Voice over LTE E-Book

Andre Perez

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 235

Veröffentlichungsjahr: 2013

Beschreibung

Voice over LTE (Long Term Evolution) presents the mechanisms put in place in 4G mobile networks for the transportation of IP packets containing voice data and telephone signaling, as well as the technologies used to provide a telephone service in the IMS (IP Multimedia Sub-system) network. Despite the difficulty connected to the handover of the 4G network to the 2G/3G network, a telephone communication will not be established on the 4G network. This book analyzes the technologies that have been put in place, such as CSFB (Circuit Service FallBack), an interim solution that enables a mobile connected to the 4G network to receive an alert transmitted by the 2G/3G network. The book also goes on to develop the SIP (Session Information Protocol) on which the telephone signaling transferred by the 4G network is based, the IMS network that provides the service and defines the routing, the SRVCC (Single Radio Voice Call Continuity) mechanism that maintains communication and the TAS (Telephony Application Server) that supplies supplementary services. Contents 1. The EPS Network. 2. The LTE Interface. 3. The CSFB Function. 4. SIP and SDP Protocols. 5. The IMS Network. 6. Telephone Services. 7. The SRVCC Function. About the Authors André Perez is a consultant and teacher in networks and telecommunications. He works with industrialists and operators regarding architecture studies and leads training on the 4G and IMS networks for NEXCOM.

Leseprobe

Table of Contents

Preface

Acronyms

Chapter 1 The EPS Network

1.1. Architecture

1.2. Signaling protocols

1.3. Procedures

Chapter 2 The LTE Interface

2.1. Structure of the radioelectric interface

2.2. Data link layer

2.3. Physical layer

2.4. Procedures

Chapter 3 The CSFB Function

3.1. Reminder about NGN

3.2. The CSFB function

3.3. Procedures

Chapter 4 SIP and SDP Protocols

4.1. Entities

4.2. Identities

4.3. Structure of SIP

4.4. Description of the media

4.5. Procedures

Chapter 5 The IMS Network

5.1. Architecture of IMS

5.2. Registration

5.3. The session between IMSs

5.4. DIAMETER messages

5.5. Interoperation with the CS network

Chapter 6 Telephone Services

6.1. Service profile

6.2. Communication Diversion

6.3. Identification presentation

6.4. Message Waiting Indication

6.5. Call parking

6.6. Conferencing

6.7. Communication transfer

6.8. Communication Waiting

6.9. Malicious Communication Identification

6.10. Automatic callback

6.11. Communication rejection

6.12. Announcements

Chapter 7 The SRVCC Function

7.1. Impact on architectures

7.2. Procedures

Bibliography

Index

First published 2013 in Great Britain and the United States by ISTE Ltd and John Wiley & Sons, Inc.

Apart from any fair dealing for the purposes of research or private study, or criticism or review, as permitted under the Copyright, Designs and Patents Act 1988, this publication may only be reproduced, stored or transmitted, in any form or by any means, with the prior permission in writing of the publishers, or in the case of reprographic reproduction in accordance with the terms and licenses issued by the CLA. Enquiries concerning reproduction outside these terms should be sent to the publishers at the undermentioned address:

ISTE Ltd

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London SW19 4EU

UK

www.iste.co.uk

John Wiley & Sons, Inc.

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Hoboken, NJ 07030

USA

www.wiley.com

©ISTE Ltd 2013

The rights of André Perez to be identified as the author of this work have been asserted by him in accordance with the Copyright, Designs and Patents Act 1988.

Library of Congress Control Number: 2013942893

British Library Cataloguing-in-Publication Data A CIP record for this book is available from the British Library

ISBN: 978-1-84821-534-4

Preface

This book discusses the mechanisms used in the 4G EPS (Evolved Packet System) mobile network for telephone service support, and in the IMS network (IP (Internet Protocol) Multimedia Sub-system) to provide a telephone service.

The 4G network does not provide a telephone service because it does not process telephone signaling. It operates in PS (Packet Service) mode, and only transports IP packets. Therefore, it only transfers IP packets containing voice data or telephone signaling.

The IP packet containing voice data has the following structure:

– AMR (Adaptative Multi-Rate) codec;

– RTP (Real-Time Transport Protocol) header;

– UDP (User Datagram Protocol) header;

– IP header.

The IP packet containing telephone signaling has the following structure:

– SIP (Session Information Protocol) message;

– UDP header;

– IP header.

Chapter 1 introduces the different entities of the 4G network. It describes the 4G signaling protocol exchanged between the different entities, enabling a mobile to attach, update its location, establish sessions for the transport of IP packets and change cells (known as handover). For the purposes of the transport of IP packets, the 4G network has supports in place that are known as bearers. A bearer is similar to a virtual circuit.

Chapter 2 presents the LTE (Long Term Evolution) radioelectric interface between the mobile and the 4G networks. The radioelectric interface serves to transport the mobile traffic (IP packets containing voice data or telephone signaling) and the 4G signaling exchanged with the 4G network.

