EPC and 4G Packet Networks

Driving the Mobile Broadband Revolution

Magnus Olsson, Catherine Mulligan

• Publisher: Academic Press
• Year: 2012
• ISBN:
  9780123948298
• Edition: 2
• Topic: Technology & Engineering
• Subtopic: Electrical Engineering & Telecommunications
• Index: Technology & Engineering

Get a comprehensive and detailed insight into the Evolved Packet Core (EPC) with this clear, concise and authoritative guide – a fully updated second edition that covers the latest standards and industry developments. The latest additions to the Evolved Packet System (EPS) including e.g. Positioning, User Data Management, eMBMS, SRVCC, VoLTE, CSFB.A detailed description of the nuts and bolts of EPC that are required to really get services up and running on a variety of operator networks.An in-depth overview of the EPC architecture and its connections to the wide variety of network accesses, including LTE, LTE-Advanced, WCDMA/HSPA, GSM, WiFi, etc.The most common operator scenarios of EPS and the common issues faced in their design.The reasoning behind many of the design decisions taken in EPC, in order to understand the full details and background of the all-IP core

NEW CONTENT TO THIS EDITION

• 150+ New pages, new illustrations and call flows • Covers 3GPP Release 9, 10 and 11 in addition to release 8 • Expanded coverage on Diameter protocol, interface and messages • Architecture overview • Positioning • User Data Management • eMBMS (LTE Broadcasting) • H(e)NodeB/Femto Cells • LIPA/SIPTO/Breakout architectures • Deployment Scenarios • WiFi interworking • VoLTE/MMTel, CS fallback and SRVCC

• SAE is the core network that supports LTE, the next key stage in development of the UMTS network to provide mobile broadband. It aims to provide an efficient, cost-effective solution for the ever-increasing number of mobile broadband subscribers
• There is no other book on the market that covers the entire SAE network architecture; this book summarizes the important parts of the standards, but goes beyond mere description and offers real insight and explanation of the technology
• Fully updated with the latest developments since the first edition published, and now including additional material and insights on industry trends and views regarding future potential applications of SAE

Part I

Introduction – Background and Vision of EPC

Chapter 1 Mobile Broadband and the Core Network Evolution

Chapter 1

Mobile Broadband and the Core Network Evolution

The telecommunications industry is undoubtedly in a period of radical change with the advent of mobile broadband radio access and the rapid convergence of Internet and mobile services. Some of these changes have been enabled by a fundamental shift in the underlying technologies; mobile networks are now increasingly based on a pure Internet Protocol (IP) network architecture. Since the first edition of this book was published in 2009, a multitude of connected devices from eBook readers to smartphones and even Machine-to-Machine (M2M) technologies have all started to benefit from mobile broadband. The sea change over the last few years is only the beginning of a wave of new services that will fundamentally change our economy, our society, and even our environment. The evolution towards mobile broadband is one of the core underlying parts of this revolution and is the focus of this book.

The phenomenal success of GSM (Global System for Mobile Communications) was built on the foundation of circuit switching, providing voice services over cellular networks. Services, meanwhile, were built by developers specializing in telecommunication applications. During the early 1990s, usage of the Internet also took off, which in later years led to a demand for “mobile Internet”, Internet services that can be accessed from an end-user’s mobile device. The first mobile Internet services had limitations due to the processing capacity of terminals and also a very limited bandwidth on the radio interface. This has now changed as the evolution of radio access networks (RANs) provide high data rates delivered by High-Speed Packet Access (HSPA) and Long-Term Evolution (LTE) radio access technologies. The speed of this change is set to increase dramatically as a number of other developments emerge in addition to the new high-speed radio accesses: rapid advances in the processing capacity of semiconductors for mobile terminals and also in the software that developers can use to create services. IP and packet-switched technologies are soon expected to be the basis for data and voice services on both the Internet and mobile communications networks.

The core network is the part that links these worlds together, combining the power of high-speed radio access technologies with the power of the innovative application development enabled by the Internet. The evolution of the core network, or Evolved Packet Core (EPC), is a fundamental cornerstone of the mobile broadband revolution; without it, neither the RANs nor mobile Internet services would realize their full potential. The new core network was developed with high-bandwidth services in mind from the outset, combining the best of IP infrastructure and mobility. It is designed to truly enable mobile broadband services and applications and to ensure a smooth experience for both operators and end-users as it also connects multiple radio access technologies.

