Outline. Energy-Efficient Target Coverage in Wireless Sensor Networks. Sensor Node. Introduction. Characteristics of WSN

Transcription

1 Ener-Effcen Tare Coverae n Wreless Sensor Newors Presened b M Trà Tá -4-4 Inroducon Bacround Relaed Wor Our Proosal Oulne Maxmum Se Covers (MSC) Problem MSC Problem s NP-Comlee MSC Heursc Concluson Sensor Node Inroducon A n devce equed w: One or more sensors One or more wreless ranscevers Sorae resources We lmaon Power lmaon Relacn e baer s no feasble Wreless Sensor Newors (WSN) Sensor newor consss of auonomous sensor nodes Sensor nodes oranze n newors o collaborae on a lare sensn as Alcaons: Naonal Secur Survellance Heal care Envronmenal Monorn Ec Caracerscs of WSN Dense Dnamc Toolo Lmed Resources Crcal Issue: Power Scarc!!! Queson: How o omze e sensor ener ulzaon?

2 Wa Is Coverae Problem Gven: A feld A n sensor nodes Queson: How well can e feld be monored? Coverae Problems Can be classfed n e follown es: Area coverae: obecve s o cover an area Pon (are) coverae: obecve s o cover a se of ons (ares) Oers: obecve s o deermne e maxmal suor/breac as a raverse a sensor feld: Bes case coverae: for an on on e a, e dsance o e closes sensor s mnmzed Worse case coverae: smlar bu e dsance o e closes sensor s maxmzed Relaed Wor Dson Se Covers Dvde sensor nodes no dson ses Eac se comleel monor all ares One se s acve eac me unl ran ou of ener Goal: To fnd e maxmum number of dson ses Ts s NP-Comlee Our Proosal Our Aroac Maxmum Se Covers (MSC) Dson ses: S {s, s } S {s, s 4 } Lfeme G C {s, s, s, s 4 } R {r, r, r } Our Aroac: S {s, s } w.5; S {s, s } w.5 S {s, s } w.5; S 4 {s 4 } w 4 Lfeme G.5 Gven: C: se of sensors R: se of ares Goal: Deermne a number of se covers S,, S and,, were: os comleel covers R omaxmze + +

3 MSC Teorem: MSC s NP-Comlee Proof: Frs, defne e Decson Verson of MSC roblem. To sow a MSC NP: Gven a collecon C of subses of a fne se R, o Gven and a a number faml of, se fnd covers a faml S, of, se S covers w me wes S,,,..., S, and w e me number wes.,..., n [, ] suc o Ten a we + can verf + n and olnomal for eac me subse weer s n C, e se covers s aears mee n e S, requremens, S w a oal we of a To rove mos, e were decson e verson lfeme of eac MSC sensor. s NP-ard: o Reduce -SAT roblem o n olnomal me Problem Formulaon Usn Lnear Prorammn Aroac Gven: A se of n sensor nodes: C {s, s,, s n } A se of m ares: R{r, r,, r m } Te relaons beween sensors and ares: C { sensor s covers are r } s r C {s, s, s }; s r R {r, r, r } s r C {,}; C {,}; C {,} Varables: x f s S, oerwse x [, ], reresens e me allocaed for S Problem Formulaon MSC Heursc Maxmze subec o x s x r were x,( x ff s S Maxmze ,.., ) subec o Maxmze x s subec o x r,.., s C were x, ( x ff s S, ) r R,.., C were or and se x Inal: G. Le * * (, ), L n, L, be e omal soluon of e LP formulaed before. Frs aroxmaon can be obaned as follows: * ) Se mn max ) For eac, coose an * C s., se. Se oer ) Udae e remann lfeme for eac sensor 4) Udae e newor lfeme G G + T MSC Heursc An Examle. Ieravel reea se and b solvn s Maxmze subec o were T s C r,.., 4. Reurn G f ere s no loner an se a can cover all ares s r C {s, s, s }; R {r, r, r } s r C {,}; C {,}; C {,} s r mn max.. S {s, s } S {s, s } S {s, s } C. T. T. T. G S {s, s } S {s, s } S {s, s } T. T. T. G. G.5

4 Noaons Performance Analss Le (, ) be e omal soluon of e LP n e eraon Le mn r R C max Le or s r,, Denoe: ρ max r R C Teorecal Analss Lemma : for an eraon ρ Lemma : + for an eraon Teorem: For an eraon, G ( ( / ρ) + ), were G l l Teorecal Resuls Corollar: If MSC as an omal soluon w no more an se-covers, en and * lm G Remar: Te newor lfeme of our eursc wll convere o MSC omal soluon Concluson Concluson WSNs are baer owered. Hence, rolonn e newor lfeme s l desrable Scedule e sensor node acv o alernae beween slee and acve mode Our conrbuons: Proose maxmum covers se aroac Prove s NP-comlee Proose an effcen eursc usn a LP formulaon 4

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