l Ti h Wl bdBd Broadband Wireless Technology · 2010-09-08 · l Ti h Wl bdBd Wireline/Wireless...

B db d Wi l T h l

Wireline/Wireless Technology Forum, Sarajevo, Bosnia and Herzegovina,7 May 2010

Broadband Wireless TechnologyF i ki Ad hi Tohoku U. Aobayama-campusFumiyuki Adachi

Wireless Signal Processing & Networking (WSP&N) Lab.

Dept of Electrical and

Tohoku U. Aobayama campus

Dept. of Electrical and Communications Engineering,

Tohoku University, JapanE-mail: adachi@ecei tohoku ac jpE-mail: [email protected]

http://www.mobile.ecei.tohoku.ac.jp/

OUTLINE

Matsushima

OUTLINEWireless Evolution3.9G (LTE) SystemsChallenge fo F t e Wi elessChallenge for Future WirelessAdvanced FDE for SC Signal Transmission Distributed Antenna Network

2010/05/07 FA/Tohoku University 1

Distributed Antenna Network (DAN)Concluding Remarks

i l l iWireless Evolution

From 2G to 3G systemsThen, from 3G to 3.9G (LTE) systems


F. Adachi, “Wireless past and future - evolving mobilecommunications systems,” IEICE Trans. Fundamentals, vol.E84-A, pp. 55-60，Jan. 2001.

Wi l E l tiWireless EvolutionIn early 1980’s, communications systems changed fromIn early 1980 s, communications systems changed fromfixed “point-to-point” to wireless “anytime, anywhere”communication.C ll l t h l d f b d t k fCellular systems have evolved from narrowband network ofaround 10kbps to wideband networks of around 10Mbps.Now on the way to broadband networks of 1Gps.Now on the way to broadband networks of 1Gps.

NarrowbandEraed

ia

i t

WidebandEra

BroadbandEra

2G~64kbps

1G~2.4kbpsyp

eultim

e

3G~2Mbps

4G100M~1Gbps

point-to-point

50 100Mbps

Broadbandrvic

e ty M

HSDPA

~14Mbps0GVoice only 3G LTE

50~100Mbps

BroadbandwirelessS

eroic

e

W-CDMACDMA2000TD-SCDMA

HSDPA(W-CDMA)

2010/05/07 FA/Tohoku University 3We are here1980 1990 2000 Year

Vo

2010

There was a big technical leap from 2G to 3GThere was a big technical leap from 2G to 3Gsystems.

V i V i DataVoice+data Voice+Data

1GA l

2GDi i l

3GDigital

Big

Analog(FDMA)

Digital(TDMA)

Digital(CDMA)

leap

Improved frequency utilization

NarrowbandIncreased peak rateIncreased no. of

Broadband

2010/05/07 4FA/Tohoku University

Increased throughputchannels

Multiple access technique used in cellular systemsMultiple access technique used in cellular systemshas been changed from FDMA to DS-CDMA.

FDMA was used in 1GFDMA was used in 1GTDMA in 2GDS-CDMA in 3G

FDMAf3

1G

ncy Ex. 6.25kHz

f2f1

uen

cy

Freq

uen

Time

TDMA

2GSingle-carrier

DS-CDMA3G

Freq

u

# 2# 3

quen

cy

TDMA

1 3 1 2 32

Ti

Spreading code#1

Ex.

5M

Hz


Fre

Time

Time20ms E

25kHz

On-going Shift To 3G Systems(J )(Japan)

3G services (~384kbps) ( p )started in 2001 in Japan. Growth rate of 3G systems were very slow in the first 1 00E+08

1.20E+083G/W-CDMA

3G/CDMA20001x

were very slow in the first few years, but now it is really taking off. 8.00E+07

1.00E+082G

Total no. of cellular subscribers @end of Dec. 2009

6.00E+07

009110,176,700 (penetration:86.3 %)

2G (4 443 600)

4.00E+07

2G (4,443,600)PDC： 4,172,800

cdmaOne: 270,800

2.00E+07

,

3G (106,173,700)96.4 % of total

0.00E+00

W-CDMA: 75,051,600CDMA2000 1x: 31,122,100


G i Wi l I t tGrowing Wireless InternetBroadband multimedia servicesBroadband multimedia services

In line with the increasing popularity of Internet in fixednetworks, cellular systems are evolving from simply, y g p yproviding traditional voice communication services toproviding broadband multimedia services throughInternet accessInternet access.

Internet cell phones @end of Dec. 2009 (source: TCA)

T t l ll l 110 176 700 ( t ti 86 3%*)Total cellular users: 110,176,700 (penetration 86.3%*)Users connected to Internet: 92,287,700 (83.8%)

i mode (DoCoMo): 48 688 200i-mode (DoCoMo): 48,688,200Ezweb (au): 26,597,200Yahoo Ke-tai (SoftBank): 16,945,700Yahoo Ke tai (SoftBank): 16,945,700EMnet (EMOBILE): 56,600

* Japan population estimate:127.69m @Oct. 2005


( )3.9G (LTE) Systems


B f 4G Th Will B 3 9GBefore 4G, There Will Be 3.9G3G systems will continue to evolve to meet the3G systems will continue to evolve to meet thedemands of (internet-related) broadband wirelessservices and substantially strengthen its downlinkservices and substantially strengthen its downlinkdata rate capability.

High-speed downlink packet access (HSDPA) ofHigh speed downlink packet access (HSDPA) of~14Mbps/5MHz, called 3.5G systems, started in Japanin 2006.Even 3.5G of ~14Mbps will sooner or later becomeinsufficient.A 3 9G (3G LTE) will appear to provide broadbandA 3.9G (3G LTE) will appear to provide broadbandservices of 50~100Mbps/20MHz using the 3G bands.

