Single Carrier FDMA - KFUPMfaculty.kfupm.edu.sa/coe/ashraf/richfilesteaching/COE082_543/... · Single Carrier FDMA May18,2008 HyungG.Myung ... SC-FDMA Implementation in 3GPP LTE

Single Carrier FDMA

May 18, 2008

Hyung G. Myung ([email protected])

Single Carrier FDMA | Hyung G. Myung 1

OutlineOutlineOutlineOutline

Introduction and Background

SC-FDMA Implementation in 3GPP LTE

Peak Power Characteristics of SC-FDMA Signals

Summary and Conclusions

Uplink Resource Scheduling in SC-FDMA Systems

Overview of SC-FDMA


Overview of SC-FDMA






3GPP Evolution3GPP Evolution3GPP Evolution3GPP Evolution

UMTS/WCDMA

HSDPA

HSUPA

HSPA+

LTE

R99

R5

R6

R7


R8


Key Features of LTEKey Features of LTEKey Features of LTEKey Features of LTE

• Multiple access scheme

– DL: OFDMA with CP.

– UL: Single Carrier FDMA (SC-FDMA) with CP.

• Adaptive modulation and coding

– DL modulations: QPSK, 16QAM, and 64QAM

– UL modulations: QPSK and 16QAM

– Rel-6 Turbo code: Coding rate of 1/3, two 8-state constituent encoders, and a contention-free internal interleaver.

• Advanced MIMO spatial multiplexing techniques

– (2 or 4)x(2 or 4) downlink and uplink supported.

• Multi-layer transmission with up to four streams.

– Multi-user MIMO also supported.

• ARQ within RLC sublayer and Hybrid ARQ within MAC sublayer.



Broadband Multipath ChannelBroadband Multipath ChannelBroadband Multipath ChannelBroadband Multipath Channel

• Demand for higher data rate is leading to utilization of wider transmission bandwidth.

Up to 20 MHzLTE, UMB, WiMAX3.5~4G

5 MHzcdma2000

5 MHzWCDMA3G

1.25 MHzIS-95 (CDMA)

200 kHzGSM2G

Transmission bandwidthStandard



Broadband Multipath ChannelBroadband Multipath ChannelBroadband Multipath ChannelBroadband Multipath Channel

• Multi-path channel causes:

– Inter-symbol interference (ISI) and fading in the time domain.

– Frequency-selectivity in the frequency domain.

0 1 2 3 4 5 60

0.2

0.4

0.6

0.8

1

Time [µsec]

Am

plitu

de [

linea

r]

3GPP 6-Tap Typical Urban (TU6) Channel Delay Profile

0 1 2 3 4 50

0.5

1

1.5

2

2.5

Frequency [MHz]

Cha

nnel

Gai

n [li

near

]

Frequency Response of 3GPP TU6 Channel in 5MHz Band


- cont.


Frequency Domain EqualizationFrequency Domain EqualizationFrequency Domain EqualizationFrequency Domain Equalization

• For broadband multi-path channels, conventional time

domain equalizers are impractical because of complexity.

– Very long channel impulse response in the time domain.

– Prohibitively large tap size for time domain filter.

• Using discrete Fourier transform (DFT), equalization can be

done in the frequency domain.

• Because the DFT size does not grow linearly with the length of the channel response, the complexity of FDE is lower than that

of the equivalent time domain equalizer for broadband

channel.



FDEFDEFDEFDE

hx y

1 *

y h x

x h y−

= ∗∴ =

1

Y H X

X H Y−

= ⋅∴ = ⋅

Time domain

Frequency domain

Fouriertransform

Channel

- cont.



• In DFT, frequency domain multiplication is equivalent to time domain

circular convolution.

• Cyclic prefix (CP) longer than the channel response length is

needed to convert linear convolution to circular convolution.

FDEFDEFDEFDE

CP Symbols

- cont.



FDEFDEFDEFDE

• Most of the time domain equalization techniques can be

implemented in the frequency domain.

– MMSE equalizer, DFE, turbo equalizer, and so on.

