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srsLTE
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Protect input buffer SSB demodulation in search/find and skip PBCH decoding if PBCH DMRS correlation does not reach threshold

This commit is contained in:
Xavier Arteaga 2022-01-26 11:17:48 +01:00 committed by Xavier Arteaga
parent aea7a11e53
commit 569f5c1a6f
1 changed files with 53 additions and 12 deletions
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49
lib/src/phy/sync/ssb.c
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@ -965,6 +965,11 @@ int srsran_ssb_csi_search(srsran_ssb_t* q,
t_offset = 0;
}
// Make sure SSB time offset is in bounded in the input buffer
if (t_offset + q->ssb_sz > nof_samples) {
return SRSRAN_SUCCESS;
}
// Demodulate
cf_t ssb_grid[SRSRAN_SSB_NOF_RE] = {};
if (ssb_demodulate(q, in, t_offset, coarse_cfo_hz, ssb_grid) < SRSRAN_SUCCESS) {
@ -1038,7 +1043,8 @@ static int ssb_select_pbch(srsran_ssb_t* q,
uint32_t N_id,
const cf_t ssb_grid[SRSRAN_SSB_NOF_RE],
uint32_t* found_n_hf,
uint32_t* found_ssb_idx_4lsb)
uint32_t* found_ssb_idx_4lsb,
srsran_dmrs_pbch_meas_t* pbch_meas)
{
// Prepare PBCH DMRS configuration
srsran_dmrs_pbch_cfg_t pbch_dmrs_cfg = {};
@ -1080,6 +1086,7 @@ static int ssb_select_pbch(srsran_ssb_t* q,
// Save findings
*found_n_hf = best_n_hf;
*found_ssb_idx_4lsb = best_ssb_idx;
*pbch_meas = best_meas;
return SRSRAN_SUCCESS;
}
@ -1177,6 +1184,9 @@ int srsran_ssb_search(srsran_ssb_t* q, const cf_t* in, uint32_t nof_samples, srs
return SRSRAN_ERROR;
}
// Set the SSB search result with default value with PBCH CRC unmatched, meaning no cell is found
SRSRAN_MEM_ZERO(res, srsran_ssb_search_res_t, 1);
// Search for PSS in time domain
uint32_t N_id_2 = 0;
uint32_t t_offset = 0;
@ -1193,6 +1203,11 @@ int srsran_ssb_search(srsran_ssb_t* q, const cf_t* in, uint32_t nof_samples, srs
t_offset = 0;
}
// Make sure SSB time offset is in bounded in the input buffer
if (t_offset + q->ssb_sz > nof_samples) {
return SRSRAN_SUCCESS;
}
// Demodulate
cf_t ssb_grid[SRSRAN_SSB_NOF_RE] = {};
if (ssb_demodulate(q, in, t_offset, coarse_cfo_hz, ssb_grid) < SRSRAN_SUCCESS) {
@ -1214,18 +1229,30 @@ int srsran_ssb_search(srsran_ssb_t* q, const cf_t* in, uint32_t nof_samples, srs
// Select the most suitable SSB candidate
uint32_t n_hf = 0;
uint32_t ssb_idx = 0;
if (ssb_select_pbch(q, N_id, ssb_grid, &n_hf, &ssb_idx) < SRSRAN_SUCCESS) {
srsran_dmrs_pbch_meas_t pbch_meas = {};
if (ssb_select_pbch(q, N_id, ssb_grid, &n_hf, &ssb_idx, &pbch_meas) < SRSRAN_SUCCESS) {
ERROR("Error selecting PBCH");
return SRSRAN_ERROR;
}
// Compute PBCH channel estimates
// Avoid decoding if the selected PBCH DMRS do not reach the minimum threshold
if (pbch_meas.corr < q->args.pbch_dmrs_thr) {
return SRSRAN_SUCCESS;
}
// Decode PBCH
srsran_pbch_msg_nr_t pbch_msg = {};
if (ssb_decode_pbch(q, N_id, n_hf, ssb_idx, ssb_grid, &pbch_msg) < SRSRAN_SUCCESS) {
ERROR("Error decoding PBCH");
return SRSRAN_ERROR;
}
// If PBCH was not decoded, skip measurements
if (!pbch_msg.crc) {
return SRSRAN_SUCCESS;
}
// Perform measurements from PSS and SSS
srsran_csi_trs_measurements_t measurements = {};
if (ssb_measure(q, ssb_grid, N_id, &measurements) < SRSRAN_SUCCESS) {
ERROR("Error measuring");
@ -1327,6 +1354,9 @@ int srsran_ssb_find(srsran_ssb_t* q,
return SRSRAN_ERROR;
}
// Set the PBCH message result with default value (CRC unmatched), meaning no cell is found
SRSRAN_MEM_ZERO(pbch_msg, srsran_pbch_msg_nr_t, 1);
// Copy tail from previous execution into the start of this
srsran_vec_cf_copy(q->sf_buffer, &q->sf_buffer[q->sf_sz], q->ssb_sz);
@ -1347,6 +1377,11 @@ int srsran_ssb_find(srsran_ssb_t* q,
t_offset = 0;
}
// Make sure SSB time offset is in bounded in the input buffer
if (t_offset > q->sf_sz) {
return SRSRAN_SUCCESS;
}
// Demodulate
cf_t ssb_grid[SRSRAN_SSB_NOF_RE] = {};
if (ssb_demodulate(q, q->sf_buffer, t_offset, 0.0f, ssb_grid) < SRSRAN_SUCCESS) {
@ -1363,11 +1398,17 @@ int srsran_ssb_find(srsran_ssb_t* q,
// Select the most suitable SSB candidate
uint32_t n_hf = 0;
uint32_t ssb_idx = 0; // SSB candidate index
if (ssb_select_pbch(q, N_id, ssb_grid, &n_hf, &ssb_idx) < SRSRAN_SUCCESS) {
srsran_dmrs_pbch_meas_t pbch_meas = {};
if (ssb_select_pbch(q, N_id, ssb_grid, &n_hf, &ssb_idx, &pbch_meas) < SRSRAN_SUCCESS) {
ERROR("Error selecting PBCH");
return SRSRAN_ERROR;
}
// Avoid decoding if the selected PBCH DMRS do not reach the minimum threshold
if (pbch_meas.corr < q->args.pbch_dmrs_thr) {
return SRSRAN_SUCCESS;
}
// Calculate the SSB offset in the subframe
uint32_t ssb_offset = srsran_ssb_candidate_sf_offset(q, ssb_idx);