Journal of Engineering Science and Technology Review 6 (5) (2013) Research Article

Transcription

1 Jst Joural of Egirig Scic ad Tchology Rviw 6 (5 ( Rsarch Articl JOURAL OF Egirig Scic ad Tchology Rviw Smart Bas Statio Ata Prformac for Cllular Radio Systm R.Ghayoula *,,, A.Smida, A.Gharsallah ad D. Grir Uit of Rsarch i High Frqucy Elctroic Circuits ad Systms, Faculty of Mathmatical, Physical ad,atural Scics of Tuis, Tuis El Maar Uivrsity, Campus Uivrsitair Tuis - El Maar 9, Tuis, Tuisia Dpartmt of Elctrical ad Computr Egirig, Laval Uivrsity 65, Avu d la Médci, Québc (QC, Caada, GV A6 Rcivd 7 April 3; Accptd 5 Dcmbr 3 Abstract Adaptiv array ata tchology is usful for dtctig th Dirctio of Arrival (DOA of sigal ad dlay for mobil commuicatios, whr th ata bam will automatically dirctd to th sigal sourc. O mthod to stimat DOA ad dlay ffctivly is by usig MUSIC (Multipl Sigal Classificatio algorithm. Wh th sigal arriv at th ata, th MUSIC algorithm will arrag th sigal ito its matrix covariac, ad th prform a ig dcompositio procss to produc th sigal ad ois subspac, ad th obtai th powr spctrum ad dlay spctrum. This papr combid th Taguchi mthod ad MUSIC algorithm, usd thm as th prdictio tool i dsigig paramtrs for th commuicatio systm ad th costructd a st of th optimal paramtr aalysis flow ad stps. Svral adaptiv bamformig critria wr discussd ad a gral form for th optimum array wight vctor was drivd that would rquir larg amouts of computatioal load. Hc, it is cssary to fid tchiqu that ca fid optimum solutio i ral tim. This papr will discuss th applicatio of MUSIC algorithm for liar ad circular array ata i ordr to stimat th DOA ad dlay of various agls of lvatio ad azimuth. Kywords: Taguchi, phasd ata array, Strig bams, MUSIC, TDOA,DOA, Itrfrc ullig.. Itroductio ABASE trascivr statio (BTS is a pic of quipmt that facilitats wirlss commuicatio btw usr quipmt (UE ad a twor. UEs ar dvics li mobil phos,wll phos, computrs with wirlss itrt coctivity, WiFi ad WiMAX dvics ad othrs. Th twor ca b that of ay of th wirlss commuicatio tchologis li GSM, CDMA, Wirlss local loop, WA, WiFi, WiMAX, tc. With th advt of mobil high-spd data applicatios, it is xpctd that th dowli of 3G CDMA systms will b th limitig li as far as capacity is cocrd. Hc, it is importat to ivstigat mthods that ca icras th dowli capacity to cop with icrasig dmad. I cllular systms such as GSM or IS-95, ata arrays ca b usd at bas statios (BSs to icras usr capacity ad provid othr advatags such as improvig voic quality, xtdig battry lif i hadsts ad icrasig data trasmissio rats. Array atas hav b mployd i military systms for may yars as a coutr masur for dlibrat, high powr jammrs []. Smart ata systms ar mployd to ovrcom multipath fadig, xtd rag, ad icras capacity by usig divrsity or bamformig tchiqus i wirlss commuicatio systms []. Udrstadig of th smart bas ata prformac mchaisms for various * addrss: ridha_ghayoula_fst@yahoo.fr ISS: Kavala Istitut of Tchology. All rights rsrvd. viromts is importat dsig cost ffctiv systms ad twors. This dissrtatio focuss o th xprimtal charactrizatio ad modllig of th smart bas statio ata prformac for various propagatio viromt scarios. I [3] th author s dscribs a mobil commuicatio bas statio ata usig a gtic algorithm basd Fabry-Pérot rsoac optimizatio. Thir focal cotributio is a bamformr-powr updat algorithm basd o upli-dowli duality that covrgs to a fasibl solutio to th problm. I th sigl-cll multi-usr dowli cas, th optimality of thir algorithm