I HC HU

I HC QUC GIA TP. H CH MINHTRNG H CNG NGH THNG TIN-----(((((-----

TIU LUNH THNG UWB

Gio vin hng dn: Th.S Chu Tin Dng

Nhm SV thc hin: 1. Trn Thanh Tng

2. Trn nht Tin

3. Nguyn L Hoi AnhNha Trang, 09/2015

MC LC

5I.TNG QUAN V H THNG UWB

51.1.Gii thiu v h thng UWB

6a Lch s pht trin ca UWB

7b Cc u im ca UWB

7c Nhng thch thc ca UWB

81.2.Cc thuc tnh ca h thng v tn hiu UWB

8a Mt n ph cng sut

9b Mu xung

13c Chui xung

14d a ng

17e Cc c im khc

191.3.Cc lnh vc ng dng ca UWB

221.4.Tng kt

24II.M HNH KNH V TUYN TRONG UWB

242.1.M u

292.2.M hnh knh

30a S dng m hnh

312.3.Tng kt

31III.TRUYN THNG UWB

323.1.Cc phng php iu ch trong truyn thng UWB

34a iu ch v tr xung (PPM)

36b Tng kt v cc phng php iu ch

393.2.B pht

403.3.Cc k thut a truy nhp p dng trong UWB

42IV.NH GI V H THNG UWB

424.1.Dung lng ca cc h thng UWB

454.2.So snh vi cc h thng truyn thng bng rng

514.3.nh hng nhiu qua li gia h thng truyn thng UWB v cc h thng truyn thng khc

52a Cc mng ni ht khng dy (WLAN)

53b Bluetooth

54c GPS

54d Cc h thng thng tin t bo

544.4.Tng kt

LI NI U

So vi cc lnh vc truyn thng khc, thng tin v tuyn c s tng trng nhanh chng. Xu hng hin nay l s dng cc thit b di ng truy cp cc dch v Internet tc cao. Mt trong nhng hng i ca vn ny l s dng cng ngh UWB. Cng ngh ny cho php cc kt ni v tuyn c tc cao hn hn so vi cc kt ni v tuyn khc. y l mt cng ngh mi khng ch mi Vit Nam m cn l mt cng ngh mi m trn th gii v l mt cng ngh c nhiu tim nng ng dng cao.

Vn x l tn hiu c mt vai tr ht sc quan trng trong cc h thng v tuyn no. Cng nh bt k mt h thng truyn thng no khc, vn x l tn hiu trong truyn thng UWB l mt trong nhng vn quyt nh n s thnh cng ca h thng, qua c th xem xt y hiu nng ca h thng ln cc gii hn c th. Trong ni dung n ny em s nghin cu tng quan v h thng truyn thng UWB v nh gi h thng di quan im x l tn hiu.

V ni dung n c chia thnh IV:

I Tng quan v h truyn thng UWB: gii thiu tng quan v h thng UWB, cc c tnh c bn ca tn hiu v h thng UWB t cho thy tim nng ng dng ca UWB l rt ln. Cc c im c bit quan tm ca h thng UWB l cc quy nh v ph tn ca FCC a ra. Li th v bng thng, kh nng chng a ng ca tn hiu UWB lm tn hiu UWB tr ln rt hp dn i vi lnh vc vin thng. Ngoi ra cc c tnh khc ca tn hiu UWB nh kh nng m xuyn, nh v lm lnh vc ng dng ca n tr nn rt rng v linh hot.

II M hnh knh cho UWB: trnh by mt m hnh knh v tuyn trong nh p dng cho truyn thng UWB.

III Truyn thng UWB: trnh by cc thnh phn quan trng h thng truyn thng, nhn mnh vo cch kha cnh quan trng ca h thng nh iu ch, a truy nhp v s dng my thu Rake thu tn hiu.