3 5G 3 9G

DS-CDMA(DL/UL) OFDMA(DL),SC-FDMA(UL)

3.5G 3.9G


(~14Mbps) SC-FDMA(UL)(50~100Mbps)

B f 4G Th Will B 3 9GBefore 4G, There Will Be 3.9G3G band will be used3G band will be used

No available bandwidth of 100MHz (a hot matter ofWRC-07))Present 3G bandwidth (1.25~20MHz) will be used toprovide much faster rate data servicesTarget: 100Mbps for downlink, 50Mbps for uplink

Difference from 3G wireless technologygy3~3.5G ： DS-CDMA (DL/UL) 3.9G: OFDMA(DL)/SC-FDMA(UL)Promising transmission performance and goodcommonality with WLAN


Wi l A f 3 9GWireless Access of 3.9GDifferent multi-access techniques between downlink andDifferent multi access techniques between downlink anduplink (this is the first time in the history)

Downlink: OFDMA, ~100Mbps Downlink and uplink Uplink: SC-FDMA, ~50Mbps

Scheduling for packet accessM lti di it i i l h l

access schemes are different

Multiuser diversity in wireless channelHybrid ARQ using incremental redundancy (IR) strategyNon real time servicesNon real time services

Downlink Uplink

Bandwidth(MHz) 1 4/3/5/10/15/20Bandwidth(MHz) 1.4/3/5/10/15/20

IFFT/FFT block size

128/256/512/1024/1536/2048size

Multi-access OFDMA SC-FDMA

Scheduling Multi-user diversity gain


g y g

ARQ Turbo-coded IR-HARQ

Uplink and Downlink Access T h i A Diff tTechniques Are Different

For a long time, the same access technique has beeng , qadopted for the uplink and downlink.Different multi-access techniques between downlink anduplink (this is the first time in the history)uplink (this is the first time in the history)

Downlink: Probably MC-based multi-access is moreappropriate since high PAPR is not a big problem at the baset tistation.

Uplink: as the data rates increases, the PAPR problembecomes more serious. SC-based multi-access is more

b f lappropriate because of its lower PAPR.

Base station(DL)Higher peak power amp.(UP) Complex MMSE-FDE

Mobile terminal(UL) Lower peak power amp


(UL) Lower peak power amp.(DL) Simple ZF-FDE

OFDMA D li k OFDMA Downlink Resource allocation: one or more resource blocks of 1msecResource allocation: one or more resource blocks of 1msecand 12 subcarriers (180kHz) each are allocated accordingto each user’s channel condition (scheduling) to obtain

lti di it imultiuser diversity gainProportional fairness (PF)* scheduling can maximize thethroughput while keeping fairness among usersthroughput while keeping fairness among users

User A User B User Cn

CodedOFDMAsignal

User A

User B

User A User B User C

nnel

gai

Nc-pointIFFT

Codeddata

signal+GI

User B

User C Freq.Chan

Freq* A Jalali R Padovani and R Pankaj “Data throughput of CDMA-


Freq.12 subcarriers(180kHz)

A. Jalali, R. Padovani, and R. Pankaj, Data throughput of CDMAHDR a high efficiency-high data rate personal communication wireless system,” Proc. IEEE VTC 2000-Spring, vol. 3, pp. 1854 -1858, Tokyo, 15-18May 2000.

Frequency and time -domain schedulingFrequency and time domain scheduling

U B

Frequency

A B

B

User B1ms

A

A

B

Bme

AB

B A

Tim

A

B

B BS

User A

AB

BS


12 subcarriers(180kHz)

Why Single-carrier (SC)T i i f U li k?Transmission for Uplink?

SC has lower PAPR than 3

4

α= 0.00SC has lower PAPR than OFDM.

No ISI at different symbol iti

0

1

2

55 57 59 61 63 65positions.

SC is suitable for the uplink transmission 4

-3

-2

-1 55 57 59 61 63 65

4transmission.Less expensive power amplifier is required.

-4

1

2

3

4

α= 0.50

SC

-2

-1

055 57 59 61 63 65

SC waveform

4

OFDMA waveform

3

4

α= 1.00

-4

-3

1

2

3

4OFDM

256 subcarriers

0

1

2

55 57 59 61 63 65-2

-1

055 57 59 61 63 65


-3

-2

-1 55 57 59 61 63 65

-4

-3

Frequency-domain E li ti I P f lEqualization Is Powerful

Frequency-domain equalization (FDE)Frequency domain equalization (FDE)With FDE, both SC and OFDM can take advantage of thechannel frequency-selectivity and have a similar improved BERpe fo manceperformance.

Similar transmitter/receiver structure

Transmit data ta

mod.

rtio

n o

f G

I

MCc-P

oin

t IF

FT GI Nc symbols

Copy

Dat

Inse

r

SC Nc

Transmitter

Ng symbols

Received d t

Data d

Nc-Po

Rem

ovFDMCdata

dem

od.

oin

t FFT

val of G

I

DEMC

SCNc-I F


ReceiverPo

int

FFT

BER Performance I tImprovement

BER performance of SC BER performance of SC can be significantly improved with MMSE-FDE

1.0E+00MRC

FDE.However, there is still a big performance gap

1.0E-01 EGC

big performance gap from the theoretical lower bound.

1.0E-02

age B

ER

Matchedfilter boundLower bound

This is due to residual ISI after MMSE-FDE.Introduction of ISI

1.0E-03Ave

raMMSE

ZFL=16-pathuniform power

e bou d

Introduction of ISI cancellation technique can reduce the

f

1.0E-04delay profileQPSKNc=256N 32performance gap.

F. Adachi, Kazuki Takeda, and H. Tomeba, “Introduction of

1.0E-050 5 10 15 20

i d / (d )

Ng=32


Frequency-Domain Signal Processing to Broadband Single-Carrier Transmissions in a Wireless Channel,” IEICE Trans.Commun., Vol. E92-B, No.09, pp.2789-2808, Sep. 2009.

Average received Eb/N0 (dB)

SC FDMASC-FDMAUplink MAIUplink MAI

The MAI can be avoided by combining SC-FDE with either FDMA orCDMA, while alleviating the complexity problem of MUD (remainingproblem is the avoidance of other-cell MAI)problem is the avoidance of other cell MAI).

SC-FDMA is a combination of SC-FDE and FDMAA block of data symbols to be transmitted is transformed intofrequency-domain signal which is then mapped onto a different set ofsubcarriers of OFDM.To preserve the low PAPR property of SC-FDMA signals, equidistancespectrum mapping (either localized or equidistantly distributed) isused.

