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  1. 1. Nazia Majadi / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.1649-1652 U-LEACH: A Routing Protocol for Prolonging Lifetime of Wireless Sensor Networks Nazia Majadi Department of Computer Science and Engineering, Military Institute of Science and Technology (MIST), Dhaka, BangladeshABSTRACT A wireless sensor network is composed of Deployment in inaccessible terrains or disaster reliefa large number of sensor nodes that are densely operations. On the other hand, this also means thatdeployed in a phenomenon or very close to it. The sensor network protocols and algorithms mustlifetime of sensor nodes shows a strong possess self-organizing capabilities. Another uniquedependence on battery lifetime. Clustering feature of sensor networks is the cooperative effort ofprovides an effective way for prolonging the sensor nodes. Sensor nodes are fitted with an onboardlifetime of a wireless sensor network. Therefore, processor. Instead of sending the raw data to theClustering techniques are used to distribute the nodes responsible for the fusion, they use theirenergy consumption among nodes in each cluster processing abilities to locally carry out simpleand extend the network lifetime. LEACH (Low- computations and transmit only the required andEnergy Adaptive Clustering Hierarchy), a partially processed data. Some of the applicationclustering-based protocol that utilizes randomized areas for WSNs are health, military, and home. Inrotation of Cluster-Heads (CHs) to evenly military, for example, the rapid deployment, self-distribute the energy among the sensors in the organization, and fault tolerance characteristics ofnetwork. But LEACH cannot select CHs sensor networks make them a very promising sensinguniformly throughout the network. Therefore technique for military command, control,there is the possibility that the elected CHs will be communications, computing, intelligence,concentrated in certain area of the network. surveillance, reconnaissance, and targeting systemsHence, some nodes will not have any CHs in their [3].vicinity. The proposed approach U-LEACH is an Despite the innumerable applications ofapproach to address this problem. It describes a WSNs, these networks have several restrictions, suchuniform distribution technique that is Uniform as limited energy supply, limited computing power,Distribution Technique (UDT) for selecting CHs and limited bandwidth of the wireless linksand their corresponding clusters. The goal of this connecting sensor nodes. One of the main designpaper is to build such a wireless sensor network in goals of WSNs is to carry out data communicationwhich each sensor node remains inside the while trying to prolong the lifetime of the network andtransmission range of CHs and therefore, the prevent connectivity degradation by employinglifetime of the network is prolonged. aggressive energy management techniques. The design of routing protocols in WSNs is influenced byKeywords- Base Station (BS), Cluster Head (CH) many challenging factors. These factors must be, Energy Efficient Unequal Clustering (EEUC) overcome before efficient communication can beMechanism, Low-Energy Adaptive Clustering achieved in WSNs [2].Hierarchy (LEACH), Uniform Low-Energy In this paper, the proposed U-LEACH isAdaptive Clustering Hierarchy (U-LEACH), described which consists of a technique for selectingUniform Distribution Technique (UDT), Wireless cluster heads and their corresponding clusters that isSensor Network (WSN). Uniform Distribution Technique (UDT). The goal of this paper is to build a wireless sensor network inI. INTRODUCTION which CHs are uniformly selected base on the Recent advances in wireless remaining energy of the sensor nodes, each sensorcommunications and electronics have enabled the node remains inside the transmission range of CHsdevelopment of low-cost, low-powered and therefore, the lifetime of the network is enlarged.multifunctional sensor nodes that are small in size The rest of the paper proceeds as follows. Section IIand jointly communicate in short distances. These describes some related work on routing protocol intiny sensor nodes, which consist of sensing, data WSN. The proposed routing protocol U-LEACH isprocessing, and communicating components, discussed in Section III. The problem domain isleverage the idea of sensor networks [3]. A sensor described in Section IV. Finally, conclusion of thisnetwork is consisting of a large number of sensor study is drawn in Section V.nodes and the position of sensor nodes need not beengineered or predetermined. This allows random 1649 | P a g e