IV nh gi mt s kha cnh ca h thng truyn thng UWB: xem xt cc vn quan trng c ngha quyt nh n s thnh cng ca h thng truyn thng UWB nh dung lng; nh hng nhiu qua li vi cc h thng

truyn thng v tuyn khc; so snh hiu nng vi mt s h thng truyn thng bng rng hin ti; v cc trng hp ng dng c th ca n.

I. TNG QUAN V H THNG UWB

1.1. Gii thiu v h thng UWB

Chng ny gii thiu cc khi nim chung v UWB v gii thch m khng s dng qu nhiu cng thc chng minh UWB l mt k thut hp dn v c tnh t ph. Trc ht ti trnh by v lch s pht trin ca UWB thy rng UWB khng hon ton l k thut mi c v phng din khi nim ln cc k thut x l tn hiu c s dng. Vi cc u th nh tc cao, cng sut tiu th thp, gy nhiu nh v,v, cc ng dng UWB rt hp dn c hin ti v trong tng lai vi cc ng dng khng dy. Trc khi tm hiu v truyn thng UWB trc ht ti trnh by nh ngha v truyn thng UWB.nh ngha:

UWB m t cc h thng truyn dn tri ph ti 500 MHz hay t s bng tn ln hn 20%. (1.1)Trong B:=fH-fL ch bng tn 10 dB ca h thng, v tn s trung tm h thng UWB vi fc=(fH+fL)/2 vi fH l tn s cao vi cng sut thp hn 10 dB so vi tn s c cng sut cc i, v fL l tn s thp vi cng sut thp hn 10 dB so vi tn s c cng sut cc i. V mt lch s, cc h thng rada UWB c pht trin ch yu phc v mc ch qun s bi v chng c th nhn xuyn qua cy ci v mt t. Tuy nhin, gn y k thut UWB ch yu s dng trong lnh vc dn s nh cc ng dng in t vin thng. Cc c im l tng ca cc h thng UWB l cng sut tiu th thp, gi thnh thp, tc cao, kh nng nh v chnh xc v gy nhiu cc nh. Mc d cc h thng UWB ph bin nhiu nm trc nhng gn y mi thc s c ch trong ngnh cng nghip v tuyn. K thut UWB c khc bit so vi cc k thut truyn dn khng dy bng hp thng thng- thay bng truyn dn trn cc knh tn s ring bit, UWB tri tn hiu trn mt di rng tn s. Dng truyn thng in hnh da trn sng v tuyn dng sin c thay th bi cc chui xung vi tc hng triu xung trn mt giy. Vi bng tn rng v cng sut rt nh lm tn hiu UWB ging nh tp m nn.a Lch s pht trin ca UWB

Phn ln mi ngi ngh rng UWB l mt cng ngh mi, do n l cng ngh cho php thc hin nhng iu trc khng th c. l tc cao, kch c thit b nh hn, tiu th cng sut thp hay cung cp cc ng dng mi. Tuy nhin, ng hn UWB l cng ngh mi theo ngha cc thuc tnh vt l mi ca n c pht hin v c a vo ng dng. Tuy nhin, phng php chim u th trong truyn thng v tuyn hin nay da vo cc sng dng sin. Truyn thng da vo sng in t dng sin tr nn ph bin trong truyn thng v tuyn n ni nhiu ngi khng bit rng h thng truyn thng u tin thc t da trn tn hiu dng xung. Nm 1893 Heirich Hertz s dng mt b pht xung to sng in t cho th nghim ca ng. Cc sng hin nay c th c gi l cc tp m mu. Trong khong 20 nm sau nhng th nghim u tin ca Hertz, cc b to sng ch yu l cc b pht tia la in gia cc in cc cacbon.Tuy nhin, truyn thng da trn sng dng sin tr thnh dng truyn thng ch yu v ch n nhng nm 1960 cc ng dng UWB mi c khi ng li mt cch nghim tc v tp trung ch yu vo pht trin cc thit b rada v truyn thng. ng dng trn lnh vc rada c ch rt nhiu v c th t c cc kt qu chnh xc vi cc h thng rada da trn truyn dn xung cc ngn. Cc thnh phn tn s thp ca tn hiu UWB c c tnh m xuyn vt th to c s pht trin cc loi rada quan st nhng vt th che khut nh rada lng t. Nm 1973 c bng sng ch u tin cho truyn thng UWB. Lnh vc ng dng UWB chuyn theo hng mi. Cc ng dng khc, nh iu khin giao thng, cc h thng nh v, o mc nc v cao cng c pht trin. Phn ln cc ng dng v pht trin din ra trong lnh vc qun s hay nghin cu c ti tr bi chnh ph M di cc chng trnh b mt. Trong qun i, cc chng trnh nghin cu ng dng cng ngh UWB nh rada chnh xc hot ng di danh ngha cc chng trnh nghin cu v pht trin. iu ch l trong nhng nm u, UWB c gi l k thut bng gc, k thut khng sng mang, v k thut xung. B Quc phng M c coi l ni u tin s dng thut ng ultra wideband.Nhng nm cui thp k 90 bt u thng mi ho cc h thng v thit b truyn thng UWB. Cc cng ty nh Time Domain v c bit l XtremeSpectrum c thnh lp quanh tng truyn thng s dng tn hiu UWB.b Cc u im ca UWB

