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Studies on Next Generation Access Technology using Radio over Free-Space Optic Links. Kamugisha Kazaura 1 , Pham Dat 1 , Alam Shah 1 ,Toshiji Suzuki 1 , Kazuhiko Wakamori 1 , Mitsuji Matsumoto 1 , Takeshi Higashino 2 , Katsutoshi Tsukamoto 2 and Shozo Komaki 2

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Studies on Next Generation Access Technology using Radio over Free-Space Optic Links

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Studies on next generation access technology using radio over free space optic links l.jpg

Studies on Next Generation Access Technology using Radio over Free-Space Optic Links

Kamugisha Kazaura1, Pham Dat1,Alam Shah1,Toshiji Suzuki1, Kazuhiko Wakamori1, Mitsuji Matsumoto1,Takeshi Higashino2, Katsutoshi Tsukamoto2and Shozo Komaki2

1Global Information and Telecommunication Institute (GITI), Waseda University, Saitama, Japan

2Graduate School of Engineering, Osaka University, Osaka, [email protected]

17th September 2008

NGMAST 2008


Contents l.jpg

Contents

  • Introduction

  • Overview of FSO/RoFSO systems

  • Experiment setup

  • Results and analysis

  • Summary


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Global

Suburban

Urban

In-Building

Macro-Cell

Home-Cell

Micro-Cell

Pico-Cell

Personal-Cell

Introduction

Wireless communication systems

PAN, WSN …

Satellite systems …

FSO, Cellular systems, WiMAX …


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Full-opticalFSO system

Optical fiber communication

100 Gbps

FSO communication

10 Gbps

Visible light communications

MM wave communication

1 Gbps

Optical WLAN

UWB

IrDA

PAN

Data rate

100 Mbps

WiMAX

WLANa/b/g

10 Mbps

Personal areaCommunication

Long distance communication

Bluetooth

1 Mbps

ZigBee

100 Kbps

1 km

100 km

1 m

10 m

100 m

10 km

Communication distance

Introduction cont.

Wireless communication technologies and standards


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Cooperation of

fiber comm.

Wireless BB environment

1T

WDM

100G

100G-Ether

10G

SONET(trunk line)

10G-Ether standard

FSO 2.5G

(Eye safe)

FSO10G(WDM)

1G

Data rate

1G-Ethernet standard

FSO 1G

FWA 50M

(5GHz)

100M

FTTH 1G

FWA 46M

(26G)

FSO 100M

Indoor FSO (P-MP)

FTTH

10M

FWA 10M

(22&26G)

11g

Indoor FSO(P-MP)

11a

Radio on FSO

FSO 10M

12M

24M

8M

1M

IEEE802.11b

ADSL

1.5M

FWA 1.5M

(22&26G)

100K

CATV,cellular phone

Video use

Analog FSO system

ISDN

~1995

~2000

2001

2002

2003

2004

2005

~2010

Introduction cont.

FSO roadmap


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Visible light

Cosmic radiation T radiation V radiation IR radiation Communications radiation

X ray radiation Microwave, radar TV VHF SW

Frequency (Hz) 1020 1018 1016 1014 1012 1010 108 106

250 THz (1 THz) (1 GHz) (1 MHz)

(1 pm) (1 nm) (1 μm) (1 mm) (1 m) (100 m)

Wavelength (m) 10-12 10-9 10-6 10-3 100 102

λ = wavelengthf = frequency

C0 = 300 000 km/sC = λ x f

Visible light

Fiber transmissionwavelength range

0.4 0.5 0.6 0.7 0.8 0.9 1.0 1.1 1.2 1.3 1.4 1.5 1.6 μm

670 780 850 1300 1550 1625 nm

Overview of FSO/RoFSO systems

FSO is the transmission of modulated visible or infrared (IR) beams through the atmosphere to obtain broadband communications.RoFSO contains optical carriers modulated in an analogue manner by RF sub-carriers.

Merits

  • Secure wireless system not easy to intercept

  • Easy to deploy, avoid huge costs involved in laying cables

  • License free

  • Possible for communication up to several kms

  • Can transmit high data rate

    De merits

  • High dependence on weather condition (rain, snow, fog, dust particles etc)

  • Can not propagate through obstacles

  • Susceptible to atmospheric effects (atmospheric fluctuations)

Electromagnetic spectrum


Fso technology application scenarios l.jpg

Internet

Mountainous terrain

Metro network extension

RoFSO transceiver and remote BS

Backhaul(~5 km)

Areas with nofiber connectivity

RoFSO link

Optical fiber link

RF based links

RoFSO transceiver

Remote locatedsettlements

Data relay satellite

Inter-satellite link

Space station

High-speed (10Gbs) optical feeder link

Demonstration of 2.5 Gbps link

Ground stationwith adaptive optics

Fiber optic link

FSO technology application scenarios

Overview of FSO/RoFSO systems cont.

