Title: A SensibilityBased Sleeping Configuration Protocol for Dependable Wireless Sensor Networks
1A Sensibility-Based Sleeping Configuration
Protocol for Dependable Wireless Sensor Networks
- Chen Xinyu
- Group Meeting
- 2005-01-28
2Outline
- Introduction
- Neighboring-sensor field sensibility
- Sensibility-based sleeping configuration protocol
- Performance evaluations
- Conclusions
3Wireless 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
4Applications
- 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)
5Requirements
- 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
6Requirements (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
7Approach 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
8Concerns
- 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
9Two 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
10Discussions 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
11Problem 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
12All-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) ?
13Discussions 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
14Neighboring-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
15Responsible 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
16Pessimistic Scan Region
17Connectivity 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
18Nis Sleeping Candidate Condition
- Responsible Sensing Region of Nj
- the two-hop confined region of Ni
- communication path between Nj and Nk
19Optimistic Scan Region
20Sensibility-Based Sleeping Configuration Protocol
(SSCP)
ready-to- sleeping
ready-to-on
sleeping
on
21Performance 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
22Bridge between BSM and GSM
- Ensured-sensibility radius
23Default 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
24Performance Evaluation (1)
- Sleeping sensor vs. communication radius
25Performance Evaluation (2)
26Performance Evaluation (3)
- Sleeping sensor vs. sensor number
27Performance Evaluation (4)
- Sleeping sensor vs. sensibility threshold
28Performance Evaluation (5)
- Network lifetime vs. live sensor when the MTBF is
800s, R is 12m
29Performance Evaluation (6)
- ?-coverage accumulated time
- The total time during which ? or more percentage
of the deployed area satisfies the coverage
requirement
30Conclusions
- 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
31Q A
Thank You