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Networked Systems in Developing Regions Challenges and Opportunities

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Title: Networked Systems in Developing Regions Challenges and Opportunities


1
Networked Systems in Developing
RegionsChallenges and Opportunities
  • Lakshminarayanan Subramanian
  • Courant Institute of Mathematical Sciences
  • New York University
  • Joint work with many fantastic collaborators!
  • (Courant, NYU Med, NYU Wagner, UC Berkeley,
    Intel, Univ of Washington, Univ of Colorado,
    Amrita University, Aravind Eye Hospitals)

2
Disclaimers of a realist
  • I am not a philanthropist
  • NGOs are great, but may not scale or be
    sustainable
  • Information and Communication Technologies (ICT)
    can only be an aid but cannot alleviate poverty
  • I believe in cell-phones

3
Causes of poverty
  • Lack of awareness/opportunity
  • A negative earnings cycle
  • Serious healthcare problems
  • Prolonged debt
  • Inheritance from family/society

4
Strategies to eliminate poverty
  • Jeffrey Sachs Provide aid to the
    underprivileged
  • William Easterly 2.3 trillion dollars of aid,
    nothing much to show. Promote homegrown
    solutions
  • C.K. Prahlad Tap the fortune at the bottom of
    the pyramid
  • Amartya Sen Promote development at the rural
    level

5
The Bottom A Brief Description
  • 3-4 billion people with per-capita equivalent
    purchasing power (PPP) less that US2,000 per
    year
  • Could swell to 6-8 billion over the next 25 years
  • Most live in rural villages or urban slums and
    shanty townsmovement towards urbanization
  • Education levels are low or no-existent
    (especially for women)
  • Markets are hard to reach, disorganized, and very
    local in nature

6
The cost of being Poor
Bombay area Dharavi(shantytown) Warden Road Ratio
Credit (APR) 600-1000 12-18 60-75x
Water (100 gal) 0.43 0.011 37x
Phone (cents/min) 4-5 2.5 2x
Diarrhea Meds 20 2 10x
Rice (/kg) 0.28 0.24 1.2x
7
Even the Very Poor Spend
  • Dharavi, one of the poorest villages in India
  • 85 have a TV
  • 50 have a pressure cooker
  • 21 have a telephone
  • but cant afford a house
  • Even the poorest of the poor in Bangladesh
  • devote 7 percent of income to communications
    services (GrameenPhone)
  • These are valid markets

8
ICT A Big Missing Piece
  • Technology can impact everyone
  • Bottom of the Pyramid
  • Not just Internet access
  • Health, education, government, commerce
  • Enable profitable businesses
  • Must be scalable and sustainable
  • Poor are a viable market
  • Focus on income creation, supply chain efficiency
  • Not charity, not financial aid
  • Promotes stability, entrepreneurism and social
    mobility
  • First World technology is a bad fit
  • New research agenda

9
How can ICT help?
  • Communications
  • Awareness, access to external world, phone calls
  • Healthcare
  • Where there is No Doctor? Rural healthcare
    system
  • Telemedicine/consultation
  • Continuing Medical Education for Health-workers
  • Low-cost diagnostic tools
  • Finance
  • Microfinance audit, insurance schemes
  • Education
  • Educational modules, distance learning

10
Other important areas
  • Commerce
  • Supply Chain
  • Agriculture
  • E-Governance

11
Where has ICT helped so far?
  • Very few ICT based efforts worldwide have led to
    a large-scale success
  • ICT adoption successes
  • Cell-phone, Radio, TV
  • Why?
  • Figure out what they need
  • Never thrust a technology
  • Economics not in favor
  • Make change a gradual phenomenon!

12
A five-step approach
  • 1. Identify basic real-world problem
  • 2. Where can ICT help?
  • 3. Research challenges?
  • 4. What is the appropriate solution?
  • 5. Deployment?

13
ICT research challenges
14
Network connectivity is key!
  • Traditional wire-line connectivity solutions are
    not economically viable!
  • Potential options
  • Develop new low-cost connectivity solution!
  • Leverage existing low-bandwidth wireless
    solutions
  • Cellular, Satellite, CDMA450, WiMax
  • Intermittent links are a fact of life
  • Budget constrained links
  • SMS
  • Power outages
  • Physical transportation links

15
Research Challenges
  • Low-cost high-performance network connectivity
  • WiLDNet WiFi-based Long Distance Networks
  • Wireless Mesh Networks
  • Intermittent distributed systems
  • Leveraging the next-generation cell-phone
  • Redesigning applications to tolerate
    intermittency
  • Interactive applications in low bandwidth
    environments
  • What can you do using 30 Kbps bandwidth?
  • Application specific research challenges
  • Security, User-interface, NLP, Image processing
    etc.

16
Research Challenges
  • Low-cost high-performance network connectivity
  • WiLDNet WiFi-based Long Distance Networks
  • Wireless Mesh Networks
  • Intermittent distributed systems
  • Leveraging the next-generation cell-phone
  • Redesigning applications to tolerate
    intermittency
  • Interactive applications in low bandwidth
    environments
  • What can you do using 30 Kbps bandwidth?
  • Application specific research challenges
  • Security, User-interface, NLP, Image processing
    etc.

