How to make VoLTE device Part 3

Now lets see the involvement of different modules for VoLTE MO call.

Here it may be little difficult for people who have no knowledge of Modem, since we will be using modem as a module using which we will talk with Network.


This is learning for me also , as I am writing this post.


1) We need to register with Network or Server which will provide me with SIP packets for signalling and RTP packets for Voice .

[This is for me : Check in 3gpp which nodes perform these roles ]


A simple diagram will do no harm

So as you can our device has to establish two connection with network, one for signalling message and one for voice data. The voice data connection or RTP connection will be establish only for call and will be broken down once call is done, since afterwards there is no use of that .


IMS stack will send a command to Modem

 AT_IMSATTACH : This will trigger modem to establish default bearer for IMS.

( IMS is the module or stack which make volte call possible) It is present on both device and network side.

Now when this bearer is establish , QoS parameter are important .

[ I have to check for default bearer Qos and other information shared by Network]

Network will provide an IP addres to us , over which IP packets will be sent and receive.


2) Once IP address is obtained , modem sends to IMS stack  indication of default bearer up and IP address obtained.

AT_IMS_RESULT
AT_IMS_IP


I will be stopping here , since I want to have AT cmd shown as structure , maybe I will go with Java and create classes to show them
Also I need to check about socket , because that will put things beautifully, since all of this is packet switch .

There is good link , more for my use

https://docs.oracle.com/javase/tutorial/networking/sockets/readingWriting.html