[srslte-users] pdsch_ue question

[amr adel]

Hi Ismael,

I am using pdsch_ue and was trying to capture all uplink grants (DCI0
messages) sent by the enodeB
For that, I have done the following modifications:

1-In ue_dl.c I added the definitions for the 2 structures:
"srslte_ra_ul_dci_t" and "srslte_ra_ul_grant_t"
2-In the same file I used the 2 functions: "srslte_ue_dl_find_ul_dci" and
"srslte_dci_msg_to_ul_grant"
3-Since I don't know the specific CRNTIs in advance, I added a for loop in
pdsch_ue to scan all UE CRNTIs range from: 0x003D - 0xFFF3

I have the following observations:

1-When going through the UE specific search space, aggregation level 8
(L=3) was not showing
I found that in pdcch.c in the function: srslte_pdcch_ue_locations in the
for loop going through l=0:3, the 3 was preceded by a less than symbol. So,
I had to modify it to less than or equal to include (L=3) --> aggregation
level 8

2-Two different CRNTIs had the same uplink grant as follows:

[INFO]:  Attempting DL decode System Frame = 0, Sub-frame = 2 , RNTI = 17193
[INFO]:  Decoded CFI=1 with correlation 44.51, sf_idx=2
Decoded DCI: nCCE=0, L=0, msg_len=28, mean=1.388349, crc_rem=0x4329
[INFO]:  prb1: 49, prb2: 49, L: 6
 - Resource Allocation Type 2 mode : Localized
   + Frequency Hopping: No
   + Resource Indicator Value: 549
   + VRB Assignment: 6 VRB starting with VRB 49
 - Modulation and coding scheme index: 2
 - New data indicator: Yes
 - Redundancy version: 0
 - TPC command for PUCCH: --
 - Number of PRBs: 6
 - Modulation type: QPSK
 - Transport block size: 256

and

[INFO]:  Attempting DL decode System Frame = 0, Sub-frame = 2 , RNTI = 5188
[INFO]:  Decoded CFI=1 with correlation 44.51, sf_idx=2
Decoded DCI: nCCE=0, L=1, msg_len=28, mean=1.347141, crc_rem=0x4329
Decoded DCI: nCCE=2, L=1, msg_len=28, mean=1.399216, crc_rem=0xe313
Decoded DCI: nCCE=4, L=1, msg_len=28, mean=1.385574, crc_rem=0x3d56
Decoded DCI: nCCE=6, L=1, msg_len=28, mean=1.331550, crc_rem=0x9724
Decoded DCI: nCCE=0, L=2, msg_len=28, mean=1.373178, crc_rem=0x4329
Decoded DCI: nCCE=4, L=2, msg_len=28, mean=1.358562, crc_rem=0x4be2
Decoded DCI: nCCE=0, L=3, msg_len=28, mean=1.365870, crc_rem=0x1444
[INFO]:  prb1: 49, prb2: 49, L: 6
 - Resource Allocation Type 2 mode : Localized
   + Frequency Hopping: Yes
   + Resource Indicator Value: 549
   + VRB Assignment: 6 VRB starting with VRB 49
 - Modulation and coding scheme index: 2
 - New data indicator: Yes
 - Redundancy version: 0
 - TPC command for PUCCH: --
 - Number of PRBs: 6
 - Modulation type: QPSK
 - Transport block size: 256

Also, can you explain what does "[INFO]:  prb1: 49, prb2: 49" prb1 and prb2
refer to ?

3-Further more I inspected the binary dci messages of the reported CRNTIs
with DCI0 messages, and found some of them don't make sense. For example
one CRNTI had the following reported DCI0 binary message
: 0010110010111110000111101111
It is 28 bits in length which is fine. The bandwidth is 20 MHz so the last
bit in this message should be a padding bit (i.e. should be a 0)
This way I think that going through the whole CRNTI range and trying to
extract the DCI0 messages might give unrealistic ones. Hence, I believe I
should add a check to discard such messages

4-One last thing, I could not go through the whole range of CRNTI in the
pdsch_ue. I was monitoring RAM usage and I notice that memory consumption
would grow linearly with iterations. I tried to include the command
"srslte_ue_dl_free(&ue_dl);"  at the end of each iteration but still wasn't
successful (RAM consumption would grow to 100% and the pc would freeze
before ending the RNTI range). Any ideas what is so memory consuming and
that grows with iterations ?

Thank you,


-- 
Amr Abdelnasser
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