129454451 Lelliwa LTE Technology

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Table of Contents

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LTE/LTE/LTE/LTE/EEEEPSPSPSPSTechnologyTechnologyTechnologyTechnology

Book revision 4.0.2

TableofContentsTableofContentsTableofContentsTableofContentsChapterChapterChapterChapter PagePagePagePage

1. Introduction ....... 5

2. Architecture .. 27

3. OFDMA & SC-FDMA ..... 49

4. E-UTRAN ..... 95

5. Core Network .... 133

6. Policy control & charging ..... 167

7. Traffic cases .. 177

8. Security . 213

9. EPS Management .. 237

10. Services ..... 249

11. CS Fallback and SMSoSGs .. 297

12. Acronyms & abbreviations ....... 313


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ChapterChapterChapterChapter1111

IntroductionIntroductionIntroductionIntroduction

TopicTopicTopicTopic PagePagePagePage

Introduction........................................................................................................7

HSPA + ............................................................................................................12

LTE / E-UTRAN.............................................................................................. 17

EPS / SAE........................................................................................................24

IMS ..................................................................................................................25


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IntroductionIntroductionIntroductionIntroductionThis chapter discusses the evolution and migration of wireless-data

technologies from EDGE to LTE as well as the evolution of underlying

wireless approaches. Progress happens in multiple phases, first with EDGE,

and then UMTS, followed by evolved 3G capabilities such as HSDPA,

HSUPA, HSPA+, and eventually LTE. Meanwhile, underlying approaches

have evolved from TDMA to CDMA, and now from CDMA to Orthogonal

Frequency Division Multiple Access (OFDMA), which is the basis of Long

Term Evolution (LTE).

TDMA,CDMAandOFDMATDMA,CDMAandOFDMATDMA,CDMAandOFDMATDMA,CDMAandOFDMA

Many times, one technology or the other is positioned as having fundamental

advantages over another. However, any of these three approaches, when fully

optimized, can effectively match the capabilities of any other. For example,

GSM, which is based on TDMA, thanks to innovations like synchronized

frequency hopping, AMR, and EDGE for data performance optimisation,

GSM is able to effectively compete with the capacity and data throughput of

CDMA based systems.

Today, the main question is whether OFDM provide any inherent advantage

over TDMA or CDMA. For systems employing less than 10 MHz of

bandwidth, the answer no. Because it transmits mutually orthogonal

subchannels at a lower symbol rate, the fundamental advantage of OFDM is

that it elegantly addresses the problem of Inter Symbol Interference (ISI)

induced by multipath and greatly simplifies channel equalization. As such,

OFDM systems, assuming they employ all the other standard techniques for

maximizing spectral efficiency, may achieve slightly higher spectral

efficiency than CDMA systems. However, advanced receiver architectures,including options such as practical equalization approaches and interference

cancellation techniques, are already commercially available in chipsets and

can nearly match this performance advantage. It is with larger bandwidths (10

to 20 MHz), and in combination with advanced antenna approaches such as

Multiple Input Multiple Output (MIMO) or Adaptive Antenna Systems

(AAS), that OFDM enables less computationally complex implementations

than those based on CDMA.

Hence, OFDM is more readily realizable in mobile devices. However, studies

have shown that the complexity advantage of OFDM may be quite small (that

is, less than a factor of two) if frequency domain equalizers are used for


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CDMA-based technologies. Still, the advantage of reducing complexity is one

reason 3GPP chose OFDM for its LTE project. It is also one reason newer

WLAN standards, which employ 20 MHz radio channels, are based on

OFDM. In other words, OFDM is currently a favoured approach underconsideration for radio systems that have extremely high peak rates. OFDM

also has an advantage in that it can scale easily for different amounts of

available bandwidth. This in turn allows OFDM to be progressively deployed

in available spectrum by using different numbers of subcarriers.

An OFDMA technology such as LTE can also take better advantage of wider

radio channels (for example, 10 MHz) by not requiring guard bands between

radio carriers (for example, HSPA carriers). In recent years, the ability of

OFDM to cope with multipath has also made it the technology of choice for

the design of Digital Broadcast Systems (DBS).

In 5 MHz of spectrum, as used by UMTS/HSPA, continual advances with

CDMA technology (realized in HSPA+) through approaches such as

equalization, MIMO, interference cancellation, and high-order modulation

will allow CDMA to largely match OFDMA-based systems.

Because OFDMA has only modest advantages over CDMA in 5 MHz

channels, the advancement of HSPA is a logical and effective strategy. In

particular, it extends the life of operators large 3G investments, reducing

overall infrastructure investments, decreasing capital and operational

expenditures, and allowing operators to offer competitive services.

3GPPevolutionaryapproach3GPPevolutionaryapproach3GPPevolutionaryapproach3GPPevolutionaryapproach

Rather than emphasizing any one wireless approach, 3GPPs evolutionary

plan is to recognize the strengths and weaknesses of every technology and to

exploit the unique capabilities of each one accordingly. GSM, based on a

TDMA approach, is mature and broadly deployed. Already extremely

efficient, there are nevertheless opportunities for additional optimizations and

enhancements.

Standards bodies have already defined evolved EDGE, that doubles the

performance of current EDGE systems.

The evolved data systems for UMTS, such as HSPA and HSPA+, introduce

enhancements and simplifications that help CDMA based systems match the

capabilities of competing systems, especially in 5 MHz spectrum allocations.

Given some of the advantages of an OFDM approach, 3GPP has specified

OFDMA as the basis of its LTE effort. LTE incorporates best-of-breed radio

techniques to achieve performance levels beyond what will be practical with

CDMA approaches, particularly in larger channel bandwidths. However, in

the same way that 3G coexists with 2G systems in integrated networks, LTE


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systems will coexist with both 3G systems and 2G systems. Multimode

devices will function across LTE/3G or even LTE/3G/2G, depending on

market circumstances.

2006 2007 2008 2009 2010 2011

3GPP GSM EDGE Radio Access Network Evolution

3GPP UMTS Radio Access Network Evolution

EDGE

DL: 474 kbps

UL: 474 kbps

Evolved EDGE

DL: 1.9 Mbps

UL: 947 kbps

HSDPA

DL: 14.4 Mbps

UL: 384 kbps

In 5 Mhz

HSDPA/HSUPA

DL: 14.4 Mbps

UL: 5.76 Mbps

In 5 Mhz

Rel 7 HSPA+

DL: 28 Mbps

UL: 11.5 Mbps

In 5 Mhz

Rel8 HSPA+

DL: 42 Mbps

UL: 11.5 Mbps

In 5 Mhz

3GPP Long Term Evolution

LTE 2X2 MIMO

DL: 173 MbpsUL: 58 Mbps

In 20 Mhz

LTE 4X4 MIMO

DL: 326 MbpsUL: 86 Mbps

In 20 Mhz

EV-DO Rev 0DL: 2.4 MbpsUL: 153 kbps

In 1.25 Mhz

EV-DO Rev ADL: 3.1 MbpsUL: 1.8 Mbps

In 1.25 Mhz

EV-DO Rev BDL: 14.7 MbpsUL: 4.9 Mbps

In 5 Mhz

UMB 2X2 MIMODL: 140 MbpsUL: 34 Mbps

In 20 Mhz

CDMA 2000 Evolution

UMB 4X4 MIMODL: 280 MbpsUL: 68 Mbps

In 20 Mhz

Fixed WiMAX

Wave 1DL: 23 Mbps

UL: 4 Mbps

10 Mhz3:1 TDD

Wave 2DL: 46 Mbps

UL: 4 Mbps

10 Mhz3:1 TDD

Mobile WiMAX Evolution

IEEE 802.16m

Figure 1-1 Different wireless technologies and their evolution

The development of GSM and UMTS/HSPA happens in stages referred to as

3GPP releases, and equipment vendors produce hardware that supports

particular versions of each specification. It is important to realize that the

3GPP releases address multiple technologies. For example, R7 optimizes

VoIP for HSPA but also significantly enhances GSM data functionality with

Evolved EDGE. A summary of the different 3GPP releases follows:

Release 99 ( completed) - First deployable version of UMTS.

Enhancements to GSM data (EDGE). Provides support for

GSM/GPRS/EDGE/WCDMA radio-access networks.

Release 4 (completed). Multimedia messaging support. First steps

toward using IP transport in the CN.

Release 5 (completed): HSDPA. First phase of IMS. Full ability to useIP-based transport instead of just ATM in the CN.

Release 6 (completed): HSUPA. Enhanced multimedia support

through Multimedia Broadcast/Multicast Services (MBMS).

Performance specifications for advanced receivers. WLAN integration

option. IMS enhancements. Initial VoIP capability.

