// estimate long sequence gain
// _q : ofdmframesync object
// _x : input array (time), [size: M x 1]
// _G : output gain (freq)
void ofdmframesync_estimate_gain_S1(ofdmframesync _q,
float complex * _x,
float complex * _G)
{
// move input array into fft input buffer
memmove(_q->x, _x, (_q->M)*sizeof(float complex));
// compute fft, storing result into _q->X
FFT_EXECUTE(_q->fft);
// compute gain, ignoring NULL subcarriers
unsigned int i;
float gain = sqrtf(_q->M_S1) / (float)(_q->M);
for (i=0; i<_q->M; i++) {
if (_q->p[i] != OFDMFRAME_SCTYPE_NULL) {
// NOTE : if cabsf(_q->S1[i]) == 0 then we can multiply by conjugate
// rather than compute division
//_G[i] = _q->X[i] / _q->S1[i];
_G[i] = _q->X[i] * conjf(_q->S1[i]);
} else {
_G[i] = 0.0f;
}
// normalize gain
_G[i] *= gain;
}
}
// write OFDM symbol
// _q : framing generator object
// _x : input symbols, [size: _M x 1]
// _y : output samples, [size: _M x 1]
void ofdmframegen_writesymbol(ofdmframegen _q,
float complex * _x,
float complex * _y)
{
// move frequency data to internal buffer
unsigned int i;
unsigned int k;
int sctype;
for (i=0; i<_q->M; i++) {
// start at mid-point (effective fftshift)
k = (i + _q->M/2) % _q->M;
sctype = _q->p[k];
if (sctype==OFDMFRAME_SCTYPE_NULL) {
// disabled subcarrier
_q->X[k] = 0.0f;
} else if (sctype==OFDMFRAME_SCTYPE_PILOT) {
// pilot subcarrier
_q->X[k] = (msequence_advance(_q->ms_pilot) ? 1.0f : -1.0f) * _q->g_data;
} else {
// data subcarrier
_q->X[k] = _x[k] * _q->g_data;
}
//printf("X[%3u] = %12.8f + j*%12.8f;\n",i+1,crealf(_q->X[i]),cimagf(_q->X[i]));
}
// execute transform
FFT_EXECUTE(_q->ifft);
// copy result to output, adding cyclic prefix and tapering window
ofdmframegen_gensymbol(_q, _y);
}
// estimate long sequence gain
// _q : wlanframesync object
// _x : input array (time), [size: M x 1]
// _G : output gain (freq)
void wlanframesync_estimate_gain_S1(wlanframesync _q,
float complex * _x,
float complex * _G)
{
// move input array into fft input buffer
memmove(_q->x, _x, 64*sizeof(float complex));
// compute fft, storing result into _q->X
FFT_EXECUTE(_q->fft);
// nominal gain (normalization factor)
float gain = 0.11267f; // sqrt(52)/64 ; sqrtf(_q->M_S1) / (float)(_q->M);
// compute gain, ignoring NULL subcarriers
unsigned int i;
for (i=0; i<64; i++) {
if (i == 0 || (i>26 && i<38) ) {
// NULL subcarrier
_G[i] = 0.0f;
} else {
// DATA/PILOT subcarrier (S1 enabled)
_G[i] = _q->X[i] * conjf(wlanframe_S1[i]) * gain;
}
}
}
// demodulate symbol, assuming perfect symbol timing
// _q : fskdem object
// _y : input sample array [size: _k x 1]
unsigned int fskdem_demodulate(fskdem _q,
float complex * _y)
{
// copy input to internal time buffer
memmove(_q->buf_time, _y, _q->k*sizeof(float complex));
// compute transform, storing result in 'buf_freq'
FFT_EXECUTE(_q->fft);
// find maximum by looking at particular bins
float vmax = 0;
unsigned int s = 0;
// run search
for (s=0; s<_q->M; s++) {
float v = cabsf( _q->buf_freq[_q->demod_map[s]] );
if (s==0 || v > vmax) {
// save optimal output symbol
_q->s_demod = s;
// save peak FFT bin value
vmax = v;
}
}
// save best result
return _q->s_demod;
}
// estimate short sequence gain
// _q : wlanframesync object
// _x : input array (time), [size: M x 1]
// _G : output gain (freq)
void wlanframesync_estimate_gain_S0(wlanframesync _q,
float complex * _x,
float complex * _G)
{
// move input array into fft input buffer
memmove(_q->x, _x, 64*sizeof(float complex));
// compute fft, storing result into _q->X
FFT_EXECUTE(_q->fft);
// compute gain, ignoring NULL subcarriers