Coded SC FDMATransmitFilter

M-pointDFT

Nc-pointIFFT

Coded data

SC-FDMAsignal+GIMapping

# R. Dinis, D. Falconer, C. T. Lam, and M. Sabbaghian,Proc. GlobeCom2004, vol.6, pp. 3808-3812, Dallas,TX, USA, 29 Nov.-3 Dec. 2004

・・・

User u

f


, ,# K. Takeda and F. Adachi, Proc. IEEE VTC2005-Fall,

Dallas, U.S.A., 26-28 Sept. 2005.# M. Schnell, I. Broeck, and U. Sorger, ETT, Vol. 10,

No.4, pp. 417-427, Jul.-Aug. 1999.

0 M-1

・・・

1 2

f

FDMA S t M iFDMA Spectrum MappingAdvantage of localized FDMAAdvantage of localized FDMA

Multi-user diversity gain, similar to downlink OFDMA, can beobtainedAccording to each user’s channel condition, one or moreresource blocks of 1msec and 12 subcarriers (180kHz) each isallocatedallocated

Di t ib t d FDMAL li d FDMA Distributed FDMA

user useruser user

Localized FDMA

Whole bandwidth

A CB D

Whole bandwidth

Multi-user diversity Frequency diversity


(freq./time-domain scheduling)q y y

h llChallenge For 4G

For the realization of 4G systems ith 1Gb bilit th with ~1Gbps capability, there may

be 3 important technical issues to be addressedaddressed

Limited bandwidth MIMO multiplexingSevere channel Advanced equalizationSevere channel Advanced equalizationTransmit power Distributed antenna

network (DAN)


In 4G systems much higher throughput isIn 4G systems, much higher throughput isdemanded than 3G systems.

V i V i DataVoice+data Voice+Data

1GA l

2GDi i l

3GDigital

4GDigital

Big

Analog(FDMA)

Digital(TDMA)

Digital(CDMA)

Digital(OFDMA?)

leapImproved frequency utilization

NarrowbandIncreased peak rateIncreased no. of

Broadband

Increased throughputchannels


E l ti f Wi l AEvolution of Wireless AccessIn 3G, FDMA was used in 1G, TDMA in 2G, DS-CDMA.In 3G, FDMA was used in 1G, TDMA in 2G, DS CDMA.In 3.9G(LTE), OFDMA and SC-FDMA will be used fordownlink and uplink, respectively.In 4G, what wireless access technique is used?

Frequency-domainSignal processing

Time-domain signal processing

g p g

cy 6.25kHzFDMA

?4G

3.9GOFDMA，SC-FDMA

f3f2f1

requen

c FDMA

y

1G

2G

3.9G(LTE)Time

F

CDMA3G

requen

cy

# 3

TDMA2G

Single-carrier

ency

1 3 1 2 32

F # 2Spreading code#1

MH

z25kHz


Time

Freq

ue

Time

1 3 1 2 32

Ex. 20ms

5

Li it d b d idth P blLimited bandwidth ProblemITU allocated the spectrum for 4G systems in Dec. 2007.ITU allocated the spectrum for 4G systems in Dec. 2007.

450~470MHz (20MHz)790~806MHz (16MHz)2.3~2.4GMHz (100MHz)3.4G~3.6GHz for Global use (200MHz)

200MHz bandwidth in the global frequency band must be200MHz bandwidth in the global frequency band must beshared by several operators (at least 2) and reusedeverywhere.The single frequency reuse is possible with either SC orOFDM.However, probably, an effective frequency reuse factor canbe around 25% an effective bandwidth/BS is only around12 5MHz/link12.5MHz/link.1Gbps/12.5MHz/BS is equivalent to 80bps/Hz/BS!!


How To Achieve 1Gbps with Li it d B d idth?Limited Bandwidth?

The use of higher level of modulation has aThe use of higher level of modulation has alimitation

1024QAM provides only 10bps/Hz.1024QAM provides only 10bps/Hz.In addition, the achievable BER performance severelydegrades.

16QAM4QAM1024QAM


16QAM(4bps/Hz)

Q(2bps/Hz) 1024QAM

(10bps/Hz)

MIMO Multiplexing May Be A S iSavior

Independent data streams are transmitted simultaneouslyIndependent data streams are transmitted simultaneouslyfrom transmit antennas using the same carrier frequency.SDM is to increase achievable data rate within the limitedbandwidth, i.e., the channel capacity in bps/Hz.

Nt antennas Nr antennas

Coding S/P Signal]

Multipathchannel

Coding S/P Signal]detection Decod.


Ch l P blChannel ProblemMultipath channelMultipath channel

In terrestrial wireless communications, the transmitted signal isreflected or diffracted by large buildings between transmitter andreceiver creating propagation paths having different time delaysreceiver, creating propagation paths having different time delays.

Strong channel frequency-selectivityFor signal transmissions using 12.5MHz bandwidth, 1 symbol length inFor signal transmissions using 12.5MHz bandwidth, 1 symbol length intime is equivalent to the distance of 24 m. So, many distinctmultipaths exist which have time delays of longer than the transmittedsymbol length.

Large obstaclesd-4

y g

Localscatterers

Transmitter

ReceiverR fl ti /


ReceiverReflection/diffraction

The transfer function The transfer function of wireless channel is no longer constant

th i l1

10

l gai

n

over the signalbandwidth.Challenge is to

0.1Cha

nnel

Challenge is to transmit broadband data close to 1 Gbps

ith hi h lit

0.010 10 20 30 40 50 60 70 80 90 100

Frequency (MHz)with high quality over such a severe frequency-selective

10

Frequency (MHz)

nfrequency selective channel.Gigabit wireless

1

hann

el g

ain

technology of >80bps/Hz/BS is necessary for 4G

0.1Ch

L=16 Uniform power delay profilel-th path time delay=100l + [-50,50)ns

necessary for 4G.


0.010 1 2 3 4 5 6 7 8 9 10

Frequency (MHz)

T it P P blTransmit Power ProblemPeak power is in proportion to “transmission rate” x “fc2.6Peak power is in proportion to transmission rate x fc[Hata-formula]” where fc is the carrier frequency.

