SIP message 401 unauthorized, call drop event

Hi Experts.
Please help analyse SIP message 401 unauthorized, call drop event occurred here.


Check what happened on RRC why you deregister.
401 Unauthorised is normal behavior after Register.

Before RRC reconfig no EPS bearer identity assign in ESM response.

You had RRCConnectionRelease message on top.
Check whay that happened before.
After that RRCConnectionReconfiguration message whith reconfigured DRBs came after your selected message.

There is not rrcconnectionRelease before ESM response.
Which message you refer to?

Second row.

Please check whether Dynamic QoS Modification (E//) or eRAB Modification (N//) is activated/not.

401 unauthorised is a normal msg during call flow for authorization…check 503 service seems ue is not able to perform requested service. Also ue was deregistered as mentioned by Spale.

I can’t see any other abnormal event but IMS voice server de registered abnormally. Also HHO intrafreq occur to a logical cell b4 rrc connection rel.

What is recommendation for Huawei?

Also: I have all drops on this one location with multiple attempt failures.



With RRcconnRelease (probably due to radio or problem with HO) all 3 bearers are released.
UE goes to idle and do again RRC establishment.
After that need RRCConnReconfiguration to do reactivation of all 3 bearers.
Check radio conditions before Rrc release message.
And maybe you will need to check S1AP interface from eNB side. Those consecutive drops looks suspicious.

Any inputs on

  1. Affected QCI
  2. KPI Counter which is affected


Looks like call failed at 503 Unavailable.

SIP IMS Call flow:

Seems SIP/IMS signalling is successful.
The issue is voice bearer couldn’t be allocated as RRC reconfiguration message is missing (to update default radio bearer to voice bearer) in L3 as per shared snap.
In general multiple reasons can be… unsupported encryption algorithm/voice codec causing de-registration, some underlying enb level parameter is missing if it’s not NW level issue, Bad Coverage (levels, quality), choked capacity, TNL failures, S1 Interface failure, etc.

1 Like

RF environment doesn’t look bad for consecutive drops.

I didn’t get this message after 401 unauthorized.

RSRP is ok but check RSRQ.

Chek again your first photo.
After 401 you will see UL Register and 200 ok on DL -> successfully registration.