GIAI PHAP TOI UtJ DINH Hl/OnVG MIEN CHO CAC U N G DUNG TRUYEN VIDEO QUA MANG DANG LlTdl K H 6 N G DAY
TS. Vd Nguyen Sffn, ThS. Huynh De Thu, KS. Hd Thi Bich Phuffng Khoa Dien -Dien td vien thdng Tdm tat: Trong bdi bdo ndy, chiing tdi gidi thieu mgt gidi phdp tdi uu dinh huang mien, mem deo, nhdm gidi quyet cdc vdn di tiiu tdn nhiiu tdi nguyin, ldi kenh vd tri hodn da chdng nhdm ndng cao chdt luang trdi nghiem (QoE - Quality of Experience) cho cdc img dung truyin video qua mang da chdng dgng luai khdng ddy (multihop Wireless Mesh Networks - WMNs). Trong gidi phdp de xudt, chung tdi xdy dung mdt bdi todn tdi uu dua vdo viec phdn tich mdi quan he giiia mien ngudi diing, mien ky thudt, vd mien tdi nguyen. Gidi bdi todn tdi uu ndy se cho phep ndng cao hieu suat truyin video. De thdy ro dugc uu diem cua gidi phdp, chitng toi trinh bdy mdt nghien ciru cu the cd tin ggi Id "Ket hgp tdi uu QoE vd tdi nguyen mang trong chinh sdch lap cho video theo yeu cdu (Video on-Demand - VoD) qua WMNs dp dung thiet ke xuyen lap ".
Abstract: In this paper, we introduce a jlexible plane-oriented optimization problem to overcome the problems of resource consumption, the lossy channels, and multi-hop delays, so as to improve the Quality of Experience (QoE) for video streaming applications over multihop wireless mesh networks (WMNs) Particularly, by analyzing the mutually mathematical relationship between the user plane, technique plane, and resource plane, we propose a framework of optimization problem This flexible jramework enables us to provide further solutions for high video streaming performance. To demonstrate the benefits of the proposed jramework compared to other existing optimization solutions, we present a case study named "Joint QoE and Resource of Network Optimized Replication Strategy for Video on-Demand (VoD) over WMNs: A Cross-layer Design Approach ".
Keywords: Plane-oriented optimization, replication strategy, streaming performance 1. Gidi thieu
Mang da chang khdng day dang ludi (multihop Wireless Mesh Networks -WMNs) dugc xem la mgt cdng nghd day bua ben vdi nhidu uu didm vugt frdi nhu ty td chuc, tu ciu hinh, ty phye hdi, tin cay va kha nang md rdng [1]. Nhiing lgi thd nay cho phep WMNs dd dang tridn khai va quan ly, ben vung va tidt kiem ttong cac dd thi ldn dd cung cap cho ngudi dimg cac umg dung bang thdng rdng, tdc do cao. Trong Hinh 1, mdt WMN didn hinh bao gdm cac bg dinh tuydn tuong ddi cd dinh, tao thanh mgt mang xuong sdng khdng day da chang. Kien tnic ciia mang xuong sdng nay co thd md rdng bang co chd chuyen tidp da chang, nang cao thdng lugng nhd cu ly truygn mdi chan ngan hon va lang lhdi gian sdng cua mang nhd cdng suat truyen qua moi chang thap hon.
Cac ling dung truyen video cho phep ngudi dung kich boat va xem ngay lap die thay vi chd den khi video dugc tai vd. Chiing cd mdt sd chi tidu phirc tap ridng ve chat lugng trai nghiem (Quality of Experience - QoE), hoac chat lugng binh anh cam nhan bdi ngudi diing. QoE thdng thudng gdm cac
chi tieu nhu: kha nang truy cap cao, xem mdt each lidn tuc,... Va do do, nang cao QoE ludn la thach lhiic ddi vdi cac nha nghidn Cliu, tridn khai VSAs.
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Hinh 1. Kien tnic dien hinh cua WMN Trong truyen VSA qua WMNs, mac dii WMNs cd nhieu lgi thg, chiing ta khdng thd bd qua nhiing van dd cd hiiu cua vide mat dii lieu qua kdnh tmyen khdng day, su cham trd da chang, va sy khdng ddng nhat bang thdng giiia cac kdt ndi khdng day. Trong khi dd, lruyen video rat nhay cam vdi tat ca nhirng vin dd nay, dac bidl la sy cham fre da chang.
