LTE Principle

Copyright©2011 Huawei Technologies Co., Ltd. All Rights Reserved.

LTELong Term Evolution

http://www.huawei.com/

Top right corner for field-mark, customer or partner logotypes.

---------------- The following nine groups of colors are an example of how our design colors can be used, please take note that you should only use one design color group per slide. For specific usage details, refer to the “Typesetting Standard”.

Copyright©2011 Huawei Technologies Co., Ltd. All Rights Reserved. 2

Mobile communication system evolution

1G (First Generation)

2G (Second Generation)

3G (Third Generation)

4G (Fourth Generation)

AMPS

TACS

ETACS

Advanced Mobile Telephone System

Total Access Communications System

Extended Total Access Communication System

GSM

CDMA One (IS-95)

DAMPS （ IS-136)

Global System for Mobile communications

Code Division Multiple Access Based on IS-95

Digital - Advanced Mobile Phone System Based onIS-136Other

UMTSWCDMA

TD-SCDMA

CDMA2000

WiMAX

LTE Advanced

UMBEV-DO Rev C

WiMAX802.16m




201120102009200820072006200520042003200220012000

R99 R4 R5 R6 R7 R8 R9 R10U

MT

S

HS

PA

DL

HS

PA

UL

LT

E

LT

E

Ad

v

HS

PA

+

EP

C

Co

mm

on

IMS

IMS

MM

Te

l

3GPP Time Line and Evolution




IMT Advanced RequirementsSpecific requirements of the IMT-Advanced report included: All-IP packet switched network and Interoperability with existing wireless standards. Share and use the network resources to support more simultaneous users per cell Scalable channel bandwidth 5–20 MHz, optionally up to 40 MHz Seamless connectivity and global roaming across multiple networks (smooth handovers). 1 Gbit/s in the downlink should be possible over less than 67 MHz bandwidth Data rate :

100 Mbit/s (high speeds)1 Gbit/s (fixed positions).

Peak link spectral efficiency :15 bit/s/Hz (downlink) 6.75 bit/s/Hz (uplink)

In the downlink spectral efficiency up to :3 bit/s/Hz/cell (outdoor)2.25 bit/s/Hz/cell (indoor)

14




LTE Background Introduction• What is LTE ？

LTE (Long Term Evolution) is known as the evolution of radio access technology conducted by 3GPP.

The radio access network will evolve to E-UTRAN (Evolved UMTS Terrestrial Radio Access Network), and the

correlated core network will evolved to SAE (System Architecture Evolution).

What can LTE do ？ Flexible bandwidth configuration: supporting 1.4MHz,

3MHz, 5MHz, 10Mhz, 15Mhz and 20MHz

Peak date rate (within 20MHz bandwidth): 100Mbps for

downlink and 50Mbps for uplink

Time delay: <100ms (control plane), <5ms (user plane)

Provide 100kbps data rate for mobile user (up to 350kmph)

Support eMBMS

Circuit services is implemented in PS domain: VoIP

Lower cost due to simple system structure




LTE Network Architecture• Main Network Element of LTE

The E-UTRAN consists of e-NodeBs, providing the user plane and control plane. The EPC consists of MME, S-GW and P-GW.

Compare with traditional 3G network, LTE architecture becomes much more simple and flat, which can lead to lower networking cost, higher networking flexibility and shorter time delay of user data and control signaling.

Network Interface of LTE The e-NodeBs are interconnected with each other by means of the X2 interface, which enabling direct transmission of

data and signaling. S1 is the interface between e-NodeBs and the EPC, more specifically to the MME via the S1-MME and to the S-GW via

the S1-U

eNB

MME / S-GW MME / S-GW

eNB

eNB

S1 S1

X2 E-UTRAN

UMTS LTE




Page 7

• SAE Brief Introduction SAE （ System Architecture Evolution ） considers evolution for the whole system architecture, including ：

Flat Functionality. Take out the RNC entity and part of the functions are arranged on e-NodeB in order to reduce the latency and enhance the schedule ability, such as interference coordination, internal load balance, etc.

Part of the functions are arranged on core network. To enhance the mobility management, all IP technology is applied, user-plane and control-plane are separated. The compatibility of other RAT is considered.

SGi

S4

S3 S1-MME

PCRF S7

S6a

HSS

Operator ’ s IP Services (e.g. IMS, PSS etc.)