• References

– M. V. Clark, “Adaptive Frequency-Domain Equalization and

Diversity Combining for Broadband Wireless Communications,”

IEEE J. Sel. Areas Commun., vol. 16, no. 8, Oct. 1998

– M. Tüchler et al., “Linear Time and Frequency Domain Turbo

Equalization,” Proc. IEEE 53rd Veh. Technol. Conf. (VTC), vol. 2,

May 2001

– F. Pancaldi et al., “Block Channel Equalization in the Frequency

Domain,” IEEE Trans. Commun., vol. 53, no. 3, Mar. 2005

- cont.



Single Carrier with FDESingle Carrier with FDESingle Carrier with FDESingle Carrier with FDE

ChannelN-

point IDFT

EqualizationN-

pointDFT

SC/FDE

OFDM

DetectRemove

CP{ }nxAdd CP/ PS

* CP: Cyclic Prefix, PS: Pulse Shaping

Channel EqualizationN-

pointDFT

DetectRemove

CP

N-point IDFT

Add CP/ PS

{ }nx



SC/FDESC/FDESC/FDESC/FDE

• SC/FDE delivers performance similar to OFDM with essentially the same overall complexity, even for long channel delay.

• SC/FDE has advantage over OFDM in terms of:

– Low PAPR.

– Robustness to spectral null.

– Less sensitivity to carrier frequency offset.

• Disadvantage to OFDM is that channel-adaptive subcarrier bit

and power loading is not possible.

- cont.



SC/FDESC/FDESC/FDESC/FDE

• References

– H. Sari et al., “Transmission Techniques for Digital Terrestrial TV Broadcasting,” IEEE Commun. Mag., vol. 33, no. 2, Feb. 1995, pp. 100-109.

– D. Falconer et al., “Frequency Domain Equalization for Single-Carrier Broadband Wireless Systems,” IEEE Commun. Mag., vol. 40, no. 4, Apr. 2002, pp. 58-66.

• Single Carrier FDMA (SC-FDMA) is an extension of SC/FDE to accommodate multiple-user access.

- cont.



CDMA with FDECDMA with FDECDMA with FDECDMA with FDE

• Instead of a RAKE receiver, use frequency domain equalization for channel equalization.

• Reference

– F. Adachi et al., “Broadband CDMA Techniques,” IEEE Wireless

Comm., vol. 12, no. 2, Apr. 2005, pp. 8-18.

Spreading ChannelM-

point IDFT

EqualizationM-

pointDFT

DetectRemove

CP{ }nxAdd CP/ PS

De-spreading



Overview of SC-FDMA






Single Carrier FDMASingle Carrier FDMASingle Carrier FDMASingle Carrier FDMA

• SC-FDMA is a new multiple access technique.

– Utilizes single carrier modulation, DFT-spread orthogonal

frequency multiplexing, and frequency domain equalization.

• It has similar structure and performance to OFDMA.

• SC-FDMA is currently adopted as the uplink multiple access

scheme in 3GPP LTE.

– A variant of SC-FDMA using code spreading is used in 3GPP2

UMB uplink.

– 802.16m also considering it for uplink.

Overview of SC-FDMA


TX & RX Structure of SCTX & RX Structure of SCTX & RX Structure of SCTX & RX Structure of SC----FDMAFDMAFDMAFDMA

Subcarrier Mapping

Channel

N-point IDFT

Subcarrier De-mapping/ Equalization

M-pointDFT

DetectRemove

CP

N-point DFT

M-point IDFT

Add CP / PS

DAC/ RF

RF/ ADC

SC-FDMA:

OFDMA:

+* N < M* S-to-P: Serial-to-Parallel* P-to-S: Parallel-to-Serial

P-to-S

S-to-P

S-to-P

P-to-S

Overview of SC-FDMA


Why Why Why Why “ Single CarrierSingle CarrierSingle CarrierSingle Carrier” “ FDMAFDMAFDMAFDMA” ????

Subcarrier Mapping

N-point DFT

M-point IDFT

Add CP / PS

DAC/ RF

Timedomain

Frequencydomain

Timedomain

“FDMA”

“Single Carrier”

P-to-S

: Sequential transmission of the symbols over a single frequency carrier.

: User multiplexing in the frequency domain.

Overview of SC-FDMA


Subcarrier MappingSubcarrier MappingSubcarrier MappingSubcarrier Mapping

• Two ways to map subcarriers; distributed and localized.

• Distributed mapping scheme for (total # of subcarriers) =

(data block size) × (bandwidth spreading factor) is called Interleaved FDMA (IFDMA).