Cc u im ca UWB c th tng kt l:1. Tc cao2. Gi thnh thit b thp3. Chng a ng 4. o c (nh v) v truyn thng trong cng mt thi imTi s trnh by chi tit hn nhng u im ny trong cc mc tip theo, nhng trc tin ti mun ni n kha cnh hp dn nht ca truyn thng UWB l tc cao. Tc cao cho php a ra cc ng dng v cc thit b mi m hin ti cha c. Tc ln hn 100 Mb/s t c v c kh nng vt qua tc trn khong cch ngn. Biu thc Shannon c biu din: (1.2)Trong C l dung lng ti a ca knh, vi n v [b/s]; B l bng tn knh [Hz]; S l cng sut tn hiu [W] v N l cng sut tp m [W].Biu thc ny ni cho thy c ba cch c th lm tng dung lng knh. C th tng bng tn, tng cng sut tn hiu hay gim tp m. C th thy rng dung lng knh tng tuyn tnh vi bng tn B nhng ch theo hm loga vi cng sut tn hiu S. Knh UWB c bng tn rt ln v thc t c th hy sinh (tng) rng bng tn gim cng sut pht v nhiu n cc ngun v tuyn khc. Qua biu thc Shannon c th thy cc h thng UWB c kh nng cung cp tc rt cao cho cc h thng truyn thng khng dy. Vn ny s c xem xt t m hn chng 4.c Nhng thch thc ca UWB

UWB c nhiu l do lm n rt hp dn cho truyn thng v tuyn cng nh nhiu ng dng khc trong tng lai, n cng c mt s thch thc phi vt qua tr thnh mt k thut c s dng ph bin.Cc h thng v tuyn lun phi tun th cc iu l trnh nhiu gia cc ngi dng khc nhau. Do UWB chim mt bng tn ln, c nhiu ngi cng s dng c bng tn nm trong di tn ny c th b nh hng v cn phi chc chn rng UWB s khng gy nhiu cho cc dch v hin ti ca h. c bit l trong trng hp nhng ngi dng ny c c quyn s dng di tn ca h. Do gii quyt vn ph tn l c bit quan trng trong h thng UWB.Nhng thch thc khc bao gm c vic cc nh sn xut chp nhn cc tiu chun m bo s tng thch gia cc thit b UWB. Hin nay cha c s nht tr hon ton v cc chun th kh nng c s xung t gia cc tiu chun cng nh cc thit b l rt r rng.Gi thnh thp nhng thm vo l s phc tp ca thit b UWB loi b nhiu v vn hnh cng sut thp c th li y gi thnh thit b UWB ln tng ng vi cc thit b v tuyn hin ti.1.2. Cc thuc tnh ca h thng v tn hiu UWB