was latr provd by Visotsy ad Madhow[4] ad Schubrt ad Boch[5], [6].Rctly, Wisl, Eldar ad Shamai[7] showd that th sigl cll dowli bamformig problm ca b formulatd as a scod-ordr co-programmig problm. I [8] th author s dscribs th smart ata alog with spatial divrsity usig fuzzy itrfrc systm ad ural twor (. I ordr to provid traiig for ad fuzzy logic, a hug prsoalisd traiig datast is gratd usig Gtic Algorithm. I this papr, a global optimizatio tchiqu basd o Taguchi mthod ad MUSIC (Multipl Sigal Classificatio algorithm ar applid so as to dtrmi th xcitatio cofficits ad th rsultat pattr for a broadsid discrt lmt array whos array factor will dirctly approximat th symmtrical sctoral pattr i ordr to stimat th DOA ad dlay of various agls of lvatio ad azimuth. Th implmtatio systm is dscribd i dtail, ad liar ata array xampls ar discussd to dmostrat its validity. Optimizd rsults show

2 R.Ghayoula, A.Smida, A.Gharsallah, ad D. Grir/Joural of Egirig Scic ad Tchology Rviw 6 (5 ( that th dsird array factors, a ull cotrolld pattr ad a sctor bam pattr, ar ffctivly obtaid. It is foud that ural twor is a xcllt cadidat for optimizig divrs applicatios, as it is asy to raliz ad covrgs to th dsird pattrs rapidly. Th papr is orgaizd as follows. Th sythsis problm formulatio usig Taguchi mthod is prstd i sctio II. Multilayr twors ad Bac-Propagatio Algorithm is dvlopd i sctio III. Sctio IV shows th ovl dsig of phasd ata array with th simulatio ad masurmt rsult, fially, sctio V mas coclusios. vrtical array of atas, phasd to giv a appropriat pattr. Mor commoly i cllular mobil systms, howvr, som limitd azimuth dirctivity is rquird i ordr to divid th covrag ara ito sctors. A typical xampl is show i Figur. Th choic of th azimuth bam width is trad-off btw allowig sufficit ovrlap btw sctors, prmittig smooth hadovrs, ad cotrollig th itrfrc rductio btw co-chal sits, which is th mai poit of sctorizatio.. Statmt of Problm Adaptiv array systms ca locat ad trac sigals (usrs ad itrfrcs ad dyamically adjust th ata pattr to hac rcptio whil miimizig itrfrc usig sigal-procssig algorithms. A fuctioal bloc diagram of such a systm is show i Fig ad Fig. This Figurs show that aftr th systm dow covrts th rvisd sigals to basbad ad digitizs thm, it locats th SOI usig th dirctio-of-arrival (DOA algorithm, ad it cotiuously tracs th SOI ad SOIs by dyamically chagig th wights (amplituds ad phass of th sigals. Basically, th DOA computs th dirctio of arrival of all sigals by computig th dlays btw th ata lmts, ad aftrward th adaptiv algorithm, usig a cost fuctio, computs th appropriat wights that rsult i a optimum radiatio pattr. I this sctio, a dscriptio of th systm modl usd i th simulatio ad th aalytical study is prstd... Digital Bam-Strig W prst i this sctio a lctroic platform ddicatd to th implmtatio of adaptiv array ata. Fuctioal Bloc Diagram of a smart ata systm as show i Figur. This schm mploys dirctioal atas as array lmts. Ths lmts ar placd i such a way that th combid array pattr covs th rgio of itrst. At a istat th ata with highst rciv sigal strgth is slctd by switch. O of th advatags of this systm is th computatioal simplicity; th switchig systm scas th atas ad slcts th ata with highst rciv strgth, which also rsults i highr tracig spd. Low cost advatag of this systm bcaus a dow covrtr ad a aalog-to-digital covrtr (ADC with o chal is sufficit at th rcivr sid. As th bam pattr of th sam ata. I adaptiv bamformig, wights usd for combiig th atas ca b adaptivly calculatd