Release 7 (completed): Provides enhanced GSM data functionality

with Evolved EDGE. Specifies HSPA Evolution (HSPA+), which

includes higher order modulation and MIMO. Also includes fine-

tuning and incremental improvements of features from previous


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releases. Results include performance enhancements, improved

spectral efficiency, increased capacity, and better resistance to

interference. Continuous Packet Connectivity (CPC) enables efficient

always-on service and enhanced uplink VoIP capacity as well asreductions in call setup delay for PoC. Radio enhancements include 64

QAM in the downlink DL and 16 QAM in the uplinks.

Release 8 (under development): Further HSPA Evolution features

such as simultaneous use of MIMO and 64 QAM. Specifies OFDMA-

based 3GPP LTE. Defines Evolved Packet System (EPS), previously

called System Architecture Evolution (SAE).

CoreCoreCoreCore----NetworkEvolutionNetworkEvolutionNetworkEvolutionNetworkEvolution

3GPP is defining a series of enhancements to the CN to improve network

performance and the range of services provided and to enable a shift to all-IP

architectures. One way to improve CN performance is by using flatter

architectures. The more hierarchical a network, the more easily it can be

managed centrally; however, the trade-off is reduced performance, especially

for data communications, because packets must traverse and be processed by

multiple nodes in the network. To improve data performance and, in

particular, to reduce latency, 3GPP has defined a number of enhancements in

R7 and R8 that reduce the number of processing nodes and result in a flatter

architecture.

In R7, an option called one-tunnel architecture allows operators to configure

their networks so that user data bypasses a serving node and travels directly

via a gateway node. There is also an option to integrate the functionality of

the RNC controller directly into the NodeB.

For R8, 3GPP has defined an entirely new CN, called the Evolved Packet

System (EPS), earlier known under different name System Architecture

Evolution (SAE).

The key features and capabilities of EPS include:

reduced latency and higher data performance through a flatter

architecture,

support for both LTE radio access networks and interworking with

GERAN/UTRAN,

the ability to integrate non-3GPP networks such as WiMAX,

optimization for all services provided via IP,


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ServiceEvolutionServiceEvolutionServiceEvolutionServiceEvolution

Not only do 3GPP technologies provide continual improvements in capacity

and data performance, they also evolve capabilities that expand the services

available to subscribers. Key service advances include Fixed-Mobile

Convergence (FMC), IMS, and broadcasting technologies. This section

provides an overview of these topics, and the appendix provides greater detail

on each of these items.

FMC refers to the integration of fixed services (such as telephony provided by

wire line or WiFi) with mobile cellular-based services. Though FMC is still in

its early stages of deployment by operators, it promises to provide significant

benefits to both users and operators. For users, FMC will simplify how they

communicate, making it possible for them to use one device (for example, a

cell phone) at work and at home, where it might

connect via a WiFi network or a femtocell. When mobile, users connect via a

cellular network. Users will also benefit from single voice mailboxes and

single phone numbers as well as the ability to control how and with whom

they communicate. For operators, FMC allows the consolidation of core

services across multiple-access networks. For instance, an operator could

offer complete VoIP-based voice service that supports access

via DSL, WiFi, or 3G. FMC has various approaches, including enabling

technologies such as Unlicensed Mobile Access (UMA), femtocells, and IMS.

With 3GGP UMA, GSM/UMTS devices can connect via WiFi or cellularconnections for both voice and data.

An alternative to using WiFi for the fixed portion of FMC is femtocells.

These are tiny base stations that cost little more than a WiFi access point and,

like WiFi, femtocells leverage a subscriber's existing wire line broadband

connection (for example, DSL). Instead of operating on unlicensed bands,

femtocells use the operators licensed bands at very low power levels. The

key advantage of the femtocell approach is that any single mode mobile

communications device a user has can now operate using the femtocell.

IMS is another key technology for convergence. It allows access to coreservices and applications via multiple-access networks. IMS is more powerful

than UMA, because it supports not only FMC but also a much broader range

of potential applications. Though defined by 3GPP, both 3GPP2 and WiMAX

have adopted IMS. IMS allows the creative blending of different types of

communications and information, including voice, video, IM, presence

information, location, and documents. It provides application developers the

ability to create applications that have never before been possible, and it

allows people to communicate in entirely new ways by dynamically using

multiple services. For example, during an interactive chat session, a user

could launch a voice call. Or during a voice call, a user could suddenly


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establish a simultaneous video connection or start transferring files. While

browsing the Web, a user could decide to speak to a customer-service

representative. IMS will be a key platform for all-IP architectures for both

HSPA and LTE.Another important new service is support for mobile TV through what is

called multicast or broadcast functions. 3GPP has defined multicast/broadcast

capabilities for both HSPA and LTE.

HSPA+HSPA+HSPA+HSPA+

OFDMA systems have attracted considerable attention through technologies

such as 3GPP LTE and WiMAX. However, as already discussed earlier,

CDMA approaches can match OFDMA approaches in reduced channel

bandwidths. The goal in evolving HSPA is to exploit available radio

technologies, enabled by increases in digital signal processing power, to

maximize CDMA-based radio performance. This not only makes HSPA

competitive, it significantly extends the life of sizeable operator infrastructure

investments.

Wireless and networking technologists have defined a series of enhancements

for HSPA, some of which are specified in R7 and some of which are beingstudied for R8.

HSPA+ features:

Advanced receivers (type 1, 2, 3, 3i)

MIMO (2x2)

Continuous Packet Connectivity (CPC)

Higher order modulation (64QAM DL, 16QAM UL)Flatter architecture

Integrated RNC/Node B

Robust Header Compression (ROHC)

Figure 1-2 HSPA+ features


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AdvancedreceiversAdvancedreceiversAdvancedreceiversAdvancedreceivers

One important area is advanced receivers, where 3GPP has specified a

number of advanced designs. These designs include Type 1, which uses

mobile Rx diversity; Type 2, which uses channel equalization; and Type 3,

which includes a combination of Rx diversity and channel equalization. Type

3i devices will employ interference cancellation. Note that the different types

of receivers are release-independent. For example, Type 3i receivers will

work and provide a capacity gain in a R5 network.

The first approach is mobile Rx diversity. This technique relies on the optimal

combination of received signals from separate receiving antennas. The

antenna spacing yields signals that have somewhat independent fading

characteristics. Hence, the combined signal can be more effectively decoded,

which results in an almost doubling of downlink capacity when employed inconjunction with techniques such as channel equalization. Receive diversity is

effective even for small devices such as PC card modems and smartphones.

Current receiver architectures based on rake receivers are effective for speeds

up to a few megabits per second. But at higher speeds, the combination of

reduced symbol period and multipath interference results in inter-symbol

interference and diminishes rake receiver performance. This problem can be

solved by advanced receiver architectures with channel equalizers that yield

additional capacity gains over HSDPA with receive diversity. Alternate

advanced receiver approaches include interference cancellation andgeneralized rake receivers (G-Rake). Different vendors are emphasizing

different approaches. However, the performance requirements for advanced-

receiver architectures are specified in 3GPP R6. The combination of mobile

Rx diversity and channel equalization (Type 3) is especially attractive,

because it results in a large capacity gain independent of the radio channel.

What makes such enhancements attractive is that the networks do not require

any changes other than increased capacity within the infrastructure to support

the higher bandwidth. Moreover, the network can support a combination of

devices, including both earlier devices that do not include these enhancements

and later devices that do. Device vendors can selectively apply these

enhancements to their higher performing devices.

MIMOMIMOMIMOMIMO

Another standardized capability is Multiple Input Multiple Output (MIMO), a

technique that employs multiple transmit antennas and multiple receive

antennas, often in combination with multiple radios and multiple parallel data

streams. The most common use of the term MIMO applies to spatial

multiplexing. The transmitter sends different data streams over each antenna.


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Whereas multipath is an impediment for other radio systems, MIMO actually

exploits multipath, relying on signals to travel across different

communications paths. This results in multiple data paths effectively

operating somewhat in parallel and, through appropriate decoding, in amultiplicative gain in throughput.

UENode B

Figure 1-3 MIMO (2x2)

Tests of MIMO have proven very promising in WLANs operating in relative

isolation, where interference is not a dominant factor. Spatial multiplexing

MIMO should also benefit HSPA hotspots serving local areas such as

airports, campuses, and malls, where the technology will increase capacity

and peak data rates. However, in a fully loaded network with interference

from adjacent cells, overall capacity gains will be more modest - in the range

of 20 to 33 percent over mobile Rx diversity. Relative to a 1x1 antenna

system, however, 2x2 MIMO can deliver cell throughput gains of about 80

percent. 3GPP has standardized spatial multiplexing MIMO in R7.

Although MIMO can significantly improve peak rates, other techniques such

as Space Division Multiple Access (SDMA) - also a form of MIMO - may be

even more effective than MIMO for improving capacity in high spectralefficiency systems using a reuse factor of 1.

