00_nsn_lte_presentation_planningteam_may12-2013.pdf

8/20/2019 00_NSN_LTE_Presentation_PlanningTeam_May12-2013.pdf

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1 © Nokia Siemens Networks

LTE fundamentals and system architect

Ahmad TalaatNSN Saudi - NPO


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Contents

• LTE Drivers

• LTE Main Requirements

• Network Architecture Evolution

• Key Features and Basics

• LTE Network Architecture• Highlight on some Important NSN Features


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The way to the Long-Term Evolution (LTE): a 3GPP driveninitiative

•LTE is 3GPP system for the years 2010 to 2020 &beyond.

•It shall especially compete with WiMAX 802.16e/m

•It must keep the support for high & highest

mobility users like in GSM/UMTS networks

•The architectural changes are big compared toUMTS

•LTE commercial launch has started early 2010.


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LTE Drivers

Wireline Evolution: pushes higher data

rates

Wireless Dataextensively used:

Pushes more capacity

Flat Rate pricing:

pushes cost efficiency

Other Wirelesstechnologies:

Competition pushes newcapabilities

Driving to clearLTE Targets


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What are the LTE challenges?

• Best price, transparent flat rate• Full Internet

• Click-bang responsiveness

• reduce cost per bit• provide high data rate

• provide low latency

The Users’ expectation… ..leads to the operator’s challenges

Price per Mbyte has to be reducedto remain profitable

User experience will have animpact on ARPU

LTE: lower cost per bit and improved end user experience

UMTS HSPA I-HSPA LTE

Cost per MByte

HSPA LTE HSPA LTE

Throughput Latency


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Reduction of network cost is necessary to remainprofitable

Source: Light Reading (adapted)

Traffic

Revenue

Revenues and Trafficdecoupled

T r a f f i c v o l u m e

€ / b

i t

Time

Profitability

Network

cost

Voicedominated

Datadominated


7/517 © Nokia Siemens Networks

Contents

• LTE Drivers




• LTE Network Architecture• Highlight on some Important NSN Features



LTE = Long Term Evolution

• Peak data rates of 303Mbps / 75 Mbps

• Low latency 10-20 ms

Enhanced consumer experience

• Scalable bandwidth of1.4 – 20 MHz

Easy to introduce on anyfrequency band

• OFDM technology

• Flat, scalable IP basedarchitecture

Decreased cost / GB

• Next step for

GSM/WCDMA/HSPAand CDMA A true global roaming technology



Schedule for 3GPP releases

• Next step for

GSM/WCDMA/HSPAand cdma2000 A true global roaming technology

year

3GPP Rel. 99/4 Rel. 5 Rel. 6 Rel. 7

2007200520032000 2008

HSDPA

IMS

HSUPA

MBMS

WLAN IW

HSPA+

LTE Studies

Specification

2009

• LTE have been developed by the same standardization organization. The target has beensimple multimode implementation and backwards compatibility.

• HSPA and LTE have in common: – Sampling rate using the same clocking frequency

– Same kind of Turbo coding

• The harmonization of these parameters is important as sampling and Turbo decoding aretypically done on hardware due to high processing requirements.

• WiMAX and LTE do not have such harmonization.

Rel. 8

LTE & EPC

Rel. 9

LTE-A

studies

LTE-A: LTE-Advanced

Rel. 10

LTE-AUMTS/

WCDMA

2011



Comparison of Throughput and Latency (1/2)

HSPA R6

Max. peak data rate

M b p s

Evolved HSPA(Rel. 7/8, 2x2MIMO)

LTE 2x20 MHz(2x2 MIMO)

LTE 2x20MHz (4x4MIMO)

Downlink

Uplink

350

300

250

200

150

100

50

0

HSPAevo

(Rel8)

LTE

* Server near RAN

Latency (Rountrip delay)*

DSL (~20-50 ms, depending on operator)

