Bung vdi nhiing gi LTEbiia hen dem lai, vide tndn khai thuong mai hda LTE cho thay cae mang LTE cd the cung cap ddc dd sd hdu dinh ldn den 100 Mb/s vi dd trd duoi 20 mih 0iy. Budc tiep theo tiong tidn trinh phit trien eua LTE dd chinh la cac mang LTE-Advanced vdi kha nang cung dp tdc dd sdhdu dinh hon IGb/s; tang cudng hoat ddng da anten, da bing tin; vi tuong tbitdi vdi cac tndn khai hidn cd. Tuy nhidn, nhu cau dung luong gia tang chua tung thdy vi vin dang tiep tue didn la, phan ldn li ta cic dudng tmydn video. Du doin ddn nim 2020, mdi nguxn su dung se tieu thu 1 Gbyte dQ heu mdi ngay. Bdn canh dd, dS dam hao thi phan tiong thi tnidng bing rdng di ddng, dc nhi mang cOng can di thidn hieu qua boat ddng vi tang cudng kha ning cho mang. phat trien cae ca hoi kmh doanh mdi, ma rdngpbd tan vibaovesudiu tu cua minh.
Bd li nhung thich thue mi LTE-Advanced Release 12 vi cac Release tiep theo phai dip ung ding nhu li tiep tue md la con dudng de ehuydn sang ky nguyen 5G.
Bii bio gioi thieu nhOng quyet dmh va giai diich chi hdt nhOng cdng nghe duoc dd xuat trong Release 12.
ThS. Dam My H^nh
1. NHU'NG SU CAI THIEN MIMO DL/3D- MIMO
Tiep tuc qui tiinh eua cae cflng nghd anten, nhung ting cudng ddi vdi cac eNB d ldn cfl thd dugc thue hidn phin ldn bing each khai thae phuong phap til sii dung tin sd ngiy cing ting v i suy 0am can nhieu trong midn khdng gian. Do su til sii dyng eac vimg d va mang truydn tai dang tdn tai, cic nha khai thic duac cung d p cic phuong tidn dd ting cudng dung lupng voi chi phi hop ly. Cac thay ddi tidm ning ddi vdi cac die ta phin ldn sd anh huong ddn phan hdi thdng tin tiang thii kdnh (CSl - Channel State Information). Trong dd, d c ting cudng ddi vdi s6 m i chi thi ma ttin tidn m i hda
UE-specific elevation BF/3D-M1MO
H
Hinh 1: Dinh dang chCin M W
2 6 I TAP CHi CNTT&TT KY 1 ( 9 . 2 0 1 4 )
(rao - Preceding Matrix Indicator] d thd cho phdp svmdiOng midn khdng gian tdt hon va d thd h6 tro cic cdu hinh eNB khac nhau. Cic chd dQ phan hdi CSI mdi cOng d thd dugc dugc dua ra.ReL 12 cOng a& chu£n hda md hinh kdnh 3D moi cho phdp md phdng d miic hd thdng mdt d c h chinh xac cho cdng nghd anten MIMO.
2. T R U Y I N THONG MAY DEN MAY (M2M) CHI PHI THAP
S\f ting tmdng manh me ciia luu lupng v i d c thidt hi v i giao tidp M2M duac mong dpi se hd tto ludi didn thdng minh, v$n tat lo0c, siic khde didn tit, ning lugng, d c ung dimg an ninh... Do dd, 0 a o did n vd tuydn LTE se dugc chuin hi dd hd tig mdt d c h hidu qui sii truydn sd lugng ldn cic gdi nhd, khdng thudng xuydn bing cich su dyng cic thidt bt cd cdng suit thip, it phiic t^p vi 0 i rd. MOt sd cdng vide vd Giao tidp Lo?u Miy (MTC - Machine Type Communication) d i dugc chuin hda sin trong Release 11. Nd bao gdm d c ydu d u phyc vu, d c vin dd vd bio mit vi Iddn tnic. Trong dd, chiic ning Udn m^ng MTC vi miy chu co kha ning cung d p dich vu (SCS - Service CapabiUty Server) dugc duih nghia tiong Release 11.