The procedures specific to the radioelectric interface relate to connection of the mobile to the 4G network, scheduling of the IP packets and re-transmission in the case of error.

To begin with, the establishment of a telephone communication will not be done over a 4G network, because of the difficulty in handover from PS mode to CS (Circuit Service) mode, when the mobile is transferred from a 4G cell to a 2G or 3G cell.

Chapter 3 discusses the mechanism of CSFB (CS FallBack), which is an interim solution. It enables a mobile connected to the 4G network to receive an alert sent by a 2G/3G network (this is known as paging). This page is sent when a call comes in on the 2G/3G network. On receiving the page, the mobile is transferred to the 2G/3G network, over which the telephone communication can then be established.

Similarly, a mobile connected to the 4G network and wishing to make an outgoing call must first be transferred to the 2G/3G network.

Chapter 4 presents the SIP protocol, upon which the telephone signaling transferred by the 4G network is based. SIP defines two fundamental procedures: registration of the mobile and establishment of the session (i.e. the telephone communication).

Chapter 5 introduces the IMS network which provides a telephone service, using the 4G network for the transport of the voice data and telephone signaling. The telephone signaling again uses SIP, enriching it.

The IMS network defines the routing of the telephone signaling, access to databases containing the profile and secret data of the subscriber, and the specific processing of voice data to provide particular services, such as conference calling, for instance.

Telephone communication can be established between two 4G mobiles. The telephone signaling is processed by the IMS entities of the home operator of each mobile. The voice data is directly transferred between the 4G networks (see Figure 1).

Figure 1.Telephone communication between two 4G mobiles

Telephone communication can also be established between a mobile and a terminal connected to the fixed network PSTN (Public Switched Telephone Network) or the mobile network PLMN (Public Land Mobile Network). The IMS network provides the entities which perform conversion of the protocols and interconnection with these networks (Figure 2).

Figure 2.Telephone communication between a 4G mobile and a terminal connected to the PLMN or PSTN network

Chapter 6 presents the telephone services offered by a particular entity within the IMS network – the TAS (Telephone Application Server). These services relate to communication forwarding, identification presentation or restriction, message waiting indication, communication hold, conference, communication transfer, call waiting, malicious communication identification, completion of communication, call rejection and announcements.

The telephone communication established over the 4G network in PS mode needs to be maintained when the mobile is transferred to the 2G/3G network in CS mode.

Chapter 7 finally discusses the mechanism of SRVCC (Single Radio Voice Call Continuity), which takes care of this call maintaining in the case of a PS-CS inter- system handover. SRVCC is a particular function of the IMS network. It anchors the flows of telephone signaling and voice data (Figure 3).

Figure 3.The SRVCC mechanism

Acronyms

A

AAA

Authorization-Authentication-Answer

AAL2

ATM Adaptation Layer 2

AAR

Authorization-Authentication-Request

ACM

Address Complete Message

ACR

Anonymous Communication Rejection

AM

Acknowledged Mode

AMR

Adaptive Multi-Rate

ANM

Answer Message

APN

Access Point Name

ARQ

Automatic Repeat reQuest

AS

Application Server

ASA

Abort-Session-Answer

ASR

Abort-Session-Request

ATCF

Access Transfer Control Function

ATGW

Access Transfer Gateway

ATM

Asynchronous Transfer Mode

B

B2BUA

Back-to-Back User Agent

B2BUA

Broadcast Control Channel

BCH

Broadcast Channel

BGCF

Breakout Gateway Control Function

BICC

Bearer Independent Call Control

BICC

Base Station Sub-system

BSSMAP

BSS Management Application Part

C

CCBS

Completion of Communications to Busy Subscriber

CCCH

Common Control Channel

CCNL

Completion of Communications on Not Logged-in

CCNR

Completion of Communications on No Reply

CD

Communication Deflection

CDF

Charging Data Function

CDIV

Communication Diversion

CDR

Charging Data Record

CFB

Communication Forwarding on Busy user

CFI

Control Format Indicator

CFNL

Communication Forwarding on Not Logged-in

CFNR

Communication Forwarding on No Reply

CFU

Communication Forwarding Unconditional

CGF

Charging Gateway Function

CM

Call Management

CQI

Channel Quality Indicator

C-RNTI

Cell Radio Network Temporary Identity

CS

Circuit Service

CSCF

Call Session Control Function

CSFB

Circuit Service FallBack

CTF

Charging Trigger Function

CW

Communication Waiting

D

DCCH

Dedicated Control Channel

DCI

Downlink Control Information

DFTS

Discrete Fourier Transform Spread

DL-SCH

Downlink Shared Channel

DNS

Domain Name System

DRB

Data Radio Bearer

DRS

Demodulation Reference Signal

DSCP

DiffServ Code Point

DTCH

Dedicated Traffic Channel

DTM

Dual Transfer Mode

DwPTS