PentHertz
/
srsLTE
mirror of https://github.com/PentHertz/srsLTE.git
1
0
Fork 0
Code Issues Packages Projects Releases Wiki Activity

Reviewed LTE noise estimation

This commit is contained in:
Xavier Arteaga 2021-05-03 15:23:38 +02:00 committed by Xavier Arteaga
parent 10a268fdba
commit 2ca0932d9b
1 changed files with 23 additions and 24 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

47
lib/src/phy/ch_estimation/chest_dl.c
View File

@ -323,15 +323,18 @@ static float estimate_noise_pilots(srsran_chest_dl_t* q, srsran_dl_sf_cfg_t* sf,
: srsran_refsignal_cs_nof_re(&q->csr_refs, sf, port_id);
uint32_t nsymbols = (ch_mode == SRSRAN_SF_MBSFN) ? srsran_refsignal_mbsfn_nof_symbols()
: srsran_refsignal_cs_nof_symbols(&q->csr_refs, sf, port_id);
if (nsymbols == 0) {
ERROR("Invalid number of CRS symbols\n");
return SRSRAN_ERROR;
}
uint32_t nref = npilots / nsymbols;
uint32_t fidx =
(ch_mode == SRSRAN_SF_MBSFN) ? srsran_refsignal_mbsfn_fidx(1) : srsran_refsignal_cs_fidx(q->cell, 0, port_id, 0);
cf_t* input2d[nsymbols + 2];
cf_t* tmp_noise = q->tmp_noise;
// Special case for 1 symbol
if (nsymbols == 1) {
// Special case for 1 or 2 symbol
if (nsymbols < 3) {
srsran_vec_sc_prod_cfc(q->pilot_estimates + 1, weight, tmp_noise, nref - 2);
srsran_vec_sum_ccc(q->pilot_estimates + 0, tmp_noise, tmp_noise, nref - 2);
srsran_vec_sum_ccc(q->pilot_estimates + 2, tmp_noise, tmp_noise, nref - 2);
@ -341,30 +344,21 @@ static float estimate_noise_pilots(srsran_chest_dl_t* q, srsran_dl_sf_cfg_t* sf,
return sum_power;
}
// Convert pilots to 2D to ease access
cf_t* input2d[4]; // The maximum number of symbols is 4
for (int i = 0; i < nsymbols; i++) {
input2d[i + 1] = &q->pilot_estimates[i * nref];
input2d[i] = &q->pilot_estimates[i * nref];
}
input2d[0] = &q->tmp_noise[nref];
if (nsymbols > 3) {
srsran_vec_sc_prod_cfc(input2d[2], 2.0f, input2d[0], nref);
srsran_vec_sub_ccc(input2d[0], input2d[4], input2d[0], nref);
} else {
srsran_vec_sc_prod_cfc(input2d[2], 1.0f, input2d[0], nref);
}
input2d[nsymbols + 1] = &q->tmp_noise[nref * 2];
if (nsymbols > 3) {
srsran_vec_sc_prod_cfc(input2d[nsymbols - 1], 2.0f, input2d[nsymbols + 1], nref);
srsran_vec_sub_ccc(input2d[nsymbols + 1], input2d[nsymbols - 3], input2d[nsymbols + 1], nref);
} else {
srsran_vec_sc_prod_cfc(input2d[nsymbols - 1], 1.0f, input2d[nsymbols + 1], nref);
}
for (int i = 1; i < nsymbols + 1; i++) {
// Compares surrounding pilots in time/frequency. It requires at least 3 symbols with pilots.
for (int i = 1; i < nsymbols - 1; i++) {
// Calculate previous and next symbol indexes offset
uint32_t offset = ((fidx < 3) ^ (i & 1)) ? 0 : 1;
// Write estimates from this symbols
srsran_vec_sc_prod_cfc(input2d[i], weight, tmp_noise, nref);
// Add the previous symbol estimates and extrapolate first/last element
srsran_vec_sum_ccc(&input2d[i - 1][0], &tmp_noise[offset], &tmp_noise[offset], nref - offset);
srsran_vec_sum_ccc(&input2d[i - 1][1 - offset], &tmp_noise[0], &tmp_noise[0], nref + offset - 1);
if (offset) {
@ -373,6 +367,7 @@ static float estimate_noise_pilots(srsran_chest_dl_t* q, srsran_dl_sf_cfg_t* sf,
tmp_noise[nref - 1] += 2.0f * input2d[i - 1][nref - 2] - input2d[i - 1][nref - 1];
}
// Add the next symbol estimates and extrapolate first/last element
srsran_vec_sum_ccc(&input2d[i + 1][0], &tmp_noise[offset], &tmp_noise[offset], nref - offset);
srsran_vec_sum_ccc(&input2d[i + 1][1 - offset], &tmp_noise[0], &tmp_noise[0], nref + offset - 1);
if (offset) {
@ -381,14 +376,18 @@ static float estimate_noise_pilots(srsran_chest_dl_t* q, srsran_dl_sf_cfg_t* sf,
tmp_noise[nref - 1] += 2.0f * input2d[i + 1][nref - 2] - input2d[i + 1][nref - 1];
}
// Scale to normalise to this symbol
srsran_vec_sc_prod_cfc(tmp_noise, 1.0f / (weight + 4.0f), tmp_noise, nref);
// Subtract this symbol
srsran_vec_sub_ccc(input2d[i], tmp_noise, tmp_noise, nref);
sum_power = srsran_vec_avg_power_cf(tmp_noise, nref);
// The left signal after the subtraction can be considered noise
sum_power += srsran_vec_avg_power_cf(tmp_noise, nref);
count++;
}
return sum_power / (float)count * sqrtf(weight + 4.0f);
return sum_power / (float)count;
}
static float estimate_noise_pss(srsran_chest_dl_t* q, cf_t* input, cf_t* ce)