Distributed Localized

0X

1NX −

1X

Zeros

Zeros0Xɶ

1MX −ɶ

Zeros

0X

Zeros

1X

2X

1NX −

0Xɶ

1MX −ɶ

Zeros

Overview of SC-FDMA



• Data block size (N) = 4, Number of users (Q) = 3, Number of subcarriers (M) = 12.

subcarriers

Terminal 1

Terminal 2

Terminal 3

subcarriers

Distributed Mode Localized Mode

- cont.

Overview of SC-FDMA



0 0 0 0 0 0 0 0X0 X1 X2 X3

frequency

0 0 0 0 0 0 0 0X0 X1 X2 X3

{ } :kX X0 X1 X2 X3

{ } :nx x0 x1 x2 x3

DFT

21

0

, 4N j nk

Nk n

n

X x e Nπ− −

=

= =

∑

{ }IFDMAlX ,

~

0 0 00 0 0 0 0X0 X1 X2 X3{ }DFDMAlX ,

~

{ }LFDMAlX ,

~ Current implementationin 3GPP LTE

- cont.

Overview of SC-FDMA


Time Domain RepresentationTime Domain RepresentationTime Domain RepresentationTime Domain Representation

x0 x1 x2 x3

x0 x1 x2 x3

{ }nx

x0 x1 x2 x3 x0 x1 x2 x3

* * * * * * * *x0 x2 x0 x2

time

* * * * * * * *x0 x1 x2 x3

{ },m IFDMAQ x⋅ ɶ

{ },m DFDMAQ x⋅ ɶ

{ },m LFDMAQ x⋅ ɶ

3

, ,0

* , : complex weightk m k k mk

c x c=

= ⋅∑

Overview of SC-FDMA


Amplitude of SCAmplitude of SCAmplitude of SCAmplitude of SC----FDMA SymbolsFDMA SymbolsFDMA SymbolsFDMA Symbols

10 20 30 40 50 600

0.1

0.2

0.3

0.4

0.5

Symbol

Am

plitu

de [l

inea

r]

IFDMALFDMADFDMA

QPSK

Overview of SC-FDMA


SCSCSCSC----FDMA and OFDMA FDMA and OFDMA FDMA and OFDMA FDMA and OFDMA

• Similarities

– Block-based modulation and use of CP.

– Divides the transmission bandwidth into smaller subcarriers.

– Channel inversion/equalization is done in the frequency domain.

– SC-FDMA is regarded as DFT-precoded or DFT-spread OFDMA.

Overview of SC-FDMA



• Difference in time domain signal

OFDMA symbol

SC-FDMA symbols*

Input data symbols

* Bandwidth spreading factor : 4time

- cont.

Overview of SC-FDMA



• Different equalization/detection aspects

Subcarrier De-

mapping

Equalizer

Equalizer

Equalizer

Subcarrier De-

mapping

Detect

Detect

Detect

Equalizer IDFT DetectSC-FDMA

OFDMA DFT

DFT

- cont.

Overview of SC-FDMA


SCSCSCSC----FDMA and DSFDMA and DSFDMA and DSFDMA and DS----CDMACDMACDMACDMA

• In terms of bandwidth expansion, SC-FDMA is very similar to

DS-CDMA system using orthogonal spreading codes.

– Both spread narrowband data into broader band.

– Time symbols are compressed into “chips” after modulation.– Spreading gain (processing gain) is achieved.

Overview of SC-FDMA



• Conventional spreading

x1 x2 x3

1 1 1

x1 x1 x1 x1 x2 x2 x2 x2 x3 x3 x3 x3

1 1 1 1 1 1 1 1 1

Signature Sequence

Data Sequence ××××

time

x0 x0 x0 x0

1 1 1 1

x0

- cont.

Overview of SC-FDMA



• Exchanged spreading

time

1

x0 x1 x2 x3

1 1

x0 x1 x2 x3 x0 x1 x2 x3

x0 x1 x2 x3 x0 x1 x2 x3 x0 x1 x2 x3

××××

Data Sequence

Signature Sequence

x0 x1 x2 x3

x0 x1 x2 x3

1

IFDMA

- cont.

