprintf(fid,"preamble_pn = zeros(1,64);\n");
rc = _q->preamble_pn;
for (i=0; i<64; i++)
fprintf(fid,"preamble_pn(%4u) = %12.4e + 1i*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
// write p/n symbols
fprintf(fid,"preamble_rx = zeros(1,64);\n");
rc = _q->preamble_rx;
for (i=0; i<64; i++)
fprintf(fid,"preamble_rx(%4u) = %12.4e + 1i*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
// write recovered header symbols (after qpilotsync)
fprintf(fid,"header_mod = zeros(1,%u);\n", _q->header_mod_len);
rc = _q->header_mod;
for (i=0; i<_q->header_mod_len; i++)
fprintf(fid,"header_mod(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
// write raw payload symbols
fprintf(fid,"payload_sym = zeros(1,%u);\n", _q->payload_sym_len);
rc = _q->payload_sym;
for (i=0; i<_q->payload_sym_len; i++)
fprintf(fid,"payload_sym(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"subplot(3,2,[3 5]);\n");
fprintf(fid,"plot(real(header_mod),imag(header_mod),'o');\n");
fprintf(fid,"xlabel('in-phase');\n");
fprintf(fid,"ylabel('quadrature phase');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"axis([-1 1 -1 1]*1.5);\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"title('Received Header Symbols');\n");
fprintf(fid,"subplot(3,2,[4 6]);\n");
fprintf(fid,"plot(real(payload_sym),imag(payload_sym),'+');\n");
fprintf(fid,"xlabel('in-phase');\n");
fprintf(fid,"ylabel('quadrature phase');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"axis([-1 1 -1 1]*1.5);\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"title('Received Payload Symbols');\n");
fprintf(fid,"\n\n");
fclose(fid);
printf("flexframesync/debug: results written to %s\n", _filename);
#else
fprintf(stderr,"flexframesync_debug_print(): compile-time debugging disabled\n");
#endif
}
int main() {
// options
unsigned int num_channels=64; // must be even number
unsigned int num_symbols=16; // number of symbols
unsigned int m=3; // filter delay (symbols)
float beta = 0.9f; // filter excess bandwidth factor
float phi = 0.0f; // carrier phase offset;
float dphi = 0.04f; // carrier frequency offset
// number of frames (compensate for filter delay)
unsigned int num_frames = num_symbols + 2*m;
unsigned int num_samples = num_channels * num_frames;
unsigned int i;
unsigned int j;
// create filter prototype
unsigned int h_len = 2*num_channels*m + 1;
float h[h_len];
float complex hc[h_len];
float complex gc[h_len];
liquid_firdes_rkaiser(num_channels, m, beta, 0.0f, h);
unsigned int g_len = 2*num_channels*m;
for (i=0; i<g_len; i++) {
hc[i] = h[i];
gc[i] = h[g_len-i-1] * cexpf(_Complex_I*dphi*i);
}
// data arrays
float complex s[num_channels]; // input symbols
float complex y[num_samples]; // time-domain samples
float complex Y0[num_frames][num_channels]; // channelized output
float complex Y1[num_frames][num_channels]; // channelized output
// create ofdm/oqam generator object and generate data
ofdmoqam qs = ofdmoqam_create(num_channels, m, beta, 0.0f, LIQUID_SYNTHESIZER, 0);
for (i=0; i<num_frames; i++) {
for (j=0; j<num_channels; j++) {
if (i<num_symbols) {
#if 0
// QPSK on all subcarriers
s[j] = (rand() % 2 ? 1.0f : -1.0f) +
(rand() % 2 ? 1.0f : -1.0f) * _Complex_I;
s[j] *= 1.0f / sqrtf(2.0f);
#else
// BPSK on even subcarriers
s[j] = rand() % 2 ? 1.0f : -1.0f;
s[j] *= (j%2)==0 ? 1.0f : 0.0f;
#endif
} else {
s[j] = 0.0f;
}
}
// run synthesizer
ofdmoqam_execute(qs, s, &y[i*num_channels]);
}
ofdmoqam_destroy(qs);
// channel
for (i=0; i<num_samples; i++)
y[i] *= cexpf(_Complex_I*(phi + dphi*i));
//
// analysis filterbank (receiver)
//
// create filterbank manually
dotprod_cccf dp[num_channels]; // vector dot products
windowcf w[num_channels]; // window buffers
#if DEBUG
// print coefficients
printf("h_prototype:\n");
for (i=0; i<h_len; i++)
printf(" h[%3u] = %12.8f\n", i, h[i]);
#endif
// create objects
unsigned int gc_sub_len = 2*m;
float complex gc_sub[gc_sub_len];
for (i=0; i<num_channels; i++) {
// sub-sample prototype filter, loading coefficients in
// reverse order
#if 0
for (j=0; j<gc_sub_len; j++)
gc_sub[j] = h[j*num_channels+i];
#else
for (j=0; j<gc_sub_len; j++)
gc_sub[gc_sub_len-j-1] = gc[j*num_channels+i];
#endif
// create window buffer and dotprod objects
dp[i] = dotprod_cccf_create(gc_sub, gc_sub_len);
w[i] = windowcf_create(gc_sub_len);
#if DEBUG
printf("gc_sub[%u] : \n", i);
for (j=0; j<gc_sub_len; j++)
printf(" g[%3u] = %12.8f + %12.8f\n", j, crealf(gc_sub[j]), cimagf(gc_sub[j]));
#endif
}
// generate DFT object
float complex x[num_channels]; // time-domain buffer
float complex X[num_channels]; // freq-domain buffer
#if 0
fftplan fft = fft_create_plan(num_channels, X, x, FFT_REVERSE, 0);
#else
fftplan fft = fft_create_plan(num_channels, X, x, FFT_FORWARD, 0);
#endif
//
// run analysis filter bank
//
#if 0
unsigned int filter_index = 0;
#else
unsigned int filter_index = num_channels-1;
#endif
float complex y_hat; // input sample
float complex * r; // read pointer
for (i=0; i<num_frames; i++) {
// load buffers
for (j=0; j<num_channels; j++) {
// grab sample
y_hat = y[i*num_channels + j];
// push sample into buffer at filter index
windowcf_push(w[filter_index], y_hat);
// decrement filter index
filter_index = (filter_index + num_channels - 1) % num_channels;
//filter_index = (filter_index + 1) % num_channels;
}
// execute filter outputs, reversing order of output (not
// sure why this is necessary)
for (j=0; j<num_channels; j++) {
windowcf_read(w[j], &r);
dotprod_cccf_execute(dp[j], r, &X[num_channels-j-1]);
}
#if 1
// compensate for carrier frequency offset (before transform)
for (j=0; j<num_channels; j++) {
X[j] *= cexpf(-_Complex_I*(dphi*i*num_channels));
}
#endif
// execute DFT, store result in buffer 'x'
fft_execute(fft);
#if 0
// compensate for carrier frequency offset (after transform)
for (j=0; j<num_channels; j++) {
x[j] *= cexpf(-_Complex_I*(dphi*i*num_channels));
}
#endif
// move to output array
for (j=0; j<num_channels; j++)
Y0[i][j] = x[j];
}
// destroy objects
for (i=0; i<num_channels; i++) {
dotprod_cccf_destroy(dp[i]);
windowcf_destroy(w[i]);
}
fft_destroy_plan(fft);
#if 0
// print filterbank channelizer
printf("\n");
printf("filterbank channelizer:\n");
for (i=0; i<num_symbols; i++) {
printf("%3u: ", i);
for (j=0; j<num_channels; j++) {
printf(" %8.5f+j%8.5f, ", crealf(Y0[i][j]), cimagf(Y0[i][j]));