ad adjustd to achiv gratr prformac improvmts tha what is possibl wh usig switchd ata systms. A adaptiv bamformig bloc diagram is show i Figur x. I this Figur, th dsird sigal corrspods to a local gratd rplica of th usr's sigal obtaid usig a prdtrmid traiig squc basd o MUSIC Algorithm with Adaptiv Taguchi sythsis mthod... Cllular Radio Systm Evoluatio Th basic fuctio of macro cll bas statio ata is to provid uiform covrag i th azimuth pla, but to provid dirctivity i th vrtical pla, maig th bst possibl us of th iput powr by dirctig i at th groud rathr tha th sy [9]. If fully omidirctioal covrag is rquird, vrtical dirctivity is usually providd by cratig a Fig.. Fuctioal bloc diagram of a adaptiv array systm Objcts surroudig th BS ad MS svrly affct th propagatio charactristics of upli ad dowli chals of cllular systms. This propagatio path loss, icludig rflctio ad shadowig, tds to dgrad systm capacity. Th hight of th MS ata is ormally much lowr tha that of th surroudig buildig ad atural faturs. Furthrmor, th carrir frqucy wavlgth is also much lss tha th siz of th surroudig structurs. Du this, th MS will xpric sigificat chargs of its rcivd sigal strgth as it movis []. Fig.. A wirlss twor with sv bas-statios ad thr usrs pr cll. 39

3 R.Ghayoula, A.Smida, A.Gharsallah, ad D. Grir/Joural of Egirig Scic ad Tchology Rviw 6 (5 ( [ a( t u, a( t, u,..., ( ] A =, a t F, u F (5 [ s ( t s ( t s ( ] T l t S =,,..., (6 With g u m f. xm, m M (7 c = si φ, d (8 Fig. 3.A wirlss twor with sv bas-statios ad thr usrs pr cll. whr A ad s(t ar calld th array rspos matrix (mod matrix ad th sigal vctor, rspctivly, ad (t is th itral additiv ois vctor[]-[]. X t ad A ar grally complx. A is a Th lmts ( matrix dimsio [ M. F, d] whos colums a ( t, u ca b put i th form of Krocr products: 3. Sigal Modl ad Estimatio Algorithm 3. Multipl Sigal Classificatio Cosidr that th array ata usd for DOA stimatio is a K-lmt liar array show i Fig., ad also that it rcivs L (L < K arrow-bad wavs whos rspctiv DOAs ar θ, θ,..., θl ad complx amplituds ar s ( t, s ( t,..., s L ( t. Wh th array rspos vctor (mod vctor of th lth icomig wav is giv by a( θ l ( l = ;;...; L, th array iput vctor x(t ca b xprssd as x d ( t s. a( t, u = = ( t A s + x =. + ( x L ( t a( θ s ( t + ( t = As( t ( t = l = l l + Wh x(t ad (t ar colum vctors of siz [MF, ] (M: umbr of atas ad F: umbr of frqucy poits, ad a matrix A with dimsios [MF, d] whos colums ar th vctors a(t,u, d dfid by: a( t, u = π.( f t g. π.( f t g. F F F M M ( (3 d (4 a( t, u = au ( u at ( t whr a u( u =. π. g. u. π. g m. π. g M at ( t =. π. f. t. π. f. t. π. f. t f F ad, d Th th colum is a ow fuctio of th dirctio of arrival ad rlativ tim dlay of th th path. a, m M, Th sam lmt of th vctor ( u u dpds o th rlativ positio of th sam ssor, th fth, f F, dpds o th fth lmt of th vctor a t ( t frqucy. 3.. MUSIC Algorithm Th most commo tchiqus for DOA stimatio ca b distiguishd btw spctral basd ad paramtric algorithms. Spctral basd algorithms us a fuctio, calld psudo spctrum, i which th maxima giv a idicatio of th DOAs. A larg umbr of spctral basd solutios hav b proposd i litratur, such as th Bartltt mthod, th Capo stimat, th liar prdictio mthod, th maximum tropy mthod ad may othrs [37]. A simpl ad widly adoptd tchiqu is th MUltipl SIgal Classificatio (MUSIC algorithm, which xploits th ig structur proprtis of th array corrlatio matrix [38]. MUSIC (stadig for multipl sigal classificatio is grally usd i sigal procssig problms as a mthod for stimatig th idividual frqucis of multipl-harmoic sigals. This is also th most frqutly studid i th (9 4

