Performance-Driven Resource Management In Layered Sensing

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1 h Inenaonal Confeence on Infomaon Fuson Seale, WA, USA, July 6-9, 009 Pefomance-Dven Resouce Managemen In Layeed Sensng Chun Yang Sgem echnology, Inc. San Maeo, CA 9440 Ivan Kada Inelnk Scences Sysems, Inc. Lake Success, NY Ek Blasch A Foce Reseach Lab WPAFB, OH ek.blasch@wpafb.afb.ml Absac - Layeed sensng povdes a heachcal necenc achecue fo unvesal suaonal awaeness wh global coveage and pessen suvellance. Sensos n he layeed heachy povde spaal, empoal, specal, and polazaon dvesy wh dffeen scales and esoluons ove dffeen me hozons. Coopeave managemen of need sensos s a successful saegy o acheve ageng pefomance and oveall measues of me (MOM goals. Afe a bef noducon o ssues n layeed sensos, a esouce managemen saegy based on geomey nfomaon s descbed so as o enhance pefomance n age deecon (mnmum deecable Dopple and ackng accuacy (geomec dluon of pecson. Pelmnay smulaon esuls ae pesened o llusae hs Geomec Appoach o Layeed Sensng (GALS concep. he boom laye, gound sensos can say n he same aea so long as he baey lass bu ypcally have lmed spaal coveage. Keywods: Layeed Sensng, Pefomance-Dven, Geomec Appoach, Resouce Managemen, Measues of Me (MOM Layeed Sensng Layeed sensng s amed a povdng unvesal suaonal awaeness wh global coveage and pessen suvellance [, 5]. A scenao of layeed sensng s shown n Fg. [9] wheen hgh alude plafoms affod age deecon, unmanned aeal vehcles (UAV manan aea suvellance fo age ackng, and gound sensos can povde ndvdual audo epos fo age denfcaon. Fo such a layeed sensng scenao, he need fo nellgen senso managemen (SM s llusaed va he smple space-me dagam n Fg. wheen layeed asses ae coodnaed o acheve msson success. As shown, hgh alude plafoms such as space-based ada (SBR n he op laye have wde gound swah sweepng along he ob fo global coveage. Alhough he saelle gound ack epeas egulaly, only offes sho me wndows on ages dung each evs. Alhough a fully populaed consellaon of fas movng low-eah ob (LEO saelles can mnmze empoal and spaal gaps n gound coveage, a long evs neval s no effecve n ackng of moble ages. Wh ealy deecons fom he op laye, UAVs n he mddle laye can be dspached and oued o he aeas of nees (AOI fo suvellance and ackng. In Ob Peod Fg. A Layeed Sensng Scenao [9] me op Laye Md Laye Low Laye Enduance Space Insananeous Coveage Global Coveage Fg. Space-me Coveage by Sensos n Dffeen Layes ISIF 850

2 Povded by he hgh alude laye, a long ls of deecons may conan boh ages and clue (false deecons. Confmed deecons fom lowe layes can educe he poson unceany esmaes; howeve, unconfmed deecons n he ls have ahe poo accuacy n he poson esmaes. hs nceases he complexy of senso managemen and paculaly fo sensos n he mddle laye, whch now need o acque (boh seach and deec desgnaed ages po o ackng, albe n a much educed volume. Resouces n layeed sensng nclude boh sensng asses and communcaons asses. hs pape wll focus on sensos. Senso managemen adonally consdes wo man hemes: ( senso assgnmen decdes whch senso combnaon wll be assgned o whch age ove whch aea and ( senso schedulng deemnes when and whch senso wll ake wha acon [, 3, 4, 5, 9,,, 3]. In layeed sensng, howeve, senso coodnaon and daa exchange va boh weless and wed newok communcaons play a pvoal ole n ne cenc-opeaon and neacon, whch may nvolve abone eplays and communcaons saelles. Funconaly pe laye and he neacon ae shown on he gh hand