Radio-over-Fiber Technology for Wireless Communication

Services

Oct. 13, 2005

Hoon KimSamsung Electronicshoonkim@ieee.org

OutlineOutline

1. Introduction

2. Current Technologies

Analog transmission over fiber

Digital transmission over fiber

Analog transmission over HFC

3. Emerging technologies

4. Conclusion

Frequencies for Broadband RadioFrequencies for Broadband Radio0.8 GHz Cellular, 2G systems1.8 GHz 2G systems2 GHz UMTS/3G systems2.4 GHz Wireless LANs (IEEE 802.11b/g)2.6 GHz S-DMB3.4 GHz 4G systems (TBD)5 GHz Wireless LANs (IEEE 802.11a)18/19 GHz Indoor wireless LANs28 GHz Fixed wireless access (LMDS)38 GHz Fixed wireless access, Pico cellular58 GHz Indoor wireless LANs62-66 GHz Mobile

Optical FiberOptical Fiber--Based Wireless Based Wireless Communication SystemsCommunication Systems

AdvantagesModulation format transparent

Compact and reliable

Centralized control of electronic circuitry

Able to transport long distance with high fidelity

DisadvantagesNeeds optical fibers

High cost on uplink transmitters

BTS

BTS: Base transceiver station

1. Analog transmission over fiberSCM technology (IF over fiber or RF over fiber)

2. Digital transmission over fiberAnalog-to-Digital/Digital-to-Analog conversion

3. Analog transmission over HFC networkSCM technology

ApproachesApproaches

Major ApplicationsMajor Applications

1. Elimination of the ‘dead-zone’

Repeater based on optical transport systems

2. Remote antenna

Fiber-To-The-Antenna (FTTA) systems

3. Capacity enhancement

Microcell, picocell systems

Optical Links for Optical Links for ‘‘DeadDead--ZonesZones’’

BTS

Tunnel

Secluded placesMan-made obstacles

Mountainous area

fiber

FTTA (FiberFTTA (Fiber--ToTo--TheThe--Antenna)Antenna)

AdvantagesLow loss

Small size

Light weight

Immune to lightening strikes and electrical discharge

Future-proof: protocol and bit-rate transparent

Cable diameter 1/2 ″ 7/8 ″ 1+5/8 ″

Loss (/100 m) 10.6 dB 5.9 dB 3.7 dB

Coaxial cable loss (@1.8 GHz)

Picture source: Erricson

MacrocellularMacrocellular SystemsSystems

BTS: Base transceiver station

BSC: Base station controller

MSC: Mobile switching center

Antenna tower

BTS

MacrocellT1/E1

BSC

Macrocell

T1/E1

MSC

BTSLocal

ExchangeCarrier

Radius: 1~3 km

BTS SiteBTS Site

Base Transceiver StationBase Transceiver Station

DUC: Digital Up-Converter DDC: Digital Down-Converter

PA: Power Amplifier LNA: Low-Noise Amplifier

BSC: Base Station Controller

ModemT1/E1

DUC PA

DDC LNA

Duplexer/DiplexerB

SC

I

I

Q

Q

UpConv.

DownConv.

Cell Size Should be SmallerCell Size Should be Smaller

Increased carrier Increased carrier frequency suffers frequency suffers from more from more propagation losspropagation loss

Higher capacity is Higher capacity is requiredrequired

Battery consumption Battery consumption is always a critical is always a critical issueissue

Small Cell

Increased concern Increased concern about the effects of about the effects of

electroelectro--magnetic magnetic wave on human bodywave on human body

Microcellular SystemsMicrocellular Systems

conventional cell(radius : 1- 2 km)

RBS

RBS

RBS

E/ORBS

O/ERBS

RBS

RemoteBase

Station

Microcell(radius : ~ 300 m)

to exchange

Source: David Wake, Microwave Photonics Inc.

System Configuration: ExampleSystem Configuration: Example

Remote Base Station (RBS)Remote Base Station (RBS)

Major advantagesFormat transparency

Small size

Light weight

High reliability

WDM

O/E

E/O Dip

lexe

r

fiber

RBS

Basic configuration

E/O & O/EProcessor

FrequencyConverter

Duplexer& Filter

High PowerAmplifier

(15 Watt/3 FAs)

58 cm

45 c

m37 cm

PowerSupply

FoMiCellFoMiCell: Remote Base Station: Remote Base Station

OFC/IOOC, paper PD13, 1999

Application ExampleApplication Example

Sydney Olympic Games

Tekmar BriteCell™

In-building and external pico-cell

Multi-operator system (3 GSM operators)

Multi-standard radio (900/1800 MHz GSM)

>500 Remote antenna units

0.8 x 1.8 km coverage

Low RF power distributed antenna system

Dynamic allocation of network capacity

500,000 wireless calls on the opening day

Source: David Wake, Microwave Photonics Inc.

