11-12-2012, 01:11 PM
A cluster-based routing protocol for wireless sensor networks with nonuniform node distribution
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Abstract
Due to the nonuniform node distribution, the energy consumption among nodes are more imbalanced
in cluster-based wireless sensor networks. Based on this problem, in this paper, a cluster-based routing
protocol for wireless sensor networks with nonuniform node distribution is proposed, which includes an
energy-aware clustering algorithm EADC and a cluster-based routing algorithm. EADC uses competition
range to construct clusters of even sizes. At the same time, the routing algorithm increases forwarding
tasks of the nodes in scarcely covered areas by forcing cluster heads to choose nodes with higher energy
and fewer member nodes as their next hops, and finally, achieves load balance among cluster heads.
Theoretical analysis and simulation results show that our protocol can balance the energy consumption
among nodes and increase the network lifetime significantly.
Introduction
A wireless sensor network consists of thousands of low-cost,
low-power and battery-powered sensor nodes. As sensor nodes
have limited and non-rechargeable energy resources, energy is a
very scarce resource and has to be managed carefully in order to
extend the lifetime of the sensor networks.
In recent years, researchers have done a lot of studies and
proved that clustering is an effective scheme in increasing the
scalability and lifetime of wireless sensor networks [1–4]. In clustering
schemes, there are two kinds of nodes in one cluster, one
cluster head (CH) and several cluster members (CMs). Cluster members
gather data from the environment periodically and send the
data to cluster heads. Cluster heads aggregate the data from their
cluster members, and send the aggregated data to the base station
(BS). There are two kinds of communications between cluster
heads and the BS, single-hop communication and multi-hop communication.
In multi-hop communication clustering algorithms,
the energy consumption of cluster heads consists of the energy
for receiving, aggregating and sending the data from their cluster
members (intra-cluster energy consumption) and the energy
for forwarding data for their neighbor cluster heads (inter-cluster
energy consumption).
Related works
LEACH [1] is a typical clustering protocol proposed for periodical
data gathering applications in wireless sensor networks. In
LEACH, each node independently elects itself as a cluster head with
a probability. Cluster heads receive and aggregate data from cluster
members and send the aggregated data to the BS by single-hop
communication. In order to balance the energy consumption, the
role of cluster head is periodically rotated among the nodes. LEACH
protocol is simple and does not require a large communication
overhead. However, the performance in heterogeneous networks
is not very well, because it elects cluster heads without considering
the residual energy of nodes. To solve this problem, researchers
improved LEACH and proposed some new algorithms [5–7].
EADEEG [8] is a novel distributed clustering algorithm. It elects
cluster heads based on the ratio between the average residual
energy of neighbor nodes and the residual energy of the node itself,
which can achieve a good cluster heads distribution and prolong the
network lifetime.
The authors in [9] analyzed EADEEG and proposed BPEC, a distributed
energy saving clustering algorithm. BPEC elects cluster
heads by the ratio between the average residual energy of neighbor
nodes and the residual energy of the node itself as its primary
probability and the node’s degree as its subsidiary probability. It is
proved that BPEC can avoid the “isolate points” problem in EADEEG
and keep all the cluster heads connected.
Cluster-based routing protocol
This protocol contains an energy-aware clustering algorithm
EADC and a cluster-based routing algorithm. In order to elect cluster
heads with higher energy, the parameter of cluster head competition
in EADC is based on the ratio between the average residual
energy of neighbor nodes and the residual energy of the node itself.
Moreover, cluster heads broadcast head messages using the same
competition range to construct clusters of even sizes. Thus, the
energy consumption among cluster members can be balanced well.
However, the even cluster size also makes the energy consumption
among cluster heads imbalanced, due to nonuniform distribution
of nodes. Cluster heads in dense areas have more members nodes,
so they have high intra-cluster energy consumption. For this, we
propose an inter-cluster energy-efficient multi-hop routing protocol,
in which cluster heads select the neighbor cluster head with
higher residual energy and a smaller number of cluster members
as the next hop to balance the energy consumption among cluster
heads. The description of control messages used in the process are
shown in Table 1.
Routing algorithm analysis
The value of DIST TH determines the number of cluster heads
which communicate with the BS directly. In the case that DIST TH
is smaller than the minimize distance between the BS and the
network field, there are no cluster heads communicate with the
BS. As a result that the data from the network cannot be transmitted
to the BS leading to an unavailable network. In the case
that DIST TH is larger than the minimize distance between the
BS and the network field, if DIST TH is small, the number of cluster
heads which communicate with the BS directly will be small
and the forwarding load of these nodes will be larger correspondingly.