4G - H thng thng tin di ng ca tng lai KS. Nguyn Trung Kin

I. GII THIU H thng thng tin di ng th h 3G (Third-generation) c tiu chun ho bi IMT-2000 (International Mobile Telecommunications 2000), bt u c pht trin ti Nht Bn vo thng 10 nm 2001. T n nay 3G pht trin mt cch nhanh chng v ng mt vai tr quan trng trong vic pht trin cc loi dch v a phng tin trong phi k n dch v Video. Vi xu hng pht trin nh hin nay, chng ta tin rng trong tng lai khng xa thng tin di ng s ng mt vai tr quan trng hn na trong i sng hng ngy, v s dng in thoi di ng l mt phn khng th thiu ca ngi dn trong mi hot ng. Chnh v l do ny, th h thng tin di ng mi, th h 4G, cn phi c nhng tnh nng vt tri hn so vi kh nng ca IMT-2000. Nghin cu, nm bt v pht trin h thng thng tin di ng 4G l mt yu cu cn thit hin nay, ph hp vi xu th pht trin chung ca ngnh vin thng.

Trong bi bo ny, chng ti trnh by nhng nt c bn nht lin quan n nhng yu cu v phm cht v kh nng ca h thng 4G cn phi p ng. i km theo l nhng vn k thut v cu hnh h thng m bo nhng yu cu ny.

II. CC YU CU V MC TIU THIT K H THNG II.1. Nhng yu cu 1. Thng tin bng rng

T trc n nay, lu lng trn mng thng tin di ng vn ch yu l lu lng thoi. H thng th h 2G, h thng t bo s c nhn PDC (Personal Digital Cellular) gii thiu cc dch v I-mode. Nhng dch v ang c ph bin hin nay nh: truy cp Internet, thng mi in t, e-mail. Nhng dch v ny ch yu l thng tin d liu da trn vn bn qua mng t bo. H thng IMT-2000 xut nhng dch v tc cao t 64 n 384 kbit/s, v t l lu lng s liu trn thoi tng ln. Tuy nhin, s pht trin mnh ca cc dch v bng rng nh ADSL (Asymmetric Digital Subscriber Line), cc h thng truy nhp cp quang, cc mng LAN c quan, gia nh lm tng nhu cu s dng cc dch v tng ng ca mng thng tin di ng.

2. Chi ph thp

Khi cc dch v bng rng pht trin, cc thu bao c th trao i rt nhiu loi thng tin vi nhau, tuy nhin h li khng sn sng tr mt chi ph qu cao cho lng thng tin trao i qu nhiu nh vy. V vy cn phi gim gi cc ca cc dch v xung bng hoc thp hn gi cc ca cc dch v hin ti. H thng IMT-2000 gim mc cc tnh theo bt v a ra cc mc gi tng i thp, nhng h thng 4G i hi mt knh bng thng rng vi mc gi thm ch thp hn mc gi theo bit m IMT-2000 a ra.

3. Vng ph sng rng

Mt trong nhng c tnh ca thng tin di ng l c mt khp mi ni mi lc. Nhng kh nng ny cng l mt tiu ch quan trng cho s pht trin ca thng tin di ng trong tng lai. Khi mt h thng mi u tin c gii thiu th ni chung rt kh khn trong vic cung cp mt vng ph sng rng nh mng hin c, v khch hng s khng mua cc thit b u cui mi nu h b gii hn vng ph sng. Nhng thit b c mn hnh hin th ln, nh PDAs (Personal Digital Assistans) v my tnh c nhn vi kh nng kt ni khng dy ngy cng c s dng ph bin. Gn lin vi nhng thit b ny l cc dch v cao cp v thng c s dng trong nh, v vy chng ta cn a ra cc dch v vi vng ph sng trong nh tt.

4. Dch v a dng v d s dng

i tng s dng thng tin di ng rt a dng v rt khc nhau. Trong tng lai, chng ta hy vng c th nng cao phm cht v chc nng h thng c th cung cp nhiu loi hnh dch v, khng ch l cc dch v thoi truyn thng m cn truyn cc thng tin lin quan n tt c nm gic quan ca con ngi. V thu bao phi d dng s dng cc dch v ny (d dng ci t, d dng kt ni, ).

