A ContextAware Middleware for Applications in Mobile Ad Hoc Environments

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A Context-Aware Middleware for Applications in
Mobile AdHoc Environments
Sørensen. C.F ,Sivaharan. T, Blair. G.S, Friday.
A, Wu. M, Duran-Limon. H, Okanda. P,.

• Computing Department,
• Lancaster University, UK

MPAC Workshop _at_Middleware 2004 ,Toronto ,18th
October 2004
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Overview of Presentation

• Introduction
• Cooperating Sentient Vehicle Application Scenario
• Challenges
• Middleware Architecture
• Sentient Vehicle Test Bed
• Demo
• Conclusions

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Introduction(2)

• EU FET Project CORTEX
• Universidade de Lisboa (Portugal)
• Lancaster University (United Kingdom)
• Trinity College (Ireland)
• Universität Ulm (Germany)
• Middleware support for constructing distributed
  mobile proactive applications based on real-time
  sentient objects
• Proposes sentient object model to support the
  construction of mobile, context aware,
  decentralised ,autonomus ,proactive and
  collaborative applications such as intelligent
  vehicles and smart buildings.
• Cooperating sentient vehicles is a key
  demonstrator of the project

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Introduction(3)

• Sentient Object Model
• System consists of environment and a set of
  sentient objects
• Sentient objects are capable of independently
  sensing the environment, derive context and infer
  autonomous actions
• Sentinet objects communicate using event
  channels to establish higher level context and
  thus cooperate with each other

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Cooperating Sentient Vehicle Application Scenario

• Two Sub problems
• Cooperative behaviour without human control
• Autonomous vehicle navigation from a given source
  to pre-determined destination
• Vehicles Objectives
• Travel along a given path( virtual circuit-VC)
  defined by set of GPS waypoints and bearings.
• Every vehicle that travels on the VC cooperate
  with other vehicles to avoid collisions and
  travel safely
• Obey external roadside traffic lights.
• Give way to pedestrians who cross the road.

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Research Challenges

• Communication Model
• Routing Protocol
• Context Awareness
• End-to-End QoS and Fail safety

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Component Framework based Middleware Platform

• Middleware is engineered as family of Component
  frameworks (CF) using Reflection and component
  technology
• Each CF addresses specific research areas
• Component Frameworks are highly configurable and
  dynamically reconfigurable (with the granularity
  of a component)
• Clear separation of concerns
• Adaptable to diversity of CORTEX applications
• CFs are implemented using Lancasters OpenCOM
  reflective component technology

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Middleware Architecture
Sentient Objects
Sentient Objects
Context CF- Sensor Fusion Inference Engine
M I D D L E W A R E
Programming Interfaces
Publish-Subscribe CF- (for MANET)
Timely Computing Base
Group Communication CF-( Ad-hoc Multicast )
Payload Channel
TCB control channel
WLAN 802.11b (ad-hoc), Windows CE
Middleware Configuration for MANET
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Communication model-Publish-Subscribe CF(1)

• Implicit event model
• Sender receiver based event filtering
• Subscription Language supports subject, content
  context based event filtering
• Supports distance based context filtering
  extensible to other contexts
• XML based generic events
• Events transported via selectable Multicast
  protocol

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Publish-Subscribe CF(3)
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Routing Protocol-Multicast CF

• A Multicast service is of vital importance to the
  CORTEX environment. Sentient objects need m-to-n
  event communication in a reliable manner.
• We offer this service in the form of a component
  framework.

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Context Awareness-Context Component Framework
(CF)

• The Sentient Vehicles require higher level
  context information such as relative location,
  orientation, status , event channel QoS etc w.r.t
  entities in its proximity in real time to
  autonomously decide its speed and steer control
  actuations.
• Fundamental challenge is constructing exact
  image (perception) of the surrounding
  environments in real time

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Context CF (1)

• Sensor capture and fusion
• Multivariate Gaussian modelling
• Bayesian networks
• Dead-reckoning
• Inference engine
• A program that reasons about a set of rules (a
  knowledge base) in order to derive an output.
• The knowledge is encoded as a set of production
  rules, contexts are represented as fact.
• CLIPS C Language Integrated Production System,
  its internal implementation is based on RETE net.

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Context Component Framework (CF)(1)

• Obstacle Sensing Service Consumes raw
  ultrasonic sensor data and fuses using a suitable
  algorithm (reliable, timely-unreliable, Gaussian,
  ) to derive higher level obstacle distance
  context such as NEAR , FAR , NOOBJECT.

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Cooperating Sentient Vehicles location
Satellites
Car publishes on Carcontrol channel Event
Packet ltcar status, Locationgt
Car publishes on Carcontrol channel Event
Packet ltcar status, Locationgt
Car subscribes to CarControlChannel Receives
events from other cars
Car subscribes to CarControlChannel Receives
events from other cars
IEEE 802.11b(ad-hoc) ---Event Channel---CarControl
Channel
Car A
Car B
4m
OC CLOSE( 4m)
OC BEHIND
OC FAR(4- 10m)
OC VERY FAR
OC BEHIND
OC CLOSE
Other Cars location context w.r.t Car B
Other cars location context w.r.t car A
OC Other car
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• Car Sentient Object and Context CF

Speed Actuator
Ultrasonic sensor
Steer Actuator
GPS sensor
Consume
Produce
Sentient object
Sentient object
Digital Compass sensor
Interface
receptacle
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End-to-End QoS Management and Fail Safety-
Timeliness requirement

• Sentient Vehicles must take action based on
  up-to-date representations of the environment
• How can this be achieved?
• Enforcing timely perceptions of the environment
  and timely actuations on it.
• Which means timely event delivery and awareness
  of QoS of the event channels used for
  inter-vehicle communication
• The key issue in uncertain and highly dynamic
  environments is that timing bounds for
  distributed actions may be violated because of
  timing failure

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End-to-End QoS Management and Fail
Safety-Timeliness Requirements

• We model the uncertainty of timely event
  dissemination via event channels using a
  dependable timing failure detection service.
• This service is provided by University of
  Lisboas Timely Computing Base (TCB)
• TCB facilitates to construct distributed event
  channels with timing bound specification
• This enables publisher or subscriber to be aware
  of the timing failures of event channels
• Thus providing awareness of timing failure
  probability for a given required coverage
• Fail safety is achieved by switching the vehicles
  to fail-safe state as soon as QoS specifications
  are violated.

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Sentient Vehicle Test Bed
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Contd
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Contd
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• Demo Settings

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Waypoint 3
Waypoint 2
Traffic Light
Waypoint 4
Waypoint 1
Virtual Circuit
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Demo Video
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Concluding Remarks

• The sentient object model
• has proved to be an excellent programming
  abstraction for the development of real-time,
  cooperative, context-aware applications.
• The component-Framework based Middleware approach
• offers benefits of flexible configuration and
  reconfiguration of the middleware components
• The middleware architecture
• also provides the management of non-functional
  concerns such as timeliness and reliability
  properties.
• Our middleware is reusable
• we are keen to investigate the generality of our
  approach by applying our middleware to other
  application domains involving embedded autonomous
  components.

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Thank You

• Questions