Assume that the required transmit power for 8kbps@2GHz is 1Watt fora communication range of 1 000ma communication range of 1,000m.The required peak transmission power for [email protected] needs to beincreased by 1Gbps/8kbps x (3.5GHz/2GHz)2.6 = 535,561 times, that is,536kW tt536kWatt.Obviously, this cannot be allowed.

To keep the 1W power, the communication range should beTo keep the 1W power, the communication range should bereduced by 43 times(i.e., 1,000m 23m). Femto cellularnetwork.

8kbps@2GHz

# M. Hata, “Empirical formula f

p @[email protected]

FA/Tohoku University 28FA/Tohoku University 28

for propagation loss in land mobile radio services”, IEEE Trans. Veh. Technol., VT-29, pp. 317-325, 1980. 2010/05/07

1000m23m

For broadband communications communicationFor broadband communications, communicationrange shrinks significantly because of thetransmit power limitation.transmit power limitation.Fundamental change is necessary in wirelessaccess networkaccess network.

Radio control station

Network Network

Base station

Base station


Advanced FDE for SC i l i iSignal Transmission

F. Adachi, Kazuki Takeda, and H. Tomeba,


“Introduction of Frequency-Domain Signal Processingto Broadband Single-Carrier Transmissions in aWireless Channel,” IEICE Trans. Commun., Vol. E92-B,No.09, pp.2789-2808, Sep. 2009.

Frequency-domain E li ti I P f lEqualization Is Powerful

Frequency-domain equalization (FDE)Frequency domain equalization (FDE)With FDE, both SC and OFDM can take advantage of thechannel frequency-selectivity and have a similar improved BERpe fo manceperformance.

Similar transmitter/receiver structure

Transmit data ta

mod.

rtio

n o

f G

I

MCc-P

oin

t IF

FT GI Nc symbols

Copy

Dat

Inse

r

SC Nc

Transmitter

Ng symbols

Received d t

Data d

Nc-Po

Rem

ovFDMCdata

dem

od.

oin

t FFT

val of G

I

DEMC

SCNc-I F


ReceiverPo

int

FFT

BER Performance I tImprovement

BER performance of SC BER performance of SC can be significantly improved with MMSE-FDE

1.0E+00MRC

FDE.However, there is still a big performance gap

1.0E-01 EGC

big performance gap from the theoretical lower bound.

1.0E-02

age B

ER

Matchedfilter boundLower bound

This is due to residual ISI after MMSE-FDE.Introduction of ISI

1.0E-03Ave

raMMSE

ZFL=16-pathuniform power

e bou d

Introduction of ISI cancellation technique can reduce the

f

1.0E-04delay profileQPSKNc=256N 32

Performanceperformance gap.

F. Adachi, Kazuki Takeda, and H. Tomeba, “Introduction of

1.0E-050 5 10 15 20

i d / (d )

Ng=32 gap


Frequency-Domain Signal Processing to Broadband Single-Carrier Transmissions in a Wireless Channel,” IEICE Trans.Commun., Vol. E92-B, No.09, pp.2789-2808, Sep. 2009.


It ti ISI C ll tiIterative ISI CancellationResidual ISI replica is generated and subtracted from theResidual ISI replica is generated and subtracted from thereceived signal.

−= )()()( ~ˆ~ iii MRR　N

c -p・)(

~ )1( kS i−

⎪⎧ = )()(

)(

ˆreplica ISI residual theis ~ where

ii

i

RWR

M Soft replica

oin

t FFT

Residual ISIMMSE

・・

・)(

)1(~ −is{ }{ }

⎪⎪

⎪⎪⎪

⎨=

−= −

)()(

)1()()()(

ˆ

~ˆ/2~

ii

iiiss

i ATE

HWH

sFIHM　　

FFT

IFFT

Residual ISIreplica

MMSEweight

・・)()( kW i )()( kM i

s

h

⎪⎪⎪

⎩ = ∑ −

=

10 )(ˆ)/1( cN

kc kHNA -GI

Nc-

poin

t

Nc-

poin

t I

ReceivedSignal block

・・

・

・・

・)(kR )(ˆ )( kR i )(~ )( kR i

-+

MMSE weight# Kazuaki Takeda and F. Adachi,

“Throughput of multicode DS-CDMA HARQ using MMSE turbo equalization” bygivenis~orerror vecttheofelementeachof

error squared average theminimizes which weight,MMSE The)()()( A iii −= FsRE

N N

HARQ using MMSE turbo equalization IEICE Technical report, RCS2006-167, pp.59-64, Nov. 2006.

# K. Ishihara, K. Takeda, and F. Adachi, “Frequency-domain Multi-stage Soft Interference Cancellation [ ]

)/(|)(|)()(

bygiven is,or error vect theofelement each of

2)1()1(

10

2)1(

*)(

NEkHkHkW

A

iis

ii

−− +ρ=

=

　

FsRE


stage Soft Interference Cancellation for DS-CDMA Uplink Signal Transmission,” IEICE Trans. Commun., Vol.E90-B, No.5, pp. 1152-1161, May 2007.

[ ].estimatesoft its andblock signal ed transmittebetween therror squaredaveragetheis|)(~)(|where 2)1()1( tstsE ii −− −=ρ

MMSE-FDE/w residual MMSE FDE/w residual ISI cancellation can improve the BER

f

100MMSE-FDE

performance.But, the performance improvement is smaller

10−1 MF bound

Rimprovement is smaller for a higher multilevel modulation [Takeda].

10−2

age

BER

QPSK

64QAM

Performance gap from MF bound

QPSK: 2dB

10−3

Aver

Q

16QAMQPSK: 2dB16QAM: 5dB64QAM: 12dB

10−4Nc=64N =16

Performancegap

0 5 10 15 20 25 3010−5

A i d E /N (dB)

Ng 16L=16-path

g p

34 34

Average received Eb/N0(dB)

2010/05/07 FA/Tohoku University

K. Takeda, et. al., IEICE Trans. Commun., Vol. E89-B, No. 12,pp. 3335-3343, Dec. 2006.

Frequency-domain Block Si l D t tiSignal Detection

BER performance of the broadband single-carrier signalBER performance of the broadband single carrier signaltransmissions significantly degrades due to the stronginter-symbol interference (ISI).Frequency-domain block signal detection which combinesfrequency-domain equalization (FDE) and maximumlikelihood detection (MLD) is very promisinglikelihood detection (MLD) is very promising.