Vdi su phat tridn nhanh cua VSAs, nhidu nghign ciiu da tap tmng vao viec lam thg nao dg nang cao hieu suat ciia VSAs qua WMNs bang each sir dyng cac ky thuat kha thi nhu
dem, lap, dinh tuygn, chinh sach rdt gdi, phan bd tdc dd bit, thidt kd xuydn ldp,... Bai bao nay gidi thieu mdt giai phap tdi uu dinh hudng midn (mign ngudi diing, mien tham chigu OSI 7 Idp va mign lai nguyen mang).
2. P h a n tich bai toan n a n g cao hieu suat cua VSAs q u a W M N s
Dd phan lich dugc bai toan tdi uu, chiing ta can phai tim hidu ro mdi quan he giiia 3 thuc the chinh ttong mgt he thdng tmyen video qua mang khdng day bao gdm: video, tai nguyen va dac tinh mang, va ngudi sii dung. De dang thay rang, chat lugng va ngi dung ciia video ciing nhu dac tinh mang khdng day cd mdi quan he true tiep vdi ngudi su dung. Vi dy nhu: video chat lugng kem, ndi dung khdng bay dugc tmydn ttong mdi trudng khdng day vdi nhidu, giao thoa va tri hoan ludn bien ddng, chac chan se khdng lam hai Idng ngudi su dung. Xet mdi quan he ciia ca 3 thuc the ttdn, mdt video HD (High Definition) dugc ma hda d tdc do dii lieu cao se tieu tdn rat nhidu tai nguydn mang nhung dieu nay Iai khdng dam bao lam hai long ngudi sir dung khi lruydn qua mang khdng day [2].
Trong 3 thuc thd ttdn, cac dac tinh mang khdng day dugc qui dinh bdi cac Idp thap (vat ly, didu khien tmy cap phuang tidn truydn lhdng, mang) cua md htnh ISO 7 ldp.
Trong khi dd, cac dac tinh cua video va cua ngudi sii dung thudc Idp iing dung. Do do, frong cac ling dyng truyen video qua mang khdng day, hieu xuat cao khd cd thd dam bao ndu ap dung giai phap tdi uu dua tten mgt ldp ddc lap lhdng thudng.
(1)
AppHcaUon Layer
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QoE
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Hinh 2. Mo hinh toi uu djnh hudng mien Tir da>;, chiing tdi cd thd dua ra md hinh giai phap tdi uu dac ta mdi quan he giiia 3 thuc thd ttdn tucmg img vdi 3 midn nhu frong Hinh 2. Gia sir cac md hinh toan cho cac ldp hoac mien la A, B, va C nhu ttong Hinh 2, bai toan thii nhat cd thd dat ra la: Iam thg nao de tan dung tdt tai nguyen san cd C dd cyc
dai hda QoE frong mdi quan he ch^t che vdi A va B. Vd toan hgc, bai toan tdi uu nay dugc md la nhu sau:
max QoE = f(A,B) St. C < C*
Tir bai toan dugc ndu frong (1), chiing ta cd thd thuc hidn bai loan thii hai, la bai toan doi nghl cua (1). Muc dich la lam thd nao de cue tidu hda tai nguydn mang thda man chat lugng video QoE cho trudc. Bai toan nay dugc md la idiu sau.
min C St. QoE - f(A,B) > QoE*
Giai cac bai toan tdi uu (1) hoac (2) frdn, hieu suit cua VoD qua WMNs se dugc nang cao. Dg thay dugc deu nay, chiing ldi se trinh bay mdt trudng hgp nghidn cim cy thd cd ten ggi "Ket hgp QoE va tai nguyen mang tdi uu chinh sach lap VoD qua WMNs ap dyng thidt ke xuydn Idp".