II.2. Mc tiu thit k Mc tiu thit k h thng p nhng yu cu trn y c minh ho trn Hnh 1. Coi thng tin d liu v video l dch v chnh, h thng 4G phi cung cp tc truyn dn cao hn vi dung lng ln hn (c v s lng thu bao l lu lng) IMT-2000.

Bt u cc dch v mi datrn nhng kh nng mi

Cc dch v cao cp nh nngcao phm cht, tnh nng mng

Tc truyn dn: 384 kbit/sDung lng h thng

Chi ph

H thng trm gcThi gian tr

y100 Mbit/s (tc cao nht cami trng di ng); 1Gbit/s (tc ti a ca mi trng trong nh)ygp 10 ln h thng 3Gy1/10 n 1/100 trn btyAll IP

y50 ms hoc nh hn

H tng dch v mi- Trin khai nhanh cc dch v mi- D dng trin khai cc dch v miKt ni v chuyn giao linh hot gianhiu h thng truy nhp

H thng IMT-2000 H thng 4G Hnh 1: Mc tiu thit k h thng 4G

Hin nay, coi tc chnh l cht lng truyn dn, mng LAN t c tc t 10 n 100 Mbit/s, v tc ca mng ADSL cng t c 2-3 Mbit/s. Mc tiu thit k h thng thng tin di ng l t tc xp x 100 Mbit/s i vi mi trng ngoi tri v c Gbit/s vi mi trng trong nh. S khng c ch cho mng thng tin di ng th h mi nu khng c tc ln hn t nht 10 ln tc hin ti ca IMT-2000. m thng tin thi gian thc gia cc thit b u cui vi nhau th h thng mi cn phi gim thi gian tr truyn dn xung di 50 ms. Gi s rng cc dch v trong tng lai s da trn truyn dn IP (Internet Protocol), hiu qu truyn dn gi IP qua mng v tuyn cng cn phi tnh n. H thng mi bn cnh vic nng cao dung lng truyn dn phi m bo c vic gim chi ph. Chi ph tnh trn 1 bt truyn dn phi gim xung bng 1/10 hoc 1/100 mc chi ph hin ti bng cch gim chi ph thit b h tng, chi ph hot ng v chi ph xy dng. Mc tiu thit k c cp trn y tp trung vo nhng dch v c phm cht tt hn cc dch v hin ti, v d dng s dng. iu m nhng nh i tin phong trong th trng dch v 4G cn phi lu l kh nng tch hp h thng LAN khng dy trong nh vi h thng hu tuyn v thc hin trin khai cc dch v mi trong thi gian ngn.

III. Nhng vn c bn trong cu hnh h thng 4G III.1. Nhng vn k thut Vn k thut cn thit i vi mng thng tin di ng th h 4G p ng nhng yu cu c nu ra phn trn c trnh by trn hnh 2.

1. Dung lng ln v tc truyn dn cao

IMT-2000 trin khai a truy nhp theo m bng rng WCDMA (Wideband Code Division Multiple Access) v t c tc 2Mbit/s vi bng tn c rng 5 MHz. Ngy nay, vic pht trin k thut iu ch v gii iu ch thch nghi a lp cho php tc truyn dn t xp x 10 Mbit/s vi cng mt bng tn s dng. t c tc truyn dn t 100 Mbit/s n 1 Gbit/s, chng ta cn phi s dng bng tn ln hn v cc h thng truyn dn mi ph hp vi truyn dn tc cao. i vi thng tin d liu, chng ta s cn h thng truy nhp v tuyn c th truyn dn gi tin hiu qu. Tm quan trng ca vic ph sng trong nh thc y cc cng ngh phi pht trin theo hng c th s dng cho c mi trng truyn sng trong nh v ngoi tri. c c nhng bng tn rng cho truyn dn tc cao v p ng nhu cu lu lng thoi ang tng cao, chng ta phi quan tm n cc bng tn mi, v pht trin cc phn t mng cn thit nh cc b khuch i, cc b lc v tnh ton suy hao truyn sng cho nhng bng tn ny. Cng vi vic nghin cu pht trin cc gii php s dng hiu qu ti nguyn ph tn hn ch cng rt cn thit.

