see oai/openairinterface5g#227

When the UE connects to the eNodeB and receives its IP address from the
network, it calls system() to set it in the linux kernel world. This call
is not done in a realtime thread, but in the NAS, which uses its own thread,
independent of the realtime processing.

In some situations this totally disrupts realtime processing.

It is difficult to know precisely why that happens, but it seems that calling
fork(), as system() does, in a multi-threaded program is not a good idea. (So
say several people on the internet.) It is not clear why the softmodem is
impacted, but it seems that fork() is really what triggers the disruption.
Several tests lead to that conclusion.

To fix the problem, we create a child background process very early in main()
(before anything else basically). Then instead of calling system(), the main
process sends the string to the background process. The background process
gets the string, passes it to system() and reports the success/failure back
to the main process.

This solution involves a lot of system calls, but calling system() in the
first place is not cheap either. As long as no realtime thread uses this
mechanism, things should be fine. Time will tell.

Develop integration w11

Summary of changes:

- bug fixes
- RCC/RRU in automatic test setup
- more work on UE/MIMO
- LimeSDR support (5/10MHz)
- compilation under ubuntu 16.04, in particular kernel modules (nasmesh, ue_ip)

See merge request !148

We'll need to to do it in a separate thread/process.
To be done. In the meantime, put it back. It impacts
oaisim.

Not sure of this one, to be checked by TCL.

the argument 'coded_bits_per_codeword' has to be an array in
case of several codewords.

The calling sites have been adapted.

Today, only the first index is used, so calling sites where
'coded_bits_per_codeword' is an integer pass the address
of it. It is expected that 'dump_dlsch2' will check in the
future that there is one or two codewords and only access
'coded_bits_per_codeword[1]' when it's sure there are
really two codewords.

- pucchsim
- prachsim
- pdcchsim
- pbchsim
- mbmssim

Mostly, add and initialize the variable 'cpuf'.
Also, pdcchsim was calling rx_pdcch with wrong
arguments.

Same as previous commit 41dda3d3
but for dlsim.

The variables that were duplicated per processing thread
were adapted. 'cpuf' was defined and initialized.

One check introduced by previous commit was not necessary.

- README.txt modified
- tests added in test_case_list.xml
  (only for test setup v2)
- python code modified
- configuration files added

This work was done by Laurent Thomas.

Merge remote-tracking branch 'origin/Correction_for_dlsch_channel_level_calculation' into develop_integration_w11

On some hosts, compilations with the T tracer was failing.

The error was:
  common/utils/T/T.h:15:19: fatal error: T_IDs.h: No such file or directory

The problem was that in CMakeLists.txt some targets depend on the
pre-generation of T_IDs.h but this dependancy relation was not set,
so those targets could be generated before the T (it was the case
with HASHTABLE).

This commit fixes that. Basically, we take all the targets found in
"add_executable" and "add_library" and make them depend on the
T if the T is enabled. Almost all existing targets were added,
even those that may not need it.

The problem of this approach is that someone adding a new target
using the T will not necessarily add a dependancy there.

Another solution would be to generate T_IDs.h at "cmake" stage,
not "make" stage and use an "if (NOT EXISTS T_IDs.h)" to generate
the file. We lose the dependancy relation though.

Things may be changed if maintenance cost is too high.

768*8 is too small, in 20MHz, the phy-test mode
(in default mode?) has a buffer of size 6378.

Let's set the buffer size to the input's one plus 4 bytes
(to accomodate for CRC, not sure about this).

Develop integration w10

Summary of changes:
- MIMO for UE
- TDD in test setup
- bug fixes

See merge request !133

We use the odd/even dlsch corresponding to the configured
subframe. It may not be the right thing to do.

  for all processing including oaisim