Nhiing ting cudng ding kd quy dudng truydn Hinh 2:
11 dich nhim cOa m^ng niy dd cii thidn tiuydn din ttong nhi. Ching ban mdt sd tiildt bl ngudi su dimg MTC (UE MTC - User Eqmpment Machme Type Communication) dugc cii dit tiong d c ting ham d a d c tda n h i hoic dia didm din cu dupc che chin bdt su d c h nhidt/dch didn/dch im bing d c l i kim lo^ 6 phia sau. cac eua sd bgc kim logi hoic d u true xiy dimg tudng diy ttuydn thdng, nhOng UE niy sd chiu su suy hao tmydn din ldn trdn giao didn vd tuydn hon 6 d c thidt b( LTE thdng thudng. NhOng
ky thuat don gian v i h ^ hen nhit lim keo dii thdi gian phin tip (TTI - Transmission Time Interval), su dtmg rdng rai bd lip HARQ (Hybrid Automatic Repeat Request) cung nhu l i lim ting cdng s u i t
3. LOAI SONG MANG MOI
Qua tiinh chuin hda LTE - Advanced thucmg bi han che bdi d c sdng mang d kha nang tuong Ihich ngugc. Mdt mit, didu niy cho phep su chuydn dieh tidi chiy cho cic phidn bin mdi. Mit khic, nd tao nen cic 0di h ^ ddi vol su dua ra cic cdng n0id mdi. Mdt trong nhimg hiu qua d a su tuong thich nguoc l i nhu d u tmydn din lidn tuc Cac ky hieu tham chidu chung (CRS - Common Reference Symbol) a mgi khung trdn dfl rdng bang cbi ra 6 Hinh 2. Hon thd niia, d c dinh dang do rgng bing tin mdi ed thd dugc dua ra dd hd ttg tit d d c
f, mmnrnmu]
S6ng mang LTDLTE-Advanced v6i c i c ky h i ^ tham chi&i chung CRS.
il I '^''^•' t
Hinh 3: Loai sdng mang mdi vdi truy&i dSn khOng lien tyc
CONG NGHE VIEN THONG
loai dd rdng bang tin. Loai sdng mang mdi cd the hoat dflng nhu la mdt loai sdng mang md rdng cimg vdi d c sdng mang LTEA.TE-A khic hoac nhu sdng mang khflng cd kha nang tuong thich ngugc boat dflng ddc lap.
4. TANG CUaNG CAC 0 NHO Tang cudng mit dfl mang la mflt ttong nhung yeu td then chdt de lim tang hidu qua su dung phd tin. Bang each dua eac UE den gin cae nut mang hon, ty Id tin hidu ttdn tap im va can nhidu SINK (Signal-to-Interference-plus-Noise Ratio) duoe cai thien, lam tang toin bfl hieu nang bing each su dung didu chd/ma hda tuong thich va MIMO. Tuang tu nhu hieu ning be thdng dinh dang chum 3D cd the tdt ban thdng qua tii su dung tin sd, duoc gpi l i ehia d. Anh huong cua mang hdn tap den hoat dflng rat da dang, chang han kha nang Imi lupng ldn, bidn thidn sd ngudi su dung tiong eac d, tinh ddng ciia SINK Idn han, ting tdc do chuyen 0ao. O Hinh 4, kieh ban diu tidn la truy nhip ndi bfl tan so ridng re, tiong dfl cac ldp tin sd khac nhau duge sii dung cho cac d nhd. Va d kieh ban thii hai, ed thd thue hidn tmy nhap nfli bfl tin sd tich hgp, tiong dd eac d macro va pico sir dung cimg tan sd va nhiing d nho duac tich hop ttgn ven vao mang.
