[srsran-users] Cannot find PLMN

Tue Jan 10 21:29:44 UTC 2023

Hello,

I'm trying to run an embms connection between two linux machines (debian
thinkpad p52 transmitting on the TX1 with a bladeRF A9, ubuntu 22.10 on a
chromebook receiving on RX1 with another bladeRF A9) and am following the
tutorial here:
https://docs.srsran.com/en/latest/app_notes/source/embms/source/index.html
but I'm unable to get the PLMN found or mbms service started.

I got a single-computer setup working with ZMQ by having two different
network spaces (one of which was called ue1) by following this tutorial:
https://docs.srsran.com/en/latest/app_notes/source/zeromq/source/index.html

In that case, the PLMN is found, the MBMS service starts, and the network
attaches. This is what I get on the UE when that happens:

dmrivers at snailshale:~/Code/srsRAN/srsRAN/build$  sudo ./srsue/src/srsue
--rf.device_name=zmq
--rf.device_args="tx_port=tcp://*:2001,rx_port=tcp://localhost:2000,id=ue,base_srate=23.04e6"
--gw.netns=ue1

Active RF plugins: libsrsran_rf_blade.so libsrsran_rf_zmq.so

Inactive RF plugins:

Couldn't open , trying /root/.config/srsran/ue.conf

Reading configuration file /root/.config/srsran/ue.conf...

Built in Release mode using commit 254cc719a on branch master.

Opening 1 channels in RF device=zmq with
args=tx_port=tcp://*:2001,rx_port=tcp://localhost:2000,id=ue,base_srate=23.04e6

Supported RF device list: bladeRF zmq file

CHx base_srate=23.04e6

CHx id=ue

Current sample rate is 1.92 MHz with a base rate of 23.04 MHz (x12
decimation)

CH0 rx_port=tcp://localhost:2000

CH0 tx_port=tcp://*:2001

Waiting PHY to initialize ... done!

Attaching UE...

Current sample rate is 1.92 MHz with a base rate of 23.04 MHz (x12
decimation)

Current sample rate is 1.92 MHz with a base rate of 23.04 MHz (x12
decimation)

.

Found Cell:  Mode=FDD, PCI=1, PRB=50, Ports=1, CP=Normal, CFO=-0.2 KHz

Current sample rate is 11.52 MHz with a base rate of 23.04 MHz (x2
decimation)

Current sample rate is 11.52 MHz with a base rate of 23.04 MHz (x2
decimation)

Found PLMN:  Id=00101, TAC=7

MBMS service started. Service id=0, port=4321, lcid=1

Random Access Transmission: seq=42, tti=2341, ra-rnti=0x2

RRC Connected

Random Access Complete. c-rnti=0x46, ta=0

Network attach successful. IP: 172.16.0.2

Software Radio Systems RAN (srsRAN) 3/1/2023 4:50:56 TZ:0

Received RRC Connection Release (releaseCause: other)

however, when I move the UE to a separate machine, although I am able to
find a cell, I'm unable to get the PLMN found, MBMS service started, or
network attached.

Instead, I get  (run on the UE receiving machine, running ubuntu )

dmrivers at casta:~/srsRAN/build$  sudo ./srsue/src/srsue
/root/.config/srsran/ue.conf

Active RF plugins: libsrsran_rf_blade.so libsrsran_rf_zmq.so

Inactive RF plugins:

Couldn't open , trying /root/.config/srsran/ue.conf

Reading configuration file /root/.config/srsran/ue.conf...

WARNING: cpu0 scaling governor is not set to performance mode. Realtime
processing could be compromised. Consider setting it to performance mode
before running the application.

Built in Release mode using commit 254cc719a on branch master.

Opening 1 channels in RF device=default with args=default

Supported RF device list: bladeRF zmq file

Trying to open RF device 'bladeRF'

Opening bladeRF...

Set RX sampling rate 1.92 MHz, filter bw: 192.Mhz

set RX frequency to 2560000000

set TX frequency to 2680000000

.

..

