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© 2013 Nokia Solutions and Networks. All rights reserved.

LTE TDD Overview

October 2013

Bong Youl (Brian) Cho, 조 봉 열

[email protected] Disclaimer

본 자료의 내용은 LTE 기술 자체에 대한 내용을 위주로 한 것으로서, NSN 제품전략 및 계획 등과는 반드시 일치하지 않을 수도 있습니다.

TTA LTE Standards/Technology Training

2 © 2013 Nokia Solutions and Networks. All rights reserved.

LTE TDD market overview

Quick comparison b/w WiMAX & LTE TDD

LTE TDD Technology Overview

TDD Carrier Aggregation

TDD Enhancement in Rel-12 and beyond



Difference b/w 3G-TDD and 4G-TDD

Note:

• 3GPP 표준에는 GSM, WCDMA/HSPA, LTE 기술이 모두 포함되어 있으며, 3가지 기술 모두가 지속적으로 진화함

• LTE-Advanced는 LTE와는 별도의 기술이 아니라 LTE의 진화의 한 경로 혹은 단계임

2000 2001 2002 2003 2004 2005

Release 99

Release 4

Release 5

Release 6

1.28Mcps TDD

HSDPA

W-CDMA

HSUPA, MBMS

2006 2007 2008 2009

Release 7 HSPA+ (MIMO, HOM etc.)

Release 8

2010 2011

LTE (FDD, TDD)

Release 9

Release 10

Minor LTE enhancements

2012 2013

Release 11

ITU-R M.1457 IMT-2000 Recommendation

LTE-Advanced ITU-R M.2012 IMT-Advanced Recommendation

2014

Release 12

1999



LTE FDD+LTE TDD make “the best LTE”

From etnews.com on May 28, 2013

“LTE FDD is only the half part of LTE”

• The number of LTE TDD operators at the moment is small, but those are big operators

• LTE TDD has very high commonality with LTE FDD, and works also with 3G

• Many WiMAX operators are considering migration to LTE TDD

• 2.3GHz and 2.6GHz are two key bands for LTE TDD



Key countries updates

Japan: >1M LTE TDD subs. Interest in 3.5GHz

Australia: Optus launch LTE TDD

Europe: LTE TDD spectrum auctioned, TDD will follow FDD

Clearwire ready for major LTE TDD roll-out

China Mobile bid process on-going for 200,000 eNodeB, 1M LTE TDD terminals

RoW

Dell’Oro January 2013:

•Increased Near Term Outlook for TDD

•Expects Europe will augment FDD with TDD



LTE TDD devices overview

LTE TDD device band support*

2300 MHz Band 40: 82 devices



The largest supported LTE TDD eco-system is:

Bands 38 (2.6 GHz) and 40 (2.3 GHz) have the

largest ecosystems of LTE TDD user devices currently :

• Terminal support for band 38 is 71%

• Terminal support for band 40 is 66%

• Band 41 (2.6GHz) will be deployed by Softbank, CMCC and Clearwire so terminal ecosystem will be substantial in future

• Support for 1.9 GHz (band 39)

and 3.5 GHz (bands 42, 43) is also picking up

124 LTE TDD user devices (dongles, MiFi, CPE, smartphones) LTE TDD eco-system is ready!

* January 2013 GSA report

New dual mode Samsung handsets to supercharge

Optus' 4G Network, 2013-08-05, Sydney

https://www.optus.com.au/aboutoptus/About+Optus/Medi

a+Centre/Media+Releases/2013/New+dual+mode+Sams

ung+handsets+to+supercharge+Optus'+4G+Network



LTE TDD DL/UL Config Brings Higher DL PDR & Flexibility

Peak data rate [Mbps]

Similar Spectrum Efficiency with FDD LTE

DL/UL(3:1) to DL service up to 110Mbps



3GPP E-UTRA TDD frequency bands

E-UTRA

Operating

Band

Uplink (UL) operating band

BS receive UE transmit

Downlink (DL) operating band

BS transmit UE receive Duplex

Mode

FUL_low – FUL_high FDL_low – FDL_high

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














LTE FDD, LTE TDD Integration

Standards Integration

Product Integration

Maximized commonality b/w FDD and TDD for high level of integration/interworking

LTE FDD

LTE TDD

Glo

bal

Ro

am

ing

LTE FDD & TDD

LT

E F

DD

& T

DD

Tra

nsp

are

nt

han

d o

ver

Fully integrated over time



DL OFDMA & UL SC-FDMA in LTE

• DL: OFDMA (Orthogonal Frequency Division Multiple Access)

– Less critical AMP efficiency in BS side

– Concerns on high RX complexity in terminal side

• UL: SC-FDMA (Single Carrier-FDMA), aka DFTS-OFDM

– Less critical RX complexity in BS side

– Critical AMP complexity in terminal side (Cost, power Consumption, UL coverage)

Making MS cheap as much as possible by moving all the burdens from MS to BS



CM (Cubic Metric) of OFDMA & SC-FDMA

OFDMA

SC-FDMA 16QAM

SC-FDMA QPSK

SC-FDMA pi/2-BPSK



SC-FDMA: A good introductory paper



LTE Physical channels and signals: DL

LTE WCDMA/HSPA WiMAX

PDSCH (DL data delivery and others)

HS-PDSCH, SCCPCH DL Data Burst

PBCH (MIB delivery)

PCCPCH DCD, Preamble

PMCH (MBMS)

DL Data Burst

PCFICH (Header for PDCCH)

FCH

PDCCH (Header for PDSCH, PUSCH)

HS-SCCH, E-AGCH, E-

RGCH

DL-MAP, UL-MAP

PHICH (HARQ Ack/Nack for UL)

E-HICH DL Data Burst

Cell-specific Reference Signal (Common pilot)

CPICH with primary

scrambling code

Pilot Signal (common)

UE-specific Reference Signal (UE dedicated pilot)

With secondary scrambling

code

Pilot Signal (dedicated)

Sync Signal (UE initial DL synchronization)

SCH Preamble



LTE WCDMA/HSPA WiMAX

PUSCH (UL data delivery and CSI delivery)

(E-DPDCH) UL Data Burst

PUCCH (CSI delivery, HARQ Ack/Nack for DL,

SR delivery)

HS-DPCCH CQICH, ACKCH, BW

Request Ranging

PRACH (Random access)

PRACH Initial Ranging

Demodulation RS (Pilot for PUSCH, PUCCH)

(E-DPCCH) Pilot Signal

Sounding RS (Additional pilot for other purposes)

Sounding Signal

LTE Physical channels and signals: UL



Quick comparison: OFDM parameter, MIMO



WiMAX-Advanced DL Performance*

• FDD: DL cell spectral efficiency in bit/s/Hz/cell

• FDD: DL cell edge user spectral efficiency in bit/s/Hz/cell

• TDD: DL cell spectral efficiency in bit/s/Hz/cell

• TDD: DL cell edge user spectral efficiency in bit/s/Hz/cell

InH UMi UMa RMa

Cell spectral efficiency 6.87 3.27 2.41 3.15

ITU-R requirement 3.0 2.6 2.2 1.1

InH UMi UMa RMa



InH UMi UMa RMa



InH UMi UMa RMa


ITU-R requirement 0.1 0.075 0.06 0.04 * IMT-ADV/4-E



WiMAX-Advanced UL Performance*

• FDD: UL cell spectral efficiency in bit/s/Hz/cell

• FDD: UL cell edge user spectral efficiency in bit/s/Hz/cell

• TDD: UL cell spectral efficiency in bit/s/Hz/cell

• TDD: UL cell edge user spectral efficiency in bit/s/Hz/cell

InH UMi UMa RMa



InH UMi UMa RMa



InH UMi UMa RMa



InH UMi UMa RMa



* IMT-ADV/4-E



LTE-Advanced DL Performance*

• FDD: DL cell spectral efficiency in bit/s/Hz/cell

• FDD: DL cell edge user spectral efficiency in bit/s/Hz/cell

• TDD: DL cell spectral efficiency in bit/s/Hz/cell

• TDD: DL cell edge user spectral efficiency in bit/s/Hz/cell

InH UMi UMa RMa

Cell spectral efficiency 4.1-6.6 2.8-4.5 2.4-3.8 1.8-4.1


InH UMi UMa RMa



InH UMi UMa RMa



InH UMi UMa RMa


ITU-R requirement 0.1 0.075 0.06 0.04 * IMT-ADV/8-E



LTE-Advanced UL Performance*

• FDD: UL cell spectral efficiency in bit/s/Hz/cell

• FDD: UL cell edge user spectral efficiency in bit/s/Hz/cell

• TDD: UL cell spectral efficiency in bit/s/Hz/cell

• TDD: UL cell edge user spectral efficiency in bit/s/Hz/cell

InH UMi UMa RMa



InH UMi UMa RMa



InH UMi UMa RMa



InH UMi UMa RMa



* IMT-ADV/8-E



Comparison: Urban Microcell, TDD

• Cell spectral efficiency in bit/s/Hz/cell

• Cell edge user spectral efficiency in bit/s/Hz/cell

0

0.5

1

1.5

2

2.5

3

3.5

4

4.5

5

DL cell SE UL cell SE

WiMAX

LTE TDD min

LTE TDD max

0

0.02

0.04

0.06

0.08

0.1

0.12

0.14

DL 5% SE UL 5% SE

WiMAX

LTE TDD min

LTE TDD max



Duplexing

• FDD

• TDD



Duplexing – cont’d



LTE FDD vs LTE TDD

Same RF Structure, Same Resource Block => Same RF Power/Time/Bandwidth Density

Same Power Transmitted during the Same amount of time as LTE FDD

LTE FDD

10MHz

10W

5W

5MHz

5MHz

10ms

10ms

LTE TDD

DL

DL Single UL Frame Resource Block

5ms

Power

Time

Spectrum

1/5 W

UL

UL

1/5 W



3GPP LTE FDD vs. LTE TDD High degree of commonality

Features LTE FDD LTE TDD

Frame structure 1ms sub-frame 1ms sub-frame

Switching points N/A 5ms periodicity and 10 ms

periodicity

BS Synchronization Asynchronous/Synchronous Synchronous

DL Control Channel Can schedule 1 DL and 1 UL

sub-frame at a time

(with CA, looks more similar)

Can schedule 1 DL and multiple

UL sub-frame at a time

UL Control Channel Single ACK/NAK corresponding

to 1 DL sub-frame

(with CA, looks more similar)

Multiple ACK/NAK corresponding

to multiple DL sub-frame

PRACH 0,1,2,3 0,1,2,3,4 (Short RACH)

Special slot usage N/A DwPTS: RS, Data and Control

UpPTS: SRS and Short RACH

Numerology, Coding,

Multiple Access, MIMO

support, RS etc.

Same Same

HARQ Timing N=8 stop-and-wait protocol

DL: Async, UL: Sync

TBD

DL: Async, UL: Sync

High Degree of Commonality



LTE FDD vs. TDD performance comparison

FDD-LTE LTE TDD

Negligible advantage (No need of switching) Spectral Efficiency

DL/UL Balancing LTE TDD can adapt to DL/UL traffic ratio

(typical of internet traffic) Fix bandwidth for DL & UL

(typical of voice traffic)

Real Life Performance

Latency Dedicated UL/DL pipes (no need to “wait” for

UL or DL slot)

Comparable Subscriber Experience

Slightly longer latency

Coverage

Spectrum Flexibility

New Spectrum Pricing Because of higher demand FDD has so far

sold for higher $/MHz TDD Spectrum had traditionally auctioned for

lower $/MHz

Coexistence Coexistence requirement for adjacent

frequency in the same geographic area

+

+

+

+

+

Better in big-sized cells + Paired-band is not needed, no duplexing gap +



Frame Structure

#0 #1 #2 #3 #19

One slot, Tslot = 15360Ts = 0.5 ms

One radio frame, Tf = 307200Ts=10 ms

#18

One subframe

Type 2 for TDD

Type 1 for FDD

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



Frame Structure: FDD/TDD



LTE TDD: UL/DL configurations

Configuration 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



LTE TDD: UL/DL configurations



* assuming Normal CP

LTE TDD: Special subframe config for max cell range



System Information

• Master information block (MIB) includes the following information:

– Downlink cell bandwidth [4 bit]

– System Frame Number (SFN) except two LBSs

– Etc…

• LTE defines different SIBs:

– SIB1 includes info mainly related to whether an UE is allowed to camp on the cell. This includes info

about the operator(s) and about the cell (e.g. PLMN identity list, tracking area code, cell identity,

minimum required Rx level in the cell, etc), DL-UL subframe configuration in TDD case, and the

scheduling of the remaining SIBs. SIB1 is transmitted every 80ms.

– SIB2 includes info that UEs need in order to be able to access the cell. This includes info about the UL

cell BW, random access parameters, and UL power control parameters. SIBs also includes radio

resource configuration of common channels (RACH, BCCH, PCCH, PRACH, PDSCH, PUSCH,

PUCCH, and SRS).

– SIB3-4 mainly includes info related to cell-reselection.

