telecom • networking • design

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Voice Over LTE (VoLTE) Originating Call

Voice over LTE (VoLTE) is the standard for voice call setup in LTE networks. When VoLTE is deployed, phones will not need to fallback to 3G for voice calls.

VoLTE uses IMS SIP signaling to set up voice calls. The following VoLTE call flow describes the IMS call setup and release. An example of sending an SMS over IMS is also included. Sample RTP and RTCP messages are also shown in the flow.
Voice over LTE Call Flow


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The Anatomy of an INVITE Request

SIP Adventures

As a high school student, I loved biology. I loved learning about the natural world and how our bodies function. The spleen was my friend — not to mention the pancreas, liver, and lungs.

Unlike many of my classmates, I didn’t mind dissecting frogs and the obligatory fetal pig. Okay, I wasn’t overly fond of the smell of formaldehyde, but it was mesmerizing cutting into the skin and exploring what lurked below.

I look upon SIP in a very similar fashion except instead of using a knife, my dissection tool of choice is Wireshark. Followers of this blog should already know that from reading my article, How to Debug SIP.   Wireshark is powerful software that not only captures SIP packets, but displays them in a very readable manner. On top of that, you can also capture and replay audio streams. If you want to call yourself a SIP professional…

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