LTE SC-FDMA for upllink

8/7/2019 LTE SC-FDMA for upllink

http://slidepdf.com/reader/full/lte-sc-fdma-for-upllink 1/17

SC-FDMA for 3GPP LTE uplink

Hong-Jik Kim, Ph. D.



Wireless Broadband – The New Category

le UMTS /

Mob

HSDPA

802.20

WCDMACellular

Wireless Broadband

rea

1xEV-DO

WiMAX 802.16e

Lo

cal

802.11

Cordless.

n

d

a g

WiMAX 802.16dNG –

Fix

/ DLCPOTS

Fiber

Voice & Messaging Broadband

Hong-Jik Kim 2



3GPP Standard

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

apan

WCDMA HSDPA LTEHSUPA Rel. 7

North

R99 Rel. 5 Rel. 6 Rel. 6

DLShared CH

ULShared CH

Multi-CarrierDL MIMO

OFDMA

America

HARQAMC

HARQAMC

Hong-Jik Kim 3



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

• 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

• -p ane : < ms rom o server

> Capacity

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

> Mobility

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

Hong-Jik Kim 4



OFDMA

Nu Nc Nc Np+Nc

S/Pconverter

Constellationmapping

Symbolto

SubcarrierNc-point

IFFT Cyclic P/S

BitStream

MappingPrefix converter

> Hi h PAPR• Need for PAPR reduction scheme especially for UL

among Nc subcarriers

> Receiver is based on FFT

Hong-Jik Kim 5



OFDM / MIMO

> OFDM – robust in dense environments

> OFDM / MIMO perfect long term marriage,

& coverage

QAMSymbol

r

1A

1A’

na

-

Symbol Multi-ElementReceiver

-

r

1’

-

Multi-ElementTransmitter

-

E

ncod

.

.

.

.

.

.

.

B

C

MIMOChannel Matrix, H

t0 t1 t2De

code

.

.

B’

C’

.

.

.

..TxAnten

E

ncod

.

.

.

.

.

.

.

.

.



t0 1 t2De

code

.

.

.

.

’

’

.

.

.

..

‘Space-TimeCodeword’

T.

NT Rx .

NR‘Space-TimeCodeword’

T..

T Rx ..

R

2.5GHz, 10MHz,TDDMIMO (Tx:Rx) 1x1 1x2 2x2 2x4 4x2 4x4

OFDMA

Cornerstone Technology for WiMAX, 3GPP LTE, 3GPP2 Evol and 802.20

. . . . . .

Hong-Jik Kim 6

rac ca ep oymen s w on gura ons – a e n enna o u ons



UL: Single Carrier (SC)-FDMA

> DFT-spreading of data symbols in frequency domain

> Low PAPR

> Subcarrier mapping

• Distributed mapping

• Transmit signal similar to IFDMA• Localized mapping

• -

• transmit signal similar to narrowband single-carrier

> MMSE equalization to restore code orthogonality

Hong-Jik Kim 7



UL: Interleaved FDMA (IFDMA)

kt T

j

e

π 2

can be used by different users

-

comb-shaped spectrum

> Hybrid of single-carrier and OFDM concepts

•

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

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

Hong-Jik Kim 8



Localized vs. Distributed

5/4 = 1.25 MHz Localized

Larger frequency diversityLess frequency diversity

5 MHz Distributed, RF = 4

ow-ra e an g -ra e users coex speacefully

Time domain channel has larger powerfluctuations

Difficult to choose a ro riate MCS due to

fluctuation

More stable MCS selection

rapid channel fluctuations

Less accurate power control

- -ore accurate power contro

Channel estimation becomes degraded

for ver lar e re etition factors

(broadband) user from the channel,especially if channel dependentschedulin is used

Tighter frequency synchronization maybe required

Narrowband filter has longer impulseresponse reduces “effective” CP

Channel estimation not degraded at

low bandwidths

Hong-Jik K im 9



Frame structure

1 sub-frame = 0.5 msec

CP LB#1 CPCP#1

LB#6CP LB #2 CP LB #3 CP LB #4 CP LB #5 CP #2

> su - rame = . ms• 6 LB (Long Block) for user / control data transfer

• or oc or p o con ro a a rans er

Hong-Jik Kim 10



Cluster structure, Localized FDMA

10 data sub-carriers + 5 pilot sub-carriers

s or oc

1 TTI

Data sub-carrier

Pilot sub-carrier

-

Hong-Jik Kim 11

,



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

-

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

Hong-Jik Kim 12

,



Simulation Parameters

Frequency hopping used on a TTI basis

MCS: QPSK rate ¼, ½, ¾ & 16 QAM rate ½, ¾

1 transmit, 2 receive antennas (uncorrelated)

ITU PB channel@3 km/hr

One turbo block per TTI

TTI=0.5ms

Both ideal and estimated channel runnin side b side

Pilot overhead: 1/7

*. .

Pilot power boost = 3dB (i.e. pilot signal amplitude = sqrt(2)*data

,

frequency domain.

Hong-Jik Kim 13



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

100 Loc.FDMA, v=3km/h

10-1

ER

-2

BL

QPSK 1/4, Perfect IR

QPSK 1/4

QPSK 1/2, Perfect IRQPSK 1/2


16QAM 1/2, Perfect IR

16QAM 1/2


16QAM 3/4

Hong-Jik Kim 14

-10 -5 0 5 10 15 2010

-3

SNR

R l f IFDMA 3k /h



Results for IFDMA , v=3km/h

0iFDMA, v=3km/h

10

-10

BLE

10-2


QPSK 1/4QPSK 1/2, Perfect IR

QPSK 1/2

,

QPSK 3/4


16QAM 1/2


Hong-Jik Kim 15

-15 -10 -5 0 5 10 15 2010

-3

SNR

iFDMA/L FDMA i h l h l i i 3k /h



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

0SUBBAND/DIVERSITY, Estimated channel, v=3km/h

10

-10

BLE

10

-2

Loc.FDMA QPSK 1/4

iFDMA QPSK 1/2

Loc.FDMA QPSK 1/2

iFDMA QPSK 3/4

Loc.FDMA QPSK 3/4

iFDMA 16QAM 1/2

Loc.FDMA 16QAM 1/2

iFDMA 16QAM 3/4

Loc.FDMA 16QAM 3/4

Hong-Jik Kim 16

-15 -10 -5 0 5 10 15 2010

-3

SNR



an you

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LTE SC-FDMA for upllink