LTE Permulaan

Confidential

© Nokia Siemens Networks

Soc Classification level

GDC Sharing Session Matrix : LTE Network Planning Optimization

LTE Fundamental

(Enabling)

LTE Radio

Planning

Principle

LTE

Optimization

Principle

LTE

Introduction

LTE Radio

Planning &

Optimization

Specialist

LTE KPI &

Counter

LTE RAN

Dim Link

Budget

LTE NetAct

Planning LTE Actix

LTE Nemo

Analyzer

LTE BTS

Site

Manager

LTE Atoll

Planning

LTE Emil

UMTS Fundamental

2G Fundamental

LTE

Parameter

Basic

Intermediate

Advanced

LTE NetAct

Optimizer

LTE

signaling

Confidential


Soc Classification level

LTE Introduction

Confidential


Summary

•LTE Overview

•LTE Network Architecture

•LTE Air Interface - DL Air Interface

• - UL Air Interface

• - Physical Layer

•LTE Connection Management

•LTE Mobility Management

Confidential


LTE Overview

Presentation / Author / Date

Confidential


3GPP UMTS Evolution

• LTE is the next step in mobile radio communications after HSPA

• Evolution driven by data rate and latency requirements


WCDMA

384 kbps DL

384 kbps UL

RTT ~150 ms

CS/PS

HSDPA/HSUPA

14.4 Mbps peak DL

5.7 Mbps peak UL

RTT <100/50 ms

PS

HSPA +

28 Mbps peak DL

11 Mbps peak UL

RTT < 30 ms (2ms TTI)

PS

EUTRA (LTE)

100 Mbps peak DL

50 Mbps peak UL

RTT ~10 ms

PS

3GPP Rel.99/4 3GPP Rel. 5/6 3GPP Rel. 7 3GPP Rel. 8

2003/4 2005/06 HSDPA 2007/08 HSUPA

2008/09 2009/10

UTRA evolution: WCDMA 5MHz UTRA Long Term Evolution: up to 20 MHz BW

E-UTRA: Evolved UMTS Terrestrial Radio Access

Confidential


What is New in LTE?

New radio transmission schemes:

OFDMA in downlink

SC-FDMA in uplink

MIMO Multiple Antenna Technology

New network architecture: flat architecture

More functionality in the base station (eNodeB)

Focus on packet switched domain

New radio protocol architecture:

Complexity reduction

Focus on shared channel operation, no dedicated channels anymore

Important for Radio Planning:

Frequency Reuse 1

No need for Frequency Planning

Importance of interference control

No need to define neighbour lists in LTE

LTE requires Physical Layer Cell Identity planning (504 physical layer cell IDs organised into 168 groups of 3)

Additional areas need to be planned like PRACH parameters, PUCCH and PDCCH capacity and UL Demodulation Reference Signal

Confidential


LTE Architecture Network Elements and Interfaces


Confidential


NSN Network Architecture Evolution - Summary

Node B RNC SGSN GGSN

Internet

3GPP Rel 6 / HSPA

Direct tunnel

3GPP Rel 7 / HSPA

Internet

Node B RNC

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

Confidential


LTE/EPC Network Elements


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

Evolved UTRAN (E-UTRAN)

MME S10

S6a

Serving

Gateway

S1-U

S11

PDN

Gateway

PDN

Evolved Packet Core (EPC)

PCRF

Gx Rx

SGi S5/S8

HSS

Mobility

Management

Entity Policy & Charging

Rule Function

S-GW /P-GW LTE-UE

Evolved Node B

(eNB)

X2

LTE-Uu

eNB

PDN: Packet Data Network

PCRF: Policy and Charging Rule Function

HSS: Home Subscriber Server (part of IMS)

Confidential


Evolved Node B (eNB)


Inter-cell RRM: HO, load balancing between cells

Radio Bearer Control: setup , modifications and

release of Radio Resources

Connection Mgt. Control: UE State Management,

MME-UE Connection

Radio Admission Control

eNode B Meas. collection and evaluation

Dynamic Resource Allocation (Scheduler)

eNB Main Functions

IP Header Compression/ de-compression

MME Selection at Attach of the UE

User Data Routing to the S-GW/ P-GW

Transmission of Paging Msg coming from MME

Transmission of Broadcast Info (e.g. System info,

MBMS)

• Only network element defined as part of eUTRAN

• Replaces the old Node B / RNC combination from 3G.