Wireless Signal Transport Using SCM Wireless Signal Transport Using SCM TechnologyTechnology

Major meritsMinimize the complexity of the RBSs • Ta-Shing Chu, AT&T, 1991

• J. Namiki, NEC, 1993

Central Base Station

Remote Base Station

PD

LDLD

PD

LD

PD

LD

PD

LD

PD

PD

LD

Controller

SCM SCM LightwaveLightwave SystemsSystems

TransmitterTransmitter FiberFiber ReceiverReceiver

Linearity of preamplifier

Thermal noise

Shot noise

LD linearity

• Spatial hole burning

• Nonlinear current leakage

• Slipping distortion

• Nonlinear coupling of gain and optical power

RIN

• Intensity noise

• Mode partition noise

• Mode hoping noise

Multipath interference

Dispersion

SBS

SPM

×Data BPF

fNLD PD

×Data BPF

f1

com

bine

r

× Data

fi

SpuriousSpurious--Free Dynamic Range Free Dynamic Range ConsiderationsConsiderations

GCNRPSFDR requiredr Δ−+Δ=

Two strong carriers

One weak carrier

ΔPr

Noise Intermod. Comp.

ΔPr: Power difference

CNRrequired : Required CNR

ΔG: Handset power control

Applications Indoor, no obstructions

Indoor/outdoor with some non-line-of sight obstructions

Outdoor, with congested

obstructions

IS-136 58~73 98~108

GSM/DCS1800 56~71 96~106

PDC 59~74 99~109

PHS 83~98 103~118

DECT 74~89 94~109

CT-2 73~88 94~108

SpuriousSpurious--Free Dynamic Range Free Dynamic Range Requirements (I)Requirements (I)

W. I. Way, Broadband hybrid fiber/coax access system technologies, 1999

Unit: dB-Hz2/3

SpuriousSpurious--Free Dynamic Range Free Dynamic Range Requirements (II)Requirements (II)

Applications SFDR requirement

GSM (900 MHz, indoor) 100

GSM (900 MHz, outdoor) 106

PCS (1900 MHz) 72-83

AMPS (900 MHz, single antenna) 91

AMPS (900 MHz, multiple antennas) 80

GSM (1~2 GHz, 3-band) 105

HiperLan (5 GHz) 94

IEEE 802.11a (5 GHz) 94

IEEE 802.11b (2.4 GHz) 94

Unit: dB-Hz2/3

A. Larsson, NEFERTITI Workshop, 2005

Current Technologies: IF over SMF/MMFCurrent Technologies: IF over SMF/MMF

Type Example Company Comments

IF over SMF/MMF

LGCell LGC Wireless Added complexity (cost) at remote unit.

Can use pre-installed fiber

BTS RF IF

Central Hub

LD PD

Remote Hub

Antenna Unit

SMF/MMF UTP

R. Penty, NEFERTITI Workshop, 2005

Current Technologies: RF over SMFCurrent Technologies: RF over SMF

Type Example Company CommentsRF over SMF

BriteCellFiberDAS

AndrewRemec

Simple remote unit but relatively expensive optics.

Uses specially installed fiber.

BTS RF

Central Hub

LD PD

Remote Hub

Antenna Unit

SMF Coax

R. Penty, NEFERTITI Workshop, 2005

Issue in Wireless Signal Transport Issue in Wireless Signal Transport Systems Using SCM TechnologySystems Using SCM Technology

1. Optical fiber should be installed

2. Mostly point-to-point architecture

3. Cost issues on upstream transmitters

Major meritsHigh performance

Use of mature digital transport technology

Compatible with multimode fiber infrastructure

Wireless Signal Transport using Digital Wireless Signal Transport using Digital Transmission TechnologyTransmission Technology