Tiiy vao kieh ban, nhiing phuong phap khac nhau dupe ydu cau de phan bfl cac nhan dang fl va de hd ttg cac UE tim thay v i su dung cae d nhd tuang ling. Ddi vdi eac d nhd, die biet khi sir dung cac tan sd eao hon, se ydu cau eac chinh sach mdi va cic nghidn ciiu cimg ton tai can duge Mem soat. Su
dimg cac so do gbdp song cdng diia ttdn TDD cOng ed the dem lai Ira ieh. Phin bd khung dudng ldn/
duong xudng mdt cich linh hoat hon ttong cac cum 6 ridng re cd the khdp vol tinh hudng luu lugng ndi bd, tiic tiidi. Du trir til nguydn va cam bien d p cao cd the dugc ydu eau dd ttinh mflt vai tinh hudng can nhidu. Chic chin rang tmy nhap ndi bg tich hpp day du d tinh hudng thii hai gidng nhu mgt^phuon^
phap tang cudng hidu nang day htia hen. Nhiing d nho chi ma rdng d macro cd cimg n h i n dang ldp vif ly hoae d e nhin dang d ao dang ki ddng duge tai su dung ttong mien khdng 0an. Cac ky thuit phdi hop can nhidu hdn fl ting cuflng (elCIC - enhanced Inter-Cell Interference Coordmation) tmdc diy 0 6 dugc thay the bing su tao ra tinh ddng cho eae fl
"mem" hoic cac d "ao" nhu viy. Giam bdt mdt luong ldn luu luong vdi su bu lai bit M eiia su md rdng pham vi fl la ed the trong tinh hudng nhu trdn. Cic 6 nhd don 0 a n la cung cap mdt dng dan sd lieu nhanh vdi quy dudng tmyen lflu han do ttang thai . a gin cua niit mang. Mat khae, d macro sd eung cip thdng tin he thdng cua d rdng cung nhu l i didu khien tai nguyen vd tuyen bao gdm dinh hudng luu lupng, lua chon sdng mang v i hd tra UE phat hidn d nho d gan ke. Cae loi ich khac la tinh di dpng tiong cic kich ban mang khdng ddng nhat HetNet nhu vay se trd ndn manh me hon va hoat ddng cua cac d nhd tham chi \ib nen trong sudt voi UE ddn noi UE tham chi khdng can nhin ra tmy nhap ndi bd.
Mac khac, kien tnic nay ydu eau su tich hgp ch^t che cae d nhd vao mang bang cic 0 a o didn sidu nhanh hoae bang don vi xu ly bang gdc trung tim.
Dieu niy cd the ngan can su lua chgn da nha cung
Hinh 4- C3C kich ban tang CLOng mat do mang.
2 8 I TAP CHI CNTT&TT KY 1 ( 9 . 2 0 1 4 )
5. TRUYEN THONG THIET BI DEN THIET BI (D2D) LTE
Traydn thdng Thiet bj ddn Thidt bi (D2D - Device to Device) cho phep tmydn thdng true tidp glQa eac UE gin kd nhau. Bdn canh tidm ning tiet kiem ning hipng, glim can nhieu va mo rdng vimg phii sdng, djnh huong then chdt cho nghidn caiu niy li dd bao dam ring 3GPP LTE dip iing cic nhu ciu an toin cdng cOng. Hidn nay, cic cflng nghe khac nhau duoc sir dyng cho d c mang td bao cflng cflng va eho d c mang an toin cdng d n g chuydn dung. LTE vdn sin dugc quing cio nhu la mdt hd thdng an toin cdng d n g cua turaig lai Mdt khi D2D duoc chuan hda, thi tiudng cd thd se thiy nhting dich vu va iing dung dua tidn ttang thii d gin mdi. 6 Hinh 6, bio bidu didu khidn (ching h^n tmy nhip khdi diu, nhin thue, didu khidn kdt ndi) cdng nhu du trti tii nguydn dupc xii ly bdi mang. Theo d c h niy, chit lugng dich vu QoS d thd dugc bio dim vi cic nhi khai thic mang vin didu khidn dupc traydn din. M$c dii su chuan hfla chua bit diu nhung d thd d c so dd trong sudt ddi voi thidt bi ngudi sii dung se dugc ua chudng hon. Cung cd kha ning dudng tmydn vd mydn cho tmydn din sd lidu tidm ning ddn mang dugc duy til mgi Itic. Tuy nhidn, cd thd cd nhOng ydu d u nguoc tii phia an toin cdng cdng nhu tradng hgp su dyng liic d tham hga, trong
(«9»)
/
• / ')) ((<•
Ph&t hi?n tiding thai gan kc
Hinh 6: Truyen thOng Thi^t bj dai TTii^t bi diipc di§u khi&i boi nngng.
dd mang bi hdng edn tmydn thdng giQa eac lite luong an ninh vin cd thd hoat ddng. Didu niy cd thd ydu d u mdt die ta mdi ciing phii hd tig mdt su didu khidn ddc lap boi UE ho^c mflt cidi ket hpp vdi didu Wiidn phin bd 0iia mang vi d c UE.
