1_LTE_TDD

© 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

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Documents

1_LTE_TDD