3. Ket h g p t6i uu QoE va tai nguyen m a n g t r o n g chinh sach lap cho VoD q u a W M N s d u n g thiet ke xuyen ldp
3.L Cu the hda mo hinh toi un Dd trign khai md hinh tdi uu frong Hinh 2, vide dau tidn can thuc hidn dd la cu the hoa md hinb nay. Trong dd, cac thudc tinh cua ngucri dung, cac van dd lien quan den video (cac tieu chuan, phuang phap ma hda, md hinh tdc do - meo ngudn, ...) va cac d^c tinh ciia mang khdng day phai dugc nghidn Cliu mdt each chi tidt. Vide nghidn ciiu nay se la CO sd dd phan tich va he thdng hda cac thyc thd vao mdt md hinh tdi uu dinh hudng mien. Tai cac ldp va mien, nhiing ky thuat cu thd se dugc nghien ciiu dya frdn thidl kd xuydn Idp (cross-layer design) - mgt giai phap thiet kg da va dang dugc ap dung phd bign lrong mang khdng day va da dugc chiing minh tinh hidu qua ciia nd so vdi cac ky thuat tdi uu ddc lap ttdn timg ldp [3, 4].
Cac ky thuat cd the dugc ap dung dd nang cao hieu suat cua VSAs qua WMNs bao gdm: 1) Phan bo ldi uu tdc do bit dya trdn thiet ke xuydn ldp nham nang cao QoE tai ldp umg dung; 2) Hoach dinh phat, dinh tuydn tot uu tai cac Idp thap (didu khidn truy nhap mdi trudng, mang) dya ttdn thidt kd
xuydn Idp n h i m nang cao QoE; 3) Phan bd tai nguyen mang dua fren thidt ke xuydn ldp nham nang cao hieu qua sir dyng; 4) Kgt hgp cac ky thuat dya lren thidt kd xuyen Idp nham tdi uu QoE va tai nguydn mang.
Trong nghidn cuu nay, chimg tdi ap dung cac ky lhuat: chinh sach lap va phan phdi tdc do bit (rate allocation) dd nang cao QoE vdi mgt tai nguydn mang cho trudc (1).
3.2. Mo hinh chinh sach lap thiet ke xuyen Idp
Trong WMNs, VSAs cho phep cac gateway thyc hien viec lap cac phan doan (segment) cua mdt video thinh hanh dang dugc yeu lhich. Muc dich ciia vide lap la dd dua cac phan doan nay ddn gan ngudi dung ban, va do do, ngudi dung cd lhd tmy cap dugc video trong mang xuang sdng cua WMNs thay vi phai truy cap tir Intemet.
Mac dli chinh sach lap la kha thi dd nan^
cao QoE, nd tidu hao tai nguydn ciia mang ve mat dung lugng luu trii cua mang. Tham chi, ngay ca chinh sach lap tao ra sy dan ttai bang thdng tieu thu trgn mang xucmg sdng cua WMNs, chung ta khdng lhd bd qua lhuc td rang: ngudi sir dung dimg cac thidt bi khac nhau (vi du: PDA, may tinh xach tay va may tinh) vdi bang thdng truy cap gidi ban khdng ddng nhal. Ro rang, ndu mdt video tryc tuyen dugc truyen d do phan giai cao, phu hgp vdi may tinh hoac may tinh xach tay thi cac PDA khdng dii kha nang theo kip vdi ldc do dii lieu dgn dg giai ma. Vi vay, chinh sach lap can quan tam dgn vide tdi uu tdc do ma hda ciia mdt video d mirc hgp ly de dap iing sy khdng ddng nhat ve bang thdng Iniy cap ciia ngudi su dung cung nhu hieu qua su dung bang thdng cua mang.
Hidn nay, rat nhieu chinb sach lap (cd hoac khdng ap dung thidt kg xuygn ldp) deu nham nang cao kha nang truy cap dii lieu cho ngudi dung frong cac mang da chang khdng day [5-7]. Nhiing chien luge nay chi co the ddp ling yeu cau xem lidn tuc cho ngudi diing khdng dap iing day du cac khia canh cua QoE cao ciing nhu khdng hidu qua ttong vide sii dung tai nguyen cua mang. Dd giai quydl nhugc diem cua cac giai phap hi?n lai, chiing tdi dd xuit giai phap lap dua frdn thidt kg
xuyen Idp cd ten ggi la CRS (Cross-layer Replication Sttategy).