Overview of SC-FDMA

*C. Chang, and K. Chen, “Frequency-Domain Approach to Multiuser Detection over Frequency-Selective Slowly Fading Channels,” IEEE PIMRC 2002, Lisboa, Portugal, Sep., 2002, pp. 1280-1284


SCSCSCSC----FDMA and Other SchemesFDMA and Other SchemesFDMA and Other SchemesFDMA and Other Schemes

SC-FDMA

OFDMADS-CDMA

/FDE* DFT-based FDE

* Block-based processing & CP

* SC transmission: Low PAPR

* Time-compressed “chip” symbols

* Time-domain detection

* Subcarrier mapping: Frequency-selective scheduling

Overview of SC-FDMA


SCSCSCSC----FDMA with Code SpreadingFDMA with Code SpreadingFDMA with Code SpreadingFDMA with Code Spreading

Subcarrier Mapping

Channel

N-point IDFT

Subcarrier De-mapping/

Equalization

M-pointDFT

Detect

Remove CP

N-point DFT

M-point IDFT

Add CP/ PS

SpreadingDe-

spreadingSC-FDMA Modulation SC-FDMA Demodulation

Overview of SC-FDMA


SCSCSCSC----FDMA MIMOFDMA MIMOFDMA MIMOFDMA MIMO

Subcarrier Mapping

MIMOChannel

N-point IDFT

Subcarrier De-mapping

M-pointDFT

DetectRemove

CP

N-point DFT

M-point IDFT

Add CP / PS

DAC/ RF

RF/ ADC

Spatial Mapping

Subcarrier Mapping

N-point DFT

M-point IDFT

Add CP / PS

DAC/ RF

Spatial Combining

/ Equalization

N-point IDFT

Subcarrier De-mapping

M-pointDFT

DetectRemove

CPRF

/ ADC

Overview of SC-FDMA


Overview of SC-FDMA






LTE Frame StructureLTE Frame StructureLTE Frame StructureLTE Frame Structure

• Two radio frame structures defined.

– Frame structure type 1 (FS1): FDD.

– Frame structure type 2 (FS2): TDD.

• A radio frame has duration of 10 ms.

• A resource block (RB) spans 12 subcarriers over a slot duration

of 0.5 ms. One subcarrier has bandwidth of 15 kHz, thus 180

kHz per RB.



LTE Frame Structure Type 1LTE Frame Structure Type 1LTE Frame Structure Type 1LTE Frame Structure Type 1

• FDD frame structure

One subframe = TTI (Transmission Time Interval)

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

One slot = 0.5 ms

One radio frame = 10 ms



LTE Frame Structure Type 2LTE Frame Structure Type 2LTE Frame Structure Type 2LTE Frame Structure Type 2

• TDD frame structure

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

DwPTS GP UpPTS DwPTS GP UpPTS

One subframe = 1 ms

One half-frame = 5 ms

One radio frame = 10 ms

One slot = 0.5 ms



LTE Resource GridLTE Resource GridLTE Resource GridLTE Resource Grid

Slot #0 #19

One radio frame

Subcarrier (frequen

cy)

OFDM/SC-FDMA symbol (time)

RBRB scN N×

12

RBscN

=

symbN

Resource block

Resource element

RBsymb scN N= × resource elements



Length of CPLength of CPLength of CPLength of CP

symbN

6Extended CP

3Extended CP (∆f = 7.5 kHz)†

7Normal CP

Configuration

512 (≈ 16.67 µs) for l = 0, 1, …, 5Extended CP

1024 (≈ 33.33 µs) for l = 0, 1, 2Extended CP (∆f = 7.5 kHz) †

160 (≈ 5.21 µs) for l = 0144 (≈ 4.69 µs) for l = 1, 2, …, 6

Normal CP

CP length NCP,l [samples]Configuration

† Only in downlink



LTE Bandwidth/Resource ConfigurationLTE Bandwidth/Resource ConfigurationLTE Bandwidth/Resource ConfigurationLTE Bandwidth/Resource Configuration

1536011520768038401920960Samples per slot

30.7223.0415.367.683.841.92Sample rate [MHz]

204815361024512256128IDFT(Tx)/DFT(Rx)

size

120090060030018072Number of

occupied subcarriers

100755025156Number of

resource blocks (NRB)

201510531.4Channel

bandwidth [MHz]