sde of Fg. 3 whee nfomaon flows fom he op laye hough he mddle laye o he boom laye and back o he op and mddle layes n a closed-loop fashon. Ealy and quck nfomaon (coase and ncomplee fom op layes gude he deploymen and execuon of lowe layes whle dealed nfomaon deved fom lowe layes may eques specal senso modes of uppe layes when flyng ove specal aeas o evs. Command, Conol & Communcaon Cene Cenalzed Managemen Dsbued Managemen wo Possble Implemenaons op Laye Sensos Deecon (ages, Clue Mddle Laye Sensos ackng (Acquson Low Laye Sensos Idenfcaon Specal Aeas Specal Modes Funconaly & Ineacon Fg. 3 Implemenaon Schemes fo Layeed Funconales and Ineacons wo possble mplemenaon schemes of he desed neacons ae shown on he lef hand sde of Fg. 3. One s he cenalzed managemen scheme whee sensos n all layes go hough he command, conol, and communcaon (C3 cene. he ohe scheme s dsbued (decenalzed managemen whee sensos n dffeen layes communcae o one anohe decly. Daa lnk bandwdh, laency, and elably ae key ssues n ne-cenc sensng. A specal aspec of senso coodnaon s age handove/cueng, whch occus beween layes and whn he same laye. One example s coelaon of acks fom sensos ha lack smulaneous coveage [6]. he cueng fom a wde feld of vew (FOV senso o a naow FOV senso, ehe co-locaed o emoely, s anohe example. Smlaly, handove of ages o a guded weapon fom s launch plafom s a hd example. Pope ne-laye and na-laye ansons ae equed o ensue coveage connuy n boh me and space. Howeve, anson n layeed sensng s moe complcaed smply because of a lage numbe of deecons wh lage unceany n addon o sevee consans on he pa of sensos and communcaon lnks avalable n me and space fo needed coveage. I becomes clea ha effcen esouce managemen becomes ndspensable. he es of he pape s oganzed as follows. In Secon, he esouce managemen saegy based on geomey nfomaon s descbed wh wo llusang examples. One example s o enhance ackng accuacy n ems of geomec dluon of pecson (GDOP whle he ohe s o enhance age deecon pefomance wh elave age-senso velocy above he mnmum deecable velocy (MDV. Fnally, he pape s concluded n Secon 3. Geomec Appoach o Layeed Sensng (GALS Layeed sensng s a mul-senso mul-age envonmen wheen a pefomance-dven saegy s amed a obanng he bes ageng esuls possble va cleve use of avalable esouces. he esouce managemen heefoe assumes he esponsbly of senso assgnmen, senso schedulng, senso daa exchange, and senso daa fuson. Fo coopeave dsbued sensos, hey can ac ogehe va communcaon lnks o mpove deecon pobably, success of classfcaon, ackng accuacy, and he especve aes. wo examples of he geomec appoach o layeed sensng (GALS ae pesened below. Example : Geomec Dluon of Pecson (GDOP as MOM Dependng on he ovelappng of mulple sensos n me, space, specum, and polazaon, he esouce manage may assgn a senso o mulple ages o have a age coveed by mulple sensos. hee ae seveal cea ha can be used o conduc senso-o-age assgnmen. One s o ensue pessen ackng of he age as oams aound, ha s, o have maxmum empoal and spaal coveage. Anohe s o ensue maxmum age deecon. A leas wo facos affec he pobably of deecon, one s he dsance fom he senso o age (he efleced sgnal powe s nvesely popoonal o R 4 whee R s he ange fom an acve senso o he age and he ohe s he 85