CPCCPCCPCCPC

In R7, Continuous Packet Connectivity (CPC) enhancements reduce the

uplink interference created by the DPCCHs of packet data users when those

users have no data to transmit. This, in turn, increases the number of

simultaneously connected HSUPA users. CPC allows both discontinuous

uplink transmission and discontinuous downlink reception, where the mobile


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can turn off its receiver after a certain period of HSDPA inactivity. CPC is

especially beneficial to VoIP on the uplink, which consumes the most power,

because the radio can turn off between VoIP packets.

HigherordermodulationHigherordermodulationHigherordermodulationHigherordermodulation

Another way of increasing performance is to use higher order modulation.

HSPA uses 16 QAM or QPSK on the downlink and QPSK on the uplink. But

radio links can achieve higher throughputs, adding 64 QAM on the downlink

and 16 QAM on the uplink. Higher order modulation requires a better SNR,

which is enabled through other enhancements such as receive diversity and

equalization.

FlatterarchFlatterarchFlatterarchFlatterarchitectureitectureitectureitecture

Another way HSPA performance can be improved is through a flatter

architecture. In R7 there is the option of a one-tunnel architecture by which

the network establishes a direct transfer path for user data between RNC and

GGSN, while the SGSN still performs all control functions. This brings

several benefits such as eliminating hardware in the SGSN and simplified

engineering of the network.

Node B

SGSN

RNC

GGSN

Node B

SGSN

RNC

GGSN

Node B

SGSN

GGSN

control planeuser plane

Figure 1-4 HSPA+ possible architectures


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IntegratedRNC/NodeBIntegratedRNC/NodeBIntegratedRNC/NodeBIntegratedRNC/NodeB

There is also an integrated RNC/NodeB option where RNC functions are

integrated in the Node B. This is particularly beneficial in femtocell

deployments, as an RNC would otherwise need to support thousands of

femtocells. The integrated RNC/NodeB for HSPA+ has been agreed as an

optional architecture alternative for packet-switched based services. Support

of circuit-switched services in HSPA+ must be deployed using the traditional

hierarchical architecture.

These new architectures, are similar to the EPS architecture, especially on the

packet-switched core network side where they provide synergies with the

introduction of LTE.

ROHCROHCROHCROHC

The size of the full IPv6 header together with Real-time Transport Protocol /

User Datagram Protocol (RTP/UDP) header is 60 bytes, while the size of a

typical voice packet is 30 bytes. Without header compression two-thirds of

the transmission would be just headers. IP header compression can be applied

to considerably improve the efficiency of VoIP traffic is HSPA.

Robust Header Compression (ROHC) is a standardized method to compress

the IP, UDP, RTP, and TCP headers of IP packets. This compression scheme

differs from other compression schemes such as IETF RFC 1144 and RFC2508 by the fact that it performs well over links where the packet loss rate is

high, such as wireless links.

The ROHC in the 3GGP is a part of R4. With ROHC, the required data rate

for VoIP is reduced from close to 40 kbps down to below 16 kbps.

HSPA+capabilitiesHSPA+capabilitiesHSPA+capabilitiesHSPA+capabilities

Depending on the features implemented, HSPA+ can exceed the capabilities

of IEEE 802.16e-2005 (mobile WiMAX) in the same amount of spectrum.This is mainly because HSPA MIMO supports closed-loop operation with

precode weighting, as well as multicode word MIMO, and enables the use of

SIC receivers. It is also partly because HSPA supports Incremental

Redundancy (IR) and has lower overhead than WiMAX.


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peak data rate

11.5 Mbps42.2 MbpsHSPA+ R8 2x2MIMO/64QAM/16QAM


11.5 Mbps21.1 MbpsHSPA+ R7 64QAM/16QAM

5.76 Mbps14.4 MbpsHSPA R6

ULDLtechnology

peak data rate



11.5 Mbps21.1 MbpsHSPA+ R7 64QAM/16QAM

5.76 Mbps14.4 MbpsHSPA R6

ULDLtechnology

Figure 1-5 HSPA+ capabilities

HSPA+ will also more than double HSPA capacity as well as reduce latency

below 25 ms. Sleep to data-transfer times of less than 200 ms will improve

users always-connected experience, and reduced power consumption with

VoIP will result in talk times that are more than 50% higher.

From a deployment point of view, operators will be able to introduce HSPA+

capabilities through either a software upgrade or hardware expansions to

existing cabinets to increase capacity.

LTE/LTE/LTE/LTE/EEEE----UTRANUTRANUTRANUTRAN

Although HSPA and HSPA+ offer a highly efficient broadband-wireless

service, 3GPP is working on a project called Long Term Evolution (LTE) as

part of R8. LTE will allow operators to achieve even higher peak throughputs

in higher spectrum bandwidth. Work on LTE began in 2004, with an official

work item started in 2006 and a completed specification expected in early

2008. Initial possible deployment is targeted for 2009.

RequirementsfortheLTEsystemRequirementsfortheLTEsystemRequirementsfortheLTEsystemRequirementsfortheLTEsystem

LTE is focusing on optimum support of Packet Switched (PS) services. Main

requirements for the design of an LTE system were identified in the beginning

of the standardisation work on LTE and have been captured in 3GPP TR

25.913. They can be summarized as follows:

Data rate: Peak data rates target 100 Mbps DL and 50 Mbps UL for

20 MHz spectrum allocation, assuming 2 receive antennas and 1

transmit antenna at the terminal (these requirement values are already

exceeded by the current LTE specification),


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Throughput & spectrum efficiency: Target for downlink average

user throughput per MHz and for spectrum efficiency is 3-4 times

better than release 6. Target for is 2-3 times better than release 6.

Latency: The one-way transit time between a packet being availableat the IP layer in either the UE or radio access network and the

availability of this packet at IP layer in the radio access network/UE

shall be less than 5 ms. Also C-plane latency shall be reduced, e.g. to

allow fast transition times of less than 100 ms from camped state to

active state.

Channel bandwidth: Scalable bandwidths of 5, 10, 15, 20 MHz shall

be supported. Also bandwidths smaller than 5 MHz shall be supported

for more flexibility, i.e. 1.4 MHz and 3 MHz.

Interworking: Interworking with existing UTRAN/GERAN systems

and non-3GPP systems shall be ensured. Multimode terminals shall

support handover to and from UTRAN and GERAN as well as inter-

RAT measurements. Interruption time for handover between E-

UTRAN and UTRAN/GERAN shall be less than 300 ms for real time

services and less than 500 ms for non real time services.

Multimedia Broadcast Multicast Services (MBMS): MBMS shall

be further enhanced and is then referred to as E-MBMS.

Costs: Reduced CAPEX and OPEX including backhaul shall be

achieved. Cost effective migration from release 6 UTRA radio

interface and architecture shall be possible. Reasonable system and

terminal complexity, cost and power consumption shall be ensured.

All the interfaces specified shall be open for multi-vendor equipment

interoperability.

Mobility: The system should be optimized for low mobile speed (0-15

km/h), but higher mobile speeds shall be supported as well including

high speed train environment as special case.

Spectrum allocation: Operation in paired (Frequency Division

Duplex / FDD mode) and unpaired spectrum (Time Division Duplex /

TDD mode) is possible.

Co-existence: Co-existence in the same geographical area and

collocation with GERAN/UTRAN shall be ensured. Also, co-

existence between operators in adjacent bands as well as cross-border

coexistence is a requirement.

Quality of Service: End-to-end Quality of Service (QoS) shall be

supported. VoIP should be supported with at least as good radio and


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backhaul efficiency and latency as voice traffic over the UMTS circuit

switched networks

Network synchronization: Time synchronization of different network

sites shall not be mandated.

data rate: DL 100 Mbps & UL 50 Mbps (already exceeded),

throughput & spectrum efficiency: DL 3-4 x R6, UL 2-3 x R6),

channel bandwidth (5, 10, 15, 20 MHz and smaller),

interworking (GERAN/UTRAN and non-3GPP),

MBMS,

cost reduction,

mobility (optimised for low speeds 0-15 km/h),

spectrum allocation (FDD & TDD),

QoS,

time synchronisation between sites not mandatory.

Figure 1-6 Requirements for the LTE system

LTEtechnologyoverviewLTEtechnologyoverviewLTEtechnologyoverviewLTEtechnologyoverviewLTE uses OFDMA on the downlink, which is well suited to achieve high peak

data rates in high spectrum bandwidth. WCDMA radio technology is basically

as efficient as OFDM for delivering peak data rates of about 10 Mbps in 5

MHz of bandwidth. However, achieving peak rates in the 100 Mbps range

with wider radio channels would result in highly complex terminals, and it is

not practical with current technology. This is where OFDM provides a

practical implementation advantage. Scheduling approaches in the frequency

domain can also minimize interference, thereby boosting spectral efficiency.

approach is also highly flexible in channelization, and LTE will operate invarious radio channel sizes ranging from 1.25 to 20 MHz.