Rx+ S10

UE

GERAN

UTRAN SGSN

“ LTE - Uu ” EUTRAN

MME

S11

S5 Serving SAE

Gateway

PDN SAE

Gateway S1-U

SAE




FDMA TDMA CDMA and OFDMA







Page 10

Introduction OFDM （ Orthogonal Frequency Division Multiplexing ） is a modulation

multiplexing scheme. The system bandwidth is divided into a plurality of

orthogonal.

Orthogonality of different subcarriers is achieved by the baseband IFFT.

OFDM OFDM has many advantages that can meet the needs of E-

UTRAN, which is one of B3G and 4G key technology.

OFDM is a modulation multiplexing scheme, and the

corresponding multi-access techniques is OFDMA. OFDMA are

used in LTE downlink.

For LTE uplink the multiple access scheme is SC-FDMA .

OFDM

…

Sub-carriersFFT

Time

Symbols

System Bandwidth

Guard

Intervals

…

Frequency

…

Sub-carriersFFT

Time

Symbols

System Bandwidth

Guard

Intervals

…

Frequency

OFDM 与 OFDMA 的比较




OFDMA and SC-FDMA Block Diagram

29




Cyclic Prefix

CPNormal

5,2 µs first symbol

4,7 µs other symbol

Extended 16,7 µs

ISI (Inter Symbol Interference)

COPY and insert

24




Page 13

OFDM & OFDMA OFDM (Orthogonal Frequency Division Multiplexing) is a

modulation multiplexing technology, divides the system bandwidth into orthogonal subcarriers. CP is inserted between the OFDM symbols to avoid the ISI.

OFDMA is the multi-access technology related with OFDM, is used in the LTE downlink. OFDMA is the combination of TDMA and FDMA essentially.

Advantage: High spectrum utilization efficiency due to orthogonal subcarriers need no protect bandwidth. Support frequency link auto adaptation and scheduling. Easy to combine with MIMO.

Disadvantage: Strict requirement of time-frequency domain synchronization. High PAPR.

DFT-S-OFDM & SC-FDMA DFT-S-OFDM (Discrete Fourier Transform Spread OFDM)

is the modulation multiplexing technology used in the LTE uplink, which is similar with OFDM but can release the UE PA limitation caused by high PAPR. Each user is assigned part of the system bandwidth.

SC-FDMA （ Single Carrier Frequency Division Multiple Accessing ） is the multi-access technology related with DFT-S-OFDM.

Advantage: High spectrum utilization efficiency due to orthogonal user bandwidth need no protect bandwidth. Low PAPR.

The subcarrier assignment scheme includes Localized mode and Distributed mode.

OFDMA & SC-FDMA

User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

System Bandwidth

Sub-band：12Sub-carriersTime

User 1

User 2

User 3

User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

System Bandwidth

Sub-band：12Sub-carriersTime

Sub-carriers

TTI: 1ms

Frequency

Time

System Bandwidth

Sub-band：12Sub-carriers

User 1

User 2

User 3

Sub-carriers

TTI: 1ms

Frequency

Time

System Bandwidth

Sub-band：12Sub-carriers

User 1

User 2

User 3

User 1

User 2

User 3




Frequency Band of LTE

E-UTRA Band

Uplink (UL) Downlink (DL)Duplex ModeFUL_low – FUL_high FDL_low – FDL_high

1 1920 MHz – 1980 MHz 2110 MHz – 2170 MHz FDD




5 824 MHz – 849 MHz 869 MHz – 894MHz FDD




9 1749.9 MHz–

1784.9 MHz 1844.9 MHz –

1879.9 MHzFDD


111427.9 MHz – 1452.9 MHz 1475.9 MHz – 1500.9 MHz FDD




… … 　　 … 　　 …


... … 　　 … 　　 …

E-UTRA Band

Uplink (UL) Downlink (DL)Duplex ModeFUL_low – FUL_high FDL_low – FDL_high

33 1900 MHz – 1920 MHz 1900 MHz – 1920 MHz TDD








TDD Frequency Band

FDD Frequency Band

From LTE Protocol: Duplex mode: FDD and TDD

Support frequency band form 700MHz to 2.6GHz

Support various bandwidth: 1.4MHz, 3MHz, 5MHz,

10MHz, 15MHz, 20MHz

Protocol is being updated, frequency information could be

changed.







