Ingeniero Electrónico

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The LTE Network Architecture
A comprehensive tutorial
Long Term Evolution (LTE) is the latest buzzword on everyone’s lips, but are you as conversant with the LTE architecture as you would like to be, or — more importantly — need to be? Would you like to find out more about LTE, but have little time to devote to it? If so, this paper will help getyou up to speed in no time. Originally published as a chapter in the most comprehensive LTE reference book available, LTE — The UMTS Long Term Evolution: From Theory to Practice (Wiley 2009), this paper provides a short, but comprehensive, overview of the 3GPP Release 8 LTE network architecture and interfaces, showing how it can be deployed in an optimized and efficient manner. Engineers involvedin the design of LTE interfaces and network equipment, as well as those involved in the first deployments of this new technology, should find this paper invaluable.

Table of contents
1 1 1 3 5 6 6 7 7 8 8 11 12 12 13 14 14 14 15 16 17 17 17 18 21 22 22 22 23 23 1. Executive summary 2. Introduction 3. Overall architectural overview 3.1 The core network 3.2 The access network 3.3Roaming architecture 3.4 Interworking with other networks 4. Protocol architecture 4.1 User plane 4.2 Control plane 5. Quality of service and EPS bearers 5.1 Bearer establishment procedure 6. The E-UTRAN network interfaces: S1 interface 6.1 Protocol structure over S1 6.2 Initiation over S1 6.3 Context management over S1 6.4 Bearer management over S1 6.5 Paging over S1 6.6 Mobility over S1 6.7 Loadmanagement over S1 7. The E-UTRAN network interfaces: X2 interface 7.1 Protocol structure over X2 7.2 Initiation over X2 7.3 Mobility over X2 7.4 Load and interference management over X2 7.5 UE historical information over X2 8. Summary 9. Abbreviations 10. Contacts 11. References

1. Executive summary
This paper provides a comprehensive overview of the network architecture of a Long TermEvolution (LTE) system according to the Release 8 version of the specifications. It is designed to enable the reader to become conversant rapidly with the main principles of the LTE network architecture. Engineers involved in the design of LTE interfaces and network equipment, as well as those involved in the first deployments of this new technology, should find this paper invaluable. Not only does thispaper provide a straightforward introduction to the definitive but complex specifications defined by the Third-Generation Partnership Project (3GPP), but it also particularly highlights aspects of the network architecture and interfaces that enable LTE networks to be deployed in an optimized and efficient manner. References are provided throughout so that the interested reader can readily accessmore detailed material. The content of this paper, authored by Sudeep Palat and Philippe Godin, was originally published as an invited chapter in the book LTE — The UMTS Long Term Evolution: From Theory to Practice (Wiley 2009), edited by Stefania Sesia, Issam Toufik and Matthew Baker, which is widely recognized as the most comprehensive reference book available on LTE. Sudeep Palat, Philippe Godinand Matthew Baker are all lead representatives in Alcatel-Lucent’s 3GPP standardization team.

2. Introduction
In contrast to the circuit-switched model of previous cellular systems, Long Term Evolution (LTE) has been designed to support only packet-switched services. It aims to provide seamless Internet Protocol (IP) connectivity between user equipment (UE) and the packet data network (PDN),without any disruption to the end users’ applications during mobility. While the term “LTE” encompasses the evolution of the Universal Mobile Telecommunications System (UMTS) radio access through the Evolved UTRAN (E-UTRAN), it is accompanied by an evolution of the non-radio aspects under the term “System Architecture Evolution” (SAE), which includes the Evolved Packet Core (EPC) network....