SrsUE fails to connect to gNb most of the time.

[MaryamJavedEE]

We are using split 8 based over the air setup. Total of three laptops are used. Two laptops run the srsran UE whereas one laptops runs the 5G gNb. The gNb easily connects to AMF ( the core). The problem is that the UE fails to attach to the gNb. Even after several tries, the RRC connects but it releases almost immediately after a few seconds and IP address shows rarely very rarely.
We are at a loss to know what exactly is the problem. Our goal is to attach two UEs at the same time to the gNb but we can't even successfully attach one without RRC being released. Would really appreciate some help.

[asheeshtripathi]

Adjust the Tx and Rx powers of gNB and UE USRP (depending on physical location, USRP etc). Also, it is worth looking at the inactivity timer in the gNB file, for issues where you see RA Procedure completes, RRC Connected, then immediately the RRC released:
cu_cp: inactivity_timer: 7200 # Sets the UE/PDU Session/DRB inactivity timer to 7200 seconds. Supported: [1 - 7200].

Have a look at this thread: https://github.com/srsran/srsRAN_Project/issues/859

[MaryamJavedEE]

Hi! Thanks alot Asheesh! We tried it just when you told this but without any success unfortunately. Do you have any other tips for us to try?

[asheeshtripathi]

The above thread (#859) has a lot of information on attaching srsUE with srsgNB. Also, other associated threads can be referred to for troubleshooting the issue. The RF environment, testbench setup, and the configurations could prevent the UE from attaching or detaching after the attach. Do you see underflows, overflows, or late packet messages when you run the UE or gNB machine? Also, please take a look at the core logs to see if the registration process goes through and if the UE gets the IP. To get effective suggestions and help from the community, it would be better to provide the setup details, configuration files, and logs, highlighting the exact issue.

[MaryamJavedEE]

Hello! We did manage to solve this! You were right! Adding the inactivity timer: 7200 definitely helped. We also added the the lines
rrc:
force_reestablishment_fallback: true
rrc_procedure_timeout_ms: 1000
By doing all of this we were able to connects both UEs at the same time with stable RRC connections and IPs.
But there's is another problem we are facing now
the UE attaches to the gNB ,the RRC connects and IP adresses show on both UEs, but it releases immediately the moment we try to ping to and from the UE and base station.
We are at a loss to know what exactly is the problem. Our goal is to attach two UEs at the same time to the gNb but we can't even successfully ping one uplink or downlink without RRC being released. Would you happen to know something about it?
Thanks again Asheesh!

[asheeshtripathi]

look at the gNB console metrics for signal quality. I would recommend first trying with a single UE and making it work, then trying the second UE. Look for CQI and RSRP values in the gNB console. Make sure that the you have added route to be able to do ping or iperf: refer https://docs.srsran.com/projects/project/en/latest/tutorials/source/srsUE/source/index.html#routing-configuration