Cost-Effective Lifetime Prediction Based Routing Protocol for Wireless Network

Transcription

1 Cost-Effectve Lfetme Predcton Based Routng Protocol for Wreless Network ABU MD. ZAFOR ALAM, MUHAMMAD ARIFUR RAHMAN, MOHAMMED ABUL HASAN 2,M. LUTFAR RAHMAN Faculty of Scence and IT, Daffodl Internatonal Unversty, Dhaka 20, BANGLADESH 2 Deptartment of Computer Scence, Informaton Valley of IIT, Dhaka 20, BANGLADESH Abstract: Generally, n computer network traffc routng, the cost of routng s one of the prmary concerns and most routng algorthms focus on cost mnmzaton. But n case of Wreless Network, the lfetme of partcpatng nodes affects the stablty of the network. Almost every node of a network has to perform the functon of a router. Due to the lmted battery power of moble devces, recent research n wreless routng s motvated towards selecton of a path that maxmzes the network lfetme. Although, these algorthms help to mantan the stablty of the network, they are not as much cost effectve as tradtonal exstng routng algorthms owng to the greedness of lfetme. In ths paper we consder both the routng cost and network lfetme ssue n route selecton so that the network remans stable and data are routed through cost-effectve path. The smulaton results show that the proposed algorthm fnds a cost-effectve path from source to destnaton, whch helps to mantan the stablty of the network. Keywords: Routng Protocol, Moble Ad Hoc Networks, Lfetme Predcton, Wreless Networks, Dstrbuted Systems. Introducton Wreless Network s an autonomous system wth moble hosts connected by wreless lnks and work ndependent of any common central control. Routng n wreless networks has been the subject of ntense research efforts over the past few years; these efforts have resulted n numerous proposals for routng protocols. Typcally n wreless ad hoc networks, t s assumed that all the devces that make up the network are cooperatve n partcular they are wllng to act as ntermedate nodes n a routng path by forwardng data for other network nodes. These hosts are self-adaptve n that f there are changes n the network they also have to change ther won routng tables to reflect the changes of the network. The lmtaton of fnte energy supply of wreless devces rases concerns about the tradtonal belef that nodes n ad hoc network wll always relay packets for each other. Energy effcency s a key objectve n many routng protocols. An energy effcent routng protocol ensures that a packet from a source node to a destnaton gets routed along the most energy effcent path possble va ntermedate nodes. Falure of some nodes n the network mght result n lack of connectvty between nodes that are stll alve. Hence we should consder the proper utlzaton of the lmted power of a node of wreless network. Selecton of the least power cost route may possess a harmful mpact on the network stablty. Thus t s better to use a routng soluton that avods usng nodes havng small amount of remanng battery energy. The remander of ths paper s organzed as follows. In next secton we dscuss the problem of routng n moble networks and provde the metrcs we used for performance evaluaton. Secton 3 contans revew of some recent related research works. Secton 4 descrbes the ratonale and detals of the proposed cost-effectve lfetme based algorthm. Secton elaborates on the smulaton envronment, the mplementaton and expermental results comparng Cost Effectve Lfetme Predcton (CELP) wth Lfetme Predcton Routng (LPR), Demand Source Routng (DSR) and power-aware routng. At last, Secton 6 concludes ths paper. 2 Metrcs We encounter two conflctng goals: on the one sde, n order to optmze cost, least cost or shortesthop routng should be used, whle on the other sde, use of shortest-hop route means that nodes wth

