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  1. 1. Mr. Rajesh Halke, Mrs. Kulkarni V. A./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2099-2102 En - LEACH Routing Protocol For Wireless Sensor Network Mr. Rajesh Halke1, Mrs. Kulkarni V. A.2 Dept. of Electronics Dept. of ElectronicsJ.N.E.C.A’BAD J.N.E.C.’BADABSTRACT A wireless network consisting of a large networks which is adaptable to non-uniform andnumber of small sensors with low-power dynamic energy distribution among The objective oftransceivers can be an effective tool for gathering this paper is to arrive at an energy-efficientdata in a variety of environments like civil and communication protocol for sensor networks which ismilitary applications. The data collected by each adaptable to non-uniform and dynamic energysensor is communicated through the network to a distribution among the sensor nodes and the changingsingle processing center called base station that network configurations.uses all reported data to determine characteristicsof the environment or detect an event. The Challengecommunication or message passing process must It is important that microsensor networks bebe designed to conserve the limited energy easily deployable, possibly in remote or dangerousresources of the sensors. environments. This requires that the nodes be able to Leach Is Clustering based protocol that communicate with each other even in the absence ofutilizes randomized rotation of local cluster-heads an established network infrastructure. In addition,to evenly distribute the energy load among the there are no guarantees about the locations of thesensors in the network. LEACH (Low-Energy sensors, such as the uniformity of placement. EventsAdaptive Clustering Hierarchy) uses localized occurring in the environment being sensed may becoordination to enable scalability and robustness time-sensitive. Therefore, it is often important to bindfor dynamic networks, andincorporates data the end-to-end latency of data dissemination.fusion into the routing protocol to reduce the Protocols should therefore minimize overhead andamount of information that must be transferred to extraneous data transfers. In a microsensor network,the base station. But LEACH is based on the data sensed by each node are required at a remoteassumption that each sensor nodes contain equal base station, rather than at other nodes, and the dataamount of energy which is not valid in real are being extracted from the environment, leading toscenarios. large amounts of correlation among data signals. Therefore, the notion of quality in a microsensorINTRODUCTION network is very different. For sensor networks, the The emerging field of wireless sensor end-user does not require all the data in the networknetworks combines sensing, computation, and because (1) the data from neighboring nodes arecommunication into a single tiny device. The power highly correlated, making the data redundant, and (2)of wireless sensor networks lies in the ability to the end-user cares about a higher-level description ofdeploy large numbers of tiny nodes that assemble and events occurring in the environment the nodes areconfigure themselves. Usage scenarios for these monitoring.devices range from real-time tracking, to monitoringof environmental conditions, to ubiquitous computing LEACH INTRODUCTIONenvironments, to monitor the health of structures or Wireless micro-sensor networks will enableequipment. Wireless sensor networks have the ability reliable monitoring of remote areas. These networksto dynamically adapt to changing environments. are essentially data-gathering networks where theHundreds of nodes scattered throughout a field data are highly correlated and the end-user requires aassemble together, establish a routing topology, and high-level description of the environment the nodestransmit data back to a collection point. The are sensing. In addition, these networks require easeapplication demands for robust, scalable, low-cost of deployment, long system lifetime, and low-latencyand easy to deploy networks are perfectly met by a data transfers. The limited battery capacity of micro-wireless sensor network. If one of the nodes should sensor nodes and the large amount of data that eachfail, a new topology would be selected and the node may produce translates to the need for highoverall network would continue to deliver data [1, 2, application-perceived performance at a minimum3, 4] cost, in terms of energy and latency. The application that typical microsensorOBJECTIVE networks support is the remote monitoring of an The objective of this paper is to arrive at an environment. Individual nodes data are correlated inenergy-efficient communication protocol for sensor a microsensor network, the end-user does not require 2099 | P a g e
