0e966What is LTE I.doc

7/28/2019 0e966What is LTE I.doc

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What is LTE--I

LTE (Long Term Evolution) is the project name of a newhigh performance air interface for cellular mobilecommunication systems.

It is the last step toward the 4th generation (4G) of radio

technologies designed to increase the capacity and speedof mobile telephone networks.

Current generation of mobile telecommunication networks

are collectively known as 3G, LTE is marketed as 4G.

According to 3GPP, a set of high level requirements wasidentified

Reduced cost per bit

Increased service provisioning more services at lowercost with better user experience

Flexibility of use of existing and new frequency bands

Simplified architecture, Open interfaces

Allow for reasonable terminal power consumption


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Roadmap to 4G

Although it uses a different form of radio ,there are

major step changes between LTE and its 3Gpredecessors.

It is nevertheless looked interface, using OFDMA /

SC-FDMA instead of CDMA.

There are many similarities with the earlier forms of

3G architecture and there is scope for much re-use.

LTE can be seen for providing a further evolution offunctionality, increased speeds and generalimproved performance.


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Table 1: LTE and 3G/3.5G Specification (from NTTdocomo Press Release)

3G WCDMA

(R99)

3.5G HSPA LTE

Frequency Common frequency assigned for 3G

Bandwidth 5MHz 5/10/20MHz

Radio Access DS-CDMA DL: OFDMA

UL: SC-FDMA

Uplink Peak

Rate

384kbps 5.7Mbps >50Mbps

Downlink Peak

Rate

384kbps 14Mbps >100Mbps

LTE has introduced a number of new technologies

when compared to the previous cellular systems.

They enable LTE to be able to operate moreefficiently with respect to the use of spectrum, andalso to provide the much higher data rates that arebeing required.

OFDM

OFDM technology has been incorporated into LTE

because it enables high data bandwidths to be

transmitted efficiently while still providing a highdegree of resilience to reflections and interference.


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MIMO (Multiple Input Multiple Output)

One of the main problems that previous

telecommunications systems have encountered isthat of multiple signals arising from the many

reflections that are encountered. By using MIMO, these additional signal paths can

be used to advantage and are able to be used toincrease the throughput.

SAE (System Architecture Evolution)

With the very high data rate and low latency

requirements for 3G LTE, it is necessary to evolvethe system architecture to enable the improved

performance to be achieved.

One change is that a number of the functions

previously handled by the core network have beentransferred out to the periphery.

Essentially this provides a much "flatter" form of

network architecture. In this way latency times canbe reduced and data can be transmitted muchfaster.

Requirement for LTE

The following target requirements were agreed amongoperators and vendors at the project to define theevolution of 3G networks started.

Peak data rate instantaneous downlink peak data

rate of 100 Mbps within a 20 MHz downlinkspectrum allocation (5 bps/Hz)


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Instantaneous uplink peak data rate of 50 Mbps (2.5

bps/Hz) within a 20MHz uplink spectrum allocationControl-plane latency

Transition time of less than 100 ms from a camped

state, such as Release 6 Idle Mode, to an activestate such as Release 6 CELL_DCH

Transition time of less than 50 ms between a

dormant state such as Release 6 CELL_PCH and anactive state such as Release 6 CELL_DCHControl-plane capacity

At least 200 users per cell should be supported in

the active state for spectrum allocations up to 5MHz User-plane latency

Less than 5 ms in unload condition (i.e., single user

with single data stream) for small IP packet Userthroughput

Downlink: average user throughput per MHz, 3 to 4

times Release 6 HSDPA

Uplink: average user throughput per MHz, 2 to 3

times Release 6 Enhanced UplinkSpectrum efficiency

Downlink: In a loaded network, target for spectrum

efficiency (bits/sec/Hz/site), 3 to 4 times Release 6HSDPA

Uplink: In a loaded network, target for spectrum

efficiency (bits/sec/Hz/site), 2 to 3 times Release 6Enhanced Uplink Mobility

E-UTRAN should be optimized for low mobile speed

from 0 to 15 km/h

Higher mobile speed between 15 and 120 km/h should

be supported with high performance

Mobility across the cellular network shall be

maintained at speeds from 120 km/h to 350 km/h (or


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even up to 500 km/h depending on the frequencyband)Coverage

Throughput, spectrum efficiency and mobility targets

above should be met for 5 km cells, and with a slightdegradation for 30 km cells. Cells range up to 100 kmshould not be precluded.

Multimedia Broadcast Multicast Service (MBMS)

While reducing terminal complexity: same

modulation, coding, multiple access approaches and

UE bandwidth than for unicast operation. Provision of simultaneous dedicated voice and MBMS

services to the user.