  2. 2. Nazia Majadi / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.1649-1652II.ROUTING PROTOCOL IN WSN way to transmit data to the base station In general, routing in WSNs can be divided through cluster-head, failure of the CHinto flat-based routing, hierarchical-based routing, and disappear the whole cluster. When clusterlocation-based routing depending on the network heads cooperate with each other to forwardstructure. In flat-based routing, all nodes are typically their data to the base station, the clusterassigned equal roles or functionality. In hierarchical- heads closer to the base station are burdenedbased routing, nodes will play different roles in the with heavy relay traffic and tend to die early,network. In location-based routing, sensor nodes’ leaving areas of the network uncovered andpositions are exploited to route data in the network causing network partition.[2]. The objective of the Energy-Aware Routing (iii) There is no real time transmission. As theprotocol [1] is to increase the network lifetime [2]. node senses ever changing real life data,LEACH (Low-Energy Adaptive Clustering sensed data can be changed during theHierarchy), a clustering-based protocol that utilizes transmission latency from nodes to baserandomized rotation of local cluster base stations station through cluster-head.(cluster-heads) to evenly distribute the energy loadamong the sensors in the network. LEACH useslocalized coordination to enable scalability and III. U-LEACH: A UNIFORM DISTRIBUTIONrobustness for dynamic networks, and incorporates TECHNIQUE OF CHS SELECTIONdata fusion into the routing protocol to reduce the In this paper, a routing protocol U-LEACH isamount of information that must be transmitted to the proposed which is a uniform distribution technique ofbase station [4]. CHs in LEACH Protocol in wireless sensor networks. LEACH is a self-organizing, adaptive It wisely organizes the network through consistentclustering protocol that uses randomization to distribution of clustering. LEACH Protocol works indistribute the energy load evenly among the sensors in the following steps [4]:the network. In LEACH, the nodes organize Step 1: Decide CHs and broadcast advertisement.themselves into local clusters, with one node acting as Step 2: Nodes transmit membership.the local base station or cluster-head. Sensors elect Step 3: Heads broadcast schedule.themselves to be local cluster-heads at any given time Step 4: Nodes transmit data.with a certain probability. These cluster head nodesbroadcast their status to the other sensors in the Step 5: Heads compress data and send to basenetwork. Each sensor node determines to which station.cluster it wants to belong by choosing the cluster-head Step 6: New turn begins go to Step 1.that requires the minimum communication energy. If the coverage area of each CH can beOnce all the nodes are organized into clusters, each predefined before Step 1, then the limitation ofcluster-head creates LEACH outperforms static uniform distribution of CHs can be improved. Theclustering algorithms by requiring nodes to volunteer CHs will be efficiently allocated throughout theto be high-energy cluster-heads and adapting the network. Initially all nodes are homogeneous. Thecorresponding clusters based on the nodes that choose node, which has the maximum remaining energy,to be cluster-heads at a given time. Once the cluster- advertises itself as the first CH. Then the first CHhead has all the data from the nodes in its cluster, the selects an area, no other node in that particular areacluster-head node aggregates the data and then can advertise itself as CH. After that another CH istransmits the compressed data to the base station. selected from rest of the network. In this way the whole network is divided into some predefined areas. Each area contains one CH and all the nodes in thatII. PROBLEM DOMAIN area constructs a cluster, not a single node will remain According to the existing LEACH protocol, outside these areas. Thus the CHs are uniformlythere are some drawbacks that need to be overcome: distributed throughout the network. The selection of(i) No uniform distribution techniques for coverage area for a certain CH can be determined by predetermined CHs. It also assumes that selecting a circle using an Energy-Efficient Unequal nodes always have data to send, and nodes Clustering Mechanism [4]. EEUC is a distributed located close to each other have correlated cluster heads competitive algorithm, where cluster data. It is not obvious how the number of head selection is primarily based on the residual predetermined CHs is going to be uniformly energy of each node. distributed through the network. Therefore, there is the possibility that the elected CHs will be concentrated in one part of the network; hence, some nodes will not have any CHs in their vicinity.(ii) Failure of a CH causes fail to the whole cluster. As nodes in a cluster have the only 1650 | P a g e