This chapter introduces the reasoning behind the evolution of the core network and a brief introduction to the technologies related to EPC. We also briefly touch on how EPS is beginning to change the industrial structure of the mobile industry.

System Architecture Evolution (SAE) was the name of the Third Generation Partnership Project (3GPP) standardization work item that was responsible for the evolution of the packet core network, more commonly referred to as EPC. This work item was closely related to the LTE work item, covering the evolution of the radio network. The Evolved Packet System (EPS) covers the radio access, the core network, and the terminals that comprise the overall mobile system. EPC also provides support for other high-speed access network technologies that are not based on 3GPP standards, for example WiFi, or fixed access. This book is all about Evolved Packet Core and Evolved Packet System – the evolution of the core network in order to support the mobile broadband vision and an evolution to IP-based core networks for all services.

The broad aims of the SAE work item were to evolve the packet core networks defined by 3GPP in order to create a simplified all-IP architecture, providing support for multiple radio accesses, including mobility between the different radio standards. So, what drove the requirement for evolving the core network and why did it need to be a globally agreed standard? This is where we start our discussion.

1.1 A Global Standard

There are many discussions today regarding the evolution of standards for the communications industries, in particular when it comes to convergence between IT and telecommunications services. A question that pops up occasionally is why is a global standard needed at all? Why does the cellular industry follow a rigorous standards process, rather than, say, the de-facto standardization process that the computer industry often uses? There is a lot of interest in the standardization process for work items like LTE and SAE, so there is obviously a commercial reason for this, or very few companies would see value in participating in the work.

The necessity for a global standard is driven by many factors, but there are two main points. First of all, the creation of a standard is important for interoperability in a truly global, multi-vendor operating environment. Operators wish to ensure that they are able to purchase network equipment from several vendors, ensuring competition. For this to be possible nodes and mobile devices from different vendors must work with one another; this is achieved by specifying a set of “interface descriptions”, through which the different nodes on a network are able to communicate with one another. A global standard therefore ensures that an operator can select whichever network equipment vendors they like and that end-users are able to select whichever handset they like; a handset from vendor A is able to connect to a base station from vendor B and vice versa. This ensures competition, which in itself attracts operators and drives deployments by ensuring a sound financial case through avoiding dependencies on specific vendors.

Secondly, the creation of a global standard reduces fragmentation in the market for all the actors involved in delivering network services to end-users: operators, chip manufacturers, equipment vendors, etc. A global standard ensures that there will be a certain market for the products that, for example, an equipment vendor develops. The larger the volume of production for a product, the greater the volume there is to spread the cost of design and production across the operators that will use the products. Essentially, with increased volumes a vendor should be able to produce each node at a cheaper per-unit cost. Vendors can then achieve profitability at lower price levels, which ultimately leads to a more cost-effective solution for both operators and end-users. Global standards are therefore a foundation stone of the ability to provide inexpensive, reliable communications networks, and the aims behind the development of EPC were no different.

There are several different standards bodies that have been directly involved in the standardization processes for the SAE work. These standards bodies include the 3GPP, the lead organization initiating the work, the Third Generation Partnership Project 2 (3GPP2), the Internet Engineering Task Force (IETF), Open Mobile Alliance (OMA), Broadband Forum (BBF), and also the WiFi Alliance. 3GPP “owns” the EPS specifications and refers to IETF and occasionally OMA specifications where necessary, while 3GPP2 complements these EPS specifications with their own documents that cover the impact on 3GPP2-based systems.

Readers who are not familiar with the standardization process are referred to Appendix 1, where we provide a brief description of the different bodies involved and the processes that are followed during the development of these specifications. We also provide a very brief history of the development of the SAE specifications.

1.2 Origins of the Evolved Packet Core

Over the years, many different radio standards have been created worldwide, the most commonly recognized ones being GSM, CDMA, and WCDMA/HSPA.

The GSM/WCDMA/HSPA and CDMA radio access technologies were defined in different standards bodies and also had different core networks associated with each one, as we describe below.

EPS is composed of the EPC, End-User Equipment (more commonly known as the UE), Access Networks (including 3GPP access such as GSM, WCDMA/HSPA and LTE as well as CDMA, etc.). The combination of these enables access to an operator’s services and also to the IMS, which provides voice and multimedia services.

In order to understand why evolution was needed for 3GPP’s existing packet core, we therefore also need to consider where and how the various existing core network technologies fit together in the currently deployed systems. The following sections present a discussion around why the evolution was necessary. While the number of acronyms may appear daunting in this section for anyone new to 3GPP standards, the rest of the book explains the technology in great detail. The following sections highlight only some of the main technical reasons for the evolution.