Found Cell:  Mode=FDD, PCI=1, PRB=50, Ports=1, CP=Normal, CFO=-0.2 KHz

Set RX sampling rate 11.52 Mhz, filter bw 9.22 Mhz

The good news though is that "Found Cell" only occurs if I run the enb on
the transmitting machine, which means that my receiving ubuntu machine must
be able to tell when I run the enb on my transmitting machine. And if I
have the UE running and then start the enb, it will also suddenly find the
cell. So this makes me think major things like carrier frequency and
bandwidth are not too badly off.

I don't get any errors on the logs in /tmp/ (the UE does get some warning
though about going backwards in time, detected slow task processing,"SFN
not yet synchronized, sending out of sync").

To try to fix these issues I tried:

Resetting the sib.conf with the sib.conf.mbsfn.example
<https://github.com/srsran/srsRAN/blob/master/srsenb/sib.conf.mbsfn.example>
file
as I had to in order to get ZMQ working, but it still didn’t fix anything

Deleting the ue1 namespace

Changing the configuration for mbms.conf to ip address on both machines
172.16.0.2

  Changing the configuration for mbms.conf to ip address on both machines
172.16.0.1 (this is what I stuck with, I think it's probably correct based
on the instructions here:
https://docs.srsran.com/en/latest/app_notes/source/embms/source/index.html)

  Changing the configuration for mbms.conf to ip address on sender to
172.16.0.1 and 172.16.0.2 on receiver

echo "performance" | sudo tee
/sys/devices/system/cpu/cpu*/cpufreq/scaling_governor

Changing sib.conf in the ue to include sib1 (some youtube video seems to
indicate sib1 is important for PLMN)

Orienting antennae at 90 degrees to each other

Running pdsch_ue and pdsch_enb in the srsran/build/lib/examples folders
(seems to connect to the cell, but didn’t really get any other information
from this, although the samplerate always seems to be outside of the
allowable range)

I just messed with earfcn settings, seems like changing the dl_earfcn to
1000 from 3350 on both enb.conf on transmitting machine and ue.conf on
receiving machine did not fix the problem

changing the MCC/MNC to 310/010 gave me some problems on the transmitting
computer:

"S1setup failed
Failed to initiate S1 connection. Attempting reconnection in 10 seconds
S1 Setup Failure. Cause: misc - unknown-PLMN"

so that's some weird internal issue. I'm not sure how to change the MCC/MNC
so that it doesn't cause this, so I'm unsure if the current MMC/MNC is the
problem. However, looking at the user_db.csv on the ubuntu receiving device
running the UE, I have a IMSI of 001010... which I think means the default
MCC/MNC of 001/01 should work fine. Unless I need to also manually change
the IMSI?

Other things I might try, if you don't have ideas:

   - Install a spectrum analyzer to be sure the signal is good enough
   https://osmocom.org/projects/sdr/wiki/Fosphor
   - The ideas here:
   https://docs.srsran.com/en/latest/usermanuals/source/srsenb/source/3_enb_trouble.html
   (is this the right troubleshooting spot?)
      - Ensure the radio being used is correctly calibrated and that the
      appropriate gain settings are used
      - check is that the LTE frequency band and EARFCN which you have
      configured are supported by the UE which you are using (I think it should
      be, because Eric says "What I like best about this is that from
what I can
      see, all LTE bands are supported" from here:
      https://ewf-engineering.com/a-quick-look-at-srslte-with-a-usrp-b200/
      but I am unsure how to determine this for sure)
      -
      https://ewf-engineering.com/lte-cell-searching-with-a-usrp-b200-srslte/
      seems to have an example where there was a "found cell" but not a "found
      plmn", there might be other ways I can alter to make it more like this
      configuration?
   - based on
   https://docs.srsran.com/en/latest/app_notes/source/embms/source/index.html
   I need to "Set m1u_if_addr to either a localhost address like 127.0.1.200
   or to your local IP of the network in which the eNodeB is available.". But
   I don't know which IP this should be. I think this is unlikey to be the
   solution because I think the embms is not really causing issues yet, it's
   the plmn not being found (I think).

Thanks,

Morgan
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