2007 International Conference on Sensor Technologies and Applications
Improvement on LEACH Protocol of Wireless Sensor Network
Fan Xiangning1,2 Song Yulin2
1 Institute of RF-&-OE-ICs, School of Information Science and Engineering, Southeast
University, Nanjing, 210096, China
2 National Mobile Communications Research Laboratory, Southeast University, Nanjing,
210096, China
xnfan@seu.edu.cn
Abstract paper, two simple performance matrixes are given, and
a new modified energy-LEACH protocol is presented
This paper studies LEACH protocol, and puts which designs in detail and improves the protocol of
forward energy-LEACH and multihop-LEACH paper [6]. Multi-hop protocol is studied in paper [7],
protocols. Energy-LEACH protocol improves the but it is quite complex. Our paper further presents a
choice method of the cluster head, makes some nodes multihop-LEACH protocol which is simple, has great
which have more residual energy as cluster heads in performance and is especially fit for WSN with
next round. Multihop-LEACH protocol improves restrictive energy.
communication mode from single hop to multi-hop
between cluster head and sink. Simulation results show 2. LEACH protocol
that energy-LEACH and multihop-LEACH protocols
have better performance than LEACH protocols. Main techniques of LEACH protocol include
algorithms for distributing cluster forming, adaptive
1. Introduction cluster forming, and cluster header position changing.
The technique of distributing cluster forming ensures
Wireless sensor network (WSN) consists of a self-organization of most target nodes. The adaptive
certain number of smart sensors which form a multi- cluster forming and cluster header position changing
hop Ad Hoc network by radio communications in algorithms ensure to share the energy dissipation fairly
sensor field. It aims to apperceive in collaborative among all nodes and prolong the lifetime of the whole
mode, gather ， deal with and send information to system in the end.
observer in network areas. Sensor, sensing object and
observer form the three factors in WSN[1][2][3]. WSN 2.1. Description of LEACH protocol
protocol stack contains physical layer, data link layer,
network layer, transport layer and application layer[4]. LEACH protocol provides a conception of round.
According to network architecture, routing protocols LEACH protocol runs with many rounds. Each round
are generally classified as plane routing, grade routing, contains two states: cluster setup state and steady state.
and position routing. In cluster setup state, it forms cluster in self-adaptive
LEACH (Lower Energy Adaptive Clustering mode; in steady state, it transfers data. The time of
Hierarchy) protocol is a grade routing protocol. Paper second state is usually longer than the time of first state
[1] and [5] introduce LEACH protocols in detail. Paper for saving the protocol payload. Figure 1 shows the
[6] presents a modified protocol, but it is still faulty process.
and the performance matrixes are complex. In this
Figure 1. Operation time of LEACH
0-7695-2988-7/07 $25.00 © 2007 IEEE 260
DOI 10.1109/SENSORCOMM.2007.21
The flow chart of LEACH protocol is shown in The flow chart of different processes for these two
figure 2. kinds of node is shown in figure 4.
Figure 4. Different processes of nodes in LEACH
protocol
2.2. Discussion of LEACH protocol
Two ideas of LEACH protocol improvement are
given in this paper. Details of improvement will be
presented in the following two sub-sections.
Figure 2. Flow chart of LEACH protocol
(1) The criterion of selecting cluster head node
The flow chart of cluster selection is shown in figure 3. LEACH protocol randomly selects cluster head at
each round. Therefore, some nodes maybe exhaust
energy too quickly due to being selected as cluster
head many times. In this paper, our modified protocol
makes the nodes with more residual energy have more
chance as cluster head and this will prevent the whole
network to die too early.
(2) Multi-hop communication among cluster heads
Cluster heads directly communicate with sink in
LEACH protocol. The energy consumption between
cluster head and sink are greater than energy
consumption among cluster heads, so the cluster head
will exhaust energy soon. Multi-hop communication
can avoid the whole network from dying quickly and
prolong the network lifetime by balancing the energy
consumption among the network.
2.3. Energy-LEACH protocol
Our energy-LEACH protocol improves the cluster
head selection procedure. It makes residual energy of
node as the main matrix which decides whether these
Figure 3. Cluster formation of LEACH protocol nodes turn into cluster head or not in the next round. In
first round communication, every node has the same
probability to turn into cluster head. n (n=p×N) nodes
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are randomly selected as cluster heads, and then, the 2.4. Multihop-LEACH protocol
residual energy of each node is different after one
round communication. We select n nodes with more Each cluster head directly communicates with sink
residual energy as cluster heads in next round no matter the distance between cluster head and sink is
communication, and so on until all nodes are dead. far or near in LEACH protocol. It will consume lot of
Same as the LEACH protocol, energy-LEACH energy if the distance is far. A further modified
protocol also divides into many rounds, and each round LEACH protocol (denoted as multihop-LEACH
contains cluster formation phase and cluster steady protocol) which selects optimal path and adopts multi-
phase. hop between cluster head and sink is presented here.
