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OLPC Mesh networking improvements


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OLPC Mesh networking improvements

  1. 1. OLPC Mesh network improving Arina Rudakova (Saint-Petersburg Elelectrotechnical University «LETI») 3rd FRUCT seminar Saint-Petersburg 23 May 2008
  2. 2. Agenda Introduction Problem definition Domain analysis Solution Project timeline
  3. 3. I. Introduction
  4. 4. One Laptop Per Child  Home:  The mission of the One Laptop per Child association is to develop a low-cost laptop—the "XO Laptop"— to revolutionize how we educate the worlds children. Goal is to provide children around the world with new opportunities to explore, experiment, and express themselves.
  5. 5. XO laptops hardware Dimensions: 242mm × 228mm × 32mm CPU x86-compatible processor AMD Geode LX-700 433 Mhz, 64KB each L1 I and Dcache; at least 128KB L2 cache DRAM memory: 256 MiB dynamic RAM BIOS: 1024KiB SPI-interface flash ROM Mass storage: 1024 MiB SLC NAND flash, high-speed flash controller Display: Liquid-crystal display: 7.5” dual-mode TFT display Keyboard: 80+ keys, 1.0mm stroke; sealed rubber-membrane key-switch assembly Gamepad: Two sets of four-direction cursor-control keys Touchpad: Dual capacitance/resistive touchpad; supports written-input mode Audio: AC’97 compatible audio subsystem Integrated color video camera: 640 x 480 resolution at 30 FPS Wireless Networking: Integrated 802.11b/g (2.4GHz) interface; 802.11s (Mesh)networking supported; dual adjustable, rotating antennas support diversity reception;capable of mesh operation when CPU is powered down;
  6. 6. XO laptops software Operating system: Linux Kernel: Linux 2.6.22; Fedora 7 base environment. User environment: Sugar GUI, written in Python, on top of the X Window and the Matchbox WM Programming environments (main): − Python (Version 2.5); − JavaScript; − Csound, music programming language; − Etoys, an implementation of Squeak using Smalltalk, an object-based programming language; − Turtle Art, a graphical programming environment; − Adobes Flash Player, Java, Gnash Libraries − Mozilla Gecko/Xulrunner (the Firefox web engine); − GUI toolkit (GTK+) (Gnome); − Matchbox window manager; − X Window System Foundation; − Multimedia framework: GStreamer and RealNetworks; − Gettext, the GNU internationalization library
  7. 7. Neighborhood:Collaboration interface The Neighbourhood view displays all the connected XO laptops within a child’s community, and what activities they are sharing. Each child is represented by a different colour If there is a shared document or activity being collaborated on by a number of children, it will show up within this view.
  8. 8. XO Mesh goals Ability to act as a mesh point when laptops main CPU is off. Support for asymmetric links/paths. Incremental releases—mesh networking is available immediately on XO; Upgrades will continue to improve functionality and adherence with standards. Simultaneously acts as a mesh point and an infrastructure node. Standards Compliance: follow 802.11s draft when possible.
  9. 9. II. Problem definition
  10. 10. Mesh network types Infrastructure wireless mesh networks: Mesh routers form an infrastructure for clients. Client wireless mesh networks: Client nodes constitute the actual network to perform routing and configuration functionalities. Hybrid wireless mesh networks: Mesh clients can perform mesh functions with other mesh clients as well as accessing the network
  11. 11. Distinguishing features dynamics structure
  12. 12. Routing mechanism in mesh Redundante links usage − Fault tolerance − Load sharing Traffic analysis Network diversity Route aggregation
  13. 13. Routing overhead reasons Nodes number influence on the amount of control traffic Network changes dynamics influence on the amount of control traffic Route length influence on the amount of control traffic
  14. 14. Project Goals Reducing Routing overhead OLPC implementation
  15. 15. III. Domain analysis
  16. 16. Ad-hoc Routing types Pro-active or Table-driven Reactive Routing or On-demand Flow Oriented Adaptive Routing or Situation-Aware Hybrid (Pro-Active and Reactive)
  17. 17. Industrial and open source implementations AWDS (Ad-hoc Wireless Distribution Service) DSDV (Highly Dynamic Destination-Sequenced Distance Vector routing protocol) – based on Bellman-Ford Routing Protocol AODV (Ad-hoc On-demand Distance Vector) Mobile Ad-hoc On-Demand Data Delivery Protocol MPRDV (Multipoint Relay Distance Vector protocol) SSR (Signal Stability Routing protocol) PLBR (Preferred link based routing) TORA (Temporally-Ordered Routing Algorithm routing protocol) HRPLS (Hybrid Routing Protocol for Large Scale Mobile Ad-Hoc Networks with Mobile Backbones) HSLS (Hazy Sighted Link State routing protocol) ZRP (Zone Routing Protocol)
  18. 18. IV. Solution
  19. 19. Solution components Routing area restriction Dynamic selection of optimization radius External definition of routing overhead
  20. 20. Routing overhead chart m — tree arity n — nodes number R — dynamics
  21. 21. Possible reasons of routing overhead increase Number of nodes increase Network dynamics increase Network radius increase Using aggressive updating strategy
  22. 22. Routing area restrictionFor effective routing area definition we should introduce some definitions.G(t)=<V,E>, where V – set of nodes, E – archesG(t) describes network topologyd(vi,vj) – distance between vi and vjvi: Ri>0, G (vi , Ri ) ⊂ G (t ), d (vi , v j ) ≤ RiChoose Ri with regard to time needed for collection of information about G(vi,Ri)G(vi,Ri) - effective routing area for vi, G (vi , Ri ) ≡ R(vi )
  23. 23. External and internal routing records External routing records (only in edge nodes) Internal routing records (always true)
  24. 24. Routing optimization area Local optimization Global optimization Optimization in restricted area
  25. 25. Local sample Information collection – 1 hop Route defining – 1 hop «Trust» zone – 1 hop Control traffic is minimum
  26. 26. Global sample Information collection – whole net Route defining – whole net «Trust» zone – whole net Control traffic is maximum
  27. 27. Restricted sample Information collection is restricted with R Route defining – within R radius «Trust» zone – within R radius Control traffic is restricted
  28. 28. Failure detection  At first only one router knows about a route failure  After the message to sender about the impossibility of passing, the whole effective routing area is informed  The sender gets informed when its timer is over
  29. 29. Routing overhead analysis
  30. 30. V. Project timeline
  31. 31. Global planThe past 2007 Autumn, generic task definition, domain investigation 2008 Winter, getting XO devices, experience XO system programmingThe future 2008 Summer, public presentation our of solution ideas (conference proceedings or paper) 2008 Autumn, implement modules for NS2 and simulations 2008 Winter, contribute some code for XO laptops 2009 Spring, defence of the master thesises at LETI
  32. 32. Thank you.Any questions?