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Implementing delay compensation during SRS-based channel estimation

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This commit is contained in:
rmagueta
2026-03-19 09:18:18 +00:00
parent fdb6b44b05
commit 0db8ddac08
3 changed files with 74 additions and 21 deletions
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openair1/PHY/NR_ESTIMATION/nr_ul_channel_estimation.c
+70 -19
View File
@@ -780,7 +780,8 @@ int nr_srs_channel_estimation(int ant,
c16_t srs_estimated_channel_time_shifted[NR_SRS_IDFT_OVERSAMP_FACTOR * ofdm_symbol_size],
uint32_t *signal_power,
uint32_t *noise_power,
int16_t *noise_power_per_rb)
int16_t *noise_power_per_rb,
c16_t delay_table[2 * MAX_DELAY_COMP + 1][NR_MAX_OFDM_SYMBOL_SIZE])
{
#ifdef SRS_DEBUG
LOG_I(NR_PHY, "Calling %s function\n", __FUNCTION__);
@@ -797,40 +798,29 @@ int nr_srs_channel_estimation(int ant,
if (N_ap == 4 && ((K_TC == 2 && srs_pdu->cyclic_shift >= 4) || (K_TC == 4 && srs_pdu->cyclic_shift >= 6))) {
fd_cdm = 2;
}
uint16_t subcarrier;
c16_t srs_ls_estimated_channel[ofdm_symbol_size * N_symb_SRS];
c16_t srs_estimated_channel_freq_avg[ofdm_symbol_size];
memset(srs_ls_estimated_channel, 0, ofdm_symbol_size * N_symb_SRS * sizeof(c16_t));
memset(srs_estimated_channel_freq_avg, 0, ofdm_symbol_size * sizeof(c16_t));
delay_t delay = {0};
for (int srs_symb = 0; srs_symb < N_symb_SRS; srs_symb++) {
uint16_t srs_symbol_offset = srs_symb * ofdm_symbol_size;
// Additional 4 in the array size is needed to maintain 16 byte memory alignment required for AVX2 instructions in channel
// interpolation
c16_t srs_est[ofdm_symbol_size + 4] __attribute__((aligned(32)));
memset(srs_est, 0, (ofdm_symbol_size + 4) * sizeof(c16_t));
// Estimate 16 byte memory alignment offset for the first SRS subcarrier to use AVX2 instructions in channel interpolation
uint8_t mem_offset = (16 - (((intptr_t)&srs_est[first_subcarrier + nr_srs_info->k_0_p[p_index][srs_symb]]) & 0xF))
>> 2; // >> 2 <=> /sizeof(int32_t)
c16_t ls_estimated = {0};
#ifdef SRS_DEBUG
LOG_I(NR_PHY, "====================== UE port %d --> gNB Rx antenna %i ======================\n", p_index, ant);
LOG_I(NR_PHY, "============================== SRS symbol index %d ===========================\n", srs_symb);
#endif
subcarrier = subcarrier_offset + nr_srs_info->k_0_p[p_index][srs_symb];
// Channel estimation based on least square method
uint16_t subcarrier = subcarrier_offset + nr_srs_info->k_0_p[p_index][srs_symb];
if (subcarrier >= ofdm_symbol_size) {
subcarrier -= ofdm_symbol_size;
}
uint16_t subcarrier_abs = mem_offset + first_subcarrier + nr_srs_info->k_0_p[p_index][srs_symb];
c16_t *srs_estimated_channel16 = &srs_est[subcarrier_abs];
c16_t ls_estimated = {0};
for (int k = 0; k < M_sc_b_SRS; k++) {
if (k % fd_cdm == 0) {
ls_estimated = (c16_t){0, 0};
@@ -852,7 +842,9 @@ int nr_srs_channel_estimation(int ant,
}
}
srs_ls_estimated_channel[srs_symbol_offset + subcarrier] = ls_estimated;
for (int ktc = 0; ktc < K_TC && srs_symbol_offset + subcarrier + ktc < ofdm_symbol_size * N_symb_SRS; ktc++) {
srs_ls_estimated_channel[srs_symbol_offset + subcarrier + ktc] = ls_estimated;
}
#ifdef SRS_DEBUG
int subcarrier_log = subcarrier - subcarrier_offset;
@@ -874,6 +866,44 @@ int nr_srs_channel_estimation(int ant,
ls_estimated.i);
#endif
// Subcarrier increment
subcarrier += K_TC;
if (subcarrier >= ofdm_symbol_size) {
subcarrier -= ofdm_symbol_size;
}
} // for (int k = 0; k < M_sc_b_SRS; k++)