Terrestrial

  • Metro network extension

  • Last mile access

  • Enterprise connectivity

  • Fiber backup

  • Transmission of heterogeneous wireless services

    Space

  • Inter-satellite communication (cross link)

  • Satellite to ground data transmission (down link)

  • Deep space communication


Slide8 l.jpg

FSO antenna

Optical source module

Optical fiber

FSO channel

Electrical signal

O/E and E/Oconversion module

Direct coupling of free-space beam to optical fiber

FSOantenna

Optical fiber

WDM FSO channel

(b) New full-optical FSO system

Overview of FSO/RoFSO systems cont.

Conventional FSO system

  • Operate near the 800nm wavelength band

  • Uses O/E & E/O conversion

  • Data rates up to 2.5 Gbps

  • Bandwidth and power limitations

    Next generation FSO system

  • Uses 1550nm wavelength

  • Seamless connection of space and optical fiber.

  • Multi gigabit per second data rates (using optical fiber technology)

  • Compatibility with existing fiber infrastructure

  • Protocol and data rate independent

(a) Conventional FSO system


Slide9 l.jpg

Cellular

DVB

WiFi

WiMAX

Overview of FSO/RoFSO systems cont.

Free-space beam directly coupled to optical fiber

RoFSO antenna

RoF

RoF

DWDM RoFSOchannel

Heterogeneous wireless service signals

(c) Advanced DWDM RoFSO system

Advanced DWDM RoFSO system

  • Uses 1550nm wavelength

  • Transport multiple RF signals using DWDM FSO channels

  • Realize heterogeneous wireless services e.g. WLAN, Cellular, terrestrial digital TV broadcasting etc


Challenges in design of fso systems l.jpg

Beam divergence, θ

FSO antenna

FSO antenna

Transmitter

Receiver

Transmitter

Receiver

wide beam

narrow beam

Challenges in design of FSO systems

Overview of FSO/RoFSO systems cont.

Wide beam FSO systems

  • Beam divergence in terms of several milliradians

  • Easy to align and maintain tracking

  • Less power at the receiver (the wider the beam the less power)

Narrow beam FSO systems

  • Beam divergence in terms of several tens of microradians

  • Difficult to align and maintain tracking

  • More optical power delivered at the receiver

The narrow transmission of FSO beam of makes alignment of FSO communication terminals difficult than wider RF systems.


Slide11 l.jpg

Overview of FSO/RoFSO systems cont.

FSO system performance related parameters

Optical powerWavelengthTransmission bandwidthDivergence angleOptical lossesBERReceive lens diameter & FOV

Internal parameters(design of FSO system)

FSO Performance

VisibilityAtmospheric attenuationScintillationDeployment distancePointing loss

External parameters(non-system specific parameters)


Slide12 l.jpg

Clear day

Visibility > 20km

Attenuation: 0.06 ~ 0.19 db/km

Cloudy day

Visibility: ~ 5.36 km

Attenuation: 2.58 db/km

Rain event

Visibility: ~ 1.09 km

Attenuation: 12.65 db/km

Overview of FSO/RoFSO systems cont.

Factors influencing performance of FSO systems

Visibility under different weather conditions

Visibility greatly influences the performance of FSO systems e.g. fog, rain, snow etc significantly decrease visibility


Slide13 l.jpg

Transmit power

Received power

Beam wander

Time

Time

Time

Time

Scintillation

Combined effect

Time

Overview of FSO systems cont.

Factors influencing performance of FSO systems

Atmospheric effects

Atmospheric turbulence has a significant impact on the quality of the free-space optical beam propagating through the atmosphere.

Other effects include: - beam broadening and- angle-of-arrival fluctuations

Suppression techniques: - Aperture averaging- Adaptive optics- Diversity techniques- Coding techniques

Reduces the optical beam power at the receiver point and causes burst errors


Experimental field l.jpg

Experimental field

Bldg. 14 Waseda University Nishi Waseda Campus

1 km

Bldg. 55 Waseda University Okubo Campus

Satellite view of the test area

Source: Google earth


New rofso system experiment setup cont l.jpg

New RoFSO system experiment setup cont.

RoFSO antenna installed on Bldg 14 rooftop

Okubo campus Bldg. 55S

Beacon signal

IR viewer

Waseda campus Bldg 14 rooftop


Slide16 l.jpg

Main transmit and receive aperture

Si PIN QPD for coarse tracking using beacon signal

BS1

Main transmit and receive aperture

Digital mobile radio transmitter tester(Anritsu MS8609A)

Post EDFA

SMF

BS2

collimator

FPM(Fine Pointing Mirror)

RoFSO antenna tracking adjustment and monitoring PC

Beacon signaltransmit aperture

InGaAs PIN QPDfor fine tracking

Beacon Source

Rough tracking beacon projection aperture

Opticalsource

BoostEDFA

DWDM D-MUX

Bldg. 14 Nishi Waseda campus

Weather measurement device

RF-FSO antenna

Optical power meter(Agilent 8163A)