}
printf("\n");
}
#endif
//
// export data
//
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,"y = zeros(1,%u);\n", num_samples);
fprintf(fid,"Y0 = zeros(%u,%u);\n", num_frames, num_channels);
fprintf(fid,"Y1 = zeros(%u,%u);\n", num_frames, num_channels);
for (i=0; i<num_frames; i++) {
for (j=0; j<num_channels; j++) {
fprintf(fid,"Y0(%4u,%4u) = %12.4e + j*%12.4e;\n", i+1, j+1, crealf(Y0[i][j]), cimagf(Y0[i][j]));
fprintf(fid,"Y1(%4u,%4u) = %12.4e + j*%12.4e;\n", i+1, j+1, crealf(Y1[i][j]), cimagf(Y1[i][j]));
}
}
// plot BPSK results
fprintf(fid,"figure;\n");
fprintf(fid,"plot(Y0(:,1:2:end),'x');\n");
fprintf(fid,"axis([-1 1 -1 1]*1.2*sqrt(num_channels));\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;
}
void wlanframesync_debug_print(wlanframesync _q,
const char * _filename)
{
#if DEBUG_WLANFRAMESYNC
if (_q->agc_rx == NULL ||
_q->debug_x == NULL ||
_q->debug_rssi == NULL ||
_q->debug_framesyms == NULL)
{
fprintf(stderr,"error: wlanframe_debug_print(), debugging objects don't exist; enable debugging first\n");
return;
}
FILE * fid = fopen(_filename,"w");
if (!fid) {
fprintf(stderr,"error: wlanframe_debug_print(), could not open '%s' for writing\n", _filename);
return;
}
fprintf(fid,"%% %s : auto-generated file\n", _filename);
fprintf(fid,"close all;\n");
fprintf(fid,"clear all;\n");
fprintf(fid,"n = %u;\n", DEBUG_WLANFRAMESYNC_BUFFER_LEN);
unsigned int i;
float complex * rc;
float * r;
fprintf(fid,"x = zeros(1,n);\n");
windowcf_read(_q->debug_x, &rc);
for (i=0; i<DEBUG_WLANFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(0:(n-1),real(x),0:(n-1),imag(x));\n");
fprintf(fid,"xlabel('sample index');\n");
fprintf(fid,"ylabel('received signal, x');\n");
// write agc_rssi
fprintf(fid,"\n\n");
fprintf(fid,"agc_rssi = zeros(1,%u);\n", DEBUG_WLANFRAMESYNC_BUFFER_LEN);
windowf_read(_q->debug_rssi, &r);
for (i=0; i<DEBUG_WLANFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"agc_rssi(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"figure;\n");
fprintf(fid,"plot(agc_rssi)\n");
fprintf(fid,"ylabel('RSSI [dB]');\n");
// write frame symbols
fprintf(fid,"framesyms = zeros(1,n);\n");
windowcf_read(_q->debug_framesyms, &rc);
for (i=0; i<DEBUG_WLANFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"framesyms(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(real(framesyms),imag(framesyms),'x','MarkerSize',2);\n");
fprintf(fid,"axis([-1 1 -1 1]*1.5);\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"xlabel('real');\n");
fprintf(fid,"ylabel('imag');\n");
// write gain arrays
fprintf(fid,"\n\n");
fprintf(fid,"G0a = zeros(1,64);\n");
fprintf(fid,"G0b = zeros(1,64);\n");
fprintf(fid,"G1a = zeros(1,64);\n");
fprintf(fid,"G1b = zeros(1,64);\n");
fprintf(fid,"G = zeros(1,64);\n");
for (i=0; i<64; i++) {
unsigned int k = (i + 32) % 64;
fprintf(fid,"G0a(%3u) = %12.8f + j*%12.8f;\n", k+1, crealf(_q->G0a[i]), cimagf(_q->G0a[i]));
fprintf(fid,"G0b(%3u) = %12.8f + j*%12.8f;\n", k+1, crealf(_q->G0b[i]), cimagf(_q->G0b[i]));
fprintf(fid,"G1a(%3u) = %12.8f + j*%12.8f;\n", k+1, crealf(_q->G1a[i]), cimagf(_q->G1a[i]));
fprintf(fid,"G1b(%3u) = %12.8f + j*%12.8f;\n", k+1, crealf(_q->G1b[i]), cimagf(_q->G1b[i]));
fprintf(fid,"G(%3u) = %12.8f + j*%12.8f;\n", k+1, crealf(_q->G[i]), cimagf(_q->G[i]));
}
fprintf(fid,"%% apply timing offset (backoff) phase shift\n");
fprintf(fid,"f = -32:31;\n");
fprintf(fid,"b = 2;\n");
fprintf(fid,"G0a = G0a.*exp(j*b*2*pi*f/64);\n");
fprintf(fid,"G0b = G0b.*exp(j*b*2*pi*f/64);\n");
fprintf(fid,"G1a = G1a.*exp(j*b*2*pi*f/64);\n");
fprintf(fid,"G1b = G1b.*exp(j*b*2*pi*f/64);\n");
fprintf(fid,"G = G.*exp(j*b*2*pi*f/64);\n");
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(f,abs(G1a),'x', f,abs(G1b),'x', f,abs(G),'-k','LineWidth',2);\n");
fprintf(fid," ylabel('G (mag)');\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(f,arg(G1a),'x', f,arg(G1b),'x', f,arg(G),'-k','LineWidth',2);\n");
fprintf(fid," ylabel('G (phase)');\n");
fclose(fid);
printf("wlanframesync/debug: results written to '%s'\n", _filename);
#else
fprintf(stderr,"wlanframesync_debug_print(): compile-time debugging disabled\n");
#endif
}
void gmskframesync_debug_print(gmskframesync _q,
const char * _filename)
{
#if DEBUG_GMSKFRAMESYNC
if (!_q->debug_objects_created) {
fprintf(stderr,"error: gmskframe_debug_print(), debugging objects don't exist; enable debugging first\n");
return;
}
FILE* fid = fopen(_filename,"w");
if (!fid) {
fprintf(stderr, "error: gmskframesync_debug_print(), could not open '%s' for writing\n", _filename);
return;
}
fprintf(fid,"%% %s: auto-generated file", _filename);
fprintf(fid,"\n\n");
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n\n");
fprintf(fid,"num_samples = %u;\n", DEBUG_GMSKFRAMESYNC_BUFFER_LEN);
fprintf(fid,"t = 0:(num_samples-1);\n");
unsigned int i;
float complex * rc;
// write x
fprintf(fid,"x = zeros(1,num_samples);\n");
windowcf_read(_q->debug_x, &rc);
for (i=0; i<DEBUG_GMSKFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"\n\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(1:length(x),real(x), 1:length(x),imag(x));\n");
fprintf(fid,"ylabel('received signal, x');\n");
fprintf(fid,"\n\n");
// write instantaneous frequency
float * r;
fprintf(fid,"fi = zeros(1,num_samples);\n");
windowf_read(_q->debug_fi, &r);
for (i=0; i<DEBUG_GMSKFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"fi(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"\n\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(1:length(fi),fi);\n");
fprintf(fid,"ylabel('Inst. Freq.');\n");
fprintf(fid,"\n\n");
// write matched filter output
fprintf(fid,"mf = zeros(1,num_samples);\n");
windowf_read(_q->debug_mf, &r);
for (i=0; i<DEBUG_GMSKFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"mf(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"\n\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(1:length(mf),mf);\n");
fprintf(fid,"ylabel('MF output');\n");
fprintf(fid,"\n\n");
#if 0
// write framesyms
fprintf(fid,"framesyms = zeros(1,num_samples);\n");
windowf_read(_q->debug_framesyms, &r);
for (i=0; i<DEBUG_GMSKFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"framesyms(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"\n\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(t,framesyms,'x')\n");