On the uplink, however, a pure OFDMA approach results in high Peak to

Average Ratio (PAR) of the signal, which compromises power efficiency and,

ultimately, battery life. Hence, LTE uses an approach called SC-FDMA,

which is somewhat similar to OFDMA but has a 2 to 6 dB PAR advantage

over the OFDMA method used by other technologies such as IEEE 802.16e.


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LTE capabilities include:

Downlink peak data rates up to 326 Mbps with 20 MHz bandwidth.

Uplink peak data rates up to 86.4 Mbps with 20 MHz bandwidth.

Operation in both TDD and FDD modes.

Scalable bandwidth up to 20 MHz, covering 1.25, 2.5, 5, 10, 15, and

20 MHz. Channels that are 1.6 MHz wide are under consideration for

the unpaired frequency band, where a TDD approach will be used.

Increased spectral efficiency over R6 HSPA by a factor of two to four.

Reduced latency, to 10 ms RTT between user equipment and the

eNodeB, and to less than 100 ms transition time from inactive to

active.The overall intent is to provide an extremely high-performance radio-access

technology that offers full vehicular speed mobility and that can readily

coexist with HSPA and earlier networks. Because of scalable bandwidth,

operators will be able to easily migrate their networks and users from HSPA

to LTE over time.

peak data rate

86.4 Mbps326.4 Mbps4x4 MIMO/64QAM


ULDLLTE configuration

peak data rate



ULDLLTE configuration

Figure 1-7 LTE bitrates (20 MHz channel)

OFDMOFDMOFDMOFDM

Orthogonal Frequency Division Multiplexing (OFDM) uses a large number of

narrow sub-carriers for multi-carrier transmission. The basic LTE downlink

physical resource can be seen as a time-frequency grid, as illustrated in

Fig 1-6. In the frequency domain, the spacing between the subcarriers, f, is

15 kHz. The number of subcarriers ranges from 75 in a 1.25 MHz channel to

1,200 in a 20 MHz channel. In addition, the OFDM symbol duration time is

1/f + cyclic prefix. The cyclic prefix is used to maintain orthogonally

between the sub-carriers even for a time-dispersive radio channel.

One resource element carries QPSK, 16QAM or 64QAM. With 64QAM, each

resource element carries six bits.


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The OFDM symbols are grouped into resource blocks. The resource blocks

have a total size of 180 kHz in the frequency domain and 0.5 ms in the time

domain. Each 1ms TTI consists of two slots (Tslot).

Each user is allocated a number of so-called resource blocks in the timefrequency grid. The more resource blocks a user gets, and the higher the

modulation used in the resource elements, the higher the bit-rate.

Which resource blocks and how many the user gets at a given point in time

depend on advanced scheduling mechanisms in the frequency and time

dimensions. The scheduling mechanisms in LTE are similar to those used in

HSPA, and enable optimal performance for different services in different

radio environments.

f

t 12 subcarriers, 180 kHz

Oneslot

(Tslot=0.5ms,7O

FDMsym

bols)

Resource block

(12 x 7 = 84 resource elements)

Resource element

QPSK 2 bits,

16QAM 4 bits,

64QAM 6 bits,

15 kHz

Figure 1-8 OFDMA concept

The basic principle of OFDM is to split a high-rate data stream into a number

of parallel low-rate data streams, each a narrowband signal carried by a

subcarrier. The different narrowband streams are generated in the frequency

domain and then combined to form the broadband stream using a

mathematical algorithm called an Inverse Fast Fourier Transform (IFFT) thatis implemented in DSPs.

By having control over which subcarriers are assigned in which sectors, LTE

can easily control frequency reuse. By using all the subcarriers in each sector,

the system would operate at a frequency reuse of 1; but by using a different

one third of the subcarriers in each sector, the system achieves a looser

frequency reuse of 1/3. The looser frequency reduces overall spectral

efficiency but delivers high peak rates to users.

In the uplink, LTE uses a pre-coded version of OFDM called Single Carrier

Frequency Division Multiple Access (SC-FDMA). This is to compensate for a


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drawback with normal OFDM, which has a very high PAR. High PAR

requires expensive and inefficient power amplifiers with high requirements on

linearity, which increases the cost of the terminal and drains the battery faster.

SC-FDMA solves this problem by grouping together the resource blocks insuch a way that reduces the need for linearity, and so power consumption, in

the power amplifier. A low PAR also improves coverage and the cell-edge

performance.

AdvancedantennasAdvancedantennasAdvancedantennasAdvancedantennas

Advanced antenna solutions that are introduced in HSPA+ are also used by

LTE. Solutions incorporating multiple antennas meet next-generation mobile

broadband network requirements for high peak data rates, extended coverage

and high capacity.

Advanced multi-antenna solutions are key components to achieve these

targets. There is not one antenna solution that addresses every scenario.

Consequently, a family of antenna solutions is available for specific

deployment scenarios. For instance, high peak data rates can be achieved with

multi-layer antenna solution such as 2x2 or 4x4 MIMO whereas extended

coverage can be achieved with beam-forming.

ProtocolsProtocolsProtocolsProtocols

The LTE physical layer solely provides shared channels to the higher layers

using a 1 ms TTI. LTE relies on rapid adaptation to channel variations,

employing rate adaptation and HARQ with soft-combining in much the same

way as is done in HSPA. The use of OFDM and SC-FDMA makes it possible

to exploit variations in both the frequency and time domains.

The architecture of the radio interface protocol is based on that for HSPA.

The names of the protocols are the same, in fact, and the functions are similar.

Some distinctions stem from differences in the multiple access techniques of

LTE and HSPA. Others relate to the fact that LTE is a packet-only system(that is, there are no requirements to support the legacy circuit-switched

domain). Fig. 1-8 and Fig. 1-9 show the architecture of the LTE radio

interface protocol. Note: Apart from the NAS protocols, all radio interface

protocols terminate in the eNodeB on the network side.

Packet Data Convergence Protocol (PDCP) handles the header compression

and security functions of the radio interface; the Radio Link Control (RLC)

protocol focuses on lossless transmission of data; and the Media Access

Control (MAC) protocol handles uplink and downlink scheduling and HARQ

signalling. Similarly, the Radio Resource Control (RRC) protocol handles

radio bearer setup, active mode mobility management, and broadcasts of


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system information, while the NAS protocols deal with idle mode mobility

management and service setup.

IP

PDCP

RLC

MAC

PHY

UE

RLC

MAC

PHY

eNode B

PDCP

IP

GW

IP

Figure 1-9 LTE protocols (user plane)

NAS

RRC

RLC

MAC

PHY

UE

RLC

MAC

PHY

eNode B

RRC

NAS

MME

PDCP PDCP

Figure 1-10 LTE protocols (control plane)

The RTT for E-UTRAN is around 7 ms, one way delay 3,5 ms and HARQ

RTT 5 ms.

UE eNode B

1 ms 1.5 ms 1 ms

1 ms 1 ms1.5 ms

TTI + framealignment

HARQ RTT 5 ms

Figure 1-11 LTE user plane delay


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EPS/SAEEPS/SAEEPS/SAEEPS/SAE

3GPP is defining EPS (previously called SAE) in R8 as a framework for anevolution of the 3GPP system to a higher-data-rate, lower-latency packet-

optimized system that supports multiple radio-access technologies. The focus

of this work is on the PS domain, with the assumption that the system will

support all services - including voice - in this domain.

Although it will most likely be deployed in conjunction with LTE, EPS could

also be deployed for use with HSPA+, where it could provide a stepping-

stone to LTE. EPS will be optimized for all services to be delivered via IP in a

manner that is as efficient as possible - through minimization of latency

within the system, for example. It will support service continuity acrossheterogeneous networks, which will be important for LTE operators that must

simultaneously support GSM/GPRS/EDGE/UMTS/HSPA customers.

One important performance aspect of EPS is a flatter architecture. For packet

flow, EPS includes two network elements, called Evolved Node B (eNodeB)

and the Access Gateway (AGW). The eNode B (base station) integrates the

functions traditionally performed by the RNC, which previously was a

separate node controlling multiple Node Bs. Meanwhile, the AGW integrates

the functions traditionally performed by the SGSN. The AGW has both

control functions, handled through the Mobility Management Entity (MME),

and user plane (data communications) functions. The user plane functionsconsist of two elements: a serving gateway that addresses 3GPP mobility and

terminates eNode B connections, and a Packet Data Network (PDN) gateway

that addresses service requirements and also terminates access by non-3GPP

networks.

The MME, serving gateway, and PDN gateways can be collocated in the same

physical node or distributed, based on vendor implementations and

deployment scenarios. The EPS architecture is similar to the HSPA One-

Tunnel Architecture, discussed in the HSPA+ section, which allows for

easy integration of HSPA networks to the EPS. EPS also allows integration ofnon-3GPP networks such as WiMAX. EPS will use IMS as a component. It

will also manage QoS across the whole system, which will be essential for

enabling a rich set of multimedia-based services.

Elements of the EPS architecture include:

Support for legacy GERAN and UTRAN networks connected via

SGSN.