Nc-symbol transmit block( ) NdHFY +sE2

timed(0) d(2) d(Nc−1)···

( ) NdHFY +=s

s

T

y YFrequency-

domain block i l−G

I

oint

FFT

Dat

aod

ulat

ion

Received dataData

Dat

adu

latio

n

d +GI

Frequency-selective

channel H signal detection

−

Nc-p

o Dde

-mo dataD

mod

+ channel H


T. Yamamoto, K. Takeda, and F. Adachi, “A Study of Frequency-Domain Signal Detection forSingle-Carrier Transmission,” Proc. IEEE VTC 2009 Fall, 20-23 Sept, 2009, Araska, US.

SIC & MMSEDSIC & MMSEDI t f MMSE

Decision resultW i h Interference

cancellationMMSE

detection

Replica

Decision resultWeight

computationY

Iteration stageInitial stage

Replica generation

......g

0th layer0th layer no cancellation cancellation

1th layer1th layer

d(0) d(1) d(2) ・・・ d(Nc-1) d(0) d(1) d(2) ・・・ d(Nc-1)

cancellationno cancellation

......cancellation

d(0) d(1) d(2) ・・・ d(Nc-1) d(0) d(1) d(2) ・・・ d(Nc-1)

cancellation

...

Nc-1th layer

...

Nc-1th layer cancellation cancellation

10

......

d(0) d(1) d(2) ・・・ d(Nc-1) d(0) d(1) d(2) ・・・ d(Nc-1)


QRM MLDQRM-MLDQR decomposition is applied to Y to transform detect theQR decomposition is applied to Y to transform detect thesymbols in decreasing order of reliability using MLD.

Y Decision QRHF = YQY H=ˆ

Y QR decomposition

Multiplication of QH

MLD based on M-algorithm

Decision result

NQRdYQY HsH E+

2ˆ NQRdYQY

N

s

s

dd

RRRRR

EYY

T

c

⎥⎥⎤

⎢⎢⎡

⎥⎥⎤

⎢⎢⎡

⎥⎥⎤

⎢⎢⎡

+==

−

)1()0(

2)1(ˆ)0(ˆ 1,01,00,0 L

NQ

0

H

cNN

N

s

s

c Nd

d

R

RRTE

NY

Y

cc

c +

⎥⎥⎥⎥

⎦⎢⎢⎢⎢

⎣ −⎥⎥⎥⎥

⎦⎢⎢⎢⎢

⎣

=

⎥⎥⎥⎥

⎦⎢⎢⎢⎢

⎣ − −−

−

)1(

)1(2

)1(ˆ

)1(

1,1

1,11,1

MMO

L

M

MLD−

∈= 1 )(minargˆ

cNc NX

L ddd

∑ ∑−

′ ′−−−−−=−=1 22

)1(2)1(ˆ2ˆ)(

and level modulation thedenotes where

cN nss nNdREnNYEL

X

RdYd

2010/05/07 FA/Tohoku University 37．

∑ ∑= =′

′−−−−− ==0 0

1,11 )1()1( )(ccc

n ncnNnN

sc

sN nNdR

TnNY

TL RdYd

As the number of QPSKAs the number of iterations increases, the BER performance i d h

1.0E-01Iterative SIC&MMSED

i=1i=0i 2

QPSK

improves and approaches that of the lower bound.Much better performance

1.0E-02QRM-MLD

M=16 M=64M=256

i=2

Much better performance can be achieved by using than iterative 1.0E-03

rage

BER MMSE-FDE

Theoretical SIC&MMSED.

1 0E 04Av

er lower bound

QPSK

[Iterative SIC&MMSED]T. Yamamoto, K. Takeda, and F. Adachi, “A Study of Frequency-Domain Si l D t ti f Si l C i T i i ”

1.0E-04 QPSKNc=64Ng=16L 16 h ifSignal Detection for Single-Carrier Transmission,”

Proc. IEEE VTC 2009 Fall, 20-23 Sept, 2009, Araska, USA.[QRM-MLD]T. Yamamoto, Kazuki Takeda, and F. Adachi, "Single-carrier transmission using QRM-


1.0E-050 5 10 15 20

L=16-path uniform


dac , S g e ca e t a s ss o us g QMLD with antenna diversity," Proc. The 12th International Symposium on Wireless Personal Multimedia Communications (WPMC2009), Sendai, Japan, 7-10 Sep. 2009.

Frequency-domain Filtering and Joint q y gMMSE-FDE & Spectrum Combining

Frequency-domain Frequency domain filtering is a partial spreading of the transmit i l i th f

Transmit

mod.

n o

f G

I

oin

t T uen

cm

ain

er Poin

t FTsignal in the frequency

domain.Frequency domain filtering

data

Dat

a m

Inse

rtio

Nc-P FF

T

Freq

uy-

dom

Filte

2N

c-P

IFF

Frequency domain filtering increases the number of frequency components from Nc to (1+α)Nc.

Transmitter

N fude

of

ectru

m

c ( ) c

Lower PAPR is achieved at the price of wider i l b d idth

Nc frequency components

NN /2−N /2−N 0A

mpl

itusi

gnal

spsignal bandwidth.Larger frequency-diversity gain can be

Filtering

(1+α)N frequency

NcNc/2−Nc/2−Nc 0e

of

trum

diversity gain can be obtained through joint MMSE-FDE & spectrum

(1+α)Nc frequency components

Am

plitu

deig

nal s

pect

combining.


NcNc/2−Nc/2−Nc 0Frequency index k

s

iReceiver StructureDouble sampling and transformation of the received signalDouble sampling and transformation of the received signalinto the frequency-domain signal having (1+α)Nc frequencycomponents by 2Nc–point FFT.Joint MMSE-FDE & spectrum combining to recover theoriginal Nc frequency components for transforming back toa time domain signal by N –point IFFTa time domain signal by Nc point IFFT.