Available for paired and unpaired spectrum

arrangements.Spectrum flexibility

E-UTRA shall operate in spectrum allocations of

different sizes, including 1.25 MHz, 1.6 MHz, 2.5 MHz,

5 MHz, 10 MHz, 15 MHz and 20 MHz in both the uplinkand downlink. Operation in paired and unpairedspectrum shall be supported

The system shall be able to support content delivery

over an aggregation of resources including RadioBand Resources (as well as power, adaptivescheduling, etc) in the same and different bands, inboth uplink and downlink and in both adjacent and

non-adjacent channel arrangements. A "Radio Band Resource" is defined as all spectrum

available to an operator


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Co-existence and Inter-working with 3GPP Radio AccessTechnology (RAT)

Co-existence in the same geographical area and co-

location with GERAN/UTRAN on adjacent channels.

E-UTRAN terminals supporting also UTRAN and/or

GERAN operation should be able to supportmeasurement of, and handover from and to, both3GPP UTRAN and 3GPP GERAN.

The interruption time during a handover of real-time

services between E-UTRAN and UTRAN (or GERAN)should be less than 300 msec.

Architecture and migration

Single E-UTRAN architecture:- The E-UTRAN architecture shall be packet based,

although provision should be made to supportsystems supporting real-time and conversationalclass traffic

E-UTRAN architecture shall minimize the presence of

"single points of failure"

E-UTRAN architecture shall support an end-to-end

QoS

Backhaul communication protocols should be

optimizedRadio Resource Management requirements

Enhanced support for end to end QoS

Efficient support for transmission of higher layers

Support of load sharing and policy management

across different Radio Access Technologies

Complexity

Minimize the number of options

No redundant mandatory features


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We can find significantly higher data rate (50-

100Mbps) and faster connection times as mostremarkable requirements relative to 3G/3.5G.

In order to achieve the high data rate, 3GPP

decided to use OFDMA and MIMO together for radioaccess technology.

LTE also introduce scheduling for shared channel

data, HARQ and AMC (Adaptive Modulation andCoding).

E-UTRAN Architecture

In order to achieve the requirements in previous

section, the LTE radio access network E-UTRANarchitecture is improved dynamically from 3G/3.5Gradio access network UTRAN.

It has been changed to be flat from legacy

hierarchy mobile network architecture.

The functions of eNB in E-UTRAN include not onlybase station (NodeB) to terminate radio interfacebut also Radio Network Controller (RNC) to manageradio resource.


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According to 3GPP TR 25.912, E-UTRAN is described asfollows:-

The evolved UTRAN consists of eNB, providing the

evolved UTRAN U-plane and C-plane protocol

terminations towards the UE.

The eNBs are interconnected with each other by

means of the X2 interfaces. It is assumed that therealways exist an X2 interface between the eNBs that

need to communicate with each other, e.g., forsupport of handover of UEs in LTE_ACTIVE.

The eNBs are also connected by means of the S1

interface to the EPC (Evolved Packet Core). The S1interface supports a many-to-many relation

between aGWs and eNBs.

E-UTRAN Architecture


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C-plane protocol stack on Uu and S1-C interfaces is shownin Figure below:-

C-plane Protocol Stack on Uu (UE/eNB) and S1-C(eNB/MME)

C-plane protocol stack on Uu and X2-C interfaces is shownin Figure below:-

C-plane Protocol Stack on X2-C (eNB/eNB)


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U-plane protocol stack on Uu and S1-U interfaces is shownin Figure bolow:-

U-plane Protocol Stack on Uu (UE/eNB) and S1-U

(eNB/MME)

C-plane protocol stack on Uu and X2-U interfaces is shown in Figure

below:-

U-plane Protocol Stack between eNB/eNB


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SAE Technology

System Architecture Evolution (SAE) is the network

architecture and designed to simplify the network toother IP based communications network.

SAE uses an eNB and Access Gateway (aGW) and

removes the RNC and SGSN from the equivalent 3Gnetwork architecture, to make a simpler mobile network

. This allows the network to be built as an All-IP based

network architecture.

SAE also includes entities to allow full inter-working

with other related wireless technology (WCDMA,WiMAX, WLAN, etc.).

These entities can specifically manage and permit the non-

3GPP technologies to interface directly into the network and

be managed from within the same network.


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SAE (System Architecture Evolution) and LTE Network


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LTE NetworkMME : MOBILE MANAGEMENT ENTITYHPCRF: HOME POLICY &CHARGING RULE FUNCTION

VPCRF: VISITING POLICV &CHARGING PULEVFUNCTION

PCEF: POLICY &CHARGING ENFORCEMENT FUNCTION

PCRF:POLICY &CHARGING RULE FUNCTION

BBERF: :BEARER BINDING &EVENT REPORTING FUNCTIONSPR: SUBSCRIPTION PROFILE REPOSITORYHSGW : HOME SUB. GATEWAYAAA SERVER: AUTHENTICATION,AUTHORIZATION AND

ACCOUNTING SERVER

EPC : EVOLVED PACKET CORE


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Bearer Services in LTE/SAE Network

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