Aopltcabon paran
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Hinh 3. Mo hinh thiet ke xuyen lap CRS CRS dugc thiet kg nhu mdt giao dien mdi dat giua cac Idp giao thiic [8]. Cu the, mdi ldp lap trung gian (Replication Middleware Layer - RML) dugc tao ra giiia Idp ling dyng va cac Idp thap (ldp mang, Idp dieu khien truy cap phuang tien tmyen thdng va Idp vat Iy) nbu dugc md la ttong Hinh 3.
RML thyc hien vide thu thap cac thdng sd va luu trii chiing ttong mdt ngan xep (Profile Stack - SP). Sau do, cac thdng sd nay dugc xii Iy cho chich sach lap tdi uu.
Trong chinh sach lap, trudc hdt, gateway se theo doi cac dac tinh phd bidn giira cac video va dac linh phd bien giiia cac phan doan cua mdi video (intra popularity).
Trong qua trinh theo doi tinh phd bidn, ndu mdt video lrd nen du hap dan (dugc truy cap bdi nhidu ngudi su dung), ldp iing dung ciia mgt gateway se quygt dinb luu trii mgt sd thdng sd CO ban ciia video nay bao gdm: 1) tdc do video; 2) kich lhudc video; 3) mdi quan he giiia tdc do bit va meo hay cdn ggi la md hinh meo nguon ciia cac khung hmh, ciia cac phan doan, hoac ciia loan bg video va 4) cac dac tinh phd bien hidn tai ciia video.
Tit ca cac thdng sd nay dugc luu frii vao SP dd su dung cho vide tdi uu chinh sach lap.
Ngoai ra, SP dugc dung dd luu frii dinh ky cac thdng sd ve tai nguydn mang ciing nhu ciia cac ldp thap hon vi du nhu: fri hoan hang dgi tai Idp mang, bang thdng dam bao va gidi ban truygn Iai tai ldp dieu khien truy cap phuang tien truygn thdng va ty Id Idi bit tai ldp vat ly. Cac thdng sd nay dugc thu lhap qua cac chang trong mang thong qua cau tnic lidn kdl mang Idp chdng [3].
Dya fren co chg lham dd dinh ky, khdi chiic nang quan ly lap se Irich xuat tat ca cac
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thdng sd hien tai cua mdt video dugc luu ttong SP. Sau do, RM yeu cau khdi chiic nang tdi uu QoE va tai nguydn tinh loan tdi uu hda nham: 1) Tinh sd lugng phan doan video phli hgp tuy vao kich thudc video va dung lugng bd nhd cua ngudi diing dugc quan ly bdi bd dinh tuyen; 2) Tim ra mat do lap tdi uu cho timg phan doan video va phan phdi ldc dp bit tdi uu cho timg khung aiih cua timg phan doan video dd chinh sach lap dugc tdi, tang QoE vdi rang budc vd tai nguyen mang (bang thdng va dung lugng bd nhd) cho trudc.
Thdng qua RM, QRO se gdi phan phdi tdc do bit tdi uu ve ldp iing dyng de ma hda lai video. Sau khi ma boa, mdi phan doan video va mat dp lap tdi uu ciia nd dugc chuydn ddn dich vu trien khai phan phdi dd thyc hien chich sach lap gdm 3 giai doan;
lap, duy lri va hoan tai [9].
3.3. Ketquad^tdurrc
Bai bao khdng trinh bai chi tidt bai loan tdi uu dd nang cao QoE ttong rang budc vd tai nguyen mang cho Irudc va cac thdng sd cung nhu phuang phap thyc hien md phdng.
Til ca cac van de nay dugc de cap trong [9].
3.3.1. Danh gia hidu suat
Dd danh gia hieu suat ciia giai phap CRS, chiing tdi so sanh CRS vdi MAC (Minimum Access Cost) [5], MQC (Minimum Query Cost) [6], va PRS (Proportional Sttategy) chinh sach lap khdng tdi uu.
a) Hieu xudt truy cdp dit lieu
dd tim thiy video. Khoang each ttung binh cang thip, kha nang tim thiy video cang cao.
