H
d tiidng GSM-R la h?thdng thdng tm di ddng ddnh ridng cho dudng sat dya tren edng ngh^
GSM dl cung cdp dudng tmyen thdng tin vd tuydn phyc vy dilu khidn, gidm sdt dodn tdu vd mot sd djch vy khdeh hdng ea ban. Id mdt phdn cua ERTMS (H? thdng quan ly ehay tdu chau Au) vd dd duge su dung nhieu d ede nude ehdu Au, Tnmg Qudc, Uc...
Hien nay, tdu ehay tde do eao Id xu hudng phdt trien tdt yeu ciia nganh dudng sdt do nd Idm tdng khd nang eanh tranh ttong Hnh vye giao thdng vdn tdi. Khi tdu chay vdi tdc dd cao - vdi tde dd tau d^t tdi 500 km/h, ddp ling duge ede ydu edu cua dudng sdt dk dieu khidn, gidm sat tdu cd hieu qud, vd yeu cdu eua hdnh khach vl cae djch vy thdng tin di ddng bdng rdng, thi hd thdng GSM- R se ttd ndn khdng edn phii hgp. Bdi bao gidi thidu mdt sd vdn dd edn nghidn ciiu khi tridn khai he thdng tiidng tin di ddng dudng sdt tdc dp eao LTE-R dya ttdn cdng nghe LTE "Long Term Evolution".
niAnG LTE-R
Kiln tnic mang cua LTE-R Id tuong ty nhu cua LTE/SAE (Hinh 1) [1]. Cd thd thdy, so vdi GSM-R, kiln true mang eiia LTE-R Id tuang ddi phdng, do do cdc nut mang va so lugng thiet bj edn bdo dudng giam di ddng kl vd vi§c phdt tridn m^ng Id dd ddng hem, do dd chi phi ciing cd thd duge gidm dang kd [4].
LTE-R MS
Hinh 1; Ki«n tnic mang ITE-R. @ CflNG NGHt ThOng tin vd Truydn thOng 13/2016 4]^
Mang truy nhap
Cdu tnic mang truy nhdp ciia LTE-R la E-UTRAN, E.NodeB (evolved- Node B) la thidt hi mang duy nhdt md khdng cd BTS vd BSC nhu hong GSM-R. Phdn hi eNodeB Id mdt niit mang md truyen tin hidu cho thiet bi ddu cudi bode nhdn tin hidu tu thidt bi dau cudi ttong mdt hode nhilu d. Nd ed mdt tdp hgp ede chuc nang Hen quan din tmyen vd thu tai ldp vdt ly eua giao didn vd tuyen, bao gdm ed didu ehd va gidi dieu che, md hda kenh vd gidi md. Ddng thdi, vi khdng ed BSC, nd eiing ddm bdo ehde nang kidm sodt tdi nguydn vd tuyen, qudn ly di ddng va giao didn vd tuydn L2 [2]. Cdc eNodeB ed thd duge kdt ndi den router mang trye tidp ma khdng qua cdc mit didu khiln tmng gian, nhu cde BSC hong GSM-R.
Mang Idi
Mang loi cua LTE-R la EPC (Mang loi gdi tidn tidn). Sy khae bidt dang ke
giiia EPC vd mang Idi eiia GSM-R la EPC mang loi di ddng todn bg IP. Didu nay co nghTa rang tat cd eae dich vy se duge x4^
dyng tten miln PS (chuyen mach goi), bao gdm ed dich vy thoai. HSS (may chii khu vye thue bao) la may chd kho v ^ S o ttdeh nhiem qudn ly thdng tin dang 1 ^ 9 ngudi su dyng. Trong cdu trijc nay, ^ g he IMS (Phan he da phuang tidn IP) cd ede chiic nang gidng nhu cdc chiie nang duge tiiye hien bdi MSC ttong GSM-R.
IMS ddt d tten EPC cung cap cde djch vy da phuang tidn IP. IMS n h ^ hd hy tmyen tdi gdi tin hidu qua, va myc didv chinh eua nd Id dd cho phep cde thi he ede tidu chudn tucmg thich vdi cde djd^
vu IP [3].