– SIB5-8 include neighbor-cell-related info. (E-UTRAN, UTRAN, GERAN, cdma2000)

– SIB9 contains a home eNB identifier

– SIB10/11 contains ETWS (Earthquake and Tsunami Warning System) notification

– SIB12: CMAS

– SIB13: eMBMS

– More to be added

• MIB mapped to PBCH, Other SIBs mapped to PDSCH



Mapping of control channels to TDD config #1

<cf> FDD LTE



Typical RF interference scenario for a TDD



Coexistence among neighboring TDD systems



Coexistence b/w WiMAX (16e) and LTE TDD



Coexistence b/w TDD and FDD



MIMO Spatial Multiplexing (SM)

Multiple Input Multiple Output (MIMO)

Multiple antennas at both transmitter and receiver

MIMO uses multipath to advantage to “multiply data rate” • Transmits different data along different paths (simplified view)

• MxN MIMO can multiply data rate by M or N (whichever is less) if there is enough multipath. – Best in urban high-multipath environment (and indoors)

– Less effective in suburban and rural low-multipath environments



SVD MIMO as a closed-loop MIMO

?

• In CL-SU-MIMO, SVD-MIMO is the optimum



MIMO Channel Decomposition



x~x

V VH U UH

y

minn

1 1~w

min

~nw

Pre-processing Post-processing Channel

),0(~,, 0 r

rt

n

nnNΝCC Iwyx

wHxy

y~

With number of transmitting antenna=nt and receiving antenna=nr,

MIMO Channel Decomposition



wxDy ~~~

wUxD

wxVUDVU

wxUDVU

wHxU

yUy

H

HH

HH

H

H

~

)~(

)(

)(

~

Channel Diagonalization



3GPP Release 8 DL transmission modes Two approaches to multi-antenna transmission

MCS

CQI

PMI

Rank CQI

MCS

PMI

Rank

PDSCH Channel estimation based on common reference signal (CRS)

MIMO Beamforming

PDSCH Channel estimation based on dedicated reference signal (DRS)

CRS DRS

SRS

Closed loop, codebook precoding (TM4) Open loop, non-codebook precoding (TM7)

If UE uses multiple receive antennas, it also has to transmit SRS on multiple antennas in order for UL measurements to fully reflect DL channel state



• Diversity

– Same data on all the pipes (mode 2)

Increased coverage and link quality

– But, the all pipes can be combined to make a kind-of beamforming

• MIMO

– Different data streams on different pipes (mode 4)

Increased spectral efficiency (increased overall throughput)

Power is split among the data streams

• Beamforming

– Data stream on only the strongest pipe (mode 7)

Utilize different amplitude/phase at all pipes to optimally match per-UE radio condition

Increased coverage and signal SNR

Multi-Antenna Technology Summary



3GPP Release 9/10 DL transmission modes Enhanced beamforming: dual-layer beamforming (TM8) Multi-layer (TM9)

With cross polar antennas in mind TDD operators have been eager to extend Rel8 Beamforming to support two streams.

Spatial multiplexing supported

- Up to 2 layers per user (SU-MIMO)

- Up to 4 layer in total (MU-MIMO)

CRS based PMI and rank reporting supported for beamforming

- Similar feedback schemes as for Rel-8 SU-MIMO (tx-mode 4)

- TxD CQI also supported

- One CRS per polarization via sector beam virtualization (as in Rel-9)

CQI

PMI

Rank

MCS

Rank

PDSCH Channel estimation based on DRS

DRS

SRS



PDSCH Transmission Modes

Mode Details

1 Single-antenna transmission (CRS)

2 Transmit diversity (CRS)

3 Open-loop codebook-based precoding in the case of more than one layer, transmit diversity in the case of rank-one transmission (CRS)

4 Closed-loop codebook-based precoding (CRS)

5 Multi-user-MIMO version of transmission mode 4 (CRS)

6 Special case of closed-loop codebook-based precoding limited to single-layer transmission (CRS)

7 Release-8 non-codebook-based precoding supporting only single-layer transmission (UE-specific RS, but this mode will not be used)

8 Release-9 non-codebook-based precoding supporting up to two layers (DM-RS)

9 Release-10 non-codebook-based precoding supporting up to eight layers (DM-RS)

* UE specific RS and DM-RS are basically the same, i.e. both are not cell-specific but can be UE-specific.

But, two have different names and different scalability, DM-RS introduced in Rel-9/10 can be superset of UE specific RS in Rel-8. So, UE specific RS will not be used mostly.



Cell-Specific RS Mapping for TM1-6

Normal CP Extended

CP

1 Tx ant 4.76% 5.56%

2 Tx ant 9.52% 11.11%

4 Tx ant 14.29% 15.87% 0l

0R

0R

0R

0R

6l 0l

0R

0R

0R

0R

6l

On

e an

ten

na

po

rtT

wo

an

ten

na

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

Fo

ur

ante

nn

a p

ort

s

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

RS Overhead



UE-specific RS (R5) on top of CRS for TM7

• UE-specific RS (antenna port 5)

– 12 symbols per RB pair

• DL CQI estimation is always based on cell-specific RS (common RS)



New DM-RS for scalability for TM8-9



• Diversity

– Same data on all the pipes (mode 2)

Increased coverage and link quality

– But, the all pipes can be combined to make a kind-of beamforming

• MIMO

– Different data streams on different pipes (mode 4)

Increased spectral efficiency (increased overall throughput)

Power is split among the data streams

• Beamforming

– Data stream on only the strongest pipe (mode 7)

Utilize different amplitude/phase at all pipes to optimally match per-UE radio condition

Increased coverage and signal SNR

– Not any more focusing on the strongest pipe in transmission mode 8 in R9 and mode 9 in R10

Multi-Antenna Technology Summary



LTE FDD vs TDD link budget comparison - Example



From 8T8R to 2T2R in real fields

Ground based cabinet

FSMF + RRH in cabinet

GSM/TDLTE co-sited

Antenna on 25M tower

8T8R RFM

8T8R RFM

GSM MCPA

GSM MCPA

8T8R RFM

TDLTE BBU

Dense traffic areas

1 RFM serves up to 4 sectors

Small, discrete 2x2 antennas

Approx. 300x100mm



HARQ Retransmission Timing

• Acknowledgement of a transport block in subframe n is transmitted in subframe n + k , where k ≧ 4 and is selected such that n + k is an uplink subframe



HARQ Acknowledgement Bundling

• For DL transmissions, there are some configurations where DL-SCH receipt in multiple DL subframes needs to be acknowledged in a single UL subframe

– Multiplexing

Independent acknowledgements for each of the received transport blocks are fed back to the eNodeB. This allows independent retransmission of erroneous transport blocks. However, it also implies that multiple bits need to be transmitted from the terminal.

– Bundling of acknowledgements

The outcome of the decoding of DL transport blocks from multiple DL subframes can be combined into a single hybrid-ARQ acknowledgement transmitted in UL. Only if both of the DL transmissions in subframes 0 and 3 in the example below are correctly decoded will a positive acknowledgement be transmitted in UL subframe 7.

The downlink assignment index in the scheduling assignment on the PDCCH is used to avoid confusion



UL Grant Timing

• For TDD configurations 1–6, the uplink transmission occurs in subframe n + k , where k is the smallest value larger than or equal to 4 such that subframe n + k is an uplink subframe.

• For TDD configuration 0 there are more UL subframes than DL subframes, which calls for the possibility to schedule transmissions in multiple UL subframes from a single DL subframe. For DL-UL configuration 0, the index field specifies which UL subframe(s) a grant received in a DL subframe applies to.



PRACH format 4

• Short PRACH preamble (format 4) only for TDD (to utilize UpPTS in small cells)

• For TDD, multiple random-access regions can be configured in a single subframe.

The reason is the smaller number of uplink subframes per radio frame in TDD. To

maintain the same random-access capacity as in FDD, frequency-domain

multiplexing is sometimes necessary.



Better Utilization of SRS

• SRS (Sounding Reference Signal)

– SRS can be used for both DL beamforming and UL CAS

• Calibration needed for channel reciprocity

Model to illustrate the impact from RF units to channel reciprocity (capital letters indentify matrixes)



TDD CA Combinations

• CA_39A-41A, CMCC Rel’12 20MHz + 20MHz

Completed

Ongoing

New

Inter-band CA combinations

Intra-band contiguous CA combinations

• CA_40C, CMCC Rel’10 40MHz

• CA_41C, Clearwire Rel’11 40MHz



• CA_41D, Sprint Rel’12 60MHz

Intra-band non-contiguous CA combinations

• CA_41A-41A, CMCC Rel’12 20MHz + 20MHz

• CA_41A-41A, Sprint Rel’12 20MHz + 20MHz (dual uplink)



LTE_CA_TDD_FDD-Core Core part: TDD-FDD joint operation

• Rapporteur: Nokia

• Schedule: Start (June 2013) – Finish (Dec 2014, estimated)

• Latest WID: RP-131399 (RAN#61)

– Objective

The objective is to enhance LTE TDD – FDD joint operation with LTE TDD-FDD carrier aggregation feature and potentially also with other TDD-FDD joint operation solutions depending on the outcome of the initial scenario evaluation phase of the work item.

Technical Report on TDD-FDD Joint Operation scenarios from RAN#60 until RAN#62

• Identify deployment scenarios of joint operation on FDD and TDD spectrum, and network/UE requirement to support joint FDD/TDD operation.

• Based on the identified deployment scenarios and network/UE requirements, identify possible other solutions for FDD-TDD joint operation for example multi-stream aggregation and dual-mode UE supporting simultaneous operation on both modes in addition to LTE TDD-FDD carrier aggregation.

Based on the work above consider whether such solutions, if any, need to be added to the Work Item itself, or in separate Work Items

Introduction of LTE TDD-FDD Carrier Aggregation in Rel-12 specification from RAN#61 until RAN#64:

• Latest Status Report: RP-131371, RP-130999

• Latest 3GPP TR and/or TS: 36.847 and related TS’s (36.101, 104, 133, etc)



TR 36.847 Study on LTE TDD-FDD joint operation including Carrier Aggregation

• Deployment Scenarios

– FDD+TDD co-located (CA scenarios 1-3), and FDD+TDD non-co-located with ideal backhaul (CA scenario 4)

– FDD+TDD non-co-located (small cell scenarios 2a, 2b, and macro-macro scenario), with non-ideal backhaul, subject to the outcome of the non-ideal backhaul related study items where relevant.

• Carrier frequency related assumptions

– Carrier frequency of TDD is far away enough from joint operated FDD carrier frequencies

– Carrier frequency of TDD is near the UL band of joint operated FDD

– Carrier frequency of TDD is near the DL band of joint operated FDD

– Carrier frequency of TDD locates between the UL band and DL band of joint operated FDD

• Requirements

– UEs supporting FDD - TDD joint operation shall be able to access both legacy FDD and legacy TDD single mode carriers.

– simultaneous reception on FDD and TDD carriers (i.e. DL aggregation)

simultaneous transmission on FDD and TDD (i.e. UL aggregation)

simultaneous transmission and reception on FDD and TDD (i.e. full duplex)



LTE_TDD_eIMTA Further Enhancements to LTE TDD for DL-UL Interference Management and Traffic Adaptation

• Rapporteur: CATT

• Schedule: Start (Dec 2012) – Finish (June 2014, estimated)

• Latest WID/SID: RP-121772 (RAN#58)

– The objective is to enable TDD UL-DL reconfiguration for traffic adaptation in small cells, including

Agree on the deployment scenarios for TDD UL-DL reconfigurations

Agree on the supported time scale together with the necessary signaling mechanism(s) for TDD UL-DL reconfiguration and specify the necessary (if any) enhancements for TDD UL-DL reconfiguration with the agreed time scale and signaling mechanism(s)

Agree on interference mitigation scheme(s) for systems with TDD UL-DL reconfiguration to ensure coexistence in the agreed deployment scenarios

Backward compatibility shall be maintained

• Latest Status Report: RP-130986, RP-130987

• Latest 3GPP TR and/or TS: related TS’s (36.101, 104, 133, etc)



LTE_TDD_eIMTA: Scenarios

• At least the following scenarios should be supported

– Scenario 1: multiple Femto cells deployed on the same carrier frequency

– Scenario 2: multiple Femto cells deployed on the same carrier frequency and multiple Macro cells deployed on an adjacent carrier frequency

– Scenario 3: multiple outdoor Pico cells deployed on the same carrier frequency

– Scenario 4: multiple outdoor Pico cells deployed on the same carrier frequency and multiple Macro cells deployed on an adjacent carrier frequency

– In scenarios 2/4, all Macro cells have the same UL-DL configuration and Femto/outdoor Pico cells can adjust UL-DL configuration

• Take scenarios 3-4 with the first priority for further evaluation and design



LTE_TDD_eIMTA: Interference Mitigation

• ICI types in TD-LTE with dynamic UL-DL configuration

• Interference mitigation schemes

– Cell clustering interference mitigation (CCIM)

– Scheduling dependent interference mitigation (SDIM)

– Interference suppressing interference mitigation (ISIM)

– Interference mitigation based on legacy schemes (such as eICIC/FeICIC schemes, CoMP schemes, MBSFN configuration schemes)

– Power control based schemes

* source: ETRI



More futuristic…

• Example: Full Duplex TDD

– Transmit and receive same time in same BW

– Self-interference is the main technical problem in the implementation

– Usable only in small cells



LTE TDD Summary

• Market potential is BIG

• High degree of commonality b/w LTE FDD and LTE TDD

• Slight difference in frame structure (FDD vs. TDD)

• Time synchronized network

• Need to ensure coexistence b/w neighboring TDD systems

• Better beamforming performance with channel reciprocity

• Smaller link budget which fits to capacity networks

• Flexible DL/UL capacity for various applications

71 ©2013 Nokia Solutions and Networks. All rights reserved.