3 elave velocy veco. In he lae case, boh age and senso velocy vecos ae ulzed n he assgnmen pocess, whch wll be dscussed n he second example. A ceon fo maxmum accuacy s pesened n he followng example. Acve angng sensos o passve beang-only sensos ulze mulple measuemens o deemne a age s poson. Measuemens a dffeen locaons can be obaned fom dsbued sensos o fom he same senso bu a dffeen me nsans ove whch ehe he age o senso o boh have meanngfully moved. Posonng pefomance can be esmaed fom usng nonlnea (ange o beang o boh measuemens. Analogous o he mehods used n [8], assume ha he age s a x and he -h senso s a x. he -h senso s measuemen s gven by: z f ( x, x + v ( whee f (, s a nonlnea measuemen equaon and v s he senso measuemen eo beng zeo-mean Gaussan N(0,. Wh an nal esmae of he age poson denoed by x 0, he nonlnea ange measuemen can be wen as: z f x + v (a ( 0, x + h ( x x0 z z z h (b x x xn he equaon can be fuhe wen as: ~ z z f ( x0, x + h x0 h x + v (3a ~ z Hx + v (3b ~ z [ ~ z ~ z ~ zn ] (3c v [ v v vn ] (3d H h h (3e [ ] m he leas squae soluon s gven by: x ˆ ( H R H H R ~ z (4a P E {( x xˆ ( x xˆ} ( H R H (4b Assume ha all sensos have he same qualy wh R I. he soluon s hen deemned by he lneazaon max H. A scala value ha chaacezes he soluon s he geomecal dluon of pecson (GDOP defned as: GDOP ace(( H R H (5a ace(( H H when R I (5b whee ace( sands fo he ace of a max. Consde an acve senso wh angng measuemens n a wo dmensonal case as shown n Fg. 4. he nonlnea ange equaon and s lneazaon ae: f ( x, x ( x x + ( y y (6a x0 x h y y e 0 sn( θ cos( θ (6b I s clea fom (6b ha h s he lne of sgh veco fom he -h senso o he age, denoed by e. As a esul, he GDOP s only deemned by he geomey (angula elaonshp, no by he acual sepaaon (dsance fo acve sensos. he hemal nose does no depend on he senso o age ange bu he age echo sengh does. So does he esulng sgnal o nose ao (SNR and hs wll affec he equvalen measuemen covaance max R. hs has sgnfcan amfcaons n geomey-based senso assgnmen and schedulng. Assume he measuemen max H s a non-sngula squae max (a vey escve example and R s a dagonal max wh unequal dagonal elemens, whch s a funcon of SNR. hen, ( H R H ace( H n H R( H R( H ace( R( HH (7 ( HH whee he subscp sands fo he -h dagonal elemen of he max ( HH. Clealy, he conbuon of he -h senso o he GDOP s weghed by. Smla esuls fo moe geneal cases can be found n [7]. Fo he case wh wo angng sensos, GDOP can be wen as: + GDOPRange (8a sn ( θ θ +, θ θ π / (8b, θ θ 0, π + ( / (8c sn ( θ θ, (8d sn ( θ θ If we have o choose wo ou of many (say, hee sensos o fom a soluon, we need o compae all possble confguaons (hee pas n hs case, namely, Sensos { and }, { and 3}, and { and 3} n ems of he GDOP as a funcon of he senso qualy ( / and he elave poson (θ θ assumng all ohe facos ae equal. Assume ha Senso has he smalles measuemen eo and s chosen as he efeence. Assume Senso s of he same qualy as Senso ( / bu makes 40 o wh espec o Senso (θ θ 40 o. Alhough Senso 3 has he bes geomey elave o Senso wh θ 3 θ 90 o, 85

4 y n (x 0, y 0 e e n θ e n θ e n e (x, y (x n, y n e θ (x, y Fg. 4 GDOP fo Rangng and Beang-Only Sensos x gdop/ gdop vs. / & θ θ (deg 3- / /.5 / /.5 / 3 Fg. 5 Opmal Selecon of Senso Pas has he wos qualy wh 3 /. he esulng GDOP fo he pa and s GDOP,.0 whle s GDOP,3.4 fo he pa { and 3}. he opmal choce s heefoe he pa { and }, as shown n Fg. 5. Refeng o Fg. 4 agan, we now consde a passve senso wh beang measuemens n a wo dmensonal case. he nonlnea angula equaon and s lneazaon ae: y y f ( x, x θ an ( (9a x x y0 y sn( θ sn( θ e h x x 0 cos( θ cos( θ (9b Compang (9b o (6b shows ha he measuemen max h fo he beang-only senso s ange-dependen and s n fac pependcula o he lne