Support for new radio-access networks such as LTE.


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The Serving Gateway that terminates the interface toward the 3GPP

radio-access networks.

The PDN gateway that controls IP data services, does routing,

allocates IP addresses, enforces policy, and provides access for non-3GPP access networks.

The MME that supports UE context and identity as well as

authenticates and authorizes users.

The Policy Control and Charging Rules Function (PCRF) that

manages QoS aspects.

AGW

LTE

eNode B

PDN GW

Serving GW

HSS

PCRF

IP networks /IMS / services

WCDMA/HSPAGSM

non-3GPPaccess

SGSN

MME

Figure 1-12 EPS / SAE architecture

IMSIMSIMSIMS

IMS is a service platform that allows operators to support IP multimedia

applications. Potential applications include video sharing, PoC, VoIP,

streaming video, interactive gaming, and so forth. IMS by itself does not

provide all these applications. Rather, it provides a framework of application

servers, subscriber databases, and gateways to make them possible. The exact

services will depend on cellular operators and application developers that

make these applications available to operators.

The core networking protocol used within IMS is Session Initiation Protocol

(SIP), which includes the companion Session Description Protocol (SDP)

used to convey configuration information such as supported voice codecs.


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Other protocols include Real-time Transport Protocol (RTP) and Real Time

Streaming Protocol (RTSP) for transporting actual sessions. The QoS

mechanisms in UMTS is an important component of some IMS applications.

Although originally specified by 3GPP, numerous other organizations aroundthe world are supporting IMS. These include the Internet Engineering

Taskforce (IETF), which specifies key protocols such as SIP, and the Open

Mobile Alliance (OMA), which specifies end-to-end service-layer

applications. Other organizations supporting IMS include the GSM

Association (GSMA), the ETSI, CableLabs, The Parlay Group, the ITU, the

American National Standards Institute (ANSI), the Telecoms and Internet

converged Services and Protocols for Advanced Networks (TISPAN), and the

Java Community Process (JCP).

IMS is relatively independent of the radio-access network and can, and likelywill, be used by other radio-access networks or even by wireline networks.

As shown in Fig. 1-13, IMS operates just outside the packet core.

Call Session Control Function (CSCF)(SIP proxy)

HSS

Media Gateway

Control Function

Media ResourceFunction (MRF)

SIPApplication

Server (AS)

IMS

DSL3GPP CN WiFi

Figure 1-13 IMS architecture

The benefits of using IMS include handling all communication in the packet

domain, tighter integration with the Internet, and a lower cost infrastructure

that is based on IP building blocks and common between voice and data

services. This allows operators to potentially deliver data and voice services at

lower cost, thus providing these services at lower prices and further driving

demand and usage.

IMS applications can reside either in the operators network or in third-party

networks, including enterprises. By managing services and applications

centrally, and independently of the access network, IMS can enable network

convergence. This allows operators to offer common services across 3G,

WiFi, and even wireline networks.


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ChapterChapterChapterChapter2222

ArchitectureArchitectureArchitectureArchitecture

TopicTopicTopicTopic PagePagePagePage

Non-roaming architecture ................................................................................ 29

Roaming architecture .......................................................................................37

Arch. for non-3GPP access .............................................................................. 39

Interfaces..........................................................................................................41

Geographical network structure....................................................................... 43

Identities........................................................................................................... 45


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Some additional nodes are also required for interworking with other (non

LTE) radio access technologies. Example of such node is SGSN that is used

for interworking with GERAN and UTRAN.

MMEMMEMMEMME

The Mobility Management Entity (MME) is in charge of all control plane

functions related to subscriber and session management. From that

perspective, the MME supports as follows:

Non-access Stratum Signalling (NAS) i.e. signalling between UE and

the Evolved Packet Core (EPC) network this relates to all signalling

procedures related with terminal location management (tracking area

update procedure) and procedures used to setup a packet data context(connection for user data) and negotiate associated parameters like

Quality of Service (QoS).

Inter Core Network (CN) node signalling for handling mobility

between different types of 3GPP access networks, i.e. signalling with

SGSN exchanged over S3 interface.

Security procedures this relates to end-user authentication, end-user

equipment check, as well as initiation and negotiation of ciphering and

integrity protection algorithms.

Tracking Area (TA) list management.

Idle UE reachability, e.g. control and execution of paging

transmission.

Selection of other CN nodes:

o S-GW and PDN-GW for the purpose of user data transmission,

o MME for handovers with MME change,

o SGSN for handovers to GERAN or UTRAN.

Roaming, i.e. MME handles interface toward subscribers HPLMNHLR.

The MME is linked through the S6a interface to the HSS which supports the

database containing all the user subscription information.


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GatewaysGatewaysGatewaysGateways

Two logical Gateways exist: Serving GW (S-GW),

PDN GW (P-GW).

The P-GW and the S-GW may be implemented in one physical node or

separated physical nodes.

MME

E-UTRAN

P-GWS-GW

S1-U

S1-MME

S11

IP/IMS

SGi

S6a HSS

Figure 2-2 S-GW and P-GW in one physical node

Also the S-GW and the MME may be implemented in one physical node or

separated physical nodes.

MME

E-UTRAN

P-GWS-GW

IP/IMSSGi

S6a HSS

S5

S1

Figure 2-3 MME and S-GW in one physical node

SSSS----GWGWGWGW

The Serving Gateway (S-GW) is the gateway which terminates the interface

towards E-UTRAN. For each UE associated with the EPS, at a given point of

time, there is a single S-GW.

The functions of the S-GW, include:

Packet routeing and forwarding,

Transport level packet marking in the uplink and the downlink, e.g.

setting the DiffServe Code Point, based on the QoS Class Identifier

(QCI) of the associated EPS bearer,

Downlink packet buffering and initiation of network triggered

service request procedure for Idle UEs,


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The local mobility anchor point for inter-eNodeB handover and

assistance in packet reordering during inter-eNodeB handover,

Mobility anchoring for inter-3GPP mobility (relaying the traffic

between 2G/3G system and P-GW,

Charging and accounting,

Lawful interception.

PPPP----GWGWGWGW

The PDN GW is the gateway which terminates the SGi interface towards the

PDN. If a UE is accessing multiple PDNs, there may be more than one PDN

GW for that UE.

PDN GW functions include:

Transport level packet marking in the uplink and the downlink,

UE IP address allocation,

Per-user based packet filtering (by e.g. deep packet inspection),

UL and DL service level charging ,

UL and DL service level rate enforcement,

UL and DL service level gating control,

Lawful Interception,

DHCP functions,

SGSNSGSNSGSNSGSN

The Serving GPRS Support Node (SGSN), in addition to the functions

handled earlier in 2G/3G network, is responsible for:

Inter EPC node signalling for mobility between 2G/3G and E-

UTRAN,

PDN and Serving GW selection,

MME selection for handovers to E-UTRAN.

PCRFPCRFPCRFPCRF

The Policy and Charging Rules Function (PCRF). PCRF functions are

described in more detail later in this book.


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HSSHSSHSSHSS

The Home Subscriber Server (HSS) is the concatenation of the HomeLocation register (HLR) and the Authentication Centre (AuC) two functions

being already present in 2G GSM and 3G UMTS networks. The HLR part of

the HSS is in charge of storing and updating when necessary the database

containing all the user subscription information, including:

user identification and addressing this corresponds to the

International Mobile Subscriber Identity (IMSI) and Mobile

Subscriber ISDN Number (MSISDN),

user profile information this includes service subscription states and

user-subscribed Quality of Service (QoS) information (such asmaximum allowed bit rate or allowed traffic class),

The AuC part of the HSS is in charge of generating security information from

user identity keys. This security information is provided to the HLR and

further communicated to other entities in the network. Security information is

mainly used for:

mutual network-terminal authentication,

radio path ciphering and integrity protection, to ensure data and

signalling transmitted between network and the terminal is neither

eavesdropped nor altered.

Introduced from the very beginning of the GSM network standardisation,

HLR and AuC boxes were eventually joined together in a single HSS node as

IMS was defined by the 3GPP. In its extended role, the HSS of Evolved

UMTS networks integrates both HLR and AuC features, including classical

MAP features (for support of CS and PS sessions), IMS-related functions, and

all necessary functions related to the new EPC.

2G/3G PS domain2G/3G CS domain

IMS EPC

HLR

AUC

HSSI/S-CSCF

GMSC

VLR SGSN

GGSN

MMES6a

Gc

S6b

Gr

Cx

C

D

Figure 2-4 HSS structure and external interfaces


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There are actually three main cases in which the HSS is actively involved:

At user registration the HSS is interrogated by the corresponding CN

node as the user attempts to register to the network in order to check

the user subscription rights. This can be done by either the MSC, theSGSN, I-CSCF or the MME, depending on the type of network and

registration being requested;

In the case of terminal location update as the terminal changes

location areas, the HSS is kept updated and maintains a reference of

the last known are;

In the case of user-terminated session request the HSS is

interrogated and provides a reference of the CN node corresponding to

the current user location.

