2. The Maryland Optics Group February 17Wireless Communications 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

3. The Maryland Optics Group February 17Wireless Communications 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

4. The Maryland Optics Group February 17Wireless Communications 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 can’t be connected by wires

5. The Maryland Optics Group February 17Wireless Communications Dynamic, Reconfigurable Hybrid FSO/RF Wireless Networks Modified from a TeraBeam picture

6. The Maryland Optics Group February 17Wireless Communications 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

7. The Maryland Optics Group February 17Wireless Communications Hybrid FSO/RF Wireless Networks – WHY? Deal with the non-acceptance of optical wireless alone High availability (>99.99%) 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

8. The Maryland Optics Group February 17Wireless Communications A Hybrid FSO/RF Link Handles Weather A Hybrid FSO/RF Network Involves Disparate Data Rates

9. The Maryland Optics Group February 17Wireless Communications 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 R&D stage High performance PAT must be developed

10. The Maryland Optics Group February 17Wireless Communications 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

11. The Maryland Optics Group February 17Wireless Communications

12. The Maryland Optics Group February 17Wireless Communications DYNAMIC AND VOLATILE ATMOSPHERIC AND PLATFORM EFFECTS

13. The Maryland Optics Group February 17Wireless Communications OPTICAL WIRELESS TRANSCEIVER

14. The Maryland Optics Group February 17Wireless Communications OMNIDIRECTIONAL OPTICAL WIRELESS TRANSCEIVER

15. The Maryland Optics Group February 17Wireless Communications Topology Control in Optical Wireless Networks Network Layer Link Layer Physical Layer Topology Control Autonomous Backbone Reconfiguration Pointing, Acquisition and Tracking

16. The Maryland Optics Group February 17Wireless Communications 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

17. The Maryland Optics Group February 17Wireless Communications 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)

18. The Maryland Optics Group February 17Wireless Communications 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 Bi-Static Transceiver Design

19. The Maryland Optics Group February 17Wireless Communications Link Failures between 2 Transceivers For large application distance For short application distance

20. The Maryland Optics Group February 17Wireless Communications PAT Process Object disappears Acquisition Process Tracking Process Transceiver Axis Alignment Step Select the desired target from the CCD image System Scanning Step Using TCP/IP socket to check link availability Link Table Update Record the current [θ,φ] into the link table Object still exists Tracking Process Motion Prediction Analysis (Track beacon)

21. The Maryland Optics Group February 17Wireless Communications 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

22. The Maryland Optics Group February 17Wireless Communications 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

23. The Maryland Optics Group February 17Wireless Communications 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 > 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

24. The Maryland Optics Group February 17Wireless Communications 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

25. The Maryland Optics Group February 17Wireless Communications BACKUP SLIDES

26. The Maryland Optics Group February 17Wireless Communications

27. The Maryland Optics Group February 17Wireless Communications The DARPA ORCLE PROGRAM (formerly THOR Program) Long range (up to 100km) high altitude (10km) laser communication links Rytov variance is  2 lnI Ranges from 10 to 100 Small C n 2, but long range makes this a strong turbulence situation May be strong boundary layer turbulence at transmitter and receivers

28. The Maryland Optics Group February 17Wireless Communications Many Link Physics and Engineering Issues Turbulence –Variations with height Obscuration –Optical depth –Spatial distribution Aerosols Aperture averaging Transceiver optimization

29. The Maryland Optics Group February 17Wireless Communications