A Load-Balanced Clustering Protocol for Hierarchical Wireless Sensor Networks

Transcription

1 International Journal of Advanes in Computer Networks and Its Seurity IJCNS A Load-Balaned Clustering Protool for Hierarhial Wireless Sensor Networks Mehdi Tarhani, Yousef S. Kavian, Saman Siavoshi, Ali Mahani Abstrat The energy limitations and assoiated problems are main hallenging issues for designing and employing battery powered wireless sensor networks (WSNs). This paper proposes a novel energy-effiient lustering protool. The protool uses a new algorim for distributing luster heads (CHs) in network. The luster formation struture is used for load balaning among far and near luster heads to e base station (BS). The paper fouses on intra-luster ommuniation and CHs use single hop sheme to ommuniate wi BS. The protool works well in small size networks. Simulation results verify at proposed protool outperform over LACH and TCAC protools for 29% and 10% in term of funtional network lifetime respetively. Keywords wireless sensor networks, hierarhial lustering, energy effiieny, load balaning. I. Introdution The wireless sensor networks are mainly onsidered as potential solution to monitor physial and harsh environments wi limited aess and olleting data from em [1]. The limitations on battery and power systems of nodes, illustrate at energy is a ritial issue for employing WSNs for different appliations [2]. In reent years muh researh has been onduted to mitigate e ritial hallenges of energy onstraints. In periodial data olleting appliation a ommon tehnique is used to luster e nodes. In is approah, a leader node named luster head (CH) node in eah luster is seleted and all ommon nodes send eir sensed data to orresponding CH node. The CH nodes aggregate e data and send em to e BS diretly or via oer nodes using multihop ommuniation sheme. The main idea behind is tehnique is to derease e number of messages at should be sent to e BS rough loal aggregation as well as derease long-distane ommuniation bo for energy saving [3]. In fair management shemes of large sale WSNs e deentralized approahes are onsidered where nodes use loal information to make deision about eir tasks suh as sensing, ommuniating and proessing tasks using ontrolling pakets. In is sheme one hallenge is e CH ount variation. Mehdi Tarhani, Yousef S. Kavian, Saman Siavoshi Faulty of ngineering, Shahid Chamran University of Ahvaz, Ahvaz Iran Ali Manahi Faulty of ngineering, Shahid Bahonar University of Kerman, Kerman Iran In fat large luster ount has high inter luster ommuniation ost and small luster ount inreases intra luster energy onsumption. The energy unbalaning among all nodes espeially in CH nodes ause quikly draining energy of some nodes making network un-funtional. This may be due to CH nodes distribution, differenes in nodes distanes to e BS or speial struture of used protool. For example in ase of ommuniation approahes between CHs and e BS, in single hop sheme, e CHs at are farer to e BS have more energy onsumption in ontrast to multi hop ommuniation sheme impose larger traffi burden on near BS nodes[4]. In proposed protool in is paper, in order to mitigate CH ount variation first some nodes are seleted as CH andidates so at andidate number is larger an desired CH number and,erefore, protool knows how many andidates should be eliminated. On oer hand for fair CH distribution, e protool uses a distane based algorim whih in a repetitive manner delete some andidate. In is way e algorim deletes some andidates, so a fixed CH ount and a good possible CHs distribution ould be ahieved depending on andidate s distribution. In lustering sheme CH nodes have more energy onsumption. In proposed protool to protet low level energy nodes, ese nodes have no hane to beome CH node and CH nodes uses single hop approah to ommuniate wi e BS. For balaning energy onsumption in CHs, e lusters farer to e BS are smaller an lose ones. This is deferent from ommon multilayer tehnique in WSNs at bo CH node density and luster size vary wi distane to e BS. In remaining of e paper, setion II overview energy effiient hierarhial protools, setion III desribes proposed protool in detail, en in setion IV proposed protool is evaluated in term of energy effiieny and finally setion V onludes e paper. II. Related Works This setion provides a quik review on some related works on lustering protools in WSNS. In [5], an adaptive distributed arhiteture named LACH protool was introdued. The protool uses two star topology layers in network. In first layer, CH nodes are enters and in seond layer e BS. The protool assumes at all CHs or member nodes have e same energy onsumption. Totally in LACH all nodes have e same hane to beome CH node. In eah round eah node alulate its hane to beome CH node as follows: 6