17
Rural Connectivity in Developing Regions
  • Current solutions
  • Wired
  • Dial-up/DSL
  • Optical fiber
  • Cellular
  • VSAT
  • WiMax

18
WiFi-based Long Distance Networks
  • WiLD links use standard 802.11 radios
  • Longer range up to 150km
  • Directional antennas (24dBi)
  • Line of Sight (LOS)
  • Why choose WiFi
  • Low cost of 500/node
  • Volume manufacturing
  • No spectrum costs
  • Customizable using open-source drivers
  • Good datarates
  • 11Mbps (11b), 54Mbps (11g)

19
WiLD Deployments
  • Bay Area
  • 7 links up to 45km
  • Experimental testbed
  • India at Aravind Hosp
  • 12 links up to 15km
  • 9 Rural Clinics
  • 25,000 patients/yr
  • Scaling to 50 clinics
  • Ghana
  • 5 links up to 100km
  • Electronic Library

Aravind Network, Theni, India
Other Projects
  • Digital Gangetic Plains
  • 30 links
  • upto 39 km
  • 802.11 APs
  • Akshaya Wireless
  • 400 nodes
  • 2-25 km
  • commercial APs
  • CRCNet,New Zealand
  • 17 links
  • upto 13 km
  • Soekris SBCs

20
Akshaya A Case study
  • Joint project between the State of Kerala in
    India and Tulip IT
  • Wireless IP network set up in the district of
    Malappuram 630 eCenters in all
  • Backhaul and last mile links are based on
    proprietary technologies
  • 1 center for every 2000 families

21
Total Costs for network deployment
WiFi/WiMax is the most economically viable
solution Fiber/WiMax is the least economically
viable
22
Experience with WiLD Networks
  • In the field, point-to-point performance is bad
  • On a 60km link in Ghana
  • We get 0.6 Mbps TCP vs 6 Mbps UDP
  • On a relay (single channel)
  • We get only 2 Mbps TCP

23
WiLDNet Design Overview
  • Fix 802.11 protocol problems
  • Replace CSMA -gt TDMA
  • Enforce synchronization of multiple links
  • Variable channel loss
  • Adaptive loss recovery
  • Combine retransmissions and FEC

24
Design Constraints
  • No hardware changes
  • Modify WiLD routers, not endpoints
  • Routers are inexpensive machines
  • low processing power
  • low energy budget (solar)
  • We want to be spectrum efficient

25
Problem with 802.11 ACKs
  • Low utilization
  • Large propagation delays
  • Stop wait inefficient
  • RTS/CTS makes it worse
  • ACK timeouts
  • ACK doesnt arrive in time
  • Retransmissions until retry limit reached

26
Problem Propagation Delay
  • Large propagation delay ? high collision
    probability

27
Design Choices for WiLDNet
  • Use Sliding Window flow control
  • 802.11 MAC ACKs disabled
  • Packet batches sent every slot
  • Slot allocation determined by demand
  • Replace CSMA with TDMA on every link
  • Alternate send and receive slots

28
Inter-Link Interference
Simultaneous Receive
Simultaneous Send
Send Receive
  • 12dB isolation
  • Disable CCA

29
Implicit Synchronization for TDMA
  • Every packet is time-stamped in TX slot
  • Slots are offset because of propagation delay
  • We dont use explicit marker packets to signify
    end of TX slot

?
Sender
TX slot
RX slot
Receiver
2P MAC protocol (Raman et al. Mobicom 05)
30
Channel Loss From external traffic
  • Strong correlation between loss and external
    traffic
  • Source (A) and interferer (I) do not hear each
    other

31
Loss Recovery Bulk ACKs FEC
  • Bulk ACKs
  • Aggregate ACKs (bit-vectors) sent with every
    packet
  • Use retransmissions for loss recovery
  • Retry limit can be per-packet
  • Adaptive FEC
  • Sender performs encoding of packets proactively
  • Packet level FEC
  • Tradeoff of BW and Delay
  • Bandwidth efficient use Bulk ACKs
  • TCP, bulk traffic
  • Delay efficient use Adaptive FEC
  • Voice, Video

32
WiLDNet Design Recap
  • Replace CSMA with TDMA
  • Loose time synchronization
  • To eliminate inter-link interference
  • Overcome variable channel loss
  • Adaptive loss recovery layer at link layer
  • Using Bulk ACKs BW efficient
  • Using FEC Delay efficient

33
Evaluation Multiple Hops outdoors
  • 2 hop network
  • 19km, 1.5km
  • WiLDNet Similar throughput
  • Same channel OR
  • Diff. channels
  • More spectrum efficient

Channels Through-put for TCP (Mbps)
802.11 Same 2.11
802.11 Diff. 4.50
WiLDNet Same 4.86
WiLDNet Diff. 4.90
34
Deployment
35
Wireless Mesh Networks
  • Rapidly deployable high performance wireless mesh
    networks
  • Current mesh networks have poor performance in
    multi-hop settings
  • What we are investigating
  • Multi-radio, Multi-channel
  • Nodes with directional antennas
  • Understanding multi-AP interactions
  • Visit the 12-node testbed in 715 Broadway!

