LTE: Is it necessary VoLTE call packets should use QCI 1 bearer for transmission ?

Question

Is it mandatory that for a UE in VOLTE call and data IP Address must be different (different bearer)

Answer 1

Hi,

No specification impose to use this bearer .But to make it general and divide the QOS flow they have defined certain Bearers. so all the UE manufacturer will follow this ,but it is ENB decision weather to use this or not.

Answer 2

What Jaganathan wrote is correct, however I want to add on here is that decision to initiate establishment of dedicated bearer is taken by IMS node i.e. Application Function and core network node i.e. PCRF.
Dedicated bearer is created at the core network first and then at eNodeB. I am not sure but if eNodeB responds to MME with the failure for dedicated bearer creation, then VoLTE call may be considered as failure.

Comments

ENodeB will send failure response of bearer allocation to MME, when the requested QOS cannot be served by it.

Answer 3

As per gsma doc for volte service description and implementation guidelines-

3.2 VoLTE Basic Call Flows
The VoLTE basic call flows are in accordance with 3GPP specifications for E-UTRAN/EPC,
IMS, and PCC. Please refer to 3GPP TS 23.401 [6], 3GPP TS 23.228 [5], and 3GPP TS
23.203 [4] respectively for further detailed information.

3gpp spec 23.401:

4.3.5.8 IMS voice over PS Session Supported Indication
The serving PLMN shall send an indication toward the UE during the Attach procedure and Tracking Area Update
procedures if an IMS voice over PS session is supported. The serving PLMN uses this indicator to indicate to the UE
whether it can expect a successful IMS voice over PS session according to TS 22.173 [73] with a bearer that supports
Conversational Voice as specified in TS 23.203 [6]. A UE with "IMS voice over PS" voice capability should take this
indication into account when establishing voice over PS sessions (as specified in TS 23.221 [27]) as well as when
determining whether to deactivate the special handling of ISR locally (as detailed in clause 4.3.5.6)

As per these specs , volte call pkts should go with qci 1 bearer.