[srslte-users] question on epc, ue and epc startup order

[J Giovatto]

Hi folks,

I have a question about startup order w/r to ue, enb and epc.

In our tests ue, enb and epc may be mobile and thus may not always be
within reach at any given time.

This is all related to running in emulation mode (streaming rf samples)
so my results may be differ than the norm but here is what I see ...

With the following startup sequence I can see the ue attach within a few
seconds as expected.

1) epc + short pause < 2 sec

2) enb + short pause < 2 sec

3) ue  + short pause  < 2 sec

Random Access Transmission: seq=1, ra-rnti=0x2
RRC Connected
Random Access Complete.     c-rnti=0x47, ta=0
Network attach successful. IP: 172.16.0.2
Software Radio Systems LTE (srsLTE)

But with this sequence below I never see a ue attach log ...

1) enb + short pause < 2 sec

I see the enb retry every 10 sec log

Failed to connect to MME - retrying in 10 seconds
Failed to connect to MME - retrying in 10 seconds
Failed to connect to MME - retrying in 10 seconds

2) ue    + long pause ~ 30 sec

Random Access Transmission: seq=1, ra-rnti=0x2
RRC Connected
Random Access Complete.     c-rnti=0x46, ta=0

3) epc


10:54:06.870503 [S1AP] [I] Received S1AP msg. Size: 49
10:54:06.870658 [S1AP] [I] Received initiating PDU
10:54:06.870687 [S1AP] [I] Received S1 Setup Request.
Received S1 Setup Request.
S1 Setup Request - eNB Name: srsenb01, eNB id: 0x19b
10:54:06.870719 [S1AP] [I] S1 Setup Request - eNB Name: srsenb01, eNB
id: 0x19b
10:54:06.870735 [S1AP] [I] S1 Setup Request - MCC:001, MNC:01, PLMN: 61712
S1 Setup Request - MCC:001, MNC:01, PLMN: 61712
10:54:06.870752 [S1AP] [I] S1 Setup Request - TAC 7, B-PLMN 0
S1 Setup Request - TAC 7, B-PLMN 0
S1 Setup Request - Paging DRX 2
10:54:06.870773 [S1AP] [I] Adding new eNB context. eNB ID 411
Sending S1 Setup Response
10:54:06.871967 [S1AP] [I] Sending S1 Setup Response
10:54:06.872066 [S1AP] [D] Waiting for SCTP Msg

If I restart the ue then the attach is successful.

logs available on request.

Regards

Joe