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Check for DCI false positive

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by comparing the received bits with re-encoded payload bits
This commit is contained in:
Sakthivel Velumani
2021-03-30 12:07:15 +02:00
parent fe191c7d0a
commit e1e459d27c
1 changed files with 43 additions and 9 deletions
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openair1/PHY/NR_UE_TRANSPORT/dci_nr.c
+43 -9
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@@ -874,6 +874,33 @@ void nr_pdcch_unscrambling(int16_t *z,
#ifdef NR_PDCCH_DCI_RUN
/* This function compares the received DCI bits with
* re-encoded DCI bits and returns the number of mismatched bits
*/
uint16_t nr_dci_false_detection(uint64_t *dci,
int16_t *soft_in,
t_nrPolar_params *polar_param,
int encoded_length,
int rnti) {
uint32_t encoder_output[NR_MAX_DCI_SIZE_DWORD];
polar_encoder_fast(dci, (void*)encoder_output, rnti, 1, polar_param);
uint8_t *enout_p = (int16_t*)encoder_output;
uint16_t x = 0;
for (int i=0; i<encoded_length/8; i++) {
x += ( enout_p[i] & 1 ) ^ ( ( soft_in[i*8] >> 15 ) & 1);
x += ( ( enout_p[i] >> 1 ) & 1 ) ^ ( ( soft_in[i*8+1] >> 15 ) & 1 );
x += ( ( enout_p[i] >> 2 ) & 1 ) ^ ( ( soft_in[i*8+2] >> 15 ) & 1 );
x += ( ( enout_p[i] >> 3 ) & 1 ) ^ ( ( soft_in[i*8+3] >> 15 ) & 1 );
x += ( ( enout_p[i] >> 4 ) & 1 ) ^ ( ( soft_in[i*8+4] >> 15 ) & 1 );
x += ( ( enout_p[i] >> 5 ) & 1 ) ^ ( ( soft_in[i*8+5] >> 15 ) & 1 );
x += ( ( enout_p[i] >> 6 ) & 1 ) ^ ( ( soft_in[i*8+6] >> 15 ) & 1 );
x += ( ( enout_p[i] >> 7 ) & 1 ) ^ ( ( soft_in[i*8+7] >> 15 ) & 1 );
}
return x;
}
uint8_t nr_dci_decoding_procedure(PHY_VARS_NR_UE *ue,
UE_nr_rxtx_proc_t *proc,
fapi_nr_dci_indication_t *dci_ind) {
@@ -920,15 +947,22 @@ uint8_t nr_dci_decoding_procedure(PHY_VARS_NR_UE *ue,
if (crc == n_rnti) {
LOG_D(PHY, "(%i.%i) Received dci indication (rnti %x,dci format %d,n_CCE %d,payloadSize %d,payload %llx)\n",
proc->frame_rx, proc->nr_slot_rx,n_rnti,rel15->dci_format_options[k],CCEind,dci_length,*(unsigned long long*)dci_estimation);
dci_ind->SFN = proc->frame_rx;
dci_ind->slot = proc->nr_slot_rx;
dci_ind->dci_list[dci_ind->number_of_dcis].rnti = n_rnti;
dci_ind->dci_list[dci_ind->number_of_dcis].n_CCE = CCEind;
dci_ind->dci_list[dci_ind->number_of_dcis].dci_format = rel15->dci_format_options[k];
dci_ind->dci_list[dci_ind->number_of_dcis].payloadSize = dci_length;
memcpy((void*)dci_ind->dci_list[dci_ind->number_of_dcis].payloadBits,(void*)dci_estimation,8);
dci_ind->number_of_dcis++;
break; // If DCI is found, no need to check for remaining DCI lengths
uint16_t mb = nr_dci_false_detection(dci_estimation,tmp_e,currentPtrDCI,L*108,n_rnti);
if (mb > 10) {
LOG_W(PHY,"DCI false positive. Dropping DCI index %d. Mismatched bits: %d/%d\n",j,mb,L*108);
continue;
}
else {
dci_ind->SFN = proc->frame_rx;
dci_ind->slot = proc->nr_slot_rx;
dci_ind->dci_list[dci_ind->number_of_dcis].rnti = n_rnti;
dci_ind->dci_list[dci_ind->number_of_dcis].n_CCE = CCEind;
dci_ind->dci_list[dci_ind->number_of_dcis].dci_format = rel15->dci_format_options[k];
dci_ind->dci_list[dci_ind->number_of_dcis].payloadSize = dci_length;
memcpy((void*)dci_ind->dci_list[dci_ind->number_of_dcis].payloadBits,(void*)dci_estimation,8);
dci_ind->number_of_dcis++;
break; // If DCI is found, no need to check for remaining DCI lengths
}
} else {
LOG_D(PHY,"(%i.%i) Decoded crc %x does not match rnti %x for DCI format %d\n", proc->frame_rx, proc->nr_slot_rx, crc, n_rnti, rel15->dci_format_options[k]);
}