Phn ny trnh by cc c im c bn ca h thng v tn hiu UWB. Chi tit ca mi c im c trnh by trong cc chng tip theo. Trc ht ta nghin cu mt n ph cng sut c p dng cho UWB.a Mt n ph cng sut

Ph ca tn hiu UWB l mt trong nhng vn chnh gy tranh lun gia ngnh cng nghip v tuyn v chnh ph thng mi ho UWB. Thc t, tn ca cng ngh l siu bng rng cho thy vn ph l trung tm ca cng ngh UWB. Tt c cc h thng truyn thng v tuyn phi tun th cc iu l v quy nh khc nhau v cng sut pht trong cc bng tn cho trc trnh nhiu ti cc ngi dng khc gn hoc chung di tn s.

Hnh 1.1: Mt n ph do FCC p t cho cc h thng truyn thng UWB

Cc h thng UWB chim bng tn rt rng v gy nhiu ti cc ngi dng hin ti. gi nhiu mc ti thiu FCC v cc nhm chun ho khc nh ngha cc mt n ph cho cc ng dng khc nhau vi cng sut pht c php mi di tn s khc nhau. Trong hnh 1.1 ch ra mt n ph ca FCC cho cc h thng UWB trong nh. Bng tn ln lin tc 7.5 GHz nm gia tn s 3.1 GHz v 10.6 GHz cng sut pht ti a cho php l -41.3 dBm/MHz. L do chnh ca cng sut u ra cho php v cng nh cc bng tn 0.96 GHz-1.61 GHz l do cc nhm i din cho cc loi hnh dch v hin ti, nh thng tin di ng, h thng nh v ton cu (GPS), v cc ng dng trong quc phng gy p lc trnh gy nhiu ln cc dch v . Cng sut cho php -41.3 dBm/MHz l kh thp so vi nh hng nhiu thc t h thng UWB c th gy ra v nhiu nhm chun ho hi vng t c cng sut pht cao hn. b Mu xung

Dng xung c bn c s dng trong UWB thng c gi l monocycle (n chu trnh) v n ch c mt chu k v c th l bt k hm no tho mn yu cu v mt n ph. Cc dng xung ph bin l cc xung Gaussian, Laplacian, Rayleigh v Hermittian ,v,v thng s dng cc dng o hm ca xung Gaussian. L do s dng xung Gaussian l cc k thut s dng to cc xung Gaussian l tng i n gin v chng c ph tn kh ph hp vi mt n ph. Trong ni dung n ny ti ch nghin cu h thng v phn tch h thng s dng xung Gaussian (bao gm xung Gaussian v cc o hm ca n).Monocycle px(t) c gi thit l o hm bc x ca xung Gaussian p(t): (1.3) (1.4)Trong l phng sai ca xung Gaussian. Mt ph cng sut (PSD) ca xung Gaussian l: (1.5) Vi P(f) l bin i Fourier ca p(t). PSD ca monocycle px(t) nhn c l : (1.6) Kt qu a ra trong cng thc (1.6) ch ra o hm xung c bn c th l mt cch iu chnh PSD ca monocycle trong trng hp ny c gi thit l xung Gaussian. Mt vn khc l phi xc nh rng xung, bi v xung Gaussian l tng c di khng xc nh. R rng y l mt iu khng thc t v cn phi gii hn rng xung thc t. Mt phng php hp l xc nh rng xung l chn rng xung ph hp vi phn trm nng lng trong khong thi gian rng xung chim. Trong ni dung n ny rng xung c nh ngha l: (1.7)Trong hnh 1.2 cc monocycle px(t) vi x=0,1,2 v rng xung pw=0.9 ns c ch ra ng thi vi mt ph cng sut tng ng v c th thy s thay i ph ca monocycle ph thuc vo bc ca o hm. Nu ng dng khc vi mt tiu chun khc th gii hn chim 99.9% cng sut trong n c th phi thay i cho ph hp vi nhng tiu chun ny.By gi coi nh rng xung bit, s lng mu trn mt xung c th c xc nh. y l iu quan trng biu din tn hiu s s dng trong sMt dng xung UWB in hnh l Gaussian doublet (x=2). Kiu xung l tn hiu s v m phng. i vi p2(t), thng s dng trong l thuyt m phng, c th biu din bi 10 mu trn mt xung, nu c chnh lch c 50 dB nm gia cc i PSD v mt na PSD cc i th tc ly mu l hiu qu.

