Nancy%20Lynch

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Virtual Node Layers

• Nancy Lynch
• Massachusetts Institute of Technology, CSAIL
• Workshop on Critical Research Areas in Aerospace
  Software
• MIT
• August 9, 2005

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Virtual Node Layers

• Collaborators
• Shlomi Dolev, Alex Shvartsman, Jennifer Welch,
• Seth Gilbert, Sayan Mitra, Calvin Newport, Tina
  Nolte,
• Limor Lahiani, Elad Schiller,
• Matthew Brown, Mike Spindel

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Virtual Nodes

• Small computers can be equipped with sensors,
  actuators, wireless communication.
• Potentially, people, robots, vehicles, could use
  this hardware to establish mobile ad hoc
  networks, coordinate in running applications.
• Examples
• Rescue workers in disaster areas
• Soldiers in urban battle
• Robots exploring a novel location
• Cars on highway
• Set up network, use network to collect and
  process data, produce models of environment, plan
  activities.

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That would be nice, but

• Application design for ad hoc networks is hard.
• Networks change unpredictably.
• New idea for simplifying application design
• Use a Virtual Node layer
• Abstract layer containing virtual computing nodes
  that are better behaved than actual physical
  nodes.
• Program applications on top of the virtual node
  layer.

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Virtual Node Layers

• Abstraction layers containing virtual active
  nodes.
• Virtual Nodes may be associated with fixed
  geographical locations, or
• VNs may move
• Along a pre-planned path, or
  
  
• Along a path that is calculated
  dynamically.
• Program applications over
  the VN layer.

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Virtual Node Layers
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Virtual Node Layers
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Application GeoCast
Route message to a designated geographical region
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Data Management
Gather, analyze,aggregate,and distribute data.
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Region Coordination
Coordinate behavior ofnodes in region.
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Token Circulation
Circulate tokenregion by region.
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Location Tracking Service

• Support queries about current locations of
  (cooperative) PNs.
• Implement Location Tracking Service over VN
  layer
• Each PN has a Home Location
• VN that keeps track of PNs current location (VN
  region).
• Determined by hash function from PN id.
• PN keeps Home Location up-to-date by sending
  periodic messages.
• Use GeoCast (implemented over VN layer).
• Queries, responses also use GeoCast.
• For reliability, use several, redundant Home
  Locations.
• Easier than solutions using distributed hashing
  directly over physical layer.
• Use this Location Tracking Service to implement
  (easily) point-to-point message routing between
  PNs.

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Coordination Oracles

• Oracle associated with a given VN location
• Gathers and analyzes information about that
  location.
• Sends summarized information to other Oracles.
• Builds a suitable model of the environment.
• PNs query nearby Oracles and use response to help
  plan their actions.
• Use for advanced global coordination.

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Coordination Oracles

My model predicts fierce fighting here. Stay
here, take cover!
Location A
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Coordination Oracles

Location B
My model predicts quiet here. Location A needs
reinforcements. I will suggest a safe route
there.
Location A
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Application Motion Coordination

• Given curve G, and a finite, unknown set of
  physical mobile nodes (PNs), move the PNs so that
  they are (approximately) evenly spaced on G.

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Virtual Node Approach

• Divide region into zones, one VN per zone.
• VN coordinates client nodes in its zone
• Directs motion of CNs in its zone
• Towards G.
• On G, to even out spacing.
• Communicates with neighboring VSNs, sends
  extra clients to
  neighboring zones.

CN
CN
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Experimental project

• Undergrad programmers Mike Spindel, Matthew
  Brown
• PhD students Gilbert, Newport, Nolte
• Building small network of virtual nodes on a
  bunch of HP Ipaqs, equipped with 802.11 and GPS
  sensors.
• Demo applications
• Virtual traffic light
• Tracking cooperative mobile devices (using home
  location service)
• Sponsor Quanta, Inc.

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Relevance to Aero/Astro?

• Virtual Node Layer consisting of Virtual
  Air-Traffic Controllers?
• For congestion management, in free flight.