Massive MIMO -Dich

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MIMO ln cho th h tip theo H thng khng dyGii thiuNhiu ngi s dng MIMO cung cp cc li th ln hn thng thng im MIMO: n hot ng vi ng-ten a n gi r thit b u cui, mt mi trng phong ph tn x l khng cn thit, v phn b ngun lc l n gin bi v mi thit b u cui hot ng s dng tt c cc thng tn s thi gian. Tuy nhin, nhiu ngi s dng MIMO, nh ban u hnh dung, vi cc con s ng ca dch v ng-ten v thit b u cui v tn s-b phn hot ng song, khng phi l mt cng ngh kh nng m rng. Ln MIMO (h thng ng-ten cng c gi l quy m ln, rt ln MIMO, siu MIMO, y kch thc MIMO, mt d ARGOS) lm cho sch ph v vi cc thc hnh hin nay bng cch s dng mt vt qu ln ca ng-ten dch v trong hot ng thit b u cui v phn chia thi gian hot ng song. ng-ten ph gip bng cch tp trung nng lng vo cc khu vc nh hn bao gi ht dung lng mang li nhng ci tin ln thng qua v x nng lng hiu qu. Li ch khc ca MIMO ln bao gm s dng rng ri khng tn km thnh phn nng lng thp, gim tr, n gin ha ca tng MAC, v mnh m chng li c gy nhiu. D on thng lng ph thuc vo mi trng truyn cung cp knh tim cn trc giao cc thit b u cui, nhng cho n nay th nghim khng tit l bt k gii hn trong lnh vc ny. Trong khi ln MIMO Hin th hnh nh nhiu truyn thng nghin cu vn khng lin quan, n khm ph nhng vn hon ton mi khn trng cn ch : nhng thch thc lm cho nhiu thnh phn chnh xc thp chi ph thp m lm vic c hiu qu vi nhau, vic mua li v ng b ha cho thit b u cui mi c tham gia, vic khai thc ca ph bc t do cung cp bi s vt tri ca ng ten dch v, gim tiu th in nng ni b t c tt c nng lng hiu qu gim, v vic tm kim tnh hung trin khai mi. Bi vit ny trnh by mt tng quan v cc khi nim MIMO ln v hin i nghin cu v ch .GOING LARGE: MASSIVE MIMO

Ln nhiu-vo nhiu / ra (MIMO) l mt cng ngh mi ni c quy m ln MIMO bi c th n t hng ca ln so vi nh nc hin ti ca ngh thut. Trong bi ny, chng ti lm theoln trn ca chng ti trnh by trc [1], vi mt tp trung vo nhng pht trin trong ba nm qua; Hu ht c bit, nng lng hiu qu, khai thc vt qu bc t do, thi gian-b phn kp (TDD) hiu chun, k thut chin u nhim th im, v hon ton mi knh o lng. Vi ln MIMO, chng ti ngh ca h thng s dng ng-ten mng vi ng-ten trm mt vi ng thi phc v cc hng chc nhiu thit b u cui trong cc ngun ti nguyn cng mt tn s thi gian. Nhng tin c bn ng sau ln MIMO l gt hi tt c nhng li ch ca truyn thng MIMO, nhng trn mt quy m ln hn nhiu. Ni chung, ln MIMO l mt enabler cho s pht trin ca tng lai mng bng thng rng (c nh v in thoi di ng), m s c nng lng hiu qu, an ton, v mnh m, v s s dng quang ph hiu qu. Nh vy, n l mt enabler cho c s h tng x hi k thut s trong tng lai s kt ni Internet ca ngi dn v Internet ca nhng iu cn vi m my v c s h tng mng khc. Nhiu cu hnh khc nhau v cc tnh hung trin khai cho cc ng-ten thc t mng c s dng bi mt h thng MIMO ln c th hnh dung (hnh 1). Mi n v ng-ten s c nh v hot ng, tt hn l cho n thng qua mt xe but k thut s quang hc hoc in. MIMO ln da trn khng gian ghp knh, m ln lt da trn trm tt c kin thc knh, v vic ti ln v ti. Ti ln, iu ny l d dng thc hin bng thit b u cui gi phi cng, da trn cc trm c s c tnh nhng phn hi knh mi ngi trong s cc thit b u cui. Ti l kh khn hn. thng thng h thng MIMO chng hn nh cc di hn Evolution (LTE) tiu chun, trm gi ra th im waveforms, da trn cc thit b u cui c tnh cc cu tr li knh, quantize c tnh do thu c, v thc n cho h quay li trm c s. iu ny s khng c kh thi trong cc h thng MIMO ln, t khng khi hot ng trong mt mi trng di ng cao, v hai l do. Phi cng u tin, ti u ti nn c hai bn trc giao gia cc ng-ten. iu ny c ngha rng s lng thi gian-tn s ti nguyn cn thit cho phi cng ti quy m vi s lng cc ng-ten, do , mt h thng MIMO ln s yu cu ti a 100 ln cc ngun lc nhiu hn so vi mt h thng thng thng. Th hai, s knh phn ng mi thit b u cui phi c tnh l cng t l thun vi s lng cc trm ng ten. Do , cc ngun ti nguyn uplink cn thit thng bo cho cc trm c s ca cc phn ng knh s ln n 100 ln ln hn trong h thng thng thng. Ni chung, gii php l hot ng trong ch TDD, v da vo nghch gia cc knh ti ln v ti, mc d tn s-b phn duplext (loi) hot ng c th c th c trong mt s trng hp [2]. Trong khi cc khi nim ln MIMO c c ch yu l l thuyt cho n nay, kch thch nhiu nghin cu c bit trong l thuyt ma trn ngu nhin v ton hc c lin quan, th nghim c bn ang tr nn c sn [3], v o c u tin knh c thc hin [4, 5].TNG OTENTIAL Pca MASSIVE MIMO