fprintf(fid,"xlabel('time (symbol index)');\n");
fprintf(fid,"ylabel('GMSK demodulator output');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"\n\n");
#endif
fclose(fid);
printf("gmskframesync/debug: results written to '%s'\n", _filename);
#else
fprintf(stderr,"gmskframesync_debug_print(): compile-time debugging disabled\n");
#endif
}
// compute ISI for entire system
// _gt : transmit filter [size: _gt_len x 1]
// _hc : channel filter [size: _hc_len x 1]
// _gr : receive filter [size: _gr_len x 1]
float eqlms_cccf_isi(unsigned int _k,
float complex * _gt,
unsigned int _gt_len,
float complex * _hc,
unsigned int _hc_len,
float complex * _gr,
unsigned int _gr_len)
{
// generate composite by convolving all filters together
unsigned int i;
#if 0
printf("\n");
for (i=0; i<_gt_len; i++)
printf(" gt(%3u) = %16.12f + j*%16.12f;\n", i+1, crealf(_gt[i]), cimagf(_gt[i]));
printf("\n");
for (i=0; i<_hc_len; i++)
printf(" hc(%3u) = %16.12f + j*%16.12f;\n", i+1, crealf(_hc[i]), cimagf(_hc[i]));
printf("\n");
for (i=0; i<_gr_len; i++)
printf(" gr(%3u) = %16.12f + j*%16.12f;\n", i+1, crealf(_gr[i]), cimagf(_gr[i]));
printf("\n");
#endif
windowcf w;
float complex * rc;
// start by convolving transmit and channel filters
unsigned int gthc_len = _gt_len + _hc_len - 1;
float complex gthc[gthc_len];
w = windowcf_create(_gt_len);
for (i=0; i<gthc_len; i++) {
if (i < _hc_len) windowcf_push(w, conjf(_hc[_hc_len-i-1]));
else windowcf_push(w, 0.0f);
windowcf_read(w, &rc);
dotprod_cccf_run(_gt, rc, _gt_len, >hc[i]);
}
windowcf_destroy(w);
#if 0
printf("composite filter:\n");
for (i=0; i<gthc_len; i++)
printf(" gthc(%3u) = %16.12f + j*%16.12f;\n", i+1, crealf(gthc[i]), cimagf(gthc[i]));
#endif
// convolve result with equalizer
unsigned int h_len = gthc_len + _gr_len - 1;
float complex h[h_len];
w = windowcf_create(gthc_len);
for (i=0; i<h_len; i++) {
if (i < _gr_len) windowcf_push(w, conjf(_gr[i]));
else windowcf_push(w, 0.0f);
windowcf_read(w, &rc);
dotprod_cccf_run(gthc, rc, gthc_len, &h[i]);
}
windowcf_destroy(w);
#if 0
printf("composite filter:\n");
for (i=0; i<h_len; i++)
printf(" h(%3u) = %16.12f + j*%16.12f;\n", i+1, crealf(h[i]), cimagf(h[i]));
#endif
// compute resulting ISI
unsigned int n0 = (_gt_len + _gr_len + (_gt_len + _gr_len)%2)/2 - 1;
float isi = 0.0f;
unsigned int n=0;
for (i=0; i<h_len; i++) {
if (i == n0)
continue;
else if ( (i%_k)==0 ) {
isi += crealf( h[i]*conjf(h[i]) );
n++;
}
}
isi /= crealf( h[n0]*conjf(h[n0]) );
isi = sqrtf(isi / (float)n);
return isi;
}
void ofdmframesync_execute_S1(ofdmframesync _q)
{
_q->timer--;
if (_q->timer > 0)
return;
// increment number of symbols observed
_q->num_symbols++;
// run fft
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
// estimate S1 gain
// TODO : add backoff in gain estimation
ofdmframesync_estimate_gain_S1(_q, &rc[_q->cp_len], _q->G);
// compute detector output
float complex g_hat = 0.0f;
unsigned int i;
for (i=0; i<_q->M; i++) {
//g_hat += _q->G[(i+1+_q->M)%_q->M]*conjf(_q->G[(i+_q->M)%_q->M]);
g_hat += _q->G[(i+1)%_q->M]*conjf(_q->G[i]);
}
g_hat /= _q->M_S1; // normalize output
g_hat *= _q->g0;
// rotate by complex phasor relative to timing backoff
g_hat *= liquid_cexpjf((float)(_q->backoff)*2.0f*M_PI/(float)(_q->M));
#if DEBUG_OFDMFRAMESYNC_PRINT
printf(" g_hat : %12.4f <%12.8f>\n", cabsf(g_hat), cargf(g_hat));
#endif
// check conditions for g_hat:
// 1. magnitude should be large (near unity) when aligned
// 2. phase should be very near zero (time aligned)
if (cabsf(g_hat) > _q->plcp_sync_thresh && fabsf(cargf(g_hat)) < 0.1f*M_PI ) {
//printf(" acquisition\n");
_q->state = OFDMFRAMESYNC_STATE_RXSYMBOLS;
// reset timer
_q->timer = _q->M + _q->cp_len + _q->backoff;
_q->num_symbols = 0;
// normalize gain by subcarriers, apply timing backoff correction
float g = (float)(_q->M) / sqrtf(_q->M_pilot + _q->M_data);
for (i=0; i<_q->M; i++) {
_q->G[i] *= g; // gain due to relative subcarrier allocation
_q->G[i] *= _q->B[i]; // timing backoff correction
}
#if 0
// TODO : choose number of taps more appropriately
//unsigned int ntaps = _q->M / 4;
unsigned int ntaps = (_q->M < 8) ? 2 : 8;
// FIXME : this is by far the most computationally complex part of synchronization
ofdmframesync_estimate_eqgain(_q, ntaps);
#else
unsigned int poly_order = 4;
if (poly_order >= _q->M_pilot + _q->M_data)
poly_order = _q->M_pilot + _q->M_data - 1;
ofdmframesync_estimate_eqgain_poly(_q, poly_order);
#endif
#if 1
// compute composite gain
unsigned int i;
for (i=0; i<_q->M; i++)
_q->R[i] = _q->B[i] / _q->G[i];
#endif
return;
#if 0
printf("exiting prematurely\n");
ofdmframesync_destroy(_q);
exit(1);
#endif
}
// check if we are stuck searching for the S1 symbol
if (_q->num_symbols == 16) {
#if DEBUG_OFDMFRAMESYNC_PRINT
printf("could not find S1 symbol. bailing...\n");
#endif
ofdmframesync_reset(_q);
}
// 'reset' timer (wait another half symbol)
_q->timer = _q->M2;
}
// frame detection
void wlanframesync_execute_seekplcp(wlanframesync _q)
{
_q->timer++;
// TODO : only check every 100 - 150 (decimates/reduced complexity)
if (_q->timer < 64)
return;
// reset timer
_q->timer = 0;
// read contents of input buffer
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
// estimate gain
// TODO : use gain from result of FFT
unsigned int i;
float g = 0.0f;
for (i=16; i<80; i+=4) {
// compute |rc[i]|^2 efficiently
g += crealf(rc[i ])*crealf(rc[i ]) + cimagf(rc[i ])*cimagf(rc[i ]);
g += crealf(rc[i+1])*crealf(rc[i+1]) + cimagf(rc[i+1])*cimagf(rc[i+1]);
g += crealf(rc[i+2])*crealf(rc[i+2]) + cimagf(rc[i+2])*cimagf(rc[i+2]);
g += crealf(rc[i+3])*crealf(rc[i+3]) + cimagf(rc[i+3])*cimagf(rc[i+3]);
}
g = 64.0f / (g + 1e-12f);
// save gain (permits dynamic invocation of get_rssi() method)
_q->g0 = g;
// estimate S0 gain
wlanframesync_estimate_gain_S0(_q, &rc[16], _q->G0a);
// compute S0 metrics
float complex s_hat;
wlanframesync_S0_metrics(_q, _q->G0a, &s_hat);
s_hat *= g;
float tau_hat = cargf(s_hat) * (float)(16.0f) / (2*M_PI);
#if DEBUG_WLANFRAMESYNC_PRINT
printf(" - gain=%12.3f, rssi=%8.2f dB, s_hat=%12.4f <%12.8f>, tau_hat=%8.3f\n",
sqrt(g),
-10*log10(g),
cabsf(s_hat), cargf(s_hat),
tau_hat);
#endif
//
if (cabsf(s_hat) > WLANFRAMESYNC_S0A_ABS_THRESH) {
int dt = (int)roundf(tau_hat);
// set timer appropriately...
