HYBRID FSO/RF LINKS AND NETWORKS WITH DIVERSITY CONTROL - PowerPoint PPT Presentation

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HYBRID FSO/RF LINKS AND NETWORKS WITH DIVERSITY CONTROL

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HYBRID FSO/RF LINKS AND NETWORKS WITH DIVERSITY CONTROL Christopher C. Davis The Maryland Optics Group Department of Electrical and Computer Engineering – PowerPoint PPT presentation

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Title: HYBRID FSO/RF LINKS AND NETWORKS WITH DIVERSITY CONTROL


1
HYBRID FSO/RF LINKS AND NETWORKS WITH DIVERSITY
CONTROL
  • Christopher C. Davis
  • The Maryland Optics Group
  • Department of Electrical and Computer Engineering
  • University of Maryland, College Park, MD 20742

2
RESOLUTION IN NEAR-FIELD ACKNOWLEDGEMENTS
  • Dr. Stuart D. Milner Department of Civil and
    Environmental Engineering
  • Dr. Igor Smolyaninov, Department of Electrical
    and Computer Engineering
  • Dr Quirino Balzano, Department of Electrical and
    Computer Engineering
  • Professor Kyuman Cho (Sogang University, Seoul,
    KOREA)
  • Pam Clark, ITT
  • Linda Wasiczko, Sugianto Trisno, Jaime Llorca,
    Tzung-Hsien Ho, Heba El-Erian, Aniket Desai,
    Clint Edwards, (graduate students)
  • AFOSR, DARPA,NSA, ARL, Army CECOM

3
WI-FI
  • The current hot topic
  • Its growing popularity will cause its demise
  • Spectral overcrowding
  • Lack of security
  • Interference with other users and equipment
  • Remember CB radio?
  • But if you are mobile you cant be connected by
    wires

4
Dynamic, Reconfigurable Hybrid FSO/RF Wireless
Networks
Modified from a TeraBeam picture
5
Hybrid FSO/RF Wireless Networks WHY?
  • RF wireless networks
  • Broadcast RF networks are not scaleable
  • RF cannot provide very high data rates
  • RF is not physically secure
  • High probability of detection/intercept
  • Not badly affected by fog and snow, affected by
    rain
  • Optical wireless networks
  • Very high data rates
  • 2.5Gb/s commercially available
  • 1Tb/s demonstrated
  • Almost zero probability of detection/intercept
  • Affected by fog and snow

6
Hybrid FSO/RF Wireless Networks WHY?
  • Deal with the non-acceptance of optical wireless
    alone
  • High availability (gt99.99)
  • Much higher goodput than RF alone
  • Last/First Mile Solution
  • FSO is not regulated by the FCC
  • must be eyesafe
  • For greatest flexibility need unlicensed RF band
  • Installed optical fiber up to 1M/mile

7
A Hybrid FSO/RF Link Handles Weather A Hybrid
FSO/RF Network Involves Disparate Data Rates
8
Challenges and Developments
  • FSO is available commercially
  • has not been widely accepted
  • most systems do not do pointing, acquisition, and
    tracking (PAT)
  • most systems are not FSO/RF Hybrids
  • FSO/RF Hybrid networks are in the RD stage
  • High performance PAT must be developed

9
Challenges and Developments (2)
  • Many applications of FSO/RF networks involve
    dynamic situations
  • Reconfigurability (topology control) is required
  • Diversity of links (transmitter and receivers)
  • Changeover algorithms
  • Network optimization
  • DoD applications

10
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11
DYNAMIC AND VOLATILE ATMOSPHERICAND PLATFORM
EFFECTS
12
OPTICAL WIRELESS TRANSCEIVER
13
OMNIDIRECTIONAL OPTICAL WIRELESS TRANSCEIVER
14
Topology Control in Optical Wireless Networks
15
Pointing, Acquisition, and Tracking in Optical
Wireless Networks
  • Allows wireless links to be established and
    maintained between moving platforms
  • Maintains alignment of optical wireless links
  • Required for autonomous reconfiguration and
    topology control in optical wireless networks

16
Agile Optical Wireless Transceiver and Motorized
Platform
  • Data rate 155Mb/s
  • High speed (800K steps per second), resolution
    and pointing accuracy up to 0.00072 per step
  • Fish-eye lens (180) used to identify and track
    neighbor nodes (beacons)

17
Bi-Static Transceiver Design
  • Mono-static
  • Advantages Reduces the complexity of PAT process
  • Disadvantages Power isolation problem (TX/RX
    feedback)
  • Bi-static
  • Advantages No power isolation problem
  • Disadvantages
  • 1. Extra alignment process required to obtain
    parallel axes
  • 2. Potential misalignment in short-distance
    application

18
Link Failures between 2 Transceivers
For large application distance
For short application distance
19
PAT Process
20
Experimental Setup
  1. Study the performance of the link with respect to
    link closure latency for different motor
    parameters
  2. To investigate the effects of larger FOV of our
    system

21
FEATURES OF OUR CURRENT OPTICAL WIRELESS SYSTEMS
  • Bistatic TX/RX systems
  • 1.3?m and 1.55?m transmitters
  • CPC and lens based receivers
  • Fast aspheric lens receivers
  • Cassegrain and Fresnel lens receivers
  • Rugged alignment stages
  • Topology control

22
OUR NEW CONCEPTS AND THEIR IMPACT
  • Maximally efficient use of high data rate FSO and
    RF communication modes
  • Network and link recovery everywhere through
    communication mode diversity and autonomous
    Physical and logical reconfigurability
  • Reduced GTT due to instantaneous network recovery
  • Physical reconfigurability assures gt 99
    availability
  • Higher optical availability increases MDR
  • Seamless diversity control between optical and RF
    communication
  • Internet-like software fully portable to DoD
    systems
  • Network software is independent of terminal
    design specifics

23
INNOVATION
  • Intelligent Aperture Diversity and Media
    Controller
  • Smart identification of RF/FSO availability at
    each RX/TX
  • Dynamic allocation of FSO/RF
  • Autonomous physical and logical reconfiguration
  • Make before break dissemination of topologies
    using high availability RF control channel
  • Enhanced TCP/IP protocol suite for Hybrid FSO/RF
    Networks
  • Multi-Protocol Label Switching (Traffic
    Engineering) exploits media diversity
  • Proxy software provides instantaneous reaction to
    physical change in topology
  • Autonomous reconfigurability integrated with
    TCP/IP suite
  • Comprehensive network modeling and simulation
  • Advanced atmospheric propagation modeling
    (turbulence, aerosols, obscuration)
  • Discrete Event Simulation for Hybrid Networks to
    aid implementation planning

24
BACKUP SLIDES
25
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26
The DARPA ORCLE PROGRAM(formerly THOR Program)
  • Long range (up to 100km) high altitude (10km)
    laser communication links
  • Rytov variance is
  • ?2lnI Ranges from 10 to 100
  • Small Cn2, but long range makes this a strong
    turbulence situation
  • May be strong boundary layer turbulence at
    transmitter and receivers

27
Many Link Physics and Engineering Issues
  • Turbulence
  • Variations with height
  • Obscuration
  • Optical depth
  • Spatial distribution
  • Aerosols
  • Aperture averaging
  • Transceiver optimization

28
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