[srslte-users] does srsLTE support multiple bearers for a UE?

[Spencer Sevilla]

Hi all,

I'm currently trying to get VoLTE working using the following setup:
UE: a OnePlus 6T running LineageOS
eNB: srsLTE master branch
EPC: open5gs (formerly NextEPC)

I think I'm very close right now! Currently, I can see the UE attach to the
EPC, setup a default bearer to the Internet (APN "internet"), and then ask
to setup a second bearer for IMS (APN "ims"). However, it looks like this
second bearer setup process fails (or at least the UE thinks it does), and
then the UE asks again 5 seconds later.

In my PCAP (taken between the eNB and EPC) I can see the following exchange
for the ims APN:
eNB -> EPC: UplinkNASTransport PDN connectivity request
eNB <- EPC: E-RABSetupRequest, Activate default EPS bearer context request
eNB -> EPC: E-RABSetupResponse

Here, according to good example PCAPs, I expect to see the following
message:
eNB -> EPC: UplinkNASTransport Activate default EPS bearer context accept
but instead, I don't see anything at all - and then 5 seconds later, the UE
sends another PDN Connectivity Request and repeats.

I am planning to test with a commercial eNB tomorrow, but in the meantime I
was wondering if anyone could tell me if srsLTE supports this or not? I saw
in the GitHub issues (and mailing list archive) that srsLTE does not yet
support dedicated bearers, but this is simply asking to setup a second
default bearer. Or maybe I'm mistaken, and this would actually be
considered a dedicated bearer? Any insight/advice here would be greatly
appreciated.

Thanks a ton!
Spencer
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