4 R.Ghayoula, A.Smida, A.Gharsallah, ad D. Grir/Joural of Egirig Scic ad Tchology Rviw 6 (5 ( litratur, vidtly with MUSIC s []-[3]-[4] ad [5]. Th MUSIC algorithm is th high-rsolutio mthod basd o th igvctors of th covariac matrix of th array iput vctor. Th covariac matrix is giv by [ ] whr S = E [s(t s(t ]ad σ Rxx = E x(t x H (t = ASAH + σ I H ( Similarly, Fig.6 shows th array factor obtaid usig th = atas; this Figur shows th bam pattrs sythsis by Taguchi Mthod wh th AOA of th icomig sigal is chagd btw 6 ad -5. Agai, AOA is corrctly foud by th sythsis wights. So from ths rsults, w ca prdict sythsis wights. Fially, this mthod prst a good bam scaig prformac with th gai variatio is blow 3dB withi th bam scaig volum is th powr of itral ois. Th, th MUSIC spctrum is xprssd as 8 6 H a (t, u.a (t, u M.F a (t, u H.w 4 = d + a (t, u = M.F ( DOA (dgrs PMUSIC (t, u = a (t, u H.w -8 = d + PMU (θ = a(θ H a(θ ( a(θ H E EH a(θ Rlativ Dlay(s Fig. 5. Tomography imag with SR = 3.68 ad agls 4, -3 ad@ -5. Tim dlays (s, 3s, 7s, s, 7s ad 35s with atas E = [L +,..., K ] whr E is composd of th igvctors: {L +,..., K } spaig th ois subspac of th covariac matrix Rxx. MUSIC : DOA with corrltd sourcs with Dg Dg AOA (dgrs Rtard rlatif (s -.5 Rcivd Powr (db Fig.6. Radiatio pattr of lmts λ/ spacd array optimizd usig Taguchi. Rcivd powr (db 3.3. Rsults ad Discussio I this sctio, computr simulatio rsults ar providd to assss th prformac with MUSIC Algorithm with diffrt agls (AOA ad Tim of arrivals (TDOA. Th MUSIC algorithm is implmtd i MATLAB ad tstd by givig diffrt agls as iput to th systm. I this xampl, w show th TOA ad th DOA simulatio rsults i azimuth ad i lvatio pla by usig a Matlab cod. Th simulatio prformd is basd o th us of MUSIC algorithm. Figs. 4 ad 5 show th MUSIC spctrum for uiform liar array with lmts ad SR=3.6 db, K= for dirctio of 4,, -, -3 ad -5 dgrs. Spacig btw lmts is assumd to b.5λ with tim dlay TDOAs=, 3, 7,, 7 ad 35 s ad Tim dlay TDOAs =, 35 ad s i Fig.7. Fig. 7. Psudo spctrum with SR = 3.68 ad agls 35,,, -45 ad@ DOA (dgrs Rlativ Dlay(s Fig. 4. Psudo spctrum with SR = 3.68 ad agls 4, -3 ad@ -5. Tim dlays (s, 3s, 7s, s, 7s ad 35s with atas 4. Elctromagtic Optimizatio Usig Bamformig Taguchi-Music Algorithm Hybrid Th radiatio charactristics of atas hav mostly to do with th far fild rgio. I this rgio, th fild xprssio 4

5 R.Ghayoula, A.Smida, A.Gharsallah, ad D. Grir/Joural of Egirig Scic ad Tchology Rviw 6 (5 ( is a multiplicatio of two parts. O part cotais th distac r dpdc of th obsrvatio poit ad th othr cotais its sphrical coordiat agls θ ad φ dpdc. Th agular distributio of th fild is idpdt of th distac r. For a typical ata lmt, th far lctric fild is E jβr f (3 4πr ( r jϖµ ( θ, ϕ Th agular-dpdt vctor f (θ,φ givs th dirctioal charactristics of th th lmt lctric fild [7]-[8]: f ( θ, ϕ I f ( θ, ϕ = (4 f (θ,φ is calld th pattr fuctio of th lmt ad I is th complx xcitatio of th th lmt of th array. E jβr jβr cosξ ϖµ I (5 4πr ( r j f ( θ, ϕ = Whr r = distac of th obsrvatio poit from th origi π β = th fr spac wav umbr λ ω = th agular frqucy ad µ = th magtic prmability of th spac (r, θ, φ ar th sphrical coordiats of a covit rfrc poit of th th lmt ad cos ξ + ( ϕ ϕ cosθ cosθ = siθ siθ cos (6 4. Taguchi Optimizatio Mthod I Fig.8, vry stp i th flowchart will b grally xplaid, ad th thy will b applid o som xampls to show th fficicy of