EEEE----UTRANUTRANUTRANUTRAN

Coming back to the first releases of the UMTS standard, the UTRAN

architecture was initially very much aligned with GSM access network

(GERAN) concepts. As described in Fig. 2-5, the UTRAN network is

composed of the radio equipment (known as NodeB or Base Station) in

charge of transmission and reception over the radio interface, and the Radio

Network Controller (RNC) in charge of NodeB configuration and radio

resource allocation. A single RNC may possibly control a large number of

NodeBs over the Iub interface.

In addition, an inter-RNC Iur interface was defined to allow UTRAN call

anchoring at the RNC level and macro-diversity between different NodeBs

controlled by different RNCs. Macro-diversity was a consequence of

CDMA-based UTRAN physical layer, as means to reduce radio interference

and preserve network capacity. The initial UTRAN architecture resulted in a

simplified NodeB implementation, and a relatively complex, sensitive, high-

capacity and feature-rich RNC design. In this model, the RNC had to support

resources and traffic management features as well as a significant part of theradio protocols. Compared with UTRAN, the E-UTRAN OFDM-based

structure is quite simple. It is only composed of one network element: the

evolved NodeB (eNodeB).


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Core Network

Iur

Iub Iub

Iu Iu

RNCRNC

IubIub

NodeB NodeB

NodeBNodeB

Core Network

X2

S1

eNodeB eNodeB

S1

UTRAN E-UTRAN

Figure 2-5 UTRAN and E-UTRAN architectures

The 3G RNC inherited from the 2G BSC has disappeared from E-UTRAN

and the eNodeB is directly connected to the Core Network (CN) using S1

interface. As a consequence, the features supported by the RNC have been

distributed between the eNodeB and the CN entities.

An eNodeB can be implemented either as a single-cell equipment providing

coverage and services in one cell only, or as a multi-cell node, where each cell

is covering a given geographical sector.

omnidirectional eNodeB sectorised eNodeB

Figure 2-6 Omnidirectional and sectorised eNodeBs

A new X2 interface has been defined between eNodeBs, working in a meshed

way (meaning that all NodeBs may possibly be linked together). The main

purpose of this interface is to minimise packet loss due to user mobility. As

the terminal moves across the access network, unsent or unacknowledged

packets stored in the old eNodeB queues can be forwarded to the new eNodeB

thanks to the X2 interface.


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S1

Tx Re-Tx

HO

Tx Re-Tx

X2

Core Network

S1

Figure 2-7 X2 interface

From a high-level perspective, the new E-UTRAN architecture is actually

moving towards WLAN network structures and WiFi or WiMAX base

stations functional definition. eNodeB as WLAN access points support

all L1 and L2 features associated to the E-UTRAN OFDM physical interface,

and they are directly connected to the network routers. There is no more

intermediate controlling node (as the 2G BSC or 3G RNC was).

This has a merit of a simpler network architecture (fewer nodes of different

types, which means simplified network operation) and allows betterperformance over the radio interface.

From the functional perspective, the eNodeB supports a set of legacy features,

all related to physical layer procedures for transmission and reception over the

radio interface:

modulation and de-modulation,

channel coding and decoding.

Besides, the eNodeB includes additional features, coming form the fact that

there are no more Base Station controllers in the E-UTRAN architecture:

radio resource control: this relates to the allocation, modification and

release of resources for the transmission over the radio interface

between the user terminal and the eNodeB.

mobility management: this refers to a measurement processing and

handover decision.

full L2 protocol: this refers detection and possibly correction of errors

that may occur in the physical layer (this function in UTRAN was

fully or for some services partially handled by RNC).


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RoamingarchitectureRoamingarchitectureRoamingarchitectureRoamingarchitecture

This section describes the case, both the visited and the home networks areEPC networks. Other cases, i.e. migration routes to this target roaming

architecture are left by 3GPP for further studies. Two alternative architectures

are shown, depending on whether UE traffic has to be routed to the HPLMN

or not.

UsertrafficroutedtotheHPLMNUsertrafficroutedtotheHPLMNUsertrafficroutedtotheHPLMNUsertrafficroutedtotheHPLMN

Fig. 2-8 presents the EPC architecture support for roaming cases. In this

example, a user has subscribed to HPLMN A, but is currently under the

coverage of the VPLMN B. This kind of situation may happen while the user

is travelling to another country, or in case in which a national roaming

agreement has been set up between operators, so as to decrease the investment

effort for national coverage. In such a roaming situation, part of the session is

handled by the VPLMN. This includes E-UTRAN access network support,

session signalling handling by the MME, and user plane routing through the

local S-GW. Thanks to local MME and S-GW, the VPLMN is then able to

built and send charging tickets to the subscriber home operator ,

corresponding to the amount of data transferred and QoS allocated.

UTRAN

SGSN

MME

E-UTRAN

P-GWS-GW

PCRF

S1-U

S1-MME

S11

S8

S10

HSSS6a

S4 S12

OperatorsIP

Services(e.g. IMS,

PSS, etc.)

SGi

Gx

Rx

LTE-Uu

GERAN

UE

S3

MME

VPLMN HPLMN

Figure 2-8 Roaming architecture (HPLMN routed traffic)

However, since the terminal user has no subscription with the VPLMN, the

Visited EPC needs to be linked to the HSS of the user home network, at least

to retrieve the user-specific security credential needed for authentication and

ciphering. In the roaming architecture , the session path goes through the


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Home P-GW over the S8 interface, so as to apply policy and charging rules in

the home network corresponding to the users subscription parameters.

The S8 interface is in fact a roaming variant of S5 reference point, to support

both signalling and data transfer between S-GW located in VPLMN andP-GW located in the HPLMN.

Briefly, in such a model, the VPLMN provides the access connectivity (which

also involves the basic session signalling procedures supported by the Visited

MME, with the support of the Home HSS), whereas the HPLMN still

provides the access to external networks, possibly including IMS-based

services.

UsertrafficnotrUsertrafficnotrUsertrafficnotrUsertrafficnotroutedtotheHPLMNoutedtotheHPLMNoutedtotheHPLMNoutedtotheHPLMN

In the previous model, the call is still anchored to the Home IASA, hence the

home routed traffic denomination. The user packet routing in such a scheme

may, however, be quite inefficient in terms of cost and network resources as

the Home P-GW and Visited S-GW may be very far from each other. This is

the reason why the 3GPP standard also allows the possibility of the user

traffic to be routed via a Visited P-GW, as an optimisation. This may be very

beneficial in the example of public Internet access as routing the traffic to

the HPLMN does not add any value to the end user and even more in the

case of an IMS session established between a roaming user and a subscriber

of the visited network. In the last case, local traffic routing avoids a complete

round trip of user data trough the HPLMN anchors.

Fig. 2-9 and describe possible network architecture in the case where the

traffic is routed locally or the local breakout case. Both gateways are part

of the VPLMN.

HomeOperatorsServices

UTRAN

SGSN

MME

E-UTRAN

P-GWS-GW

vPCRF

S1-U

S1-MME

S11

S5

S10

HSS

S6a

S4 S12

VisitedOperators

PDNSGi

Gx

Rx

LTE-Uu

GERAN

UE

S3

MME

VPLMN HPLMN

hPCRF

S9

Rx

Figure 2-9 Roaming architecture (local breakout)


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If the networks make use of PCRF, one of the possible solutions is that the

enforcement of the HPLMN policies (QoS and charging policies) by the

Visited P-GW is performed through the interaction of Home and Visited

PCRF. Possibly, the Visited PCRF may add/modify policies according tothose defined in the VPLMN. The related reference point between PCRFs is

referred as S9.

ArchArchArchArch....fornonfornonfornonfornon----3GPPaccess3GPPaccess3GPPaccess3GPPaccess

A non-3GPP IP Access Network is defined as atrusted non-3GPP IP Access

Network if the 3GPP EPC system chooses to trust such non-3GPP IP accessnetwork. The 3GPP EPC system operator may choose to trust the non-3GPP

IP access network operated by the same or different operators, e.g. based on

business agreements.

Note that specific security mechanisms may be in place between the trusted

non-3GPP IP Access Network and the 3GPP EPC to avoid security threats. It

is assumed that an IPSec tunnel between the UE and the 3GPP EPC is not

required.

On the contrary, an untrusted non-3GPP IP Access Network is an IP access

network where 3GPP network requires use of IPSec between the UE and the3GPP network in order to provide adequate security mechanism acceptable to

3GPP network operator. An example of such untrusted non-3GPP IP access is

WLAN and it is made trusted in the Interworking WLAN specifications

developed within 3GPP.

In the current standardisation documents, a trusted non-3GPP IP access is also

referred to as the non-3GPP IP access, and an untrusted non-3GPP IP accesses

are accommodated by is also referred to as the WLAN 3GPP IP access.

