We have a crash:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread 0x7fff7387d700 (LWP 1944)]
ulsch_decoding (eNB=eNB@entry=0x7fffaf73b010, proc=proc@entry=0x7fffaf73b480,
UE_id=UE_id@entry=0 '\000',
control_only_flag=control_only_flag@entry=0 '\000',
Nbundled=<optimised out>, llr8_flag=<optimised out>)
at /roux/merge/openairinterface5g/openair1/PHY/LTE_TRANSPORT/ulsch_decoding.c:1450
1450 *((__m256i *)&ulsch_harq->e[iprime]) = *((__m256i *)&y[j2]);
This commit reduces the apparition of the crash, but does not
eliminate it completely.
To be fixed after integration.
1- implement max harq retrans
2- bug in harqId > 1 for dci format 1A
3- wrong G computation
4- bug in harq UL for scheduling flag
5- initial sync, limit freq offset to 150Hz
- add progess bar report
- reduce ssh max_tries to 10
- cleanOldPrograms -> change kill cmd line to be able to run autotest on same machine than lte-softmodem (thanks Rohit & Gabriel)
- Cleanning output prints
- add --skip-machine-preparation on cmd line
- add --skip-sanity-check on cmd line
- add HTML REPORT (no-S1 only)
- add XML detailled report (no-S1 only)
The PHICH generation is wrong.
HARQ process X is uplink scheduled at TTI n.
At TTI n+4 the eNB receives the data.
At TTI n+8 the eNB sends ACK/NACK on the PHICH.
The problem is that PHICH generation is done after scheduling.
And PHICH generation uses "first_rb" and "n_DMRS" to compute
"ngroup_PHICH" and "nseq_PHICH".
So at TTI n+8 if the eNB has reused the HARQ process X for
a new uplink scheduling the values "first_rb" and "n_DMRS"
may have changed.
We need to use the previous values.
One solution would have been to do PHICH generation before
scheduling. The problem is that "generate_phich_top" does more
than PHICH generation. It has to setup parameters to sort of
"emulate" a DCI0 in case of retransmission scheduled without
DCI0. So part of it has to be done after scheduling. We would
have to split the function.
The simple adopted fix is to store old values of "first_rb"
and "n_DMRS" and use those values in "generate_phich_top".
This fix has only been tested with FDD. TDD may miserably fail.
The case of a CRC == 0 is legal.
After discussion with Raymond, it is also possible to have all
bits at 0 (and so a CRC==0) if there is no transmission and thus
not much energy.
So this hotfix may introduce new problems (false decoding).
A future work is to handle this case properly by not calling the
turbo decoder if there is not enough energy received.
The problem might manifest itself more in the UE part, especially
when it tries to decode MIB and/or SIB (if I understood correctly).
Cedric Roux