• Provides all radio management functions

• To enable efficient inter-cell radio management for cells not attached to the same eNB, there is a inter-eNB interface X2 specified. It will allow to coordinate inter-eNB handovers without direct involvement of EPC during this process.

Confidential


EPC Network Elements (1/2) MME: Mobility Management Entity

• Pure signalling entity inside the EPC:

– Signalling coordination for EPS bearer setup/release

• Subscriber attach/detach

• Tracking area updates

• Roaming Control

• Trigger and distribution of paging messages to UE

• Radio security control

• Authentication, integrity protection

Serving Gateway

• Manages the user data in the EPC

• Receives packet data from the eNodeB and sends packet data to it


HSS

eNB

MME

Serving

Gateway

S1-U

S1-MME

S11

S6a

Confidential


EPC Network Elements (2/2)

Packet Data Network Gateway

• Connection between EPC and a number of external data networks (comparable to GGSN in 2G/3G networks)

• IP Address Allocation for UE

• Packet Routing/Forwarding between

Serving GW and external Data Network

• Packet screening (firewall functionality)

Policy and Charging Rule Function

• Quality of Service (QoS) negotiation with the external PDN

• Charging Policy: How packets should be accounted

HSS: Home Subscriber Server

• Permanent and central subscriber database

• Stores mobility and service data for every subscriber

• Contains AuC (authentication center) functionality

MME

Serving

Gateway

S5/S8

PDN

Gateway

PDN SGi

PCRF

S7 Rx+

S11

HSS S6a

Confidential


LTE Radio Interface and the X2 Interface


LTE-Uu interface

• Air interface of LTE

• Based on OFDMA in DL and SC-FDMA in UL

• FDD and TDD duplex methods

• Scalable bandwidth 1.4MHz to currently 20 MHz

X2 interface

• Inter eNB interface

• X2AP: special signalling protocol

• Functionalities:

– In inter- eNB HO to facilitate handover and provide data forwarding.

– In RRM to provide e.g. load information to neighbouring eNBs to facilitate interference management

– Logical interface: It does not need direct site-to-site connection

(E)-RRC User PDUs User PDUs

PDCP

..

RLC

MAC

LTE-L1 (FDD/TDD-OFDMA/SC-FDMA)

TS 36.300

eNB

LTE-Uu

eNB

X2

User PDUs

GTP-U

UDP

IP

L1/L2

TS 36.424

X2-UP

(User Plane) X2-CP

(Control Plane)

X2-AP

SCTP

IP

L1/L2 TS 36.421

TS 36.422

TS 36.423

TS 36.421

TS 36.420

[currently also in TS 36.300 §20]

Confidential


Downlink Air Interface

OFDMA


LTE Air Interface

Confidential


OFDM Basics

• Transmits hundreds or even thousands of separately modulated radio signals using orthogonal subcarriers spread across a wideband channel


Orthogonality:

The peak (centre

frequency) of one

subcarrier …

…intercepts the

‘nulls’ of the

neighbouring

subcarriers

15 kHz in LTE: fixed

Total transmission bandwidth

Confidential


Cyclic Prefix (CP) and Guard Time


Note: CP represents an overhead

resulting in symbol rate reduction.

Having a CP reduces the

bandwidth efficiency but the

benefits in terms of minimising the

ISI compensate for it

t

total symbol time T(s)

Guard Time

T(g)

CP

T(g) Useful symbol

time T(b)

• Consists in copying the last part of a symbol shape for a duration of guard-time and attaching it in front of the symbol

• CP needs to be longer than the channel multipath delay spread

• A receiver typically uses the high correlation between the Cyclic Prefix (CP) and the last part of the following symbol to locate the start of the symbol and begin then with decoding

• 2 CP options in LTE:

– Normal CP: for cells with short multipath delay spread

– Extended CP: designed for use with cells having long delay profiles

Confidential


Doppler in OFDM and Loss of Orthogonality

• Doppler effect (shift): Change in frequency of a wave due to the relative motion of source and receiver

• Symbols are distorted in the time domain

Frequency shifts make symbol detection inaccurate

MCS schemes with high number of bits per subcarrier (high data rates) are not suitable for UEs moving at high speed