Hnh 1.2: Cc monoycle px(t) vi x=02 vi PW=0.9 ns v cc dng ph mt cng sut ca chng

Mt c im cn ch khc l cc anten s dng trong cc b pht v thu. L do l anten hot ng vi tn hiu UWB khc vi cc tn hiu bng hp. C th thy t cc phng trnh Maxwell cc anten tng tc vi tn hiu UWB s c khc bit [7p.33-34]. Thnh phn in bc x s t l vi o hm ca xung pht v xung thu c s t l vi o hm bc hai ca xung c a n anten. Nhng nh hng ny phi c tnh n thc hin gii iu ch hiu qu.To xung Gaussian.

Hnh 1.3: M hnh Matlab n gin to tn hiu Gaussian doubletny thng c s dng trong cc h thng UWB bi v dng xung ca n to ra d dng. Xung dng ch nht c th to ra d dng bng cch tt m nhanh transistor

Hnh 1.4: Chi tit ca vic to xung trong h thng truyn thng UWB: (a) Chui xung ch nht; (b) Chui xung dng Gaussian; (c) xung o hm bc 1; (d) cc xung Gaussian doublet

Hnh 1.3 v 1.4 a ra mt m hnh to xung n gin, n m t qu trnh to xung Gaussian doublet, cc nh hng ca anten pht v thu tn hiu. Chng ta bt u vi xung ch nht hnh 1.4(a). Cc xung UWB c rng c ns hay ps. Chuyn mch tt m nhanh to cc xung khng c dng ch nht m c dng xp x dng xung Gaussian. l l do ca tn xung Gaussian, monocycle hay doublet. Mch n gin to xung Gaussian doublet c trnh by trn hnh 1.3. Pht xung trc tip n anten cc thnh phn xung b lc tu thuc vo cc c tnh ca anten. Qu trnh lc ny c th m hnh nh l qu trnh o hm [8]. nh hng tng t cng xy ra anten thu. y ti ch m hnh knh l tr v gi thit xung c khuych i pha thu. c Chui xung

Mt xung bn thn n khng th truyn nhiu thng tin. Thng tin hay d liu cn c iu ch vo mt chui cc xung c gi l mt chui xung nh hnh 1.5 minh ho. Khi cc xung c pht cc khong thi gian lp li, thng c gi l lp xung hay t l thi gian chim, ph thu c s bao gm cc nh ph cc tn s ng vi lp . Nhng tn s ny l bi s ca nghch o ca tc lp xung. Cc ng cng sut nh ny gi l cc ng rng lc bi v n trng ging mt chic lc. Xem hnh 1.6 (a).

Hnh 1.5: Chui xung UWB

Cc nh xung gii hn cng sut pht ng k. Mt phng php to dng ph ging tp m l lm nho ph tn hiu bng vic thm vo mt dch ngu nhin vo mi xung: hoc lm tr xung hoc pht xung trc mt khong nh so vi thi im pht xung thng thng (thi im danh nh). Dng ph thu c t s dng dch ngu nhin c ch ra trn hnh 1.6 (b) v c th so snh vi hnh 1.6 (a) thy rng cc ng rng lc c lm gim i rt r rt. Chng ta s thy chng sau, vic to tr ny khng hon ton ngu nhin nhng lp theo m gi ngu nhin bit (PN)d a ng

Mc ny s xem xt nh hng ca hin tng a ng, c bit trong knh v tuyn trong nh. Do b rng xung cc nh, nu cc xung c x l trong min thi gian th cc nh hng ca hin tng a ng, nh giao thoa k hiu (ISI), c th gim nh. a ng l hin tng pha thu thu c nhiu phin bn khc nhau ca mt tn hiu in t c truyn n bng cc ng khc nhau ti u thu. Xem hnh 1.7 cho v d v truyn dn a ng trong mt phng. Nguyn nhn ca hiu ng ny l do phn x, hp th, tn x, v nhiu x nng lng in t bi cc vt th gia cng nh xung quanh b thu v b pht.