Carrier Frequency EARFCN Calculation

eNB

UE

FDL = FDL_low + 0.1(NDL - NOffs-DL)

FUL = FUL_low + 0.1(NUL - NOffs-UL)

The values of FDL_low ， NDL ， NOffs-DL can be found from 3GPP 36.101, as below ：




Page 17

Radio Frame Structures Supported by LTE:

Type 1, applicable to FDD

Type 2, applicable to TDD

FDD Radio Frame Structure:

LTE applies OFDM technology, with subcarrier spacing f=15kHz and 2048-order IFFT. The time unit in

frame structure is Ts=1/(2048* 15000) second

FDD radio frame is 10ms shown as below, divided into 20 slots which are 0.5ms. One slot consists of 7

consecutive OFDM Symbols under Normal CP configuration

#0 #1 #2 #3 #19#18

One radio frame, Tf = 307200Ts = 10 ms

One slot, Tslot = 15360Ts = 0.5 ms

One subframe FDD Radio Frame Structure

Concept of Resource Block: LTE consists of time domain and frequency domain resources. The minimum unit for schedule is RB

(Resource Block), which compose of RE (Resource Element)

RE has 2-dimension structure: symbol of time domain and subcarrier of frequency domain

One RB consists of 1 slot and 12 consecutive subcarriers under Normal CP configuration

Radio Frame Structure (1)




Resource Block




Page 19

• TDD Radio Frame Structure:

Applies OFDM, same subcarriers spacing and time

unit with FDD.

Similar frame structure with FDD. radio frame is

10ms shown as below, divided into 20 slots which

are 0.5ms.

The uplink-downlink configuration of 10ms frame are

shown in the right table.

One slot, Tslot=15360Ts

GP UpPTSDwPTS

One radio frame, Tf = 307200Ts = 10 ms

One half-frame, 153600Ts = 5 ms

30720Ts

One subframe, 30720Ts

GP UpPTSDwPTS

Subframe #2 Subframe #3 Subframe #4Subframe #0 Subframe #5 Subframe #7 Subframe #8 Subframe #9

Uplink-downlink Configurations

Uplink-downlink configuration

Downlink-to-Uplink Switch-point periodicity

Subframe number

0 1 2 3 4 5 6 7 8 9

0 5 ms D S U U U D S U U U

1 5 ms D S U U D D S U U D

2 5 ms D S U D D D S U D D

3 10 ms D S U U U D D D D D

4 10 ms D S U U D D D D D D

5 10 ms D S U D D D D D D D

6 5 ms D S U U U D S U U D

DwPTS: Downlink Pilot Time Slot

GP: Guard Period

UpPTS: Uplink Pilot Time Slot

TDD Radio Frame Structure

D: Downlink subframe

U: Uplink subframe

S: Special subframe

Radio Frame Structure (2)




Page 20

• Special Subrame Structure: Special Subframe consists of DwPTS, GP and UpPTS . 9 types of Special subframe configuration. Guard Period size determines the maximal cell radius.

(100km) DwPTS consists of at least 3 OFDM symbols, carrying

RS, control message and data. UpPTS consists of at least 1 OFDM symbol, carrying

sounding RS or short RACH.

Configuration of special subframe

Special Subframe Structure

Special subframe configuration

Normal cyclic prefix

DwPTS GP UpPTS

0 3 10

1

1 9 4

2 10 3

3 11 2

4 12 1

5 3 9

26 9 3

7 10 2

8 11 1




Page 21

Radio Frame Structure (3)• CP Length Configuration:

Cyclic Prefix is applied to eliminate ISI of

OFDM.

CP length is related with coverage radius.

Normal CP can fulfill the requirement of

common scenarios. Extended CP is for wide

coverage scenario.

Longer CP, higher overheading.

Configuration DL OFDM CP LengthUL SC-FDMA CP

LengthSub-carrier of

each RBSymbol of each slot

Normal CP f=15kHz160 for slot #0

144 for slot #1~#6

160 for slot #0

144 for slot #1~#6 127

Extended CP

f=15kHz 512 for slot #0~#5 512 for slot #0~#5 6

f=7.5kHz 1024 for slot #0~#2 NULL 24 (DL only) 3 (DL only)

CP Configuration

Slot structure under Normal CP configuration

( f=15kHz)△

Slot structure under Extended CP configuration

( f=15kHz)△

Slot structure under Extended CP configuration

( f=7.5kHz)△




Page 22

Brief Introduction of Physical Channels

Downlink Channels ： Physical Broadcast Channel (PBCH): Carries system information for cell

search, such as cell ID.

Physical Downlink Control Channel (PDCCH) : Carries the resource allocation

of PCH and DL-SCH, and Hybrid ARQ information.

Physical Downlink Shared Channel (PDSCH) : Carries the downlink user data.

Physical Control Format Indicator Channel (PCFICH) : Carriers information of

the OFDM symbols number used for the PDCCH.

Physical Hybrid ARQ Indicator Channel (PHICH) : Carries Hybrid ARQ

ACK/NACK in response to uplink transmissions.

