University of Nevada, Reno Performance Analysis of Voice Transfer Using Multi-Transceiver Optical Communication Structures Abdullah Sevincer, Hasan T. Karaoglu, and Murat Yuksel Project Website: IEEE ICSOS 2011, Santa Monica, CA

Outline Motivation Literature Survey Previous work & LOS Algorithm Prototype Implementation Experiments & Results Conclusion & Future Work

Motivation RF spectrum is highly saturated – need alternative mediums for MANETs – Free-Space-Optical communication may serve as an alternative complementary medium to RF Spectrum characteristics – 100+ GHz bandwidth – Low power per bit – License free Directional communication – Spatial reuse – Low probability of intercept – Full-duplex transceivers Device characteristics – Smaller form factor – dense packaging is possible – More durable – Issues to be solved (among others): LOS – availability, and detection when available Mobility or sway – LOS maintenance

4 Motivation: FSO-MANETs Free-Space-Optical (FSO) Communications Mobile Ad-Hoc Networking High bandwidth Low power Dense spatial reuse License-free band of operation Mobile communication Auto-configuration Free-Space-Optical Ad Hoc Networks Spatial reuse and angular diversity in nodes Low power and secure Electronic auto-alignment Optical auto-configuration (switching, routing) Project Website:

Motivation: FSO-MANETs Our approach and focus to achieve the vision of FSO-MANETs – Low altitude and shorter ranges LOS becomes the major issue not the visibility Obstacles are common than the visibility problems – Cheaper devices (LEDs) with redundancy Packaging and managing many transceivers per node Electronic steering becomes possible if packaging provides angular diversity No need for mechanical steering

Motivation Electronic steering over multi-transceiver FSO nodes – By using multiple transceivers per node and automatically detecting neighbor nodes that are in LOS each other, we showed how to maintain the LOS alignment on FSO nodes. [IEEE ICC’10] Question: “Can we use such multi-transceiver structures for streaming-style applications which may require little or no disconnection?” 3-D optical antenna design.

FSO Literature High altitudes and longer ranges – FSO communications with a focus on coding and modulation techniques – Attaining longer transmission ranges, hardware design issues, and solutions against mobility – Focus on long distance (up to 7 kms) point-to- point applications with employing high-speed laser or VCSEL hardware. Our focus: Low altitudes and shorter ranges

FSO Literature Multiple elements/transceivers in FSO communication in interconnects which communicate over very short distances. The main issues: – interference (or cross-talk) between adjacent transceivers due to finite divergence of the light beam – Misalignment due to vibration.

FSO Literature FSO transmitters are highly directional: – comes with a cost of LOS alignment problem – Requires smart mechanisms to manage LOS among transceivers during an ongoing transmission. – Mechanical systems: (High maintenance and expensive, not fast enough to recover disruptions, multi-point-to-multi-point communication are not considered). Our focus: Electronic steering with a redundancy of transceiver devices

Previous Work & LOS Detection Algorithm Instead of mechanical steering, we implemented “electronic steering” over spherical optical antennas. LOS detection and alignment establishment protocol via fast handshakes among transceivers of neighboring nodes. – Quick and automatic hand-off of data flows among different transceivers – Omni-directional propagation and spatial reuse at the same time – Assigning logical data streams to appropriate physical transceivers/channels

Prototype Implementation Improved prototype with faster transceivers Voice file transfers to evaluate performance of our LOS detection and alignment establishment protocol over streaming-style application traffic. Mean Opinion Score (MOS) to evaluate voice transfer. MOSRatingPerceived Quality 4-5ExcellentToll Quality 3-4GoodCell Phone Quality <3FairUnacceptable <2BadUnintelligible

Prototype-Hardware Controller Board: – PIC32 Ethernet Starter Kit – Expansion board FSO Transceivers

Prototype-Setup NODE-B NODE-C NODE-A TR-B TR-C TR1-A TR2-A Wireless Link

Prototype-Experiments Transceiver Performance Test: – Half Duplex Line – Portable Document File (PDF): 3637 bytes – File Transfer at varying distances NODE-B NODE-A TR-B Wireless Link

Prototype-Setup-Experiments NODE-B NODE-C NODE-A TR-B TR-C TR1-A TR2-A Wireless Link

Prototype-Experiments Simultaneous File Transfer – Image Transfer from Node-A to both Node-B and Node-C – Half Duplex and Full Duplex Line – Image File Length: 7572 bytes Voice File Transfer – 6 different voice file transfer for MOS evaluation – Voice File Transfer at varying distances

Results Transceiver Performance Test Half Duplex Image File Transfer Full Duplex MOS Performance: 6 Files MOS Performance: varying distance Good MOS Values! Unacceptable Quality

Conclusion & Future Work Prototype: FSO system: multiple data streams Simultaneous voice file transfers with minimal disruptions and overheads Multimedia service with off-the-shelf components: Multi-transceiver & directionality Future Work: Improvement on the quality of voice transfer Improve the prototype: faster transceivers Link-and physical layer buffering mechanisms: reduce misalignment effects

Questions? Acknowledgments This work was supported by the U.S. National Science Foundation under awards and and DARPA under contract W31P4Q-08-C-0080