*3GPP TS 36.104



LTE Bandwidth ConfigurationLTE Bandwidth ConfigurationLTE Bandwidth ConfigurationLTE Bandwidth Configuration

frequen

cy

time

300

RBRB scN N×=12

RBscN

=(7.68 MHz)

512

M

=(4.5 MHz)(180 kHz)

Resourceblock

Zeros

Zeros

1 slot

DL or UL symbol

* 5 MHz system withframe structure type 1



UL Overview UL Overview UL Overview UL Overview

• UL physical channels

– Physical Uplink Shared Channel (PUSCH)

– Physical Uplink Control Channel (PUCCH)

– Physical Random Access Channel (PRACH)

• UL physical signals

– Reference signal (RS)

• Available modulation for data channel

– QPSK, 16-QAM, and 64-QAM

• Single user MIMO not supported in current release.

– But it will be addressed in the future release.

– Multi-user collaborative MIMO supported.



UL Resource BlockUL Resource BlockUL Resource BlockUL Resource Block

1 slot (0.5 ms)

Resourceblock (RB)

Frequency

Time

One SC-FDMA symbol

Subcarrier

Referencesymbols (RS)

*PUSCH with normal CP



UL Physical Channel ProcessingUL Physical Channel ProcessingUL Physical Channel ProcessingUL Physical Channel Processing

Scrambling

Modulation mapping

Transform precoding

SC-FDMA signal generation

Resource element mappingSC-FDMAmodulation

DFT-precoding

IDFT operation



SCSCSCSC----FDMA Modulation in LTE ULFDMA Modulation in LTE ULFDMA Modulation in LTE ULFDMA Modulation in LTE UL

Serial-to-

Parallel

M-IDFT

N-DFT

Zeros

{ }0 1 1, , Nx x x −…

Parallel-to-Serial

{ }0 1 1, , Mx x x −ɶ ɶ ɶ…

Subcarrier Mapping

subcarrier

0M-1

Zeros

One SC-FDMA symbol

Localized mapping with an option of adaptive scheduling or random hopping.



UL Reference SignalUL Reference SignalUL Reference SignalUL Reference Signal

• Two types of UL RS

– Demodulation (DM) RS ⇒ Narrowband.

– Sounding RS: Used for UL resource scheduling ⇒ Broadband.

• RS based on Zadoff-Chu CAZAC (Constant Amplitude Zero

Auto-Correlation) polyphase sequence

– CAZAC sequence: Constant amplitude, zero circular auto-

correlation, flat frequency response, and low circular cross-

correlation between two different sequences.

2

2 , 0,1,2, , 1; for even2

( 1)2 , 0,1,2, , 1; for odd

2

k

r kj qk k L L

L

r k kj qk k L L

L

ea

e

π

π

− + = −

+ − + = −

=

⋯

⋯

* r is any integer relatively prime with L and q is any integer.

B. M. Popovic, “Generalized Chirp-like Polyphase Sequences with Optimal Correlation Properties,”IEEE Trans. Info. Theory, vol. 38, Jul. 1992, pp. 1406-1409.



UL RS MultiplexingUL RS MultiplexingUL RS MultiplexingUL RS Multiplexing

subcarriers

User 1

User 2

User 3

subcarriers

FDM Pilots CDM Pilots



UL RS MultiplexingUL RS MultiplexingUL RS MultiplexingUL RS Multiplexing

• DM RS

– For SIMO: FDM between different users.

– For SU-MIMO: CDM between RS from each antenna

– For MU-MIMO: CDM between RS from each antenna

• Sounding RS

– CDM when there is only one sounding bandwidth.

– CDM/FDM when there are multiple sounding bandwidths.

- cont.



Overview of SC-FDMA






0 2 4 6 8 10 1210

-4

10-3

10-2

10-1

100

Pr(

PA

PR

>P

AP

R0)

PAPR0 [dB]

CCDF of PAPR: 16-QAM, Rolloff = 0.22, Nfft

= 512, Noccupied

= 128

Dotted lines: no PSDashed lines: RRC PSSolid lines: RC PS

IFDMA

DFDMA

LFDMA

OFDMA

PAPR CharacteristicsPAPR CharacteristicsPAPR CharacteristicsPAPR Characteristics

* Monte Carlo simulations (Number of iterations: > 104)* Time domain pulse shaping with 8-times oversampling* Nfft: number of total subcarriers = FFT size* Noccupied: number of occupied subcarriers = data block size* RC: raised-cosine, RRC: root raised-cosine* Rolloff factor of 0.22


