Avoiding Energy Holes in Wireless
Sensor Network with Nonuniform
Node Distribution
Xiaobing Wu, Guihai Chen and Sajal K. Das
Parallel and Distributed Systems 2008
Outline

Introduction


Analysis of the Nonuniform Node Distribution
Strategy
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
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Energy Hole Problem
Impossibility of Balanced Energy Depletion
Possibility of Subbalanced Energy Depletion
Novel Nonuniform Node Distribution Strategy
and q-switch Routing
Simulation
Energy Hole Problem in Sensor
Network

Energy hole:

Unbalanced energy utilization

Sink
Some nodes deplete their power more quickly
Sink
Sink
Energy hole
Energy hole
Energy hole
Related Work

Approaches that have been proposed to mitigate
the energy hole problem



Sink mobility
Multiple sinks
Hierarchical deployment

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
Clustering
Non-uniform initial energy budgets
Non-uniform node distribution

The objective of this paper
Contributions of this paper
1.
2.
3.
4.
Prove that balanced energy utilization is
impossible for many-to-one traffic pattern.
Prove that subbalanced energy utilization
is possible
Propose a nonuniform node deployment
strategy
Propose a q-switch routing
Assumptions and Network Model
Assume that all the nodes are deployed in a circular area
with a radius R
 The width of each corona
is 1 unit length
 Maximum transmission range
is 1 unit length
 Nodes belonging to a corona
{Ci | i  R} will forward data
generated by both themselves
and nodes from coronas
{C j | i  1  j  R}

Assumptions and Network Model

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Assume that each sensor node generates and sends
L bits of data per unit time
Regular reporting
The initial energy of each sensor is 
Sending 1 bit costs e1 units of energy
Receiving 1 bit costs e2 units of energy
Energy Consumption


Ni : the number of nodes in Ci
Ei: the energy consumed per time unit
by nodes in Ci
Balanced v.s. Subbalanced
Impossibility of Balanced Energy
Depletion
Proof
If balanced energy depletion is achieved, then

Average energy consumption per node
Impossibility of Balanced Energy
Depletion
Subbalanced Energy Depletion

Proof: If the network achieves the subbalanced
energy depletion
Average energy consumption per node
Subbalanced Energy Depletion
Subbalanced Energy Depletion
the number of nodes in coronas increases in geometric
progression with a common ratio of q
Nonuniform Node Distribution
-- Subbalanced Energy Depletion
q=3
16 8
144 48
Nonuniform Node Distribution
-- Subbalanced Energy Depletion

Proof
Nonuniform Node Distribution
-- Subbalanced Energy Depletion
Nonuniform Node Distribution Strategy

The number of nodes in Ci

Subbalanced Energy Depletion
Nonuniform Node Distribution Strategy
q-Switch Routing
Simulation
Conclusion


This paper explored the theoretical aspects
of the nonuniform node distribution strategy
in WSNs.
Although it is impossible to achieve
balanced energy depletion, subbalanced
energy depletion in the network is possible.