  2. 2. Mr. Rajesh Halke, Mrs. Kulkarni V. A./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2099-2102all the (redundant) data; rather, the end-user needs a energies and avoids the inefficiencies associated withhigh-level function of the data data replication. NEW PROPOSALS TO ENHANCE THE LEACH PROTOCOL The modifications and enhancements to the LEACH protocol as follows 2.1. Changes Proposed in Cluster Setup Phase to handle Non-Uniform Energy Distribution In LEACH, probability of becoming a cluster-head is based on the assumption that all nodesFigure 1-1: The LEACH protocol for microsensor start with an equal amount of energy, and that allnetworks. nodes have data to send during each frame. If nodes LEACH includes adaptive, self-configuring begin with different amounts of energy, the nodescluster formation, localized control for data transfers, with more energy should be cluster-heads more oftenlow-energy media access, and application-specific than the nodes with less energy, in order to ensuredata processing. that all nodes die at approximately the same time. In LEACH, the nodes organize themselvesinto local clusters, with one node acting as the 2.2. Changes proposed in Data Transmissioncluster-head. All non-cluster-head nodes must Phasetransmit their data to the cluster-head, while the Since failure of cluster-head is a bigcluster-head node must receive data from all the problem in LEACH protocol and chances of itscluster members, perform data aggregation failure are more in data transmission phase, becausefunctions on the data, and transmit data to the remote this phase involves more energy dissipationbase station. Therefore, being a cluster-head node is compared to other phases in LEACH. So a methodmuch more energy-intensive than being a non- should be evolved where failure of cluster-head cancluster-head node. In the scenario where all nodes are be conveyed to its cluster members, which will helpenergy-limited, if the cluster-heads were chosen a in saving a lot of energy of its cluster members.priori and fixed throughout the system lifetime, as ina static clustering algorithm, the cluster-head sensor En-LEACH INTRODUCTIONnodes would quickly use up their limited energy. ENHANCED-LEACH (En-LEACH)Once the cluster-head runs out of energy, it is no protocol as the enhancements and innovationslonger operational. devised in thisprotocol has following objectives:  To handle cluster-head failure  To account for the non-uniform and dynamic residual energy of the nodes Protocol rounds are repeated with a periodicity Tr,Figure 1-2: Time-line showing LEACH operation. with each round consisting of the following phases.ADVANTAGES OF THE LEACH 3.1.1. Advertisement PhasePROTOCOL The first round (i.e. round number zero) is There are strong motivations behind started by each node calculating Threshold value (orselecting the LEACH as a baseline for our target En- probability to become cluster-head) using sameLEACH protocol are: method as used in LEACH protocol and comparing The LEACH protocol assumes all the nodes the threshold value with random no (0 to 1) selectedto be similar in their capabilities and doesn’t require by the node. If the threshold value is greater than thethe cluster head nodes to be more efficient than the random number chosen then the node becomes theothers in any respect. cluster-head for this round. Hence the probability of It successfully distributes the energy load becoming cluster-head in round zero is given as:over all the nodes of the sensor network by P(n) = p/(1-(p*(rdynamically rotating the cluster-head functionality mod 1/p)))among the nodes. P(n) = Energy of node/Total It makes the cluster-head decision and Energy of the Clusterselection process truly distributed without requiring a Here p indicates optimum number of cluster-central arbitrator for these decisions. head in a round ( 5 % as suggested by LEACH) and r It uses the data aggregation strategy, this denotes round number.strategy help in making a judicious use of the node 2100 | P a g e
  3. 3. Mr. Rajesh Halke, Mrs. Kulkarni V. A./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2099-2102Actually during Data Transmission phase of each 3.1.3. Schedule Creation Phaseround every member sends data along with The cluster-head node receives all theinformation of its residual energy to their cluster- messages for nodes that would like to be included inhead and based on this information, the cluster-head the cluster. Based on the number of nodes in thedecides which node will become the future cluster cluster, the cluster-head node creates a TDMAhead. This is done by calculating the probability of schedule telling each node when it can transmit. Thisbecoming cluster head as a function of node energy schedule is broadcast back to the nodes in the cluster.divided by total energy of the cluster. The schedule creation broadcast message consists of the following fields:  The schedule message flag SCHED_MESSAGE  The CDMA spreading code to be used for communications within the cluster  The TDMA schedule consisting of N number of {node-identity(node_id) – TDMA time- slot} pairs 3.1.4. Data Transmission Phase (Steady-state Phase) Once the clusters are created and the TDMA schedule is fixed, data transmission can begin. If the nodes have data to send, they send it during their allocated transmission time to the cluster head. The cluster-head node must keep its receiver on to receive all the data from the nodes in the cluster. Also in this case each member node must keep their receiver on to receive cluster-head status. A data