_q->timer = (16 + dt) % 16;
//_q->timer += 32; // add delay to help ensure good S0 estimate (multiple of 16)
_q->state = WLANFRAMESYNC_STATE_RXSHORT0;
#if DEBUG_WLANFRAMESYNC_PRINT
printf("********** frame detected! ************\n");
printf(" s_hat : %12.8f <%12.8f>\n", cabsf(s_hat), cargf(s_hat));
printf(" tau_hat : %12.8f\n", tau_hat);
printf(" dt : %12d\n", dt);
printf(" timer : %12u\n", _q->timer);
#endif
}
}
void ofdmframesync_debug_print(ofdmframesync _q,
const char * _filename)
{
#if DEBUG_OFDMFRAMESYNC
if (!_q->debug_objects_created) {
fprintf(stderr,"error: ofdmframe_debug_print(), debugging objects don't exist; enable debugging first\n");
return;
}
FILE * fid = fopen(_filename,"w");
if (!fid) {
fprintf(stderr,"error: ofdmframe_debug_print(), could not open '%s' for writing\n", _filename);
return;
}
fprintf(fid,"%% %s : auto-generated file\n", DEBUG_OFDMFRAMESYNC_FILENAME);
fprintf(fid,"close all;\n");
fprintf(fid,"clear all;\n");
fprintf(fid,"n = %u;\n", DEBUG_OFDMFRAMESYNC_BUFFER_LEN);
fprintf(fid,"M = %u;\n", _q->M);
fprintf(fid,"M_null = %u;\n", _q->M_null);
fprintf(fid,"M_pilot = %u;\n", _q->M_pilot);
fprintf(fid,"M_data = %u;\n", _q->M_data);
unsigned int i;
float complex * rc;
float * r;
// save subcarrier allocation
fprintf(fid,"p = zeros(1,M);\n");
for (i=0; i<_q->M; i++)
fprintf(fid,"p(%4u) = %d;\n", i+1, _q->p[i]);
fprintf(fid,"i_null = find(p==%d);\n", OFDMFRAME_SCTYPE_NULL);
fprintf(fid,"i_pilot = find(p==%d);\n", OFDMFRAME_SCTYPE_PILOT);
fprintf(fid,"i_data = find(p==%d);\n", OFDMFRAME_SCTYPE_DATA);
// short, long, training sequences
for (i=0; i<_q->M; i++) {
fprintf(fid,"S0(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->S0[i]), cimagf(_q->S0[i]));
fprintf(fid,"S1(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->S1[i]), cimagf(_q->S1[i]));
}
fprintf(fid,"x = zeros(1,n);\n");
windowcf_read(_q->debug_x, &rc);
for (i=0; i<DEBUG_OFDMFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(0:(n-1),real(x),0:(n-1),imag(x));\n");
fprintf(fid,"xlabel('sample index');\n");
fprintf(fid,"ylabel('received signal, x');\n");
fprintf(fid,"s1 = [];\n");
for (i=0; i<_q->M; i++)
fprintf(fid,"s1(%3u) = %12.4e + j*%12.4e;\n", i+1, crealf(_q->s1[i]), cimagf(_q->s1[i]));
// write agc_rssi
fprintf(fid,"\n\n");
fprintf(fid,"agc_rssi = zeros(1,%u);\n", DEBUG_OFDMFRAMESYNC_BUFFER_LEN);
windowf_read(_q->debug_rssi, &r);
for (i=0; i<DEBUG_OFDMFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"agc_rssi(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"agc_rssi = filter([0.00362168 0.00724336 0.00362168],[1 -1.82269490 0.83718163],agc_rssi);\n");
fprintf(fid,"agc_rssi = 10*log10( agc_rssi );\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(agc_rssi)\n");
fprintf(fid,"ylabel('RSSI [dB]');\n");
// write short, long symbols
fprintf(fid,"\n\n");
fprintf(fid,"S0 = zeros(1,M);\n");
fprintf(fid,"S1 = zeros(1,M);\n");
for (i=0; i<_q->M; i++) {
fprintf(fid,"S0(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(_q->S0[i]), cimagf(_q->S0[i]));
fprintf(fid,"S1(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(_q->S1[i]), cimagf(_q->S1[i]));
}
// write gain arrays
fprintf(fid,"\n\n");
fprintf(fid,"G0 = zeros(1,M);\n");
fprintf(fid,"G1 = zeros(1,M);\n");
fprintf(fid,"G_hat = zeros(1,M);\n");
fprintf(fid,"G = zeros(1,M);\n");
for (i=0; i<_q->M; i++) {
fprintf(fid,"G0(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(_q->G0[i]), cimagf(_q->G0[i]));
fprintf(fid,"G1(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(_q->G1[i]), cimagf(_q->G1[i]));
fprintf(fid,"G_hat(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(_q->G_hat[i]),cimagf(_q->G_hat[i]));
fprintf(fid,"G(%3u) = %12.8f + j*%12.8f;\n", i+1, crealf(_q->G[i]), cimagf(_q->G[i]));
}
fprintf(fid,"f = [0:(M-1)];\n");
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(f, fftshift(abs(G_hat)),'sb',...\n");
fprintf(fid," f, fftshift(abs(G)),'-k','LineWidth',2);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('subcarrier index');\n");
fprintf(fid," ylabel('gain estimate (mag)');\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(f, fftshift(arg(G_hat).*[abs(G0) > 1e-3]),'sb',...\n");
fprintf(fid," f, fftshift(arg(G)),'-k','LineWidth',2);\n");
fprintf(fid," grid on;\n");
fprintf(fid," xlabel('subcarrier index');\n");
fprintf(fid," ylabel('gain estimate (phase)');\n");
// write pilot response
fprintf(fid,"\n\n");
fprintf(fid,"px = zeros(1,M_pilot);\n");
fprintf(fid,"py = zeros(1,M_pilot);\n");
for (i=0; i<_q->M_pilot; i++) {
fprintf(fid,"px(%3u) = %12.8f;\n", i+1, _q->px[i]);
fprintf(fid,"py(%3u) = %12.8f;\n", i+1, _q->py[i]);
}
fprintf(fid,"p_phase(1) = %12.8f;\n", _q->p_phase[0]);
fprintf(fid,"p_phase(2) = %12.8f;\n", _q->p_phase[1]);
// save pilot history
