Research overview

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Research overview

• Murat Demirbas
• SUNY Buffalo
• CSE Dept.

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Personal computing ?

• PC processors are only 2 of all processors
• Where do the rest of the processors go?
• Automotive industry, e.g., new car has dozens of
  microprocessors
• Communications, e.g., cell-phones
• Consumer electronics, e.g., microwaves, washing
  machines
• Industrial equipment, e.g., factory floor robots

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Ubiquitous computing !

• Instead of us interacting with the computers in
  the virtual world, the computers should interact
  with us in our physical world
• Technology is now available via MEMS, CMOS, CMOS
  radios
• Real-world deployments have already started
• Environmental monitoring
• Precision agriculture
• Asset management
• Military surveillance

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Wireless sensor networks (WSNs)

• A sensor node (mote)
• 8K RAM, 4Mhz processor
• magnetism, heat, sound, vibration, infrared
• wireless (radio broadcast) communication up to
  100 feet
• costs 10 (right now costs 100)

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Challenges in WSN

• Scalability
• Thousands of nodes collaborate for achieving
  scalability distributed local algorithms are
  needed
• Distributed algorithms are notoriously difficult
  to design
• Fault-tolerance
• Wireless communication is unreliable due to
  collisions
• Consensus is impossible to achieve
• Nodes fail due to adverse environmental
  conditions and software bugs
• Maintenance of infrastructures are costly and
  difficult

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Research statement

• Developing distributed, robust, resilient WSN
  services
• Distributed decentralized
• Robust strong, durable
• Resilient able to adapt and recover from hazards
• This requires work on several layers of the WSN
  protocol stack

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Research overview

1. MAC layers for robust single-hop communication
2. Geometric infrastructures for resilient WSN
   services
3. Programming abstractions for robust computing
4. Real-world deployments of robust WSN
5. Theory of self-stabilization

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1. MAC layers for robust communication

• Coordinated attack problem
• Two armies are waiting to attack a city
• They need to attack together to win
• Each army coordinates with a messenger
• Messenger may be captured by the city
• Can generals reach agreement?
• Agreement is impossible in the presence of
  unreliable channel
• Wireless communication is unreliable due to
  collisions
• Hidden node problem

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Receiver-side collision detection (RCD)

• RCD circumvents the impossibility result
• RCD enables coping with undetectable message loss
• RCD is easily implementable in WSNs
• Receiver side monitoring and notification of
  collisions
• No info wrt of lost messages or identities of
  senders
• Classification of RCDs
• Completeness Ability to detect collisions
• Accuracy Ability to avoid false positives
• Synchronized rounds to convey negative feedback
• Collisions of negative feedback imply at least
  one negative feedback

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Vote-Veto algorithm

• Two phases vote and veto
• Vote phase
• Every active node sends out its vote
• If a node hears no collision, the node updates
  its vote to min of received votes
• If a node hears collision or different votes, it
  decides to veto
• Veto phase
• If no veto messages are received or collisions
  detected, then a node can decide, else nodes
  continue to next round
• Intuition By having a dedicated veto phase,
  effects of collision is detectable
• Robcast and BEMA MAC protocols for robust
  broadcast
• They eliminate the hidden terminal problem and
  improve throughput

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2. Geometric infrastructures for resilient WSN
services

• For scalability, local operations are needed over
  global structures
• By exploiting the geometry of WSNs, we can design
  efficient, minimal, and resilient infrastructures
  
• Querying structures Glance, DQT, PeeR-tree
• O(d) time for querying, where d is the distance
  to the nearest answer
• Graceful resilience to the face node failures via
  simplicity of design
• Tracking structures Stalk, Trail
• O(d) time for querying
• O(mlogm) for update, where m is the distance the
  evader moved
• Local self-healing via containment wave idea
  stretch-factor idea

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Geometric infrastructures for mobile WSN

• Mobility improves coverage and, hence,
  resilience
• Mobile base-station for efficient data
  aggregation
• Relocating the base-station in response to
  varying data rates
• Deployment and relocation of mobile WSN
• Sensor nodes relocate to provide dynamic coverage
  by following the interest gradient
• Even though neighbors can change for each node,
  the network should stay connected
• What are local rules to maintain such a mobile
  WSN ?

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3. Programming abstractions for robust computing

• Transact A transactional framework for
  programming WSANs
• Effectively managing concurrent execution is a
  big challenge
• Concurrency needs to be tamed to prevent
  unintentional nondeterministic executions
• Concurrency needs to be boosted for achieving
  timeliness
• Transactional, optimistic concurrency control
  framework
• enables understanding of a system execution as a
  single thread of control,
• while permitting the deployment of actual
  execution over multiple threads distributed on
  several nodes
• By exploiting the properties of wireless
  broadcast communication, we provide a distributed
  and local conflict detection and serializability

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4. Real-world deployments of robust WSN

• Line In The Sand
• In OSU, we developed a surveillance service for
  DARPA-NEST
• Detect, track, and classify trespassers as car,
  soldier, civilian
• LiteS 100 nodes in 2003, ExScal 1000 nodes in
  Dec 2004

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4. Real-world deployments of robust WSN

• INSIGHT INternet Sensor InteGration for HabitaT
  monitoring
• Single-hop network
• Basestation serves webpage
• To circumvent firewall a replica is established
  via XML query
• http//insight.podzone.net
• Elvis In-building personnel localization

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5. Theory of self-stabilization

• Self-stabilization is the ability of a system to
  recover within bounded steps from arbitrary
  states to states from where the system exhibits
  desired behavior
• Arbitrary state corruption provides a clean
  abstraction of how many systems are perturbed by
  their diverse environments
• Self-stabilization provides a viable method to
  deal with state corruption
• Case-by-case analysis of faults and recovery is
  shunned in favor of a uniform mechanism
• Self-stabilizing systems do not need any
  initialization
• Self-configuring!

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5. Theory of self-stabilization
legitimate states from where safety and
liveness are satisfied
illegitimate states reached possibly due to
faults

• Closure Set of legitimate states is closed
  under system execution
• Convergence Starting from any system state,
  every system
• computation eventually
  reaches a legitimate state

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5. Theory of self-stabilization

• Graybox self-stabilization
• Improves over the whitebox and blackbox
  approaches tried so far
• Compositional reasoning for self-stabilization
• Modular design and verification of
  self-stabilization
• Syntax-based design of self-stabilization
• Use programming patterns to achieve
  self-stabilization
• Probabilistic model-based verification of
  self-stabilization
• Improves over strictly deterministic design and
  verification of self-stabilization

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Research group

• Current PhD students
• Muzammil Hussain
• Xuming Lu
• Dola Saha
• Onur Soysal
• Several MS students are involved (via CSE 646)
• Closely related research groups
• Chunming Qiao networking
• Jan Chomicki, Michalis Petropoulos database
  management

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Questions ?

1. MAC layers for robust single-hop communication
2. Geometric infrastructures for resilient WSN
   services
3. Programming abstractions for robust computing
4. Real-world deployments of robust WSN
5. Theory of self-stabilization

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3. Abstractions for robust computing

• Virtual Infrastructure (VI)
• Robustness in spite of mobility of nodes
• Static or mobile virtual nodes
• Applications in traffic monitoring,
• and regulation (MITs CarTel platform)