Hnh 1.6: Ph ca chui xung cha c lm trn (a) v ca chui xung c lm trn bng cch dch ln pha trc hoc sau mt khong nh (TH)

Nu khng c vt th no hp th hay phn x nng lng th hin tng ny c th khng xy ra v nng lng bc x bc x t b pht ch ph thuc vo c im ca anten pht. Tuy nhin, trong thc t cc vt nm gia b pht v thu to ra cc hiu ng vt l nh phn x, hp th, tn x, nhiu x v chng gy nn hin tng a ng. Do chiu di ca cc ng khc nhau, cc xung s n b thu cc khong thi gian tr khc nhau vi t l vi di ng i. Cc h thng UWB thng c c im chng a ng. Kim tra cc xung m t phn trc, chng ta c th thy rng nu cc xung n trong khong mt rng xung chng s gy nhiu v nu chng tch bit t nht rng mt xung chng s khng gy nhiu. Nu cc xung khng b chng ln, chng c th c lc ra trong min thi gian hay ni cch khc c th b qua. Gi thit rng mt k hiu iu ch trn mt xung th chng s khng gy giao thoa trong cng mt k hiu. Mt khc nng lng t cc thnh phn a ng li c th cng li trong mt b thu Rake. Hnh 1.8 v 1.9 m t cc xung khng chng ln v chng ln tng ng.

Hnh 1.7: M hnh a ng in hnh trong nh, xung pht b phn x bi cc vt th trong nh to ra cc phin bn ca xung b thu vi cng , tr khc nhau

T biu thc: . Trong , l chnh lch qung ng, thi gian n b thu gia hai thnh phn a ng tng ng. hai thnh phn a ng khng chng ln nhau th . Do khong thi gian tch bit cn thit gia cc ng trnh hin tng chng ln gim khi rng xung gim i. y l l do rng xung cng nh cng tt c bit trong mi trng trong nh.Mt phng php khc gim nhiu a ng l gim thi gian chim dng (duty cycle) ca xung. Bng cch pht nhng xung vi khong thi gian ln hn tr a ng ln nht, nhng phn x khng mong mun c th b loi b d dng u thu. Cch ny r rng l khng hiu qu v to ra gii hn tc truyn dn d liu ti a i vi mt h thng vi phng php iu ch cho trc. Trong trng hp gii hn nu cc xung c pht lin tc th h thng s tng t vi h thng truyn dn sng dng sin.

Hnh 1.8: Hai xung n vi khong thi gian ln hn rng mt xung s khng chng ln v s khng gy nhiu

e Cc c im khc

Tc pht d liu Mt trong nhng li ch ca truyn dn UWB cho truyn thng l tc cao ca n. Hin ny tc chip lin tc c ci thin, phn ln cc ng dng nhm t tc trong khong 100 Mb/s ti 500 Mb/s [9], tng ng Ethernet c dy ti USB 2.0. Tc tng ng vi 100 n 500 ln tc ca Bluetooth, khong 50 ln tc ca 802.11b hay 10 ln tc ca WLAN. Nh thy bng 1.1 tc d liu hng ti cho truyn dn UWB trong nh l trong khong 110 Mb/s n 480 Mb/s, kh ln so vi cc chun khng dy hin nay. Thc t tc truyn dn hin ti c chun ho vo ba tc : 110 Mb/s vi khong cch c l 10 m, 200 Mb/s vi khong cch c 4 m v 480 Mb/s vi khong cch nh hn 4m.L do ca cc loi khong cch ny da trn ch yu cc ng dng khc nhau. V d, 10m ph hp vi kch thc ca mt phng. Khong cch nh hn 4m ph hp vi cc thit b nh home server v ti vi. Khong cch nh hn 1m ph v cho cc thit b trong my tnh c nhn.