// Delay estimation
c16_t ch_estimates_time[ofdm_symbol_size] __attribute__((aligned(32)));
nr_est_delay(ofdm_symbol_size, srs_ls_estimated_channel, ch_estimates_time, &delay);
// Interpolation of LS estimates
// Additional 4 in the array size is needed to maintain 16 byte memory alignment required for AVX2 instructions in channel
// interpolation
c16_t srs_est[ofdm_symbol_size + 4] __attribute__((aligned(32)));
memset(srs_est, 0, (ofdm_symbol_size + 4) * sizeof(c16_t));
// Estimate 16 byte memory alignment offset for the first SRS subcarrier to use AVX2 instructions in channel interpolation
uint8_t mem_offset =
(16 - (((intptr_t)&srs_est[first_subcarrier + nr_srs_info->k_0_p[p_index][srs_symb]]) & 0xF)) / sizeof(c16_t);
uint16_t subcarrier_abs = mem_offset + first_subcarrier + nr_srs_info->k_0_p[p_index][srs_symb];
c16_t *srs_estimated_channel16 = &srs_est[subcarrier_abs];
subcarrier = subcarrier_offset + nr_srs_info->k_0_p[p_index][srs_symb];
if (subcarrier >= ofdm_symbol_size) {
subcarrier -= ofdm_symbol_size;
}
int delay_idx = get_delay_idx(delay.est_delay, MAX_DELAY_COMP);
const c16_t *srs_delay_table = delay_table[delay_idx];
for (int k = 0; k < M_sc_b_SRS; k++) {
// Apply delay
ls_estimated = c16mulShift(srs_ls_estimated_channel[srs_symbol_offset + subcarrier], srs_delay_table[subcarrier], 8);
// Channel interpolation
if (srs_pdu->comb_size == 0) {
if (k == 0) { // First subcarrier case
@@ -914,6 +944,27 @@ int nr_srs_channel_estimation(int ant,
} // for (int k = 0; k < M_sc_b_SRS; k++)
// Revert delay
int inv_delay_idx = get_delay_idx(-delay.est_delay, MAX_DELAY_COMP);
const c16_t *srs_inv_delay_table = delay_table[inv_delay_idx];
subcarrier_abs = mem_offset + first_subcarrier + nr_srs_info->k_0_p[p_index][srs_symb];
subcarrier = subcarrier_offset + nr_srs_info->k_0_p[p_index][0];
if (subcarrier >= ofdm_symbol_size) {
subcarrier -= ofdm_symbol_size;
}
for (int k = 0; k < K_TC * M_sc_b_SRS; k++) {
srs_est[subcarrier_abs] = c16mulShift(srs_est[subcarrier_abs], srs_inv_delay_table[subcarrier], 8);
// Subcarrier increment
subcarrier++;
if (subcarrier >= ofdm_symbol_size) {
subcarrier -= ofdm_symbol_size;
}
subcarrier_abs++;
if (subcarrier_abs >= ofdm_symbol_size) {
subcarrier_abs -= ofdm_symbol_size;
}
}
memcpy(&srs_estimated_channel_freq[srs_symbol_offset], &srs_est[mem_offset], ofdm_symbol_size * sizeof(c16_t));
// Average srs channel estimates over multiple symbols
@@ -996,7 +1047,7 @@ int nr_srs_channel_estimation(int ant,
return -1;
}
subcarrier = subcarrier_offset + nr_srs_info->k_0_p[p_index][0];
uint16_t subcarrier = subcarrier_offset + nr_srs_info->k_0_p[p_index][0];
if (subcarrier >= ofdm_symbol_size) {
subcarrier -= ofdm_symbol_size;
}
openair1/PHY/NR_ESTIMATION/nr_ul_estimation.h
+2 -1
View File
@@ -90,7 +90,8 @@ int nr_srs_channel_estimation(int ant,
c16_t srs_estimated_channel_time_shifted[NR_SRS_IDFT_OVERSAMP_FACTOR * ofdm_symbol_size],
uint32_t *signal_power,
uint32_t *noise_power,
int16_t *noise_power_per_rb);
int16_t *noise_power_per_rb,
c16_t delay_table[2 * MAX_DELAY_COMP + 1][NR_MAX_OFDM_SYMBOL_SIZE]);
void nr_freq_equalization(NR_DL_FRAME_PARMS *frame_parms,
c16_t *rxdataF_comp,
openair1/SCHED_NR/phy_procedures_nr_gNB.c
+2 -1
View File
@@ -905,7 +905,8 @@ void nr_srs_rx_procedures(PHY_VARS_gNB *gNB,
srs_estimated_channel_time_shifted[ant_rx_ind][p_ind],
&signal_power,
&noise_power,
noise_power_per_rb);
noise_power_per_rb,
frame_parms->delay_table);
signal_power_avg += signal_power;