QCI1 attempt in LTE at a particular sector

Question

Can some tell me what i need to check if there is no QCI1 attempt at a particular sector.

Answer 1

QCI 1 is associated with voice data in LTE. If you are suspecting QCI 1 is not being established at a particular sector then I would suggest to verify following things:
- Towards network side
1. EPS network feature support field in attach accept message. This field contains various flags and one of the flags indicates "IMS over PS session in S1 mode" supported/un-supported.
2. If network supports IMS over PS session then UE can trigger IMS registration towards IMS network. IMS registration messages are transferred using QCI = 5 bearer which is a default bearer of IMS signalling. This bearer can be established as part of initial registration or as a separate PDN connectivity procedure.
3. Verify for successful execution of ERAB setup procedure for QCI 1. If it is not happening then eNodeB would be sending exact error code to network.
- Towards UE side
1. After SIP messages exchanged, verify for incoming RRC connection reconfiguration from eNodeB with NAS "Activate Dedicated EPS bearer context Request" message.

If VoLTE call is happening is other sector but not happening in few sectors then narrow down your debugging area at S1-AP interface messages such as E-RAB setup Request (for QCI 1) and UE logs after SIP registration.