By default, eNB are now frame/subframe synchronized in time (that is they
all transmit the exact same frame and subframe at the same time).
Use -no-sync to disable synchronization.

Some bugs were fixed:
- memory initialized to 0
- ignore SIGPIPE that was delivered sometimes when an eNB disconnects
- set tx_sample_advance to 40, which is used in the usrp lib of openair
  (srsUE did not connect well with 0)

The main goal of this commit is to be able to perform X2 handover
using a COTS UE and two 'simulated' eNB, each running on a separate
computer, but both using the same USRP device to send and receive IQ
data over the air. By changin the gains at runtime using a small script,
it is possible to trigger X2 handover based on the A3 measurement report
as sent by the UE.

The documentation on how to perform X2 handover with only one
USRP device is in channel_simulator/README.x2_handover.

This commit improves performances by changing the processing
in libchannel_simulator.so.

The ultimate goal is to run x2 handover with a real UE and a single
physical device. For that we need to run two eNBs, which requires a
remote computer. The processing as done before this commit was badly
using the network link between the two machines, killing realtime.

This commit introduces a TX thread to cut the "read, write, read, write"
loop of before. This loop led to a maximum throughput of 90 Mb/s
(sum of RX and TX, which are each 45 Mb/s) on a test environment.
But for 25 RBs we need around 500 Mb/s for realtime.

The problem, I think, is that there is some latency when sending and
receiving data to the network device. This is not a problem of TCP
(apart from the NODELAY thing). Doing "read, write, read, write"
with an UDP socket led to the same bad throughput. Also, we don't
send a full subframe at a time, but only 512 samples, which may lead
to more latency (sending full subframes was not tested).

On the test environment, just running the eNB and the channel_simulator
we reach 740 Mb/s with this commit (the link is a direct connection
of two machines with 1Gb ethernet; on one machine it's a 'native'
ethernet port, on the other an USB 3 <-> ethernet adapter is used;
running uplink and downlink iperf and bwm-ng to monitor network, we
see the link can do 2 Gb/s cumulated).

The UE does not work anymore with this commit because we require
some TX all the time. It has also not been tested with TDD mode,
only FDD.

Later commits may solve these problems.

This commit introduces the ability to connect a real hardware device to
the channel simulator.

It is possible to run an eNB with the libchannel_simulator.so as
liboai_device.so and the "usrp" program and have both connected
as if the eNB was directly talking to the USRP device.

For that, a channel can now have a "sample_advance". (The USRP receives
data from the air for subframe N and sends data for subframe N+x in the
future. In this commit x = 2 subframes.)

The following commands can be run to connect an eNB and the "usrp"
program in FDD mode with 25 RBs.

First, run the the channel simulator. In the directory channel_simulator:

    ./channel_simulator

To run usrp, as root, in the directory channel_simulator/usrp:

    ./usrp

To run the eNB, as root:

    CHANNEL_SIMULATOR_RX_FREQUENCY=2 CHANNEL_SIMULATOR_TX_FREQUENCY=1 CHANNEL_SIMULATOR_TX_SAMPLE_ADVANCE=15360 ./lte-softmodem -O [config file]

Then it is possible to connect a COTS UE.

It is also possible to connect openair UE which uses libchannel_simulator.so
as liboai_device.so. For that, run, as root:

    CHANNEL_SIMULATOR_RX_FREQUENCY=1 CHANNEL_SIMULATOR_TX_FREQUENCY=2 CHANNEL_SIMULATOR_RX_SAMPLE_ADVANCE=15360 ./lte-uesoftmodem -C 2680000000 -r 25 --ue-rxgain 140 --nokrnmod

Connecting both the openair UE and a COTS UE, it is possible to send traffic
between the two.

Note: performances need to be improved.

Note 2: the program "channel_simulator" now requires AVX2 instruction set.

Develop Integration Branch: 2019 week 41

See merge request oai/openairinterface5g!689

    initial support for iperf in distributed environment
Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

  - Add more IP routes / rules
  - OAI UE should be pingable!
  - Relative time column added to HTML report
Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

  -- Adding the python framework of build and test to inria r2lab pipeline
  -- R2LAB pipeline has logCollections and artifacts storing
  -- Python framework should support latest Rel14 OAI openair-cn/cn-cups EPC
  -- Pipeline uses the latest version of booking-lease script (by duration)
  -- Support for distributed smartphone adb servers
  -- Initial scenarios:
     ** Build on one OAI 4G eNB and one OAI 4G UE
     ** Test in FDD band7 / 5MHz / TM1 in noS1 configuration
     ** Test in FDD band7 / 5MHz / TM1 with latest OpenAir-CN-CUPS --> just attachment
Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

Develop Integration Branch: 2019 week 36

The following MR are included:

* MR 653 : Feature LTE-M PUSCH CE - 8 Repetitions
* MR 654 : Rfsimu config and CI scripting updates

  -- Properly stopping FlexRan Ctl in case of failure
Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>

  -- IperfNoS1 when eNB crashed
  -- LTE-M module failed attachment
  -- LTE-M module pinging
Signed-off-by: Raphael Defosseux <raphael.defosseux@eurecom.fr>