Some code in T tracers is used by both LTE and NR.
In LTE, we expect 10 subframes per frame, and the logging is done with
this assumption. We have one tick per subframe.
In NR, we deal with slots, not subframes. And we have n ticks per frame
(depending on mu). As of today, only n=20 is tested (corresponding to
mu=1).
A previous commit introduced 'subframes_per_frame' which had the correct
meaning for LTE but was truly 'slots per frame' for NR. This creates
confusion.
Let's replace 'subframe' by 'tick' to reduce confusion.
Think: NR with different number of slots per frame depending on mu.
The name 'subframes_per_frame' is a bit ambiguous. It is valid for LTE,
but for NR it should be 'slots_per_frame'.
For example, for sub-carrier spacing of 30KHz, we have 20 slots per
frame, so in this case subframes_per_frame = 20. In reality whatever
the numerology, there is always 10 subframes per frame in NR.
But how to name this variable which is used both for LTE and NR cases?
'subframes_or_slots_per_frame'? It's a bit long and also ambiguous.
Conclusion: no big deal I think. 'subframes_per_frame' and so be it.
T hacks: add new tracer ant0 and a tool to plot ofdm data from usrp or rfsim
(output or input)
The tool ant0 dumps IQ data to a file (or stdout) as float complex or short.
It is needed for a student's project. (Well, we could use record/extract, but
it's simpler.) The tool ofdm-plot is used to plot output or input signal from
gnb in the frequency domain. May be useful to debug, why not.
- Add _tracer_app_gnb and t_tracer_app_ue apps to common/utils/T/tracer/Makefile
- Add Data collection Service for gNB: common/utils/T/tracer/t_tracer_app_gnb.c
- Add Data Collection Service for UE: common/utils/T/tracer/t_tracer_app_ue.c
- Add Shared memory configuration (common/utils/T/tracer/shared_memory_config.h),
since We will have too much memory consumption on the stack if the
T-tracer is not fast enough to process the traces or if we have too
much traces. As a result, tracers start to capture data, write data in
shared memory, then close the T-Tracer after getting the recording of
N slots
- Support the operation of : COnfig, Record, and Stop
- Poll from Socket and not use get_events to mitigate long-time waiting
if there is no data in buffer or the UE is already released or crashed
- Add extra offset to improve data sync
When data is generated by "normal" T tracers, it should be fine.
But it might come from unknown sources and then content might be
"strange". So let's validate input data a bit more.
The way allocation is done (granularity of 64KiB) makes a crash more
difficult to achieve, but if a trace is exactly 64KiB, we miss 4 bytes
in the realloc and then anything may happen.
In NR with several layers, we may have MAC PDU of size bigger than 64KB,
which does not fit into a UDP buffer, destroying macpdu2wireshark.
Let's add an option to dump to a pcap file instead of using UDP packets.
The DLT 252 magic is used (check wireshark documentation to understand).
Run macpdu2wireshark with -h to see how to configure wireshark to read
the produced files.
Useful to debug realtime issues, for example when calling a periodical
routine, if it's not programmed carefully enough, it may be that the first
call takes way longer than the next ones (for example it uses some memory
that is not mapped in the process, leading to many page faults the first
time it's executed).
Having a periodic log for the timing of this routine with min/avg/max/count
will reveal that a call is way longer than average and will help in
finding where exactly in the code the time is spent, thanks to the ease
of use of the T tracer; you put T(T_XX, T_INT(1)) just before the code
you want to measure, you put T(T_XX, T_INT(0)) just after and time_meas
will show the delta time between those events. Then you cut the routine
in smaller pieces, measure with T(1)/T(0), and you finally reach the small
guilty part that takes too long.
In time_meas.c, when getting 0 for the event, we log delta time with
previous 1 for the event. "start_valid" was not cleared, so receiving
a second 0 without 1 in between may lead to wrong logging.
Should not happen in practice, but still, little bug.
(Note: we don't protect against streams of 1, but this case should also
not happen.)
MIB, SIB1, random access and regular scheduling are traced.
At the beginning of a connection (rrc setup request and rrc setup), the
RNTI is reported as 0. Might be fixed, somehow, if absolutely needed (not
sure).
This changes the way T_IDs are defined. The T_ID macro was using a integer to pointer cast in
order to provide type safety. This trick disables some compiler optimizations, as explained
here: https://clang.llvm.org/extra/clang-tidy/checks/performance/no-int-to-ptr.html.
Removing the type cast reenables the compiler optimizations.
Some people needed that.
Let's stop to 19 for the time being. It's tricky enough.
We can increase later if needed. (A previous commit
made the tracers to accept up to 32 variables.)
T_MAX_ARGS was 16 and some people start to use the T machinery with
more than 16 values. So be it. Let tracers be friendly and accept 32.
(More commits to follow for full support.)
Also why is T_MAX_ARGS in T_defs.h when it's only used by event.h?
Hum?
* the goal is to make the documentation more procedural and
descriptive and easier to understand
* added missing info in RLC-NR about reassembling of AM frames
Rakesh Mundlamuri