SC-FDMA for 3GPP LTE uplink

Hong-Jik Kim, Ph. D.

Wireless Broadband – The New Category

ile 3GPP LTEUMTS / M

obil

HSDPA

3GPP LTE

802.20

WCDMACellular Wireless Broadband

Are

a

1xEV-DO WiMAX 802.16e

WiFi 802 11

Loca

l A

802.11 a/b/g

WiFiCordless 802.11 n

ed

a/b/gWiMAX 802.16d

NG –DSLDSL / Cable /

Fixe DSL

/ DLCPOTSDSL / Cable /

Fiber

Existing 2004-2006 Rollout 2006+

Voice & Messaging Broadband

Hong-Jik Kim2

Existing 2004-2006 Rollout 2006+

3GPP Standard

J PDC

2G2G 2,5G2,5G 3G3G 3,5G3,5G 4G ?4G ?

Japan

Europe

PDC

GSM GPRS WCDMA HSDPA LTEHSUPA Rel. 7Europe

North

GSM

TDMA

GPRS R99 Rel. 5

EDGE

LTERel. 6 Rel. 6

DL Shared CH

UL Shared CH

Multi-CarrierDL MIMO

OFDMADL/UL MIMOAmerica TDMA EDGE S a ed C

HARQAMC

S a ed CHARQAMC

O DL/UL MIMO

Hong-Jik Kim3

3GPP LTE objectives> Scalable bandwidth : 1.25, 2.5, 5, 10, (15), 20MHz

> Peak data rate (scaling linearly with the spectrum allocation)• DL (2 Rx @ UE) : 100Mb/s for 20MHz spectrum allocation• UL (1 Tx @ UE) : 50Mb/s for 20MHz spectrum allocation

> Spectrum efficiency> Spectrum efficiency• DL : 3-4 times HSDPA for MIMO (2,2)• UL : 2-3 times HSUPA for MIMO(1,2)

> Reference Antenna configurations (targets)• DL : 2Tx and 2 Rx• UL : 1 Tx and 2 Rx

> Latency• C-plane : < 50-100ms to establish U-plane

U plane < 10ms from UE to ser er• U-plane : < 10ms from UE to server

> Capacity• 200 users for 5MHz, 400 users in larger spectrum allocations (active state) g p ( )

> Mobility• LTE is optimised for low speeds 0-15km/h but mobility is maintained for speeds up to 350km/h

Hong-Jik Kim4

OFDMANu Nc Nc Np+Nc

S/P converter

Constellation mapping Symbol

toSubcarrier

Nc-pointIFFT Cyclic P/S

Bit Stream

Mapping Prefix converter

> High PAPRg• Need for PAPR reduction scheme especially for UL

> Various mappings from Nu data symbols to Nu subcarriers> Various mappings from Nu data symbols to Nu subcarriers among Nc subcarriers

> Receiver is based on FFT

Hong-Jik Kim5

OFDM / MIMO> OFDM – robust in dense environments> OFDM / MIMO perfect long term marriage> Achieves considerable increase in capacity peak rates> Achieves considerable increase in capacity, peak rates

& coverage

Space TimeQAMSymboler

1A

r

1 A’na

Space-TimeSymbol Multi-Element

Receiver-

er1

r

’

-Multi-Element Transmitter

-x

Enco

de

.

.

.

.

.

.

.

BC

MIMOChannel Matrix, H

t0 t1 t2 Dec

oder

.

.

B’C’

.

.

.

.

.

TxA

nten

x En

cod e

.

.

.

.

.

.

.

.

.

MIMOChannel Matrix, H

MIMOChannel Matrix, H

t0 1 t2 Dec

oder

.

.

.

.

’’

.

.

.

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.

‘Space-Time Codeword’

Tx. .

NT Rx .

NR‘Space-Time Codeword’

Tx.. .

T Rx ..

R

2.5GHz, 10MHz,TDDMIMO (Tx:Rx) 1x1 1x2 2x2 2x4 4x2 4x4Bits/Sec/Hz/Sector 1 2 1 8 2 8 4 4 3 7 5 1

OFDMA

Cornerstone Technology for WiMAX, 3GPP LTE, 3GPP2 Evol and 802.20P ti l D l t ith 2X4 C fi ti C bl & A t S l ti

Bits/Sec/Hz/Sector 1.2 1.8 2.8 4.4 3.7 5.1

Hong-Jik Kim6

Practical Deployments with 2X4 Configurations – Cable & Antenna Solutions

UL: Single Carrier (SC)-FDMA

> DFT-spreading of data symbols in frequency domain

> Low PAPR> Subcarrier mapping

• Distributed mapping• Frequency diversity• Frequency diversity• Transmit signal similar to IFDMA

• Localized mapping• Multi user diversity (frequency domain scheduling)• Multi-user diversity (frequency domain scheduling)• transmit signal similar to narrowband single-carrier

> MMSE equalization to restore code orthogonality

Hong-Jik Kim7

UL: Interleaved FDMA (IFDMA)kt

Tj

eπ2

can be used by different users

> Also known as distributed SC-FDMA

comb-shaped spectrum

> Also known as distributed SC FDMA

> Hybrid of single-carrier and OFDM concepts• Low PAPR (same as single carrier)Low PAPR (same as single carrier)

> Orthogonal uplink as each user is assigned set of sub-carriers orthogonal to other users

> Receiver is based on FDE (e.g. MMSE).