2 hgher degree mght de soon snce they are used n most cases. An nterestng property of usng least-cost routng s that packet delay does not ncrease. The cost of forwardng messages could be defned and determned n varous ways takng nto account factors such as cost of energy used to forward messages, hop count, delay, lnk qualty as well as other factors. Another metrcs used s the lfetme of nodes, whch s a functon of the remanng battery energy. As n [], lfetme of a node s predcted based on the resdual battery capacty and the rate of energy dscharge. Our routng algorthm s a reactve routng protocol, whch only takes acton and starts computng routng paths when a network ntates a sesson. It uses a DSR-lke route dscovery protocol and channels all nformaton regardng cost and lfetme to the destnaton node. The destnaton node computes the cost and lfetme of each path and sends ths nformaton back to the source. 3 Related work Some researchers have tred energy effcent broadcast /multcast algorthm [2],[3]. One major approach for energy conservaton s to route a communcaton sesson along the route whch requres the lowest total energy consumpton [4][]. Ths optmzaton problem s referred to as Mnmum-Energy Routng [6]. Whle the mnmumenergy uncast routng problem can be solved n polynomal tme by shortest-path algorthms, t remans open whether the mnmum-energy broadcast routng problem can be solved n polynomal tme, despte the NP-hardness of ts general graph verson. Recently three greedy heurstcs were proposed n [] MST (mnmum spannng tree), SPT (shortest-path tree), and BIP (broadcastng ncremental power). They have been evaluated through smulatons n [8], It has recently been recognzed that medum access control (MAC) schemes can sgnfcantly ncrease the energy effcently of moble batteres [9]. If moble devce A transmts data to another moble devce B, neghborng mobles do not lsten to the data from moble A snce lstenng causes unnecessary moble power consumpton. Another energy effcent MAC scheme has been proposed n [0]. The man dsadvantage of power aware routng [] technques s that t always selects the least power cost routes. As a result, there s a large possblty of selectng a node, whch has a very lttle lfetme; hence t would de early. So the network wll get dsconnected and the network lfetme wll be adversely affected. Besdes, n these technques a partcular node may become a vctm because of ts poston at such a place that makes t selected frequently and hence de early. Ths s doubly harmful snce the node that de early s precsely the one that s needed most to mantan the network connectvty. Therefore, t wll be better to use a hgher power cost route f ths routng soluton avods usng nodes that have a small lfetme. Keepng t n mnd, [] proposes a lfetme predcton based routng algorthm. Lfetme predcton routng s an on demand source routng protocol that uses battery lfetme predcton. The objectve of ths routng protocol s to extend the servce lfe of wth dynamc topology. Ths protocol favors the path whose lfetme s maxmum. The authors calculated the lfetme of a route wth the followng equaton. MaxT ( t) = Mn( T ( t)) π π επ Where: T π (t): lfetme of path π T (t): predcted lfetme of node n path π In ths algorthm lfetme of a path s predcted by the mnmum lfetme of all nodes along the path. That path s selected whch has maxmum value of calculated mnmum lfetmes. The man objectve of LPR s to mnmze the varance n the remanng energes of all the nodes and thereby prolong the network lfetme. Although, LPR ncreases the stablty of the network, ths technque has totally overlooked the cost of routng. To acheve best performance we propose a routng algorthm that combnes the best features of the two above-mentoned technques. 4 Proposed Model A network N=(V,E, ω) conssts of a set of nodes V={v,.,v n } that represent moble devces, a set E V x V of drected edges (v, v j ) that connect two nodes, and a weght functon ω:e R (Ratonal number) for each edge (v, v j ) that ndcates the cost of transmttng a data packet from node v to v j. Each node has a unque dentfcaton number, but t s not a pror known whch nodes are currently n the network, nor s edge set E or weght functon ω