of sgh veco fom senso o age. When he ange-dependence and angula eos ae combned n he GDOP (5, povdes a poson eo pependcula o he LOS (o along e, ha s,. Fo he case wh wo beang-only sensos, GDOP of (5 can be wen as: GDOP GDOPN Beang Beang + sn ( θ θ R (0d,, (0e sn ( θ θ θ θ π /, fo, and (0f θ θ 0, π he same esuls fo angng sensos can be appled o beang-only sensos when he coss ange eo ( beang used n (0 s eaed n much he same way as he angng eo ( angng n (8b. he pefomance cuve fo senso pa selecon as shown n Fg. s also applcable. o emphasze he geomec aspec, a nomalzed GDOP o GDOPN was noduced n [8]. I s defned as: GDOPN ace(( H R H (a R whee s an aveaged nose vaance defned as: R N R N (b Indeed, he ognal defnon assumes R I and GDOP s elaed puely o he geomey. hs woks well fo such applcaons as GPS saelles selecon above a cean + elevaon mask angle. Fo a nea Eah use, s anges o (0a sn ( θ θ mos saelles ae abou he same and he SNR does no vay gealy. As a esul, GDOP s a good choce. Howeve, +, θ θ π / (0b he dffeence n dsance o ages fom sensos n vaous, θ θ 0, π layes may be sgnfcan and so s he SNR. By consequence, he use of GDOP weghed wh + ( / (0c measuemen qualy seems o be moe useful, (0b as llusaed sn ( θ θ n Fg. 5. he GDOP defnons above nvolve he measuemen max H and he poduc of s anspose H. hs s smla o he Fshe nfomaon gan and s also elaed o 853

5 he Came-Rao lowe bound. I s of nees o fuhe nvesgae he elaonshps. A paccal poblem wh he leas squaes soluon (4 s he nably o nvese he max em H RH. hs max nvese poblem occus when he vecos of he obsevaon max H become collnea (ank-defcen, whch poduces unsable esmaes. Unde hs condon, he GDOP s excessvely hgh. Howeve, he max nvese consan condon may be used explcly fo senso assgnmen. When happens, one could ask anohe avalable senso wh nea opmum geomey. Howeve, when hee s no me o dsplace he sensos o he desed locaons, empoay means may be appled o ensue he qualy of soluon. One echnque s o apply he dge egesson (egulazed leas squaes, consaned leas squaes, o khonov egulazaon n he nem befoe he opmal dsplacemen s acheved. Rdge egesson aemps o lm he mnmum values of he dagonal values of H H by eplacng wh H H + κi n (4a [7, 0]. I s used o educe he oveall mean squaed eos and he vaance nflaed by poo GDOP a he expense of hghe bas. Explcly, he dge egesson s wen as: x ˆ ( H R H + κ I H R ~ z (a P ( H R H + κi (b hs can be vewed as he opmal soluon ha mnmzes he followng pefomance ndex: J ( ~ z Hx R ( ~ z Hx + κx x (3 I conans a measuemen eo em and a consan em on he soluon. Such a fomulaon s also efeed o he egulazed leas squaes (RLS [4]. I s also smla o he nonlnea consaned opmzaon used fo ack o oad fuson [6]. Example : Relave Moon fo Deecon n Clue One ask of senso managemen s o pu he gh sensos n he gh places a he gh mes and dong he gh pocessng. he goal of he fou ghs s o mpove age deecon pobably and sae esmaon accuacy ye wh mnmum effos (cos and me. Wh advance n need sensos and mul-npu and muloupu (MIMO ada, dsbued sensos may be coodnaed o poduce bee fuson esuls. Clealy hee ae wo lowe levels of fuson, namely, deecon o feaue fuson (classfe fuson and coodnaed pocessng and sgnal fuson (coheen and non-coheen negaon. One example of sgnal fuson s n a bsac seng whee wo adas look a he same place, one seves as he ansme and he ohe as eceve. he backscaeed sgnal a he ansme may be combned wh he fowad-scaeed sgnal a he eceve, coheenly o non-coheenly, o enhance he deecon. hs may eque one ada