Vol. 4, No. 4 April 2013 ISSN Journal of Emerging Trends in Computing and Information Sciences CIS Journal. All rights reserved.

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1 WP A Tree Based Response Tme Algorthm for Event Drven Wreless Sensor Networks 1 Itu Sngdh, 2 Saurabh Kumar 1 Department of Computer Scence and Engneerng, Brla Insttute of Technology, Mesra, Ranch, Jharkhand, , Inda 2 Department of Computer Scence and Engneerng, Brla Insttute of Technology, Mesra, Ranch, Jharkhand, , Inda ABSTRACT Irrespectve of the deployment strategy or the coverage constrants, the usual energy conservaton nevtablty remans. Among the many approaches that have come up so as to save energy, reducng the number of transmssons and an effectve routng strategy accomplsh consderaton. In addton to the number of transmssons, the response tme and average delay become crtcal when referrng to an event drven sensor network. Ths paper s an effort to reduce the burden of exstng routes, neutralze the hot spots for a balanced and unform energy depleton of sensors as well as a better response tme n order to ncrease the effectveness of the network as a whole. A Parallel approach to reduce the overhead of ndvdual sensors thereby ensurng a unform depleton of the nodes has been proposed wthout compromsng the energy and network constrants. Keywords: Sensor Network, Tree Herarchy, Energy conservaton, Response tme. 1. INTRODUCTION A wreless sensor network (WSN) conssts of spatally dstrbuted autonomous sensors to montor physcal or envronmental condtons, such as temperature, sound, pressure, turbdty, humdty, etc. As an advantage, there s no need of physcal connectons among nodes to communcate wth each other n a WSN [1]. The sensors cooperatvely pass data through the network to a man locaton.e the base staton. The man functon of sensor nodes s to collect and send data to snk nodes whch are connected to computng devces and external networks [2, 3]. An event drven wreless sensor network s a specalzed network that detects any anomaly n the condton under observaton and nforms the base staton wthn the real tme constrants. In addton to sendng perodc observatons, the sensng node reports the event through messages on any event of nterest. For the purpose, some Intellgency for sgnal processng and networkng of data s ncorporated n the sensor nodes. Among the vared qualty of servce requrements n a wreless network, response tme s one of the cost measures to judge the qualty of a dstrbuton strategy. Optmal response tme s crucal when gong for query processng n a sensor network analogous to a dstrbuted system. The parameters affectng response tme are Type of network mantaned, Access of data: local or remote, Process of communcaton: seral or parallel, Lfetme and energy constrants, Communcaton speed, memory and bandwdth Propagaton technque. We dscuss the related work n Secton 2, the effect of balanced and unbalanced tree herarchy n Secton 3, present the system model and descrbe WP approach n detal n Secton 4. The descrpton of expermental evaluaton follows n Secton 5 and a summary and concluson of work n Secton RELATED WORK The response tme of a sensor node gets affected by collsons n data packets. The balancng of the node degrees results n mnmzaton of packet collsons durng query executon. The Mnmum-Hot-Spot query routng trees [1] acheves tree balancng for a dstrbuted algorthm that s much closer to the centralzed algorthm. The algorthm utlzes Coeffcent of Varance (COV) parameter and a sequental greedy parent selecton strategy. The average response tme of the whole network can be reduced by ncorporatng balanced load strategy so that the energy usage of each node s almost equal and average lfetme of the network s ncreased [4]. A decsve varable for prolongng the longevty of a WSN s to mnmze the utlzaton of the wreless communcaton medum. It s well establshed that communcaton over the rado n WSNs s the most energy demandng factor among all other functons, such as storage and processng [5]. In utlzng multple paths for respondng an event by the sensor node, the multple copes of the same packet may be travellng along dfferent paths n parallel towards the same destnaton due to whch duplcty s ncurred [6]. An alternatve to the method s to choose to create multple possble paths, but use only one of them at a tme [7], whereas other works have focused on nnetwork data processng as a means for energy savng [8]. For example, the utlzaton of PERLA as a data gatherng protocol for wreless sensor networks employs a hybrd sngle/ mult-path routng algorthm whch makes use of alternatve paths when necessary [7]. 372

