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Raabta: Low-cost Video Conferencing for the Developing World

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  • 1. Raabta: Low-cost Video Conferencing for the Developing World Zubair Nabi zubair.nabi@cantab.net Information Technology University, Pakistan* MobiCom Workshop on Lowest Cost Denominator Networking for Universal Access 30 September, 2013 * Now at IBM Research, Dublin
  • 2. Raabta ● Leverage existing analog cable TV networks to provide video conferencing ● Raspberry-Pi instances as end-hosts ● Video conferencing application co-design – ● Multi-layered encoding and dynamic recovery Simple text-free interface
  • 3. Outline ● Motivation ● Background ● Design Goals ● Raabta ● Beyond Raabta ● Conclusion and Future Work
  • 4. Motivation ● ● ● ● Daily income for > 50% of the world: < $2 The Internet has the power to improve the human condition 10% increase in broadband Internet penetration leads to 1.4% increase in GDP (World Bank) Cognizance of social, economic, and technological conditions
  • 5. Proposed Solutions ● Challenges: – – Intermittent and bad power – Extreme weather conditions: dust, humidity, etc. – Frequent equipment failure – Lack of trained local workforce – ● Monetary and engineering costs Rolling investment required WiMAX, satellite, long-distance WiFi, ZigBee, optical, cellular etc. – Both backbone and last-mile access – Also plagued by shortcomings
  • 6. Observations ● Internet access not an underpinning technology – ● ● Backbone access extremely expensive Basic, community-wide communication required Systems designed for the developing world illsuited due to fundamental differences, such as low population density
  • 7. Design Goals ● Cost: as low as possible ● Power: low power draw ● Failure: norm rather than exception ● User-interface: simple enough to be used by low-literate people ● Internet connectivity: not a requirement ● Infrastructure: leverage existing ● Operational sustainability: self-managing
  • 8. Background: Analog Cable Networks ● Broadcast-based shared medium ● Downstream traffic (Gbps): [4.9, 6.6] ● Cable modem as MAC layer bridge ● Link-layer protocol can be offloaded ● At least 12 million people in rural areas in Pakistan own a TV and 3.9 million have cable connections (Gallup)
  • 9. Background: Raspberry Pi ● ● General-purpose single board computer Broadcom system-on-chip processor: ARM 700MHz processor, 24GFLOPS GPU, and integration audio and video ● Multiple video output options ● Optional Ethernet
  • 10. Background: Video Conferencing ● 3 functional aspects: 1) Overlay topology 2) Encoding scheme 3) Packet loss recovery ● High-bandwidth and low-latency requirement ● Tolerance to device and network heterogeneity
  • 11. Raabta
  • 12. Raabta: End-host Component Raspberry Pi Model B Camera Board External Cable Modem USB Sound Card USB Keyboard USB Mouse Headset Total Cost ($) 35 25 20 7 2 2 1 92
  • 13. Raabta: Network ● ● Status-quo: Downstream spectrum: 50860MHz, 6MHz per channel (42Mbps: 256QAM), 135 channels Key modifications: – Use non-TV channels for video conferencing – Same band for upstream/downstream – Delegate MAC operation to end-host – Replace uni-directional amplifiers with bi-directional ones
  • 14. Raabta: MAC Layer ● No centralized arbitration 1) FDMA • • Slice up free spectrum into equi-sized slots 200KHz ensures 700Kbps for very good quality video • • 135 end-hosts 25KHz ensures 84Kbps for reasonable QoE • 1480 end-hosts 2) CSMA/CD • Treat entire spectrum as a large shared channel • • • ● 37MHz, 258Mbps, 1.6ms RTT, 51600byte minimum frame size 51600 MPEG frame: 51580 payload + 4 header + 16 FEC Each modem listens for its MAC or broadcast address Explore different points in the design space
  • 15. Raabta: Network Layer ● ● LAN so network layer not required but unmodified IP used 2 key advantages: – – ● Potential wider Internet connectivity IP multicast for efficient multi-party conferencing Distributed protocol for dynamic address allocation
  • 16. Raabta: Transport Layer ● ● Vanilla RTP atop UDP Each RTP packet: timestamp, sequence number, and payload format ● RTCP for synchronization across streams ● For each call, 4 streams initiated – – One stream each for audio and video – ● SIP for destination port selection Two streams for synchronization Packet loss: dynamic switching b/w FEC and selective acks based retransmission
  • 17. Raabta: Video Conferencing 1) User database • Init: Broadcast user ID, picture, and IP • Also broadcast regularly 2) Multi-layer encoding • • Base layer + additional incremental layers Resilient to high loss, quality of video determined by recipient downlink capacity 3) UI • Text free, although optional text messaging • Picture-driven with audio feedback
  • 18. Beyond Raabta ● Internet connectivity – ● Community-wide applications – ● Simple to extend using low-cost solutions Telemedicine, distance learning, etc Operator incentive – – Simple management due to decentralization – ● No additional operational or power cost Flat monthly rate Leveraging existing infrastructure – Community needs to focus on this
  • 19. Conclusion and Future Work ● ● Possible to provide low-cost video conferencing using existing infrastructure and simple components Future work: – Implementation and evaluation of the system – Closer inspection and analysis of MAC – Deployment in the wild
  • 20. Q? ● Acknowledgments: – Anil Madhavapeddy for comments and suggestions – Arjuna Sathiaseelan and Jon Crowcroft for arranging remote talk – Images: FreeDigitalPhotos.net, Berkeley TIER, wikimedia.org, and evidence4action.net