Can anyone tell me what are the various Attach Request Type and Attach Accept response from Network

Question

Hi All,

I want to know, various types of Attach Request for Phone and Wifi devices and what will be the respective attach Accept response from the network in successful Case. I am looking for Network response both in case if network supports VoLTE (Like RJIO)and if network doesnot supports volte (Airtel)....

Answer 1

In LTE, spec TS 24.301 5.5.1, there are three types of attach request:
attach for EPS only (attach procedure),
attach for EPS and non-EPS (combined attach), or
attach for emergency.

"what will be the respective attach Accept response from the network in successful Case" you can see 24.301 5.5.1.2.4 and 8.2.1.1
You can download spec in here
https://portal.3gpp.org/desktopmodules/Specifications/SpecificationDetails.aspx?specificationId=1072

There is an IE in attach accept sent by network is called "EPS network feature support".
There is one bit called IMS VoPS in "EPS network feature support".
If IMS VoPS is set then network support IMS voice call.

Reference 24.301 8.2.1.1 and 9.9.3.12A

As for Wifi, i think it is impossible to use VoLTE because it is not through the CN of operator, but i am not sure. Maybe other people can help you.