(a) QPSK (b) 16-QAM

0 2 4 6 8 10 1210

-4

10-3

10-2

10-1

100

Pr(

PA

PR

>P

AP

R0)

PAPR0 [dB]

CCDF of PAPR: QPSK, Rolloff = 0.22, Nfft

= 512, Noccupied

= 128

Dotted lines: no PSDashed lines: RRC PSSolid lines: RC PS

IFDMA

DFDMA

LFDMA

OFDMA

*H. G. Myung, J. Lim, and D. J. Goodman, "Peak-to-Average Power Ratio of Single Carrier FDMA Signals with Pulse Shaping," IEEE PIMRC ’06, Helsinki, Finland, Sep. 2006


PAPR CharacteristicsPAPR CharacteristicsPAPR CharacteristicsPAPR Characteristics

• PAPR and different rolloff factors

*α: rolloff factor of raised cosine pulse shaping filter

0 2 4 6 8 1010

-4

10-3

10-2

10-1

100

Pr(

PA

PR

>P

AP

R0)

PAPR0 [dB]

CCDF of PAPR: QPSK, Nfft

= 256, Noccupied

= 64

Solid lines: without pulse shapingDotted lines: with pulse shaping

IFDMA LFDMA

α=0.4α=0.6α=0.2

α=0

α=0.8

α=1


*H. G. Myung, J. Lim, and D. J. Goodman, "Peak-to-Average Power Ratio of Single Carrier FDMA Signals with Pulse Shaping," IEEE PIMRC ’06, Helsinki, Finland, Sep. 2006

- cont.


PAPR of SCPAPR of SCPAPR of SCPAPR of SC----FDMA FDMA FDMA FDMA MIMOMIMOMIMOMIMO

4 6 8 10 12

10-4

10-3

10-2

10-1

100

PAPR0 [dB]

Pr(

PA

PR

>P

AP

R0)

SM

SFBC (QPSK)

SFBC (16-QAM)

TxBF(avr. & quant.)

TxBF(no avr. & no quant.)


*H. G. Myung, J.-L. Pan, R. Olesen, and D. Grieco, "Peak Power Characteristics of Single Carrier FDMA MIMO Precoding System", IEEE VTC 2007 Fall, Baltimore, USA, Oct. 2007


Overview of SC-FDMA






ChannelChannelChannelChannel----Dependent Scheduling (CDS)Dependent Scheduling (CDS)Dependent Scheduling (CDS)Dependent Scheduling (CDS)

• Channel-dependent scheduling

– Assign subcarriers to a user in

excellent channel condition.

• Two subcarrier mapping

schemes have advantages over

each other.

– Distributed: Frequency diversity.

– Localized: Frequency selective

gain with CDS.

Subcarriers

Frequency

User 1

User 2

Channel gain



CDSCDSCDSCDS

*J. Lim, H. G. Myung, K. Oh, and D. J. Goodman, "Proportional Fair Scheduling of Uplink Single-Carrier FDMA Systems", IEEE PIMRC 2006, Helsinki, Finland, Sep. 2006

4 8 16 32 64 1285

10

15

20

25

30

35

40

45

Number of users

Agg

rega

te th

roug

hput

[Mbp

s]

R-LFDMA

S-LFDMAR-IFDMAS-IFDMA

4 8 16 32 64 1285

10

15

20

25

30

35

40

45

Number of users

Agg

rega

te th

roug

hput

[Mbp

s]

R-LFDMAS-LFDMAR-IFDMA

S-IFDMA

Utility: sum of user throughput Utility: sum of logarithm of user throughput

* Capacity based on Shannon’s upper bound.* Time synchronized uplink data transmission.* Perfect channel knowledge.* No feedback delay or error.


- cont.