2 The proposal of VTAMn [9] constructs a vrtual backbone tree usng the characterstc dstance. It connects a non-tree node to a tree node whch guarantees the mnmal energy consumpton to transmt data to the snk node. Ths results n a mnmum packet collson n the network, hence optmzng the response tme of nodes. Wth characterstc lmtatons of a sensor node and need to satsfy real tme response constrants, the need of a parallel dstrbuton scheme s requred. It can be servce based archtecture [10] for desgnng sensor networks, where the data communcaton functonalty s separated from the applcaton-specfc processng, or an mplementaton of a mult-rado WSN platform [11], where smultaneous data exchange wth multple neghbors can be used for mnmzng hop delays and for maxmzng network throughput. Although random placement s consdered to be the ultmate long term goal, t s currently nfeasble n most stuatons as the ndvdual sensors are generally too expensve to deploy n an envronment where the probablty of destructon of nodes durng deployment s hgh [12]. Random deployment of nodes can be augmented wth determnstc features to acheve fner placement pattern. In ths paper, we ntroduce a dstrbuted algorthm, coned Weghted Parallel (WP) algorthm that uses parallel transmssons and load balancng n order to almost equalze the energy consumpton of each sensor node, whch mnmzes the collson n network. WP explans a herarchcal communcaton wth optmal query forwardng on the bass of selecton probablty and weghts and has been found successful n reducng both the average response tme and average energy of consumpton. 3. EFFECT OF BALANCED VS UNBALANCED LOAD It requres a robust strategy to communcate across the network wth the mnmum overhead wth the usual constrants lke energy. The event drven WSN has an advantage that for large applcatons, t requres fewer messages to be transmtted. In order to process contnuous queres n an event drven WSN, a data acquston framework s mantaned that organze sensors n a tree herarchy (T). Ths herarchy provdes each sensor wth a path over whch the sensed data s transmtted to the snk node. In the current scenaro, T s constructed n an ad-hoc manner; hence there s no guarantee of dstrbuton of workload equally among the nodes n the network [12]. The unbalanced workload poses three major challenges: ) Increase data transmsson collson; ) Wastage of energy due to unnecessary collson; ) Reducton n network lfetme; snce most of the energy s spent on transmttng and recevng data, the node wth hgher workload wll be depleted more rapdly than others; v) Reduced coverage of the sensor nodes, resultng n undesrable response tme of the nodes; n absence of alternate parents, the nodes whose parent has depleted wll have lesser or no coverage. 4. SYSTEM MODEL We formalze our system model and the basc termnology that wll be utlzed n the subsequent sectons. We gve formal defntons and propostons that we use n our algorthms and use to defne the optmzed response tme. Let V denote a set of n sensng devces {v 1, v 2 v n } n an Event drven wreless sensor network. Let T = (V, E) denote the network tree that represents the communcaton edges E of the nodes n V. The nodes are consdered neghbors f they are wthn communcaton range. The sensor nodes are deployed usng QRA. The QRA uses Quas Monte Carlo Integraton strategy for calculaton of coordnate values. The dscrepancy sequence utlzed s Halton sequence that s multdmensonal n mplementaton. Thus, the nodes are deployed wth ther unque nodeid and are locaton-aware. 