2Nc Nc2Ncnt

FFT

nt IF

FT

ta ulat

ion

Receivedal o

f GI

・tr

um inin

g

・

ss T

Tit Δ+⋅=

2W(0) ・

2Nc-p

oin

Nc-p

oin

Da

dem

odu

data

Rem

ova ・

・Sp

ect

com

bi

・・

・・

W(2Nc−1)Double-ratesampling

T. Obara, K. Takeda, and F. Adachi, "Joint Frequency-domain Equalization & Spectrum Combining for The Reception of SC Signals


Joint MMSE-FDE & spectrum combiningThe Reception of SC Signals in the Presence of Timing Offset," Proc. IEEE VTC2010-Spring, Taipei, Taiwan, 16–19 May 2010.

1.E-01QPSKN 256 N 32

100QPSK

1.E-02

Nc=256, Ng=32L=32-path uniform

10-1

0

1 E-03ge B

ER

10 2

OFDMα=0

>PA

PR0)

1.E 03

Aver

ag

□ α=0◇

10-2

α=0.25

Pr(P

APR

>

1.E-04 ◇ 0.25△ 0.5○ 0.75× 1

10-3α=0.5

0 75α=1

P

1.E-050 5 10 15 20

i d / (d )

× 110-4

102 4 6 8

α=0.75


Average received Eb/N0 (dB) PAPR0 (dB)

R b t A i t Ti i Off tRobust Against Timing OffsetJoint MMSE-FDE & spectrum combining is robust againstJoint MMSE FDE & spectrum combining is robust againstthe receive timing offset.

MMSE weight removes the phase rotation produced by timing offset.BER f i l i i i h i i ffBER performance is almost insensitive to the timing offset.

α=0.51.E-01

QPSK1.E-01

QPSK

α=1

1.E-02

QPSKNc = 256Ng = 32L=32-path uniformα=0.5 1.E-02

QPSKNc = 256Ng = 32L=32-path uniformα=1

Symbol rate MMSE-FDESymbol rate

MMSE-FDE1 E 03ge

BER

1 E-03ge B

ER

Joint Joint MMSE-FDE & spectrum combining

1.E-03

Aver

ag 1.E-03

Aver

ag MMSE-FDE & spectrum combining

combining1.E-04

Δ=0Δ∈[−0.5, 0.5]

Freq. diversity gain

1.E-04

Δ=0Δ∈[−0.5, 0.5]

Freq. diversity gain

42

1.E-055 10 15 20


g1.E-05

5 10 15 20

Average received Eb/N0 (dB)2010/05/07 FA/Tohoku University

O l FDEOverlap FDEThe insertion of GI (CP) for FDE reduces the throughput by( ) g p ya factor of 1/(1+Ng/Nc).

DataGI

Copy

f

Nc symbolsNg symbols

Without GI insertion, the inter-block interference (IBI) isproduced.

FDE output without GI insertionFDE output without GI insertion

NoiseIBIresidualISIresidual)()()(12)(ˆ1

+++⎟⎟⎞

⎜⎜⎛

= ∑−

tskHkWEtscN

s NoiseIBIresidualISIresidual)()()()(0

+++⎟⎟⎠

⎜⎜⎝

= ∑=

tskHkWNT

tskcc *Kazuki Takeda, H. Tomeba, K. Takeda, and F.

Adachi, “DS-CDMA HARQ with Overlap FDE,” IEICETrans. Commun., Vol. E90-B, No.11, pp.3189-3169,Nov 2007


Average equivalent channel gainNov. 2007.

*K. Takeda, H. Tomeba, and F. Adachi, “IterativeOverlap FDE for DS-CDMA without GI,” Proc. 2006IEEE 64th Vehicular Technology Conference (VTC),Montreal, Quebec, Canada, 25-28 Sept. 2006.

0 5

Impulse response of 0.4

0.5

fter F

DE MMSE-FDE

N c =256L =16Impulse response of

circular FDE filter concentrates at the i i it f t 0

0.2

0.3

espo

nse

aft L =16E b /N 0=10dB

vicinity of t=0.This means that the residual IBI after FDE is localized

0

0.1

Inpu

lse r

only at the both ends of FFT block.This property can be

0-128 -64 0 64 128

tp p yexploited to mitigate the IBI after FDE.

Overlap FDE

A partial sequence of Msymbols is picked up

Overlap FDE

FFT bl k

time

FFT block

FFT blockFFT block

*Kazuki Takeda, H. Tomeba, K. Takeda, and F.Adachi, “DS-CDMA HARQ with Overlap FDE,” IEICETrans. Commun., Vol. E90-B, No.11, pp.3189-3169,N 2007


FFT blockNov. 2007.*K. Takeda, H. Tomeba, and F. Adachi, “IterativeOverlap FDE for DS-CDMA without GI,” Proc. 2006IEEE 64th Vehicular Technology Conference (VTC),Montreal, Quebec, Canada, 25-28 Sept. 2006.

If M≤128 is used, the 1.E+00

QPSKN c =256SF =U =16

Without GIWith GI (N g =32)

If M≤128 is used, the residual IBI can be minimized and the BER f 1.E-01

R

L =16, α=0 dBMMSE-FDE

BER performance close to MMSE-FDE with CP insertion can

1.E-02

vera

ge B

E

Lowerbound

with CP insertion can be achieved.

1.E-03Av

M =64128

192

+

1.E-04 224 240 256

×FFT block window

1.E-050 5 10 15 20

Average received E b /N 0 (dB)

M chips

0 Nc-1


0 Nc 1

Joint overlap FDE & ICI cancellation provides good BERJoint overlap FDE & ICI cancellation provides good BERperformance close to the lower-bound.

1.E-01QPSK

1.E-01QPSK

1.E-02

N c =256, M =160L =16

SF =U =161.E-02

QPSKN c =256, M =160

L =16SF =1

e B

ER LowerOverlap FDEonlye

BER Lower Overlap FDE

1.E-03

Ave

rage bound

y

Iterativej i lNumber of iteration

1.E-03

Ave

rage bound only

Number of iteration1.E-04

joint overlap FDE& ICI cancellationi =1

2 3

Number of iteration1.E-04

Iterativejoint overlap FDE& ICI cancellation

i =1 2 3

Number of iteration

1.E-050 5 10 15 20

41.E-05

0 5 10 15 20

4


Average received E b /N 0 (dB)Average received E b /N 0 (dB)

(a) SF=U=1 (b) SF=U=16

MIMO M lti l iMIMO MultiplexingNext generation (4G) wireless systems areNext generation (4G) wireless systems areexpected to provide broadband packet dataservices of up to 1Gbps. However, availablep p ,bandwidth is limited.