6. LIEN HOAT DONG VO TUYEN 3GPP/
W I F I
Cto thd thiy mdt sd d c tiam gdc cflng hd tta WlFi tidn thi tradng nhung su lien boat ddng phin ldn bi 061 han bdi chiic ning mang ldi nhu nhin thuc/dp phep/tinh cudc ngudi su dung. Mic dii d$c ta ciing hd tto tinh di ddng, su tdi uu hon nfla cQng se dem lai lgi ieh dd cai tiiidn cin bang tai, glim sit QoS vi eai thidn ti^u tiiu pin 6 UE Ithi su dung cdng n0id WiFi kdt hop chit che vol cac mang td bio. Tiong giai doan diu tien eua n0iidn ciiu niy, vin dd lidn hoat ddng d ldp
Dl Di
Truyen thong D2D
Hinh 5; Giai doan tmydn Vtiimg v i phat hi^n t r ^ g thii gdn k$ cho D2D.
TAP CHI CNTT&TT KY 1 (9.2014)
| 2 9 |
CONG NGHE VIEN THONG
Sqfi quang
P . ^ ! ^ / «
LTE HS VW-Fl
Hinh7:TichhopLTE/WiFi.
vd t t ^ n se diroc nghien ciiu va d c yeu d u se dugc xac djnh de nhin diBX eae giai phip tuong img. Cae ehite nang phat hidn va lim chgn mang WIH hien nay cd the dupc dieu khien bdi cic nhi Itiiai thae. Dieu nay cho phdp thue thi mang mdt each thdng minh hon khi xem xet tai ciia fl hoac tai ciia mang tmyen din, QoS ciia ngudi sit dung hoic chit liKmg li6n kdt vd tuydn ddi vdi d e Mn kdt khae nhau trong sudt hoat ddng dd.
7. NANG CAO TINH DI DONG CUA HETNET
Van de nay ra ddi dua tren ket qua nghien ciiu ttong Release 11, cd the tim thay tiong TR36.839. Tir eac kdt qua md phdng cd the ket luan ring hieu nang chuyen giao ciia mang bdn tap khflng tdt bing su tnen khai mang macro thuin tiiy. Hon the niia, nd cdn chi m ring tde dd UE anh hudng dang ke len hidu ning chuyen giao va cac thiet lap thu khdng lidn tuc DRX (Discontinuous Reception) can than dugc ydu d u de ttanh d c anh huong tidu cue den hidu nang chuyen 0ao. Muc tieu nang cao hidu ning chuydn 0ao tiong mfli tmflng HetNet (ching han ti le hong hdc, tdi thieu d c hieu iing ping-pong, phuc hdi d c hdng hdc tren lidn ket vfl tuyen) cung hd tip tinh di ddng d a UE va chu kl DRX dii hon. Su tang cuflng d e d nhd lien quan
den tinh di ddng eung se dupc thao luan ttong cae' kich ban lidn tan sd. f • Tien trinh phat tndn ciia LTE tiSp tnc manh me tning Release 12 va nhdng Release tidp theo hing su ning cao cac boat ddng cda LTE va LTE - Advance. Bic bidt LTERelease 12 dd cip den su tiien khai dcd nho ngang hing, nhiing su tang cudng doi vdi 6 macro, truydn thong M2M,phithidn tmyen tiidngD2D, tang cudng SON, va die biet li loai sdng mang mdi dio phep tidt Mem ning lucmg cai thien quan ly can nhidu vi tiien khai linh boat Q-ongHetNet. Muc tidu mi LTERelease 12 nham ddn li day manh hieu ning, vung phd vi nhiing Unh vuc mdt hy vong langnd sd dip img disx: su tang tmong cda s6 lieu truyen dan va cac ung dung mm vdi da dang dcym.
cau vi dac tinh ding nhu li tidp din dio sir phat tnen cua cac md thitc tidp theo, die biet la dc cong nghe sau 4G trong Rell4/15.
Tai li|u tham khao
[11. Nokia Siemens Networks, LTE Release 12 md Beyond, Uqid Net, 2012.
[2]. EiKO SEIDEL, 3GPPLTE-A Standardisation in Release 12 and Beyond, Nomor Research GmbH, 01/2013
[3]. Ericsson, LTERelease 12-t^ing another st^ toward the Networked Society, White paper, 01/2013.