fprintf(fid,"p0 = zeros(1,M);\n");
windowf_read(_q->debug_pilot_0, &r);
for (i=0; i<DEBUG_OFDMFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"p0(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"p1 = zeros(1,M);\n");
windowf_read(_q->debug_pilot_1, &r);
for (i=0; i<DEBUG_OFDMFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"p1(%4u) = %12.4e;\n", i+1, r[i]);
fprintf(fid,"figure;\n");
fprintf(fid,"fp = (-M/2):(M/2);\n");
fprintf(fid,"subplot(3,1,1);\n");
fprintf(fid," plot(px, py, 'sb',...\n");
fprintf(fid," fp, polyval(p_phase, fp), '-k');\n");
fprintf(fid," grid on;\n");
fprintf(fid," legend('pilots','polyfit',0);\n");
fprintf(fid," xlabel('subcarrier');\n");
fprintf(fid," ylabel('phase');\n");
fprintf(fid,"subplot(3,1,2);\n");
fprintf(fid," plot(1:length(p0), p0);\n");
fprintf(fid," grid on;\n");
fprintf(fid," ylabel('p0 (phase offset)');\n");
fprintf(fid,"subplot(3,1,3);\n");
fprintf(fid," plot(1:length(p1), p1);\n");
fprintf(fid," grid on;\n");
fprintf(fid," ylabel('p1 (phase slope)');\n");
// write frame symbols
fprintf(fid,"framesyms = zeros(1,n);\n");
windowcf_read(_q->debug_framesyms, &rc);
for (i=0; i<DEBUG_OFDMFRAMESYNC_BUFFER_LEN; i++)
fprintf(fid,"framesyms(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(real(framesyms), imag(framesyms), 'x');\n");
fprintf(fid,"xlabel('I');\n");
fprintf(fid,"ylabel('Q');\n");
fprintf(fid,"axis([-1 1 -1 1]*1.6);\n");
fprintf(fid,"axis square;\n");
fprintf(fid,"grid on;\n");
fclose(fid);
printf("ofdmframesync/debug: results written to '%s'\n", _filename);
#else
fprintf(stderr,"ofdmframesync_debug_print(): compile-time debugging disabled\n");
#endif
}
void wlanframesync_execute_rxlong1(wlanframesync _q)
{
_q->timer++;
if (_q->timer < 64)
return;
// run fft
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
// estimate S1 gain, adding backoff in gain estimation
wlanframesync_estimate_gain_S1(_q, &rc[16-2], _q->G1b);
// compute S1 metrics
float complex s_hat;
wlanframesync_S1_metrics(_q, _q->G1b, &s_hat);
s_hat *= _q->g0; // scale output by raw gain estimate
// rotate by complex phasor relative to timing backoff
//s_hat *= cexpf(_Complex_I * 2.0f * 2.0f * M_PI / 64.0f);
s_hat *= cexpf(_Complex_I * 0.19635f);
// save second 'long' symbol statistic
_q->s1b_hat = s_hat;
// rotate by complex phasor relative to timing backoff
//s_hat *= liquid_cexpjf((float)(_q->backoff)*2.0f*M_PI/(float)(_q->M));
#if DEBUG_WLANFRAMESYNC_PRINT
printf(" s_hat : %12.8f <%12.8f>\n", cabsf(s_hat), cargf(s_hat));
#endif
// check conditions for s_hat
float s_hat_abs = cabsf(s_hat);
float s_hat_arg = cargf(s_hat);
if (s_hat_arg > M_PI) s_hat_arg -= 2.0f*M_PI;
if (s_hat_arg < -M_PI) s_hat_arg += 2.0f*M_PI;
// check conditions for s_hat:
// 1. magnitude should be large (near unity) when aligned
// 2. phase should be very near zero (time aligned)
if (s_hat_abs > WLANFRAMESYNC_S1B_ABS_THRESH &&
fabsf(s_hat_arg) < WLANFRAMESYNC_S1B_ARG_THRESH)
{
#if DEBUG_WLANFRAMESYNC_PRINT
printf(" acquisition S1[b]\n");
#endif
// refine CFO estimate with G1a, G1b and adjust NCO appropriately
float nu_hat = wlanframesync_estimate_cfo_S1(_q->G1a, _q->G1b);
nco_crcf_adjust_frequency(_q->nco_rx, nu_hat);
#if DEBUG_WLANFRAMESYNC_PRINT
printf(" nu_hat[1]: %12.8f\n", nu_hat);
#endif
// TODO : de-rotate S1b by phase offset (help with equalizer)
// estimate equalizer with G1a, G1b
wlanframesync_estimate_eqgain_poly(_q);
// set state
_q->state = WLANFRAMESYNC_STATE_RXLONG1;
// reset timer
_q->timer = 0;
}
// set state
_q->state = WLANFRAMESYNC_STATE_RXSIGNAL;
// reset timer
_q->timer = 0;
}
// frame detection
void ofdmframesync_execute_seekplcp(ofdmframesync _q)
{
_q->timer++;
if (_q->timer < _q->M)
return;
// reset timer
_q->timer = 0;
//
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
// estimate gain
unsigned int i;
float g = 0.0f;
for (i=_q->cp_len; i<_q->M + _q->cp_len; i++) {
// compute |rc[i]|^2 efficiently
g += crealf(rc[i])*crealf(rc[i]) + cimagf(rc[i])*cimagf(rc[i]);
}
g = (float)(_q->M) / g;
#if OFDMFRAMESYNC_ENABLE_SQUELCH
// TODO : squelch here
if ( -10*log10f( sqrtf(g) ) < _q->squelch_threshold &&
_q->squelch_enabled)
{
printf("squelch\n");
return;
}
#endif
// estimate S0 gain
ofdmframesync_estimate_gain_S0(_q, &rc[_q->cp_len], _q->G0);
float complex s_hat;
ofdmframesync_S0_metrics(_q, _q->G0, &s_hat);
s_hat *= g;
float tau_hat = cargf(s_hat) * (float)(_q->M2) / (2*M_PI);
#if DEBUG_OFDMFRAMESYNC_PRINT
printf(" - gain=%12.3f, rssi=%12.8f, s_hat=%12.4f <%12.8f>, tau_hat=%8.3f\n",
sqrt(g),
-10*log10(g),
cabsf(s_hat), cargf(s_hat),
tau_hat);
#endif
// save gain (permits dynamic invocation of get_rssi() method)
_q->g0 = g;
//
if (cabsf(s_hat) > _q->plcp_detect_thresh) {
int dt = (int)roundf(tau_hat);
// set timer appropriately...
