Delivering a Backup File Using Beamformer Antenna for Partially Failed Nodes in a Clustered Distributed Systems for Tolerating Faults

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1 ISSN , England, UK Jurnal f Infrmatn and Cmputng Scence Vl. 5, N. 2, 21, pp Delverng a Backup Fle Usng Beamfrmer Antenna fr Partally Faled Ndes n a Clustered Dstrbuted Systems fr Tleratng Faults Amare Tefer 1, Yu L 2, 1 Department f Electrncs & Infrmatn Engneerng, Huazhng Unversty f Scence and Technlgy, Wuhan, Chna 2 Department f Electrncs & Infrmatn Engneerng, Huazhng Unversty f Scence and Technlgy, Wuhan, Chna (Receved March 22, 21, accepted March 28, 21) Abstract. Ths paper addresses the prblem f delverng backup fle fr tw r mre partally faled ndes at the same tme n a cluster. The desgn bjectve s t mnmze the maxmum transmt pwer f a backup server and enhance the speed f backup fle delverng n allwable tme span by utlzng smart antenna and clusterng scheme fr fault tlerance dstrbuted systems. In ths wrk we prpse Matched Flter (MF), Mnmum Varance Dstrtn less Respnse (MVDR), Mnmum pwer dstrtn less respnse (MPDR), and Mnmum Mean Square Errr (MMSE) beamfrmers t track partally faled ndes n a cluster n rder t delver backup fle fr tw r mre ndes at the same tme. We have dne ur smulatn usng MATLAB t shw cnvergence f beam accrdng t the number f partally faled ndes n a cluster wth Sgnal t Nse Rat (SNR), t shw ur prpse prtcl that s needed fr cmmuncatn amng backup servers, backup server wth partally faled ndes n a cluster and master backup wth agent backup servers and have nvestgated the perfrmance f ur channel mdel fr dfferent scenars. Keywrds: Dstrbuted Systems, Backup Server, Drectnal Antennas, Smart Antennas, Clusterng, capacty. 1. Intrductn Clusterng n Dstrbuted Systems (DS) may address many bjectves, such as effectveness, fast mantenance wth tleratng f faults, mblty awareness, and lad balancng. The gal f effectveness can be acheved by grupng all ndes n the netwrks wth a small number f cluster backup servers. Ths leads t a smple and stable cluster backbne, whch facltates and gves servce t the ne whch needs backup fle wth tlerable delay [1]-[6]. Therefre, a hgher number f smultaneus transmssns culd be sustaned by the backup server. Beamfrmer antennas have the ablty t cncentrate the radated pwer twards the ntended drectn f transmssn and pssble t delver dfferent types f backup fle at the same tme fr s many partally faled ndes n a cluster usng dfferent Carrer frequency. As a result, they can help reduce the amunt f radated pwer necessary t reach a nde, and thus greatly mprve the energy effcency f Dstrbuted System prtcls [7]-[14]. The rest f ths paper s rganzed as fllws. In the next sectn, we dscuss ur prpsed scheme n sectn 2. In sectn 3, s presented channel mdel n the tme span f delverng backup fle. In sectn 4, the needed perfrmance results are dsplayed. Fnally, n sectn 5, we cnclude the paper and the last but nt the lst s the acknwledgement f ths wrk s mentned. 2. Prpsed Scheme Crrespndng authr. Tel.: ; fax: (86) E-mal address: [email protected], [email protected]. Publshed by Wrld Academc Press, Wrld Academc Unn