Doppler only impacts SINRs at the higher range i.e. > 20dB


It reduces orthogonality

• The frequency domain subcarriers are shifted causing inter-carrier interference (ICI)

• The nulls of interferers and peaks of signals will not coincide

ICI in the absence of orthogonality

Confidential


Resource Block

Channel Bandwidth (MHz) 1.4 3 5 10 15 20*(20 Mhz *

10% = 18 Mhz)

No. of Resource Blocks 6 15 25 50 (9000 khz /

180 Khz = 50)

75 100

Number of Subcarriers 72 180 12 * 15 =

180

300 600 12 * 50 =

600

900 1200

Occupied Bandwidth (MHz) 1.08 2.7 (15 khz * 180

= 2.7 Mhz)

4.5 9.0 (15 khz * 600

= 9 Mhz)

13.5 18.0*

Resource Block in the Frequency Domain

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

18

0 K

Hz

1 slot 1 slot

1 ms subframe

• Resource Block (RB):

12 subcarriers in frequency domain (180kHz) x 1 slot period in time domain (0.5ms)

• Capacity allocation is based on Resource Block

• 1 TTI = 1 ms

Resource

Element

Confidential


OFDMA Symbol

• OFDMA is an extension of OFDM technique to allow multiple user transmissions and it is used in other systems like Wi-Fi, DVB and WiMAX

• OFDMA Symbol is the Time period occupied by the modulation symbols on all subcarriers. Represents all the data being transferred in parallel at a point in time


• OFDM symbol duration including CP is

aprox. 71.4 µs (*)

– Long duration when compared with 3.69µs for GSM and 0.26µs for WCDMA allowing a good CP duration

Robust for mobile radio channel with the use of guard internal/cyclic prefix

– Symbol length without considering CP: 66.67µs (1/15kHz)

(*) normal CP

Confidential


OFDMA Parameters

• Frame duration: 10ms created from slots and subframes

• Subframe duration (TTI): 1 ms (composed of 2x0.5ms slots)

• Subcarrier spacing: Fixed to 15kHz (7.5 kHz defined for MBMS)

• Sampling Rate: Varies with the bandwidth but always factor or multiple of 3.84 to ensure compatibility with WCDMA by using common clocking


Frame Duration

Subcarrier Spacing

Sampling Rate (MHz)

Data Subcarriers

Symbols/slot

CP length

1.4MHz 3 MHz 5 MHz 10 MHz 15 MHz 20 MHz

10 ms

15 kHz

Normal CP=7, extended CP=6

Normal CP=4.69/5.12 μsec, extended CP= 16.67μsec

1.92 3.84 7.68 15.36 23.04 30.72

72 180 300 600 900 1200

Confidential


Uplink Air Interface

SC-FDMA


Confidential


SC-FDMA in UL

• Single Carrier Frequency Division Multiple Access: Transmission technique used for Uplink

• Variant of OFDM that reduces the PAPR:

– Combines the PAR of single-carrier system with the multipath resistance and flexible subcarrier frequency allocation offered by OFDM

– It can reduce the PAPR between 6…9dB compared to OFDMA

– TS36.201 and TS36.211 provide the mathematical description of the time domain representation of an SC-FDMA symbol.

• Reduced PAPR means lower RF hardware requirements (power amplifier)


SC

-FD

MA

OF

DM

A

Confidential


SC-FDMA and OFDMA Comparison (2/2)


Confidential


Uplink Air Interface Technology SC-FDMA

• User multiplexing in frequency domain, a user is allocated different bandwidths (multiples of 180kHz)

– In OFDMA the user multiplexing is in sub-carrier domain: user is allocated Resource Blocks