TrustedNonTrustedNonTrustedNonTrustedNon----3GPPIPAccess3GPPIPAccess3GPPIPAccess3GPPIPAccess

Fig. 2-10 represents the network architecture providing IP connectivity to the

EPC using non-3GPP type of access. This architecture is independent from

the access technology, which could be WiFi, WiMAX or any other kind of

access type. This picture applies to the trusted WLAN access, corresponding

to the situation where the WLAN network is controlled by the operator itself

or by another entity (local operator or service provider) which can be trusted

due to the existence of mutual agreements.


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Trustednon 3GPPIP Access

HSS

3GPP AAA

Server

MME

E-UTRAN

PCRF

OperatorsIP

(services:IMS, PSS,

etc)Wx

Ta

P-GWS2a

S7

SGi

Rx

Non-3GPPnetwork

3GPPnetwork

S-GW

Figure 2-10 Trusted Non-3GPP IP Access architecture

As described below, some new network nodes and interfaces are needed to

support non-3GPP access types. In contrast, on terminal side, no changes are

required except some slight software adaptations. This comes from the fact

that Authentication Authorisation and Accounting (AAA) mechanisms for

mutual authentication and access control are based on known IETF protocols

but make use of the 3GPP UICC stored credentials.

The 3GPP AAA Servers role is to act as an inter-working unit between the

3GPP world and IETF standard-driven WLAN networks from the securityperspective. Its purpose is to allow end-to-end authentication with WLAN

terminals using 3GPP credentials. For that reason, the 3GPP AAA Server has

an access to the HSS through Wx interface, so as to retrieve user-related

subscription information and 3GPP authentication vectors.

From the 3GPP AAA Server, the Ta interface has been defined with the

trusted access network, aiming at transporting authentication, authorization

and charging-related information in a secure manner.

From the user plane perspective, the user data are transmitted from the

WLAN to the P-GW through the new S2a interface. As in legacy EPCarchitecture, the P-GW still serves as an anchor point for the user traffic.

In such a model, the 3GPP Anchor and MME UPE nodes are not needed any

more. Terminal location management is under the responsibility of the

WLAN Access as well as the packet session signalling and does not need any

support from 3GPP EPC nodes (aside from the provision of 3GPP security

credentials). In the example of a 802.11 WiFi access point, user association

(the process by with a WiFi terminal connects to an access point), security

features as well as radio protocols are handled by the access point itself.


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In addition to the trusted model, the standard defines another model, for the

situations where WLAN is untrusted. This model is described in Fig. 2-11. As

an example, this may correspond to a business entity deploying a WLAN for

its internal use and willing to offer 3GPP connectivity to some of itscustomers. In such a case, the WLAN-3GPP interconnection looks a bit

different due to additional mechanism to maintain legacy 3GPP infrastructure

security and integrity.

Untrustednon 3GPP

IP Access

HSS

3GPP AAA

Server

MME

E-UTRAN

PCRF

Operators

IP(services:

IMS, PSS,

etc)

Wx

Ta

P-GW SGi

Rx

Non-3GPP

network

3GPP

network

S-GW

ePDGWn

Wm

S2b

S7

Figure 2-11 Untrusted Non-3GPP IP Access architecture

This model introduced a evolved Packet Data Gateway (ePDG) node which

concentrates all the traffic issued or directed to the WLAN network. Its main

role is to establish a secure tunnel for user data transmission with the terminal

using IPSec and filter unauthorised traffic.

In this model, the new Wm interface is introduced for the purpose of

exchanging user-related information from the 3GPP AAA Server to the

ePDG. This will allow the ePDG to enable proper user data tunnelling and

encryption to the terminal.

InterfacesInterfacesInterfacesInterfaces

It is important to note, that the interfaces shown in Fig. 2-1 are logical

interfaces, i.e. they have no close relation with the physical network structure

and transmission. The connectivity between nodes will be handled by IP

network, operating on longer distances on top of SDH transmission network

and possibly on shorter distances on Carrier Ethernet, Gigabit Ethernet or


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even ADSL technologies. In such case the logical interface between two

nodes exist if only they are able to exchange information across IP network.

This means also, that they are aware of their functions and IP addresses,

which are configured either statically by means of O&M commands ordynamically by means of some signalling protocols.

SGSN

MMEP-GW

S-GW

PCRF

HSS

EIR

eNodeB

eNodeB

P-GW

S-GW

MME

eNodeB

Figure 2-12 Interfaces & connectivity

The protocol stacks used across the EPS interfaces are listed in Fig. 2-13.

Diameter/SCTP/IPP-GW PCRFGx

GTP-C/UDP/IPMME/SGSNMSCSv

SGsAP/SCTP/IPMME MSCSGs

Diameter/SCTP/IPSGSN HSSS6b

IPS-GW PDNSGi

S1-AP/SCTP/IPeNB

MMES1-MME

Diameter/SCTP/IPPCRF AFRx

X2-AP/SCTP/IPeNB eNBX2

Diameter/SCTP/IPMME EIRS13

GTP-U/UDP/IPS-GW RNCS12

GTP-C/UDP/IPMME S-GWS11

GTP-C/UDP/IPMME MMES10

Diameter/SCTP/IPvPCRF hPCRFS9

GTP/UDP/IP or PMIPvS-GW hP-GWS8

Diameter/SCTP/IPMME HSSS6a

GTP/UDP/IP or PMIPS-GW P-GWS5

GTP/UDP/IPS-GW SGSNS4

GTP-C/UDP/IPMME SGSNS3

GTP-U/UDP/IPeNB S-GWS1-U

Protocol stackNodesInterface

Diameter/SCTP/IPP-GW PCRFGx

GTP-C/UDP/IPMME/SGSNMSCSv

SGsAP/SCTP/IPMME MSCSGs

Diameter/SCTP/IPSGSN HSSS6b

IPS-GW PDNSGi

S1-AP/SCTP/IPeNB

MMES1-MME

Diameter/SCTP/IPPCRF AFRx

X2-AP/SCTP/IPeNB eNBX2

Diameter/SCTP/IPMME EIRS13

GTP-U/UDP/IPS-GW RNCS12

GTP-C/UDP/IPMME S-GWS11

GTP-C/UDP/IPMME MMES10

Diameter/SCTP/IPvPCRF hPCRFS9

GTP/UDP/IP or PMIPvS-GW hP-GWS8

Diameter/SCTP/IPMME HSSS6a

GTP/UDP/IP or PMIPS-GW P-GWS5

GTP/UDP/IPS-GW SGSNS4

GTP-C/UDP/IPMME SGSNS3

GTP-U/UDP/IPeNB S-GWS1-U

Protocol stackNodesInterface

Figure 2-13 Protocols on EPS interfaces


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GeographicalnetworkstructureGeographicalnetworkstructureGeographicalnetworkstructureGeographicalnetworkstructure

For all mobiles not being in idle mode, location management is still animportant item, as the network needs to know the current terminal location at

any time in case of mobile-terminated session setup or push services.

However, idle mode procedures do not require the network to know each

terminal location with the high degree of accuracy (such as the cell level). For

that reason, the concept of Tracking Area (TA) has been introduced.

Basically, a TA is defined as a set of contiguous cells. The identity of the TA

the cell belongs to, or Tracking Area Identity (TAI), is part of the system

information broadcast on Broadcast Control Channel (BCCH). As in the

3GPP definition, TAs do not overlap each other. When the network needs tojoin the terminal, a paging message is sent in all the cells which belong to the

Tracking Area.

The current terminal TA is signalled to the EPC at initial registration and

when UE changes the zones. In addition, the current TA is periodically

updated, even if it does not change, so that the EPC network does not keep

alive a context for a terminal which is no longer reachable in the network.

This can happen if the terminal fails to de-register or runs out of coverage.

As an enhancement to UMTS, the standard leaves the possibility for the

terminal to be registered into multiple TAs. In this situation , the terminaldoes not perform any TA update as long as it remains under the coverage of

the TAs it was registered to (like TA1, TA2 and TA3 in Fig. 2-14), with the

exception of periodic TA update. This multi-TA registration mechanism helps

to reduce the number of TA updates that the network has to process for

terminals located at the edge of TAs.

TA#3

TA#7

TA#8

TA#9

TA#1

TA#2

TA#4

TA#5

TA#6

TA update

Figure 2-14 Tracking Area (TA)


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The list of TAs that the UE is registered to is communicated by the network

during the TA update process. The UE considers it is registered to the whole

TA list until it enters a TA which does not belong to the list, or gets an update

list from the network, e.g. on the occasion of periodic TA update.The concept of location area, such as the TA, is not new to EPS, a sit was

introduced at the beginning of GSM system. Letter on, when GPRS and

UMTS were introduced, this principle become more complex. In UMTS, as

presented in Fig. 2-15, no less than four types of areas are being used:

Location Area (LA), which is a type of area supported by the CS CN

domain,

Routing Area (RA), which is the equivalent of the LA for the PS CN

domain,

UTRAN Registration Area (URA), which is a registration area for the

use of the UMTS access network,

Cell, which provides the best accuracy localisation information.