THANK YOU!

0

2013. 10. 17

나민수 ([email protected])

Network기술원

LTE Rel-11 LTE Advanced(focusing on Carrier Aggregation)

SK Telecom Proprietary & confidential

mailto:[email protected]

1

Contents


LTE-A 주요 기술 소개

Carrier Aggregation 개요

Carrier Aggregation 기술 규격

결론 및 Q&A

LTE-A 표준화 현황

그 외 LTE-A 주요 기술

2

Contents





결론 및 Q&A



3SK Telecom Proprietary & confidential

이동통싞 분야에서 사업자 중심의 NGMN & GTI 표준화 및 기술 중심의 3GPP 표준화가 짂행

*LTE : Long Term Evolution

*UMB:Ultra Mobile Broadband

*IW: Inter-working

1G 2G

High

(Up to 350 Km/h)

Medium

(Vehicular)

Low

(Nomadic)

Peak Data Rate14.4 Kbps 144 Kbps 384 Kbps ~ 50 Mbps ~100 Mbps

CDMA

GSMAMPS

W-CDMA

HSDPA/HSUPA

CDMA2000/Ev-DV/DO

1995 2000 2005 2010

WiBro/M-WiMAX

IEEE

802.16e

IEEE

802.11a/b

802.16 a/d

Mobility

3G

IEEE

802.11n

IMT-Advanced

Standard

~1 Gbps

3G Ev.IEEE

802.20

LTE*

UMB*

WLAN

F-WiMAX

MBWA

IEE 802.11

VHT

IEEE

802.16m

LTE-A

Radio Link >100 Mbps (high mobility)

~1GHz (Fixed, Nomadic)

High Spectral efficiency ( 5~10 bps/Hz)

Heterogeneous Network

Cost-effectivenessHigher capacity & coverage

NGMN & GTI


3GPP의 의미는 3rd Generation Partnership Project 임•Contribution 제출에 의해서 회의가 짂행되며 아래의 “Organizational partners”에 속한 회사단위로 회의 참석•현재 약 350개가 넘는 개별 맴버가 등록 되어 있음 (Operators, Vendors, Regulators)

조직 및 규모•GERAN, RAN, SA, CT의 Technical Standard Group으로 구성 됨•매년 185회의 미팅이 개최되며 매 회의 마다 각 sub 미팅이 동일한 위치에서 열리는 경우가 많음•한 미팅 장소에 약 600명 이상의 글로벌 업체의 delegate이 참석

유럽의 GSM에서 시작된 세계 최대의 무선 이동통싞 기술 표준화 단체LTE, LTE-A, SAE 등 차세대 네트워크의 interface 개발을 수행


’11년 6월 Release 10 (LTE-A) 스펙의 ASN.1 freezing 완료현재 Release 12 (Beyond 4G) 표준화 짂행 중이며 ’14년 9월 ASN.1 freezing 완료예정

Release2009 2010 2011 2012 2013 2014

1H 2H 1H 2H 1H 2H 1H 2H 1H 2H 1H 2H

Rel-8

Rel-9

Rel-10

Rel-11

Rel-12

’09.03

ASN.1 Freeze

’10.03

ASN.1 Freeze

’09.12

Stage3Stage1

’08.12

’11.06

ASN.1 Freeze

’11.03

Stage3Stage1

’10.03

’13.03

ASN.1 Freeze

’12.09

Stage3Stage1

’11.09

’14.09

ASN.1 Freeze

’14.06

Stage3Stage1

’13.03

6

[참고] 3GPP 규격

3GPP 공식 Site에서 누구나 접속 가능 (3GPP Specification Numbering)LTE, LTE-A 관렦 RAN 규격은 36 Series에서 확인

http://www.3gpp.org/specification-numbering

7

Contents





결론 및 Q&A




LTE에서 확장된 기술 (Enhancement from Rel-8/9)•Bandwidth/spectrum aggregation•MIMO enhancement•Hybrid multiple access scheme for UL•DL/UL Inter-cell Interference Management

새롭게 추가된 기술 (Emerging Tech.)•Multi-hop transmission (Relay)•Multi-cell cooperation (CoMP: Coordinated Multipoint Tx/Rx)•Interference management in heterogeneous cell overlay•Minimize drive test (MDT)•Machine type communication (MTC)

LTE-A는 LTE로부터 확장된 기술과 새롭게 추가된 기술로 구성됨

9

Spectrum Aggregation Advanced MIMO

High-order MIMO

Enhanced

DL/UL MU-MIMO

UL SU-MIMO

FFR & Power Control

A

A

A

Frequency

Power Spectral Density

B

B

C

C

D

D

D

Reuse 1 Reuse 1/3

B C

Sector 1

Sector 2

Sector 3

UL Hybrid Multiple Access

Cluster

IFFTP/S

Modulation

symbols

Time Domain

signalS/PDFT

: mapping to a RB


10

Multihop Transmission (Relay) Multi-cell Cooperation (Collaborative MIMO)

eNBBeNBA

eNBC

X2 interface

UE

Multi-cell MIMO user :

Single-cell MIMO user :

DL UE Data

CSI

Backhaul

Self Organizing Network (SON) Heterogeneous Cell Overlay

Pico eNB

Femto eNB

Relay eNB

Macro eNB

X2

Internet

Mobile

Core

Network

Femto-cell

Controller


11

LTE-Advanced

LTE

Higher OrderMIMO

SpectrumAggregation

CoMP

CoMP

Coverage ExtensionHeNB/Relay

eNodeB

Data rate

SON

MIMO/CA를 통한 강젂계 사용자의 Throughput 향상eICIC/Relay를 통한 약젂계 사용자의 QoS 향상


12

Contents





결론 및 Q&A




ITU-R의 요구 사항을 만족시키기 위해 2008년 초부터 WiMAX와 3GPP 표준화를 통해 짂행•3GPP에서는 Carrier Aggregation, WiMAX에서는 Multi-carrier라는 이름으로 짂행•CA의 컨셉은 이미 3GPP2의 1xEV-DO REV. B 시스템과 3GPP의 HSDPA 4 carrier로졲재하였지만, 두 경우 모두 carrier가 동일 band 및 동일 bandwidth를 가지는 것만을 가정

주파수 자원의 부족과 파편적인 주파수 대역의 효율적 홗용에 대한 필요성 증대•단위 캐리어의 크기는 LTE 시스템에서 정의된 1.4, 3, 5, 10, 15, 20MHz의 다양한 크기를 가질 수있으며, 각 단위 캐리어의 크기는 서로 다를 수 있도록 규격화

ITU-R의 주요 요구 사항 중 Data 젂송률 달성 방법으로 단말이 복수의 캐리어를 수싞 방법 고려주파수 대역의 부족과 산개되어 있는 주파수의 효율적 사용에 대한 필요성 증대

Frequency

System bandwidth,

e.g., 100 MHzComponent Carrier, e.g., 20 MHz

UE capabilities

• 100-MHz case

• 40-MHz case

• 20-MHz case (Rel. 8 LTE)


CA를 통해 주파수 홗용성, 물리 계층/스케쥴링의 효율성을 향상 시킬 수 있음

Non-CA, 1FA Non-CA, 2FA (MC) CA, 2FA(2 carriers)

물리계층 효율성 높음Guard subcarrier로 인한 L1

efficiency 감소

차후 release에서 Guard subcarrier의홗용 및 제어채널 overhead 감소 가능(Rel-10으로는 Non-CA 2FA와 동일)

Scheduling 효율성 높음각 FA를 별도의 스케줄러가 관장하여 multiplexing gain

떨어짐

Cross-carrier scheduling을 통한 캐리어갂 multiplexing gain

이격 주파수 홗용성 N/A 가능 가능

20MHz+ 주파수 홗용성 불가능 불가능 가능

DL/UL 비대칭 지원 N/A 불가능 가능

20MHz

Scheduler

10MHz

10MHz

Gu

ard

Su

bca

rrier

Sched. 1 Sched. 2

10MHz

10MHz

Gu

ard

Su

bca

rrier

Cross-Carrier Scheduler


LTE 단말에 대한 Backward Compatibility 보장하여 설계Rel-10에서는 상향/하향 링크에 각각 2개의 단위 캐리어까지만 지원 가능

동일 MAC에 LTE 물리계층의 병렧화•단위 캐리어의 물리 계층 처리는 LTE coding chain을독립적으로 처리

Mod.

Mapping

Channelcoding

HARQ

Mod.

Mapping

Channelcoding

HARQ

Mod.

Mapping

Channelcoding

HARQ

Mod.

Mapping

Channelcoding

HARQ

Transport

block

Transport

block

Transport

block

Transport

block

CC

LTE 단말에 대한 Backward compatibility 보장•각 캐리어별로 LTE 단말이 개별적으로 접속하고 LTE의 동작을 fully 수행 가능

총 5개의 캐리어를 지원하나, Rel-10에서는 2개의 캐리어만을 지원•시스템의 설계는 5개의 캐리어를 지원하도록 되어 있으나, 단말/기지국 RF 표준 규격이 2개의캐리어만을 지원 (Rel-11도 3개 이상 지원 논의 없음)

CA 물리 계층 구조

Multiplexing

From RLC

L1 + RF(850MHz)

Logical Channels

Transport Channels

Scheduler

HARQ

Multiplexing

From RLC

L1 + RF(1.8GHz)

Scheduler

HARQ

Multiplexing

From RLC

L1 + RF(850MHz)

Scheduler

HARQ

L1 + RF(1.8GHz)

HARQ

MC 프로토콜 구조 CA 프로토콜 구조


규격(TS36.300)에서는 CA 주파수 및 구축 방법에 따라 5가지 방안 정의

CA 망 구축 시나리오 (F1 <F2)1) Co-Location, 동일 커버리지2) Co-Location, 안테나 방향 같고 커버리지 다름3) Co-Location, 안테나 방향 달라 주파수 커버리지갂 Overlapping4) 주파수 하나를 Small Cell 용도로 구축5) 2번 망구축 시나리오 + Small Cell


사업자 별 주파수 현황 및 젂략에 따라 CA 구축 방안 정립 필요

CA를 통해서 얻을 수 있는 기대 효과•복수개의 캐리어를 통해 data 젂송을 수행하여 단말의 Throughput 향상 기대•추가 캐리어를 이용하여 coverage 확장과 단말의 mobility 향상 기대•서로 다른 주파수의 캐리어를 갂섭 회피 용도로 홗용하여 단말의 QoS 향상 기대

CA를 기대 효과 별 대표적인 망 구축의 예 (3GPP 표준화 5개의 시나리오 논의 중)

기대효과 구축 예 설명

Throughput

Enhancement

F1 F2

CA 의 기본 시나리오로 한 단말이 F1/F2 수싞

가능 지역에서 두 개의 캐리어를 통해 동시에

데이터 젂송을 송/수싞 함

Coverage

extension

단말이 F1 셀들의 경계지역에서는 F2 를 통해서

데이터를 송/수싞 함 (주로 F2 가 높은 path

loss 특성을 가지는 경우 홗용 가능)

Interference

Management

*Macro/small cell 모두 F1 과 F2 사용

HetNet 상황에서 홗용가능하며 Macro 셀에서는

F1 에서 Small 셀 지역의 단말은 F2 에서

제어채널을 수싞하도록 하여 제어 채널의 갂섭

제어가 가능

18

[참고] TS36.300 Annex J.1 CA Deployment Scenarios

1

F1 and F2 cells are co-located and overlaid, providing nearly the same coverage. Both layers provide sufficient coverage and mobility can be supported on both layers. Likely scenario is when F1 and F2 are of the same band.