0 20 40 60 80 100 120 140 160 180 200

GSM/EDGE

HSPARel6

min max

ms

Enhanced consumer experience:- drives subscriber uptake

- allow for new applications

- provide additional revenue streams

• Peak data rates of303 Mbps / 75 Mbps

• Low latency 10-20ms



Scalable bandwidth

• Scalable bandwidthof 1.4 – 20 MHz

Easy to introduce on anyfrequency band: FrequencyRefarming

(Cost efficient deployment on lowerfrequency bands supported)

Scalable Bandwidth

Urban

2006 2008 2010 2012 2014 2016 2018 2020

Rural

2006 2008 2010 2012 2014 2016 2018 2020

or

2.6 GHz

2.1 GHz

2.6 GHz

2.1 GHz

LTE

UMTS

UMTS

LTE

900 MHz

900 MHz GSM

or

GSM UMTS

LTE

LTE

LTE



0.0

0.2

0.40.6

0.8

1.0

1.2

1.4

1.6

1.8

2.0

HSPA R6 HSPA R6 +

UE

equalizer

HSPA R7 WiMAX LTE R8

b p s / H z / c e l l

DownlinkUplink

Increased Spectral Efficiency

• All cases assume 2-antenna terminal reception

• HSPA R7, WiMAX and LTE assume 2-antenna BTS transmission (2x2 MIMO)

ITU contribution from

WiMAX Forum shows

DL 1.3 & UL 0.8 bps/Hz/cell

Reference:

- HSPA R6 and LTE R8 from 3GPP R1-071960

- HSPA R6 equalizer from 3GPP R1-063335

- HSPA R7 and WiMAX from NSN/Nokia

simulations

• OFDMA technologyincreases Spectral

efficiency

LTE efficiency is 3 x HSPA R6 indownlinkHSPA R7 and WiMAX have Similar

Spectral Efficiency


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Reduced Network Complexity

• Flat, scalable IP basedarchitecture Flat Architecture: 2 nodes architectureIP based Interfaces

Access Core Control

Evolved Node B Gateway

IMS HLR/HSS

Flat, IP based architecture

Internet

MME


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LTE/SAE Requirements Summary

1. Simplify the RAN:

- Reduce the number of different types of RAN nodes, and their complexity.

- Minimize the number of RAN interface types.2. Increase throughput: Peak data rates of UL/DL 50/100 Mbps

3. Reduce latency (prerequisite for CS replacement).

4. Improve spectrum efficiency: Capacity 2-4 x higher than with Release 6 HSPA

5. Frequency flexibility & bandwidth scalability: Frequency Refarming

6. Migrate to a PS only domain in the core network: CSFB for initial phase

7. Provide efficient support for a variety of different services. Traditional CS services

will be supported via VoIP, etc: EPS bearers for IMS based Voice

8. Minimise the presence of single points of failure in the network above the eNBs S1-

Flex interface

9. Support for inter-working with existing 3G system & non-3GPP specified systems.

10. Operation in FDD & TDD modes

11. Improved terminal power efficiency

A more detailed list of the requirements and objectives for LTE can be found in TR 25.913.


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Contents

• LTE Drivers




• LTE Network Architecture

• Highlight on some Important NSN Features


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NSN Network Architecture Evolution (1/4)

Node B RNC SGSN GGSNInternet

3GPP Rel 6 / HSPA

User plane

Control Plane

• Original 3G architecture.• 2 nodes in the RAN.

• 2 nodes in the PS Core Network.

• Every Node introduces additional delay.

• Common path for User plane and Control plane data.• Air interface based on WCDMA.

• RAN interfaces based on ATM.

• Option for Iu-PS interface to be based on IP.


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Direct tunnel

3GPP Rel 7 / HSPA

Internet

Node B RNC

SGSN

GGSN

User plane

Control Plane

• Separated path for Control Plane and User Plane data in the PSCore Network.

• Direct GTP tunnel from the GGSN to the RNC for User plane data:simplifies the Core Network and reduces Signalling.

• First step towards a flat network Architecture.

• 30% core network OPEX and CAPEX savings with Direct Tunnel.