Hnh 1.9: a) Hai xung chng ln v b) dng sng thu c bao gm cc xung chng ln

Mt trong nhng li th quan trng ca k thut UWB l phc tp t v gi thnh h, vi lng rt t thit b RF. S lng thit b t dn n gi thnh thp. B pht UWB n gin nht ch bao gm b tch phn xung, mch nh thi, v mt anten.Bng 1.1: So snh tc ca UWB vi cc chun khng dy cng nh c dy

ChunTc (Mb/s)

UWB, USB 2.0480

UWB (khong cch c 4 m), 1394a (4.5 m)200

UWB (khong cch c 10 m)110

Fast Ethernet90

802.11a54

802.11b11

Ethernet10

Bluetooth1

Cng sut tiu th thpVi thit k hp l thit b UWB c cng sut tiu th tng i thp. Cng sut tiu th mc tiu ca cc chip UWB l nh hn 100 mW. Bng 1.2 a ra s liu ca v cng sut tiu th ca cc chip truyn thng di ng khcBng 1.2: Cng sut tiu th ca UWB v cc chip truyn thng di ng khc

Chip ng dngCng sut tiu th (mW)

802.11a1500-2000

LSI 1394 tc 400 Mb/s700

MPU 32 bit RISC di ng200

B ADC camera s150

UWB (mc tiu)100

Bng hin th mu TFT trong thit b di ng75

LSI gii m MPEG-450

LSI m ho trong thit b di ng19

1.3. Cc lnh vc ng dng ca UWB

R&O (Report and Order) nh ngha ba loi h thng UWB l: Cc h thng chp nh, cc h thng truyn thng v o c, v cc h thng rada giao thng. Ph tn p dng cho cc ng dng trn c lit k ra bng 1.3.

( Cc mng WPAN (Wireless Personal Area Network): y l lnh vc ng dng ch yu ca UWB. c hiu l cc mng v tuyn trong nh. WPAN kt ni trong mt khong cch ngn (thng l t 10-20 m) gia cc thit b di ng, cc thit b truyn thng. Chng cho php truyn thng video v audio thi gian thc cht lng cao, truyn file gia cc h thng lu tr, thay th dy cp cho cc h thng gii tr ti nh. iu ny c th chng t mt c im th v l xy dng h thng vi cc thit b ton s trong tng lai gn. Mt im khc na l tt c cc thit b c th c kt ni tc cao vi nhau qua giao din v tuyn. N kt ni tt c cc loi thit b a dng nh: cc PDA, my di ng, TV, t lnh, my tnh v tt c cc b cm bin ng thi cc thit b ny c th bit c v tr ca cc thit b khc do kh nng nh v ca tn hiu UWB. iu ny m ra mt lot cc kh nng p dng cc dch v mi. Chng hn nh iu khin t xa t thit b di ng cc ng dng trong nh hay h thng an ninh thc hin nhn din v m ca cho bn v.v. Do , k thut UWB pht trin c th xy dng lp vt l y ha hn cho cc h thng WPAN do c im tc cao trn khong cch ngn, vi gi thp, cng sut thp v t l thi gian chim thp.