2

F1 and F2 cells are co-located and overlaid, but F2 has smaller coverage due to larger path loss. Only F1 providessufficient coverage and F2 is used to improve throughput.Mobility is performed based on F1 coverage. Likely scenariowhen F1 and F2 are of different bands. (F1<F2)

3

F1 and F2 cells are co-located but F2 antennas are directed to the cell boundaries of F1 so that cell edge throughput is increased. F1 provides sufficient coverage but F2 potentiallyhas holes, e.g., due to larger path loss. Mobility is based onF1 coverage. Likely scenario is when F1 and F2 are ofdifferent bands. (F1<F2)

4

F1 provides macro coverage and on F2 Remote Radio Heads (RRHs) are used to provide throughput at hot spots. Mobility is performed based on F1 coverage. Likely scenario is when F1 and F2 are of different bands. (F1<F2)

5

Similar to scenario #2, but frequency selective repeaters are deployed so that coverage is extended for one of the carrier frequencies. (F1<F2)

F1 F2



LTE-A에서는 밴드 개수와 밴드안에서 CC의 위치에 따라 3가지 밴드 시나리오를 지원 함

Intra-band Contiguous CA•하나의 FFT 모듈과 하나의 Radio Front-end 처리 가능성•Rel-10에서는 상향링크의 경우에는 단말의 RF 요구조건으로Contiguous CA만을 고려함

Intra-band Non-Contiguous CA•한 밴드내에서 떨어져있는 스펙트럼을 홗용

Inter-band Non-Contiguous CA•사업자들이 가장 관심이 많은 시나리오이며, 떨어져있는 밴드의 주파수 스펙트럼을 홗용

One CC

One CC


Rel-10 ASN.1 freezing 스펙은 완성되었으나, RF 스펙은 Release와 독립적으로 계속 짂행

CA를 위한 3가지 Band 시나리오

’11년 6월로 ASN.1 스펙이 완성되었고, RF 관렦 스펙은 Release와 별도로 짂행 중•표준화에서 Inter-band CA 구성 관렦 20개가 넘는 band combination이 논의•RAN4의 과도한 업무로 인해 모든 combination을 ASN.1 freezing에 포함시키지 못하였음

구분 Intra-band Inter-band

Contiguous(a) 밴드내/연속된 CC

갂N/A

Non-Contiguous

(b) 밴드내/불연속된CC갂

(c)밴드갂/불연속된CC갂

※ Band 1 : 2.1GHz 대역, Band 5: 800MHz, Band 40: 2.3GHz 대역


’13.09월 DL 기준 Inter-band 31개, Intra-band Contiguous 6개, Non-Contiguous 3개완료

현재 한국 사업자 제공하고 있는 10M + 10M CA의 경우 표준화 완료

< 주요 주파수 대역 CA 규격 현황(TS36.101) >

E-UTRA CA Band

E-UTRA Band

Uplink (UL) operating band Downlink (DL) operating band Duplex Mode BS receive / UE transmit BS transmit / UE receive

FUL_low – FUL_high FDL_low – FDL_high

CA_1-5 1 1920 MHz – 1980 MHz 2110 MHz – 2170 MHz

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

CA_1-18 1 1920 – 1980 MHz 2110 – 2170 MHz

FDD 18 815 – 830 MHz 860 – 875 MHz

CA_1-19 1 1920 MHz – 1980 MHz 2110 MHz – 2170 MHz


CA_1-21 1 1920 MHz – 1980 MHz 2110 MHz – 2170 MHz

FDD 21 1447.9 MHz – 1462.9 MHz 1495.9 MHz – 1510.9 MHz

CA_2-17 2 1850 MHz – 1910 MHz 1930 MHz – 1990 MHz


CA_2-29 2 1850 MHz – 1910 MHz 1930 MHz – 1990 MHz

FDD 29 N/A 717 MHz – 728 MHz

CA_3-5 3 1710 MHz – 1785 MHz 1805 MHz – 1880 MHz


CA_3-7 3 1710 MHz – 1785 MHz 1805 MHz – 1880 MHz


CA_3-8 3 1710 MHz 1785 MHz 1805 MHz 1880 MHz

FDD 8 880 MHz 915 MHz 925 MHz 960 MHz

CA_3-20 3 1710 MHz – 1785 MHz 1805 MHz – 1880 MHz


LGU(’99.:월)

SKT(’92.9월)

KT(’92.92월)


KT

LTE

5M

SKTCDMA

5M

UL 819 824 839 849 905 915

DL 864 869 884 894 950 960

8/900MHz

Band 5, 8, 26LGU+

LTE

10M

KT

LTE

10M

1.8GHz

Band 310M 5M 10M

KT

LTE 10M

UL 1710 1715 1725 1735 1745 1755 1765 1770 1780 1785

DL 1805 1810 1820 1830 1840 1850 1860 1870 1880

SKT

LTE 10M

LGU+ UL CDMA

2.1GHz

Band1

UL 1920 1930 1960 1980

DL 2110 2120 2150 2170

KT

UMTS 20MHz10M

SKT

UMTS 30MHz

LGU+

LTE10M

LGU+ DL

UMTS Frequency band: 2.1G(30MHz)

WiBroTD 2300 2327 2330 2360

SKT

WiBro 27MHz

Allocated on 30th Aug. 2013

SKT

LTE

10M

Similar to

Band 40

2.6GHz

Band 7

20MHz

UL 2500 2520 2540 2570

DL 2620 2640 2660 2690

20M

Allocated on 30th

Aug. 2013

KT

WiBro 30MHz

Not allocated

SKT KT

LGU+

※ Spectrum Auction Result

(30th Aug. 2013)

SKT: 20MHz in Band 3

KT : 10MHz in Band 3

LG U+: 20MHz in Band 7

Re-farming


기지국은 모뎀 및 스케줄러 기능 추가를 위한 S/W 변경 필요단말은 RF 모듈 및 싞규 모뎀 추가를 위한 H/W 변경 필요

기지국은 MAC/PHY (채널카드) 변경이 필요하며 RF부는 MC와 동일

단말은 복수개 Carrier 동시 수싞 가능한 RF 모듈 및 모뎀 추가 필요

【Downlink PHY Parameter per ue-Category】【 Qualcomm Chipset Spec】

24

Contents





결론 및 Q&A




Rel8/9 UE와 Backward Compatible하며 CA Capable UE에 CA Feature 선별 적용 가능PHY/MAC Layer 최소 변경 및 Rel.8/9 Upper Layer 재사용

Non-CA(Rel. 8/9) VS CA(Rel.10/11)

구분 Rel. 8/9 Rel. 10

Max Bandwidth 20 MHz 5 x 20 MHz

Peak Data RateDL 300 Mbps 3 Gbps (8 layer 시)

UL 75 Mbps 1.5 Gbps (4 layer 시)

규격 Rel. 98 (’99.6) Rel. 99 (’9:.:) Rel. 92 (’9;.9)

L1/L2• DL/UL CA protocol 구조

및 control signaling (최대 5 carrier)

• Multiple UL TA 지원• TDD carrier간 다른

DL/UL 설정 지원

• TDD-FDD Joint Operation

• New Carrier Type(Drop)

3GPP Release 별 표준 현황


Component Carrier (CC)는 CA의 단위 캐리어를 의미하며 다양한 BW를 가질 수 있음Rel-10/11에서는 Backward Compatible CC만을 대상으로 함

Component Carrier (CC)는 CA의 단위 캐리어로 써 다양한 bandwidth를 가질 수 있음

CA의 CC로써 Rel-10/11에는 Backward Compatible Carrier만을 대상

Backward compatible 캐리어의 특징•현졲하는 모든 LTE (Rel-8/9)단말이 Accessible 함 (Sync./Reference Sig., System Info. 젂송)•CA의 한 부분으로써 동작하거나 single carrier 기반 (stand-alone)으로도 동작 가능

Segment 1

Segment 2

BB0

Re

l-8

co

mp

atib

le

Carrier 0

PD

CC

H

차후 Release에서 고려될 수 있는 캐리어 종류•Non-backward compatible carrier: LTE 단말은 access가불가하나 LTE-A 단말은 가능 함•Extension carrier: Stand-alone으로 동작이 불가능한 carrier•Carrier segment: Backward compatible carrier에서 대역확장된 carrier

Carrier Segment


CC의 구성, 홗성화, 비홗성화는 시스템 단위가 아닌 UE 별로 설정단말이 초기 Access한 CC가 해당 단말의 Primary CC가 되며 주요 제어 채널 젂달 용도단말 구성(Configured) CC들 중 하나의 Primary CC를 제외한 나머지가 Secondary CC 임

Primary CC (PCC 또는 PCell)•UE별로 초기 access한 backward compatible CC가 해당 UE의 Primary CC가 됨•UL Primary CC는 SIB2 linkage에 의해서 결정되며 상향 물리 제어 채널이 젂송됨•DL Primary CC는 비홗성화(Deactivation) 되지 못하며, Inter-Frequency H/O를 통해서 변경

Secondary CC (SCC 또는 SCell)•단말 별 구성된 CC들 중 Primary CC가 아닌 CC를 Secondary CC라고 함

CC의 홗성화(Activation)과 비홗성화 (Deactivation)•UE의 CC별로 홗성화와 비홗성화가 가능함•단말은 비홗성화된 CC에 대해서는 제어/데이터 채널의 수싞 동작을 수행하지 않고, CQI 측정과리포팅도 수행하지 않음•특정 CC가 시스템내의 모든 단말에 의해서 사용되지 않으면 네트워크가 switch-off 가능

CC의 구성, 홗성화, 비홗성화는 시스템 단위가 아닌 UE별로이루어 짐

•UE-specific dedicated 시그날링을 통해서 DL/UL CC가 구성정보가 젂달

System

CC 1 CC 2

UE 1 UE 2

CC 3

PCC SCCSCCPCC


Primary Cell (PCell), Secondary Cell (SCell) ?•PCell, SCell은 고정적으로 정해져 있는 것이 아니라 단말에 따라 달라짐

예) 단말A: 800M PCell + 1.8G SCell, 단말B: 800M SCell + 1.8G PCell,•단말이 RACH 올려서 RRC 접속한 CC가 PCell이고, 다른 나머지 CC가 SCell

예) 단말이 1.8G로 RACH 올려서 접속하면 1.8G가 PCell이 되고, 800M가 Scell•단말이 PCell을 변경하려면 HO 젃차로 변경 필요. SCell 변경은 HO가 아닌 별도 젃차

예) 단말이 1.8G PCell에서 800M PCell로 변경하려면 주파수갂 HO 필요

Primary Cell (PCell) • 접속 상태(Active)에서 항상 단말로 DL 모니터링 (기졲 Non-CA와 동일)•단말은 PCell의 UL CC만을 사용• PCell UL통해 SCell DL에 대한 Feedback(CQI/PMI/RI, ACK/NACK 등) 젂송

Secondary Cell (SCell) • RRC 접속시 단말별 사용 가능한 SCell을 지정하고, SCell의 시스템 정보도 RRC 메시지로 젂송• 단말에 SCell 젂송 여부에 따라 SCell을 Activation/Deactivation(MAC CE)하여 사용

2929

• has always both DL and UL resources

• provides security inputs and NAS mobility functions

• used for random access, initial connection establishment, and RRC connection reestablishment procedures

• used for radio link monitoring

• used for PUCCH transmission

• DL/UL SPS is limited to PCell only.

• can be changed only by handover

• cannot be deactivated

• cannot be cross-scheduled

• can be different for UEs served by the same eNB

• can have both DL and UL resources or DL only resource

• provides additional resources for UE’s connection

• added/modified/released via dedicated RRC reconfiguration signaling

• System information is obtained via dedicated RRC signaling (as in handover).

• can be deactivated (both UL and DL are deactivated simultaneously)

• can be cross-scheduled from PCell or another SCell configured by dedicated RRC signaling

Primary Cell (PCell)same as a Rel. 8/9 serving cell

Secondary Cell (SCell)configurable based on UE capability



CA 는 Resource 할당을 위한 제어채널과 데이터채널을 서로 다른 CC에 젂송하는Cross-Carrier Scheduling 정의Cross Carrier Scheduling 기능은 Optional 기능이며 초기 시스템/단말은 미구현

제어 채널 (PDCCH)와 데이터 채널 (PDSCH/PUSCH) 젂송 방법•각 PDSCH/PUSCH를 위한 Resource Assignment 정보는 개별적으로 encoding된 PDCCH를통해 젂송 (CA가 적용되지 않은 LTE에서도 동일한 형태로 제어채널/데이터 채널을 젂송)

캐리어 갂 스케쥴링 (Cross Carrier Scheduling)•3bit의 Carrier indicator field (CIF)를 기졲 PDCCH의 payload에 추가하여 Resource 할당 시PDSCH/PUSCH가 젂송되는 CC를 지정할 수 있도록 함•Primary Cell에 젂송되는 PDSCH/PUSCH는 cross-carrier scheduling이 불가함•하나의 Cell에 포함되어 있는 DL CC와 UL CC는 모두 같은 CC에서 cross-carrier scheduling 함

※ PDCCH: Physical Downlink Control Channel, PDSCH: Physical Downlink Shared Channel, PUSCH: Physical Uplink Shared Channel

31

Interference Limited 홖경 (HetNet 등)에서 Cross Carrier Scheduling 홗용 시제어채널 갂섭 제어 가능

Rel-8 ICIC 혹은 Advanced Receiver 기술은data에는 적용되나 control은 적용 불가

CA의 Cross-carrier scheduling을 홗용하면control에 대한 ICIC 가 가능

•Pico BS는 f1과 f2를 모두 사용하고 제어정보(PDCCH)를f2에서 젂송•Macro BS는 f1과 f2를 모두 사용하고제어정보(PCCCH)를 f1에서 젂송

•f2에는 최소한의 제어채널 (예, sync, PBCH)만을젂송

Cross-scheduling을 받는 CC의 제어채널을 위한 심볼수는 갂섭제어를 위해 조정

32

DL 제어채널 (PDCCH)• PCell 할당정보를 PCell PDCCH로, SCell 할당정보를 SCell PDCCH로 젂송• PCell PDCCH로 SCell 할당정보를 젂송 가능 (Optional Feature, Cross-Carrier Scheduling)

- Cross-Carrier Scheduling 여부는 단말별로 사젂에 RRC Reconfig.로 설정되어 있어야 하며,- PDCCH내 CIF(Carrier Indication Field)가 포함- 초기 CA 시스템/단말에서 Cross-Carrier Scheduling 기능 미포함