In December 2007, ITU allocated 3.4~3.6GHz band for,4G services. Only 200MHz is available for global use.This must be shared by at least 2 operators and by the

/d li k Alth h ll f 100MH iup/down links. Although one-cell reuse of 100MHz ispossible, but, effective bandwidth which can be used ateach BS is only around 12.5MHz/link. 1Gbps/12.5MHz iseach BS is only around 12.5MHz/link. 1Gbps/12.5MHz isequivalent to 80bps/Hz/BS!!

Thus, the development of a highly spectrum, p g y pefficient wireless transmission technology of>80bps/Hz/BS is demanded.p / /


Throughput of SC MIMO M lti l i SC MIMO Multiplexing

MIMO signal detection 8MIMO signal detection using FDE and FDIC provides higher throughput th OFDM

7

8

SC w/ OFDMthan OFDM.

Start

6

z)

FDIC

SC

OFDMw/ FDIC

FDIC

Start

MMSE FDE Weight comp.

4

5

ut (

bit

/s/H

z w/o FDIC

FDIC

Replica gene.LLR comp.3

4

hro

ugh

pu

OFDM w/o Output

# A. Nakajima, D. Garg and F. Adachi, “Frequency-

2T

h

SC (4, 4)MIMO SDM with iterative FDIC

FDIC

domain iterative parallel interference cancellation formulticode DS-CDMA-MIMO multiplexing,” Proc. IEEEVTC’05 Fall, Vol.1, pp. 73-77, Dallas, U.S.A., 26-28Sept. 2005.

# A Nakajima and F Adachi “Iterative FDIC using 2D 0

1(i=4)HARQ type-II S-P2QPSK, Nc=256, Ng=32L=16-path uniform power delay profile


# A. Nakajima and F. Adachi, “Iterative FDIC using 2D-MMSE FDE for turbo-coded HARQ in SC-MIMOmultiplexing,” IEICE Trans. Commun. Vol. E90-B, No.3,pp.693-695, Mar. 2007.

0-5 0 5 10 15 20 25

Average received Es/N0 per receive antenna (dB)

L 16 path uniform power delay profile

Throughput of S d MIMO M lti l i

8

Spread MIMO MultiplexingSpread MIMO SDM w/FDIC 8

7

8MC-CDMA (4,4)SDM with iterative FDIC, QPSK,SF (=U )=256, N c=256, N g =32, L=16, S-P2, i=4

C S

Spread MIMO SDM w/FDIC provides the throughput superior to non-spread SC. 7

8

SC w/ OFDM

6OFDM

MC, DS

w/ FDIC

Much better throughput than OFDM in a high Es/N0 region.Almost the same throughput as

6

z)

FDIC

SC

OFDMw/ FDIC

4

5

ut (b

ps/H

z) MC, DS

w/o FDIC

OFDM in a low Es/N0 region.Start

2D-MMSE FDE Weight comp 4

5

ut (

bit

/s/H

z w/o FDIC

3

4

Thro

ughp

u

OFDMFDIC

2D MMSE FDE

Multicode Multicode

Weight comp.

3

4

hro

ugh

pu

OFDM w/o

Single transmit antenna limit2Replica gene.LLR comp.

despreading spreading

2T

h

SC (4, 4)MIMO SDM with iterative FDIC (i=4)

FDIC

0

1 MC DSw/ FDICw/o FDIC

EndA. Nakajima, D. Garg and F. Adachi, “Frequency-domainiterative parallel interference cancellation for multicode DS-CDMA-MIMO multiplexing,” Proc. IEEE VTC’05 Fall, Vol.1, pp. 73-0

1HARQ type-II S-P2QPSK, Nc=256, Ng=32L=16-path uniform power delay profile

0-5 0 5 10 15 20 25 30

Average received E s /N 0 per antenna (dB)2010/05/07 FA/Tohoku University 49

p g, , , pp77, Dallas, U.S.A., 26-28 Sept. 2005.A. Nakajima and F. Adachi, “Iterative FDIC using 2D-MMSE FDEfor turbo-coded HARQ in SC-MIMO multiplexing,” IEICE Trans.Commun. Vol. E90-B, No.3, pp.693-695, Mar. 2007.

0-5 0 5 10 15 20 25

Average received Es/N0 per receive antenna (dB)

Increasing the no 80Increasing the no. of antennas can improve the

70

80

8

NxN MIMO (w/receive diversity)

improve the spectrum efficiency or can decrease the 50

60

6

7

8

o a d arequired transmit power.

40

C(b

ps/H

z)

5

4

6

5

pHowever, too many antennas are 20

30C 4

3

2antennas are required at both transmitter and

10

2

N=1

receiver! 0

0 10 20 30Average total received Es/N0 per receive antenna (dB)


G. J. Foschini and M. J. Gans, “On limits of wireless communicationsin a fading environment when using multiple antennas,” WirelessPersonal Commun., Vol.6, No. 3, pp.311-335, Mar. 1998.

Space for MIMO Antennas I Li it d !Is Limited !

How to implement many antennas in a handHow to implement many antennas in a handportable unit?Wearable antenna on your head?Wearable antenna on your head?

Wearable antenna

No space in a small hand small hand portable unit


MIMO Cannot Solve Power P blProblem

Peak power is in proportion to “transmission rate” x “fc2.6Peak power is in proportion to transmission rate x fc[Hata-formula]” where fc is the carrier frequency.Links for broadband data services will be severely power-limited.Let’s consider the peak transmit power for [email protected] a communication range of 1 000m We assume theat a communication range of 1,000m. We assume therequired transmit power for 8kbps@2GHz is 1Watt.The required peak transmission power increases byThe required peak transmission power increases by1Gbps/8kbps x (3.5GHz/2GHz)2.6 = 535,561 times, that is536kWatt. Obviously, this cannot be allowed.