• The SGSN still controls traffic plane handling, performs session andmobility management, and manages paging.

• Still 2 nodes in the RAN.


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Direct tunnel

3GPP Rel 7 / Internet HSPA

Internet

Node B

SGSN

GGSN

Node B

(RNC Funct.)User plane

Control Plane

• I-HSPA introduces the first true flat architecture to WCDMA.• Standardized in 3GPP Release 7 as: “Direct Tunnel with collapsedRNC”.

• Most part of the RNC functionalities are moved to the Node B.

• Direct Tunnels runs now from the GGSN to the Node B.

• Solution for cost-efficient broadband wireless access.

• Improves the delay performance (less node in RAN).

• Deployable with existing NSN WCDMA base stations.

• Transmission savings


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Direct tunnel

3GPP Rel 8 / LTE

Internet

Evolved Node B

MME

SAE GW

• LTE takes the same Flat architecture from Internet HSPA.• Air interface based on OFDMA.

• All-IP network.

• New spectrum allocation (i.e 2600 MHz band)

• Possibility to reuse spectrum (i.e. 900 MHZ)

User plane

Control Plane


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NSN Network Architecture Evolution - Summary

Node B RNC SGSN GGSN

Internet

3GPP Rel 6 / HSPA

Direct tunnel

3GPP Rel 7 / HSPA

Internet

Node BRNC

SGSN

GGSN

Direct tunnel

3GPP Rel 7 / Internet HSPA

Internet

Node B

SGSN

GGSN

Node B

(RNC Funct.)

Direct tunnel

3GPP Rel 8 / LTE

Internet

Evolved Node B

MME

SAE GW


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Contents

• LTE Drivers







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Evolved Packet Core (EPC)LTE Radio

Access Network(EUTRAN)

MME

Serving

GWPDN

GW

PacketData

Network

SAE-GW

eNode-B

LTE Radio Interface Key Features

LTE Radio Interface Key Features

• Retransmission Handling (HARQ/ARQ)

• Spectrum Flexibility• FDD & TDD modes

• Multi-Antenna Transmission

• Frequency and time Domain scheduling

• Uplink (UL) Power Control


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MME

Serving

GWPDN

GW

PacketData

Network

SAE-GW

eNode-B

EUTRAN Key Features

EUTRAN Key Features:

• Evolved NodeB

• IP transport layer

• UL/DL resource scheduling

• QoS Awareness

• Self-configuration


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MME

Serving

GWPDN

GW

PacketData

Network

SAE-GW

eNode-B

EPC Key Features

EPC Key Features:

• IP transport layer

• QoS Awareness

• Packet Switched Domain only

• 3GPP (GTP) or IETF (MIPv6) option

• Prepare to connect to non-3GPP access networks


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TDMA

f

t

f

• Time Division

FDMA

f

f

t

• Frequency Division

CDMA

f

t

f

• Code Division

OFDMA

f

f

t

• Frequency Division

• Orthogonal subcarriers

Multiple Access Methods User 1 User 2 User 3 User ..

OFDM is the state-of-the-art and most efficient and robust air interface


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The Rectangular Pulse

Advantages:

+ Simple to implement: there is no complexfilter system required to detect such pulses

and to generate them.+ The pulse has a clearly defined duration.This is a major advantage in case of multi-path propagation environments as it simplifieshandling of inter-symbol interference.

Disadvantage:

- it allocates a quite huge spectrum. Howeverthe spectral power density has null pointsexactly at multiples of the frequency fs = 1/Ts.This will be important in OFDM.

time

a m p l i t u d e

Ts f s 1

T s

Time Domain

frequency f/f s

s p e c t r a l p o w e r d e n s i t y

Frequency Domain

f s

Fourier

Transform

InverseFourier

Transform


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Air Interface - OFDM Basics

• Data is sent in parallel across the set of subcarriers, each subcarrier only

transports a part of the whole transmission• The throughput is the sum of the data rates of each individual (or used)

subcarriers while the power is distributed to all used subcarriers

• FFT ( Fast Fourier Transform) is used to create the orthogonal subcarriers. Thenumber of subcarriers is determined by the FFT size ( by the bandwidth)