Atmospheric turbulence effects recording PC

Bit Error Rate Tester(Advantest D3371)

Atmospheric effects measurement antenna

RoFSO antenna

Bldg. 55S Okubo campus


Slide17 l.jpg

New RoFSO system experiment setup diagram

RF-FSOantenna

RF-FSOantenna

RF-FSO link

RoFSO link

RoFSOantenna

RoFSOantenna

Opt.circulator

Opt.circulator

filter

EDFA

Filter & ATTN

TrackingPC

Signal Analyzer

2.5Gbps Opt. Tx

Power meter

2.5Gbps Opt. Rx

Opt. Source

Clock

Data

PC

Signal Generator

BERT

BERT

PC

Bldg. 14 Nishi Waseda Campus

Bldg. 55S Okubo Campus


Slide18 l.jpg

New RoFSO system experiment

Characteristics of FSO antennas used in the experiment


Slide19 l.jpg

Results: CNR and ACLR characteristics for RF-FSO cont.

Effects of weather condition

Relationship between CNR and ACLR

WCDMA received signal spectrum

WCDMA: Wideband Code Division Multiple AccessCNR: Carrier to Noise RatioACLR: Adjacent Channel Leakage Ratio (a quality metric parameter for WCDMA signal transmission)


Slide20 l.jpg

Results: CNR and ACLR characteristics for RF-FSO

112 dB

45 dB

RF signal transmission characteristics measured using RF-FSO system


Slide21 l.jpg

Results: BER and received power characteristics

RoFSO system

BER and received power characteristics measured using RoFSO system


Slide22 l.jpg

Results: CNR characteristics

RF-FSO system

CNR characteristics measured using RF-FSOsystem


Slide23 l.jpg

Results: ACLR and optical received power measurement

RoFSO system

With EDFA: -24.5 dBm

Without EDFA: -15 dBm

Received 3GPP W-CDMA signal ACLR spectrum(3GPP Test Signal 1 64 DPCH)

Variation of ACLR with the measured received optical power


Slide24 l.jpg

Results: EVM measurement

RoFSO system

Error Vector Magnitude (EVM)

  • EVM is the ratio in percent of the difference between the reference waveform and the measured waveform.

  • EVM metric is used to measure the modulation quality of the transmitter.

  • The 3GPP standard requires the EVM not to exceed 17.5%


Slide25 l.jpg

Summary

  • Presented characteristics of RF signals transmission using FSO links under various weather conditions reflecting actual deployment scenarios.

  • Measured, characterized and quantified important quality metric parameters e.g. CNR, ACLR, EVM, BER, optical received power etc significant for evaluation of RF signal transmission using FSO links.

  • A properly engineered RoFSO link can be used as a reliable next generation access technology for providing heterogeneous wireless services in the absence of severe weather conditions.

  • Further work on simultaneous transmission of multiple RF signals by DWDM technology using the RoFSO system are ongoing.

  • The results are significant in design optimization, evaluation, prediction and comparison of performance as well as implementation issues/guidelines of RoFSO systems in operational environment.


Thank you for your attention kamugisha kazaura kazaura@ aoni waseda jp l.jpg

Supported by

This work is supported by a grant from the National Institute of Information and Communication (NICT) of Japan

Thank you for your attention

Kamugisha KAZAURA (カムギシャ カザウラ)

[email protected]


Slide27 l.jpg

I. Development of an Advanced DWDM RoFSO Link System

- Transparent and broadband connection between free-space and optical fiber

- DWDM technologies for multiplexing of various wireless communications and broadcasting services

DWDM RoF

DWDM RoFSO

Cellular

Mobile NW

Cellular BS

Scintillation

Digital TV

FSO

Tx,Rx

FSO

Tx,Rx

Digital TV

WDM

OE, EO

WDM

WLAN

WLAN AP

River, Road, etc

Internet

New Wireless

Universal Remote BS

New Wireless

Services

Optical Free-Space

Fiber-rich Area

Rural Area without Broadband Fiber infrastructure

OE/EO

OE

III. Long-term Demonstrative Measurements

- Pragmatic examination of advanced RoFSO link system

- Investigation of scintillation influence on various types of wireless services transported using the RoFSO system.

II. Development of Seamless Connecting Equipments between RoF, RoFSO and Wireless Systems

- Wireless service zone design

- Total link design through RoF, RoFSO, and Radio Links

OE/EO

OE/EO

Overview of DWDM RoFSO Link research


Slide28 l.jpg

Overview of FSO systems cont.

Atmospheric effects suppression techniques

  • Aperture averaging

    • Reducing scintillation effects by increasing the telescope collecting area.

  • Adaptive optics

    • Measure wavefront errors continuously and correct them automatically.

  • Diversity techniques

    • Spatial diversity (multiple transmitters and/or receivers)

    • Temporal diversity (signal transmitted twice separated by a time delay)

    • Wavelength diversity (transmitting data at least two distinct wavelengths)

  • Coding techniques

    • Coding schemes used in RF and wired communications systems.


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