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A SensibilityBased Sleeping Configuration Protocol for Dependable Wireless Sensor Networks

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Title: A SensibilityBased Sleeping Configuration Protocol for Dependable Wireless Sensor Networks


1
A Sensibility-Based Sleeping Configuration
Protocol for Dependable Wireless Sensor Networks
  • Chen Xinyu
  • Group Meeting
  • 2005-01-28

2
Outline
  • Introduction
  • Neighboring-sensor field sensibility
  • Sensibility-based sleeping configuration protocol
  • Performance evaluations
  • Conclusions

3
Wireless Sensor Networks
  • Composed of a large number of sensor nodes
  • Sensors communicate with each other through
    short-range radio transmission
  • Sensors react to environmental events and relay
    collected data through the dynamically formed
    network

4
Applications
  • Environment monitoring
  • Military reconnaissance
  • Physical security
  • Traffic surveillance
  • Industrial and manufacturing automation
  • Distributed robotics

Ossama Younis and Sonia Fahmy Distributed
Clustering in Ad-hoc Sensor Networks A Hybrid,
Energy-Efficient Approach (InfoCom2004)
5
Requirements
  • Maintaining coverage
  • Every point in the region of interest should be
    sensed within given parameters
  • Extending system lifetime
  • The energy source is usually battery power
  • Battery recharging or replacement is undesirable
    or impossible due to the unattended nature of
    sensors and hostile sensing environments

6
Requirements (Contd)
  • Fault tolerance
  • Sensors may fail or be blocked due to physical
    damage or environmental interference
  • Produce some void areas which do not satisfy the
    coverage requirement
  • Scalability
  • High density of deployed nodes
  • Each sensor must configure its own operational
    mode adaptively based on local information, not
    on global information

7
Approach Coverage Configuration
  • Coverage configuration is a promising way to
    extend network lifetime by alternately activating
    only a subset of sensors and scheduling others to
    sleep according to some heuristic schemes while
    providing sufficient coverage in a geographic
    region

8
Concerns
  • A good coverage-preserved and fault-tolerant
    sensor configuration protocol should have the
    following characteristics
  • It should allow as many nodes as possible to turn
    their radio transceivers and sensing
    functionalities off to reduce energy consumption,
    thus extending network lifetime
  • Enough nodes must stay awake to form a connected
    network backbone and to preserve area coverage
  • Void areas produced by sensor failures and energy
    depletions should be recovered as soon as possible

9
Two Sensing Models
  • Boolean sensing model (BSM)
  • Each sensor has a certain sensing range, and can
    only detect the occurrences of events within its
    sensing range
  • General sensing model (GSM)
  • Capture the fact that signals emitted by a target
    of interest decay over the distance of
    propagation
  • Exploit the collaboration between adjacent sensors

10
Discussions for the BSM
  • Each sensor has a deterministic sensing radius
  • Allow a geometric treatment of the coverage
    problem
  • Miss the attenuation behavior of signals
  • Ignore the collaboration between adjacent sensors
    in performing area sensing and monitoring

11
Problem Formulation for the GSM
  • Point Sensibility s(Ni, p) the sensibility of a
    sensor Ni for an event occurring at an arbitrary
    measuring point p
  • ? the energy emitted by events occurring at
    point p
  • ? the decaying factor of the sensing signal
  • d(Ni, p) the distance between senosr Ni and
    point p

12
All-Sensor Field Sensibility (ASFS)
  • Suppose we have a background distribution of n
    sensors, denoted by N1, N2, , Nn, in a
    deployment region A
  • All-Sensor Field Sensibility for point p
  • With a sensibility threshold ?, the point p is
    covered if Sa(p) ?

13
Discussions for the ASFS
  • Need a sink working as a data fusion center
  • Produce a heavy network load in multi-hop sensor
    networks
  • Pose a single point of failures

14
Neighboring-Sensor Field Sensibility (NSFS)
  • Treat each sensor as a sensing fusion center
  • Each sensor broadcasts its perceived field
    sensibility
  • Each sensor only collects its one-hop neighbors
    messages
  • Transform the original global coverage decision
    problem into a local problem

15
Responsible Sensing Region (RSR)
  • Voronoi diagram
  • Partition the deployed region into a set of
    convex polygons such that all points inside a
    polygon are closet to only one particular node
  • The polygon in which sensor Ni resides is its
    Responsible Sensing Region ?i
  • If an event occurs in ?i, sensor Ni will receive
    the strongest signal
  • Open RSR and closed RSR

16
Pessimistic Scan Region
17
Connectivity Requirement
  • Considering only the coverage issue may produce
    disconnected subnetworks
  • Simple connectivity preservation
  • Evaluating whether Nis one-hop neighbors will
    remain connected through each other or through
    its two-hop neighbors when Ni is removed

18
Nis Sleeping Candidate Condition
  • Responsible Sensing Region of Nj
  • the two-hop confined region of Ni
  • communication path between Nj and Nk

19
Optimistic Scan Region
20
Sensibility-Based Sleeping Configuration Protocol
(SSCP)
ready-to- sleeping
ready-to-on
sleeping
on
21
Performance Evaluation with ns-2
  • Boolean sensing model
  • ESS extended sponsored sector
  • Proposed by Tian et. al. of Univ. of Ottawa, 2002
  • Consider only the nodes inside the RSR of the
    evaluated node
  • General sensing model
  • SscpP SSCP with the pessimistic scan region
  • SscpO SSCP with the optimistic scan region

22
Bridge between BSM and GSM
  • Ensured-sensibility radius

23
Default Parameters Setting
  • The deployed area is 50m x 50m
  • ? 1, ? 3, ? 0.001 (r 10m)
  • R 12 m
  • The number of deployed sensor 120
  • Power Consumption
  • Tx (transmit) 1.4W, Rx (receive) 1W, Idle
    0.83W, Sleeping 0.13W

24
Performance Evaluation (1)
  • Sleeping sensor vs. communication radius

25
Performance Evaluation (2)
  • Network topology

26
Performance Evaluation (3)
  • Sleeping sensor vs. sensor number

27
Performance Evaluation (4)
  • Sleeping sensor vs. sensibility threshold

28
Performance Evaluation (5)
  • Network lifetime vs. live sensor when the MTBF is
    800s, R is 12m

29
Performance Evaluation (6)
  • ?-coverage accumulated time
  • The total time during which ? or more percentage
    of the deployed area satisfies the coverage
    requirement

30
Conclusions
  • Propose NSFS with the GSM
  • transform a global decision problem to a local
    one
  • exploit the cooperation between adjacent sensors
  • Develop SSCPs to build dependable wireless sensor
    networks

31
Q A
Thank You
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