Uplink SCUplink SCUplink SCUplink SC----FDMAFDMAFDMAFDMA

with Adaptive Modulation and CDSwith Adaptive Modulation and CDSwith Adaptive Modulation and CDSwith Adaptive Modulation and CDS

Channel K

Resource Scheduler

Channel 2

Subcarrier

Mapping

Channel 1IDFTCP / PS

DFT

ConstellationM

apping

SC-FDMA Receiver

User 1

User 2

User K

Data flow

Control signal flow

Mobile terminals Base station



Simulation ResultsSimulation ResultsSimulation ResultsSimulation Results

• Aggregate throughput vs. feedback delay

0 1 2 3 4 52

4

6

8

10

12

14

16

18

Feedback delay [ms]

Agg

rega

te th

roug

hpu

t [M

bps]

mobile speed = 3 km/h (fD

= 5.6 Hz)

LFDMA: StaticLFDMA: CDSIFDMA: StaticIFDMA: CDS

0 1 2 3 4 52

4

6

8

10

12

14

16

18

Feedback delay [ms]

Agg

rega

te t

hrou

ghpu

t [M

bps

]

mobile speed = 60 km/h (fD = 111 Hz)

LFDMA: Static

LFDMA: CDSIFDMA: Static

IFDMA: CDS

* Carrier frequency = 2 GHz

* K = 64 total number of users, N = 16 subcarriers per chunk, Q = 16 total number of chunks

* Utility: sum of user throughput


*H. G. Myung, K. Oh, J. Lim, and D. J. Goodman, "Channel-Dependent Scheduling of an Uplink SC-FDMA System with Imperfect Channel Information," IEEE WCNC 2008, Las Vegas, USA, Mar. 2008


Simulation ResultsSimulation ResultsSimulation ResultsSimulation Results

• Aggregate throughput vs. mobile speed

0 20 (37) 40 (74) 60 (111) 80 (148)2

4

6

8

10

12

14

16

18

Mobile speed [km/h] (Doppler [Hz])

Ag

greg

ate

thro

ugh

put [

Mb

ps]

Feedback delay = 3 ms

LFDMA: Static

LFDMA: CDSIFDMA: StaticIFDMA: CDS


- cont.

*H. G. Myung, K. Oh, J. Lim, and D. J. Goodman, "Channel-Dependent Scheduling of an Uplink SC-FDMA System with Imperfect Channel Information," IEEE WCNC 2008, Las Vegas, USA, Mar. 2008.


Overview of SC-FDMA






Summary and ConclusionsSummary and ConclusionsSummary and ConclusionsSummary and Conclusions

• SC-FDMA is a new single carrier multiple access technique

which has similar structure and performance to OFDMA.

– Currently adopted for uplink multiple access scheme for 3GPP

LTE.

• Two types of subcarrier mapping, distributed and localized,

give system design flexibility to accommodate either

frequency diversity or frequency selective gain.

• A salient advantage of SC-FDMA over OFDM/OFDMA is low

PAPR.

– Efficient transmitter and improved cell-edge performance.

• Pulse shaping as well as subcarrier mapping scheme has a

significant impact on PAPR.



References and ResourcesReferences and ResourcesReferences and ResourcesReferences and Resources

• H. G. Myung, J. Lim, & D. J. Goodman, “Single Carrier FDMA for Uplink Wireless Transmission,” IEEE Vehic. Tech. Mag., vol. 1, no. 3, Sep. 2006

• H. Ekström et al., “Technical Solutions for the 3G Long-Term Evolution,” IEEE Commun. Mag., vol. 44, no. 3, Mar. 2006

• D. Falconer et al., “Frequency Domain Equalization for Single-Carrier Broadband Wireless Systems,” IEEE Commun. Mag., vol. 40, no. 4, Apr. 2002

• H. Sari et al., “Transmission Techniques for Digital Terrestrial TV Broadcasting,” IEEE Commun. Mag., vol. 33, no. 2, Feb. 1995



References and ResourcesReferences and ResourcesReferences and ResourcesReferences and Resources

• LTE Spec– http://www.3gpp.org/ftp/Specs/html-info/36-series.htm

• SC-FDMA resource page– http://hgmyung.googlepages.com/scfdma

• Comprehensive list of SC-FDMA papers– http://hgmyung.googlepages.com/scfdma2


- cont.


Final WordFinal WordFinal WordFinal Word

SC-FDMA Low PAPR�


Thank you!

May 18, 2008

Hyung G. Myung ([email protected])

Documents

Single Carrier FDMA - KFUPMfaculty.kfupm.edu.sa/coe/ashraf/richfilesteaching/COE082_543/... · Single Carrier FDMA May18,2008 HyungG.Myung ... SC-FDMA Implementation in 3GPP LTE