Ln MIMO cng ngh da trn phasecoherent nhng computationally rt n gin ch bin ca tn hiu t tt c cc ng-ten ti cc trm c s. Mt s li ch c th ca mt h thng MU-MIMO ln l:

Massive MIMO c th tng nng lc 10 ln hoc nhiu hn v ng thi nng cao hiu qu nng lng chiu trn th t ca 100 ln. Kt qu kh nng tng t cc tch cc khng gian ghp knh c s dng trong MIMO ln. Nhng nguyn tc c bn m lm cho s gia tng ng k trong nng lng hiu qu c th l rng vi mt s ln cc ng-ten, nng lng c th c tp trung vi cc sc nt thnh cc khu vc nh trong khng gian (hnh 2). Vt l c bn l chng chp mch lc ca wavefronts. Bi mt cch thch hp to hnh tn hiu c gi bi cc ng-ten, trm c th chc chn rng tt c wavefronts chung pht ra t tt c cc ng-ten tng ln cch xy dng ti a im ca cc thit b u cui d nh, nhng destructively (ngu nhin) gn nh khp mi ni khc. S can thip gia thit b u cui c th c dp tt hn na bng cch s dng, v d, zero-buc (ZF). iu ny, Tuy nhin, c th n vi chi ph ca nhiu hn truyn sc mnh, nh minh ha trong hnh 2.

Hn nh, hnh 3 (t [6]) miu t ci gi c bn gia nng lng hiu qu trong iu khon ca tng s bit (tng t l) truyn mt Joule cho mi thit b u cui nhn c dch v nng lng chi tiu, v quang ph hiu qu trong iu khon ca tng s bit (tng t l) truyn cho mi n v ca quang ph radio tiu th. Hnh minh ha mi quan h cho ti ln, t thit b u cui trm (hiu sut ti l tng t). Cc con s cho thy thng mi-off cho ba trng hp: Mt h thng ti liu tham kho vi mt antennaserving duy nht mt thit b u cui duy nht (mu tm) Mt h thng vi ng-ten 100 phc v mt singleterminal bng cch s dng thng thng beamforming (xanh) Mt h thng MIMO ln vi 100 antennassimultaneously phc v nhiu (khong 40 y) thit b u cui (, bng cch s dng ti a t l kt hp, v mu xanh, bng cch s dng ZF). S hp dn ca t l ti a kt hp (MRC) so vi ZF khng phi l ch n gin tnh ton ca n nhn ca cc tn hiu nhn c ca cc knh lin hp phn ng- nhng cng l n c th c thc hin trong mt thi trang phn phi, c lp ti mi n v ng-ten. Trong khi ZF cng lm vic kh tt cho mt h thng MIMO thng thng hoc c kch thc va phi, MRC ni chung khng. L do MRC hot ng rt tt cho ln MIMO l nhng phn hi knh lin kt vi thit b u cui khc nhau c xu hng gn nh trc giao khi s lng cc trm ng ten l ln.