Power

frequency

bandwidth


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The OFDM Signal


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OFDMA Parameters in LTE

• Channel bandwidth: DL bandwidths ranging from 1.4 MHz to 20 MHz

• Data subcarriers: the number of data subcarriers varies with thebandwidth

– 72 for 1.4 MHz to 1200 for 20 MHz


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Resource Block and Resource Element

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

0 1 2 3 4 5 6 0 1 2 3 4 5 6

Subcarrier 1

Subcarrier 12

1 8 0 K H z

1 slot 1 slot

1 ms subframe

ResourceElement

• Physical Resource Block PBR or Resource Block RB:

– 12 subcarriers in frequency domain x 1 slot period in time domain

– Capacity allocation based on Resource Blocks

Resource Element RE: – 1 subcarrier x 1 symbol period

– theoretical min. capacity allocation unit

– 1 RE is the equivalent of 1 modulationsymbol on a subcarrier, i.e. 2 bits(QPSK), 4 bits (16QAM), 6 bits (64QAM).


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Physical Resource Blocks

....

12 subcarriers

Time

Frequency

0.5 ms slot

1 ms subframe

or TTI

Resource

block

During each TTI,

resource blocks for

different UEs arescheduled in the

eNodeB

• In both the DL & UL direction, data isallocated to users in terms of

resource blocks (RBs).

• a RB consists of 12 consecutivesubcarriers in the frequency domain,

reserved for the duration of 0.5 ms

slot.• The smallest resource unit a

scheduler can assign to a user is a

scheduling block which consists of

two consecutive resource blocks


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LTE Channel Options

Bandwidth options: 1.4, 1.6, 3, 3.2, 5, 10, 15 and 20 MHz

Subcarriers in frequency domain (15 kHz or 7.5 kHz subcarrier spacing)

Channel bandwidth

(MHz)

Number of

subcarriers

Number of resource

blocks

1.4

72

6

3

180

15

5

300

25

10

600

50

15

900

75

20

1200

100


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LTE RRM: Scheduling

• Motivation

– Bad channel condition avoidance

OFDMA

The part of total available

channel experiencing badchannel condition (fading)

can be avoided during

allocation procedure.

CDMA

Single Carrier transmission

does not allow to allocate

only particular frequency

parts. Every fading gap

effects the data.


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Contents

• LTE Drivers

• LTE Main Requirements• Network Architecture Evolution




N k A hi E l i


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Network Architecture Evolution

SAE GWGGSN

SGSN

RNC

Node B

(NB)

Direct tunnel

GGSN

SGSN

I-HSPA

MME/SGSN

HSPA R7 HSPA R7 LTE R8

Node B +

RNC

Functionality

Evolved

Node B

(eNB)

GGSN

SGSN

RNC

Node B

(NB)

HSPA

HSPA R6

LTE

User plane

Control Plane

• Flat architecture: single network element in userplane in radio network and core network

E l d P k t S t (EPS) A hit t S b t


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Evolved Packet System (EPS) Architecture - Subsystems

• The EPS architecture goal is to optimize the system for packet data transfer.

• There are no circuit switched components. The EPS architecture is made up of: – EPC: Evolved Packet Core, also referred as SAE

– eUTRAN: Radio Access Network, also referred as LTE

LTE or eUTRAN SAE or EPC

EPS Architecture

• EPC provides access toexternal packet IP networks and

performs a number of CN

related functions (e.g. QoS,

security, mobility and terminal

context management) for idle

and active terminals

• eUTRAN performs all radiointerface related functions

LTE/SAE Network Elements


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LTE/SAE Network Elements

Main references to architecture in 3GPP specs.: TS23.401,TS23.402,TS36.300

LTE-UE

Evolved UTRAN (E-UTRAN)

MME S10

S6a

Serving

Gateway

S1-U

S11

PDN

Gateway

PDN

Evolved Packet Core (EPC)

PCRF

S7 Rx+

SGiS5/S8

Evolved Node B

(eNB)

X2

LTE-Uu

HSS

Mobility

Management

Entity Policy &

Charging Rule

Function

SAE

Gateway

eNB

C t t


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Contents

• LTE Drivers

• LTE Main Requirements• Network Architecture Evolution




UL Ph i l R Bl k DRS & SRS


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UL Physical Resource Block: DRS & SRS

....

