If data is disabled in VoLTE device, how will UE know the PCSCF address for SIP registration?

Can someone explain if my mobile data is disabled in VoLTE device, how will UE know the PCSCF address for SIP registration?

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Default bearer still data is active cant be OFF in LTE n above.

Even if mobile dat is OFF, its still enabled in the background.

Do you mean default bearer of internet is still get created if data is disabled in the UE?

Yes, correct.

When your mobile data is disabled in a Voice over LTE (VoLTE) capable device, the UE (User Equipment) may face challenges in knowing the PCSCF (Proxy-Call Session Control Function) address for SIP (Session Initiation Protocol) registration. VoLTE relies on an IP-based network for handling voice calls and data services simultaneously.

PCSCF is an important element in the IMS (IP Multimedia Subsystem) architecture for handling SIP signaling. In a typical scenario where mobile data is enabled, the UE can communicate with the network, and during the Attach procedure, the PCSCF address can be obtained through the network’s signaling.

However, when mobile data is disabled, the UE might not have access to the IP network to directly query the PCSCF. In this situation, the UE might struggle to obtain the PCSCF address for SIP registration. Some potential implications could include:

  1. Registration Failure: The UE might not be able to register on the IMS network, resulting in an inability to make VoLTE calls or access IMS-based services.
  2. Fallback to CSFB: If VoLTE is not available due to disabled mobile data, the UE might fall back to CSFB (Circuit-Switched FallBack), which routes voice calls over legacy circuit-switched networks, but this doesn’t involve IMS registration.
  3. Limited Services: Some services and features associated with IMS, such as HD voice, video calls, and enriched calling features, might not be available to the UE when it’s not registered on the IMS network.

It’s important to note that the exact behavior can depend on the specific network configuration, device capabilities, and operator policies. In scenarios where VoLTE and SIP are central, enabling mobile data when using a VoLTE-capable device is typically recommended to ensure proper network registration and the ability to access IMS-based services seamlessly.

Please consult your mobile carrier or network operator for detailed information about how their network handles these scenarios and any potential workarounds that may be available.

Is this ChatGPT ?

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Data (internet) is on one Bearer, VoLTE (IMS) is on another Bearer and MMS is on a third Bearer. These 3 bearers can connect/disconnect independently.

One Bearer does not need to be attached for any of the other Bearers to attach.

The term default bearer is often misunderstood. The default bearer is not the Data bearer. Data, IMS and MMS are all default bearers. Dedicated bearers can be conjured on-demand for media/video channels on the IMS IP/bearer.

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Well, you almost guessed it, only another bot that is a little more responsible for this specificity.

Why use a bot service to make posts in a forum ?

When users are asking questions in this forum, they expect answer from humans that can be held accountable for their information.

The bot-blurp you pasted in is basically elegant bullshit. At best it does not address the question asked - at worst it is misleading the original post into all kind of irrelevant places.

“Please consult your mobile carrier” … we are the mobile carriers !!!


Disabling data is an application-level operation. It doesn’t block lower layer attaching procedure, so IMS registration can go on.

Mobile data OFF is a setting on the device it doesn’t effect enabling the default bearer.

VoLTE registration flow is exactly same with mobile data ON and OFF.

Because of very small amaount of data usage (around 500 kilo bytes) even mobile data is OFF for some certain UEs.

Some operators provisions an APN with no data as a defalt bearer.

Data disable enable/disable is mechanism by which android control data switch between AP/CP (application and modem).

Even if data is disabled it only means that data will not flow to modem module in UE.

VoLTE stack can still send data to modem as it resides in modem part.

You can perform a simple test, disable data, still you can do MO / MT call.

So it means without having internet default bearer, IMS bearer can exists.

Default bearer will establish even without data enable.

Data enable/disable is switch between AP and CP.

Do simple test - disable data then airplane mode OFF/ON.

Disable airplane mode and make sure data is remain disabled. Make a VoLTE call.