static void dft(struct OFDM *, complex float *, complex float *);
static void idft(struct OFDM *, complex float *, complex float *);
static complex float vector_sum(complex float *, int);
-static int coarse_sync(struct OFDM *, complex float *, int, float *foff_est);
+static int coarse_sync(struct OFDM *, complex float *, int, float *);
/* Defines */
result[row] = result[row] + (vector[col] * ofdm->W[col][row]);
}
- result[row] = result[row] * (1.0f / (float) OFDM_M);
+ result[row] = result[row] * OFDM_INVERSE_M;
}
}
/* Calculate sample rate of phase samples, we are sampling phase
of pilot at half a symbol intervals */
- float Fs1 = Fs/((OFDM_M + OFDM_NCP)/2);
+ float Fs1 = Fs / ((OFDM_M + OFDM_NCP)/2);
/* subtract phase of adjacent samples, rate of change of phase is
frequency est. We combine samples from either end of frame to
improve estimate. Small real 1E-12 term to prevent instability
with 0 inputs. */
- *foff_est = Fs1 * cargf(conjf(p1)*p2 + conjf(p3)*p4 + 1E-12f) / TAU;
+ *foff_est = Fs1 * cargf(conjf(p1) * p2 + conjf(p3) * p4 + 1E-12f) / TAU;
return timing_est;
}
* ----------------------------------------------
*/
-void ofdm_txframe(
- struct OFDM *ofdm,
- complex float tx[OFDM_SAMPLESPERFRAME],
- complex float *tx_sym_lin)
-{
+void ofdm_txframe(struct OFDM *ofdm, complex float tx[OFDM_SAMPLESPERFRAME], complex float *tx_sym_lin) {
complex float aframe[OFDM_NS][OFDM_NC + 2];
complex float asymbol[OFDM_M];
complex float asymbol_cp[OFDM_M + OFDM_NCP];
/* store complex BPSK pilot symbols */
assert(sizeof(pilotvalues) == (OFDM_NC+2));
+
for (i = 0; i < (OFDM_NC + 2); i++) {
ofdm->pilots[i] = ((float) pilotvalues[i]) + 0.0f * I;
}
for (i = 0, n = Nlower; i < (OFDM_NC + 2); i++, n++) {
float w = (TAU * (float) n) / (OFDM_FS / OFDM_RS);
+
for (j = 0; j < OFDM_M; j++) {
ofdm->W[i][j] = cexpf(I * w * j);
}
ofdm->timing_valid = 0;
ofdm->timing_mx = 0.0f;
ofdm->nin = OFDM_SAMPLESPERFRAME;
- ofdm->foff_running = 0.0 + I*0.0;
+ ofdm->foff_running = 0.0f + 0.0f * I;
/* sync state machine */
- for(i=0; i<OFDM_NUWBITS; i++) {
+ for (i = 0; i < OFDM_NUWBITS; i++) {
ofdm->tx_uw[i] = tx_uw[i];
}
+
strcpy(ofdm->sync_state,"search");
strcpy(ofdm->last_sync_state,"search");
ofdm->uw_errors = 0;
ofdm->pilot_samples[i] = temp[j];
}
- // states.timing_norm = Npsam*(rate_fs_pilot_samples*rate_fs_pilot_samples');
+ // From Octave: states.timing_norm = Npsam*(rate_fs_pilot_samples*rate_fs_pilot_samples');
/* Now copy the whole thing after the above */
float acc = 0.0f;
- for (i = 0; i < OFDM_M+OFDM_NCP; i++) {
+ for (i = 0; i < (OFDM_M + OFDM_NCP); i++) {
acc += (crealf(ofdm->pilot_samples[i]) * crealf(ofdm->pilot_samples[i]) +
cimagf(ofdm->pilot_samples[i]) * cimagf(ofdm->pilot_samples[i]));
}
//fprintf(stderr, "timing_norm: %f\n", ofdm->timing_norm);
- ofdm->sig_var = ofdm->noise_var = 1.0;
+ ofdm->sig_var = ofdm->noise_var = 1.0f;
return ofdm; /* Success */
}
/*
* Convert the time-domain samples to the frequency-domain using the rx_sym
- * data matrix. This will be 18 carriers of 11 symbols.
+ * data matrix. This will be Nc+2 carriers of 11 symbols.
*
- * You will notice there are 18 BPSK symbols for each pilot symbol, and that there
- * are 16 QPSK symbols for each data symbol.
+ * You will notice there are Nc+2 BPSK symbols for each pilot symbol, and that there
+ * are Nc QPSK symbols for each data symbol.