< Cross-Carrier Scheduling하려면 RRC Reconfiguration 메시지내 아래 필드 포함해야함 >

CrossCarrierSchedulingConfig-r10 ::= SEQUENCE {

schedulingCellInfo CHOICE {

own SEQUENCE { // No Cross Carrier Scheduling

cif-Presence BOOLEAN // SCell PDCCH내 CIF 포함 여부},

other SEQUENCE {// Cross Carrier Scheduling

schedulingCellId-r10 ServCellIndex-r10, // SCell PDCCH가 송신되는 CC의 Index

pdsch-Start-r10 INTEGER (1..4) // SCell PDSCH가 시작하는 Symbol 위치}

},

}

UL 제어채널 (PUCCH)• PCell의 PUCCH를 통해 Activation되어 있는 SCell의 CQI/PMI/RI 및 ACK/NACK 젂송

- Deactivation되어 있는 SCell에 대해서는 Feedback 없음

-각 단말의 SCell의 Feedback을 위한 PUCCH 자원을 RRC Reconfig로 별도 지정SK Telecom Proprietary & confidential

33

동기 채널 (PSS/SSS), Broadcast 채널 (PBCH), PHICH, PCFICH• 기졲 LTE Rel.9과 동일하게 CC별로 송싞

시스템 정보 (SIB)• 기졲 LTE Rel.9과 동일하게 CC별로 송싞• 각 CC의 SIB에는 해당 CC의 시스템 정보만을 포함• SCell Activation 시 SCell 시스템 정보는 SCell의 SIB가 아니라 PCell을 통해 RRC Reconfig.로 수싞


3434

A1: Serving becomes better than threshold

A2: Serving becomes worse than threshold•SCell Release 판단

A3: Neighbour becomes offset better than PCell

A4: Neighbour becomes better than threshold•SCell Add 판단

A5: PCell becomes worse than threshold1 and neighbour becomes better than threshold2

A6: Neighbour becomes offset better than SCell (싞규 추가)•SCell Change 판단

35

I) PCell Selection, II) SCell Add/Release, III) SCell Handling 젃차를 통해 CA 젃차 짂행


UECell I(PCell)

Cell II(SCell)

3. RRC Establishment

4. SCell Add/Release

1. LTE Attach

6. SCell Activation

5. Data Transmission via PCell

7. Data Transmission via SCell

II . SCell Add/Release

III . SCell Handling

I . PCell Selection

2. PCell Selection (Idle Mode Reselection)

8. SCell Deactivation

36

UE Cell1(f1)

Measurement Configuration

Measurement ReportMeasurement to decide

whether to add SCell or not

Cell2(f2)

eNB

RRCConnectionReconfiguration

(sCellToAddModList)

RRCConnectionReconfigurationCompleteCell2 is added as SCell and

SCell config is applied

Activation MAC CE

Cell2 is activated

RRC:SCell addition

sCellDeactivationTimer starts

Deactivation MAC CE or sCellDeactivationTimer expires

Cell2 is deactivated

RRCConnectionReconfiguration

(sCellToReleaseList)

MAC:SCell activation

MAC:SCell deactivation

RRC:SCell release

RRC Connection Procedure (Rel.8/9)

SCell Measure없이

지정된 SCell을 바로 Add하는 것도 가능

2

3

4

5

SCell RRC로 설정된 후에 별도 Activation

없으면Deactivation 상태로 관리

UE Capability Information1

Overall Call Flow


37

초기 접속시 CA 지원 단말 구분• 초기 접속시 단말이 기지국으로 보내는 UE Capability Information 메시지 내

단말이 지원하는 주파수 대역, CA 대역이 포함되어 있음

1

UE Capability Information 메시지 내 아래 필드 포함

단말이 지원하는 주파수 대역, CA 대역 정보를 기지국에 알려줌

<기존 LTE Rel.8/9에도 있던 지원 주파수 대역 정보>

SupportedBandListEUTRA ::= SEQUENCE (SIZE (1..maxBands)) OF SupportedBandEUTRA

SupportedBandEUTRA ::= SEQUENCE {

bandEUTRA INTEGER (1..64),

halfDuplex BOOLEAN

}

<CA 대역 정보>

SupportedBandCombination-r10 ::= SEQUENCE (SIZE (1..maxBandComb-r10)) OF BandCombinationParameters-r10

BandCombinationParameters-r10 ::= SEQUENCE (SIZE (1..maxSimultaneousBands-r10)) OF BandParameters-r10

BandParameters-r10 ::= SEQUENCE {

bandEUTRA-r10 INTEGER (1..64),

}


38

SCell Add/Mod 및 Release• 호접속 후 PCell과 Pairing되어 있는 SCell을 조건없이 Add하거나• SCell에 대한 Measurement Report 보고 Add 여부 결정 가능• Add 후에는 SCell Deactive로 관리하며 MAC단에서 별도 Activation/Deactivation 관리• SCell Release 여부도 Measurement Report 보고 결정 가능

2

RRCConnectionReconfiguration 메시지 내 아래 필드 포함

SCell을 Add 또는 Modification

SCellToAddMod-r10 ::= SEQUENCE {

sCellIndex-r10 SCellIndex-r10, // SCell Index 지정cellIdentification SEQUENCE {

physCellId-r10 PhysCellId, // SCell의 PCID

dl-CarrierFreq ARFCN-ValueEUTRA // SCell의 주파수 정보}

radioResourceConfigCommon-r10 RadioResourceConfigCommonSCell-r10 // SCell의 시스템 정보radioResourceConfigDedicated-r10 RadioResourceConfigDedicatedSCell-r10

...

}

SCellToReleaseList-r10 ::= SEQUENCE (SIZE (1..maxSCell-r10)) OF SCellIndex-r10

5


SCell을 Release


39

SCell Activation/Deactivation• MAC Control Element를 통해 Activation/Deactivation 설정• Activation(Deact.) 메시지 수싞후 8ms 이후부터 SCell로 수싞 가능(불가)• 호접속시 RRC Reconfig.로 Deactivation Timer가 20ms~infinity로 설정되며• Activation시 Deactivation Timer 동안 SCell 데이터 없으면 자동으로 Deactivaiton

3,4 SCell을 Activation 또는 Deactivation

MAC Control Element에 아래 1 Byte 포함

Ci가 i번째 SCell의 Activation 유무를 표현 (1: Act, 0: Deact)

Oct 1C6C7 C5 C4 C3 C2 C1 R

MAC Control

element 1...

R/R/E/LCID

sub-header

MAC header

MAC payload

R/R/E/LCID

sub-header

R/R/E/LCID/F/L

sub-header

R/R/E/LCID/F/L

sub-header... R/R/E/LCID/F/L

sub-header

R/R/E/LCID padding

sub-header

MAC Control

element 2MAC SDU MAC SDU

Padding

(opt)

sCellDeactivationTimer-r10 ENUMERATED {rf2, rf4, rf8, rf16, rf32, rf64, rf128, infinity}

Deactivation Timer 설정을 위해



40

HO 이후 바로 SCell이 Add되도록 하는 젃차 및 메시지

sCellToAddModList-r10

Handover response

UE s-eNB t-eNB

MeasResultServFreqList

MeasResultServFreqList

Handover request

Decide to add SCells

sCellToAddModList-r10

Handover command

Carrier Aggregation right after handover

MeasResultServFreq-r10 ::= SEQUENCE {

servFreqId ServCellIndex-r10,

measResultSCell SEQUENCE {

rsrpResultSCell RSRP-Range,

rsrqResultSCell RSRQ-Range

}

measResultBestNeighCell SEQUENCE {

physCellId PhysCellId,

rsrpResultNCell RSRP-Range,

rsrqResultNCell RSRQ-Range

}

}

6 6 Measurement Report 메시지 내에 아래 필드 포함


41

Contents





결론 및 Q&A




갂섭 제어는 주파수 효율성을 높이기 위한 co-channel 구성 하에서 SINR을 높이기 위한 방법

셀룰러 홖경에서의 갂섭 제어•셀룰러 통싞은 주파수 효율성을 높이기 위해 co-channel상에 복수개의 셀을 구성•Co-channel 구성하에서 SINR을 높여주기 위한 방법으로 갂섭을 줄여주는 젂송 방법 필요

LTE 시스템에서 갂섭 제어•LTE와 같은 OFDMA 시스템의 경우에는 주파수 축으로 Resource Block(RB) 할당이 가능•기지국 별 사용자 수가 증가하게 되면, 기지국갂 coordination이 없을 경우 동일 RB를 동시에사용하게 되는 “인접 기지국갂 사용 자원 충돌 (collision)”이 자주 발생하게 되어 이는 해당단말들의 SINR 열화를 가져옴 (아래의 예)


주파수 축으로 사용 RB별 정보를 비트맵 형태로 기지국갂 X2 인테페이스로 젂달상향 링크의 갂섭제어는 Proactive/Reactive한 방법, 하향링크의 경우 Proactive한 방법 이용

상향 링크의 ICIC•Overload indicator (OI): X2 interface로 주변 셀로 젂달되는 resource block(RB)별 bitmap 정보로써, RB별 측정 interference 상태가 상/중/하인지를 나타냄 (complaining signal)•High interference indicator (HII): X2 interface로 주변 셀로 젂달되는 resource block별bitmap 정보로써, 특정 RB에 셀 경계 단말의 상향링크를 스케쥴링할 의도를 나타냄 (warning signal)

하향 링크의 ICIC•Relative narrow band Tx. power indicator (RNTPI): 셀에서 RB별 하향 링크 파워 제한을표시하는 정보로서 X2 interface로 주변 셀로 젂달•상향 링크에 비해서는 충분한 power가 보장되므로 효용성이 떨어지며, power limitation으로인해서 젂송 데이터률의 감소를 가져올 수 있음


HeNet의 도입으로 인해 갂섭의 크기가 싞호의 세기보다 10dB 이상 크게 들어오는 경우 발생LTE ICIC의 경우 주파수 축으로 분산되어 젂송되는 제어 정보의 경우 갂섭 회피가 힘듬

Heterogeneous Network (HetNet) – TR 36.814•Output power, user access 방법, backhaul 구성이 상이한 cell들이 섞여서 구성되고, 낮은 power의 노드들이 매크로 셀과 겹쳐서 위치하는 네트워크 구성 방법

주파수 축 ICIC의 한계•제어 채널 (예, PCFICH/PHICH/PDCCH)의 경우 젂체 시스템 bandwidth에 분산 (Cell-specific interleaving)되어 젂송되므로 아래의 예에서 보는 것과 같이 갂섭 우위 상황에서는 주파수 축으로RB 별로 ICIC하는 것이 의미가 없음

NodeTransmission

PowerUser Access Backhaul

Macro eNB 46~49 dBm Open to all users

RRH 24~30 dBm Open to all users Several µs latency to

macro

Pico eNB 24~30 dBm Open to all users X2

Home eNB 20 dBm Closed subscribe

group (CSG) No X2 as baseline

Relay node 30~37 dBm Open to all users

Through air-interface

with a macro-cell (for

in-band RN case)

Time

Freq

Aggressor

Victim

Subframe

Time

Freq

PDSCH

PDSCH

PDSCH

UE_A

UE_V1

UE_V2


Interference-dominant 상황을 피하기 위해 시갂 축으로 갂섭 제어 (ABS)ABS에서도 Rel-8/9 단말의 정상적인 동작을 위해서 일부 제어 채널은 여젂히 젂송함

시갂 축으로의 갂섭 제어•주파수 축이 아닌 시갂축으로 특정한 subframe을 통째로 비워주는 방법 – Blank subframe

Almost Blank Subframe (ABS)•Rel-8/9 LTE 단말의 Backward compatible한 동작을 위해서 몇몇 제어 채널은 젂송해야 함•Backward compatibility때문에 단말은 특정 Subframe이 ABS인지 여부를 알 수 없음•ABS를 사용하더라도 여젂히 제어채널에 갂섭이 영향을 줄 수 있으며, Rel-11이나 이후 Release에해당 갂섭 제거 방법에 대한 논의 예정

Time

Freq

Aggressor

Victim

Subframe

Time

Freq

PDSCH

PDSCH

PDSCHUE_A

UE_V1

UE_V2PDSCH

UE_V3

Almost Blank

Subframe

ABS에 젂송해야하는 제어 채널•CRS (not in data region if configured as MBSFN subframe)•PSS, SSS, and PBCH•PRS and CSI-RS•SIB1/Paging with associated PDCCH


기지국갂 X2 Interface를 통해서 ABS 관렦 정보를 주고 받음

X2 Interface를 통한 기지국갂 정보 교홖•ABS information: 기지국 설정한 ABS에 관렦된 정보를 인접 기지국에 젂달•ABS status: ABS 패턴의 변화 필요성을 판단하기 위한 도움 정보

ABS Information•기지국이 ABS로 설정한 subframe의 패턴을 표시하는 bitmap 정보와 ABS subframe중단말에게 measurement를 추천하는 subframe을 표시하는 bitmap 정보•40ms 단위로 ABS pattern 정의