(1) In cluster formation phase, each node decides First, multi-hop communication is adopted among
whether to turn into cluster head or not by comparing cluster heads. Then, according to the selected optimal
with residual energy； path, these cluster heads transmit data to the
(2) Some nodes with more residual energy turn into corresponding cluster head which is nearest to sink.
cluster heads and send cluster head information to Finally, this cluster head sends data to sink.
inform other nodes. The other nodes with less residual Multihop-LEACH protocol is almost the same as
energy turn into common nodes, and send information LEACH protocol, only makes communication mode
about joining cluster to a cluster head； from single hop to multi-hop between cluster heads
(3 ) In cluster steady phase, nodes in a cluster send and sink. Its multi-hop routing algorithm within one
data according to TDMA table, and cluster heads round is shown in figure 6.
receive, fuse and send data to sink. After a period of
time, the network reforms the cluster head selection
procedure in a new round.
In cluster formation phase, the flow chart of
whether a node turns into cluster head or a common
node is shown in figure 5.
Figure 6. Routing of multihop-LEACH protocol
3. Simulation analysis
Performances of LEACH protocol, energy-LEACH
protocol and multihop-LEACH protocol are simulated
and compared in this section.
3.1. Performance matrixes
Network lifetime of WSN is very important due to
restricting energy. Here, two matrixes are given to
show the state of network energy consumption.
(1) Residual energy of all node;
(2) Time of network death for different number of
nodes.
In our simulation, matrix (1) shows all residual
Figure 5. Flow chart of energy-LEACH protocol
energy of 100 node, and matrix (2) is the time when
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the whole network is finally dead under the condition in this paper. Energy-LEACH protocol considers
of a given number of node. residual energy in the phase of cluster head selection.
Multihop-LEACH protocol adopts multi-hop
3.2. Simulation parameters setting communication between cluster and sink. Simulation
results show that energy-LEACH and multihop-
(1) Sensor nodes contain two kinds of nodes: sink LEACH protocols have better performance than
nodes (no energy restriction) and common nodes (with LEACH protocol.
energy restriction);
(2) Nodes are randomly distributed in a area within Energy consuption of three protocols
80m×80m, and the efficient distance among nodes is
1000
15m; 900
(3) Suppose that every node knows its position, 800
channels between sensor nodes are ideal, sending 700
LEACH
energy__LEACH
energy consumption is the same as receiving energy multihop__LEACH
Residual energy(J)
consumption, energy consumption in each round is 600
0.05J, and initial energy of each node is 10J; 500
(4) Energy consumption between cluster head and 400
sink is 59 times of the energy consumption among
common nodes;
300
(5) Probability of being cluster head equals 0.04; 200
(6) Each node sends data in every 0.5s, and sends 100
data in every time interval at a random time by a
TDMA slotted MAC (Medium Access Control)
0
0 20 40 60 80 100 120 140 160 180 200
Time(s)
protocol;
(7) Network with same number of nodes still may Figure 7. Residual energy of three protocols with
have different performance due to network structure. In 100 nodes
our simulation, the network topology is randomly built
each time, and simulation results are averaged for 3 Time of network death for different number of nodes
different network topologies.
160
LEACH
155
energy__LEACH
3.3. Simulation results
multihop__LEACH
150
Time of network death(s)
Figure 7 shows the performance of residual energy 145
of LEACH protocol, our energy-LEACH protocol and 140
multihop-LEACH protocol. Multihop-LEACH
protocol has more residual energy than LEACH and 135
energy-LEACH protocols. Energy-LEACH protocol 130
has the same residual energy as LEACH protocol in
the beginning, but Energy-LEACH protocol gradually
125
has more residual energy than LEACH protocol after a 120
certain period of time (120s for our simulation).
Figure 8 shows the performance of network death
115
20 30 40 50 60 70 80 90 100
Node numbers
time for different number of nodes. Multihop-LEACH
protocol survives longer than both energy-LEACH Figure 8. Time of network death in different num of
protocol and LEACH protocol, and Energy-LEACH node of three protocols
protocol longer than LEACH protocol. The results
show that our two modified protocols prolong the
network lifetime as compared with the commonly used 5. Acknowledgement
LEACH protocol.
This paper is supported by the National High
4. Conclusion Technology Research and Development Program of
China (863 Program) No.2007AA01Z2A7.
Two modified LEACH protocols: energy-LEACH
protocol and multihop-LEACH protocol are presented
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6. References 2002.
[5] W. Heinzelman, A. Chandrakasan, and H.
[1] Sun Limin, Li Jianzhong, Chen Yu, Wireless Balakrishnan, “Energy-eficient Communication
Sensor Networks, Tsinghua publishing company, Protocol for Wireless Sensor Networks”,
Beijing, 2005. Proceeding of the Hawaii International
[2] I. F. Akyildiz, W. Su, Y. Sankarasubramaniam, “A Conference on System Sciences, Hawaii, January
Survey on Sensor Networks”, IEEE 2000.
Communications Magazine, 2002, 40(8), pp.102- [6] Wang Wei, “Study on Low Energy Grade Routing
114 Protocols of Wireless Sensor Networks”,
[3] G. J. Pottie, W. J. Kaiser, “Embedding the Internet: Dissertation, Hang Zhou, Zhe Jiang
Wireless Intergrated Network Sensors”, university,2006.
Communications of the ACM, 2000, 43(5), pp.51- [7] Mo Xiaoyan, “Study and Design on Cluster
58. Routing Protocols of Wireless Sensor Networks”,
[4] D. Estrin, “Tutorial Wireless Sensor Networks- Dissertation, Hang Zhou, Zhe Jiang
Part IV: Sensor Network Protocols”, MobiCom, university,2006.
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