[srslte-users] UE attach but can't create VPN

[Theo Gurgey]

Hello,

I have successfully done my installation with srsLTE on one machine Ubuntu
18.04, with a LimeSDR mini. The LimeSDR mini is linked to the UE (LTE
modem) with coaxial cable with -20 dB attenuation on RX side and -30 dB
attenuation on TX side.

Since my UE has only one coax port, I use a splitter.

The air conditioning next to the Lime cools it down, and the card is well
connected to an USB 3 port.

I can launch srslte, and attach the UE to the network, even if the
attach procedure can be fickle (see log file printed below).

However, I want to establish a VPN connection between my UE and a VPN
server, but I can't !
The VPN server receives the connexion request, it answers but the answer is
not received by my UE. I can clearly see messages from both sides on the
srslte machine, on the spgw interface, but it seems the LimeSDR doesn't
send back the answer to the UE (see attached file srs_spgw_sgi.png). My UE
retransmit perpetually connexion request so.
Sometimes for a short period of time <1s, the packets are well received by
the UE and then it overlaps.

The " [ERROR] Tx Calibration: MCU error 4 (SXT tune failed) " worried me
but I don't know if it is the cause of my problems since I have seen many
people having the same errors on forums.

What can I do? All suggestions are welcome.

Regards,
Théo




##########################  srs_spgw_sgi
#######################################

[image: srs_spgw_sgi1.jpg]
##############################################################################



##############################################################################
################################### enb log
####################################
##############################################################################
---  Software Radio Systems LTE eNodeB  ---

Reading configuration file /home/user/.config/srslte/enb.conf...

Built in Release mode using commit c892ae56b on branch master.

/home/user/SRS-LTE/srsLTE/srsenb/src/enb_cfg_parser.cc.883: Force DL EARFCN
for cell PCI=1 to 6200

Opening 1 channels in RF device=soapy with args=rxant=LNAH,txant=BAND2
Soapy has found device #0: addr=24607:1027, driver=lime, label=LimeSDR Mini
[USB 3.0] 1D538755289563, media=USB 3.0, module=FT601, name=LimeSDR Mini,
serial=1D538755289563,
Selecting Soapy device: 0
[INFO] Make connection: 'LimeSDR Mini [USB 3.0] 1D538755289563'
[INFO] Reference clock 40.00 MHz
[INFO] Device name: LimeSDR-Mini
[INFO] Reference: 40 MHz
[INFO] LMS7002M register cache: Disabled
Setting up Rx stream with 1 channel(s)
Setting up Tx stream with 1 channel(s)
[INFO] RX LPF configured
[INFO] Filter calibrated. Filter order-4th, filter bandwidth set to 5
MHz.Real pole 1st order filter set to 2.5 MHz. Preemphasis filter not active
[INFO] TX LPF configured
Available device sensors:
 - clock_locked
 - lms7_temp
Available sensors for Rx channel 0:
 - lo_locked
Setting Rx antenna to LNAH
Setting Tx antenna to BAND2
[ERROR] Tx Calibration: MCU error 4 (SXT tune failed)
[INFO] Rx calibration finished
State of gain elements for Rx channel 0 (AGC not supported):
 - TIA: 9.00 dB
 - LNA: 30.00 dB
 - PGA: -4.00 dB
State of gain elements for Tx channel 0 (AGC not supported):
 - PAD: 45.00 dB
 - IAMP: 0.00 dB
Rx antenna set to LNAH
Tx antenna set to BAND2

==== eNodeB started ===
Type <t> to view trace
[INFO] RX LPF configured
[INFO] Filter calibrated. Filter order-4th, filter bandwidth set to 11.52
MHz.Real pole 1st order filter set to 2.5 MHz. Preemphasis filter not active
[INFO] TX LPF configured
Setting frequency: DL=796.0 Mhz, UL=837.0 MHz for cc_idx=0
RACH:  tti=9271, preamble=31, offset=13, temp_crnti=0x46

RACH:  tti=3571, preamble=42, offset=13, temp_crnti=0x47
Disconnecting rnti=0x46.
User 0x47 connected
LRACH:  tti=9821, preamble=27, offset=13, temp_crnti=0x48
Disconnecting rnti=0x48.
Disconnecting rnti=0x47.
RACH:  tti=9991, preamble=15, offset=13, temp_crnti=0x49
RACH:  tti=9931, preamble=20, offset=13, temp_crnti=0x4a
RACH:  tti=4221, preamble=21, offset=13, temp_crnti=0x4b
User 0x4b connected

##########################################################################
##########################################################################
##########################################################################

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