Physical Multicast Channel (PMCH) : Carries the multicast information.

Uplink Channels ： Physical Random Access Channel (PRACH) : Carries the random access

preamble.

Physical Uplink Shared Channel (PUSCH) : Carries the uplink user data.

Physical Uplink Control Channel (PUCCH) : Carries the HARQ ACK/NACK,

Scheduling Request (SR) and Channel Quality Indicator (CQI), etc.

BCH PCH DL-SCHMCH

DownlinkPhysical channels

DownlinkTransport channels

PBCH PDSCHPMCH PDCCH

UplinkPhysical channels

UplinkTransport channels

UL-SCH

PUSCH

RACH

PUCCHPRACH

Mapping between downlink transport channels and downlink physical channels

Mapping between uplink transport channels and downlink physical channels

Physical Layer

MAC Layer

Physical Layer

MAC Layer




Page 23

Downlink Physical Channel

ScramblingModulation

mapper

Layermapper

Precoding

Resource element mapper

OFDM signal generation


OFDM signal generation


mapper

layers antenna portscode words

Downlink Physical Channel Processing scrambling of coded bits in each of the code words to be transmitted on a physical channel modulation of scrambled bits to generate complex-valued modulation symbols mapping of the complex-valued modulation symbols onto one or several transmission layers precoding of the complex-valued modulation symbols on each layer for transmission on the antenna ports mapping of complex-valued modulation symbols for each antenna port to resource elements generation of complex-valued time-domain OFDM signal for each antenna port

Modulation Scheme of Downlink Channel

Shown at the right table

Phy Ch Modulation Scheme Phy Ch Modulation Scheme

PBCH QPSK PCFICH QPSK

PDCCH QPSK PHICH BPSK

PDSCH QPSK, 16QAM, 64QAM PMCH QPSK, 16QAM, 64QAM




Page 24

Uplink Physical ChannelUplink Physical Channel Processing

scrambling modulation of scrambled bits to generate complex-valued symbols transform precoding to generate complex-valued symbols mapping of complex-valued symbols to resource elements generation of complex-valued time-domain SC-FDMA signal for each antenna port

Modulation Scheme of Downlink Channel Shown at the right table

Phy Ch Modulation Scheme

PUCCH BPSK, QPSK

PUSCH QPSK, 16QAM, 64QAM

PRACH Zadoff-Chu


mapperTransform precoder


SC-FDMA signal gen.




Page 25

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l

One

ant

enna

por

tTw

o an

tenn

a po

rts

Resource element (k,l)

Not used for transmission on this antenna port

Reference symbols on this antenna port

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l 0l

1R

1R

1R

1R

6l 0l

1R

1R

1R

1R

6l

0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l 0l

1R

1R

1R

1R

6l 0l

1R

1R

1R

1R

6l

Four

ant

enna

por

ts

0l 6l 0l

2R

6l 0l 6l 0l 6l

2R

2R

2R

3R

3R

3R

3R

even-numbered slots odd-numbered slots

Antenna port 0


Antenna port 1


Antenna port 2


Antenna port 3

Downlink Physical Signals (1)Downlink RS (Reference Signal):

Similar with Pilot signal of CDMA. Used for downlink physical channel demodulation

and channel quality measurement (CQI)

Three types of RS in protocol. Cell-Specific Reference Signal is essential and the other

two types RS (MBSFN Specific RS & UE-Specific RS) are optional.

Cell-Specific RS Mapping in Time-

Frequency DomainOn

e A

nte

nn

a

Po

rtTw

o A

nte

nn

a

Po

rts

Fo

ur

An

ten

na

P

ort

s

Antenna Port 0 Antenna Port 1 Antenna Port 2 Antenna Port 3

Characteristics: Cell-Specific Reference Signals are generated from cell-specific RS

sequence and frequency shift mapping. RS is the pseudo-random

sequence transmits in the time-frequency domain.

The frequency interval of RS is 6 subcarriers.

RS distributes discretely in the time-frequency domain, sampling the

channel situation which is the reference of DL demodulation.

Serried RS distribution leads to accurate channel estimation, also high

overhead that impacting the system capacity.

MBSFN: Multicast/Broadcast over a Single Frequency Network

RE

Not used for RS transmission on this antenna port

RS symbols on this antenna port

R1: RS transmitted in 1st ant port

R2: RS transmitted in 2nd ant port

R3: RS transmitted in 3rd ant port

R4: RS transmitted in 4th ant port




Page 26

Synchronization Signal: synchronization signals are used for time-frequency synchronization between UE and E-UTRAN during cell search.

synchronization signal comprise two parts:

Primary Synchronization Signal, used for symbol timing, frequency synchronization and part of the cell ID detection.