*
- * XXXXXXXXXXXXXXXX <-- Timing Slip
- * PPPPPPPPPPPPPPPPPP <-- Previous Frames Pilot
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD Ignore these past data symbols
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * PPPPPPPPPPPPPPPPPP <-- This Frames Pilot
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD These are the current data symbols to be decoded
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * PPPPPPPPPPPPPPPPPP <-- Next Frames Pilot
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD Ignore these next data symbols
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * DDDDDDDDDDDDDDDD
- * PPPPPPPPPPPPPPPPPP <-- Future Frames Pilot
- * XXXXXXXXXXXXXXXX <-- Timing Slip
+ * XXXXXXXXXXXXXXXXX <-- Timing Slip
+ * PPPPPPPPPPPPPPPPPPP <-- Previous Frames Pilot
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD Ignore these past data symbols
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * PPPPPPPPPPPPPPPPPPP <-- This Frames Pilot
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD These are the current data symbols to be decoded
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * PPPPPPPPPPPPPPPPPPP <-- Next Frames Pilot
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD Ignore these next data symbols
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * DDDDDDDDDDDDDDDDD
+ * PPPPPPPPPPPPPPPPPPP <-- Future Frames Pilot
+ * XXXXXXXXXXXXXXXXX <-- Timing Slip
*
* So this algorithm will have seven data symbols and four pilot symbols to process.
* The average of the four pilot symbols is our phase estimation.
/*
* Each symbol is of course (OFDM_M + OFDM_NCP) samples long and
- * becomes 18 carriers after DFT.
+ * becomes Nc+2 carriers after DFT.
*
- * We put this 18 carrier pilot symbol at the top of our matrix:
+ * We put this carrier pilot symbol at the top of our matrix:
*
- * 0 ................... 17
+ * 1 .................. Nc+2
*
* +----------------------+
* | Previous Pilot | rx_sym[0]
}
/*
- * We put these 18 carrier symbols into our matrix after the previous pilot:
+ * We put these Nc+2 carrier symbols into our matrix after the previous pilot:
*
- * 0 ................... 17
+ * 1 .................. Nc+2
*
* | Previous Pilot | rx_sym[0]
* +----------------------+
/*
* We put the future pilot after all the previous symbols in the matrix:
*
- * 0 ................... 17
+ * 1 .................. Nc+2
*
* | | rx_sym[9]
* +----------------------+
}
/*
- * Basically we divide the 18 pilots into groups of 3
+ * Basically we divide the Nc+2 pilots into groups of 3
*
* Then average the phase surrounding each of the data symbols.
*/
complex float rx_corr;
int abit[2];
int bit_index = 0;
- float sum_amp = 0.0;
+ float sum_amp = 0.0f;
for (rr = 0; rr < OFDM_ROWSPERFRAME; rr++) {
/*
- * Note the i has an index of 1 to 16, so we ignore carriers 0 and 17.
+ * Note the i starts with the second carrier, ends with Nc+1.
+ * so we ignore the first and last carriers.
*
* Also note we are using sym[2..8] or the seven data symbols.
*/
/* update mean amplitude estimate for LDPC decoder scaling */
- ofdm->mean_amp = 0.9*ofdm->mean_amp + 0.1*sum_amp/(OFDM_ROWSPERFRAME * OFDM_NC);
+ ofdm->mean_amp = 0.9f * ofdm->mean_amp + 0.1f * sum_amp/(OFDM_ROWSPERFRAME * OFDM_NC);
/* Adjust nin to take care of sample clock offset */
/* estimate signal and noise power, see ofdm_lib.m, cohpsk.m for
more info */
- float sig_var = 0.0;
+ float sig_var = 0.0f;
complex float *rx_np = ofdm->rx_np;
- for(i=0; i<OFDM_ROWSPERFRAME * OFDM_NC; i++) {
- sig_var += crealf(rx_np[i])*crealf(rx_np[i]) + cimagf(rx_np[i])*cimagf(rx_np[i]);