FA/Tohoku University 52FA/Tohoku University 52

M. Hata, “Empirical formula for propagation loss in land mobile radio services”, IEEE Trans. Veh. Technol., VT-29, pp. 317-325, 1980.

2010/05/07

Distributed Antenna k ( )Network (DAN)

Another important technical issue for therealization of high data rate 4G networks isrealization of high data rate 4G networks isthe significant reduction of the transmit powerfrom a mobile terminal (MT).This can be achieved by introducing thedistributed antenna concept.


Distributed Antenna Network (DAN)(DAN)

Many antennas are spatially distributed around each BSMany antennas are spatially distributed around each BSwhich is a gateway to the network

With a high probability, some antennas close to an MT can always bevisiblevisible.Antennas are connected with a BS by a means of optical fiber orwireless links.

Many antennas cooperate and act as Distributed MIMOmultiplexing, diversity, or relay.

The problems can be mitigated which result from distance-dependentThe problems can be mitigated which result from distance-dependentpath loss and shadowing loss as well as the instantaneous signalpower variations due to the multi-path fading.

Optical fiber cable

BS

Di t ib t d t k

Distributed wirelessport

Distributed MIMO

multiplexing/diversity

Distributed MIMO relay


Distributed networkantenna

Transmit Diversity for SC-DAN D li k Downlink

The distributed MIMO 1 0E+00The distributed MIMO diversity increases significantly the channel

it

1.0E+00α=3.5, σ=7.0

Es/N0=10dBL=16-path uniform

capacity.The use of only around 5 antennas near a user provides a

1.0E-01

scis

sa]

Νt=1

MRT diversity

sufficient improvement.

Transmit power can be reduced significantly 1 0E 02ro

b[C

<abs

Νt=5∼10Νt=2

Ν 3reduced significantly. 1.0E-02Pr Νt=3

Νt=4

tion

[%]

10(0,0) (1,0)

Receiver x

y

BS1.0E-03

0 1 2 3 4 5 6 7 8 9 10age

pow

er d

istri

but

1

(1,1)(0,1)

Antenna

MT

# H. Matsuda, H. Tomeba, and F. Adachi,“Channel capacity of distributed antenna systemusing maximal ratio transmission ” The 5th

0 1 2 3 4 5 6 7 8 9 10Channel capacity C (bit/s/Hz)Av

era

0.1


Distributed Antenna Network

MT using maximal ratio transmission, The 5thIEEE VTS Asia Pacific Wireless CommunicationsSymposium (APWCS2008), Tohoku University,21~22 Aug., 2008.

1.0E+00 2D-WF1

2D water filling weight

α = 3.5 σ = 7.0

MRT2D water filling weight

bygivenweightWF2Dtheusing maximized iscapacity downlink The

σ 7.0TransmitEs/N0 = 10 dBL = 16is

sa]( ) ( )

Nt

tknHknW

t

=−1

2

* ,,

bygiven weight WF2D theusing

1.0E-01Nt = 1

2

0.1

C<a

bsci( )

nt knH

t

⎫⎧ ⎞⎛

∑=0

2,

2

310

Prob

[C

Ns

NE

t ⎪

⎪⎪

⎬

⎫

⎪

⎪⎪

⎨

⎧

⎟⎟⎟⎟⎞

⎜⎜⎜⎜⎛

⎟⎟⎠

⎞⎜⎜⎝

⎛−ϕ× −

−

1

1

2D 0 ,1max

510

0.01

( )N

nt knH

N t

t⎪⎪

⎭⎪⎪

⎩⎟⎟⎟

⎠⎜⎜⎜

⎝

⎟⎠

⎜⎝ ∑

=

1

0

20

t i tt itd th

,

1.0E-020 1 2 3 4 5 6 7 8 9 10

C (bps/Hz)

0.01

c

N N

t NknWc t

=∑ ∑− −1 1

2),(

constraintpower transmit under the

C (bps/Hz)


k nt= =0 0H. Matsuda, K. Takeda, and F. Adachi, “Downlink Transmit Diversity For Broadband Single-carrier Distributed Antenna Network,” to be presented at IEEE VTC 2010 Spring, Taipei, May 2010.

Di t ib t d B f iDistributed BeamformingMultiple beams from different distributed antenna pointsMultiple beams from different distributed antenna pointsserve a user to increase the signal power and reduce thecochannel interference.

Directional beam

DANProcessing

Omuniantenna

Processingcenter

57Distributed antenna point(a group of antennas)


Multi-hop Virtual Cellular N t k (VCN)Network (VCN)

Virtual cellular network (VCN) is suitable for non-real timeVirtual cellular network (VCN) is suitable for non real timepacket communication.Virtual cell consisting of many distributed wireless ports

One port (central port) acts a gateway to the network.Mobile terminal and central port are connected using wirelessmulti hop relay techniquemulti-hop relay technique.

DistributedNetworkNetwork

Network control station

Distributedport

Base station

Centralport(b) VCN (a) Conventional CN


p(b) VCN (a) Conventional CN

E. Kudoh and F. Adachi, “Power and Frequency EfficientWireless Multi-hop Virtual Cellular Concept,” IEICE Trans.Commun., Vol.E88-B, No.4, pp.1613-1621, Apr. 2005.

An introduction of 2-hop relay may be a goodAn introduction of 2 hop relay may be a goodsolution at the beginning.

relay Single-hoprelay Single hop

Terminal

Base station


S C l di R kSome Concluding RemarksNext generation wireless networks will require Giga-bitNext generation wireless networks will require Giga bitwireless technology of ~1Gbps and >80bps/Hz/BS undersevere co-channel interference.Wireless Signal Processing

Frequency-domain equalization & MIMO may be indispensibletechniques But still insufficient!techniques. But, still insufficient!

Reducing transmit powerDistributed antenna network (DAN) with multiplexing, diversityst buted a te a et o ( ) t u t p e g, d e s tyor relay can solve the transmit power problem while increasingthe spectrum efficiency.Other promising solutions?Other promising solutions?

Lots of interesting and important research topics remainbefore the born of next generation wireless systems.before the born of next generation wireless systems.


Please Visit Our f fHomepage for More Info.

http: // bil i t h k j//www.mobile.ecei.tohoku.ac.jp


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