this tchiqu. sythsis valus ad Tabl II (amplitud valus hold th optimum valus of th phas ad amplitud obtaid usig Taguchi's mthod (aftr itratios. A Laptop with Itl Cor (TM Duo CPU@. GHz ad.96 Go RAM wr usd for simulatig th Taguchi's cod, ad th simulatio tim was oly scods. a.. Iitializig th Problm a.. Dsigig Iput Paramtrs Usig a OA (max mi LD = (7 s + whr "max" ad "mi" ar th uppr ad lowr bouds of th optimizatio rag, rspctivly. a.3. Coductig Exprimts η = log( Fitss ( db (8 Aftr coductig all th xprimts ad fidig th fitss valus ad th corrspodig S/ ratio, a rspos tabl is built by avragig th S/ for ach paramtr ad lvl m usig [9]-[]. η ( m, = ηi (9 i, OA( i, =m a.4. Idtifyig Optimal Lvl Valus ad Coductig Cofirmatio Exprimt a.5. Rducig th Optimizatio Rag If th trmiatio critria ar ot satisfid, th optimal lvl for th currt itratio will b th ctr of th xt itratio. i+ ϕ = ϕ opt i ( Also, th optimizatio rag for th xt itratio is miimizd by multiplyig th currt lvl diffrc by th rducig rat (rr q.5. rr ca b st btw.5 ad accordig to th problm [3]. So, for th (i+ th itratio []-[3]. LD i i + = RR( i LD = rr LD ( Whr RR (i = rr i is calld th rducd fuctio. a.6. Chcig th Trmiatio Critria LD i + covrgd valu ( LD Fig. 8. Flow chart of Taguchi mthod []-[3] I this xampl, Taguchi's optimizatio mthod will b applid o a -lmt liar array. Tabl I (Phas Usually, th covrgd valu ca b st btw. to. dpdig o th problm. If th dsig targts ar achivd or Eq. is satisfid, th optimizatio procss will fiish. Fially, th abov stps ar rpatd util a spcific trmiatio critrio is achivd or a spcific umbr of itratios ar rachd. 4. Liar ata array Usually, i th dsig of a ata array, som costraits, such as th SLL, th FBW, th HPBW ad th dirctivity, 4

6 R.Ghayoula, A.Smida, A.Gharsallah, ad D. Grir/Joural of Egirig Scic ad Tchology Rviw 6 (5 ( ar spcifid, whil othrs, such as th phas/amplitud of th lmts, th umbr of radiators ad th gomtry of th array, must b proprly drivd to satisfy th dsig rquirmts. Which has = qually spacd lmts alog th axis x. Th lmt spacig is half-wavlgth ad th xcitatios of array lmts ar symmtric with rspct to th axis y. Th xcitatio amplitud of th fiv lmts will b optimizd i th rag of (, to shap th ata pattr. For a lmt symmtrical array, th array factor ca b writt as []-[]-[]: E E jβr (3 4πr ( r jϖµ f ( θ, ϕ AF( θ, ϕ ( r jϖµ f ( θ, ϕ A = jβr 4πr jϕ ( ( [ ( ] cos d cosθ (4 whr is th wav umbr; A(, d (=λ/, ad ϕ( = ar th xcitatio amplitud, locatio, ad phas of th th lmt, rspctivly. Th followig fitss fuctio ca b usd i th optimizatio. fitss = mi(max{ log AF( θ} (5 Th array factor ca b writt as AF jϕ ( ( ( θ = A cos[ d( cosθ ] 5 = (6 ordr to obtai a Coctric Rig Array (CRA. This plaar gomtry abls th scaig i both azimuth ad lvatio plas [35] [36]. Lt us first ma som lmtary obsrvatios of th diffrcs btw liar ad circular arrays. For th liar array i Fig., th radiatig lmts ar idtical, with qual spacig d, ad thy all poit i th sam dirctio. Th far-fild radiatio fuctio is [5]: E jr, (7 r ja siθ cos ( ( ϕ ϕ r θ, ϕ = V = Whr, V is th xcitatio amplitud of lmt is th propagatio costat, = π / λ ϕ = π ( =Agular positio of th lmt I gral, th xcitatio cofficit of th th lmt ca b writt as V ja = I (8 Whr I = Amplitud xcitatio o th th lmt, a = Phas xcitatio (rlativ to th array ctr of th th lmt. E jr = (9 r ( r, θ, ϕ [ AF ( θ, ϕ ] Fig.9. Gomtry of a ata array with idtical lmts Fig.. Gomtry of Circular ata array with idtical lmts 4.3 Circular ata array Aothr commoly mployd cofiguratio is th Uiform Circular