Hnh 1.Mt s cu hnh c th c ng-ten v tnh hung trin khai cho cc trm c s MIMO ln.D on trong hnh 3 da trn mt phn tch l thuyt thng tin rng s a vo ti khon intracell can thip, cng nh chi ph bng thng v nng lng ca vic s dng phi cng c c cc knh thng tin trng thi trong mt mi trng di ng cao [6]. Vi thu MRC, chng ti hot ng trong ch gn nh ting n gii hn l thuyt thng tin. iu ny c ngha l cung cp cho mi thit b u cui vi mt t l khong 1 trc ta b/phc tp (1 b/s/Hz). Trong mt h thng MIMO ln, khi s dng MRC v hot ng trong ch "xanh" (tc l, m rng quy m xung sc mnh cng nhiu cng tt m khng c nghim trng nh hng n hiu qu tng th quang ph), multiuser can thip v cc hiu ng t phn cng hon ho c xu hng b qu ti bi ting n thermal. L do hiu qu tng th quang ph vn c th 10 ln cao hn so vi MIMO thng thng l hng chc nhiu thit b u cui c phc v cng mt lc, trong ti nguyn cng mt tn s thi gian. Khi hot ng ch b/kch thc/terminal 1, cng l mt s bng chng rng intersymbol can thip c th c coi nh l b sung ting n nhit [7], do cung cp mt cch x l vi tn s trc giao-b phn ghp knh (OFDM) nh l mt phng tin combatting intersymbol can thip.

hiu quy m cng sut li nhun ln MIMO cung cp, hy xem xt mt mng bao gm 6400 omnidirectional ng ten (Tt c hnh thc yu t 6400 (l/2)2 40 m2) truyn vi mt sc mnh tng s 120 W (tc l, mi ng-ten ta ra khong 20 mW) trn mt bng thng 20 MHz trong ban nhc c nhn truyn thng dch v (my tnh) (1900 MHz). Cc mng phc v 1000 thit b u cui c nh phn phi ngu nhin trong mt a bn knh 6 km, tp trung vo mng, mi thit b u cui c mt ng-ten tng 8 dB. Chiu cao ca mng ng ten l 30 m, v chiu cao ca cc thit b u cui l 5 m. bng cch s dng cc m hnh Hata-COST231, chng ti thy rng mt con ng 127 dB khong cch 1 km, v phm vi phn r m l 3,52. cng l bnh thng ng nhp bng m dn vi lch chun 8 dB. Cc thit b thu receiver c mt con s ting n 9 dB. Mt phn t thi gian chi cho truyn dn ca cc phi cng uplink TDD knh d ton, v ngi ta cho rng cc knh l ng k lin tc hn khong 164 ms c tnh li nhun Knh vi chnh xc . Ti d liu c truyn qua t l ti a truyn (MRT) beamforming kt hp vi quyn lc kim sot, ni 5 phn trm ca thit b u cui vi cc knh ti t nht c loi tr khi Dch v. Chng ti s dng mt cng sut thp hn rng buc t [8] m rng p ng chm dn, gn/xa nh hng v kim sot quyn lc, chim nhn ting n, knh d ton li, overhead th im truyn dn v khng hon ho ca tu in ngm beamforming. Chng ti s dng iu khin ti u ti-min in, confers mt t l tn hiu-nhiu-plus-nhiu bng trn mi ngi trong s cc thit b u cui 950 v do bng thng qua. Trung bnh s ngu nhin v tr thit b u cui v bng m cho thy rng 95 phn trm ca cc thit b u cui s nhn c mt thng lng ca 21,2 Mb/s/terminal.Nhn chung, cc mng trong v d ny s cung cp cho thit b u cui 1000 mt thng lng ti tt c cc 20 Gb/s, dn n mt hiu qu tng quang ph ca 1000 b/s/Hz. iu ny s l , v d, cung cp 20 Mb/s dch v bng thng rng cho mi 1000 nh. Kim sot quyn lc ti a-min cung cp dch v bng ng thi thit b u cui 950. Cc loi quyn lc kim sot kt hp vi thi gian-b phn ghp knh c th cha lu lng truy cp khng ng nht nhu cu ca mt b ln hn ca thit b u cui.

Nhn MRC (cho ti ln) v cc i tc tu in ngm precoding (cho ti) cng c bit n nh kt hp lc (MF) trong cc ti liu.

MIMO ln c th c xy dng vi chi ph thp, thnh phn nng lng thp.

Hnh 2.Sc mnh tng i trng xung quanh mt mc tiu thit b u cui trong mt mi trng tn x ca kch thc 800 l 800 l khi trm l t 1600 l bn tri. Th mnh trung bnh l lnh vc c tnh trn 10.000 ngu nhin v tr ca 400 scatterers khi hai precoders khc nhau tuyn tnh c s dng: mt) tu in ngm precoders; b) ZF precoders. Bn tri: gi mu l ca sc mnh trung bnh l lnh vc, vi mc tiu ngi dng v tr ti Trung tm () v bn ngi dng khc gn (). Bn phi: trung bnh th mnh lnh vc nh l b mt, cho php mt ci nhn thay th ca tp trung khng gian.

MIMO ln l mt tr chi thay i cng ngh lin quan n l thuyt, H thng, v thc hin. Vi ln MIMO,

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