12 subcarriers

Time

0.5 ms slot

1 ms subframe

or TTI

Frequency

Sounding Reference

Signal on last OFDM

symbol of 1 subframe;

Periodic or aperiodic

transmission

Demodulation

Reference Signal in

subframes that carry

PUSCH

• The Demodulation ReferenceSignal is transmitted in the third

SC-FDMA symbol (counting from

zero) in all resource blocks

allocated to the PUSCH carryingthe user data.

• This signal is needed for channelestimation, which in turn is

essential for coherent

demodulation of the UL signal in

the eNodeB.

• The Sounding Reference SignalSRS provides UL channel quality

information as a basis for

scheduling decisions in the base

station. This signal is distributed inthe last SC-FDMA symbol of

subframes that carry neither

PUSCH nor PUCCH data. [SRS is

always disabled in FDD RL30 and

before.]PUCCH: Physical UL Control Channel

RL30U li k S h d l


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• Flexi eNodeB takes into account the noise and interference measurements together withthe UE Tx power density (= UE TX power per PRB) when allocating PRBs in thefrequency domain

• Cell edge users are assigned to frequency sub-bands with low measured inter-cellinterference

• Up to 10% gain for cell edge users in low and medium loaded networks

• Easier to implement than channel aware scheduling (no sounding reference signal used)

Improvement in UL coverage by optimizing the cell edge performance

eNode Bmeasuredinterference

subband with lowinterference

subband with highinterference

subband with mediuminterference

PRBs

Feature ID(s): LTE619

RL30Uplink SchedulerIAS: Interference Aware Scheduler UL

High Tx power density indicates

cell edge users / strong interferers

LTE46 UL Ch l A S h d li

RL40


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LTE46, UL Channel Aware Scheduling

• Channel Unaware Scheduling (CUS)

– random allocation of PRBs => averaging of inter-cell interference

– simple and robust, no UL channel sounding required

– no FDPS gain

• Interference Aware Scheduling (IAS, LTE619)

– rudimentary interference reduction via coarse segmentation

– scheduling criterion based on Tx power density =>Tx power per PRB

– no UL channel sounding required

– lower FDPS gain than CAS, LTE46

• Channel Aware Scheduling (CAS, LTE46)

– very similar implementation in RL15 and RL40

– sophisticated SRS- and PUSCH-based PRB allocation according to UEspecific channel state information (CSI)

– UL channel sounding required

– FDPS gain (low for a high # of PRBs allocated to a specific UE )

RL40

LTE RRM: Connection Mobility Control


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LTE RRM: Connection Mobility ControlHandover Types

• Intra-RAT handover

– Intra eNodeB and Inter eNodeB handover – Above handovers can also be Inter-frequency handovers (RL20) i.e. to support different

frequency bands and deployments within one frequency band but with different center

frequencies

– Data forwarding over X2 for inter eNodeB HO

– HO via S1 interface (RL20): HO in case of no X2 interface configured between servingeNB and target eNB

• Inter-RAT handover

– LTE to WCDMA: RL30

– WCDMA to LTE: RL40

– LTE to CDMA2000: RL40 (CDMA2000 to LTE not assigned)

– LTE GSM and GSM LTE: not assigned


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Intra frequency handover via X2

• Basic Mobility Feature

• Event triggered handover basedon DL measurements (ref.

signals)