  3. 3. Nazia Majadi / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.1649-1652 to say, the node’s competition radius should decrease as its distance to the base station decreases. The range of competition radius in the network needs to be controlled [4]. Suppose R0comp is the maximum competition radius which is predefined. Setting Rcomp of Si as a function of its distance to the base station [4]:  d  d si , BS   0 si .Rcomp  1  c max   R comp ………..  d max  d min  (1) where dmax and dmin denote the maximum and minimum distance between sensor nodes and the base station, d(Si, BS) is the distance between Si and the Fig. 1: An overview of U-LEACH base station, c is a constant coefficient between 0 and 1. According to the equation (1), the competition radius varies from (1 - c) R0comp to R0comp. Fig. 1 gives an overview of U-LEACHprotocol, where the circles of unequal size represent Each tentative cluster head maintains a setclusters. First, several tentative cluster heads are SCH of its adjacent tentative cluster heads. Tentativeselected to compete for final cluster heads. Every head Sj is an adjacent node of Si if Sj is in Si’snode becomes a tentative cluster head with the same competition diameter or Si is in Sj’s competitionprobability T that is a predefined threshold. Other diameter [4]. Whether a tentative cluster head Si willnodes keep sleeping until the cluster head selection become a final cluster head depends on the nodes instage ends. Suppose Si becomes a tentative cluster SCH. Therefore, the proposed approach to enhance thehead. Si has a competition range Rcomp, which is a performance of LEACH protocol should pursue thefunction of its distance to the base station. If Si following sequences:becomes a cluster head at the end of the competition, CHs Selection Algorithm of U-LEACHthere will not be another cluster head Sj within Si’s Initially all nodes are homogeneous and CHi = 0 forcompetition diameter. Fig. 2 illustrates a topology of all nodes where i is the sensor node.tentative cluster heads, where the circles represent Let us suppose, number of nodes is N, queue QNdifferent competition ranges of tentative cluster heads. contains all nodes who will perform in the election and queue QE contains those nodes that are not going to perform in the election, Ei=1N of node i, t indicates time of rearrangement of CH selection. Initially all nodes are inserted into QN, QE = null Step 1: The node, which has the maximum remaining energy, advertises itself as CH. Then the CH selects an area, no other node in that particular area can advertise itself as CH. After that another CH is selected from rest of the network. In this way the whole network is divided into some predefined areas. Each area contains one CH and all the nodes in that area constructs a cluster. Thus the CHs are uniformly distributed throughout the network. Step 2: Set CHi =1 for maximum Ei of QN - QEFig. 2: The competition among tentative CHs Step 3: Push QE all nodes inside Rcomp2 where node i is the center. Node i advertises itself as CH. In Fig. 2, S1 and S2 can both be cluster heads, Go to Step 3 until QN NULL.but S3 and S4 cannot. Therefore the distribution ofcluster heads can be controlled over the network. And Step 4: Each node starts data transmission to CHsthe cluster heads closer to the base station should and CHs transmit to smaller cluster sizes because of higher energy Step 5: After t time go to step 1.consumption during the inter-cluster multihopforwarding communication. Thus more clustersshould be produced closer to the base station. That is 1651 | P a g e
  4. 4. Nazia Majadi / International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.1649-1652V. CONCLUSION Communications Magazine, 40(8), 2002, It is found that LEACH protocol fails in 102-114.some conditions where the higher energetic nodes are [2] J. N. Al-Karaki, and A. E. Kamal, Routingconcentrated, some nodes having highly probable to techniques in wireless sensor networks: Aremain outside of any CH’s vicinity will die within survey, IEEE Wireless Communications,short period. Therefore the rotation of cluster heads 11(6), 2004, 6-28.and the metric of residual energy are not sufficient to Book:balance the energy consumption across the network, [3] F. Zhao and L. J. Guibas, Wireless sensorCHs are required to be distributed uniformly networks: An information processingthroughout the network so that a single node should approach (San Francisco, CA: Elsevier,not be deducted by clusters. This paper has presented 2004).a routing protocol U-LEACH in WSN that can reduce Proceeding Paper:the problems of LEACH. As well as, a uniform [4] W. R. Heinzelman, A. Chandrakasan, and H.distribution technique of U-LEACH for selecting CHs Balakrishnan, Energy-Efficientcan not only reduce energy consumption but also Communication Protocol for Wirelessincrease nodes life time. Therefore, the network Microsensor Networks, Proc. 33rd Hawaiilifetime is prolonged. As the future work, the International Conference on Systemproposed U-LEACH protocol will be applied to Sciences, Washington DC, USA, 2000,WSNs where sensor nodes are heterogeneous. 8020-8029.REFERENCESJournal Papers: [1] I. F. Akyildiz, W. Su, Y. Sankarasubramaniam, and E. Cayirci, A survey on sensor networks, IEEE 1652 | P a g e