Array (UCA, i which th lmts ar rgularly arragd o a circular rig (Fig..6. Th UCA is of vry practical itrst ad is oft adoptd i radar ad soar systms as wll as i cllular bas statios. Bsids, a dirct compariso btw a UCA (Uiform Circular Array ad a ULA (Uiform Liar Array shows that, adoptig th sam umbr of lmts ad th sam spacig btw adjact radiators, th circular array producs arrowr mai bams with rspct to th corrspodig liar array. Th prformac of th circular cofiguratios ca b improvd by usig multipl rigs i Thus, th radiatio fuctio for th focusd, circular cas bcoms AF, = [ + ] (3 a j R siθ cos ( I ( φ ϕ θ ϕ = With th circular array, w ca similarly impos phas valus to ach lmt so that thy add up cohrtly i th dirctioθ. W gt th propr phas xcitatio for ach lmt by choosig [6]-[7]-[8]. 43

7 R.Ghayoula, A.Smida, A.Gharsallah, ad D. Grir/Joural of Egirig Scic ad Tchology Rviw 6 (5 ( ( θ α = Rsiθ cos, ϕ (3 Thus th array factor ca b writt as AF [ ] jr siθ cos ( ( ϕ ϕ siθ cos( ϕ ϕ = I θ, ϕ = = I = jr [ cosψ cosψ ] (3 For coformal arrays, th lmt pattr plays a importat rol i th array pattr, bcaus ach lmt is facig a diffrt dirctio. Which has qually spacd lmts. Th lmt spacig is half-wavlgth ad th xcitatios of array lmts ar symmtric with rspct to th axis y. Th xcitatio amplitud of th fiv lmts will b optimizd [9]-[] i th rag of (, to shap th ata pattr. O of th major advatags of array atas is that th array xcitatio ca b closly cotrolld to produc xtrmly-low-sid lob pattrs or vry accurat approximatios of chos radiatio pattrs. May itricat procdurs hav b dvlopd for sythsizig usful array factors. Ths mthods fit ito thr mai classs of sythsis: sythsis of various sctor pattrs that ar usually may bam widths wid, sythsis of low-sid lob, arrow-bam pattrs, ad procdurs that optimiz som array paramtr, such as gai ad sigal to-ois ratio, subjct to som costrait o th sid lob lvl or th xistc of outsid ois sourcs. To illustrat th ffctivss of th proposd approach, two xampls ar prstd hr. I th xampls, th Taguchi optimizatio tchiqu is carrid out i t rus of itratios ach. For ths two xampls, th CPU tim for itratios is about 6.5s usig MATLAB softwar o a Itl(R Cor (TM i3-37m GHz PC. I this xampl (#, Taguchi's optimizatio mthod will b applid o a -lmt liar array (xampl #. Tabl III holds th optimum valus of th amplituds obtaid usig Taguchi's mthod (aftr itratios. I this sctio, Taguchi algorithm is implmtd for th qually spacd symmtric circular array. Th problm is to optimiz th amplituds of th lmts to achiv miimum SLL or/ad with ull placmt. For this ata arrays, diffrt umbrs of lmts ar ta. Th amplituds of th lmts allowd to vary btw [; ]. Th otatio OA is usd to rprst a orthogoal array []. To hlp radrs udrstad th OA dfiitio, Tabl I shows a orthogoal array OA(7,, 3,, which has 7 rows ad colums. Each try of th array is slctd from a st s={,,3}. Thus, this is a thr-lvl orthogoal array. choos ay two colums, ad o may s i possibl combiatios as a row []-[3]: (,, (,, (, 3, (,, (,, (, 3, (3,, (3,, (3, 3. It ca b asily provd that ach combiatio appars xactly th sam umbr of tims as a row, i.., thr tims[4]-[5]. I this sctio, w cosidr a circular array of isotropic lmts spacd.5λ apart i ordr to grat two bams towards th with amplitud-phas sythsis by Taguchi mthod. Bcaus of symmtry, hr oly fiv phass ad fiv amplituds ar to b optimizd. Accptabl Sid Lob Lvl (SLL should b qual to or lss tha th dsird 4dB. W oft wat that th sid lob lvl is as low as possibl. W shall apply th optimizd wights