_q->timer = (_q->M + dt) % (_q->M2);
_q->timer += _q->M; // add delay to help ensure good S0 estimate
_q->state = OFDMFRAMESYNC_STATE_PLCPSHORT0;
#if DEBUG_OFDMFRAMESYNC_PRINT
printf("********** frame detected! ************\n");
printf(" s_hat : %12.8f <%12.8f>\n", cabsf(s_hat), cargf(s_hat));
printf(" tau_hat : %12.8f\n", tau_hat);
printf(" dt : %12d\n", dt);
printf(" timer : %12u\n", _q->timer);
#endif
//printf("exiting prematurely\n");
//ofdmframesync_destroy(_q);
//exit(1);
}
}
// receive data symbols
void wlanframesync_execute_rxdata(wlanframesync _q)
{
_q->timer++;
if (_q->timer < 80)
return;
//printf(" receiving symbol %u...\n", _q->num_symbols);
// reset timer
_q->timer = 0;
// run fft
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
memmove(_q->x, &rc[16-2], 64*sizeof(float complex));
// compute fft, storing result into _q->X
FFT_EXECUTE(_q->fft);
// recover symbol, correcting for gain, pilot phase, etc.
wlanframesync_rxsymbol(_q);
// demodulate and pack
unsigned int i;
unsigned int n=0;
unsigned int sym;
for (i=0; i<64; i++) {
unsigned int k = (i + 32) % 64;
if ( k==0 || (k > 26 && k < 38) ) {
// NULL subcarrier
} else if (k==43 || k==57 || k==7 || k==21) {
// PILOT subcarrier
} else {
// DATA subcarrier
assert(n<48);
sym = wlan_demodulate(_q->mod_scheme, _q->X[k]);
_q->modem_syms[n] = sym;
n++;
#if DEBUG_WLANFRAMESYNC
// TODO : move this outside loop
if (_q->debug_enabled)
windowcf_push(_q->debug_framesyms, _q->X[k]);
#endif
}
}
assert(n==48);
// pack modem symbols
//printf(" %3u = %3u * %3u\n", _q->enc_msg_len, _q->nsym, _q->bytes_per_symbol);
unsigned int num_written;
liquid_wlan_repack_bytes(_q->modem_syms, _q->nbpsc, 48,
&_q->msg_enc[_q->num_symbols * _q->bytes_per_symbol], 8, _q->bytes_per_symbol,
&num_written);
assert(num_written == _q->bytes_per_symbol);
// increment number of received symbols
_q->num_symbols++;
// check number of symbols
if (_q->num_symbols == _q->nsym) {
// decode message
wlan_packet_decode(_q->rate, _q->seed, _q->length, _q->msg_enc, _q->msg_dec);
// assemble RX vector
struct wlan_rxvector_s rxvector;
rxvector.LENGTH = _q->length;
rxvector.RSSI = 200 + (unsigned int) (10*log10f(_q->g0));
rxvector.DATARATE = _q->rate;
rxvector.SERVICE = 0;
// invoke callback
if (_q->callback != NULL) {
//int retval =
_q->callback(_q->msg_dec, rxvector, _q->userdata);
}
// reset and return
wlanframesync_reset(_q);
}
}
// frame detection
void ofdmframesync_execute_S0b(ofdmframesync _q)
{
//printf("t = %u\n", _q->timer);
_q->timer++;
if (_q->timer < _q->M2)
return;
// reset timer
_q->timer = _q->M + _q->cp_len - _q->backoff;
//
float complex * rc;
windowcf_read(_q->input_buffer, &rc);
// estimate S0 gain
ofdmframesync_estimate_gain_S0(_q, &rc[_q->cp_len], _q->G1);
float complex s_hat;
ofdmframesync_S0_metrics(_q, _q->G1, &s_hat);
s_hat *= _q->g0;
_q->s_hat_1 = s_hat;
#if DEBUG_OFDMFRAMESYNC_PRINT
float tau_hat = cargf(s_hat) * (float)(_q->M2) / (2*M_PI);
printf("********** S0[1] received ************\n");
printf(" s_hat : %12.8f <%12.8f>\n", cabsf(s_hat), cargf(s_hat));
printf(" tau_hat : %12.8f\n", tau_hat);
// new timing offset estimate
tau_hat = cargf(_q->s_hat_0 + _q->s_hat_1) * (float)(_q->M2) / (2*M_PI);
printf(" tau_hat * : %12.8f\n", tau_hat);
printf("**********\n");
#endif
// re-adjust timer accordingly
float tau_prime = cargf(_q->s_hat_0 + _q->s_hat_1) * (float)(_q->M2) / (2*M_PI);
_q->timer -= (int)roundf(tau_prime);
#if 0
if (cabsf(s_hat) < 0.3f) {
#if DEBUG_OFDMFRAMESYNC_PRINT
printf("false alarm S0[1]\n");
#endif
// false alarm
ofdmframesync_reset(_q);
return;
}
#endif
float complex g_hat = 0.0f;
unsigned int i;
for (i=0; i<_q->M; i++)
g_hat += _q->G1[i] * conjf(_q->G0[i]);
#if 0
// compute carrier frequency offset estimate using freq. domain method
float nu_hat = 2.0f * cargf(g_hat) / (float)(_q->M);
#else
// compute carrier frequency offset estimate using ML method
float complex t0 = 0.0f;
for (i=0; i<_q->M2; i++) {
t0 += conjf(rc[i]) * _q->s0[i] *
rc[i+_q->M2] * conjf(_q->s0[i+_q->M2]);
}
float nu_hat = cargf(t0) / (float)(_q->M2);
#endif
#if DEBUG_OFDMFRAMESYNC_PRINT
printf(" nu_hat : %12.8f\n", nu_hat);
#endif
// set NCO frequency
nco_crcf_set_frequency(_q->nco_rx, nu_hat);
_q->state = OFDMFRAMESYNC_STATE_PLCPLONG;
}
int main() {
// options
unsigned int num_channels=4; // number of channels
unsigned int m=5; // filter delay
unsigned int num_symbols=12; // number of symbols
// derived values
unsigned int num_samples = num_channels * num_symbols;
unsigned int i;
unsigned int j;
// generate filter
// NOTE : these coefficients can be random; the purpose of this
// exercise is to demonstrate mathematical equivalence
unsigned int h_len = 2*m*num_channels;
float h[h_len];
for (i=0; i<h_len; i++) h[i] = randnf();
//for (i=0; i<h_len; i++) h[i] = 0.1f*i;
//for (i=0; i<h_len; i++) h[i] = (i<=m) ? 1.0f : 0.0f;
//for (i=0; i<h_len; i++) h[i] = 1.0f;
// create filterbank manually
dotprod_crcf dp[num_channels]; // vector dot products
windowcf w[num_channels]; // window buffers
#if DEBUG
// print coefficients
printf("h_prototype:\n");
for (i=0; i<h_len; i++)
printf(" h[%3u] = %12.8f\n", i, h[i]);
#endif
// create objects
unsigned int h_sub_len = 2*m;
float h_sub[h_sub_len];
for (i=0; i<num_channels; i++) {
// sub-sample prototype filter, loading coefficients in
// reverse order
#if 0
for (j=0; j<h_sub_len; j++)
h_sub[j] = h[j*num_channels+i];
#else
for (j=0; j<h_sub_len; j++)
h_sub[h_sub_len-j-1] = h[j*num_channels+i];
#endif
// create window buffer and dotprod objects
dp[i] = dotprod_crcf_create(h_sub, h_sub_len);
w[i] = windowcf_create(h_sub_len);
#if DEBUG