2. Chi ph thp hn

Vi cc cng ngh cu hnh h thng thng thng, nu s dng mt bng tn cao hn t c tc truyn dn cao hn s lm gim kch thc cell, hay gim vng ph sng ca mt trm gc. vn gi c vng ph sng rng nh trc y yu cu phi c nhiu trm gc hn v do lm tng chi ph mng. trnh c vn ny chng ta cn phi m rng bn knh cell bng cch s dng nhng phng php truyn dn v tuyn phm cht cao hn, cc k thut iu ch v gii iu ch ci tin, dn anten thch nghi, cc b thu tp m thp. Xa hn na, gim chi ph xy dng v hot ng mng, chng ta phi nghin cu thc hin kt ni cc trm gc vi mng ng trc, cng ngh trm gc iu khin c lp v cc cng ngh kt ni v tuyn phn lp.

Cng ngh anten v truyn dn tn hiuyTruyn dn tc cao/iu ch v gii iu

ch phm cht ttyDung lng ln, truy nhp gi qung byAnten dn thch nghiy FEC, ARQ, TPC phm cht cao

Cu trc mng truy nhp v iu khinyiu khin gi IP/iu khin phn b

mng truy nhp v tuyn RANyiu khin QoS truyn dn d liu giyiu khin lin kt lin mch vi cc

mng khc

Thit k qu ng truynv truyn dn sng v tuynyTruyn dn vi bayTruyn dn qung byTruyn dn trong nh

RF circuit/EMCyKhuch i hiu sut caoyB nhn tp m thpySoftwave defined radioyMicrowave EMC

Cc tuyn truy nhpyCc tuyn v tuyn qung byMng tch hp quang/v tuyn

FEC : M sa li trcARQ :Yu cu pht li t ngTPC : iu khin cng sutRAN : Mng truy nhp v tuynQoS : Cht lng dch vRF : Tn s v tuynEMC : Tng thch in t trng

Hnh 2: Nhng vn k thut lin quan n cng ngh v tuyn 3. Kt ni lin mng da trn cng ngh IP

Mt bin php cho nhng thu bao s dng h thng mi khng gp phi vn v vng ph sng l phi m bo cc thit b u cui mi phi h tr hot ng trn c h thng c v h thng mi. Mt khc, chng ta phi tnh n kh nng roaming quc t, mt thit b u cui phi c h tr hot ng trn nhiu h thng nh s dng cng ngh SDR (Softwave Defined Radio). Vi cng ngh ny, thit b u cui c th hot ng trn nhiu bng tn khc nhau ca cc quc gia v khu vc khc nhau. Hn na, mng thng tin di ng trong tng lai phi tch hp vi nhiu phng thc truy nhp khc nhau, vi rt nhiu loi cell c cc kh nng kt ni lin mng da trn cng ngh IP. Chnh v vy, kt ni lin

mng v chuyn giao gia cc h thng truy nhp l mt yu cu cn thit ngoi yu cu v kh nng chuyn giao v roaming ni b v gia hai mng thng tin di ng vi nhau.

