COTS UE keeps disconnecting

[mohit4444]

Hi
My setup is as follows:
USRP x310 connected via a 1G link
Pixel 8 pro
sysmoISIM-SJA5-9FV
Dockerised 5g core

The phone is able to attach to the network but it keeps disconnecting and reconnecting as shown in the 5g core log below:

I've set

Infinite timeout: Set NR_TIMER_WAIT_IMS_REGISTRATION from default 180 to -1
Disable timeout: Set SUPPORT_IMS_NR_REGISTRATION_TIMER from default 1 to 0

When the phone is connected, there is no internet access

I'm currently using a 1G link instead of 10G link to connect my USRP x310 to my server. Could that be causing this issue. I've attached all the logs for your reference. Any help would be appreciated!
configs.zip

[robertfalkenberg]

Hi,

according to the logs there are already some packets exchanged through DRB1, which is a good sign, i.e. the UE tries to send some (background) traffic through the 5G link.

For the lack of internet access, it might be a routing issue. Try to enter the open5GS container via console and ping the IP address of the UE to see if it responds. If so, you might need to configure routes between core and the internet.

For the disconnect after 180s, please double check these IMS-related tweaks you already posted. Sometime those settings are reset, e.g. if you change the uSIM (and sometimes the UE just forgets about those and you have to configure again).

[asheeshtripathi]

@mohit4444, Please check the tunnel status and the NAT rules:
This creates the tunnel, enables IP forwarding and adds NAT rule. You should get Internet access when you run following:
sudo ip tuntap add name ogstun mode tun
sudo ip addr add 10.45.0.1/16 dev ogstun
sudo ip addr add 2001:db8:cafe::1/48 dev ogstun
sudo ip link set ogstun up
sudo sysctl -w net.ipv4.ip_forward=1
sudo sysctl -w net.ipv6.conf.all.forwarding=1
sudo iptables -t nat -A POSTROUTING -s 10.45.0.0/16 ! -o ogstun -j MASQUERADE
sudo ip6tables -t nat -A POSTROUTING -s 2001:db8:cafe::/48 ! -o ogstun -j MASQUERADE
sudo ufw disable
sudo iptables -I INPUT -i ogstun -j ACCEPT

But I see your UE is getting IP 10.45.1.X, so make changes accordingly. There should already be a tunnel created. If you do an ifconfig, you will see something with the name of ostun.

Also, I see the RF power levels and OTA channels conditions are good (CQI is 15), so it is not the RF that is causing the discoonect.

I have only tested with APN "internet" with a lot of different COTS UEs. You can try that as well. Also, as Robert mentioned, IMS-related tweaks need to be double-checked. We have tried these tweaks with the Pixel 6, and it works for us.

[mohit4444]

Hi @robertfalkenberg and @asheeshtripathi . Thank you for taking the time to look into this.
I'm able to test uplink and downlink by pinging but i'm still not able to get internet access on the UE. I'll dig deeper into the routing.