• One user is always continuous in frequency

• Smallest uplink bandwidth, 12 subcarriers: 180 kHz

– same for OFDMA in downlink


• Largest uplink bandwidth: 20 MHz

– same for OFDMA in downlink

– Terminals are required to be able to receive & transmit up to 20 MHz

Confidential


OFDMA and SC-FDMA vs. CDMA

• Larger bandwidths and frequency flexibility

– OFDM provides performance benefits over CDMA based system when the bandwidth

increases beyond 5 MHz

– OFDM makes it simpler to provide different bandwidths

• Frequency Domain Scheduling

– OFDM can take benefit of frequency domain scheduling which increases capacity up

to 50% compared to CDMA

• Reduced UE power consumption

– LTE uplink uses SC-FDMA which enables better power amplifier efficiency

• Simpler multi antenna operation

– MIMO is simpler to implement with OFDM than with CDMA

• Same multiple Access Techniques for FDD and TDD in LTE

– OFDMA in DL and SC-FDMA in UL. In WCDMA, TDD mode is different than FDD

although some harmonization was done e.g. chip rates and coding solutions


Confidential


Physical Layer Structure and Channels


Physical Layer

Confidential


Frame Structure (FDD)

• FDD Frame structure (also called Type 1 Frame) is common to both uplink and downlink.

• Divided into 20 x 0.5ms slots

– Structure has been designed to facilitate short round trip time


10 ms frame

0.5 ms slot

s0 s1 s2 s3 s4 s5 s6 s7 s18 s19 …..

1 ms sub-frame

SF0 SF1 SF2 SF9 …..

sy4 sy0 sy1 sy2 sy3 sy5 sy6

0.5 ms slot

SF3

- Frame duration =10 ms (same as UMTS)

- FDD: 10 ms radio frame for UL and 10 ms radio frame for DL

- Radio frame includes 10 subframes

- 1 Subframe represents a Transmission Time Interval (TTI)

- Each subframes includes two slots

- 1 slot = 7 (normal CP) or 6 symbols (extended CP)

SF: SubFrame

s: slot

Sy: symbol

Confidential


Resource Block

• Physical Resource Block or Resource Block (PRB or RB):

12 subcarriers in frequency domain (180kHz) x 1 slot period in time domain (0.5ms)

Subcarrier 1

Subcarrier 12

18

0 K

Hz

Capacity allocation is based on Resource Blocks

Resource Element

• Note: Although 3GPP definition of RB refers to 0.5ms, in some cases it is possible to find that RB refers to 12 subcarriers in frequency domain and 1ms in time domain. In particular, since the scheduler in the eNodeB works on TTI basis (1ms) RBs are considered to last 1ms in time domain. They can also be known as ‘scheduling resource blocks’

Confidential


Resource Element

• Theoretical minimum capacity allocation unit

• Equivalent to one subcarrier x one symbol period

• 72 or 84 Resource Elements per Resource Block

• Each Resource Element can accommodate 1 modulation symbol, e.g. 2 bits for QPSK, 4 bits for 16QAM and 6 bits for 64 QAM

• Modulation symbol rate per Resource Block is 144 ksps (extended CP) or 168 ksps (normal CP)


Case 1: Normal Cyclic Prefix, 84 RE Case 2: Extended Cyclic Prefix, 72 RE

7 symbols = 0.5 ms 6 symbols = 0.5 ms

Fre

quency D

om

ain

12 s

ubcarr

iers

= 1

80 k

Hz

Resource Element

12 s

ubcarr

iers

= 1

80 k

Hz

Time Domain Time Domain

Confidential


Downlink Physical Signals and Channels

• Downlink Physical Signals

– Reference Signals

– Synchronisation Signals

• Downlink Physical Channels

– Physical Broadcast Channel (PBCH)

– Physical Downlink Shared Channel (PDSCH)

– Physical Downlink Control Channel (PDCCH)

– Physical Control Format Indicator Channel (PCFICH)

– Physical Hybrid-ARQ Indicator Channel (PHICH)

– Physical Multicast Channel (PMCH)


Confidential


DL Physical Channels

PBCH:

• To broadcast the MIB (Master Information Block), RACH parameters

PDSCH:

• Carries user data, paging data, SIBs (cell status, cell IDs, allowed services…)

PMCH:

• For multicast traffic as MBMS services

PHICH:

• Carries H-ARQ Ack/Nack messages from eNB to UE in response to UL transmission

There are no dedicated channels in LTE, neither in UL nor DL

PCFICH: • Carries details of PDCCH format (e.g.# of symbols)

PDCCH:

• Carries the DCI (DL control information): schedule uplink resources on the PUSCH or downlink resources on the PDSCH. Alternatively, DCI transmits TPC commands for UL

Confidential


Mapping of DL Physical Channels (I)

