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Bug-fix in Up-link with respect to PUSCH RE calculation when PTRS is enabled.

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Problem STATEMENT:
- When enabling PTRS flag in ulsim, there are multiple scrambling and decoding errors
  are observed even with high SNR values
  SNR 60dB   errors_scrambling 5546/13800
  Channel BLER 1.000000e+00, Channel BER 4.018841e-01

ANALYSIS:
- While extracting PTRS RE's, the PUSCH RE count was not updated accordingly for PTRS symbols.
- This results in 0 value LLR's on same positions which cause offset issue in later processing.

IMPLEMENTATION:
* nr_ulsch_demodulation.c
- In case of PTRS symbol, respective total number of PTRS RE's are subtracted from available
  PUSCH RE's in each PUSCH Symbol processing.

TESTING
* ulsim.c
- PTRS are enabled for testing and are not enabled by default by this commit.
- Available bit count is adjusted if PTRS is enabled.

VERIFICATION
- Total Scrambling errors after gNb processing shall be only 250 bits (in K=2)
  which were replaced with PTRS at UE side while transmission.
  SNR 60.000000 errors_scrambling 250/13800
  Channel BLER 0.000000e+00, Channel BER 1.811594e-02
- After adjusting available bits in ulsim.c for error calculation
  SNR 60.000000: n_errors errors_scrambling 0/13550
  Channel BLER 0.000000e+00, Channel BER 0.000000e+00

EXTRA
- Removed white-spaces from all above mentioned files
- Added Global/vim tags to .gitignore file
This commit is contained in:
Parminder Singh
2020-08-14 10:20:36 +02:00
parent f7dc17ec20
commit f4631f2186
4 changed files with 31 additions and 3 deletions
Download Patch File Download Diff File Expand all files Collapse all files
openair1/SIMULATION/NR_PHY/ulsim.c
+11 -1
View File
@@ -561,6 +561,7 @@ int main(int argc, char **argv)
uint16_t l_prime_mask = get_l_prime(nb_symb_sch, typeB, pusch_dmrs_pos0, length_dmrs); // [hna] remove dmrs struct
uint8_t ptrs_time_density = get_L_ptrs(ptrs_mcs1, ptrs_mcs2, ptrs_mcs3, Imcs, mcs_table);
uint8_t ptrs_freq_density = get_K_ptrs(n_rb0, n_rb1, nb_rb);
int ptrs_symbols = 0; // to calculate total PTRS RE's in a slot
if(1<<ptrs_time_density >= nb_symb_sch)
pdu_bit_map &= ~PUSCH_PDU_BITMAP_PUSCH_PTRS; // disable PUSCH PTRS
@@ -838,6 +839,15 @@ int main(int argc, char **argv)
//----------------- count and print errors -----------------
//----------------------------------------------------------
if (pusch_pdu->pdu_bit_map & PUSCH_PDU_BITMAP_PUSCH_PTRS) {
for (int i = pusch_pdu->start_symbol_index; i < pusch_pdu->start_symbol_index + pusch_pdu->nr_of_symbols; i++){
ptrs_symbols += ((gNB->pusch_vars[UE_id]->ptrs_symbols) >> i) & 1;
}
/* 2*5*(50/2), for RB = 50,K = 2 for 5 OFDM PTRS symbols */
available_bits = available_bits - (2 * ptrs_symbols * (nb_rb/((ptrs_freq_density)?4:2)));
printf("After PTRS subtraction available_bits are : %d \n", available_bits);
}
for (i = 0; i < available_bits; i++) {
if(((ulsch_ue[0]->g[i] == 0) && (gNB->pusch_vars[UE_id]->llr[i] <= 0)) ||
@@ -865,7 +875,7 @@ int main(int argc, char **argv)
errors_decoding++;
}
}
if (n_trials == 1) {
if (n_trials == 1 && errors_decoding > 0) {
for (int r=0;r<ulsch_ue[0]->harq_processes[harq_pid]->C;r++)
for (int i=0;i<ulsch_ue[0]->harq_processes[harq_pid]->K>>3;i++) {
if ((ulsch_ue[0]->harq_processes[harq_pid]->c[r][i]^ulsch_gNB->harq_processes[harq_pid]->c[r][i]) != 0) printf("************");