sendng s eceved sgnal (anslaed ono a dffeen fequency o he ohe ada. Lage bandwdh s equed fo communcaon bu only a hose ccal momens fo hghvalued ages. Bsac deecon becomes moe vable when hee ae moe eceves n he newok dwellng a he same egon of nees whee boh sgnal fuson and classfe fuson can ake place. In addon o he wo ypes of sensos dscussed n he las secon, namely, ( passve sensos wh beang-only measuemens and ( acve sensos wh ange measuemens (no o poo angula measuemens, we now consde measuemens ha depend on elave velocy along he lne of sgh (LOS decon o ages. An example s an abone gound movng age ndcao (GMI. As analyzed n he las secon, he elave geomey affecs age deecon and esmaon accuacy. hs s llusaed agan n Fg. 6. In Fg. 6(a fo passve sensos wh beang-only measuemens, he posonng accuacy depends no only on he sensos accuacy measuemen qualy and he ange o age bu also on he elave geomey of he sensos o age. Fg. 6(b shows acve sensos wh ange measuemens. Is posonng accuacy depends on he sensos accuacy measuemen qualy as well as on he elave geomey of he sensos o age. he dependence on he ange-o-age s due o SNR (paally efleced n he ange measuemen eos. Fo he hd ype of measuemens, consde he encoune geomey shown n Fg. 8 whee he ange aes due o he age moon ae gven by: V sn( θ (4a V sn( θ + θ (4b whee V s he age s velocy and θ and θ ae he vewng angles of he wo sensos elave o he age s boadsde, especvely. he ange aes n (4a and (4b specfy he Dopple fequency as seen by ndvdual sensos when hey opeae n a monosac manne (fo wo-way popagaon, a faco of wo s omed. In he bsac seng, he Dopple fequency s hen gven by: V sn( θ + V sn( θ + θ θ θ V sn( θ + cos( (5 When θ 0, (5 s dencal o (b, whch can be easly vefed fom Fg. 8. Fo a gven θ of he fs senso, he placemen of he second senso a θ s such ha he ange ae s maxmzed. he soluon can be wen as: θ + θ sgn(sn( θ (6a π θ sgn (sn( θ θ (6b π 854

6 age V sn( θ V V θ sn( θ + (a Passve Beang-Only Sensos θ (b Acve Rangng Sensos Fg. 6 Geomec Effecs on age Posonng θ o age Boadsde Senso Fg. 7 wo Sensos wh a age Senso.5.5 θ 0 o θ 5 o θ 0 o V -nomalzed ange ae V -nomalzed ange ae θ θ Fg. 8(a Monosac a θ Fg. 8(b Monosac a θ As a Funcon of θ abs of bsac dopple, nomalzed by V.4 θ 0 o θ V -nomalzed abs of bsac ange ae θ 5 o θ 0 o θ θ Fg. 9(a Bsac wh θ vs. θ Fg. 9(b Bsac as a Funcon of θ fo Seleced θ 855

7 he esul n (6b s sgnfcan. Fo he wo ypes of sensos shown n Fgs. 6(a and 6(b, he angula sepaaon s desed o be 90 o o ohogonal. Howeve, fo GMI ype of sensos, he bes angula sepaaon s he nney degees (90 o complemen of he fs senso s angula poson o he age s boadsde. ha s, o place he second senso n he decon of he age velocy. Fg. 8(a shows (4a, whch ndcaes posve and negave maxmum values a ±90 o, ha s, n he same decon o oppose o he age s velocy veco. Fg. 8 (b shows (4b fo hee values of θ 0 o, 5 o, and 0 o. he cuve s shfed lefwad and so s he peak pon. hs s conssen wh (6. Fg. 9(a shows he absolue value of (5 as a funcon of θ and θ whee he dak bown colo epesens he maxmum and he dak blue fo mnmum (zeo values. Fg. 9(b shows he hee ows of Fg. 9(a. Agan he bes placemen of he nd senso s a he peak locaon and hs agees wh (6. he above esuls affod seveal obsevaons fo managng mxed sensos. Fs, f nsuffcen nfomaon s avalable abou he age and s moon (velocy veco, he placemen of wo sensos 90 apa s a easonable choce because hs poduces good GDOP and avods he wos case Dopple deecon. Knowng he age velocy veco o s pedcon eques a sde-lookng senso o fly ove he age s pah (pependcula o. When addonal nfomaon s avalable abou one senso s vewng angle, he placemen of a second senso o moe can be made accodng o (6 so as o mpove he oveall ageng capably and esmaon accuacy. 