RoF (Radio over Fiber) is a technique to transmit analog radio frequency signal as optical intensity modulation using optical fibers which have low-loss and broadband property.・Centralized operation of several small-cell base stations. → reduction of maintenance cost, easily construct heterogeneous radio network, cooperative distributed antenna system, and large transmission capacity.

Radio over Fiber (RoF) TechnologyNetwork Systems Laboratory, Graduate School of Information Science,

Nara Institute of Science and Technology (NAIST)

Background

RoOOOK (Radio over Optical OOK）RoFisa(rac+vebutdedicatedop+calsourcesandfibersareneeded.RadiooverOp+calOn-OffKeying(RoOOOK)transfersop+calbaseband(BB)signalandradiofrequency(RF)signaloversingleop+calfiberchannel.

network

BaseSta+on(LTE)

BaseSta+on(WiFi)

BaseSta+on

BaseSta+on

LTE

LTE

network

ControlSta+on

E/OO/E

E/OO/E

E/OO/E

E/OO/E

Fiberwirelessintegra+on

LTE

WiMAX

WiFi

LTE

LTE

Externalre-modula+onofop+calOOKsignal

ForIn-buildingnetwork

EVMvsRFpowertoEOM(π/4shiUQPSK)

OOKspectrumoverlapswithRFsignalspectrum

〒630-0192　奈良県生駒市高山町8916-5　奈良先端科学技術大学院大学　情報科学研究科　ネットワークシステム学研究室GraduateSchoolofInforma+onScience,NaraIns+tuteofScienceandTechnology8916-5Takayama,Ikoma,Nara,630-0192JAPAN

Sharingsingleop+calfiberlink

Optical OOK bit series

Transfer Curve of External optical modulator RF signal

Modulated signal

Bias point

B

m B

Optical OOK bit sequence, p(t)

RF signal, sr(t)

Optical intensity

Bp(t)+mBp(t)sr(t)

OOKinterfereswithRFsignal 1 5 1 0 5 0 5 1 0 1 50

5

1 0

1 5

2 0

2 5

3 0th e o rye x p e rim e n t

Dynami crangeofthesystem(12dB )

Critical pointofstable Ether netlink

Requir edEV M

EVM

forR

F[%

]

In c id e n tR F p ow e r to E O M [d B m ]

Experimentusing10GbpsEthernetand1.9GHzRF

BFP640

R36

C

220n

C

220n

Vcc

3.0

C

220n

R20k

V_bias

L180n

D

HSMS2820R10

RF_in

RF_out

RF in

Vcc Vbias

RF out

RadiooverOp+calOn-OffKeyingRoOOOK

Measuredspectrum:(leU)ordinaryRoF,(right)RoOOOK

Conven+onalFemto-cellbasesta+ons

Centralized control and resource sharing

Op+calswitchworkingwithload-balancingalgorithmAsshowninthefigure,abasebandunit(BBU)andremoteradiounit(RAU)isnolongerpointtopointconnec+on.Op+calswitchenablesusbeneficialfeature,notonlyreduc+onforthenumberofBBUequipmentitself,butalsoaflexibleresourcesharingandreduc+onforthenumberofhandoverprocess.

100

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1200

2 4 6 8 10 12

Tota

l thr

ough

put (

Mbp

s)

Number of BBUs, M

Round robinSorted-Round robin

GreedySorted-GreedyIn-buildingCentral office (CO)

BBU-1

.

.

.

RAU-1RAU-2RAU-3RAU-4

RAU-N

!

!

!

!

I/F

Optical switch

M < N

BBU-2BBU-3

BBU-M I/F

I/F

I/F

I/F

I/F

I/F

I/F

I/F

!

!

!

!

!

Opticalfiber

ControlM

10

15

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45

2 4 6 8 10 12

Stan

dard

dev

iatio

n (M

bps)

Number of BBUs, M

Round robinSorted-Round robin

GreedySorted-GreedyConclusion

Weevaluatethethroughputperformanceanddevia+onamongBBU’susage.Astheloadbalancingalgorithms,RoundrobinandGreedytype,andtheirmodifiedoneareassumed.TheSorted-GreedyalgorithmcanreducethenumberofBBUsby33%.TheSorted-GreedycanachieveminimumSD.ItisfoundthattheofferedloadwithhigherthroughoutshouldbeassignedtoBBUinpriortotheloadwithlowerrequiredthroughout.

Interferencesuppressionusingbiasedhalf-waverec+fica+on(BHWR)

Principleofopera+onin+medomain

Circuitdiagram

SpectrumaUerthroughBHWRcircuit

14dB

Gap-filler for High Definition Mobile Broadcasting

RadiooverFiber(RoF)basedgap-filler

RadiooverFiber(RoF)isemployedtocompensateradiodeadzonesuchasundergroundcityandinsidetunnelarea.Thesignaltransmi(edbyusingRoFissuffereddistor+oncausedbyop+calmodulator.Inthisresearch,weevaluatestheperformanceofanop+calrepeatersystemusingradiooverfiberfornextgenera+onDTTBsystememployinghigher-orderdigitalmodula+onbyusingcomputersimula+on.

(a)

(b)

Frequencyspectrumat(b)witIMD(leU)withIMD(right)

Simula+onmodel

MERvsReceivedPowerat(a)

MERat(b)dropsbyIMD