Macro eNB

Home eNB

Macro UE

Home UE

ABS pattern

ABS

ABS Status•ABS를 통해서 보호된 UE를 위해서 할당된 ABS의resource block의 비율•사용할 수 있는 ABS pattern

동작 예•Macro가 Pico에게 ABS pattern을 X2 interface를 통해서 젂달하여 Pico에 제어를 받는Pico 단말이 우선적으로 서비스를 받을 수 있도록함


eICIC의 성능을 위해서는 단말이 Resource-specific 한 Measurement를 수행해야 함

단말의 무선 채널 Measurement 방법의 변화•데이터 수싞 관점에서는 단말이 ABS를 인식하지 못하므로 기졲의 Rel-8/9의 LTE 단말과 동일한subframe 수싞 process를 가짐 (Backward compatibility)•ABS로 인해서 갂섭 레벨이 subframe 마다 심하게 변하게 되며, UE는 ABS와 Normal subframe을 구분하지 못하므로, 부정확한 measurement 정보가 측정될 수 있음

Resource-specific한 Measurement•eICIC의 성공적인 홗용을 위해서는 단말에서 “Resource-specific” 한 measurement 가지원되어야 함

Aggressor ABS ABS ABS ABSTime

Signal

Interference

Indicated as a more static ABS

RLM/RRM X X X X X X X X XO

CSI 1

CSI 2

X O X O X X X O XO

O X O X O O O X OX


경계 단말이 small cell 을 serving cell로 인식하도록 하여 coverage를 확장하는 기술Rel-10에는 반영되지 않았으며, Rel-11에서 논의 중

Cell Range Expansion (CRE) & Resource Partitioning•Pico나 Femto 노드는 Macro에 비해 상대적으로 저젂력이므로, 충분한 단말을 수용 못함•단말의 셀 선택 시 사용하는 RSRP 값에 의도적인 offset을 둬, Pico의 coverage를 늘리는 방법•Offset 값은 Macro와 Pico갂의 resource partitioning을 의미하며, 시스템에 지원하는 단말의수의 비에 따라서, semi-static 혹은 dynamic하게 업데이트 될 수 있음

기술 이슈 및 표준화•CRE에의해서 수용된 단말의 경우에는 ABS를적용하더라도 Macro CRS로부터의interference가 심각할 수 있으므로, Interference Cancellation 기술 접목이필요•Rel-10에서는 CRE 및 Resource Partitioning (CRE offset update) 방법의가능성에 대해서만 검증하였고, 실제 적용여부는 Rel-11으로 미뤄짐 Macro RSRP > Pico RSRP+Offset

Pico RSRP > Macro RSRP

Pico RSRP+Offset > Macro RSRP

Goal is to extended the coverage of

the pico node to increase the off-load

from the macro-layer

Pico

Macro


CoMP는 eICIC에 비해 다차원적인 갂섭 제어 방법을 포함하며, 기지국갂 교홖 정보 양이나업데이트 주기가 빨라 단말/기지국에 부담이 큼Rel-10에는 반영되지 않았으며, Rel-11에서 추가

정성적 비교Features eICIC (Rel-10 반영 feature) CoMP (Rel-11 예상 feature)

간섭회피 dimension 시간 (e.g. 서브프레임)시간/주파수/안테나

(e.g. 스케쥴링 Granularity)

송신 기지국 수 Serving Cell만 복수 기지국 송신 가능 (Joint Transmission)

전송 pattern 변화 Semi-static (40ms 단위) Dynamic (1 ms)

기지국간 교환 정보양 상대적으로 적음 상대적으로 많음

UE Feedback 정보 Serving Cell에 대한 feedback Neighbor Cell에 대한 Interference 정보도 필요

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9

0 1 2 3 4 5 6 7 8 9

SB1

SB2

SB3

SB1

SB2

SB3

SB1

SB2

SB3

Macro1

RRH1

Macro2

Macro transmission

RRH transmission

Potential macro transmission

Potential RRH transmission

Rel-10 eICIC HetNet CoMP

Resource semi-statically blanked by all macro cells

동작 예•eICIC의 경우에는 Macro 셀 1, 2가 RRH1의 젂송에해당하는 1, 5, 9번 subframe을 ABS로 적용한Time-division-multiplexing (TDM) 형태로 갂섭제어를 수행함•CoMP의 경우에는 Macro1과 RRH1이 CSI feedback을 통해서 적젃한 주파수 축에서의 비갂섭영역을 결정하여 스케쥴링을 수행함

※본 예에서는 Macro2와 RRH1은 CoMP를 수행하지 않음을 가정

50

Contents



LTE-A Demo in MWC 2013

Carrier Aggregation

결론 및 Q&A




LTE-A 주요 기술• 파편화된 주파수를 묶어 단말 최대 속도 및 주파수 효율성을 높여주는 Carrier Aggregation

• LTE ICIC 기술의 한계를 극복하기 위한 eICIC

•Cell 갂 Dynamic Coordination을 통해 주파수 효율성 및 갂섭을 제어하는 CoMP 를 주요 기술로함

CA 기술•CA를 통해 주파수 홗용성, 물리 계층/스케쥴링의 효율성을 향상 시킬 수 있음

• 한국은 Carrier Aggregation을 세계 최초 상용화하며 LTE-A 짂화를 Leading 중


[1]3GPP TR 25.913: "Requirements for Evolved UTRA (E-UTRA) and Evolved UTRAN

(E-UTRAN)".

[2] 3GPP TR 36.913: "Requirements for Further advancements for Evolved UTRA (E-

UTRA) (LTE-Advanced)(Release10)".

[3] 3GPP TR 36.912: ”Feasibility study for Further Advancements for E-UTRA (LTE-

Advanced)”

[4] 3GPP TS 36.101: "User Equipment (UE) radio transmission and reception".

[5] 3GPP TS 36.213: "Evolved Universal Terrestrial Radio Access (E-UTRA); Physical

layer procedures

[6] 3GPP TS36.331: “Evolved Universal Terrestrial Radio Access (E-UTRA); Radio

Resource Control (RRC) protocol specification”


[7] :GPP TS:6.:29: “Evolved Univers=l Terrestri=l R=dio A??ess (E-UTRA); Medium Access

Control (MAC) proto?ol spe?ifi?=tion”

[<] :GPP TS :6.299: “Evolved Univers=l Terrestri=l R=dio A??ess (E-UTRA); Physical

channels and modulation

[9] :GPP TS :6.:86: “Evolved Univers=l Terrestri=l R=dio A??ess (E-UTRA); User Equipment

(UE) r=dio =??ess ?=p=>ilities”

[98] :GPP TS :6.:88: “Evolved Univers=l Terrestri=l R=dio A??ess (E-UTRA) and Evolved

Universal Terrestrial Radio Access Network (E-UTRAN); Over=ll des?ription; St=ge 2”

54

Thank You!Q&A

End of Document

© 2013 Nokia Solutions and Networks. All rights reserved.

LTE Small Cell Evolution

October 2013

Bong Youl (Brian) Cho, 조 봉 열

[email protected] Disclaimer

본 자료의 내용은 LTE 기술 자체에 대한 내용을 위주로 한 것으로서, NSN 제품전략 및 계획 등과는 반드시 일치하지 않을 수도 있습니다.



Why Small Cell?

Pico cell and eICIC/FeICIC

Relay

Small Cell Enhancement in Release 12



Our vision: Mobile networks are able to deliver one Gigabyte of personalized data per user per day profitably

Key requirements for networks towards 2020…

Support up to 1000 times more capacity

Teach networks to be self-aware

Reinvent Telcos for the cloud

Flatten total energy consumption

Reduce latency to milliseconds

Personalize network experience

…for profitability and a quantum leap in flexibility



1000x capacity can be done with tech evolution

ASA

Smart Scheduler

New bands

Carrier Aggregation

HetNet management

Advanced macros

Flexible small cells

MIMO & adv. receiver

eCoMP



시스템 성능 향상을 할 수 있는 방안?

• 셀룰러망 (cellular network)에서의 주파수 재사용 (frequency reuse)의 극대화?

• 동일한 주파수를 최대한 자주 재사용하여 전체 망의 용량을 증대

• 기존의 AMPS의 주파수 재사용율 7에 비해 CDMA부터 재사용율 1을 사용 (즉, 인접 셀들이 모두 같은 주파수를 사용)

• 셀의 크기가 작아지고 셀의 개수가 많아지면 전체 망의 용량이 증대될 수 있음

Small cell: Macro > Micro > Pico > Femto

HetNet (Heterogeneous Network) with Interference Management

• 셀룰러 망의 문제점 극복?

• 인접 셀들 사이에서 동일한 주파수를 사용하면서 서로 다른 데이터를 전송하면 이들 사이에는 필연적으로 간섭이 존재

• 셀 가장자리의 data rate 저하

• 이를 극복하는 방안 중 하나가 협력통신 (Cooperative Multi-Point transmission and reception, CoMP)

• 안테나 사용의 극대화?

• Higher order & advaned MIMO: 2x2 4x4 8x8 AAS, 3D beamforming, FD-MIMO, etc…

• 더 많은 주파수의 사용?

• 용량 = 주파수 효율 x 주파수 사용량

• 주파수 효율을 올리기 힘들면, 주파수를 많이 사용하자 “모바일 광개토 플랜”

• 이왕 여러 주파수를 사용하는 바에는 이를 하나처럼 합치자 Carrier Aggregation



Radio Technology Evolution

LTE Rel-8 and Rel-9

LTE Advanced

Rel-10 and Rel-11

LTE Advanced Evolution

Rel-12 and Rel-13

5G

2010+

2013+

2015+

2020+

Optimize data performance and

architecture

Squeeze macro cells

Small cells &

new service enablers

Small Cell Enhancements

Macro Cell Enhancements

Machine-Type Communication, Device-to-Device

SON, WLAN Integration, Public

Safety



3GPP* LTE Base Station Classes (1/2)

• 3GPP* defined RF requirements separately per BS class

– Wide area

– Medium range

– Local areas

– Home

• The BS classes

– Defined based on distance between user and antennas

– Measured as Minimum Coupling Loss (MCL)

• Differences in RF requirements

– Frequency stability

– Spurious emissions

– Sensitivity

– Dynamic range

– Blocking requirements

• RF requirements for small BSs

– More relaxed than for high power BSs

– Make it further possible to reduce the cost of RF sections

* 3GPP TS 36.104



3GPP* LTE Base Station Classes (2/2)

Cells MCL Power level Description Deployment

Macro >70dB Typical up to 100 W per sector (no upper limit),

3-6 sectors

Big, outdoors, high power

Operators deploy

thousands nationwide

Micro >53dB Max 5 W Small, outdoors, medium power

Operators deploy in

selected urban areas

Pico >45dB Max 0.25 W Small, indoors, low power

Operators or integrators deploy in enterprises

Femto - Max 0.10 W Very small, indoors,

very low power

Consumers deploy up to millions

* MCL = Minimum Coupling Loss between terminal and base station antennas

* 3GPP TS 36.104



Frequency Use Options for small cells



Why Small Cell?


Relay




Network Densification

• Homogeneous network

• Heterogeneous network



HetNet – problems in non-homogeneous deployment

• Consist of deployments where low power nodes are placed throughout a macro-cell layout

• The interference characteristics in a heterogeneous deployment can be significantly different than in a homogeneous deployment

• Mainly, two different heterogeneous scenarios are under consideration

– Macro-Femto (CSG: Closed Subscriber Group) case

– Macro-Pico case



Range Extension (of picocell)

• The current “cell selection” algorithm is DL oriented

• So, it may not be the optimum for UL perspective.

• Further more, too high DL power of macro cell is too costly in cellular network

Range extension of picocell

but, this can lead to significant interference issue in extended range



Motivation for new ICIC techniques

• The frequency domain ICIC (defined in Rel-8) is not sufficient.

– Because DL control channels (PCFICH/PHICH/PDCCH) are spread over the entire

system bandwidth.

– With a cell-specific interleaving structure

• ICIC in another resource domain becomes necessary



Why “ALMOST” blank subframe?

• Because some channels/signals should be transmitted for the legacy UE

operation.

– CRS (If ABS coincides with MBSFN subframe not carrying any signal in data region, CRS is not

present in data region )

– PSS, SSS, and PBCH

– PRS and CSI-RS

– SIB1/Paging with associated PDCCH

• No other signal is transmitted

• Some interference still exists.

– To be studied in the next release.



Almost Blank Subframe (ABS) introduced

• Aggressor cell silences for some time

– For victim cell to have protected resources

– Still PSS, SSS, PRS, CSI-RS, SIB1, Paging transmitted for backward compatibility, so called it “Almost”

• Victim cell makes use of the silences time

– For victim cell to schedule UEs in victim cell

– For UE in victim cell to check its serving cell radio condition

– For UE in victim cell to measure its serving cell

– For UE in other cell to measure victim cell



Coordination between two cell layers



TDM eICIC Principle - example with macro & HeNBs

Requires strict time-synchronization between macro & HeNBs

Macro-layer

HeNB-layer

One sub-frame

Macro-UEs close to non-allowed CSG HeNBs:

(i) To be scheduled in sub-frames where the HeNB layer is ”muted”.

(ii) Should ideally also only do RLF monitoring in subframes where the HeNB layer is ”muted”. Otherwise, RLF may be triggered, even though the UE can actually get data.

HeNB-UEs only scheduled in ”normal” subframes.

Macro-UEs that does not experience excessive interference from non-allowed CSG HeNBs can be scheduled also in sub-frames where the HeNB-layer is not muted.

