Change in osmo-gsm-tester[master]: 4g: Introduce ZMQ GnuRadio stream broker

[pespin]

Hello Jenkins Builder, srs_andre, 

I'd like you to reexamine a change. Please visit

    https://gerrit.osmocom.org/c/osmo-gsm-tester/+/20521

to look at the new patch set (#4).

Change subject: 4g: Introduce ZMQ GnuRadio stream broker
......................................................................

4g: Introduce ZMQ GnuRadio stream broker

srsENB currently creates 1 zmq stream (1 tx, 1 rx) for each cell (2 if
MIMO is enabled). Each cell transceives on a given EARFCN (and several
cells can transmit on same EARFCN).

However, for handover test purposes, we want to join all cells operating
on the same EARFCN to transceive on the same ZMQ conn, so that an srsUE
can interact with them at the same time (same as if the medium was shared).
Furthermore, we want to set different gains on each of those paths
before merging them in order to emulate RF conditions like handover.

In order to do so, a new element called the Broker is introduced, which
is placed in between ENBs and UEs ZMQ conenctions, multiplexing the
connections on the ENB side towards the UE side.

A separate process for the broker is run remotely (ENB run host) which
listens on a ctrl socket for commands. An internal Broker class is used
in osmo-gsm-tester to interact with the remote script, for instance to
configure the ports, start and stop the remote process, send commands to
it, etc.
On each ENB, when the rfemu "gnuradio_zmq" rfemu implementation is selected
in configuration, it will configure its zmq connections and the UE ones to
go over the Broker.

As a result, that means the UE zmq port configuration is expected to be
different than when no broker is in used, since there's the multiplexing
per EARFCN in between.

In this commit, only 1 ENB is supported, but multi-enb support is
planned in the future.

The handover test passes in the docker setup with this config:
"""
OSMO_GSM_TESTER_OPTS="-T -l dbg -s 4g:srsue-rftype at zmq+srsenb-rftype@zmq+" \
	"mod-enb-nprb at 6+mod-enb-ncells@2+mod-enb-cells-2ca+suite-4g at 10,2+" \
	"mod-enb-meas-enable -t =handover.py"
"""

and in resources.conf (or scenario), added:
"""
enb:
  ...
  cell_list:
    - dl_rfemu:
       type: gnuradio_zmq
    - dl_rfemu:
        type: gnuradio_zmq
"""

Note that since the broker is used, there's not need for mod-srsue-ncarriers at 2
since the broker is joining the 2 enb cells into 1 stream on the UE side.

Change-Id: I6282cda400558dcb356276786d91e6388524c5b1
---
M src/osmo_gsm_tester/obj/enb.py
M src/osmo_gsm_tester/obj/enb_amarisoft.py
M src/osmo_gsm_tester/obj/enb_srs.py
M src/osmo_gsm_tester/obj/ms_srs.py
M src/osmo_gsm_tester/obj/rfemu.py
A src/osmo_gsm_tester/obj/rfemu_gnuradio_zmq.py
M sysmocom/scenarios/mod-enb-cells-2ca.conf
A utils/bin/osmo-gsm-tester_zmq_broker.py
8 files changed, 515 insertions(+), 31 deletions(-)


  git pull ssh://gerrit.osmocom.org:29418/osmo-gsm-tester refs/changes/21/20521/4
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Gerrit-Project: osmo-gsm-tester
Gerrit-Branch: master
Gerrit-Change-Id: I6282cda400558dcb356276786d91e6388524c5b1
Gerrit-Change-Number: 20521
Gerrit-PatchSet: 4
Gerrit-Owner: pespin <pespin at sysmocom.de>
Gerrit-Reviewer: Jenkins Builder
Gerrit-Reviewer: srs_andre <andre at softwareradiosystems.com>
Gerrit-MessageType: newpatchset
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