He thdng vd tuyen dodn tdu eung c^..
cde dieh vy thdng tin phdi dam bao cac ydu cdu RAMS (tin cdy, sdn sdng, duy tri vd an toan) va QoS (chdt lugng dich vy). Vi vdy LTE phdi cd cac tinh ndog
4 2 CflNG NGHE ThOng tin vi Truyen thOng | 3/2016
dap ling duge ydu eau ve cac djeh vu thdng tin vd tuyen dudng sdt dieu khiln, gidm sdt dodn tdu vd cae dich vy thdng tin vd tuydn dudng sat mong mudn. Dac tinh eua LTE sd dap ling duge eac djeh vy thdng tin ehiic nang ciia dudng sdt duge thi hidn nhu Bdng 1.
Ngodi ra, h§ thdng LTE-R vdi ky thudt edi tiln eung cap djeh vy thdng tin vd tuyen dung lugng Idn, tde dp cao eung ed the ddp ung tdt ed eac djeh vy thdng tin mong mudn hong dudng sdt.
LTE TRONG mdlTRtrdHGDaONG siTTdcoqcAO
Cde hd thdng LTE, Wimax hay 3G phu hgp vdi mdi trudng cd tdc do di chuyen khdng eao ciia thiet bi ddu eudi ngudi diing. Ddi vdi ngudi su dung di ehuydn vdi tdc dp cao nhu nhdn vidn va hanh khach ttdn tdu tdc dp eao thi he thdng thdng tin di ddng hien tai chua the eung edp cdc dicb vu dft lieu tde dd cao nhu vdi ngudi dung di ehuyen tde dd thdp. De cung cdp dudng tmyen vd tuyln bang rdng tin cdy vd dn dinh gifta tau vd mat ddt cd rat nhidu vdn de cdn duge gidi quydt vi khi tau chay vdi tdc do cao nd gdy ra mpt sd vdn dd nhu djch tdn Doppler dae biet Id khi tdu chay gan tdi BS bode qua BS, chuyln giao xay ra thudng xuyen. Fading nhanh hong he thdng thdng tin.... Vi vdy he thdng LTE hong mdi tmdng tde dp eao cua dudng sdt cd nhiing vdn de quan hpng edn dupe ddnh gia nhu:
- Chuydn giao ttong mdi tmdng tde do cao:
Trong hd thdng LTE h§ trg eo ehd chuydn giao eftng HHO (Hard Handover) dl gidm sy phue tap ttong kiln true mang, tuy nhien HHO khdng ddm bdo viec khdng ed gdi tin ndo bi mdt hong qud trinh ehuydn giao. Vi vdy phdi cd ca chl hd hg chuydn giao cho LTE khi nd ftng dyng hong mdi tmdng dudng sat tdc do eao dd dap ung
Bang 1 - C3c d$c tfnh LTE dap irng ySu cdu d|ch v g thflng t i n chuySn d u n g ciia d u f i n g sdt cao t6c
Cac chCrc ndng GSM-R
VGCS
VBS
eMLPP
FN LDA
REC ThiStlSpcuOc ggi nhanh Chuydn d o lieu
^ ^ W ^ OSc tinh LTE ^ ^ E ^ ^
LTE IMS tr6n VoIP (VoLTE) + IMS tren bo dam (PoC) + Dich vg da d|ch vg da phgong tien cJi tiSn (eMBMS) * VoLTE + PoC v S / h o a c eMBMS
Co c h ^ s6ng mang phan Idp truy nhap + Nguyen tic 6\iii khien + co chS QoS (ARP)
SIP * * : Oia chi giao thilc d3u phlsn Oinh VI trong LTE (Release 10)
cac dich vg t i ^ n g noi an toan va khan c3p qua IIVIS trong LTE
IMS tren PoC + sdng mang phan Idp truy nhap
IMS tren dich vg SMS
ede yeu edu vd djeh vu QoS vd RAMS.