2 1 Amare Tefer, et al: Delverng a Backup Fle Usng Beamfrmer Antenna fr Partally Faled Ndes Assumptns: All dead ndes may nt be cnsdered at all. All member ndes n the netwrk are smlar n transmssn Pwer. All backup servers n the netwrk have the same transmssn level Smart Antenna Mdel [1][3] We assumed that a transmtter (backup server n a cluster) s fxed and the recevers are mvable. All the sgnals arrvng frm the dfferent antenna elements t the recever are added tgether and radated t the pstn where the recever fund. Hwever, snce the elements are separated by dstance, the phase f the dfferent sgnals s dfferent. Let the sgnal s (t) represent the sgnal arrvng at the dfferent antenna elements and let w dente the phase and gan that s added t each sgnal s (t). z (t) s the utput sent t the recever and d s dstance between elements dentng the phase and gan that s added t each sgnal. Then, the utput sent t the recever, can be wrtten as: z( t) A M 1 w S ( t) N A M 1 w s ( t) e jd cs Where β=2 / s the phase prpagatn factr, λ s the wavelength, and A s an arbtrary gan cnstant. The weght w s used t shft the phase f the sgnal wthut varyng the ampltude. The representatn fr the weght s: j d sn s w e (2) 2.2. Prtcl Desgn Cluster wll be frmed accrdng t [1]. Aback-up cluster head wll be selected n each cluster [1]. Partally faled Ndes that wsh t get backup fle frm Backup Server n a cluster frst send an Omndrectnal Request-T-Send (RTS) packet. A Back-up-Server that receves Request-T-Send (RTS) crrectly can d Drectn-Of-Arrval (DOA) estmatn usng ne f the beamfrmer mentned belw and wll send a backup fles t all ndes that send an RTS t t. In the meantme, nde A frm recevng backup fle packet wll prceed t transmt acknwledgement data packet n the antenna facng the drectn twards Backup Server. The master wll nmnate agent backup servers nearer t t [1]. Cmmuncatn wll be cntnued amng cluster heads, cluster backup heads wth master backup. The prtcls whch are utlzed t determne DOA n ur scheme are:- 1. MF Algrthm (Matched Flter). 2. MVDR Algrthm (Mnmum Varance Dstrtn less Respnse). 3. MPDR (Mnmum Pwer Dstrtn less Respnse). 4. MMSE (Mnmum Mean Square Errr) Physcal Mdel (Antenna Sgnal t nterference Rat (SINR) [15] All ndes are assumed t be equpped wth a lnear array antenna cnsstng f N elements, and chse a cmmn pwer P. Let {X k : kt} be the subset f ndes smultaneusly transmttng at sme tme nstant. A transmssn frm a nde X, T, s successfully receved by nde X j(). SINR j N X kt k P a X j() P*G X X G s the average recevng antenna gan fr a randm nterferer. In the case f the lnear array antenna s I gven by I a j β N (1) (3) JIC emal fr cntrbutn: [email protected]

3 Jurnal f Infrmatn and Cmputng Scence, Vl. 5 (21) N. 2, pp π 1 sn.25πn csθ 1 GI θ π d Nsn.25π csθ 1 (4) 3. Channel Mdel 3.1. Input sgnal t the back-up server Let the number f partally faled ndes n a cluster be z transmt Request t Send (RTS) f an L-ary pulse S y (t), the cmplex ttal sgnal at the nput f back-up server s: L rt () KS l y( t l) nt () Sy() t nt () (5) l1 Where L s the number f partally faled ndes n a cluster and K l s the cmplex fadng ceffcent f the th l nde and Sy(t) s the receved y th sgnal. Fr a cluster whch s suffcently dense wth number f faled ndes, the brad cast f multple Request-t-Send (RTS) frm ndes wll be supermpsed and the resultng sgnal S y wll be apprxmately a nnstatnary Gaussan randm prcess: M z() m, z y( m, z) m() (6) n1 r t K S t n t 3.2. The estmated sgnal at the utput f back-up server [1] The fltered sgnal at the utput f recever wll be represented by a vectr f r(z) = S y + N(z). The Maxmum Lkelhd Estmatn (MLE) f S y s: P ˆ 1 S r( z) y (7) P 1 Let Es 2 y () t, then the Mean Square Estmatn Errr (MSE) wavefrms can be wrtten as: 2 kmax N kmax MSE E sˆy s y (8) P PSNR Where SNR=P/N. Then the recever can adaptvely update the estmatns n a decsn drected mde. We cnsdered a BPSK scheme and desgnate the centre nde as a backup server, the partally faled ndes transmttng an RTS data t fld the entre cluster. Hence, the bnary symbls ±1 are sent t a backup server. Its crrespndng cmplex wavefrm equvalent s P y (t), wth duratn Tp=(1/W) and ne-sded bandwdth, W. p () t s W sn c( Wt) (9) y y There are ther surces f errrs just as channel nse due t ndes n a cluster, neghbur clusters and ther whte and black nse n the system. If there s n errr prpagatn sgnal frm neghbur, the prbablty f errr s slely determned by the Sgnal t Nse rat (SNR): d 2E pbpsk ( E) P( m) Q Q 2 N (1) The sgnals whch are prpagated frm dfferent ndes wll change ur rgnal gaussan nse N. Nw, nstead f havng N gaussan nse varance, t becmes e N and the percentage f backup server that may experence mstakes durng detectn f sgnal becmes є. Thus, the errr varance s smply E b tmes the percentage f ndes that makes a prpagatn f errr sgnal t the back-up 2 2 server, e O z and the prpagated errr mdel becmes: 2 JIC emal fr subscrptn: [email protected]