3 known. A node can not control the drecton n whch t sends data, and thus data are broadcast to all nodes nsde ts transmsson range. Nodes can move and the edge cost between any two nodes can change over tme. Also the lfetme of any node can change over tme. However, for the ease of presentaton, we assume a statc network durng the route dscovery phase. 4. Cost-Effectve Lfetme Predcton based routng (CELP) Our objectve s to select a cost effectve route, whch affects less on the stablty of the network. Routng cost and lfetme of nodes are used as the selectng parameters of a path. In power-aware routng algorthms the selected path of transmsson s the most cost-effectve whereas n lfetme predctve routng algorthms selects a path wth maxmum lfetme and hence results stablty of the network. Power-aware routng algorthms suffer from poor stablty and lfetme predcaton based routng algorthms suffer from poor cost effectveness. Our proposed CLPR algorthm s more stable than that of power-aware routng and also has less cost than that of lfetme predcton routng. Let us assume the possble lfetme of any node s up to L and the possble transfer cost between any two nodes s up to C. We defne a scalng factor ξ as the rato of the two parameters. L ξ = C Let there be n paths (π, π 2,..π n ) from source to destnaton. Then lfetme of a path π s τ = MnT j (t) jε and the cost of a path π s ς = π m cπ j, j + j= ( t) where π m s number of nodes n path π and c j,j+ s the cost between node j and j+. Our path selectng parameter β s represented by τ β = ξς The algorthm selects a path, whch has the largest β. If more than one path havng hghest β s found, the path wth hghest hop count wll be selected. 0 S 9 8 E C A F 00 B 20 G 46 Fg : A network wth 8 moble nodes wth ther battery lfetmes As an example, consder the scenaro shown n fgure. Here from source (S) to destnaton (D) there are sx paths. They are: Path : S A B D Path 2: S A B C F G D Path 3: S E F C B D Path 4: S E F G D Path : S C F G D and Path 6: S C B D. If we calculate the total cost along each path and select the path wth mnmum cost among them, as done n cost-effectve routng, we get the path : S A B D havng cost 9 and lfetme 00s. Whle n LPR the path 4: S E F G D s chosen havng lfetme 40s and cost 29. For our CELP algorthm let us assume maxmum cost (C) between any two nodes s and maxmum lfetme (L) of any node s 600. So the scalng factor ξ becomes 40. Hence, usng CELP algorthm the selectng parameter β for the path-, path- 2, path- 3, path- 4, path- and path- 6 are 0.36, 0.068, 0.28, 0.389, and 0.44 respectvely. So the selected path s path 6: S C B D havng cost 22 and lfetme 400. As another example, consder the scenaro shown n fgure 2. Here from source (A) to destnaton (J) there are twelve paths to reach from source to destnaton. 8 D

4 300 A B 30 E 0 D J F 30 G I H Fg 2: A network wth 0 moble nodes wth ther battery lfetmes Those paths are: Path : A B C F J Path 2: A D F J Path 3: A D C F J Path 4: A E H I J Path : A E H D F J Path 6: A E H D C F J Path : A E H G J Path 8: A E H G F J Path 9: A D H I J Path 0: A D H G J Path : A B C D F J and Path 2: A B C D H I J. If we calculate the total cost along each path and select the path wth mnmum cost among them, as done n cost-effectve routng, we get the path-2, havng cost and lfetme 0s. Whle n LPR the route path-4 s chosen havng lfetme 30s and cost 23. So the selected path for our proposed CELP based method s path-: A E H G J havng cost and lfetme 30. Here s a comparson tables for the path-cost and network lfetme for the 3 methods for the above two fgures. COST-EFF. LPR CELP Fgure Fgure 2 23 Table : Comparson of Path-Costs COST-EFF. LPR CELP Fgure Fgure Table 2: Comparson of Network-Lfetmes 9 We fnd that CELP s better than CLP n cost perspectve and also better than cost-effectve routng n stablty perspectve. Although CELP may selects a path wth cost lttle hgher than a path wth least cost and a path havng lttle less of lfetme than a path havng hghest lfetme, ths s acceptable consderng both the stablty and the cost-effectveness of the route. Smulaton In our dscrete event drven smulaton we used 2 nodes. The lfetme of a node may vary between and 600 whle the transmsson to neghborng nodes may vary between and. Random connectons were establshed where each node has chance to connect wth every other nodes. The smulaton was run for 2000 tme unt. Nodes followed random vewpont moblty model. Each packet relayed or transmtted has a cost factor and ths cost s consdered as the cost at the transmtter node. 6 Concluson A cost effectve lfetme predcton (CELP) based routng protocol for moble ad hoc networks that ncrease the network lfetme and performance, was presented n ths paper. Smulaton results show that the proposed "Cost Effectve Lfetme Predcton (CELP)" protocol can ncrease the network lfetme up to 2%. In the prevous works, whle they are tryng to ncrease the lfetme of the network, they just consdered the battery power of the moble devsed. They ddn t consder the dstance that the selected route covered. So most of the tme, t has chosen the longest path to maxmze the network lfetme. Here securty may be hampered due to the longest dstance from the source to the destnaton. Our proposed method has cut the dstance short whle ncreasng network lfetme. References: [] M. Malek, K. Dantu and M. Perdram, Lfetme Predcton Routng n Moble Ad- Hoc Networks, proc. Of IEEE Wreless Communcaton and Networkng Conf., Mar, [2] J. E. Weselther, G. D. Nguyen and A. Ephremdes, On the Constructon of Energy- Effcent Broadcast and Multcast Trees n Wreless Networks, Proc. of IEEE Infocom 2000, March 2000.

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