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HHigh-igh-SSpeed peed NNetworking etworking LLab.ab.HHigh-igh-SSpeed peed NNetworking etworking LLab.ab.

On Achieving Maximum Network Lifetime On Achieving Maximum Network Lifetime Through Optimal Placement of Cluster-heads Through Optimal Placement of Cluster-heads

in Wireless Sensor Networksin Wireless Sensor Networks

High-Speed Networking Lab.High-Speed Networking Lab.Dept. of CSIE, Fu-Jen Catholic UniversityDept. of CSIE, Fu-Jen Catholic University

Adviser: Jonathan C. Lu, Ph.D.Adviser: Jonathan C. Lu, Ph.D.Speaker: Yen-Fong WangSpeaker: Yen-Fong Wang

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OutlineOutline• AbstractAbstract• IntroductionIntroduction• Related workRelated work• Optimal placement of cluster-heads (OPC) Optimal placement of cluster-heads (OPC)

algorithmalgorithm• Simulation resultsSimulation results• ConclusionConclusion• ReferenceReference

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I. Abstract

• In wireless sensor network, the network lifetime is an important issue when the size of the network is large

• The cluster-heads near the sink get overloaded and drained out sooner

• Formulate an optimization problem and find the optimum number of cluster-heads to be deployed and their optimum transmission ranges

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II. Introduction• There are two basic network architectures in WSN

– Multi-hop– Cluster-heads

• Multi-hop: The sensor nodes are homogeneous and they transmit data packets via intermediate sensor nodes in a multi-hop fashion to the sink

• Cluster heads: The whole area is divided into a number of cluster regions

• Cluster-heads reduce the number of transmissions by aggregating the sensed information thereby minimizing the energy dissipation in the network

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III. Related work

• The lifetime of the sensor nodes is balanced by varying the radio’s transmission range

• Sensor nodes reach the cluster-head station using– Single-hop mode– Multi-hop mode– Hybrid communication mode

• The cluster-heads– Gather the sensed information from sensor nodes– Perform the required computation– Have long transmission range than that of the sensor nodes

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IV. OPC Algorithm• Places additional cluster-heads near the sink to handle the

high load

• Provides the optimum density and radio transmission range for the cluster-heads in order to achieve the maximum network lifetime with the minimum network cost

• Network model– The network is divided into number of clusters– Cluster-heads transmit packets to the data sink in a multi-hop path via

other cluster-heads– Sensor nodes communicate with their cluster-heads either in a single or

multi-hop path

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IV. Cluster architecture in wireless sensor network

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IV. OPC Algorithm

• Relationship between node density and transmission range–

• Optimum number of cluster-heads problem is non linear integer programming problem (NLP)

Joules102.7Energy 114 TxRange

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IV. OPC Algorithm

• Varying dense placement algorithm– The cluster-heads near the sink will run out of power sooner

and reduce the network lifetime

• Minimum number of cluster-heads required

: the minimum number of cluster-heads requiredr : the transmission range for cluster-heads

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IV. Varying dense placement of cluster-heads

R1

2

3

45

6

r

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IV. OPC Algorithm

• Cluster-heads can reduce the transmission range, in order to save energy

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IV. OPC Algorithm

• The hop distance between the sink and the border cluster-heads is N, where

• The objective is to minimize the network cost is

K: the number of packets transmitted by a cluster-heads after collecting the data from

sensor nodes

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V. Simulation results

• Use GloMoSim simulator to simulate the results

• Compared uniform dense placement (UDP), varying dense placement (VDP) and OPC algorithms in the network lifetime, collisions and latency

• Simulation parameters– Network size (Terrain radius): 1000 – 2000 meters– Bandwidth: 48 kbps– Packet size 512 bytes– Transmission range (UDP/VDP): 200 meters– Transmission range (OPC): 80-200 meters– MAC protocol: IEEE 8.2.11 DCF

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V. Network lifetime for different network sizes

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V. Effect of varying traffic on collisions

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V. Effect of varying traffic on latency

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VI. Conclusion

• The optimum number if cluster-heads required and their respective transmission ranges

• This paper’s algorithm achieves the maximum network lifetime with the minimum network cost and less number of collisions

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VII. Reference

• On Achieving Maximum Network Lifetime Through Optimal Placement of Cluster-heads in Wireless Sensor NetworksDhanaraj, M.; Siva Ram Murthy, C.;IEEE International Conference on Communications, 2007. ICC `07.

24-28 June 2007

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