2 P 1 T ( n) 1 Pr mod P 0 International Journal of Advanes in Computer Networks and Its Seurity IJCNS Where P is total luster head probability, r is urrent round number and G is nodes at in 1/P have not been seleted as luster head. The LACH protool annot ontrol e CH nodes distribution aross e network and CH nodes ount may be ompletely deferent from desired CH number. In [6] an energy-aware protool named TCAC is proposed. The TCAC protool uses a powerful algorim to have good CHs distribution in eah round. This protool tries to balane energy onsumption in CH nodes and prolongs network lifetime. III. The Proposed Protool (1) This setion first make all assumptions and network model, en give proposed protool in details. A. Network Model if n G oerwise N nodes are dispersed in a M M area and are fixed after deployment The base station (BS) is stationary and far from network area. Nodes don t have any information about eir loation and aren t equipped wi global positioning system. Network appliation is periodi data olletion and in eah yle alled round sensed data are gaered and send to e BS after loal aggregation. ah node an estimate its distane to anoer node or e BS based on streng of reeiving signal from e node. The BS has not suh limitation as proessing, storing, energy. B. nergy Consumption Model In is paper a node onsumes energy for transmitting, reeiving and proessing data as follows: 2) Reeiving mode In is mode energy onsumption is:. L (3) r x 3) Proessing mode It is assumed at e miroontroller onsumes energy only for aggregating sensed data as follows:.. pr DA n L (4) Where n is number of data messages and DA is data aggregation energy. C. Protool Desription In is protool eah round is omposed of two time duration alled set up phase and steady state phase. In first phase, e luster and luster heads are seleted en in seond phase, e data gaering is performed depending on topology formed in previous set up phase so at member node send eir data to assigned luster head diretly and luster heads after aggregating gaered data send em to e BS diretly. In following we explain how e protool selets luster heads and form lusters. In an initial phase, before first round all nodes estimate eir distane to e BS. 1) Cluster head seletion To selet luster heads proposed protool first selet some andidate from high level energy nodes depending on energy information provided by luster heads in provirus round. In is way to protet low energy nodes, e nodes at eir energy is less an a reshold ( ) essentially are not e andidate. This reshold is different for different nodes but during network operation is fixed for eah node: N (( )..(1 ) ). L (5) K i x t (d(i,bs)) data where i is node ID, K is desired luster head ount, is protool parameter between zero and one, L data is data paket size and d (i,bs) is distane between node i and e BS. So in set up phase, all nodes wi energy level more an orresponding alulate a reshold number T as follows: is: 1) Transmitting mode To transmit a L bit message to distane d required energy 4 ( x m d ).L d tx (d) 2 (2) ( x f d ).L d Where x is radio iruit energy onsumption, m and are multipa fading hannel and free spae model fators. f T res i i (6) Z where res is residual energy of node i and Z is: i Tot Th Z (7) k 7