Hong-Jik Kim8

Localized vs. Distributed

5/4 = 1.25 MHz LocalizedLarger frequency diversity

L t d hi h t i t

Less frequency diversityHigher FER for narrowband users

5 MHz Distributed, RF = 4

Low-rate and high-rate users coexist peacefully

Time domain channel has less power

Higher FER for narrowband usersTime domain channel has larger power fluctuations

Difficult to choose appropriate MCS due to Time domain channel has less power fluctuation

More stable MCS selectionM t t l

Difficult to choose appropriate MCS due to rapid channel fluctuationsLess accurate power control

Low-rate user may block a high-rate More accurate power control

Channel estimation becomes degraded for very large repetition factors

Low rate user may block a high rate (broadband) user from the channel, especially if channel dependent scheduling is used for very large repetition factors

Tighter frequency synchronization may be required

g

Narrowband filter has longer impulse response reduces “effective” CP length (IFDMA only)length (IFDMA only)

Channel estimation not degraded at low bandwidths

Hong-Jik Kim9

Frame structure

SB

1 sub-frame = 0.5 msec

SB

1 b f 0 5

CP LB#1 CPCP SB#1 LB#6CP LB #2 CP LB #3 CP LB #4 CP LB #5 CP SB

#2

> 1 sub-frame = 0.5ms• 6 LB (Long Block) for user / control data transfer

2 SB (Sh t Bl k) f il t / t l d t t f• 2 SB (Short Block) for pilot / control data transfer

Hong-Jik Kim10

Cluster structure, Localized FDMA

10 data sub-carriers + 5 pilot sub-carriers

1 h t bl k

1 long block

1 short block

1 TTI1 long block

Data sub-carrier

Pilot sub-carrier

Unobserved sub-carrier short blocks

Hong-Jik Kim11

Unobserved sub-carrier, short blocks

Cluster structure, Interleaved FDMA

10 data sub-carriers + 5 pilot sub-carriers per user

1 TTI

Data sub-carrier of user 1, 2 ,3 ,4

Unobserved sub-carrier short blocks

Pilot sub-carrier of user 1, 2 ,3 ,4

Hong-Jik Kim12

Unobserved sub carrier, short blocks

Simulation Parameters

Frequency hopping used on a TTI basisMCS: QPSK rate ¼, ½, ¾ & 16 QAM rate ½, ¾ 1 transmit, 2 receive antennas (uncorrelated)ITU PB channel@3 km/hrOne turbo block per TTITTI=0.5msBoth ideal and estimated channel running side by sideBoth ideal and estimated channel running side by sidePilot overhead: 1/7Sampling Rate = 15 359 MHz (=4*3 84MHz)Sampling Rate = 15.359 MHz (=4 3.84MHz)Pilot power boost = 3dB (i.e. pilot signal amplitude = sqrt(2)*data signal amplitude) QPSK modulation with constant modulus in thesignal amplitude), QPSK modulation with constant modulus in the frequency domain.

Hong-Jik Kim13

Results for Loc.FDMA, v=3km/h

100

Loc.FDMA, v=3km/h

10-1

LER

10-2

BL

QPSK 1/4, Perfect IR10

QPSK 1/4QPSK 1/2, Perfect IRQPSK 1/2QPSK 3/4, Perfect IRQPSK 3/4QPSK 3/416QAM 1/2, Perfect IR16QAM 1/216QAM 3/4, Perfect IR16QAM 3/4

Hong-Jik Kim14

-10 -5 0 5 10 15 2010

-3

SNR

Results for IFDMA , v=3km/h

100

iFDMA, v=3km/h10

0

-110

-1

R

2

BLE

R

10-2

QPSK 1/4, Perfect IRQPSK 1/4QPSK 1/2, Perfect IRQPSK 1/2QPSK 3/4 Perfect IRQPSK 3/4, Perfect IRQPSK 3/416QAM 1/2, Perfect IR16QAM 1/216QAM 3/4, Perfect IR16QAM 3/4

Hong-Jik Kim15

-15 -10 -5 0 5 10 15 2010

-3

SNR

16QAM 3/4

iFDMA/Loc.FDMA with real channel estimation , v=3km/h

100

SUBBAND/DIVERSITY, Estimated channel, v=3km/h10

0

-110

-1

R

2

BLE

R

iFDMA QPSK 1/410-2 iFDMA QPSK 1/4

Loc.FDMA QPSK 1/4iFDMA QPSK 1/2Loc.FDMA QPSK 1/2iFDMA QPSK 3/4Loc.FDMA QPSK 3/4iFDMA 16QAM 1/2Loc.FDMA 16QAM 1/2iFDMA 16QAM 3/4Loc.FDMA 16QAM 3/4

Hong-Jik Kim16

-15 -10 -5 0 5 10 15 2010

-3

SNR

Th kThank you