/* Computes channel estimates for each reference in a slot and port.
* Saves the nof_prb * 12 * nof_symbols channel estimates in the array ce
*/
void chest_ce_slot_port(chest_t *q, cf_t *input, cf_t *ce, int nslot, int port_id) {
int i, j;
cf_t x[2], y[MAX_NSYMB];
assert(nslot >= 0 && nslot < NSLOTS_X_FRAME);
assert(port_id >= 0 && port_id < q->nof_ports);
assert(q->refsignal[port_id][nslot].nsymbols <= 2);
refsignal_t *r = &q->refsignal[port_id][nslot];
INFO("Estimating channel using %d reference signals\n", r->nof_refs);
for (i=0;i<r->nof_refs;i++) {
chest_ce_ref(q, input, nslot, port_id, i);
}
/* interpolate the symbols with references
* in the freq domain */
for (i=0;i<r->nsymbols;i++) {
interp_linear_offset(&r->ch_est[i * r->nof_refs/2],
&ce[r->symbols_ref[i] * q->nof_prb * RE_X_RB], RE_X_RB/2,
r->nof_refs/2, r->voffset, RE_X_RB/2-r->voffset);
}
/* now interpolate in the time domain */
for (i=0;i<q->nof_prb * RE_X_RB; i++) {
for (j=0;j<r->nsymbols;j++) {
x[j] = ce[r->symbols_ref[j] * q->nof_prb * RE_X_RB + i];
}
interp_linear_offset(x, y, r->symbols_ref[1]-r->symbols_ref[0],
2, r->symbols_ref[0], 3);
for (j=0;j<q->nof_symbols;j++) {
ce[j * q->nof_prb * RE_X_RB + i] = y[j];
}
}
}
/* Computes channel estimates for each reference in a slot and port.
* Saves the nof_prb * 12 * nof_symbols channel estimates in the array ce
*/
int chest_ce_slot_port(chest_t *q, cf_t *input, cf_t *ce, uint32_t nslot, uint32_t port_id) {
uint32_t i, j;
cf_t x[2], y[MAX_NSYMB];
int ret = LIBLTE_ERROR_INVALID_INPUTS;
if (q != NULL &&
input != NULL &&
nslot < NSLOTS_X_FRAME &&
port_id < q->nof_ports)
{
if (q->refsignal[port_id][nslot].nsymbols <= 2) {
refsignal_t *r = &q->refsignal[port_id][nslot];
DEBUG("Estimating channel slot=%d port=%d using %d reference signals\n",
nslot, port_id, r->nof_refs);
for (i=0;i<r->nof_refs;i++) {
chest_ce_ref(q, input, nslot, port_id, i);
}
/* interpolate the symbols with references
* in the freq domain */
for (i=0;i<r->nsymbols;i++) {
#ifdef VOLK_INTERP
interp_run_offset(&q->interp_freq[port_id],
&r->ch_est[i * r->nof_refs/2], &ce[r->symbols_ref[i] * q->nof_re],
r->voffset, RE_X_RB/2-r->voffset);
#else
interp_linear_offset(&r->ch_est[i * r->nof_refs/2],
&ce[r->symbols_ref[i] * q->nof_re], RE_X_RB/2,
r->nof_refs/2, r->voffset, RE_X_RB/2-r->voffset);
#endif
}
/* now interpolate in the time domain */
for (i=0;i<q->nof_re; i++) {
if (r->nsymbols > 1) {
for (j=0;j<r->nsymbols;j++) {
x[j] = ce[r->symbols_ref[j] * q->nof_re + i];
}
#ifdef VOLK_INTERP
interp_run_offset(&q->interp_time[port_id], x, y,
r->symbols_ref[0], 3);
#else
interp_linear_offset(x, y, r->symbols_ref[1]-r->symbols_ref[0],
2, r->symbols_ref[0], 3);
#endif
} else {
for (j=0;j<MAX_NSYMB;j++) {
y[j] = ce[r->symbols_ref[0] * q->nof_re + i];
}
}
for (j=0;j<q->nof_symbols;j++) {
ce[j * q->nof_re + i] = y[j];
}
}
ret = LIBLTE_SUCCESS;
}
}
return ret;
}
/* Performs 1st order linear interpolation */
void interp_linear(cf_t *input, cf_t *output, int M, int len) {
interp_linear_offset(input, output, M, len, 0, 0);
}