Secondary Synchronization Signal, used for detection of radio frame timing, CP length and cell group ID.

Synchronization Signals Structure

Characteristics: The bandwidth of the synchronization signal is

62 subcarrier, locating in the central part of

system bandwidth, regardless of system

bandwidth size.

Synchronization signals are transmitted only in

the 1st and 11rd slots of every 10ms frame.

The primary synchronization signal is located in

the last symbol of the transmit slot. The

secondary synchronization signal is located in

the 2nd last symbol of the transmit slot.

Downlink Physical Signals (2)




Page 27

Uplink RS (Reference Signal): The uplink pilot signal, used for synchronization between

E-UTRAN and UE, as well as uplink channel estimation.

Two types of UL reference signals: DM RS (Demodulation Reference Signal), associated with

PUSCH and PUCCH transmission.

SRS (Sounding Reference Signal), without associated with

PUSCH and PUCCH transmission.Characteristics:

Each UE occupies parts of the system bandwidth since SC-FDMA

is applied in uplink. DM RS only transmits in the bandwidth

allocated to PUSCH and PUCCH.

The slot location of DM RS differs with associated PUSCH and

PUCCH format.

Sounding RS’s bandwidth is larger than that allocated to UE, in

order to provide the reference to e-NodeB for channel estimation in

the whole bandwidth.

Sounding RS is mapped to the last symbol of sub-frame. The

transmitted bandwidth and period can be configured. SRS

transmission scheduling of multi UE can achieve

time/frequency/code diversity.

DM RS associated with PUSCH is mapped to the 4th symbol each slot

Time

Freq

Time

Freq

Time

Freq

DM RS associated with PUCCH (transmits UL ACK signaling) is mapped to the central 3

symbols each slot

DM RS associated with PUCCH (transmits UL CQI signaling) is mapped to the 2

symbols each slot

PUCCH is mapped to up & down ends of the system bandwidth,

hopping between two slots.

Allocated UL bandwidth of one UE

System bandwidth

Uplink Physical Signals




Downlink Resource Structure• Downlink Resource Structure

Type I frame, single antenna, ΔF = 15 kHz

Standard RB:

One of center 6 RBs:

Legend:

Downlink Reference SignalsPBCH (Physical Broadcast Channel)

PSS (Primary Synchronisation Signal)

SSS (Secondary Synchronisation Signal)

PDCCH / PHICH / PCFICH (Physical - Downlink Control / HARQ Indicator / Control Format Indicator - Channels)

PDSCH (Physical Downlink Shared Data Channel)

© Forsk 2010




Downlink Resource Structure

OFDMSymbol 0C

P OFDMSymbol 1C

P OFDMSymbol 3C

P OFDMSymbol 4C

P OFDMSymbol 5C

P OFDMSymbol 6C

POFDMSymbol 2C

P

Legend: Downlink Reference signals

PBCH PSS SSS

PDCCH / PHICH / PCFICH PDSCH

1 subframe = 2 slot (1 ms)

1 frame = 10 subframe (10 ms)

SF 0 SF 1 SF 2 SF 3 SF 4 SF 5 SF 6 SF 7 SF 8 SF 9

7 OFDM symbols at normal CP per slot (0.5 ms)

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

Cen

tre

6 R

Bs

© Forsk 2010




Uplink Resource Structure

OFDMSymbol 0C

P OFDMSymbol 1C

P OFDMSymbol 3C

P OFDMSymbol 4C

P OFDMSymbol 5C

P OFDMSymbol 6C

POFDMSymbol 2C

P

Legend:

UL DMRS (Uplink Demodulation Reference Signal)

UL SRS (Uplink Sounding Reference Signal)

PUCCH (Physical Uplink Control Channel)

(incl.HARQ feedback and CQI reporting)

Demodulation Reference Signal for PUCC

PUSCH (Physical Uplink Shared Data Channel)SF 0 SF 1 SF 2 SF 3 SF 4 SF 5 SF 6 SF 7 SF 8 SF 9

7 OFDM symbols at normal CP per slot (0.5 ms)

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

© Forsk 2010

1 subframe = 2 slot (1 ms)

1 frame = 10 subframe (10 ms)




Page 31

Basic Principle of Cell Search: Cell search is the procedure of UE synchronizes with E-UTRAN in

time-freq domain, and acquires the serving cell ID.