4 12 Amare Tefer, et al: Delverng a Backup Fle Usng Beamfrmer Antenna fr Partally Faled Ndes E b (11) P( E) 2Q 2 N e 2 E b PUB ( E) 2Q 1 ( ) N 2 The wrst case scenar (near-feld), the errr prpagatn leads t an SNR degradatn f1 ( ) 2. Thus an upper bundary f the prbablty f errr be desgnated by equatn (12). Fnally, we evaluate perfrmance f the system usng dfferent scenars and the result s depcted n belw fgure 6 wth the fllwng cnsderatns shwn n Table 1. 2 (12) 4. Smulatn Part Table 1. Data fr smulatng BER vs. SNR Parameter Type r Value Mdulatn BPSK c 3 x 1 8 (m/s) BW=Bandwdth 83.5Mbps N= Number f ndes n a cluster 5 radus 1m Δt = samplng rate T p 1 1mw S y 4.1. Smulatn f Beamfrmer Antenna usng GUI f MATLAB In ths sectn we present sme sample results t shw the beam cnvergence wth ther SNR by takng the fllwng cnsderatns: The pwer fr bth Transmtter and Recever Antenna s s 1. The results are depcted n fgures belw. Intally, a recever whch needs a backup fles bradcast an Omn-drectnal RTS beam as shwn belw n Fgure 1. Fg.1: Bradcastng f Request-t-Send (RTS) packet as a beam frm frm partally faled nde n an Omn-drectnal way The next step s selectng ne beamfrmer amng the abve mentned and pressng the update buttn. The transmtter then adjusts ts maxmum pwer wth the beam cverage area twards the partally faled JIC emal fr cntrbutn: [email protected]

5 Jurnal f Infrmatn and Cmputng Scence, Vl. 5 (21) N. 2, pp nde drectn as shwn belw Fgures (Fr all dagrams, the left part f each fgure s used t represent the pstn f partally faled ndes wth mvable recevers and besdes the mddle nde s a backup server wth a target partally faled nde that has green clur). (A) Beamfrmng pattern fr Mnmum varance dstrtn less respnse (MVDR) Algrthm (B) Beamfrmng pattern fr Mnmum Pwer dstrtn less respnse(mpdr) (C) Usng Mnmum Mean Square Errr (MMSE) (D) Usng Matched Flter (MF). Fg. 2((A), (B), (C), (D)): Beamfrmng fr ne partally faled nde (A) Usng MVDR Algrthm (B) Usng (MPDR) Algrthm JIC emal fr subscrptn: [email protected]

6 14 Amare Tefer, et al: Delverng a Backup Fle Usng Beamfrmer Antenna fr Partally Faled Ndes (C) Usng Mnmum Mean Square Errr (MMSE). (D) Beamfrmng pattern usng Matched Flter (MF). Fg..3 ( (A),(B),(C),(D)): Beam pattern fr three partally faled ndes. As the number f partally faled ndes ncreases mre and mre, the beam pattern s adjusted accrdng t partally faled ndes pstn Smulatn Part f prpsed prtcl In ths sectn we present sme sample results t shw ur prpsed prtcl that needs t frm cmmuncatn amng cluster backup server ndes, cluster back-up server t partally faled ndes and master backup server t agent backup servers. 25 Master Back-up Server Befre frmatn f Cluster Fg. 4: Ndes befre havng Cluster JIC emal fr cntrbutn: [email protected]

7 Jurnal f Infrmatn and Cmputng Scence, Vl. 5 (21) N. 2, pp Cmmuncatn amng cluster back-up servers, master back-up wth agent back-up servers and back-up server wth partally faled ndes usng Beamfrmer Antenna Master back-up Nrmal Nde partally faled nde Cluster back-up (A) Cmmuncatn amng cluster back-up servers, master back-up wth agent back-up servers and back-up server wth partally faled ndes usng Beamfrmer Antenna (B) JIC emal fr subscrptn: [email protected]