bfor, th amplituds to miimiz thm ad th phass to dirct th mai lob. Wh this optimizatio procss has b xcutd for itratios, a optimal cotrol pattr is obtaid ad prstd i Fig..Taguchi mthod was usd to adjust th positio ad th xcitatio of ach lmt i th circular array to obtai bttr sid lob supprssio. Tabl. Th OA(7,, 3,, Fitss Valus, Ad S/ Ratios I Th First Itratio Of Th ull Cotrolld Pattr Optimizatio Exprics Elmt # V V V3 V4 V5 fitss RS Tabl.. Rspos Tabl i th First Itratio of ull Cotrolld Pattr Optimizatio Elmt (db V V V3 V4 V5 Lvl Lvl Lvl W hav prstd a pattr sythsis mthod of uiform circular ata arrays for simultaous rductio of th sid lob lvl, rquird smallr circumfrc ad arly symmtrical pattr. Th rsult shows th circular ata array radiatio pattr th Sid Lob Lvl (SLL is db. Th optimizd xcitatio magituds of lmts ar listd i Tabl III. To apprciat th fficicy of Taguchi s mthod, th covrgc curv of fitss valu is plottd i Fig.. It is obsrvd that th fitss valu covrgs to th optimum rsult quicly. Rsults clarly show a vry good agrmt btw th dsird ad sythsizd spcificatios. Th Taguchi mthod i xampl (# usd to obtai th voltags (Amplitud ad phas corrspodig to th spcifid ar fild distributio. Th rsultig voltags, listd i Tabl II ad prst th optimizd lmt xcitatios of th circular ata array with a sctor bam pattr show i Fig.. Th optimizatio rags of th xcitatio magitud ad phas of ach lmt ar from zro to o ad from to, rspctivly. Eq.( is usd for valuatig th fitss valu durig th optimizatio procss. Th covrgd valu is st to. ad th RR is st to.9.[]. 44

8 R.Ghayoula, A.Smida, A.Gharsallah, ad D. Grir/Joural of Egirig Scic ad Tchology Rviw 6 (5 ( Fig.. Radiatio pattr for = usig th Taguchi rsults as compard to th uiform rsults For th xt xampls (# ad #3, w ta a array with 4 lmts, i amplitud-phas sythsis, th dsig of this array is basd o fidig th amplitud ad phas distributio of ach lmt, i th pla φ=9, th SLL is st to -8dB (xampl #, ad th SLL is st to -7 db (xampl #3. So to illustrat th prformac of th mthod dscribd i th arlir sctio for strig sigl ad multipl bams i dsird dirctio by cotrollig th amplitud ad phas xcitatio of ach array lmt, xampls of Taguchi xcitd circular array with = 4, o-half wavlgth spacd isotropic lmts wr prformd with th mai bam poitig at 8 dirctios. Fig.4 ad Fig.5 show a sythsis radiatio pattr with Taguchi mthod, which illustrats th abov discussio o how th bam is strd to a dsird agl θ startig from Fig. 3. Covrgc curv of Sid Lob lvl rductio of th - lmt qually spacd liar array for th cotrolld pattr dsig with Taguchi Mthod. Tabl. 3. Sythsizd Voltags, Exampl # Elmt # Amplitud Elmt (db Phas (dg. T util T 8 ( θ =,,, 3, 4, 5, 6, 7, 8, 9,,,, 3, 4,5, 6, 7,8. Fig. 4. Radiatio pattr for = 4 usig th Taguchi rsults xampl# Fig.. Covrgc curv of th fitss valu of th -lmt qually spacd liar array for th cotrolld pattr dsig. Th rsults of strig bam i th dirctio of th dsird sigal ar prstd i Figs 3 ad 4 with th covrgd valu is st to. ad th RR is st to.9; this rsult is obtaid aftr itratios. This proprty of th proposd dsig abls to choos th siz (ara of th rgio to b covrd by th mai bam whil pig radiatio i th othr dirctios blow a dsird lvl. Fig.7 givs th computd lmt phass by Taguchi mthod (xampl#3. Fig.5. Radiatio pattr for = 4 usig th Taguchi rsults xampl#3 45

