The discard timer is used by the PDCP layer to discard packets that were not
transmitted to RLC after some time.
We don't really need it for the moment, maybe never for the default
bearer which is a best-effort bearer passing all kind of IP traffic.
Maybe for voice over IP kind of traffic it's important, or realtime
applications.
I ran an iperf UDP uplink test and saw no error on the PHY layer but still
lots of packets lost in the iperf logs, which was very surprising. By
analyzing the logs in wireshark I saw that, with the current scheduler,
an IP packet sent by the UE took 40ms to be sent piece by piece to the
gNB, and then the next uplink IP packet was never sent at all because
the discard timer was expired, leading to the high count of packets lost
in the iperf logs.
So let's put infinity for the moment for the discard timer. From my
understanding of the moment it's not a problem. If for some reason we
should set it to some non-infinity value, then we can change later.
1) Only count new transmission as scheduled bytes (which is then
compared against the BSR)
2) When subtracting scheduled bytes after successful reception, subtract
TBsize from correct HARQ process
- a new section in the configuration file to select security algorithms,
with new code to deal with it
- cleanup CG-ConfigInfo: specs seem to indicate that we must not
add mcg_RB_Config; the gNB has to deal with that
- as a consequence, modify fill_default_rbconfig() that is called in
every cases and needs security and bearer parameters
The new section in the configuration file looks like:
security = {
# preferred ciphering algorithms
# the first one of the list that an UE supports in chosen
# valid values: nea0, nea1, nea2, nea3
ciphering_algorithms = ( "nea0", "nea2" );
# preferred integrity algorithms
# the first one of the list that an UE supports in chosen
# valid values: nia0, nia1, nia2, nia3
integrity_algorithms = ( "nia0" );
};
The code is forced to use nea2, no matter what the UE supports.
After 2^18 PDCP packets, it will fail to work (we don't use HFN yet).
These limitations will be fixed in later commits.
The existing security function was not reused, because it does too
much memory allocation and initializes the security context at each
ciphering. So here comes nr_pdcp_security_nea2_cipher(). And also
the ciphering is done inplace. To be changed if necessary.
* add the RA process to handle to command parameters
* Do not create the RAR_pdu into an intermediate array, but directly
into the nFAPI TX_req
* Slightly restructure nr_generate_Msg2() to first make AssertFatal()
checks, then proceed allocating
As the precedent commit, this commit deals with the realtime problems
that we currently have on the CI bench.
For DL HARQ feedback, nFAPI does not give us the HARQ process ID.
Instead, we have to figure this out "from timing", i.e., if we trigger
PUCCH reception, we will get a message with HARQ if we instructed the
PHY to do so. If we have real-time problems, it seems (I cannot verify:
don't have real time problems) that we do not get the nFAPI message with
HARQ feedback. Thus, we need to skip the HARQ processes that should have
been processed in the past, which happens in this commit.
At the time of this commit, the CI has realtime issues. This can mean
that the HARQ result is delivered in a delayed fashion. Before this
commit, we were asserting on whether the slot corresponds to the HARQ
process's expected feedback slot, but a particular feedback might be
delayed under realtime issues, and we actually don't care about the
timing since we get the HARQ process ID.
Instead, we loop through the HARQ processes for which we wait for a
feedback in the beginning until we have the right process (which did not
seem to cause a problem till now, but who knows.
Cedric Roux