Two steps in cell search:

Step 1: Symbol synchronization and acquirement of ID within

Cell Group by demodulating the Primary Synchronization Signal;

Step 2: Frame synchronization, acquirement of CP length and

Cell Group ID by demodulating the Secondary Synchronization

Signal.

About Cell ID ： In LTE protocol, the physical layer Cell ID comprises two parts:

Cell Group ID and ID within Cell Group. The latest version defines

that there are 168 Cell Group IDs, 3 IDs within each group. So

totally 168*3=504 Cell IDs exist.

represents Cell Group ID, value from 0 to 167;

represents ID within Cell Group, value from 0 to 2.

(2)ID

(1)ID

cellID 3 NNN

(1)IDN(2)IDN

Initial Cell Search: The initial cell search is carried on after the UE power on. Usually, UE doesn’t

know the network bandwidth and carrier frequency at the first time switch on. UE repeats the basic cell search, tries all the carrier frequency in the spectrum to

demodulate the synchronization signals. This procedure takes time, but the time requirement are typically relatively relaxed. Some methods can reduce time, such as recording the former available network information as the prior search target.

Once finish the cell search, which achieve synchronization of time-freq domain and acquirement of Cell ID, UE demodulates the PBCH and acquires for system information, such as bandwidth and Tx antenna number.

After the procedure above, UE demodulates the PDCCH for its paging period that allocated by system. UE wakes up from the IDLE state in the specified paging period, demodulates PDCCH for monitoring paging. If paging is detected, PDSCH resources will be demodulated to receive paging message.

Search Freq

Sync Signals

PBCH

PDCCH

PDSCH

Physical Layer Procedure — Cell Search




Page 32

Basic Principle of Random Access : Random access is the procedure of uplink synchronization

between UE and E-UTRAN.

Prior to random access, physical layer shall receive the following information from the higher layers:

Random access channel parameters: PRACH configuration, frequency position and preamble format, etc.

Parameters for determining the preamble root sequences and their cyclic shifts in the sequence set for the cell, in order to demodulate the random access preamble.

Two steps in physical layer random access: UE transmission of random access preamble

Random access response from E-UTRAN

Detail Procedure of Random Access: Physical Layer procedure is triggered upon request of a preamble

transmission by higher layers.

The higher layers request indicates a preamble index, a target preamble received power, a corresponding RA-RNTI and a PRACH resource .

UE determines the preamble transmission power is preamble target received power + Path Loss. The transmission shall not higher than the maximum transmission power of UE. Path Loss is the downlink path loss estimate calculated in the UE.

A preamble sequence is selected from the preamble sequence set using the preamble index.

A single preamble is transmitted using the selected preamble sequence with calculated transmission power on the indicated PRACH resource.

UE Detection of a PDCCH with the indicated RA-RNTI is attempted during a window controlled by higher layers. If detected, the corresponding PDSCH transport block is passed to higher layers. The higher layers parse the transport block and indicate the 20-bit grant.

PRACHRA Preamble

PDCCHRA Response

RA-RNTI: Random Access Radio Network Temporary Identifier

Physical Layer Procedure — Radom Access




Page 33

Basic Principle of Power Control:

Downlink power control determines the EPRE (Energy per

Resource Element);

Uplink power control determines the energy per DFT-SOFDM

(also called SC-FDMA) symbol.

Uplink Power Control: Uplink power control consists of opened loop power and closed loop power control.

A cell wide overload indicator (OI) is exchanged over X2 interface for integrated inter-

cell power control, possible to enhance the system performance through power

control.

PUSCH, PUCCH, PRACH and Sounding RS can be controlled respectively by uplink

power control. Take PUSCH power control for example:

PUSCH power control is the slow power control, to compensate the path loss and

shadow fading and control inter-cell interference. The control principle is shown in

above equation. The following factors impact PUSCH transmission power PPUSCH: UE

maximum transmission power PMAX, UE allocated resource MPUSCH, initial transmission

power PO_PUSCH, estimated path loss PL, modulation coding factor △TF and system

adjustment factor f (not working during opened loop PC)

UE report CQI

DL Tx Power

EPRE: Energy per Resource Element

DFT-SOFDM: Discrete Fourier Transform Spread OFDM

f(i)}(i)ΔPLα(j)(j)P(i))(M,{P(i)P TFO_PUSCHPUSCHMAXPUSCH 10log10min

Downlink Power Control: The transmission power of downlink RS is usually constant. The

transmission power of PDSCH is proportional with RS transmission power.

Downlink transmission power will be adjusted by the comparison of UE

report CQI and target CQI during the power control.