printf("h_sub[%u] : \n", i);
for (j=0; j<h_sub_len; j++)
printf(" h[%3u] = %12.8f\n", j, h_sub[j]);
#endif
}
// generate DFT object
float complex x[num_channels]; // time-domain buffer
float complex X[num_channels]; // freq-domain buffer
#if 0
fftplan fft = fft_create_plan(num_channels, X, x, LIQUID_FFT_BACKWARD, 0);
#else
fftplan fft = fft_create_plan(num_channels, X, x, LIQUID_FFT_FORWARD, 0);
#endif
// generate filter object
firfilt_crcf f = firfilt_crcf_create(h, h_len);
float complex y[num_samples]; // time-domain input
float complex Y0[num_symbols][num_channels]; // channelized output
float complex Y1[num_symbols][num_channels]; // channelized output
// generate input sequence (complex noise)
for (i=0; i<num_samples; i++)
y[i] = randnf() * cexpf(_Complex_I*randf()*2*M_PI);
//
// run analysis filter bank
//
#if 0
unsigned int filter_index = 0;
#else
unsigned int filter_index = num_channels-1;
#endif
float complex y_hat; // input sample
float complex * r; // read pointer
for (i=0; i<num_symbols; i++) {
// load buffers
for (j=0; j<num_channels; j++) {
// grab sample
y_hat = y[i*num_channels + j];
// push sample into buffer at filter index
windowcf_push(w[filter_index], y_hat);
// decrement filter index
filter_index = (filter_index + num_channels - 1) % num_channels;
//filter_index = (filter_index + 1) % num_channels;
}
// execute filter outputs, reversing order of output (not
// sure why this is necessary)
for (j=0; j<num_channels; j++) {
windowcf_read(w[j], &r);
dotprod_crcf_execute(dp[j], r, &X[num_channels-j-1]);
}
// execute DFT, store result in buffer 'x'
fft_execute(fft);
// move to output array
for (j=0; j<num_channels; j++)
Y0[i][j] = x[j];
}
//
// run traditional down-converter (inefficient)
//
float dphi; // carrier frequency
unsigned int n=0;
for (i=0; i<num_channels; i++) {
// reset filter
firfilt_crcf_reset(f);
// set center frequency
dphi = 2.0f * M_PI * (float)i / (float)num_channels;
// reset symbol counter
n=0;
for (j=0; j<num_samples; j++) {
// push down-converted sample into filter
firfilt_crcf_push(f, y[j]*cexpf(-_Complex_I*j*dphi));
// compute output at the appropriate sample time
assert(n<num_symbols);
if ( ((j+1)%num_channels)==0 ) {
firfilt_crcf_execute(f, &Y1[n][i]);
n++;
}
}
assert(n==num_symbols);
}
// destroy objects
for (i=0; i<num_channels; i++) {
dotprod_crcf_destroy(dp[i]);
windowcf_destroy(w[i]);
}
fft_destroy_plan(fft);
firfilt_crcf_destroy(f);
// print filterbank channelizer
printf("\n");
printf("filterbank channelizer:\n");
for (i=0; i<num_symbols; i++) {
printf("%3u: ", i);
for (j=0; j<num_channels; j++) {
printf(" %8.5f+j%8.5f, ", crealf(Y0[i][j]), cimagf(Y0[i][j]));
}
printf("\n");
}
// print traditional channelizer
printf("\n");
printf("traditional channelizer:\n");
for (i=0; i<num_symbols; i++) {
printf("%3u: ", i);
for (j=0; j<num_channels; j++) {
printf(" %8.5f+j%8.5f, ", crealf(Y1[i][j]), cimagf(Y1[i][j]));
}
printf("\n");
}
//
// compare results
//
float mse[num_channels];
float complex d;
for (i=0; i<num_channels; i++) {
mse[i] = 0.0f;
for (j=0; j<num_symbols; j++) {
d = Y0[j][i] - Y1[j][i];
mse[i] += crealf(d*conjf(d));
}
mse[i] /= num_symbols;
}
printf("\n");
printf("rmse: ");
for (i=0; i<num_channels; i++)
printf("%12.4e ", sqrt(mse[i]));
printf("\n");
printf("done.\n");
return 0;
}
// print debugging information
void flexframesync_debug_print(flexframesync _q,
const char * _filename)
{
#if DEBUG_FLEXFRAMESYNC
if (!_q->debug_objects_created) {
fprintf(stderr,"error: flexframesync_debug_print(), debugging objects don't exist; enable debugging first\n");
return;
}
unsigned int i;
float complex * rc;
float * r;
FILE* fid = fopen(_filename,"w");
fprintf(fid,"%% %s: auto-generated file", _filename);
fprintf(fid,"\n\n");
fprintf(fid,"clear all;\n");
fprintf(fid,"close all;\n\n");
fprintf(fid,"n = %u;\n", DEBUG_BUFFER_LEN);
// write x
fprintf(fid,"x = zeros(1,n);\n");
windowcf_read(_q->debug_x, &rc);
for (i=0; i<DEBUG_BUFFER_LEN; i++)
fprintf(fid,"x(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"\n\n");
fprintf(fid,"figure;\n");
fprintf(fid,"plot(1:length(x),real(x), 1:length(x),imag(x));\n");
fprintf(fid,"ylabel('received signal, x');\n");
// write pre-demod sample buffer
fprintf(fid,"k = %u;\n", _q->k);
fprintf(fid,"m = %u;\n", _q->m);
fprintf(fid,"presync_samples = zeros(1,k*(64+m));\n");
windowcf_read(_q->buffer, &rc);
for (i=0; i<_q->k*(64+_q->m); i++)
fprintf(fid,"presync_samples(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
// write p/n sequence
fprintf(fid,"preamble_pn = zeros(1,64);\n");
r = _q->preamble_pn;
for (i=0; i<64; i++)
fprintf(fid,"preamble_pn(%4u) = %12.4e;\n", i+1, r[i]);
// write p/n symbols
fprintf(fid,"preamble_rx = zeros(1,64);\n");
rc = _q->preamble_rx;
for (i=0; i<64; i++)
fprintf(fid,"preamble_rx(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
// write payload symbols
unsigned int num_payload_syms = _q->payload_mod_len > 256 ? 256 : _q->payload_mod_len;
fprintf(fid,"payload_syms = zeros(1,%u);\n", num_payload_syms);
rc = _q->payload_sym;
for (i=0; i<num_payload_syms; i++)
fprintf(fid,"payload_syms(%4u) = %12.4e + j*%12.4e;\n", i+1, crealf(rc[i]), cimagf(rc[i]));
fprintf(fid,"figure;\n");
fprintf(fid,"plot(real(payload_syms),imag(payload_syms),'x',...\n");
fprintf(fid," real(preamble_rx), imag(preamble_rx), 'x');\n");
fprintf(fid,"xlabel('in-phase');\n");
fprintf(fid,"ylabel('quadrature phase');\n");
fprintf(fid,"legend('p/n syms','payload syms','location','northeast');\n");
fprintf(fid,"grid on;\n");
fprintf(fid,"axis([-1 1 -1 1]*1.5);\n");
fprintf(fid,"axis square;\n");
#if 0
// NCO, timing, etc.