8 16 Amare Tefer, et al: Delverng a Backup Fle Usng Beamfrmer Antenna fr Partally Faled Ndes Cmmuncatn amng cluster back-up servers, master back-up wth agent back-up servers and back-up server wth partally faled ndes usng Beamfrmer Antenna 25 Master 25 Back-Up Partally faled nde (C) Fg.5(A,B,C): Cluster frmatn, electn f backup Server and dentfng partally faled ndes usng the prpsed algrthm 4.3. Perfrmance Part: Channel perfrmance There are ther surces f errrs just as ndes n a cluster, neghbur clusters and ther whte and black nse n the system. Therefre, we evaluate perfrmance f the system usng dfferent scenars and the result s depcted n belw fgure 6. 1 Wth Errr Prpagatn frm neghbr f back-up server head Wth N Errr and wth n nse Prpagatn twards the back-up server wth the addtn f nse n a cluster cnsderatn f errr prpagatn frm the neghbr clusters 1-1 Prbablty f Errr SNR Threshld Fg.6: Effect f Errr Prpagatn n perfrmance Perfrmance f MVDR vs. MPDR Fnally, by varyng number f ndes, perfrmances were nvestgated fr MVDR, MPDR, MMSE and MF beamfrmers. Fgure 7 shws the result fr the effect f msmatch wth dstrtn cnstrants fr MPDR Vs MVDR prtcls. JIC emal fr cntrbutn: [email protected]

9 Jurnal f Infrmatn and Cmputng Scence, Vl. 5 (21) N. 2, pp Impulse respnse realzatns.35 MPDR MVDR.3 Anerage Out put Ampltude at the FIlters Number f Ndes 5. Cnclusn and Dscussn Fg.7 : Impulse respns realzatn at the ut put f MPDR vs. MVDR In ths paper, we nvestgated fur dfferent beamfrmers named MVDR, MPDR, MMSE and MF that are nvked fr Drectn f Arrval (DOA) Prtcl whch are used t beamfrmer n a way that maxmzes SNR. We ntce that amng all these, DOA f MVDR beamfrmer has a faster respnse than thers wth hgher beam cverage twards the revvers. We studed the mpact f usng a realstc DOA algrthm as well as the benefts f nullng. Fnally, we cmpared the SNR wth Drectn f Arrval (DOA) prtcls t Omn-drectnal antenna and bserved that t has a gan f 2x 4x hgher than Omn-drectnal Antenna. We als develped a prtcl whch s needed t frm cmmuncatn amng backup servers, cluster backup server t partally faled ndes and master backup server t agent backup servers that needs t ensure the lfe guaranty f netwrk n a fault tlerance dstrbuted systems. Ths scheme helps t shft the beam f smart antenna twards the needed ndes n the netwrk and can fasten delverng f backup fle wth a tlerable tme span wth lw transmssn pwer. It can determne the number and sze f clusters wth a mnmum number f backup servers accrdng t the fault exsted n a cluster and t the exstng traffc stuatn that selects the apprprate nde as a man backup server n each cluster. We als desgned the channel mdel and nvestgated the prblem f nterferences frm neghbur partally faled ndes, neghbur clusters and even ther whte and black nses whch may exst n the system. Reduce the backbne changes and nter-cluster mantenance verhead and can utlze the cluster stretchng mechansm t reduce the leavng rate whch affects hgher cluster-based prtcls. Fr the future research, better algrthms may be desgned usng artfcal neural netwrk fr backup server electn and dentfyng the pstn f partally faled ndes and sme theretc analyss shuld be cnducted. One culd analyze dfferent channel mdels n depth, MUSIC algrthm fr drectn f arrval estmatn and dfferent flterng schemes wth equalzers and the lkes. It s als pssble t ncrprate mre practcal cnstrants r bjectves nt the mdel and algrthms. 6. Acknwledgements We need t say thanks t the edtr f ths wrk. 7. References [1] A. Tefer and Y. L. Effcently Utlzatn f Redundancy Backup Server by Frmng Dynamc Clusterng n Dstrbuted Systems fr Tleratng Faults. Prc. f the Cnference n Sgnal Prcessng, Rbtcs and Autmatn (ICSRA 21), 21 (n press). [2] D. Gldberg., M. L, W. Ta, Y.Tamr. The Desgn and Implementatn f a Fault-Tlerant Cluster Manage. Cmputer Scence Department, Unversty f Calfrna, Ls Angeles, Oct. 21. [3] M. Treaster. A Survey f Fault-Tlerance and Fault-Recvery Technques n Parallel Systems. Natnal Center fr Supercmputng Applcatns, Unversty f Illns, 25. JIC emal fr subscrptn: [email protected]

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