forms the processing of the telephone signal to provide VoLTE and ViLTE services, including call routing and the provision of additional services. Different procedures are described: the set-up and termination of a session, interconnection with third-party networks, roaming and intra-system handover. The inter-system handover PS-CS is a special case that occurs when the mobile loses 4G network coverage over the course of a session. The e-SRVCC mechanism enables continuity of the service during the switch of the telephone communication to the 2G or 3G networks. The SMS service for short messages, which is a special telephone service in itself, is provided by two structures, one relying on the IMS network, and a second on the CSFB functionality. 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 SYSTEMS. WILEY www.iste.co.uk 91781848219236 NETWORKS AND TELECOMMUNICATIONS SERIES Wi-Fi Integration to the 4G Mobile Network André Perez WILEY Wi-Fi Integration to the 4G Mobile Network Wi-Fi Integration to the 4G Mobile Network André Perez WILEY First published 2018 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 John Wiley & Sons, Inc. 27-37 St George's Road 111 River Street London SW19 4EU Hoboken, NJ 07030 www.iste.co.uk www.wiley.com © ISTE Ltd 2018 The rights of André Perez to be identified as the a