Lifetime and Coverage Guarantees Through Distributed Coordinate-Free Sensor Activation
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Lifetime and Coverage Guarantees Through Distributed Coordinate-Free Sensor Activation
ACM MOBICOM 2009
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Outline
• Introduction• Network model• Problem statement• Algorithm• Simulation• Conclusion
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Introduction
• In many of these applications, WSNs need to monitor the target field for detecting events of interest.
• The challenge is compounded by the fact that the sensors are battery-powered and owing to size limitations the sensors can only be deployed with low-lifetime batteries.
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Introduction
• To our knowledge, the only scheme that provides guarantees on the network lifetime is the one proposed by Berman et al. [11].
• This algorithm determines how to activate sensors based on an approximate solution of a linear program that requires complete knowledge – network topology– coordinates of sensor locations– initial energy of sensors
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Introduction
• Our contribution is to provide a distributed, coordinate-free sensor activation scheme that provides provable guarantees on the network lifetime.
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Network model
• A set S of n sensors• ID(u) : a unique identification number• : sensing range• :transmission range• : distance between nodes u and v• : the set of neighbors of u (TR)• : initial energy
uRur
vud ,
uN
uB
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Network model
• Assume that nodes only have localized distance information– – and for each– for each pair
• Time : time slots• Sensors have synchronized
Internal node
Periphery node
uNvuNvw ,
vrvud ,
wvd ,
uR
r̂
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The target field
• Definition 1 (The Target Field).– The target field is the area defined by the closure
of the union of the sensing ranges of all the internal sensors.
Internal node
Periphery node
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The target field
• Definition 2 (Sensor Cover). – A set C of sensors that k-covers the target field is
termed a sensor cover.
Internal node
Periphery node
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Problem statement
• Definition 3 (The Network Lifetime). – The network lifetime is the time interval from the
activation of the network until the first time at which a coverage hole appears.
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Problem statement
• Definition 4. (The Maximum Network Lifetime Problem) – An activation schedule is a sequence of sensor
covers that are activated in successive slots, such that in every slot, each sensor in the activated sensor cover has non-zero energy.
– The maximum network lifetime problem seeks to find an activation schedule that maximizes the network lifetime.
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Algorithm overview
• Distributed Lifetime Maximization (DLM)
– Every node decides whether to activate itself in the slot based only on the state information in its neighborhood.
SlotInitialization
phase
Activationphase
Beginning of the network operation Slot
Activationphase
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Algorithm
• Distributed Lifetime Maximization (DLM)– Initialization phase• The set of intersection points that it covers• The identities of the sensors in • The intersection points in that are covered by each
sensor in
u
uP
uTuP
uT
a
b
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Algorithm
• Distributed Lifetime Maximization (DLM)– Activation phase• Weight assignment
• If assigns itself a weight of
u
uu B
jbl
)(
u
jl
u Bjw
u )(
)(
The energy has been consumed in slots 1~j-1
Initial energy
Consumed fractionof its energy
1)( uu Bjb
uSu BB
nB
max
4
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Algorithm
• Distributed Lifetime Maximization (DLM)– Activation phase• Sensor activation
– Sensors that have infinite weights => sleep at slot j
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Algorithm
• Distributed Sensor Cover (DSC)
201
20,10
1
10 BA arar 25.0
20
5,5.0
10
5 BA arar
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Algorithm
• Calculation of Sp– Cosine Rule
v
u
wp1
1
1
vupvuw
uwp
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Simulation
• n sensors• initial energy of B units• sensing and transmission radii of 10 and 22• deployed uniformly at random in a 50* 50
units2 target field• Each time slot was 1 unit long
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Simulation
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Simulation
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Simulation
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Conclusion
• We designed a distributed, coordinate-free algorithm for attaining high lifetimes in sensor networks, subject to ensuring the k-coverage of the target field during the network lifetime.
• Simulation results reveal that our algorithm substantially outperforms other schemes for lifetime maximization.