• Network evaluated HO decision• Operator configurable

thresholds for

• coverage based &• best cell based handover

• Data forwarding via X2• Radio Admission Control (RAC)gives priority to HO related

access over other scenarios S1

S1 X2

MMES-GW

P-GW


A reliable and lossless mobility

RL20


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Intra LTE Handover via S1

Extended mobility option to X2 handover

• Handover in case of

• no X2 interface between eNodeBs, e.g. multi-vendor scenarios

• eNodeBs connected to different CN elements

• Operator configurable thresholds for

• coverage based (A5) and• best cell based (A3) handover

• DL Data forwarding via S1


RL20

• Admission Control gives priority to HO

related access over other scenarios• Blacklists

RL20


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Inter Frequency Handover

Multi-band mobility

• Network controlled

• Event triggered based on DLmeasurement RSRP and RSRQ

• Inter frequency measurementstriggered by events A1/A2

• Operator configurable thresholds for

coverage based (A5),

best cell based (A3) handover

• Service continuity for LTE deployment

in different frequency bands as wellas for LTE deployments within onefrequency band but with differentcenter frequencies

• Blacklists


RL20

RL30


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Inter RAT Handover to WCDMA

• Coverage based inter-RAT PS handover• Only for multimode devices supporting

LTE and WCDMA

• Event triggered handover based on DLmeasurement RSRP (reference signalreceived power)

• Operator configurable RSRP threshold

• Network evaluated HO decision

• Target cells are operator configurable

• An ANR functionality may be applied

optionally


• Blacklisting

• eNB initiates handover via EPC

RL30

CC GSRL30


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eNACC to GSMNetwork Assisted Cell Change to GSM

Service continuity to GSM

• Network change from LTE to GSM inRRC Connected Mode when LTE

coverage (RSRP) is ending

• Prior to actual reselection process the

measurements of 2G network aretriggered

• Only applicable for NACC capabledevices

• Inter RAT measurements triggered byevents A1/A2

• Operator configurable handoverthreshold (event B2)

• Target cells for IRAT measurements canbe configured by the operator

• Blacklisting of target cells is supportedFeature ID(s): LTE442

RL30

LTE735: RRC Connection Reestablishment RL30


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LTE735: RRC Connection Reestablishment

• eNode B takes UE back to RRCCONNECTED

• UE initiated procedure

• Typical scenarios:

• Radio link failures (e.g. T310expires)

• Handover failure (e.g. T304expires)

• RRC connection reconfigurationfailure

Advanced failure handling

MMES-GW

UE reverts back to

source cell due to

handover failure

RL30

Automated Neighbor Relation (ANR) Configuration


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Automated Neighbor Relation (ANR) Configuration

• Neighbour relations are important as wrong neighbour definitions cause HOfailures and dropped calls

• Self configuration of relations avoids manual planning & maintenance

ANR covers 4 steps:

1) Neighbour cell discovery

2) Neighbour Site’s X2 transport configuration discovery (i.e. Neighbour Site IP@)

3) X2 Connection Set-up with neighbour cell configuration update

4) ANR Optimization

• The scope within ANR is to establish an X2 connection between source andtarget nodes and for that it is necessary that source eNB knows the target eNBIP@

• How the source eNB gets the IP@ differentiates the ANR features: – Central ANR (RL10)

– ANR (RL20)

– ANR- Fully UE based (RL30)

3GPP ANR Configuration Principle


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MME

3GPP ANR Configuration Principle

Site

eNB - A

Neighbor

Site

eNB - B

New cell

discovered

New cell

identified

by ECGI

CM

X2 Setup : IPsec, SCTP, X2-AP [site & cell info]

UE

connected

S1 : Request X2 Transport Configuration (ECGI)

S1: Request X2 Transport Configuration

relays

request

S1: Respond X2 Transport Configuration (IP@)

S1 : Respond X2 Transport Configuration (IP@)

CM

relays

response

Add Site & Cell

parameter of

eNB-A CM CM

Add Site & Cell

Parameter of

eNB-B

Neighbor Cell Tables in both eNB updated


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Thank You

00_nsn_lte_presentation_planningteam_may12-2013.pdf

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