X2

UL Tx Power

System adjust

parameters

Physical Layer Procedure — Power Control




Page 34Page 34

Adaptive Modulation and Coding

2 bits per symbol in each carrier.



The most appropriate modulation and coding scheme can be adaptively selected according to the channel propagation conduction, then the maximum throughput can be obtained for different channel situation.




LTE Feature

• MIMO• ICIC• SON

ANR Automatic Detection and Collision PCI Mobility Load Balancing

• CSFB




Page 36

Downlink MIMO MIMO is supported in LTE downlink to achieve spatial

multiplexing, including single user mode SU-MIMO and multi user mode MU-MIMO.

In order to improve MIMO performance, pre-coding is used in both SU-MIMO and MU-MIMO to control/reduce the interference among spatial multiplexing data flows.

The spatial multiplexing data flows are scheduled to one single user In SU-MIMO, to enhance the transmission rate and spectrum efficiency. In MU-MIMO, the data flows are scheduled to multi users and the resources are shared within users. Multi user gain can be achieved by user scheduling in the spatial domain.

Uplink MIMO Due to UE cost and power consumption, it is difficult to implement

the UL multi transmission and relative power supply. Virtual-MIMO, in which multi single antenna UEs are associated to transmit in the MIMO mode. Virtual-MIMO is still under study.

Scheduler assigns the same resource to multi users. Each user transmits data by single antenna. System separates the data by the specific MIMO demodulation scheme.

MIMO gain and power gain (higher Tx power in the same time-freq resource) can be achieved by Virtual-MIMO. Interference of the multi user data can be controlled by the scheduler, which also bring multi user gain.

Pre-coding vectors

User k data

User 2 data

User 1 data

Channel Information

User1

User2

User k

Scheduler Pre-coder

S1

S2

Pre-coding vectors

User k data

User 2 data

User 1 data

Channel Information

User1

User2

User k

Scheduler Pre-coder

S1

S2

User 1 data

Channel Information

User1

User2

User kScheduler

MIMO

DecoderUser k data

User 1 data

User 1 data

Channel Information

User1

User2

User kScheduler

MIMO

DecoderUser k data

User 1 data

DL-MIMO Virtual-MIMO

MIMO




Page 37Page 37

DL MIMO

codeword

UE1

User1SFBC

Mod

SFBC (Transmit Diversity)

Same stream transmitted simultaneously in certain form of MIMO coding at the same time-frequency resource from both antenna ports (Rank = 1)

Depending on the environment & number of antennas, SFBC can reduce fading margin by 2~8 dB, to extend coverage, and enhance system capacity

UE1

Layer 1, CW1, AMC1UE2

Layer 2, CW2, AMC2

MIMO encoder and layer mapping

MCW (Spatial Multiplexing)

Multiple data streams transmitted at the same time-frequency resource from different antenna ports

The terminal must have at least 2 Rx antennas for spatial multiplexing (SM)




Page 38

Frequency

Cell 3,5,7Power

Frequency

Cell 3,5,7Power

Frequency

Cell 2,4,6Power

Frequency

Cell 2,4,6Power

ICIC is one solution for the cell interference control, is essentially a schedule strategy. In LTE, some coordination schemes( ICIC )

can control the interference in cell edges to enhance the frequency reuse factor and performance in the cell edges.

1

2

3

6

5

7

4

1

2

3

6

5

7

4

The edge band is assigned to the users in cell edge. The eNB transmit power of the

edge band can be high.

Center Band

Cell 2,4,6 Primary Band

Frequency

Cell 1Power

Frequency

Cell 1Power

Cell 1 Edge Band

Center Band

Cell 3,5,7P Edge Band

The center band is assigned to the users in cell center. The eNB transmit power of the center band

should be reduced in order to avoid the interference to the edge band of neighbor cells.

Center Band

Center Band

ICIC （ Inter-Cell Interference

Coordination ）




SON （ Self-Organising Networks ）• SON Brief Introduction

SON (Self Organization Network) is the functions of LTE that required by the NGMN (Next Generation Mobile Network) operators.

From the point of view of the operator’s benefit and experiences, the early communication systems had bad O&M compatibility and high cost.