9 R.Ghayoula, A.Smida, A.Gharsallah, ad D. Grir/Joural of Egirig Scic ad Tchology Rviw 6 (5 ( Fig. 6. Covrgc curv of Sid Lob lvl rductio of th 4- lmt qually spacd liar array for th cotrolld pattr dsig with Taguchi Mthod (xampl#3. Fig. 7. Optimizd lmt xcitatios (Phass of th circular ata array by Taguchi mthod (xampl#3 I this sssio, th Taguchi mthod was usd to adjust th positio ad th xcitatio of ach lmt i th circular array to obtai bttr sid lob supprssio. W hav prstd a pattr sythsis mthod of circular ata arrays for simultaous rductio of th sid lob lvl, rquird smallr circumfrc ad arly symmtrical pattr. Array pattrs obtaid from Taguchi rsults ar grally bttr tha thos prstd i [9] which wr obtaid usig GA. At th prst tim, w ar ivstigatig th applicatio of th PSO mthod to optimiz th sid lob lvl of coctric circular arrays [33]-[34]. Tabl. 4. Sythsizd Voltags, Exampl #3 Elmt # Elmt (db Amplitud &4.35 &3.57 3&.66 4&.64 5&.9 6&9.5 7& & & &5. &4.977 & COCLUSIO I this papr, w propos a hybrid optimizatio approach that combis th MUSIC (Multipl Sigal Classificatio algorithm with Taguchi's mthod. I adaptiv array smart ata, to locat th dsird sigal, various DOA stimatio algorithms ar usd. Most of th DOA stimatio algorithms ar applid i th ata array assumd to b isotropic poit sourcs which ar impractical. Th simulatio rsults illustrat that th MUSIC ad Taguchi mthod for DOA stimatio ca b applid o ral tim with array lmts. May umrical xampls wr itroducd to masur th prformac of th both algorithms ad thir ability to rsolv icomig sigals accuratly ad fficitly. Th prformac of th MUSIC algorithm dpds o th umbr of th data sapshots. Th MUSIC algorithm has highly accurat ad stabl ad provids high agular rsolutio. Th advatag of Taguchi's optimizatio tchiqu is th ability of solvig problms with a high dgr of complxity usig small umbr of xprimts i th optimizatio procss. Taguchi's mthod is asy to implmt ad covrgs to th dsird goal quicly. To dmostrat this tchiqu, a liar ata array is optimizd to raliz a ull cotrol pattr ad a sctor bam pattr. Rfrcs. P.R.P. Hool ad D.Phil.Oxo Smart Atas ad Sigal Procssig for commuicatio,biomdical ad Radar Systms, ayagy Tchological Uivrsity, WIT Prss Southampto, Bosto,.. S. Bllofior t al., Smart ata systm aalysis, itgratio ad prformac for Mobil Ad-Hoc twors (MAET s, IEEE Tras. Atas Propagat., vol. 5, pp , May. 3. D. Kim, J. Ju, ad J.Choi, A Mobil Commuicatio Bas Statio AtaUsig a Gtic Algorithm Basd Fabry-PérotRsoac Optimizatio, IEEE Tras. o Atas ad Propagatio, Vol. 6, o., pp53-58, Fb. 4. E. Visotsy ad U. Madhow, Optimal bamformig usig trasmitata arrays, Proc. IEEE Vh. Tchol. Cof., vol., pp ,Jul M. Schubrt ad H. Boch, Solutio of th multiusr dowli bamformigproblm with idividual SIR costraits, IEEE Tras. Vh.Tchol., vol. 53, pp. 8 8, Ja Itrativ multiusr upli ad dowli bamformig udrsir cotraits, IEEE Tras. Sigal Procss., vol. 53, pp ,Jul A. Wisl, Y. C. Eldar, ad S. Shamai, Liar prcodig via coicoptimizatio for fixd MIMO rcivrs, IEEE Tras. Sigal Procss.,vol. 54, o., pp. 6 76, Ja T.S. Ghous Basha, G. Aloysius, B.R. Rajaumar, M.. Giri Prasad, P.V. Sridvi, A costructiv smart ata bam-formig tchiqu with spatial divrsity, IET Microwavs, Atas & Propagatio, Vol. 6, pp , 9. Costati.A.Balais, Modr Ata Hadboo, Joh Wily ad Sos, Ic, USA, pp , 8.. M. Chy, Th liar samplig mthod ad th MUSIC algorithm, Ivrs Problms, 7 (, pp A. Kirsch, Th MUSIC algorithm ad th factorisatio mthod i ivrs scattrig thory for ihomogous mdia, Ivrs Problms, 8 (, pp C. Bcma, B. Lidmar, Th Evolutio of Bas Statio Atas for Mobil Commuicatios, Itratioal Cofrc o Elctromagtics i Advacd Applicatios 7, Torio, Italy, pp. 85 9, 7- Sptmbr 7. 46

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