unsigned int i;
float gain = 0.054127f; // sqrt(12)/64 ; sqrtf(_q->M_S0) / (float)(_q->M);
// clear input
for (i=0; i<64; i++) _G[i] = 0.0f;
// NOTE : if cabsf(_q->S0[i]) == 0 then we can multiply by conjugate
// rather than compute division
//_G[i] = _q->X[i] / _q->S0[i];
_G[40] = _q->X[40] * conjf(wlanframe_S0[40]) * gain;
_G[44] = _q->X[44] * conjf(wlanframe_S0[44]) * gain;
_G[48] = _q->X[48] * conjf(wlanframe_S0[48]) * gain;
_G[52] = _q->X[52] * conjf(wlanframe_S0[52]) * gain;
_G[56] = _q->X[56] * conjf(wlanframe_S0[56]) * gain;
_G[60] = _q->X[60] * conjf(wlanframe_S0[60]) * gain;
//
_G[ 4] = _q->X[ 4] * conjf(wlanframe_S0[ 4]) * gain;
_G[ 8] = _q->X[ 8] * conjf(wlanframe_S0[ 8]) * gain;
_G[12] = _q->X[12] * conjf(wlanframe_S0[12]) * gain;
_G[16] = _q->X[16] * conjf(wlanframe_S0[16]) * gain;
_G[20] = _q->X[20] * conjf(wlanframe_S0[20]) * gain;
_G[24] = _q->X[24] * conjf(wlanframe_S0[24]) * gain;
}
// estimate complex equalizer gain from G0 and G1
// _q : ofdmframesync object
// _ntaps : number of time-domain taps for smoothing
void ofdmframesync_estimate_eqgain(ofdmframesync _q,
unsigned int _ntaps)
{
#if DEBUG_OFDMFRAMESYNC
if (_q->debug_enabled) {
// copy pre-smoothed gain
memmove(_q->G_hat, _q->G, _q->M*sizeof(float complex));
}
#endif
// validate input
if (_ntaps == 0 || _ntaps > _q->M) {
fprintf(stderr, "error: ofdmframesync_estimate_eqgain(), ntaps must be in [1,M]\n");
exit(1);
}
unsigned int i;
// generate smoothing window (fft of temporal window)
for (i=0; i<_q->M; i++)
_q->x[i] = (i < _ntaps) ? 1.0f : 0.0f;
FFT_EXECUTE(_q->fft);
memmove(_q->G0, _q->G, _q->M*sizeof(float complex));
// smooth complex equalizer gains
for (i=0; i<_q->M; i++) {
// set gain to zero for null subcarriers
if (_q->p[i] == OFDMFRAME_SCTYPE_NULL) {
_q->G[i] = 0.0f;
continue;
}
float complex w;
float complex w0 = 0.0f;
float complex G_hat = 0.0f;
unsigned int j;
for (j=0; j<_q->M; j++) {
if (_q->p[j] == OFDMFRAME_SCTYPE_NULL) continue;
// select window sample from array
w = _q->X[(i + _q->M - j) % _q->M];
// accumulate gain
//G_hat += w * 0.5f * (_q->G0[j] + _q->G1[j]);
G_hat += w * _q->G0[j];
w0 += w;
}
// eliminate divide-by-zero issues
if (cabsf(w0) < 1e-4f) {
fprintf(stderr,"error: ofdmframesync_estimate_eqgain(), weighting factor is zero\n");
w0 = 1.0f;
}
_q->G[i] = G_hat / w0;
}
}
void firpfbch_analyzer_run(firpfbch _c, float complex * _y)
{
// NOTE: The analyzer is different from the synthesizer in
// that the invocation of the commutator results in a
// delay from the first input sample to the resulting
// partitions. As a result, the inverse DFT is
// invoked after the first filter is run, after which
// the remaining filters are executed.
// restore saved IDFT input state X from X_prime
memmove(_c->X, _c->X_prime, (_c->num_channels)*sizeof(float complex));
unsigned int i, b;
unsigned int k = _c->filter_index;
// push first value and compute output
float complex * r;
WINDOW(_read)(_c->w[k], &r);
DOTPROD(_execute)(_c->dp[0], r, &(_c->X[0]));
// execute inverse fft, store in buffer _c->x
FFT_EXECUTE(_c->fft);
// copy results to output buffer
memmove(_y, _c->x, (_c->num_channels)*sizeof(float complex));
// push remaining samples into filter bank and execute in
// *reverse* order, putting result into the inverse DFT
// input buffer _c->X
//for (i=1; i<_c->num_channels; i++) {
// NOTE : the filter window buffers have already been loaded
// in the proper reverse order, so there is no need
// to execute the dot products in any particular order,
// so long as they are aligned with the proper input
// buffer.