URA #1 URA #1 URA #1

RA #1

LA #1

RA #2 RA #3 RA #4 RA #5

LA #2 LA #3

Figure 2-15 UMTS location areas

RA is defined in such a way that a LA may include one or more RA. URA

was introduced to provide flexibility in UTRAN terminal location

management, in connection with the protocol states which were introduced in

the UTRAN RRC layer. As it is managed by the UTRAN, URA has no

relation with the CNs LA and RA.

LA and RA are quite similar to the concept of TA, as being a non-overlapping

group of cells. However, the URA concept has no equivalent in E-UTRAN.

The possibility of defining overlapping URA was introduced as a way to

decrease the signalling load impact of URA update, similarly to the TA list

registration concept presented above.


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From the perspective of the terminal location management, EPS has been

simplified ,a s there is only one type of CN domain (the EPC) and no

registration area has been defined for the access network like the UTRANs

URA. This will also have an impact on RRC state management simplification.

IdentitiesIdentitiesIdentitiesIdentities

Similarly to GSM/UMTS, EPS uses a number of descriptors to identify

subscribers. In Fig. 2-16 the EPS nodes are presented together with the

identities used by these nodes for various identification purposes.

MSISDN

IMSI

IMEI

P-TMSI

UTRAN

SGSN

MME

E-UTRAN

P-GWS-GW

HSS

EIR

GERAN

UE

IMSI IMEI

IMSIIMEI

IMEI

IMSI

IMEI

P-TMSI

PDP

address

IMSIIMEI GUTI

PDP address

PDP

address

GUTI

Static PDP address ?

MSISDNIMSI IMEI

Figure 2-16 EPS identities

IMSIIMSIIMSIIMSI

The unique identity for mobile subscriber is called International MobileSubscriber Identity (IMSI). IMSI consists of three parts:

MCC - Mobile Country Code (three digits),

MNC - Mobile Network Code (2-3 digits),

MSIN - Mobile Station Identification (up to 10 digits).

This number is stored on the SIM and acts acts as the unique database search

key in the HSS, MME and SGSN.


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TAC SNR

IMEI

spare

Figure 2-19 IMEI

TAC - Type Approval Code - Is a 8 digits length code that

identifies the particular type of the mobile equipment.

SNR - Serial Number (6 digits)

Spare - (1 digit)

The IMEI (14 digits) is complemented by a check digit. The check digit is not

part of the digits transmitted when the IMEI is checked. The Check Digit is

intended to avoid manual transmission errors, e.g. when customers registerstolen mobile equipment at the operator's customer care desk.

GUTI,MGUTI,MGUTI,MGUTI,M----TMSIandSTMSIandSTMSIandSTMSIandS----TMSITMSITMSITMSI

The MME allocates a Globally Unique Temporary Identity (GUTI) to the UE.

The GUTI has two main components:

Globally Unique MME Identifier (GUMMEI) uniquely identifying the

MME which allocated the GUTI,

M-TMSI uniquely identifying the UE within the MME that allocated

the GUTI.

GUTI/IMSI IMSI

GUTIIMSI

IMSI

new GUTI

IMSIGUTI

new GUTI

MME P-GW

HSS

S-GWeNodeBeNodeB

SGSN

Figure 2-20 Globally Unique Temporary Identity (GUTI)


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GUMMEI is constructed from MCC, MNC and MME Identifier (MMEI).

In turn the MMEI is constructed from an MME Group ID (MMEGI) and an

MME Code (MMEC).

For paging, the mobile is paged with the S-TMSI. The S-TMSI is constructed

from the MMEC and the M-TMSI.

The operator needs to ensure that the MMEC is unique within the MME pool

area and, if overlapping pool areas are in use, unique within the area of

overlapping MME pools.

The GUTI is used to support subscriber identity confidentiality, and, in the

shortened S-TMSI form, to enable more efficient radio signalling procedures.

GUMMEI

MCC MNC MMEGI MMEC M-TMSI

MMEI

S-TMSI

Figure 2-21 GUTI structure

TAITAITAITAI

The Tracking Area Identity (TAI) is the identity used to identify TrackingAreas (TAs). The Tracking Area Identity is constructed from the MCC, MNC

and Tracking Area Code (TAC).

MCC MNC TAC

Figure 2-22 Tracking Area Identity (TAI)


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IntroductionIntroductionIntroductionIntroductionMultiple access in telecommunications systems refers to techniques that

enable multiple users to share limited network resources efficiently. A

telecommunications network has finite resources that are usually defined in

terms of bandwidth. When there is more than one user to access such limited

bandwidth, an multiple access scheme must be put in place to control the

share of bandwidth among multiple users so that everyone can use services

provided by the network and to make sure that no single user spends all

available resources.

From a very early stage of modern communications, researchers have been

working on finding the best multiple access scheme to follow the above

simple rule of resource sharing among multiple users. Very visible and

fundamental ways of sharing bandwidth, frequency and time separation, were

chosen as the beginning of multiple access generation.

FDMAFDMAFDMAFDMA

In the first multiple access communications systems, the available frequency

spectrum for a given system was divided into some frequency channels where

each channel occupies a portion of total available bandwidth and is given to a

single user. Multiple users using separate frequency channels could access the

same system without significant interference from other users concurrently

operating in the system. It is the simplest way of having an scheme in a multi-

user system, and it is referred to as Frequency Division Multiple Access

(FDMA).

time

frequencyf1 f2 f3 f4 f5 f6 f7

Figure 3-1 Frequency Division Multiple Access


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TDMATDMATDMATDMA

With the same concept, Time Division Multiple Access (TDMA) schemes

came to start the digital communications era by dividing the time axis into

portions or time slots, each assigned to a single user to transmit data

information. TDMA schemes thus came into effect through frame and

multiframe concepts: a user could send a large data file within time slots of

periodical frames. Data from a single user always sits in the same time slot

position of a frame, so at the receiver all information from that portion can be

collected and aggregated to shape the original transmitted packet. TDMA,

together with Pulse Code Modulation (PCM), has become an effective way of

sharing the available system resources not only in wireless communications

but in wired communications since then. TDMA has kept its dominance in

wired and wireless systems for many years. Many cellular standards such asthe GSM and GPRS adopted TDMA as their multiple access scheme.

time

frequency

TS 1

TS 2

TS 3

TS 4

Figure 3-2 Time Division Multiple Access

As is clear from the above simple review, in both FDMA and TDMA

techniques the number of channels or time slots is fixed for a given system,

and a single channel is allocated to a single user for the whole period of

communications.

This was not only a concept to have a simple multiple access technique in the

early stage of modern telecommunications, but was based on the dominantservice in mind at the time, voice communications. Having a fixed channel or

time slot assignment could guarantee the service quality for real-time and

constant-bit-rate voice telephony, the main service at that time. By increasing

the number of services from simple voice to more burst data transmissions,

fixed channel assignment has shown its lack of efficiency in utilizing the

scarce spectrum, especially with the exponential increase in number of users.

Researchers started to think of more dynamic channel assignment forms of

TDMA and FDMA that could allocate a channel only when the user wants to

transmit data. While many dynamic channel assignment multiple access

schemes have been invented since then, the fixed upper limit on number of


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users in a TDMA or FDMA system has created a demand for new multiple

access schemes with fewer limitations, particularly for mobile

communications.

CDMACDMACDMACDMA

With this idea in mind, Code Division Multiple Access (CDMA) schemes

based on spread spectrum technology started to come into commercial

systems, different from their original environment mainly in military

applications. In a CDMA system the relatively narrowband users information

is spread into a much wider spectrum using a high clock chip rate. Using

different uncorrelated codes by each user, it is possible to send multiple users

information on the same frequency spectrum without significant difficulty in

detecting the desired signal at the receiver side as long as the correctspreading code is known to the receiver. The signal from each user will have

very low power and be seen by others as background noise. Therefore, as long

as the total power of noise (i.e., multi-user interference) is less than a

threshold, it is possible to detect the desired signal using the spreading code

used to encode the signal at the transmitter. Using spread spectrum

techniques, CDMA has become a dynamic channel allocation multiple access

scheme that has no rigid channel allocation limitation for individual users.

The number of users is also not fixed as in TDMA and FDMA, and a new

user can be added to the system at any time. The upper limit for the maximum

number of simultaneous users in the system using the same frequency

spectrum is decided by the effect of total power of multi-user interference;

thus, adding new users to a CDMA system will only cause graceful

degradation of signal quality. CDMA is thus seen as an multiple access

scheme that has no fixed maximum number of users as opposed to TDMA

and FDMA schemes.

frequency

time

code

code 1

code 2

code 3

code 4

Figure 3-3 Code Division Multiple Access


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With the ex

129454451 Lelliwa LTE Technology

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