message which is sent to cluster-head consists of the following fields:  The Data message flag DATA_MESSAGE  Identity of the source node n  Cluster-head idFigure 3-1: Cluster-head decision in En-LEACH  Residual energy left in node n ,E(n)protocol  The actual data if any The cluster-head status message contain following Each node that has elected itself a cluster- field:head for the current round broadcasts an  The message flagadvertisement message to the rest of the nodes. For CLUSTER_HEAD_DOWNthis “cluster-head-advertisement” phase, the cluster-  The cluster-head idheads use a CSMA MAC protocol, and all cluster-  The probability of becoming cluster-headheads transmit their advertisement using the same for each node i.e. (P(n) , node id) pair.transmit energy. The advertisement message contains Where P(n) = Energy of the node/total energy of thethe following fields: cluster. The advertisement message flagADVERTISE_MESSAGE 3.1.5. Future Cluster-head Update Phase Cluster-head id If the cluster-head is alive even after data Cluster-head location transmission phase then it can update the probability of each of its members becoming future cluster head3.1.2. Cluster Set-up Phase by sending following update message: After each node has decided to which cluster  The message flagit belongs, it must inform the cluster-head node that it CLUSTER_UPDATE_MESSAGEwill be a member of the cluster. Each node transmits  Cluster-head id (it’s own id)this information back to the cluster-head again using  Probability of each of its members { nodea CSMA MAC protocol through selection message. id(n), P(n)} in pair.The contents of the selection message are:• The selection message flag RESULTCLUSTER_SELECT_MESSAGE EN-LEACH protocol was simulated and• Cluster-head identity compared with LEACH protocol both in uniform and• Self node id non-uniform energy distribution scenario. 2101 | P a g e
  4. 4. Mr. Rajesh Halke, Mrs. Kulkarni V. A./ International Journal of Engineering Research and Applications (IJERA) ISSN: 2248-9622 Vol. 2, Issue4, July-August 2012, pp.2099-21024.1. Uniform Energy Distribution (due to energy required for data aggregation and long Once a node runs out of energy, it is distance data transmission).considered dead and can no longer transmit or This provision is missing in LEACH protocol.receive data. For these simulations, energy is  En-LEACH is more effective; producingremoved whenever a node transmits or receives data. high level information about the environment the nodes are monitoring in an energy-efficient way.  En-LEACH is able to handle non-uniform energy distribution of sensor nodes which is an important characteristic of a dynamic sensor networks. REFERANCES: 1. Malik Tubaishat and Sanjay Madria. Sensor networks: an overview. In IEEE Potentials, April/May 2003, Pages: 20–23 2. Deborah Estrin, David Culler, Kris Pister andGauravSukhatme. Connecting the Physical World with Pervasive Networks. InFigure 4-1: System lifetime - LEACH protocol IEEE Pervasive Computing, Volume 1, Issue 1 (January 2002), Pages: 59–69. 3. Berkeley, University of California, 800 node self-organized wireless sensor network. 2001: 4. System Architecture for Wireless Sensor Networks: pdf.Wendi Rabiner Heinzelman, Anantha Chandrakasan, and Hari Balakrishnan. Energy-Efficient Communication Protocol for Wireless Microsensor Networks. In Proceedings of the Hawaii International Conference on System Sciences, January 4- Figure 4-2: Sensors that remain alive (Non dot) 7, 2000, Maui, Hawaii.and those that are dead (dots) after 31 round for 5. Wendi RabinerHeinzelman,LEACH protocol. AnanthaChandrakasan, and Clusters are indicated using HariBalakrishnan , An Application-specificdifferent colors Protocol Architecture for WirelessThe results can be summarized as follows Microsensor Networks ,in IEEE transaction The first death in En-LEACH occurs at on wireless communications ,vol-1, no-4,round 38, whereas in case of LEACH the first node October 2002.dies at round 22, hence first node death is 2 times later than the LEACH einzelman.pdf.protocol. 6. M. Bhardwaj and A. Chandrakasan. Power Also the last node death in En-LEACH Aware Systems, presented at theoccurs much later than the last node death in case of 34thAsilomar Conference on Signals,LEACH. Systems and Computers, November 2000. 7. X. Lin and I. Stojmenovic. Power-AwareCONCLUSION Routing in Ad Hoc Wireless Networks. In In LEACH, there may be a case when SITE, University of Ottawa, TR-98-11, Dec.cluster-head chosen which having less amount of as compared to its cluster member nodes, 8. J. Broch, D. Maltz, D. Johnson, Y. Hu, andwhich will result in early death of cluster-head. But J. Jetcheva. A Performance Comparisonin case of En-LEACH, cluster-head depending upon ofMulti-Hop Wireless Ad Hoc Netowrkenergy left in the node, hence it is bound to perform Routing Protocols. In Proc. 4th ACMbetter than LEACH. InternationalConference on MobileIn En-LEACH, all cluster members are kept informed Computing and Networking (Mobicom98),about the status of their cluster-head (whether it is October 1998.alive or dead), since the probability of failureofcluster-head is high during data transmission phase 2102 | P a g e