+
+ for (i = 0; i < (OFDM_ROWSPERFRAME * OFDM_NC); i++) {
+ sig_var += crealf(rx_np[i]) * crealf(rx_np[i]) + cimagf(rx_np[i]) * cimagf(rx_np[i]);
}
+
sig_var /= (OFDM_ROWSPERFRAME * OFDM_NC);
float sig_rms = sqrtf(sig_var);
complex float s;
- float sum_x = 0;
- float sum_xx = 0;
+ float sum_x = 0.0f;
+ float sum_xx = 0.0f;
int n = 0;
+
for (i=0; i<OFDM_ROWSPERFRAME * OFDM_NC; i++) {
s = rx_np[i];
- if (fabs(crealf(s)) > sig_rms) {
+
+ if (fabsf(crealf(s)) > sig_rms) {
sum_x += cimagf(s);
sum_xx += cimagf(s) * cimagf(s);
n++;
that case set a benign value for noise_var that will produce a
sensible (probably low) SNR est */
- float noise_var = 1.0;
+ float noise_var = 1.0f;
+
if (n > 1) {
- noise_var = (n*sum_xx - sum_x*sum_x)/(n*(n-1));
+ noise_var = (n * sum_xx - sum_x * sum_x) / (n * (n - 1));
}
- ofdm->noise_var = 2*noise_var;
+
+ ofdm->noise_var = 2.0f * noise_var;
ofdm->sig_var = sig_var;
}
ofdm->sync_start = ofdm->sync_end = 0;
if (strcmp(ofdm->sync_state,"search") == 0) {
-
if (ofdm->timing_valid) {
/* freq offset est has some bias, but this refinement step fixes bias */
int st = OFDM_M + OFDM_NCP + OFDM_SAMPLESPERFRAME;
- int en = st + 2*OFDM_SAMPLESPERFRAME;
+ int en = st + 2 * OFDM_SAMPLESPERFRAME;
float woff_est = TAU * ofdm->foff_est_hz / OFDM_FS;
complex float work[(en - st)];
float foff_est;
coarse_sync(ofdm, work, (en - st), &foff_est);
+
if (ofdm->verbose) {
fprintf(stderr, " coarse_foff: %4.1f refine: %4.1f combined: %4.1f\n", ofdm->foff_est_hz, foff_est, ofdm->foff_est_hz+foff_est);
}
+
ofdm->foff_est_hz += foff_est;
ofdm->frame_count = 0;
ofdm->sync_counter = 0;
}
if (!strcmp(ofdm->sync_state,"synced") || !strcmp(ofdm->sync_state, "trial")) {
-
ofdm->frame_count++;
ofdm->frame_count_interleaver++;
we use a Unique Word to get a really solid indication of sync. */
ofdm->uw_errors = 0;
+
for (i=0; i<OFDM_NUWBITS; i++) {
ofdm->uw_errors += ofdm->tx_uw[i] ^ rx_uw[i];
}
ofdm->sync_counter++;
ofdm->frame_count = 0;
}
+
if (ofdm->sync_counter == 2) {
/* if we get two bad frames drop sync and start again */
strcpy(next_state, "search");
void ofdm_get_demod_stats(struct OFDM *ofdm, struct MODEM_STATS *stats)
{
- int c,r;
+ int c, r;
stats->Nc = OFDM_NC;
assert(stats->Nc <= MODEM_STATS_NC_MAX);
- float snr_est = 10*log10((ofdm->sig_var/ofdm->noise_var)*OFDM_NC*OFDM_RS/3000);
+ float snr_est = 10.0f * log10f((ofdm->sig_var / ofdm->noise_var) * OFDM_NC*OFDM_RS / 3000.0f);
//fprintf(stderr, "sig: %f var: %f snr: %f\n", ofdm->sig_var, ofdm->noise_var, snr_est);
- stats->snr_est = 0.9*stats->snr_est + 0.1*snr_est;
+ stats->snr_est = 0.9f * stats->snr_est + 0.1f * snr_est;
stats->sync = !strcmp(ofdm->sync_state, "synced") || !strcmp(ofdm->sync_state, "trial");
//fprintf(stderr, "sync: %d %s\n", stats->sync, ofdm->sync_state);
stats->foff = ofdm->foff_est_hz;
stats->rx_timing = ofdm->timing_est;
- stats->clock_offset = 0.0; /* TODO: work out sample clock offset */
+ stats->clock_offset = 0.0f; /* TODO: work out sample clock offset */
assert(OFDM_ROWSPERFRAME < MODEM_STATS_NR_MAX);
stats->nr = OFDM_ROWSPERFRAME;
- for(c=0; c<OFDM_NC; c++) {
- for (r=0; r<OFDM_ROWSPERFRAME; r++) {
- complex float rot = ofdm->rx_np[r*c] * cexpf(I * (M_PI/4.0));
+
+ for (c = 0; c < OFDM_NC; c++) {
+ for (r = 0; r < OFDM_ROWSPERFRAME; r++) {
+ complex float rot = ofdm->rx_np[r * c] * cexpf(I * (M_PI / 4.0f));
stats->rx_symbols[r][c].real = crealf(rot);
stats->rx_symbols[r][c].imag = cimagf(rot);
//fprintf(stderr, "%f %f\n", stats->rx_symbols[r][c].real, stats->rx_symbols[r][c].imag);
}
}
}
+
projects / freetel-svn-tracking.git / commitdiff