III.2. Cu hnh h thng 1. Cu hnh h thng da trn IP

H thng 4G phi c cu hnh kt ni vi mng IP, truyn dn hiu qu cc gi IP, cng tn ti vi cc h thng truy nhp khc, linh hot khi a vo khai thc, c kh nng m rng khi cn, Cc mng IP cng c th kt ni d dng hoc ph hp vi cc h thng truy nhp v tuyn khc hn cc h thng 4G. im truy nhp v tuyn 4G (4G-AP-4G Access Point) s c kt ni vi mt b nh tuyn truy nhp AR (Access Router) nh trn Hnh 3. 4G-AP c cc chc nng iu khin truyn dn v tuyn, chuyn giao, cho php cc thit b di ng lin lc vi nhau da trn IP. Cc 4G-AP s c t tng ng vi cc cell ca chng. Khi mt thit b di ng di chuyn gia cc cell, vic chuyn giao s c thc hin bng chuyn mch n gin gia cc im truy nhp v cc vng v tuyn nu hai im 4G-AP kt ni vi cng mt AR. Nu hai im 4G-AP thuc hai AR khc nhau th nh tuyn truyn dn gi tin trong mng IP phi thay i tc th. Lit kt hot ng gia chuyn mch 4G-IP v nh tuyn mng IP ng mt vai tr rt quan trng i vi qu trnh chuyn giao. i vi chuyn giao gia mt 4G-AP v mt AP ca h thng khc, thit b di ng phi c chc nng truy nhp c hai mng. Chuyn giao s c thc hin bng vic theo di v so snh gia cc h thng khc nhau la chn c mt h thng ph hp.

Cell di ng

Cell ngoitri

Cell trong nh

Mng truynhp khc

Mng truynhp khc

Ni vi mng khc(Internet, )

Mng IP

AR : b nh tuyn truy nhp4G-AP : im truy nhp v tuyn 4GMR : b nh tuyn di ng

Hnh 3: Cu hnh h thng 4G 2. Phn loi v cu hnh cell theo mi trng truyn dn

H thng 4G c cell ngoi tri, trong nh, trong phng tin di chuyn, nh trn Hnh 3. Nhng cell ngoi tri c vng ph sng rng, cho php cc thit b u cui ang di chuyn vi tc cao trao i thng tin vi tc cao. Vng ph trong nh c thc hin bi cc indoor AP. Cc Indoor AP c thit k khng ch gip trao i thng tin tc cao v hot ng n gin m cn p ng nhng yu cu ca mt mng LAN v tuyn tng lai. Ngoi ra, cc cell trong phng tin giao thng di chuyn nh xe but, tu ho (c gi l cc cell/mng di ng) c phc v bi mt b nh tuyn di ng MR (Mobile Router). MR c chc nng chuyn tip tn hiu gia trm gc v thit b u cui trn phng tin, nn nhng thit b u cui ny khng lin lc trc tip vi trm gc nh thng thng. Cu hnh ny c thit k t c hiu qu v cng sut pht ca thit b u cui, tc truyn dn, ln ca tn hin iu khin. Kt ni multi-hop a chng, mt phng php hiu qu m rng kch thc cell s c nghin cu nh l mt cch gii quyt vn cc im cht gy ra bi hiu ng bng. Truyn dn d liu qua trm chuyn tip c thc

hin ngay c khi b gii hn v cng sut pht ca thit b u cui v suy hao truyn sng ln.

3. Thng tin a phng tin

Nhng mng IP trc y ch yu cung cp cc dch v dng TCP, nhng vi cc ng dng thi gian thc m c d bo l s pht trin mnh trong tng lai nh thng tin a phng tin th vn QoS (Quality of Service) ca dch v rt quan trng v cn phi c ch . Cu hnh h thng 4G cho php truyn dn vi tc cao, hot ng lin kt vi cc mng IP trong khi vn phi m bo c QoS ca truyn dn gi.

Trm gc

Nh cao tng

Thng tin trc tip b chn binh cao tng

Thng tin trc tip khng th thc hin c do khongcch ln hn phm vi ph sng ca single-hop

Hnh 4: Lin lc thng qua cc kt ni multi-hop V. Kt lun H thng thng tin di ng 4G v ang c nghin cu nhiu ni trn th gii. Vi mc ch gii thiu nhng nt c bn nht v h thng thng tin di ng trong tng lai, h thng 4G, bi bo trnh by nhng c im cng nh nhng yu cu c bn ca h thng. Bn cnh , chng ti cp n nhng vn k thut lin quan trong vic cu hnh h thng 4G p ng nhng yu cu nu trn.

Ti liu tham kho

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