/* 36.211 v10.3.0 Section 6.3.4 */
int predecoding_type(cf_t *y, cf_t *ce[MAX_PORTS], cf_t *x[MAX_LAYERS],
int nof_ports, int nof_layers, int nof_symbols, lte_mimo_type_t type) {
if (nof_ports > MAX_PORTS) {
fprintf(stderr, "Maximum number of ports is %d (nof_ports=%d)\n", MAX_PORTS,
nof_ports);
return -1;
}
if (nof_layers > MAX_LAYERS) {
fprintf(stderr, "Maximum number of layers is %d (nof_layers=%d)\n",
MAX_LAYERS, nof_layers);
return -1;
}
switch (type) {
case SINGLE_ANTENNA:
if (nof_ports == 1 && nof_layers == 1) {
return predecoding_single_zf(y, ce[0], x[0], nof_symbols);
} else {
fprintf(stderr,
"Number of ports and layers must be 1 for transmission on single antenna ports\n");
return -1;
}
break;
case TX_DIVERSITY:
if (nof_ports == nof_layers) {
return predecoding_diversity_zf(y, ce, x, nof_ports, nof_symbols);
} else {
fprintf(stderr,
"Error number of layers must equal number of ports in transmit diversity\n");
return -1;
}
break;
case SPATIAL_MULTIPLEX:
fprintf(stderr, "Spatial multiplexing not supported\n");
return -1;
}
return 0;
}
/* Decodes the PBCH channel
*
* The PBCH spans in 40 ms. This function is called every 10 ms. It tries to decode the MIB
* given the symbols of a subframe (1 ms). Successive calls will use more subframes
* to help the decoding process.
*
* Returns 1 if successfully decoded MIB, 0 if not and -1 on error
*/
int pbch_decode(pbch_t *q, cf_t *slot1_symbols, cf_t *ce_slot1[MAX_PORTS], pbch_mib_t *mib) {
uint32_t src, dst, nb;
uint32_t nant_[3] = { 1, 2, 4 };
uint32_t na, nant;
int i;
int nof_bits;
cf_t *x[MAX_LAYERS];
int ret = LIBLTE_ERROR_INVALID_INPUTS;
if (q != NULL &&
slot1_symbols != NULL &&
mib != NULL)
{
for (i=0;i<q->cell.nof_ports;i++) {
if (ce_slot1[i] == NULL) {
return LIBLTE_ERROR_INVALID_INPUTS;
}
}
/* Set pointers for layermapping & precoding */
nof_bits = 2 * q->nof_symbols;
/* number of layers equals number of ports */
for (i = 0; i < MAX_PORTS; i++) {
x[i] = q->pbch_x[i];
}
memset(&x[MAX_PORTS], 0, sizeof(cf_t*) * (MAX_LAYERS - MAX_PORTS));
/* extract symbols */
if (q->nof_symbols != pbch_get(slot1_symbols, q->pbch_symbols[0], q->cell)) {
fprintf(stderr, "There was an error getting the PBCH symbols\n");
return LIBLTE_ERROR;
}
/* extract channel estimates */
for (i = 0; i < q->cell.nof_ports; i++) {
if (q->nof_symbols != pbch_get(ce_slot1[i], q->ce[i], q->cell)) {
fprintf(stderr, "There was an error getting the PBCH symbols\n");
return LIBLTE_ERROR;
}
}
q->frame_idx++;
ret = 0;
/* Try decoding for 1 to cell.nof_ports antennas */
for (na = 0; na < q->cell.nof_ports && !ret; na++) {
nant = nant_[na];
DEBUG("Trying %d TX antennas with %d frames\n", nant, q->frame_idx);
/* in conctrol channels, only diversity is supported */
if (nant == 1) {
/* no need for layer demapping */
predecoding_single_zf(q->pbch_symbols[0], q->ce[0], q->pbch_d,
q->nof_symbols);
} else {
predecoding_diversity_zf(q->pbch_symbols[0], q->ce, x, nant,
q->nof_symbols);
layerdemap_diversity(x, q->pbch_d, nant, q->nof_symbols / nant);
}
/* demodulate symbols */
demod_soft_sigma_set(&q->demod, 1.0);
demod_soft_demodulate(&q->demod, q->pbch_d,
&q->pbch_llr[nof_bits * (q->frame_idx - 1)], q->nof_symbols);
/* We don't know where the 40 ms begin, so we try all combinations. E.g. if we received
* 4 frames, try 1,2,3,4 individually, 12, 23, 34 in pairs, 123, 234 and finally 1234.
* We know they are ordered.
*
* FIXME: There are unnecessary checks because 2,3,4 have already been processed in the previous
* calls.
*/
for (nb = 0; nb < q->frame_idx && !ret; nb++) {
for (dst = 0; (dst < 4 - nb) && !ret; dst++) {
for (src = 0; src < q->frame_idx - nb && !ret; src++) {
ret = pbch_decode_frame(q, mib, src, dst, nb + 1, nof_bits, nant);
}
}
}
}
/* If not found, make room for the next packet of radio frame symbols */
if (q->frame_idx == 4) {
memmove(q->pbch_llr, &q->pbch_llr[nof_bits], nof_bits * 3 * sizeof(float));
q->frame_idx = 3;
}
}
return ret;
}