Hnh 1.10: Kt ni cc thit b s dng UWB

( Mng cm bin (sensor network): Mng cm bin bao gm mt s lng ln cc trm tri trn mt vng no . Cc trm c th c nh, v d trin khai theo di tnh trng nhim; hoc di ng, nu c trang b cho binh lnh, lnh cu ho, hoc robot trong qun i v trong gii quyt cc tnh trng khn cp.Yu cu quan trng cho mng cm bin vn hnh trong cc iu kin kh khn trn l gi thnh r, tiu tn t nng lng, v a chc nng. Cc h thng truyn thng UWB tc cao cho php thu thp, phn phi v trao i mt lng ln thng tin cm bin trong thi gian ngn. c bit, nng lng l rt hn ch trong mng cm bin so vi cc mng WPAN bi kh khn trong vic np li acqui cho cc thit b cm bin. Cc nghin cu ch ra p dng cng ngh UWB cho mng cm bin p ng nhng yu cu v nng lng v gi thnh. Hn na, c th khai thc kh nng nh v chnh xc ca UWB c bit ti nhng ni GPS cha c s dng.( Cc h thng chp nh: Khc vi cc h thng rada thng thng nhim v ch yu l xc nh cc ngun pht x, cc xung rada UWB nh v khong cch nh hn. Tn hiu phn x t vt th cn nh v khng ch thay i v bin , thi gian m cn thay i c v dng xung. Kt qu l tn hiu UWB c nhy cao hn nhiu so vi cc tn hiu rada thng thng. c tnh ny c p dng cho cc h thng rada. Mt khc do cc thnh phn tn s thp ca tn hiu UWB c kh nng m xuyn nn c th m rng vi cc ng dng khc nh chp nh xuyn tng, lng t, v i dng; hay cc thit b chn on y t, gim st ng bin gii. ( Cc h thng rada giao thng: Cm bin da trn UWB c kh nng ci thin vn ca cc sensor chuyn ng khong cch ngn. Da vo kh nng nh v c chnh xc cao ca UWB, c th xy dng cc h thng iu khin giao thng v trnh tai nn thng minh. Cc h thng ny c th ci thin hot ng ca cc ti kh bo him trong phng tin giao thng v h tr iu khin giao thng cng nh t thay i ch hot ng ph hp tnh trng giao thng. K thut UWB cn c th tch hp vo cc h thng gii tr v dn ng trong phng tin giao thng bng cch download d liu t cc b pht UWB hng dn dc theo hai bn ng.

1.4. Tng kt

Chng ny gii thiu tng quan v h thng cng nh tn hiu UWB, v phn tch mt s kha cnh ca tn hiu UWB nh ph tn, dng xung ca xung UWB. iu c bit quan trng ca h thng UWB l cng sut pht cng nh mt ph cng sut ca tn hiu UWB b gii hn bi mt n ph cng sut do FCC a ra. Chng ta thy rng do cng sut pht trn ph tn rt thp -41.3 dB/ MHz, trong iu kin ca phading, chng rt t c kh nng gy nhiu n cc h thng truyn thng v tuyn khc. rng xung cc nh nn cc xung c th phn bit vi cc thnh phn a ng khng mong mun khc d dng do kh nng phn gii thi gian cao. iu ny dn n c im chng a ng ca tn hiu UWB. Ngoi cc u im ng dng trong lnh vc truyn thng cc c tnh khc ca tn hiu UWB nh kh nng m xuyn vt th v kh nng nh v cao lm cho cng ngh UWB c phm vi ng dng rt rng nh truyn thng, rada, chp nh v.v cng nh tch hp hiu qu ng thi nhiu ng dng trn nn tng cng ngh ny. Chng hn nh tt c cc thit b trong phng c th thc hin truyn thng v tuyn tc cao vi nhau ng thi c th bit c v tr ca nhau.Hn na, do c im cc b thu v pht khng cn cc linh kin ln v t ca tng trung tn do khng phi thc hin chuyn i trung tn (IF) nn c th gim gi thnh, kch c, trng lng, v cng sut tiu th ng k ca cc h thng UWB so vi cc h thng truyn thng bng hp khc.

Bng 1.3: Di tn quy nh cho cc lnh vc ng dng UWB khc nhau

Truyn thng trong nh [GHz]Truyn thng cm tay [GHz]Chp nh tn thp [GHz]Chp nh tn cao [GHz]Chp nh tn trung bnh [GHz]Rada giao thng [GHz]

[3.1,10.6][3.1,10.6]