3 Ine-Laye ansons he handoff of age nfomaon fom one laye o he mos appopae sensos n anohe laye (.e., ne-laye anson s an mpoan aspec of esouce managemen n layeed sensng as dscussed n Secon. he wo geomec appoaches pesened n Secon, namely, usng GDOP as MOM and ceang elave moon o maxmze deecon n clue, can be used o mplemen an opmal handoff scheme. he nfomaon abou a age fom one laye may be epesened n ems of he age knemac sae esmae (a ack and he esmaon eo covaance and possbly a age ID and s confdence level. Howeve, some passve sensos may only offe beangs assocaed wh a deecon and a level of qualy. Gven such a po nfomaon, whch may be pedced fowad o a fuue me o ove a me neval, he mos appopae sensos ae chosen such ha he updaed eo covaance a ha pacula fuue me o ove he fuue me neval s mnmzed. he hs secon s added based on he commens and suggesons fom hee anonymous evewes, who ae gaefully appecaed. GDOP mehod (o a smla egen analyss [7] can be appled fo hs pupose. Howeve, hs GDOP mehod assumes ha he desgnaed age can be found a he fuue updang me and hs nvolves age deecon and deecon-o-ack assocaon so as o cay ou hs nelaye anson. As a esul, a vable senso-o-age assgnmen appoach ough o ake a holsc vew n whch maxmum pobably of age deecon, coec daa assocaon, effecve poson eo educon, and mpoved age ID ae all desgn goals unde such consans as lmed enduance, ECM condons, advese envonmenal facos, and communcaons [9, 0]. In pacula, maxmzng age deecon and age ID may also nvolve adapve wavefom selecon a he same me as senso-o-age assgnmen [, ]. In addon, he concep of age value can be ulzed o poze he assgnmen of senso funcons, whch s moe opeaonal applcable. In case of oo lle esouce capacy (oveload, senso asks need o be assgned o he (opeaonally mos mpoan objecs. Assgnng values o ages s no easy ask. A leas hee faces can be consdeed: ( age ID o class, ( a age s poxmy o accal posons n he feld, and (3 a age s need fo senso updang. I s heefoe necessay o have an dea of he class a age belongs o and o deploy hose sensos ha can povde such class nfomaon (boh coopeave and noncoopeave. In fac, akng he age class no accoun could also help n opmzng he geomec aspecs (as shown n Fgs. 6 and 7 as helps o esmae he RCS/ Swelng case combnaon [8], hus yeldng a bee pedcon of he P d. Layeed sensng nvolves managng sensos ha ae spead ove a lage aea. he meeoologcal effecs canno be ovelooked. wo sensos ha have smla pefomance may yeld dffeen esuls agans he same age ype when he EM popagaon pah of one of he sensos s affeced by ducng effecs fo nsance. hese and ohe ssues ae made a pa of ou ongong nvesgaon. 4 Conclusons Whn he famewok of layeed sensng, hs pape descbed he needs, ssues, and appoaches o esouce managemen. In pacula, he geomec appoach o layeed sensng (GALS s dealed o enhance pefomance n age deecon (mnmum deecable Dopple and ackng accuacy (geomec dluon of pecson. Smulaon examples showed ha such a geomecal pefomance-based layeed-sensng appoach could be used fo senso managemen n boh senso selecon and senso schedulng. Ongong wok s focused on coopeave managemen of need sensos n a moe complex envonmen o acheve ageng pefomance and oveall msson goals. 856

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