for (i=1; i<_c->num_channels; i++) {
b = (k+i) % _c->num_channels;
WINDOW(_read)(_c->w[b], &r);
DOTPROD(_execute)(_c->dp[i], r, &(_c->X[i]));
}
}
void FFTransformer::fillComplexSub()
{
auto plan = FFT_CREATE_PLAN(m_bufferSize, m_complexSub, m_complexSub, FFTW_FORWARD, FFTW_ESTIMATE);
double speed = Options::getInstance()->getSignalSpeed();
double rxRate = Options::getInstance()->getBand();
for(size_t i = 0; i < m_bufferSize; i++)
{
double t = i / rxRate;
t *= t;
auto iter = *(m_complexSub + i);
iter[0] = cos(M_PI * t * speed);
iter[1] = sin(M_PI * t * speed);
}
FFT_EXECUTE(plan);
for(size_t i = 0; i < m_bufferSize; i++)
m_complexSub[i][1] *= -1;
FFT_DESTROY_PLAN(plan);
}
void firpfbch_synthesizer_execute(firpfbch _c, float complex * _x, float complex * _y)
{
unsigned int i;
// copy samples into ifft input buffer _c->X
memmove(_c->X, _x, (_c->num_channels)*sizeof(float complex));
// execute inverse fft, store in buffer _c->x
FFT_EXECUTE(_c->fft);
// push samples into filter bank and execute, putting
// samples into output buffer _y
float complex * r;
for (i=0; i<_c->num_channels; i++) {
WINDOW(_push)(_c->w[i], _c->x[i]);
WINDOW(_read)(_c->w[i], &r);
DOTPROD(_execute)(_c->dp[i], r, &(_y[i]));
// invoke scaling factor
_y[i] /= (float)(_c->num_channels);
}
}
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;
}
}
// 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);
}
}
// 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;
}
// create FFT-based FIR filter using external coefficients
// _h : filter coefficients [size: _h_len x 1]
// _h_len : filter length, _h_len > 0
// _n : block size = nfft/2, at least _h_len-1
FFTFILT() FFTFILT(_create)(TC * _h,
unsigned int _h_len,
unsigned int _n)
{
// validate input
if (_h_len == 0) {
fprintf(stderr,"error: fftfilt_%s_create(), filter length must be greater than zero\n",
EXTENSION_FULL);
exit(1);
} else if (_n < _h_len-1) {
fprintf(stderr,"error: fftfilt_%s_create(), block length must be greater than _h_len-1 (%u)\n",
EXTENSION_FULL,
_h_len-1);
exit(1);
}
// create filter object and initialize
FFTFILT() q = (FFTFILT()) malloc(sizeof(struct FFTFILT(_s)));
q->h_len = _h_len;
q->n = _n;
// copy filter coefficients
q->h = (TC *) malloc((q->h_len)*sizeof(TC));
memmove(q->h, _h, _h_len*sizeof(TC));
// allocate internal memory arrays
q->time_buf = (float complex *) malloc((2*q->n)* sizeof(float complex)); // time buffer
q->freq_buf = (float complex *) malloc((2*q->n)* sizeof(float complex)); // frequency buffer
q->H = (float complex *) malloc((2*q->n)* sizeof(float complex)); // FFT{ h }
q->w = (float complex *) malloc(( q->n)* sizeof(float complex)); // delay buffer
// create internal FFT objects
#ifdef LIQUID_FFTOVERRIDE
q->fft = fft_create_plan(2*q->n, q->time_buf, q->freq_buf, LIQUID_FFT_FORWARD, 0);
q->ifft = fft_create_plan(2*q->n, q->freq_buf, q->time_buf, LIQUID_FFT_BACKWARD, 0);
#else
q->fft = FFT_CREATE_PLAN(2*q->n, q->time_buf, q->freq_buf, FFT_DIR_FORWARD, FFT_METHOD);
q->ifft = FFT_CREATE_PLAN(2*q->n, q->freq_buf, q->time_buf, FFT_DIR_BACKWARD, FFT_METHOD);
#endif
// compute FFT of filter coefficients and copy to internal H array
unsigned int i;
for (i=0; i<2*q->n; i++)
q->time_buf[i] = (i < q->h_len) ? q->h[i] : 0;
// time_buf > {FFT} > freq_buf
#ifdef LIQUID_FFTOVERRIDE
fft_execute(q->fft);
#else
FFT_EXECUTE(q->fft);
#endif
memmove(q->H, q->freq_buf, 2*q->n*sizeof(float complex));
// set default scaling
FFTFILT(_set_scale)(q, 1);
// reset filter state (clear buffer)
FFTFILT(_reset)(q);
// return object
return q;
}