• PBCH:

– Occupies the central 72 subcarriers across 4 symbols

– Transmitted during second slot of each 10 ms radio frame on all antennas

• PCFICH:

– Can be transmitted during the first 3 symbols of

each TTI

– Occupies up to 16 RE per TTI

• PHICH:

– Normal CP: Tx during 1st symbol of each TTI

– Extended CP: Tx during first 3 symbols of each TTI

• PDCCH:

– Occupies the RE left from PCFICH and PHICH within the first 3 symbols of each TTI

– Minimum number of symbols are occupied. If PDCCH data is small then it only occupies the 1st symbol

• PDSCH:

– Is allocated the RE not used by signals or other physical channels


RB

Confidential


Mapping of DL Physical Channels (II)

PBCH PDCCH PCFICH PHICH

20 slots = 10 subframes = 10 ms = 10 TTI

72 s

ubcarr

iers

(1

.4M

Hz)

PDSCH

• PDSCH physical channel used to transfer application data has access to whatever is left over

• PBCH, PCFICH, PDCCH and PHICH physical channels also occupy symbols and represent an overhead

TTI Control information at start of every TTI

Confidential


Uplink Physical Signals and Channels

• Uplink Physical Signals

– Demodulation Signals:

Used for channel estimation in the eNodeB receiver to demodulate control and data channels

Located in the 4th symbol (normal CP) of each slot and spans the same bandwidth as the allocated uplink data

– Sounding Reference Signals:

Provides uplink channel quality estimation as basis for the UL scheduling decisions -> similar in use as the CQI in DL

Sent in different parts of the bandwidth where no uplink data transmission is available.

Not part of first NSNs implementations (UL channel aware scheduler in RL40)

• Uplink Physical Channels

– Physical Uplink Shared Channel (PUSCH)

– Physical Uplink Control Channel (PUCCH)

– Physical Random Access Channel (PRACH)


Confidential


UL Physical Channels

• PUSCH: Physical Uplink Shared Channel

– Intended for the user data (carries traffic for multiple UEs)

• PUCCH: Physical Uplink Control Channel

– Carries H-ARQ Ack/Nack indications, uplink scheduling request, CQIs and MIMO feedback

– If control data is sent when traffic data is being transmitted, UE multiplexes both streams together

– If there is only control data to be sent the UE uses Resources Elements at the edges of the channel with higher power


RACH

CCCH DCCH DTCH

UL-SCH

PRACH PUSCH PUCCH

Logical

Transport

PHYS.

RLC

MAC

•PRACH: Physical Random Access Channel

– For Random Access attempts. PDCCH indicates the Resource elements for PRACH use

– PBCH contains a list of allowed preambles (max. 64 per cell in Type 1 frame) and the required length of the preamble

Confidential


Uplink Resource Mapping

• Demodulation Reference Signal:

Always on symbol 3 of each slot (normal CP)

• PUSCH mapping:

Data is allocated in multiples of 1 RB (12 subcarriers in frequency domain). Only factors of 2, 3 and 5 resource blocks are allowed

• PUCCH mapping:

If PUCCH not multiplexed with PUSCH then it is transmitted on a reserved frequency region. PUCCH occupies RBs at both edges of the uplink bandwidth (in green in the picture on the right)

Confidential


Random Access Channel (PRACH)

• RACH operation uses around 1.08 MHz bandwidth

– This is equal to 6 resource blocks of 180 kHz

• The location of those resource blocks is dynamically defined by 2 RRC Layer Parameters (PRACH Configuration Index and PRACH Frequency offset)

– 4 possible PRACH durations (PRACH configuration index parameter selects one of the 4)

• PRACH only carries the preambles and it is used during the RACH process


307200Ts

TPRE TGT TCP

Preamble CP

0.1 ms 0.1 ms 0.8 ms

Confidential

© Nokia Siemens Networks Presentation / Author / Date

b0 b1

QPSK

Im

Re 10

11

00

01

b0 b1b2b3

16QAM

Im

Re

0000

1111

Im

Re

64QAM

b0 b1b2b3 b4 b5

• 3GPP standard defines the following options: QPSK, 16QAM, 64QAM in both directions (UL and DL)

– UL 64QAM not supported in initial releases

• Not every physical channel is allowed to use any modulation scheme:

