// Help function to keep code base small
void modem_test_demodsoft(modulation_scheme _ms)
{
// generate mod/demod
modem mod = modem_create(_ms);
modem demod = modem_create(_ms);
//
unsigned int bps = modem_get_bps(demod);
// run the test
unsigned int i, s, M=1<<bps;
unsigned int sym_soft;
unsigned char soft_bits[bps];
float complex x;
for (i=0; i<M; i++) {
// modulate symbol
modem_modulate(mod, i, &x);
// demodulate using soft-decision
modem_demodulate_soft(demod, x, &s, soft_bits);
// check hard-decision output
CONTEND_EQUALITY(s, i);
// check soft bits
liquid_pack_soft_bits(soft_bits, bps, &sym_soft);
CONTEND_EQUALITY(sym_soft, i);
// check phase error, evm, etc.
//CONTEND_DELTA( modem_get_demodulator_phase_error(demod), 0.0f, 1e-3f);
//CONTEND_DELTA( modem_get_demodulator_evm(demod), 0.0f, 1e-3f);
}
// clean it up
modem_destroy(mod);
modem_destroy(demod);
}
// receive header data
void ofdmflexframesync_rxheader(ofdmflexframesync _q,
float complex * _X)
{
#if DEBUG_OFDMFLEXFRAMESYNC
printf(" ofdmflexframesync extracting header...\n");
#endif
// demodulate header symbols
unsigned int i;
int sctype;
for (i=0; i<_q->M; i++) {
// subcarrier type (PILOT/NULL/DATA)
sctype = _q->p[i];
// ignore pilot and null subcarriers
if (sctype == OFDMFRAME_SCTYPE_DATA) {
// unload header symbols
// demodulate header symbol
unsigned int sym;
#if OFDMFLEXFRAME_H_SOFT
modem_demodulate_soft(_q->mod_header, _X[i], &sym, &_q->header_mod[OFDMFLEXFRAME_H_BPS*_q->header_symbol_index]);
#else
modem_demodulate(_q->mod_header, _X[i], &sym);
_q->header_mod[_q->header_symbol_index] = sym;
#endif
_q->header_symbol_index++;
//printf(" extracting symbol %3u / %3u (x = %8.5f + j%8.5f)\n", _q->header_symbol_index, OFDMFLEXFRAME_H_SYM, crealf(_X[i]), cimagf(_X[i]));
// get demodulator error vector magnitude
float evm = modem_get_demodulator_evm(_q->mod_header);
_q->evm_hat += evm*evm;
// header extracted
if (_q->header_symbol_index == OFDMFLEXFRAME_H_SYM) {
// decode header
ofdmflexframesync_decode_header(_q);
// compute error vector magnitude estimate
_q->framestats.evm = 10*log10f( _q->evm_hat/OFDMFLEXFRAME_H_SYM );
// invoke callback if header is invalid
if (_q->header_valid)
_q->state = OFDMFLEXFRAMESYNC_STATE_PAYLOAD;
else {
//printf("**** header invalid!\n");
// set framestats internals
_q->framestats.rssi = ofdmframesync_get_rssi(_q->fs);
_q->framestats.cfo = ofdmframesync_get_cfo(_q->fs);
_q->framestats.framesyms = NULL;
_q->framestats.num_framesyms = 0;
_q->framestats.mod_scheme = LIQUID_MODEM_UNKNOWN;
_q->framestats.mod_bps = 0;
_q->framestats.check = LIQUID_CRC_UNKNOWN;
_q->framestats.fec0 = LIQUID_FEC_UNKNOWN;
_q->framestats.fec1 = LIQUID_FEC_UNKNOWN;
// invoke callback method
_q->callback(_q->header,
_q->header_valid,
NULL,
0,
0,
_q->framestats,
_q->userdata);
ofdmflexframesync_reset(_q);
}
break;
}
}
}
}
// execute synchronizer, receiving header
// _q : frame synchronizer object
// _x : input sample
void flexframesync_execute_rxheader(flexframesync _q,
float complex _x)
{
// mix signal down
float complex y;
nco_crcf_mix_down(_q->nco_coarse, _x*0.5f/_q->gamma_hat, &y);
nco_crcf_step(_q->nco_coarse);
// update symbol synchronizer
float complex mf_out = 0.0f;
int sample_available = flexframesync_update_symsync(_q, y, &mf_out);
// compute output if timeout
if (sample_available) {
// push through fine-tuned nco
nco_crcf_mix_down(_q->nco_fine, mf_out, &mf_out);
#if DEBUG_FLEXFRAMESYNC
if (_q->debug_enabled)
_q->header_sym[_q->header_counter] = mf_out;
#endif
// demodulate
unsigned int sym_out = 0;
#if DEMOD_HEADER_SOFT
unsigned char bpsk_soft_bit = 0;
modem_demodulate_soft(_q->demod_header, mf_out, &sym_out, &bpsk_soft_bit);
_q->header_mod[_q->header_counter] = bpsk_soft_bit;
#else
modem_demodulate(_q->demod_header, mf_out, &sym_out);
_q->header_mod[_q->header_counter] = (unsigned char)sym_out;
#endif
// update phase-locked loop and fine-tuned NCO
float phase_error = modem_get_demodulator_phase_error(_q->demod_header);
nco_crcf_pll_step(_q->nco_fine, phase_error);
nco_crcf_step(_q->nco_fine);
// update error vector magnitude
float evm = modem_get_demodulator_evm(_q->demod_header);
_q->framestats.evm += evm*evm;
// increment counter
_q->header_counter++;
if (_q->header_counter == FLEXFRAME_H_SYM) {
// decode header and invoke callback
flexframesync_decode_header(_q);
// invoke callback if header is invalid
if (!_q->header_valid && _q->callback != NULL) {
// set framestats internals
_q->framestats.evm = 20*log10f(sqrtf(_q->framestats.evm / FLEXFRAME_H_SYM));
_q->framestats.rssi = 20*log10f(_q->gamma_hat);
_q->framestats.cfo = nco_crcf_get_frequency(_q->nco_coarse) +
nco_crcf_get_frequency(_q->nco_fine) / 2.0f; //(float)(_q->k);
_q->framestats.framesyms = NULL;
_q->framestats.num_framesyms = 0;
_q->framestats.mod_scheme = LIQUID_MODEM_UNKNOWN;
_q->framestats.mod_bps = 0;
_q->framestats.check = LIQUID_CRC_UNKNOWN;
_q->framestats.fec0 = LIQUID_FEC_UNKNOWN;
_q->framestats.fec1 = LIQUID_FEC_UNKNOWN;
// invoke callback method
_q->callback(_q->header,
_q->header_valid,
NULL,
0,
0,
_q->framestats,
_q->userdata);
}
if (!_q->header_valid) {
flexframesync_reset(_q);
return;
}
// update state
_q->state = STATE_RXPAYLOAD;
}
}
}