1.2.1 3GPP Radio Access Technologies

GSM was originally developed within the European Telecommunication Standards Institute (ETSI), which covered both the RAN and the core network supplying circuit-switched telephony. The main components of the core network for GSM were the Mobile Switching Centre (MSC) and the Home Location Register (HLR). The interface between the GSM BSC (Base Station Controller) and the MSC was referred to as the “A” interface. It is common practice for interfaces in 3GPP to be given a letter as a name; in later releases of the standards there are often two letters, for example “Gb” interface. Using letters is an easy shorthand method of referring to a particular functional connection between two nodes.

Over time, the need to support IP traffic was identified within the mobile industry and the General Packet Radio Services (GPRS) system was created as an add-on to the existing GSM system. With the development of GPRS, the concept of a packet-switched core network was needed within the specifications. The existing GSM radio network evolved, while two new logical network entities or nodes were introduced into the core network – SGSN (Serving GPRS Support Node) and GGSN (Gateway GPRS Support Node).

GPRS was developed during the period of time when PPP, X.25, and Frame Relay were state-of-the-art technologies (mid to late 1990s) for packet data transmission on data communications networks. This naturally had some influence on the standardization of certain interfaces, for example the Gb interface, which connects the BSC in the GSM radio network with the GPRS packet core.

During the move from GSM EDGE Radio Access Network (GERAN) to WCDMA/UMTS Terrestrial Radio Access Network (UTRAN), an industry initiative was launched to handle the standardization of radio and core network technologies in a global forum, rather than ETSI, which was solely for European standards. This initiative became known as the 3GPP and took the lead for the standardization of the core network for UTRAN/WCDMA, in addition to UTRAN radio access itself. 3GPP later also took the lead in the creation of the Common IMS specifications. IMS is short for IP Multimedia Subsystem, and targets network support for IP-based multimedia services. We discuss the IMS further in Chapter 11.

The core network for UTRAN reused much of the core network from GERAN, with a few updates. The main difference was the addition of the interface between the UTRAN Radio Network Controller (RNC), the MSC and the SGSN, the Iu-CS and the Iu-PS respectively. Both of these interfaces were based on the A interface, but the Iu-CS was for circuit-switched access, while the Iu-PS was for packet-switched connections. This represented a fundamental change in thinking for the interface between the mobile terminal and the core network. For GSM, the interface handling the circuit-switched calls and the interface handling the packet-switched access were very different. For UTRAN, it was decided to have one common way to access the core network, with only small differences for the circuit-switched and packet-switched connections. A high-level view of the architecture of this date, around 1999, is shown in Figure 1.1 (to be completely accurate, the Iu-CS interface was split into two parts, but we will disregard that for now in order not to make this description too complex).

Figure 1.1 High-level View of The 3GPP Mobile Network Architecture.

The packet core network for GSM/GPRS and WCDMA/HSPA forms the basis for the evolution towards EPC. As a result, it is worthwhile taking the time for a brief review of the technology. Again, do not be put off by the number of acronyms. Parts II and III provide more details.

The packet core architecture was designed around a tunneling protocol named GTP (GPRS Tunneling Protocol) developed within ETSI and then continued within 3GPP after its creation. GTP is a fundamental part of 3GPP packet core, running between the two core network entities, the SGSN and the GGSN. GTP runs over IP and provides mobility, Quality of Service (QoS), and policy control within the protocol itself. As GTP was created for use by the mobile community, it has inherent properties that make it suitable for robust and time-critical systems such as mobile networks. Since GTP is developed and maintained within 3GPP, it also readily facilitates the addition of the special requirements of a 3GPP network such as the use of the Protocol Configuration Option (PCO) field between the terminal and the core network. PCO carries special information between the terminal and the core ...

Table of contents

• Cover image
• Title page
• Table of Contents
• Copyright
• Foreword by Dr. Kalyani Bogineni
• Foreword by Dr. Ulf Nilsson
• Preface
• Acknowledgements
• List of Abbreviations
• Part I: Introduction – Background and Vision of EPC
• Part II: Overview of EPS
• Part III: Key Concepts and Services
• Part IV: The Nuts and Bolts of EPC
• Part V: Conclusion and Future of EPS
• Appendix A: Standards Bodies Associated with EPS
• References
• Index