• Scheduler decides which form to use depending on carrier quality feedback information from the UE

Modulation Schemes

QPSK:

2 bits/symbol

16QAM:

4 bits/symbol

64QAM:

6 bits/symbol

Physical

channel

Modulation

PDSCH QPSK,

16QAM,

64QAM

PMCH QPSK,

16QAM,

64QAM

PBCH QPSK

PDCCH

(PCFICH,

PHICH)

QPSK

PUSCH QPSK,

16QAM,

64QAM

PUCCH BPSK and/or

QPSK

Confidential


LTE UE Connection Management Overview


Confidential


Mobility and Connection States (1/2)

• 2 sets of states for the UE are defined based on the information held in the MME:

– EMM: EPS Mobility Management States

– ECM: EPS Connection Management States

• EMM:

– EMM- DEREGISTERED

MME holds no valid location information about the UE (location unknown)

• UE can not be paged

– EMM- REGISTERED

UE registers with an MME and establishes a default bearer for application data transfer via attach procedure or TAU procedure after inter-system HO

UE responds to paging messages


EMM deregistered

EMM registered

Attach

Detach

EPS: Evolved Packet System

Confidential


Mobility and Connection States (2/2)

• ECM: – UE and MME enter ECM-CONNECTED state when the signaling connection is

established between UE and MME

– UE and E-UTRAN enter RRC-CONNECTED state when the signaling connection is established between UE and the E-UTRAN


ECM idle ECM connected

S1 connection establishment

S1 connection release

RRC idle RRC connected

RRC connection establishment

RRC connection release

UE E-UTRAN MME

MME

S1 connection RRC connection

Confidential


LTE Radio Resource Control (RRC) States RRC Idle state

– No signalling connection between UE and network exists

– UE performs cell reselections

– Paging needed when the there is data in downlink direction

– RACH procedure used on RRC connection establishment


• UEs RRC connection can be maintained even if UE is inactive

• RRC connection may be released due to the following reasons:

RRC Connected State

– A signalling connection exists between UE and network

– UE location is known in MME with an accuracy of a cell ID

– The mobility of UE is handled by the handover procedure

inactive >x min

2. High mobility: UE makes x handovers within m minutes

1. UE is inactive for a long time

3. Max number of RRC connected UEs reached. Then, longest inactive UE is released

Confidential


EMM & ECM States Transitions


EMM_Deregistered

ECM_Idle

Power On

Registration (Attach)

EMM_Registered

ECM_Connected

• Allocate C-RNTI, S_TMSI

• Allocate IP addresses

• Authentication

• Establish security context

• Release RRC connection

• Release C-RNTI

• Configure DRX for paging

EMM_Registered

ECM_Idle

Release due to

Inactivity

•Establish RRC Connection

•Allocate C-RNTI

New Traffic Deregistration (Detach)

Change PLMN

• Release C-RNTI, S-TMSI

• Release IP addresses

Timeout of Periodic TA

Update

• Release S-TMSI

• Release IP addresses

Confidential


LTE Mobility Management


Confidential


LTE Handover Principles

Only hard handovers in LTE (no soft handovers)

• Lossless

– Packets are forwarded from the source to the target

• UE-assisted

– Measurements are made and reported by the UE to the network

• Network-controlled

– Target cell is selected by the network, not by the UE

– Handover control in E-UTRAN (not in packet core)

• Late path switch

– Only once the handover is successful, the packet core is involved


Confidential


Handover Procedure


S-GW + P-GW

MME

Source eNB

Target eNB

MME MME MME

= Data in radio

= Signalling in radio = GTP tunnel

= GTP signalling

= S1 signalling

= X2 signalling

Before handover Handover

preparation Radio handover Late path switching

S-GW + P-GW S-GW + P-GW S-GW + P-GW

X2

Confidential


Handover Measurement Procedure

eNodeB sends Measurement control to UE giving Reporting thresholds

UE identifies others cell ids (Physical Cell ID - PCI -) from Synchronization Signal

UE measures other cells’ signal from Reference Signals (RS)

When the reporting threshold condition is fulfilled, UE sends Handover measurements to eNodeB


Confidential


Thank You

LTE Permulaan

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Transcript of LTE Permulaan