3 International Journal of Advanes in Computer Networks and Its Seurity IJCNS Figure. 1. The andidate eleminating approah where K is expeted andidates and Tot Th is total energy of nodes at eir energy is more an orresponding Th. Now eah node produes a random number in (0,1) and ompares at wi its T and if is value is less en T onsider itself as a andidate oerwise in urrent round will be a member node. These elementary andidates introdues emselves by broadast aross e network using a andidate-msg inluding its ID and normalized distanes to oer introdued andidates in Rad radiane. As soon as number of introdued andidates satisfies k, remaining unintrodued andidates doesn t ontinue is proedure and will onsider emselves as member nodes. At first every andidate alulates its pnt value at is multiplying distanes to oer andidates ( Rad is used instead of distanes larger an Rad ). ah andidate wi respet to oer andidate-msg alulates oer andidates pnt values. The andidate wi least pnt gives up e ompetition. The pnt values are realulated but distanes to eliminated andidate no longer aren t taken into aount. A andidate wi least pnt gives up e ompetition again. This proedure is followed till number of remaining andidates be equal to K. Fig. 1 shows an example of is proedure. In some latest yle of network operation nodes residual energy may be very low, suh at e number of nodes wi energy level higher an is not bigger an k and ese rounds are alled ltst rounds. In ese rounds nodes don t take into onsideration to beome luster head andidates and in relation (7), Tot (total remaining energy) is used instead of Tot. 2) Cluster formation After determining luster heads, ey broadast a message named h-msg ontaining eir ID, distane to e BS and spreading ode. Now eah member node hearing some or all of h-msg messages selet its luster head to send sensed data to at, as follows: If ere is at least two CHs in R mem (a parameter of protool) radiane, e member node selet one at is loser to ehe BS, oerwise selet nearest luster head. Then eah member node sends a join-msg message inluding its ID, luster head ID and residual energy to inform its luster head. ah luster head identify its members and all luster heads alulate Tot or Tot ooperatively to use in following round and inform all nodes about is value. After is proedure, like LACH protool, eah luster head sends a shedule-msg message to inform all members about time slot numbers at ey should send eir data and e medium aess is based on TDMA protool. Now set up phase is ended and steady state phase get started. The template is used to format your paper and style e text. All margins, olumn wids, line spaes, and text fonts are presribed; please do not alter em. You may note peuliarities. For example, e head margin in is template measures proportionately more an is ustomary. This measurement and oers are deliberate, using speifiations at antiipate your paper as one part of e entire proeedings, and not as an independent doument. Please do not revise any of e urrent designations. 8

4 International Journal of Advanes in Computer Networks and Its Seurity IJCNS IV. Simulation Results To evaluate proposed protool in term of energy effiieny e proposed protool is simulated and ompared wi two energy effiient protool named LACH and TCAC protools. In is paper MATLAB tool is used to simulate all protools. In literature ere are deferent lifetime definitions. Totally, is depends on network appliation ough some works define lifetime wi respet to simpliity of protool analysis [7]. In is paper e time to first node dead in round is onsidered as network lifetime. Therefore to inrease lifetime a protool should onsider bo energy onsumption and load balaning espeially among nodes in deferent region of network area. All parameters used in is paper is summarized in Table 1. The high R mem values inrease intra luster ommuniation distanes and small values makes unbalaning in luster head loads, so at farer to e BS luster heads have more energy onsumption. Also high luster heads number inrease data pakets at should be sent to e BS onsequently inrease energy onsumption espeially in far BS ases. In small ases intra luster energy onsumption roughout e network is inreased. Fig. 2. The dead nodes in eah round 9

5 International Journal of Advanes in Computer Networks and Its Seurity IJCNS Fig. 3. The network residual energy The simulation parameters are onsidered as; k 5, k 8,.5 Rad 55 and Rmem 25 for simulation onduted in is paper. In e proposed protool, e variation of luster head number is small. This is reasonable as expeted luster head number ( k ) is smaller an desired luster head andidates ( k ). For LACH protool k opt 5 is used and in TCAC protool K initial and Range is set to 30 and 32 respetively. Fig. 2 shows at proposed protool derease energy onsumption and Fig. 3 shows e dead node number in eah round onsidering after first node dea. As shown, e proposed protool mitigates energy unbalaning among nodes and inrease network lifetime. The proposed protool an work wi bo heterogynous and homogenous networks as uses residual energy of nodes to selet luster heads. V. Conlusion This paper proposed a distributed energy-aware protool at onsiders CH node ount variation and CHs distribution aross e network. Simulation results verified at proposed dereases total energy onsumption along wi improving load balaning. Also proposed protool inreased funtional network lifetime 29% and 10% over LACH and TCAC protools respetively. TABL I. TH USD PARAMTRS AND NOTATIONS Parameter Area Loation of BS N initial x m DA Data Paket size Control Paket Size f value (0,0)~(100,100) (50,175) 100.5J 50 nj/bit 10 pj/bit/m pj/bit/m nj/bit/signal 4000 bits 200 bits 10

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