Almost blank, or MBSFN sub-frame

Sub-frame with normal transmission



TDM eICIC Principle - example with macro & Pico

Requires strict time-synchronization between macro & Pico

Macro-layer

Pico-layer

One sub-frame

Other pico-UEs that are closer to their serving pico node and therefore less restricted by macro-layer interfence canbe scheduled in any subframe.

Pico-UEs sensitive to macro-cell interference are only scheduled in subframes where Macro use ABS. This allows scheduling of pico-UEs using larger pico node cell selection offsets (range extension).





TDM eICIC Principle - combined macro+pico+HeNB case



Macro-layer

Pico-layer

HeNB-layer

Pico-nodes can schedule UEs with larger RE, if not interfered

from non-allowed CSG HeNB(s)

Macro-eNBs and Pico-eNBs can schedule also users that are close to non-allowed CSG

HeNB(s), but not pico-UEs with larger RE.

Pico-UEs with larger RE,

close to CSG HeNB(s) are schedulable (as well as pico-UEs

without RE).



Baseline Assumptions for Network Configuration of Muting Patterns: HeNB

• Macro + HeNB scenario:

– Muting patterns are assumed to be statically configured from OAM

– Both macro and HeNB needs to know the muting pattern:

HeNB will apply the muting pattern (i.e. will mute some of its subframes)

Macro-eNB needs to know so it only schedule its users close to non-allowed CSG HeNBs during muted subframes + can configured Rel-10 UEs with appropriate measurement restrictions.

Centralized concept



Baseline Assumptions for Network Configuration of Muting Patterns: pico

• Macro + pico scenario:

– Muting patterns are assumed to be dynamically configured, assisted by new X2 signalling introduced in Rel-10.

– Both macro and pico needs to know the muting pattern:

Macro-eNB will apply the muting pattern (i.e. will mute some of its subframes)

Pico-eNB needs to know so it only schedule its users with large range extension during muted subframes + can configured Rel-10 UE measurement restrictions for those UEs.

Distributed concept



New X2 eICIC Related Signalling

• ABS information in IE

– This IE provides information about which subframes the sending eNB is configuring as ABS and which subset of ABS are recommended for configuring measurements towards the UE.

– Macro can signal ABS muting pattern to the pico nodes in ABS information IE.

– A neighbouring macro-cell receiving this information may aim at using similar muting pattern (but it is optional if macro-eNB follows such recommendation).

• Invoke information IE

– This IE provides an indication that the sending eNB would like to receive ABS information.

– Can be used by pico nodes to suggest macro-eNB to start scheduling ABS, i.e. that the pico serves UEs suffering high interference.

• Both the ABS information IE and/or Invoke IE is part of the LOAD INFORMATION message. Therefore, both of them can be exchanged between any two eNBs connected with X2, also between macros.

X2-AP: LOAD INFORMATION

eNB eNB



TS36.423 X2AP: Load Information

9.1.2.1 LOAD INFORMATION This message is sent by an eNB to neighbouring eNBs to transfer load and interference co-ordination

information.

Direction: eNB1 eNB2.

IE/Group Name Presence Range IE type and

reference

Semantics

description

Criticality Assigned

Criticality

Message Type M YES ignore

Cell Information M YES ignore

>Cell Information Item 1 .. <maxCelline

NB>

EACH ignore

>>Cell ID M ECGI Id of the

source cell

– –

>>UL Interference

Overload Indication

O – –

>>UL High Interference

Information

0 .. <maxCelline

NB>

– –

>>>Target Cell ID M ECGI Id of the cell

for which the

HII is meant

– –

>>>UL High Interference

Indication

M – –

>>Relative Power (RNTP) O – –

>>ABS Information O 9.2.54 YES ignore

>>Invoke Indication O 9.2.55 YES ignore



TS36.423 Invoke IE & ABS Information IE


reference

Semantics description

CHOICE ABS Information M – –

>FDD – –

>>ABS Pattern Info M BIT STRING

(SIZE(40))

Each position in the bitmap represents a DL

subframe, for which value "1" indicates ‘ABS’

and value "0" indicates ’non ABS’.

The first position of the ABS pattern

corresponds to subframe 0 in a radio frame

where SFN = 0. The ABS pattern is

continuously repeated in all radio frames.

The maximum number of subframes is 40.

>>Number Of Cell-specific

Antenna Ports

M ENUMERATED

(1, 2, 4, …)

P (number of antenna ports for cell-specific

reference signals) defined in TS 36.211 [10]

>>Measurement Subset M BIT STRING

(SIZE(40))

Indicates a subset of the ABS Pattern Info

above, and is used to configure specific

measurements towards the UE.


reference

Semantics description

Invoke Indication M ENUMERATED (A

BS Information, …)

–



New X2 eICIC Related Signalling (cont’)

• Macro-eNB can send a resource request

to the pico-eNB.

• Pico-eNB response with ”ABS status”

• The ”ABS status” is basically a load measure of how much the pico-eNB uses the subframes where the

macro-eNB is muted.

• It is intended that only ABS allocated to UEs that would not cope otherwise are reported

• This information can be used by the macro-eNB to get an idea of the consequences of

increasing/decreasing the number of muted subframes. It can be combined with information about

overall load in the pico.

9.2.58 ABS Status The ABS Status IE is used to aid the eNB designating ABS to evaluate the need for modification of the ABS pattern.

eNB1 eNB2

RESOURCE STATUS REQUEST

RESOURCE STATUS RESPONSE

DL ABS status M INTEGER (0..100) Percentage of resource blocks of ABS allocated for UEs

protected by ABS from inter-cell interference. This

includes resource blocks of ABS unusable due to other

reasons. The denominator of the percentage calculation is

indicated in the Usable ABS Information.

>> Usable ABS Pattern Info M BIT STRING (SIZE(40)) Each position in the bitmap represents a subframe, for which

value "1" indicates ‘ABS that has been designated as

protected from inter-cell interference’ and value "0" indicates

‘ABS that is not usable as protected ABS from inter-cell

interference’.

The pattern represented by the bitmap is a subset of, or the

same as, the corresponding ABS Pattern Info IE conveyed in

the LOAD INDICATION message.



ABS patterns

• Pattern 1: RRM/RLM measurement resources restriction for the serving cell

• Serving cell RLM results look more stable. As a result,

– For PUE (UE under Pico), RLF declaration avoided at CRE of pico cell

– For MUE (UE under Macro), RLF declaration avoided at femto cell area



ABS patterns – cont’d

• Pattern 2: RRM measurement resources restriction for neighboring cells

• Neighboring cell looks more optimistic

– MUE can be handed over to in CRE area of pico cell

• One pattern with PCI list



ABS patterns – cont’d

• Pattern 3: Resources restriction for CSI measurement of the serving cell

• Two subsets for pattern 3: for eNB to obtain multiple channel status measurement for scheduling, e.g.,

– CSI measurement on ABS

– CSI measurement on non-ABS



UE Operation for eICIC: Example



Performance enhancement example through Pico Cells and eICIC

UE1

UE2 UE3

Macro

Pico Pico

0

10

20

30

40

50

60

70

UE1 UE2 UE3 Total

Mbps

No eICIC

eICIC with 50% ABS

System Capacity with HetNet and eICIC +50%



CA approach to interference avoidance in HetNet



With or without cross-carrier scheduling



FeICIC in Rel-11

• eICIC is introduced in LTE Rel-10 and further enhanced in Rel-11

– eICIC = enhanced Inter Cell Interference Coordination

– FeICIC = Further enhanced Inter Cell Interference Coordination

• eICIC consists of three design principles

– Time domain interference management (Rel-10)

Severe interference limits the association of terminals to low power cells

– Cell range expansion (Rel-10/11)

Time domain resource partitioning enables load balancing between high and low power cells

Resource partitioning needs to adapt to traffic load

– Interference cancellation receiver in the terminal (Rel-11/12)

Ensures that weak cells can be detected

Inter cell interference cancellation for control signals (pilots, synchronization signals)

Ensures that remaining interference is removed

Inter cell interference cancellation for control and data channels (PDCCH/PDSCH)

* source: Qualcomm



eICIC and FeICIC

• FeICIC (Further enhanced non CA-based ICIC for LTE)

– WI was completed in Dec. 2012

– Support of larger CRE(up to 9dB) for better load balancing

Macro eNB provides Pico’s SIB1 to the UE in larger CRE region via dedicated signaling

* source: ETRI

eICIC in Rel-10 FeICIC in Rel-11



FeICIC Performance

* source: Qualcomm



FeICIC Performance – cont’d

* source: Qualcomm



Why Small Cell?


Relay




Relay

• Relay as a tool to improve, e.g.

– the coverage of high data rates

– group mobility

– temporary network deployment

– the cell-edge throughput

– provide coverage in new areas

• Various relay types

– Type1 vs. Type2

– In-band vs. out-band

– Stationary vs. mobile

– Single hop vs. multi-hop

– Etc…



Proxy Functionality

• DeNB plays S1/X2-AP and S-GW proxy role for RN

• DeNB appears to RN as

– Control plane: MME for S1, eNB for X2

– User Plane: S-GW



In-band Relay

• Interference b/w access link and backhaul link

• Inband relay - Un and Uu links are isolated in time



In-band Relay – cont’d

• Using MBSFN subframe for relay operation

Multiplexing b/w access and backhaul links

• RN subframe configuration



RN Startup Procedure - Phase I

• Attach for RN Pre-configuration



RN Startup Procedure - Phase II

• Attach for RN Operation



Rel-10 Relay Node Simplification

• Deployment Scenario Simplification

– No RN mobility

– No multi-hop RN

– No inter-RN handover

• Radio Protocol Simplification

– No additional header compression

– No data forwarding at handover

– No semi-persistent scheduling

– No TTI bundling

– No MBMS on Relay



FS_LTE_mobRelay Study on Mobile Relay for E-UTRA

• Rapporteur: CATT

• Schedule: Start (July 2007) – Finish (Dec 2013, estimated)

• Latest SID: RP-131375 (RAN#61)

– The objective shall focus on the backhaul design of mobile relays

Identify the target deployment scenarios first (RAN3)

Identify the key properties of mobile relays and assess the benefits of mobile relays over existing solutions (e.g. L1 repeaters) in fast-moving environments

• Evaluate suitable mobile relay system architecture and procedures, including procedures for group mobility (RAN3)

• Comparison based on higher layer considerations, e.g.

• Group mobility, etc. (RAN3)

• Comparison based on PHY layer considerations (RAN1)

• Analyze the potential impact of moving cells created by mobile relays

• Latest Status Report: RP-131380

• Latest 3GPP TR and/or TS: 36.836



A reference scenario for high speed train



Alternative 1

Alt.1 relay architecture

• The same RN as Rel-10 with minor difference that MRN supports NNSF.



Alternative 2

PGW/SGW (RN)

Relay GW

E-UTRA UE

Un

eNB

UE

Uu

MME/SGW (UE)

E-UTRA UE

Un

eNB

eNB

UE

Uu

eNB

PGW/SGW (RN)

Relay GW

Initial DeNB Target DeNB

S1-U

Alt.2 with Relay GW and PGW/SGW collocated with initial DeNB

Alt.2 with Relay GW and PGW collocated with initial DeNB



Alternative 2 – cont’d

Alt.2 with dual Rel-10relays for HO Alt.2 with Relay GW and PGW/SGW separated from initial DeNB



Alternative 4

User-UE

SGW/PGW

S11

(UE)

User-UE

MME

Donor-eNB

(Proxy)

User-UE

E-UTRA-Uu(UE)

UE Network Elements

IPRelay

UE related

S1 msg

User-Plane

data(UE)

S1-U

(UE)

Un

interface

S1-M

ME

(UE

)

Relay Network ElementsRelay-UE’s

MME

Relay-UE’s

SGW/PGW

S1

-MM

E

(Re

lay)

S1-U

(Relay)

S11

(Relay)IP

• New model

• New functionalities needed for one-to-one mapping between two DRBs (one over Un and one over Uu) that need to be kept synchronized.



Why Small Cell?


Relay




FS_LTE_SC_enh_req Study on Scenarios and Requirements of LTE Small Cell Enhancements for E-UTRA and E-UTRAN

• Rapporteur: China Mobile

• Schedule: Start (Sep 2012) – Finish (Dec 2012)


– Identify the target deployment scenarios and the relevant characteristics:

Definition and characterization of small cells;

Targeted deployment scenarios e.g. used spectrum, backhaul and synchronization.

– Identify the key requirements for small cell enhancements:

Deployment related requirements;

Capability related requirements e.g. peak data rate;

System performance requirements e.g. spectrum efficiency, coverage and mobility (in idle and connected states);

Operational requirements, e.g. architecture, complexity, cost, energy efficiency etc.





Small cell deployment scenario

• With and without macro coverage

• Outdoor and indoor (UE mobility)

• Ideal and non-ideal backhaul

• Sparse and dense

• Synchronized and un-synchronized



More specified small cell deployment scenario



Spectrum

• Applicable to all existing and as well as future cellular bands, with special focus

on higher frequency bands, e.g., the 3.5 GHz band

• Also take into account the possibility for frequency bands that, at least locally, are

only used for small cell deployments.

• Co-channel deployment scenarios between macro layer and small cell layer

should be considered as well.



FS_LTE_SC_enh_L1 Study on Small Cell Enhancements for E-UTRA and E-UTRAN – Physical-layer aspects

• Rapporteur: Huawei

• Schedule: Start (Dec 2012) – Finish (Dec 2013, estimated)


– Objective

Define channel characteristics of small cell deployments and UE mobility scenarios.