fprintf(fid,"symsync_index = zeros(1,664);\n");
fprintf(fid,"nco_phase = zeros(1,664);\n");
for (i=0; i<664; i++) {
fprintf(fid,"symsync_index(%4u) = %12.4e;\n", i+1, _q->debug_symsync_index[i]);
fprintf(fid,"nco_phase(%4u) = %12.4e;\n", i+1, _q->debug_nco_phase[i]);
}
fprintf(fid,"figure;\n");
fprintf(fid,"subplot(2,1,1);\n");
fprintf(fid," plot(nco_phase);\n");
fprintf(fid," ylabel('nco phase');\n");
fprintf(fid," grid on;\n");
fprintf(fid,"subplot(2,1,2);\n");
fprintf(fid," plot(symsync_index);\n");
fprintf(fid," ylabel('symsync index');\n");
fprintf(fid," grid on;\n");
#endif
fprintf(fid,"\n\n");
fclose(fid);
printf("flexframesync/debug: results written to %s\n", _filename);
#else
fprintf(stderr,"flexframesync_debug_print(): compile-time debugging disabled\n");
#endif
}
// main program
int main (int argc, char **argv)
{
// command-line options
int verbose = 1;
int ppm_error = 0;
int gain = 0;
unsigned int nfft = 64;
float offset = -65.0f;
float scale = 5.0f;
float fft_rate = 10.0f;
float rx_resamp_rate;
float bandwidth = 800e3f;
unsigned int logsize = 4096;
char filename[256] = "rtl_asgram.dat";
int r, n_read;
uint32_t frequency = 100000000;
uint32_t samp_rate = DEFAULT_SAMPLE_RATE;
uint32_t out_block_size = DEFAULT_BUF_LENGTH;
uint8_t *buffer;
int dev_index = 0;
int dev_given = 0;
struct sigaction sigact;
normalizer_t *norm;
//
int d;
while ((d = getopt(argc,argv,"hf:b:B:G:n:p:s:o:r:L:F:")) != EOF) {
switch (d) {
case 'h':
usage();
return 0;
case 'f':
frequency = atof(optarg);
break;
case 'b':
bandwidth = atof(optarg);
break;
case 'B':
out_block_size = (uint32_t)atof(optarg);
break;
case 'G':
gain = (int)(atof(optarg) * 10);
break;
case 'n':
nfft = atoi(optarg);
break;
case 'o':
offset = atof(optarg);
break;
case 'p':
ppm_error = atoi(optarg);
break;
case 's':
samp_rate = (uint32_t)atofs(optarg);
break;
case 'r':
fft_rate = atof(optarg);
break;
case 'L':
logsize = atoi(optarg);
break;
case 'F':
strncpy(filename,optarg,255);
break;
case 'd':
dev_index = verbose_device_search(optarg);
dev_given = 1;
break;
default:
usage();
return 1;
}
}
// validate parameters
if (fft_rate <= 0.0f || fft_rate > 100.0f) {
fprintf(stderr,"error: %s, fft rate must be in (0, 100) Hz\n", argv[0]);
exit(1);
}
if (!dev_given) {
dev_index = verbose_device_search("0");
}
if (dev_index < 0) {
exit(1);
}
r = rtlsdr_open(&dev, (uint32_t)dev_index);
if (r < 0) {
fprintf(stderr, "Failed to open rtlsdr device #%d.\n", dev_index);
exit(1);
}
sigact.sa_handler = sighandler;
sigemptyset(&sigact.sa_mask);
sigact.sa_flags = 0;
sigaction(SIGINT, &sigact, NULL);
sigaction(SIGTERM, &sigact, NULL);
sigaction(SIGQUIT, &sigact, NULL);
sigaction(SIGPIPE, &sigact, NULL);
/* Set the sample rate */
verbose_set_sample_rate(dev, samp_rate);
/* Set the frequency */
verbose_set_frequency(dev, frequency);
if (0 == gain) {
/* Enable automatic gain */
verbose_auto_gain(dev);
} else {
/* Enable manual gain */
gain = nearest_gain(dev, gain);
verbose_gain_set(dev, gain);
}
verbose_ppm_set(dev, ppm_error);
rx_resamp_rate = bandwidth/samp_rate;
printf("frequency : %10.4f [MHz]\n", frequency*1e-6f);
printf("bandwidth : %10.4f [kHz]\n", bandwidth*1e-3f);
printf("sample rate : %10.4f kHz = %10.4f kHz * %8.6f\n",
samp_rate * 1e-3f,
bandwidth * 1e-3f,
1.0f / rx_resamp_rate);
printf("verbosity : %s\n", (verbose?"enabled":"disabled"));
unsigned int i;
// add arbitrary resampling component
msresamp_crcf resamp = msresamp_crcf_create(rx_resamp_rate, 60.0f);
assert(resamp);
// create buffer for sample logging
windowcf log = windowcf_create(logsize);
// create ASCII spectrogram object
float maxval;
float maxfreq;
char ascii[nfft+1];
ascii[nfft] = '\0'; // append null character to end of string
asgram q = asgram_create(nfft);
asgram_set_scale(q, offset, scale);
// assemble footer
unsigned int footer_len = nfft + 16;
char footer[footer_len+1];
for (i=0; i<footer_len; i++)
footer[i] = ' ';
footer[1] = '[';
footer[nfft/2 + 3] = '+';
footer[nfft + 4] = ']';
sprintf(&footer[nfft+6], "%8.3f MHz", frequency*1e-6f);
unsigned int msdelay = 1000 / fft_rate;
// create/initialize Hamming window
float w[nfft];
for (i=0; i<nfft; i++)
w[i] = hamming(i,nfft);
//allocate recv buffer
buffer = malloc(out_block_size * sizeof(uint8_t));
assert(buffer);
// create buffer for arbitrary resamper output
int b_len = ((int)(out_block_size * rx_resamp_rate) + 64) >> 1;
complex float buffer_resamp[b_len];
debug("resamp_buffer_len: %d", b_len);
// timer to control asgram output
timer t1 = timer_create();
timer_tic(t1);
norm = normalizer_create();
verbose_reset_buffer(dev);
while (!do_exit) {
// grab data from device
r = rtlsdr_read_sync(dev, buffer, out_block_size, &n_read);
if (r < 0) {
fprintf(stderr, "WARNING: sync read failed.\n");
break;
}
if ((bytes_to_read > 0) && (bytes_to_read < (uint32_t)n_read)) {
n_read = bytes_to_read;
do_exit = 1;
}
// push data through arbitrary resampler and give to frame synchronizer
// TODO : apply bandwidth-dependent gain
for (i=0; i<n_read/2; i++) {
// grab sample from usrp buffer
complex float rtlsdr_sample = normalizer_normalize(norm, *((uint16_t*)buffer+i));
// push through resampler (one at a time)
unsigned int nw;
msresamp_crcf_execute(resamp, &rtlsdr_sample, 1, buffer_resamp, &nw);
// push resulting samples into asgram object
asgram_push(q, buffer_resamp, nw);
// write samples to log
windowcf_write(log, buffer_resamp, nw);
}
if ((uint32_t)n_read < out_block_size) {
fprintf(stderr, "Short read, samples lost, exiting!\n");
break;
}
if (bytes_to_read > 0)
bytes_to_read -= n_read;
if (timer_toc(t1) > msdelay*1e-3f) {
// reset timer
timer_tic(t1);
// run the spectrogram
asgram_execute(q, ascii, &maxval, &maxfreq);
// print the spectrogram
printf(" > %s < pk%5.1fdB [%5.2f]\n", ascii, maxval, maxfreq);
printf("%s\r", footer);
fflush(stdout);
}
}
// try to write samples to file
FILE * fid = fopen(filename,"w");
if (fid != NULL) {
// write header
fprintf(fid, "# %s : auto-generated file\n", filename);
fprintf(fid, "#\n");
fprintf(fid, "# num_samples : %u\n", logsize);
fprintf(fid, "# frequency : %12.8f MHz\n", frequency*1e-6f);
fprintf(fid, "# bandwidth : %12.8f kHz\n", bandwidth*1e-3f);
// save results to file
complex float * rc; // read pointer
windowcf_read(log, &rc);
for (i=0; i<logsize; i++)
fprintf(fid, "%12.4e %12.4e\n", crealf(rc[i]), cimagf(rc[i]));
// close it up
fclose(fid);
printf("results written to '%s'\n", filename);
} else {
fprintf(stderr,"error: %s, could not open '%s' for writing\n", argv[0], filename);
}
// destroy objects
normalizer_destroy(&norm);
msresamp_crcf_destroy(resamp);
windowcf_destroy(log);
asgram_destroy(q);
timer_destroy(t1);
rtlsdr_close(dev);
free (buffer);
return 0;
}
