January 2021
Intermediate to advanced
624 pages
23h 5m
English
Content preview from From GSM to LTE-Advanced Pro and 5G, 4th Edition
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.
5VoLTE, VoWifi, and Mission Critical Communication
5.1 Overview
In the chapter on GSM the structure of the GSM network was described in combination with voice telephony. It is difficult to separate the GSM voice service from the GSM network as the (voice) service and the network are completely integrated. Even in UMTS, this is still the case to a significant degree. For LTE, however, 3GPP decided with only a few exceptions, to completely separate the network from any kind of higher‐layer service, including voice telephony. This is the reason the description of LTE in the previous chapter could be done without mentioning an integrated voice telephony solution.
Voice telephony, however, is still an important service, and the CS‐Fallback solution described in the chapter on LTE and LTE‐Advanced Pro was only meant to be a temporary solution on the path to an all‐IP network in which all services including voice telephony are based on the Internet protocol. After many years, this has finally been accomplished with the VoLTE (Voice over LTE) IP Multimedia Subsystem (IMS) profile standardized in GSMA IR.92 [1], which is based on the Session Initiation Protocol (SIP).
In practice, it can be currently observed that LTE networks have not yet reached the same level of geographic coverage as GSM networks and it is likely to remain that way for some time to come. Therefore, a fallback for an ongoing voice call to a classic circuit‐switched channel is still required. This functionality is ...
Become an O’Reilly member and get unlimited access to this title plus top books and audiobooks from O’Reilly and nearly 200 top publishers, thousands of courses curated by job role, 150+ live events each month,
and much more.
Read now
Unlock full access
More than 5,000 organizations count on O’Reilly
O’Reilly covers everything we've got, with content to help us build a world-class technology community, upgrade the capabilities and competencies of our teams, and improve overall team performance as well as their engagement.Julian F.
I wanted to learn C and C++, but it didn't click for me until I picked up an O'Reilly book. When I went on the O’Reilly platform, I was astonished to find all the books there, plus live events and sandboxes so you could play around with the technology.Addison B.
I’ve been on the O’Reilly platform for more than eight years. I use a couple of learning platforms, but I'm on O'Reilly more than anybody else. When you're there, you start learning. I'm never disappointed.Amir M.
I'm always learning. So when I got on to O'Reilly, I was like a kid in a candy store. There are playlists. There are answers. There's on-demand training. It's worth its weight in gold, in terms of what it allows me to do.