MTSO

Transmitters

Receivers Splitter Digital-RFconverter

Opticalreceiver

Combiner RF-digitalconverter

Opticaltransmitter

RF-digitalconverter

OpticalTransmitter

Digital-RFconverter

OpticalReceiver

WDM

WDM Duplexer

AnalogAnalog--toto--Digital ConverterDigital Converter

1

2

3 Quantization error

0123456789101112131415

8

9

10

Aperture jitter

SignalSignal--toto--Noise RatioNoise Ratio

B: number of bits of resolution

fs: sampling frequency

fmax: maximum frequency of the input analog signal

N: number of RF carriers

( ) ( )dBNffBSNR s

10max

10 log202

log1076.102.6 −⎟⎟⎠

⎞⎜⎜⎝

⎛++=

( ) ( )dBNB 10log206 −≈

⎟⎟⎠

⎞⎜⎜⎝

⎛=

ajitter tf

SNRmax

10 21log20

π

ta: aperture jitter of the ADC

Analog vs. Digital TransportAnalog vs. Digital Transport

Distance

Perf

orm

ance

Digital transport

Analog transport

Quantization noise-dominant

Sych loss

Current Technologies: Digital over SMF/MMFCurrent Technologies: Digital over SMF/MMF

Type Example Company CommentsDigital over SMF/MMF

Digivance ADC Added complexity (cost) at remote unit.

Mature digital technology

Can use pre-installed fiber

BTS RF IF

Central Hub

A/D PD

Remote Antenna Unit

SMF/MMFLD

Sync

D/A

1. Cost issues of A/D and D/A converters

2. Clock recovery is required at the receivers

3. Frequency converters are typically required

4. Overheads of digitized signals

Issues of Wireless Signal Transport Issues of Wireless Signal Transport Systems Using Digital Transmission Systems Using Digital Transmission

TechnologyTechnology

Wireless Signals Over HFCWireless Signals Over HFC

Major meritsUse of the existing HFC networks

Head End FibernodeFiber

Coaxial Cable Transmission Coaxial Cable Transmission Characteristics Affecting Wireless Characteristics Affecting Wireless

AccessAccess

1. Interference between existing wireline signals and

wireless signals

2. Multiple antenna noise

3. Transmission delay between any two mBSs

4. Available cable spectra (<1 GHz)

5. Funneling ingress and impulse noise

6. Multiple micro-reflections in the coaxial cable plant

Emerging Technologies: Emerging Technologies: EAMEAM--based Transceiverbased Transceiver

• D. Wake et al., Electron. Lett., 1997 • Microwave Photonics Inc.

EAM

Laser

PD

Central Site RAU

Acts as photodiode for downlink

Acts as modulator for uplink

Can operate using FDD or TDD

Can operate in passive mode

Relatively poor performance either as photodiode or modulator

Limited coverage when operating in passive mode

Emerging Technologies: WDMEmerging Technologies: WDMEfficient usage of fiber (ring, bus, double star architectures)

Can be deployed over a WDM-PON

Flexible service provision

CentralOffice

BS

BS

BS

BS

BS

BS

λ 1, λ 2, λ 3,…

λ n

λ1λ2

λn

λ1λ2

λn

CentralOffice

RN

RN

BS

BS

λn-1

λ1, λ2, λ3, … λn

RN

BSλ1 λ2

BS

λn

RN

Emerging Technologies: MMW over FiberEmerging Technologies: MMW over FiberReduced cell coverage makes this technology attractive for this application.

Enormous bandwidth of optical fiber suitable for MMW signal transport.

Dispersion-induced signal fading – SSB transmission.

• CRL, Japan

DispersionDispersion--Induced Signal FadingInduced Signal Fading

Dispersive medium

f1

λ

0 2 4 6 8Fiber Length (km)

Nor

mal

ized

Opt

ical

Pow

er

Single SideSingle Side--Band (SSB) ModulationBand (SSB) Modulation

f1

λRF signal

(f1)

90° shift

CW MZ modulator

Hilbert Transform

Intensitymodulator

RF signal(f1)

Optical filterCW

f1

λ

Optical Filtering

ConclusionsConclusions

Merging of photonic and radio technologiesMerging of photonic and radio technologies

- Fiber-radio as a last mile solution.

- Centralized control of electronic equipment is the main advantage of fiber-radio technology.

- Cost is the paramount issue for the wide deployment of this technology.

Major IssuesMajor Issues

- Cost-effective upstream transport.

- Opto-electronic interfaces.

- Integration of photonic and radio components.