4.1 Assumptons Assume that the nodes have a restrcted communcaton range. In ths case, a routng tree T s created connectng every node over a mult-hop path wth the snk. Each node has ts local depth (d v ) and branchng factor (the number of chldren to accommodate) known to tself. Defnton 4.1.1: Gven a tree T = (V, E), an edge (u, v) E, and range R of a node, then a node S j wll be the chld of node S f and only f S j s n range of S, where (S, S j ) V. The herarchy tree generated wll be balanced n order to mnmze the number of collsons durng transmsson across the network. Defnton 4.1.2: A tree T s balanced f and only f all the nodes n the tree has number of chldren less than or equal to the branchng factor. Each node s assocated wth energy (J) n Joules, wth each path among nodes s assgned a weght (W) parameter. The response tme s calculated (as shown n Fg. 1.) on the bass of the most elgble lnk to transmt that s computed dynamcally on comparson of the dstance from the randomly generated events and the mnmum weghts that are assgned to each connectng lnk as a measure of energy conservng crtera. 373

3 Fg 1: Detecton and forwardng of event message to the snk node 4.2 Notatons N Notatons Table 1: Lst of notatons. Descrpton total number of nodes deployed S set of all nodes deployed (X, Y ) coordnates of th node Node_ID unque dentfcaton of each node T tree generated usng node communcaton. level level of node n tree herarchy. parent_dstance R ED APL B W E cost D 4.3 Algorthm dstance of node from ts parent response tme Eucldean dstance between and j alternate parent lst of a node optmal branchng factor weght of path between a par of nodes set of events transmsson cost of a node Eucldean dstance between an event and sensor node /* Deployment of nodes*/ 1: Begn procedure waltz_deploy (n, b ; where (b є smallest prme number set)). 2: For 1: n repeat 3: Compute coordnate: call (halton (, b )). 4: End procedure. /* Tree generaton*/ 1: Begn procedure waltz_tree (S, (X, Y ); where (S є set of nodes)). 2: Intalze : =0, j: =1, range of each node: = range. 3: Whle ( < n) do 4: Whle (j < n) do 5: If (j and. parent NULL) then calculate ED (, j) 6: If(ED (, j) < =. range) then 7: If (j. parent = NULL) then 8: Assgn parent to node 9: Else assgn the alternate parent lst (APL) to the node. 10: End f. 11: End f. 12: End f 13: End whle. 14: End whle. 15: End procedure. /* Tree Balancng*/ At S 0. 1: Gegn procedure waltz_balanced (S ; chldren (S ); APL (S j ), where (S j є chldren (S )) ). 2: (B, newparent) = receve (); Get nfo from parent. 3: Step 1: Connect to new parent f needed. 4: whle (newparent NULL) do 5: If (! connect (newparent)) then 6: Newparent= getnewparent (parent (S )). 7: End f. 8: End whle. 9: Step 2: Adjust the parent of the chldren nodes. 10: If ( chldren (S ) < = B) then 11: For j=1 to chldren (S ) do 12: Send (B, NULL, S j ). 13: End for. 14: Else Ask chldren (S ) - B nodes to change ther parent. 15: Whle ( chldren (S ) > B) do 16: S j = getnext (chldren (S )). 17: If ( APL (S j ) > 1) then 18: Newparent = alternparent (APL (S j ), S ). 19: Send (B, newparent, S j ). 20: Chldren (S ) = chldren (S ) - S j. 21: Else send (B, NULL, S j ). 22: End f. 23: End whle. 24: End f. 25: End procedure. /* Response Tme Calculaton*/ 1: Begn procedure waltz_response (T near_balanced, R). 2: Intalze :=0, j:=1, W :=0, cost:=1; where (W є weght of each connected path; cost є transmsson cost). 3: Whle ( < n) do 4: Whle (j < n) do 5: Calculate ED (, j). 6: End whle. 7: For each event E, calculate ED (E, node_id (X, Y )). 8: Assgn dstance D to each node for whch ED (E, node_id (X, Y )) < R. 9: If (W s same for all the sensng nodes) then 10: Choose mnmum (D ) as the sensng node (P). 374