36
Research Challenges
  • Low-cost high-performance network connectivity
  • WiLDNet WiFi-based Long Distance Networks
  • Wireless Mesh Networks
  • Intermittent distributed systems
  • Leveraging the next-generation cell-phone
  • Redesigning applications to tolerate
    intermittency
  • Interactive applications in low bandwidth
    environments
  • What can you do using 30 Kbps bandwidth?
  • Application specific research challenges
  • Security, User-interface, NLP, Image processing
    etc.

37
Intermittent Distributed Systems
  • How do we build conventional distributed systems
    in intermittent environments?
  • Connectivity is intermittent and unpredictable
  • Net bandwidth is limited
  • Potentially high delays
  • Potentially lossy environments
  • Examples
  • A distributed system of cell-phones using GPRS
    links and SMS messages to communicate
  • Web search from a rural cafe

38
Intermittent Web Search
  • A typical search today involves 4-8 queries!
  • Can we do web search in one round?
  • What we have done
  • Change the query interface
  • Specify all that you know about what you are
    searching for
  • Intermittent proxy issues multiple queries,
    prefetches and bundles response pages
  • Local proxy enables search within retrieved bundle

39
Intermittent ATM
  • How do you operate ATMs over intermittent
    environments?
  • Our solution
  • Enable offline authentication
  • Use approximate consistency results to split a
    bank balance into smaller entities
  • Provide a risk model to enable extra cash
    availability at ATMs

40
Research Challenges
  • Low-cost high-performance network connectivity
  • WiLDNet WiFi-based Long Distance Networks
  • Wireless Mesh Networks
  • Intermittent distributed systems
  • Leveraging the next-generation cell-phone
  • Redesigning applications to tolerate
    intermittency
  • Interactive applications in low bandwidth
    environments
  • What can you do using 30 Kbps bandwidth?
  • Application specific research challenges
  • Security, User-interface, NLP, Image processing
    etc.

41
Low-bandwidth video streaming
  • Multi-hop satellite network for distance learning
    /telemedicine
  • Very high delays, low bandwidth
  • Questions
  • Enhancing QoS on low bandwidth environments
  • OverQoS Overlay based QoS
  • On the fly transcoding
  • Can we develop an appropriate video codec that is
    easily adaptable to different rates?

42
Intermittent proxy
  • Imagine a distributed system over a multi-hop
    intermittent/low-bandwidth network
  • Content distribution, distributed databases,
    video streaming, client/server transactions, web
    search
  • Intermittent proxy
  • A generic optimization engine that performs
    resource allocation across flows on a
    low-bandwidth/intermittent link
  • Maintains soft application state to enhance
    performance
  • Performs local hop-hop recovery

43
Research Challenges
  • Low-cost high-performance network connectivity
  • WiLDNet WiFi-based Long Distance Networks
  • Wireless Mesh Networks
  • Intermittent distributed systems
  • Leveraging the next-generation cell-phone
  • Redesigning applications to tolerate
    intermittency
  • Interactive applications in low bandwidth
    environments
  • What can you do using 30 Kbps bandwidth?
  • Application specific research challenges
  • Security, User-interface, NLP, Image processing
    etc.

44
Cell-phone based applications
  • Cell-phone based Micro-finance
  • Use SIM as a cheap identity
  • Use programmable smart-phones to provide low-cost
    authentication
  • Benefits Reduce transaction costs and corruption
  • Cell-phone based Health record system
  • Health-workers in the field use cell-phones to
    enter health records
  • Need a distributed database syncronization/search
    mechanism which works over SMS-links
  • Cell-phone based cheap Inventory management
  • Why need RF-ID based systems?

45
Low cost paper-watermarking
  • Every piece of paper has an inbuilt random
    speckle pattern
  • Can we extract this speckle pattern to watermark
    any paper?
  • Use USB 60x microscope
  • Applications
  • Verification of paper based records
  • Cheap inventory management

46
Watermarking initial results
Nearly 90 match
Less than 20 match
47
Automated Diabetic Retinopathy
48
Medical Education Modules
  • Can we create medical education modules to teach
    a healthcare worker to become a malaria expert?
  • WiSE-MD modules for surgical education in NYU Med
  • Tailor modules for two focus areas
  • Malaria and Infectious diseases
  • Obstetrics and Gynecology

49
Other interesting problem areas
  • Traffic Signaling Networks
  • User interfaces
  • Text-free interfaces for semi-literate or
    illterates
  • Speech interfaces
  • Natural language processing
  • People interested in content in local language
  • Language translation

50
Questions?
  • Thank you!
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