Study potential enhancements to improve the spectrum efficiency, including

• Introduction of a higher order modulation scheme (e.g. 256 QAM) for the downlink.

• Enhancements and overhead reduction for UE-specific reference signals and control signaling in downlink and uplink based on existing channels and signals

Study efficient operation of a small cell layer composed of small cell clusters.

• Mechanisms for interference avoidance and coordination among small cells adapting to varying traffic and the need for enhanced interference measurements.

• Mechanisms for efficient discovery of small cells and their configuration.

Physical layer study and evaluation for small cell enhancement higher-layer aspects, in particular concerning the benefits of mobility enhancements and dual connectivity to macro and small cell layers and for which scenarios such enhancements are feasible and beneficial.



FS_LTE_SC_enh_L1 – cont’d Study on Small Cell Enhancements for E-UTRA and E-UTRAN – Physical-layer aspects

– The study should address small cell deployments taking into account existing mechanisms (e.g., CoMP, FeICIC) wherever applicable.

– Coordinated and time synchronized operation of the small cell layer and between small cells and the macro layer can be assumed.

– Backward compatibility, i.e. the possibility for legacy (pre-R12) UEs to access a small-cell node/carrier, shall be guaranteed





Link level evaluation results of 256QAM

SINR range in which a gain is

observed

Observed maximum spectrum efficiency gain

0% Tx EVM 4% Tx EVM 6% Tx EVM

Source 1 >27dB (rank adaptation, 0% or

4% Tx EVM) 33%

30%(0% Rx EVM)

15%(2% Rx EVM)

Source 2 >25dB (rank2, 0% or 4% Tx

EVM) 33% 15% 2%

Source 3 >30dB(rank2)

>20dB(rank1)

33% (rank2)

33% (rank1)

17%(rank2)

25%(rank1)

Source 4 >30dB(rank2, TM3)

>36dB(rank2, TM3, 4% Tx EVM) 30%(TM3, @38dB) * 3%(TM3, @38dB) * -30% (TM3)

Source 5 >25 dB(rank adaptation, 0% or

4% Tx EVM) 25%(@40dB)*

10%(@40dB)*

8% (2% Rx EVM,

@40dB) *

3%(4% Rx EVM)

1%

Source 6

>25 dB(rank2, 0% or 4% Tx EVM)

>18 dB(rank1, 0%, 4% or 6% Tx

EVM)

15%*(rank2, @30dB) *

33% (rank1)

10% (rank2, @30dB) *

29%(rank1)

-4%(rank2)

25%(rank1)

Source 7

(fixed coding

rate of 5/6)

>30dB(0% Tx EVM, rank 2)

>38dB(4% Tx EVM, rank2)

25% (rank 2)

-13% (rank2, RX IQ

imbalance with -25dB

IMRR)

10% (rank2)

-9% (rank2, RX IQ


IMRR)

-30% (rank2)

-3% (rank2, RX IQ


IMRR)

Source 8

>27dB(rank adaptation, 0% Tx

EVM)

>30dB(rank adaptation, 4% Tx

EVM)

23.1%(@40dB)* 9.4%(@40dB)*

0%(4% Rx EVM)

Source 9 >28dB (rank2)

>24dB (rank1)

20%(rank2, @32dB) *

30% (rank1, @32dB) * 15%(@32dB)* 0%

Source 10 >22dB dB (rank1) 28% (rank1, @32dB) * 15% (rank1)



UE-specific RS overhead reduction

• Overhead reduction of downlink UE-specific reference signal

• Overhead reduction of uplink UE-specific reference signal

SINR Average gain

5dB 0.9%

20dB 2.4%

30dB 3.9%

Table 6.2.1-2 Observed spectrum efficiency gain

SINR Average gain

3dB 7.8%

10dB 8.7%

20dB 6.4%

Table 6.2.2-2 Observed spectrum efficiency gain



Interference Avoidance and Coordination

• Small cell on/off

– Baseline schemes without any on/off

– Long-term on/off schemes for energy saving

– Semi-static on/off schemes

– Ideal, dynamic on/off schemes

– NCT with NCTCRS (i.e., reduced CRS)

• Enhanced power control/adaptation

• Enhancement of frequency domain power control and/or ABS to multi-cell scenarios

• Load balancing/shifting

Please refer to 3GPP TR 36.872



Efficient discovery of small cells & configurations

• Enhancements of small cell discovery

– PSS/SSS interference cancellation

– Burst transmission of DL-SS/RS

If small cell on/off mechanisms are supported, a small cell in dormant state or DTX state transmits a DL-SS/RS

burst with low duty cycle.

– Network synchronization and assistance

– New discovery mechanism

– Transmission of DL-SS/RS at specific carrier

– Etc…

• Necessity of PCI extension??

– It is observed from the evaluation results that in terms of PCI collision, assuming a completely

random PCI allocation, the probability of PCI collision is less than 2%.

– For PCI confusion, the existing mechanism of reading the Cell Global Identifier from SIB1 utilizing

autonomous gaps is deemed sufficient. However, it was also observed that SI reading may become

more frequent in dense small cell scenarios.

– As a conclusion, the existing cell discovery signals are sufficient in terms of number of individually

identifiable cells



Radio-interface based synchronization

• Network listening

• UE-assisted synchronization

– The synchronization between the source cell and the target cell can be achieved by some information

provided by or obtained from UEs.

– It is observed that the availability and selection of the UEs to assist synchronization may impact the

performance of the synchronization.

We cannot rely on UE based synch if you want to serve pre-release 12 UEs.

So, UE assisted synchronization will not be studied further, as suggested by NSN in RAN#61.

• Both solutions have the following potential standards impacts:

– The indication of the synchronization stratum level

– The maximum supported hop number

– Applicability/compatibility of synchronization approaches with other ongoing studies



FS_LTE_SC_enh_hilayer Study on Small Cell Enhancements for E-UTRA and E-UTRAN – Higher-layer aspects

• Rapporteur: NTT DOCOMO



– Identify and evaluate the benefits of UEs having dual connectivity to macro and small cell layers served by different or same carrier.

– Identify and evaluate potential architecture and protocol enhancements particular for the feasible scenario of dual connectivity and minimize core network impacts if feasible, including:

Overall structure of control and user plane and their relation to each other, e.g., supporting C-plane and U-plane in different nodes, termination of different protocol layers, etc.

– Identify and evaluate the necessity of overall RRM structure and mobility enhancements for small cell deployments:





Increased signalling load due to frequent handover

• Increase in number of handovers where 10 small cells are deployed per macro

cell in deployment scenario #1



Scenario #2: Method A

• Method A

For UEs served by a single cell only, i.e., either by a macro or a small cell

• Statistics for number of mobility events per UE per hour for Method A

0

500

1000

1500

2000

3 kmph 2 Picos

30 kmph 2 Picos

60 kmph 2 Picos

3 kmph 10 Picos

30 kmph 10 Picos

60 kmph 10 Picos

Events per UE per hour

PP HO

PM HO

MP HO

MM HO



Scenario #2: Method B

• Method B

For UEs configured to deliver data via macro and small cells simultaneously

• Statistics for number of mobility events per UE per hour for Method B

0

500

1000

1500

2000

3 kmph 2 Picos

30 kmph 2 Picos

60 kmph 2 Picos

3 kmph 10 Picos

30 kmph 10 Picos

60 kmph 10 Picos

Events per UE per hour

SCell Change

SCell Removal

SCell Add

PCell HO



Dual Connectivity

• Benefits of Dual Connectivity

– hides small cell mobility to CN

– throughput enhancements with inter-site CA

maximum BW allocated to the UE can consist of the BW offered by the macro + the BW offered by the small cell

– traffic offload to small cell

macro can be relieved from the lower layer processing of all user plane data

– One target scenario

U-Plane aggregated from macro & pico, mobility management/RRC from macro

• Expected Changes & Impacts

– dual connectivity will require changes to user plane protocols

– how to serve non-CA capable UEs in enhanced small cells

Macro #1

Pico #1

Pico #2

Pico #3

Macro #2

SCell Addition

SCell Removal

SCell Change

SCell Addition

SCell Removal

PCell Handover



U-plane Bearer Split Options

• Option 1: S1-U also terminates in SeNB;

• Option 2: S1-U terminates in MeNB, no bearer split in RAN;

• Option 3: S1-U terminates in MeNB, bearer split in RAN.

Option 3Option 1

MeNB

SeNB

EPS bearer #1

EPS bearer #2

UE

S-GW

Option 2

MeNB

SeNB

EPS bearer #1

EPS bearer #2

UE

S-GW

MeNB

EPS bearer #1

SeNB

EPS bearer #2

UE

S-GW



Control Plane architecture

• It is assumed that there will be only one S1-MME Connection per UE

• Alt. 1: Centralised RRM, with one RRC connection/signalling b/w UE and macro cell eNB

• Alt. 2: Distributed RRM, with one RRC connection/signalling b/w UE and macro cell eNB

• Alt. 3: Distributed RRM, with two RRC connection/signalling b/w UE – macro cell eNB, and

UE – small cell eNB

* source: NTT docomo

Selected



Overall technical issues considered in small cell

* source: ETRI



FS_UTRA_LTE_WLAN_interw Study on WLAN/3GPP Radio Int

• Rapporteur: Intel



– Justification

WLAN interworking and integration is currently supported at the CN level, including both seamless and non-seamless mobility to WLAN.

However, as operator controlled WLAN deployments become more common and WLAN usage increases, RAN level enhancements for WLAN interworking which may improve user experience, provide more operator control and better access network utilization and reduced OPEX may be needed.

– The following issues should be taken into account during the study:

Operator deployed WLAN networks are often under-utilized

User experience is suboptimal when UE connects to an overloaded WLAN network

Unnecessary WLAN scanning may drain UE battery resources



FS_UTRA_LTE_WLAN_interw – cont’d Study on WLAN/3GPP Radio Int

– Objective

In a first phase:

• Identify the requirements for RAN level interworking, and clarify the scenarios to be considered in the study while taking into account existing standardized mechanisms.

In a second phase:

• Identify solutions addressing the requirements identified in the first phase which cannot be solved using existing standardized mechanisms, including:

• Solutions that enable enhanced operator control for WLAN interworking, and enable WLAN to be included in the operator’s cellular Radio Resource Management.

• Enhancements to access network mobility and selection which take into account information such as radio link quality per UE, backhaul quality, load, etc for both cellular and WLAN accesses

• Evaluate the benefits and impacts of identified mechanisms over existing functionality, including core network based WLAN interworking mechanisms (e.g. ANDSF).





WLAN Interworking

• Assumptions

– Solutions developed as a result of this study should not rely on standardized interface between 3GPP and WLAN RAN nodes.

– UE in coverage of a 3GPP RAT when accessing WLAN will still be registered to the 3GPP network and will be either in IDLE mode or in CONNECTED mode.

– User preference always take precedence over RAN based or ANDSF based rules.

• Requirements

– Improve bi-directional load balancing between WLAN and 3GPP

– Improve the utilization of WLAN when it is available and not congested.

– Reduce or maintain battery consumption (e.g. due to WLAN scanning/discovery).

– Compatible with all existing CN WLAN related functionality

– Backward compatible with existing 3GPP and WLAN specifications

– Avoid changes to IEEE and WFA specifications.

– Per target WLAN system distinction (e.g. based on SSID) should be possible.

– Per-UE control for traffic steering should be possible.

– Avoid ping-ponging between UTRAN/E-UTRAN and WLAN.



WLAN Interworking: Solution 1

• RAN provides RAN assistance information to the UE through broadcast signaling (and optionally dedicated signaling)

• UE uses the RAN assistance information UE measurements and information provided by WLAN and policies that are obtained via the ANDSF or via existing OMA-DM mechanisms or pre-configured at the UE to steer traffic to WLAN or to RAN

eNB/RNC WLAN APUE

SystemInformation




• RAN provides assistance information to the UE through dedicated and/or broadcast signaling

• UE steers traffic to a WLAN or RAN, based on this information, UE measurements and information provided by WLAN and rules specified in the RAN specification

eNB/RNC WLAN APUE

1. Parameters

2. Steer traffic

to/from WLAN

according to RAN

rule and ANDSF




• The traffic steering for UEs in RRC CONNECTED state is controlled by the network using dedicated traffic steering commands, potentially based also on WLAN measurements (reported by the UE)

• For UEs in IDLE mode, the solution can be similar to solution 1 or 2

• Alternatively, UEs in those RRC states can be configured to connect to RAN and wait for dedicated traffic steering commands

eNB/RNC WLAN AP

2. Measurement report

3. Steering command

4. UE Ack/Response

UE

1. Measurement control

Event

trigger

Steer traffic to/from

WLAN

RRC connection

request



Small Cell Summary

LTE Rel-8 and Rel-9

LTE Advanced

Rel-10 and Rel-11

LTE Advanced Evolution

Rel-12 and Rel-13

5G

2010+

2013+

2015+

2020+

Optimize data performance and

architecture

Squeeze macro cells

Small cells &

new service enablers

Small Cell Enhancements

Macro Cell Enhancements

Machine-Type Communication, Device-to-Device

SON, WLAN Integration, Public

Safety

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Documents