4 11: R: = (cost * ED (, j) 2 ). 12: End f. 13: If (W has dfferent values at any nstant) then 14: If (D 1 < D 2 and W 2 < W 1 ) then 15: Add delay (go to step 12 and calculate response tme for W 2 ). 16: End f. 17: End f. 18: End procedure. 5. RESULTS For analyss, a set of ten events are taken randomly, calculatng ther Eucldean dstance from the set of nodes deployed. As soon as a sensor node senses an event, t sends ts response to ts parent on the bass of weght path value. The mplementaton work s carred out usng stand-alone CPP packages and the results of WP approach are compared wth WQRT approach by plottng the response tme of each node for both the balanced and unbalanced workloads. As shown n Fg. 2, 3 and 4 below, the response tmes of WP and WQRT are compared. The response tme for balanced workload s lesser as compared to the unbalanced workload. It was seen that n case of WQRT, same node senses and sends the event response multple tmes due to whch wth ncrease n the number of nodes, the energy depleton wll be faster. In WP approach, the fare share of energy s possble among the sensor nodes, due to whch the coverage, lfetme of the sensor node, and n turn, the lfetme of the whole network s enhanced wth effectve response tme. Fg 4: Comparson of WP/WQRT response tme and energy usage for n= CONCLUSION Snce an energy constraned event drven WSN requres a fast response for anomaly detecton, the delay n query forwardng becomes crtcal. Moreover lesser energy consumpton leads to a longer lfetme whch s eventually the man am of coverage. It s observed that by usng a ratng method n terms of weght ensures a tree based archtecture to be able to balance the energy depleton better as well as proves to acheve a better response tme. Ths work s prelmnary and needs to be extended for a larger set of nodes. REFERENCES [1] G. Chatzmlouds, D. Zenalpour-Yazt, D. Gunopulos, Mnmum-Hot-Spot Query Trees for Wreless Sensor Networks, Proceedngs n ACM Internatonal Workshop on Data Engneerng for Wreless and Moble access, June [2] I. F. Akyldz, W. Su, Y. Sunkarasubramanam, E. Cayrc, A Survey on sensor networks, IEEE Communcaton magazne, vo. 40, pp , [3] A. R. Hevner, S. B. Yao, Query processng n dstrbuted database systems, IEEE, vo. SE-5, pp , Fg 2: Comparson of WP/WQRT response tme and energy usage for n=5. [4] M. Yngch, L. Xaofang, L. Y, Workload-based query routng tree algorthms n wreless sensor networks, IEEE, [5] D. Messna, M. Ortolan, G. Lo Re, A Network protocol to enhance robustness n tree-based WSNs usng data aggregaton, IEEE, [6] C. Intanagonwwat, R. Govndan, D. Estrn, Drected dffuson: a scalable and robust communcaton paradgm for sensor networks, In Moble Computng and Networkng, pp , Fg 3: Comparson of WP/WQRT response tme and energy usage for n=7. [7] K. Ln, H. Zhao, Z. Yn, D. Luo, An adaptve classfed data aggregaton arthmetc for wreless sensor networks, IEEE, pp , [8] J. Km, Jee-Hyong Lee, VTAMn: A Vrtual backbone tree algorthm for mnmal energy 375

5 consumpton n wreless sensor network routng, IEEE, pp , [9] S. Chakraborty, S. Chakraborty, S. Nand, S. Karmakar, A tree-based local reparng approach for ncreasng lfetme of query drven WSN, IEEE, pp , [10] A. H. Mohajerzadeh, M. H. Yaghmaee, Z. Eskandar, Tree based energy effcent and congeston aware routng protocol for wreless sensor networks, IEEE, pp , [11] M. Brazl, C. J. Ras, D. A. Thomas, Determnstc Deployment of Wreless Sensor Networks, Proceedngs of the world Congress on Engneerng, vo. 1, [12] P. Andreou, A. Pambors, D. Zenalpour-Yazt, P. K. Chrysanths, G. Samaras, ETC: Energy-drven Tree Constructon n Wreless Sensor Networks, pp , AUTHOR PROFILES 1. Itu Sngdh receved the Masters degree n software engneerng from BIT Mesra (Ranch). Currently, she s an Assocate Professor n the department of Computer Scence and Engneerng at BIT Mesra and also pursung her Ph.D. from the same nsttute. She has a couple of natonal and nternatonal publcatons n the feld of Wreless Sensor Networks and network securty. Her areas of nterest nclude Software Engneerng, Database Management Systems and Wreless Sensor Networks. 2. Saurabh Kumar receved the degree n computer scence from Chhattsgarh Swam Vvekanand Techncal Unversty (Bhla) n He s currently workng towards the completon of the M.Tech degree n the Department of Computer Scence n BIT, Mesra. Hs research nterests nclude Wreless Sensor Networks and Wreless Communcatons. 376