Ca che chuyen giao LTE ttong mdi tmdng dae biet nay phdi lien tyc, nhanh vd tdi thidu vide mdt gdi hn. Cd hai phuang an de edi thidn ty Id Idi ehuydn giao hong khi tdi thieu thdi gian ehuydn giao hong mdi tmdng tdc do cao. Phuang an mdt la thyc hidn eo chl chuyln giao mlm SHO (Soft Handover) hong LTE, phuang an nay bao ham mdi ddu cudi ngudi su dyng kdt ndi vdi hai eNode ciing mdt thdi diem, phuong dn ndy tdn ngudn tai nguydn tan sd vd phiic tap hon, tuy nhidn, hong mdi tmdng dudng sat thi dieu ndy ed the chdp nhdn [8]. Phuang an thu hai la tap tmng vao viee tdi uu hda cdc ca ehe HHO hong LTE de gidm thieu vide mdt ban tm, gidm sd Idn chuyen giao, gidm thdi gian ehuyen giao ttong mdi tmdng tdc do cao [9]
CONG NGHE Thdng tin vi Truydn th6ng 13/2016 4 3
- Hieu ling Doppler:
Vide tdu di chuydn vdi tdc dp cao ddn ddn sy thay ddi vd dieu kidn kenh. Dieu che OFDM (Orthogonal Frequency Division Multiplexing) dua vdo LTE sd trdnh duge nhieu ddng kenh ICI (Inter Carrier Interference), tuy nhidn nd edn dupe ddnh gid vdi mdi trudng tdc do eao [10].
KET LUAN
Tdu ehay tdc dp cao Id xu hudng phdt tridn tat yeu cua nganh dudng sat do nd lam tdng kha nang eanh hanh ttong ITnh vye giao thdng van tai. Vide van hdnh vd cung edp cae djch thdng tin eho he thdng vd khach hang ddi hdi nhiing ydu edu cao hem ddi vdi he thdng thdng tin dudng sdt hi?n tai. Vi the vide nghien cuu vd dp dung edng nghe mdi LTE-R dl ddp img nhu edu tiidng tin dilu khiln tdu va thdng tin hanh khdeh ttong he thdng dudng sdt cao tde Id edn thidt.®
TAI LI$V THAM KHAO
[I] LTE/SAE -The Future Railway \&^
Radio System? Long-Term Visions on Rmhkg Mobile Radio Technologies, UIC, 14.09.2009, VO. 4 Draft.
[2] JIA SHEN. Shiqiang Suo. 3GPP Long 7bm Evolution: Principle and System Design, Beijing.
People's Posts and Telecom Press. 2008.
[3] A High-speed Railway MobSg Communication System Based on LTE, 20lO International Conference on Electronics and Information Engineering (ICEIE 2010), Gao Tingling Stale Key Lab of Rail Traffic Contrd and Safety Beijing Jiaotong University Beijii^
CHINA.
[4] ALEKSANDER SNIADYandJOSe SOIER.
Capacity gain with an alternative LTE raih/o}
communication network. IEEE members, 7A International Workshop on C b i n m ^ H ^ H Technologies for Vehicles (Nels4Cars-FaII^^^^
[5] JAIME CALLE-SANCHEZ. MARIANO MOLINA-GARCLi & JOSe I.ALONSO.\
Challenges of LTE to become Next Gen Railway Communication Sysien of Signal, Systems and Radiocomi ETSlT.Technical University of Madrid, '^can, 2012.
[6] BADARD. B. & DLtSCORl BOULMIER, G. etal, Migrationto VoIPom, networks Technical challenges and t opportunity analysts, Telecomm, Network Strategy and Planning (NETWORKS). 2010 14thIntematiorud.V
pp 1-7. 27-30 Sept. 2010. _ [7] CHEN WU. User ID provisioning for SIP
registration in IMS, Education Technology aai Computer (ICETC). vol.2, no.,pp.V2-206-V2-^
22-24 June 2010. ^ ^ [8] QIWEL W & GUANGUANG. R. &-MC
T. , A sofi handover algorithm for TD-LTE 4^'^^
in high-speed railwccy scenario. Signal F>
Communications and Computing (ICSPCC),^^
no., pp.1-4. 14-16 Sept. 201L
[9J L. LUAN el al. Handover ParamOe Optimization of LTE System in Variational
Velocity Environment, Proceeding i ICCTA201I. International Conference on
Computer Theory and Applications, 2011.
[10] REN. X & REN. G. & LE. C, -Carria- frequency offset estimation for PUCCH in hi^
speed train environment, 12ih Imemationd Conference on Electronic Packaging Technology and High Density Packaging, pp. 1-4, Agosto 2011.
4 4 CONGNGHE ThOng tfn vd Truyen thAng 13/2016