New requirements of LTE are brought forward, mainly focus on FCAPSI (Fault, Configuration, Alarm, Performance, Security, Inventory) management:

Self-planning and Self-configuration, support plug and play

Self-Optimization and Self-healing

Self-Maintenance




Page 40

Add new Sites

New site configured site

Description:

• Auto configure and optimize Neighbor

relations, intra-LTE and inter-RAT

• X2 automatic setup

• Operator defined rules and monitoring

supported

Description:

• Auto configure and optimize Neighbor

relations, intra-LTE and inter-RAT

• X2 automatic setup

• Operator defined rules and monitoring

supported

Benefits:

• Fast definition of Neighbor Relations

• up to 95% lower cost of neighbor relation

planning and optimization

• Improve customer experience by reducing

HO failure caused by missing neighbor

relations

Benefits:

• Fast definition of Neighbor Relations

• up to 95% lower cost of neighbor relation

planning and optimization


HO failure caused by missing neighbor

relations

SON_ANR (Automatic Neighbor Relation)




Page 41

ANR functionality ANR management is implemented through the following functions:

Automatic detection of missing neighboring cells Automatic evaluation of neighbor relations Automatic detection of Physical Cell Identifier (PCI) collisions Automatic detection of abnormal neighboring cell coverage

Automatic Neighbor Relation (ANR) can automatically add and maintain neighbor relations. The initial network construction, however, should not fully depend on ANR for the following considerations:

ANR is closely related to traffic in the entire network ANR is based on UE measurements but the delay is introduced in the measurements.

After initial neighbor relations configured and the number of UEs increasing, some neighboring relations may be missing. In this case, ANR can be used to detect missing neighboring cells and add neighbor relations.




Page 42

ANR functionality Two main type of ANR:

Event triggered Periodical reporting – fast ANR

• Both Event triggered and Fast ANR are applicable for same system or different systems




SON_Automatic Detection of PCI Collisions

• A PCI collision means the serving cell and a neighboring cell have the same PCI but different ECGIs. PCI collisions may be caused by improper network planning or abnormal neighboring cell coverage (also known as cross-cell coverage). If two neighboring cells have the same PCI, interference will be generated.

• When a PCI collision occurs, the eNodeB cannot determine the target cell for a handover. In this situation, the handover performance deteriorates and the handover success rate is reduced.

• After a PCI collision is removed, the following conditions are met: The PCI is unique in the coverage area of a cell. The PCI is unique in the neighbor relations of a cell.

Page 43




SON_Automatic Detection of PCI Collisions Cont.Automatic Detection of PCI Collisions• After a neighbor relation is added to the NRT, the eNodeB compares the PCI of the new neighboring cell with the

PCIs of existing neighboring cells in the case of IntraRatEventAnrSwitch is set to ON. If the new neighboring cell and an existing neighboring cell have the same ECGI but different PCIs, the eNodeB reports a PCI collision to the M2000. The M2000 collects statistics about PCI collisions and generates a list of PCI collisions.

Reallocating PCIs • PCI reallocation is a process of reallocating a new PCI to a cell whose PCI collides with the PCI of another cell. The

purpose is to remove PCI collisions. • The M2000 triggers the PCI reallocation algorithm to provide suggestions on PCI reallocation.

Note: • After the PCI of a cell is changed, the cell needs to be reestablished and the services carried on the cell are

disrupted. Therefore, the PCI reallocation algorithm only provides reallocation suggestions. A PCI can be reallocated manually or automatically through a scheduled task configured on the M2000.

Page 44




Page 45

Cell A Cell B Cell C

Cell CCell BCell A

Description:

• Exchange cell load information over X2

• Offload congested cells

• Optimize cell reselection / handover

parameters

Description:

• Exchange cell load information over X2

• Offload congested cells

• Optimize cell reselection / handover

parameters

Benefits:

• Increase 10% system capacity and 10%-20%

access success rate in unbalance scenario


call drop rate, handover failure rate, and

unnecessary redirection caused by

unbalanced load

Benefits:

• Increase 10% system capacity and 10%-20%

access success rate in unbalance scenario


call drop rate, handover failure rate, and

unnecessary redirection caused by

unbalanced load

SON_MLB( Mobility Load Balancing)




How to solve Mobility

Problems?

PING PONG

unnecessary HO Rate

HO successful rate

Valu

e

Before adopt MRO After adopt MRO

Description:

• HO parameters are optimized based

upon long term UE mobility behavior

• Avoid Ping-Pong handover, handover

too early, handover too late, etc

Description:

• HO parameters are optimized based

upon long term UE mobility behavior

• Avoid Ping-Pong handover, handover

too early, handover too late, etc

Benefits:

• Reduce cost of mobility optimization


call drop rate and handover failure rate

Benefits:

• Reduce cost of mobility optimization


call drop rate and handover failure rate

SON_MRO( Mobility Robust Optimization )

HUAWEI TECHNOLOGIES CO., LTD.

THANK YOU




PAPR

Cyclic Prefix

Documents

LTE Principle