Trong Hinh 4, CRS va MAC dat hidu suit truy cap video cao nhit, hay ndi each khac, vdi CRS va MAC, ngudi dimg se nhanh chdng dugc xem video hon so vdi MQC va PRS. Trong Hinh 4, a la be sd dac trung cho cu xir cua ngudi dung [12],
b) Hieu sudt ve tinh lien tuc Sau khi video dugc tiin thiy, cac phan doan video phai dugc truyen mgt cdch lidn tyc ddn ngudi diing. Ddnh gia tinh lien luc trong qud trinh xem video, chiing tdi diing tidu chi khoang each truyen cyc dai trung binh (AMTD) tu didm lap ddn ngudi diing.
AMTD cang thip thi tinh lidn bic cang cao.
Hinh 5 cho thiy, vdi CRS/MAC, ngudi dung it cd cam giac bi gian doan ban frong qud trinb xem video so vdi MQC va PRS.
Hinh 4. Hieu suat truy cap video Khd nang truy cap dii lieu la kha nang tim thay video sau khi nguiri sii dung gdi yeu cau, hay con ggi la ty le lim thay video dugc danh gia thdng qua khoang each trung binh
Hinh S. So sanh hieu suat ve tinh lien tuc c) Hieu sudt ve chdt luang hien thi
Hinh 6. So sanh hieu suat ve chat luong hien thi Khi da dam bdo rang cac phan doan video dugc lruyen ddn ngudi dung mdi each lien fric, mdt tidu chi rat quan ttgng khdc cin phai dugc xem xet danh gia do la chat lugng hidn thi ciia video. Thdng sd thudng diing dd ddnh gid tidu chi nay dd la PSNR (Peak Signal-to-Noise Ratio). PSNR trung binh cang cao, chil lugng hidn thi cang tdt. Doi vdi tidu chi nay, CRS cho kdt qua tot nhit so vdi cac phuang phdp cdn lai (Hinh 6).
Ngudi su dung cd the chi cin PSNR tnmg binh khdng cao lim nhung do dao ddng chat lugng giiia cdc khung dnh hoac giiia cac phan doan video phai thap hay do dn dinh chat lugng phdi cao.
d) Hieu sudt vi do on dinh chdt luang Dd danh gid tidu chi nay, chiing tdi diing thdng sd do lech chuan ciia PSNR. Do lech chuan cdng ldn, dg dao dgng cdng ldn. Nhu frong Hinh 7, CRS cho kdt qua tdt nhat vd do dn dinh chat lugng hidn thi.
Hinh 7. So sanh hieu suat ve dp on dinh chat lugng 4. Ket luan
Bai bao vira dd xuat mgt giai phap tdng quat nham tdi uu hidu xuat ciia VSAs qua WMNs. Trong giai phap nay, cac thuc the quan frgng cua iing dung truydn video qua mang khdng day dugc phan tich va md hinh hda frong mdt bai toan tdi uu hidu sual truyen video (cue dai QoE vdi mgt tai nguyen mang cho trudc hoac cyc lieu hda tidu hao tai nguyen mang vdi mgt ngudng QoE dii cao cho frude). Dd minh chimg cho tinh hieu qud, mgt nghien cim cu the dugc xem xet ttong bai bao. Trong nghidn ciiu nay, bai todn cyc dai hda QoE vdi mdt tai nguyen mang cho trudc dugc giai quydt. Kdl qua mo phdng da cho lhay linh uu vidt ciia gidi phdp.
Tai lieu tham khao:
[1] I F . Akyildiz, X. Wang, and W. Wang,
"Wireless mesh networks: A survey,"
Computer Networks, 2005, vol. 47, no.4, pp. 445-487.
[2] Du Xu, Nguyen-Son Vo, et al, "Rale- user- perceived- quality aware replication sfrategy for video stteaming over WMNs," KSIl Trans, on Intemet and Information Systems, Nov. 2011, vol. 5, no. l l , p p . 2 1 0 3 - 2 1 2 0 .
[3] Y. Andreopoulos, et al, "Cross-layer optimized video stteaming over wireless multihop mesh networks," IEEE J. on Selected Areas in Com., Oct. 2006, vol.
24, no. I I , pp. 2104-2115.
[4] D. Wu, S. Ci, and H. Wang, "Cross-layer optimization for packetized video conunun. over wireless mesh networks,"
in Proc. of IEEE Int. Com. Conf, May 2008. Beijing, China.
[5] S. Jin and L. Wang, "Content and service replica sfrategies in multi-hop wireless mesh networks," in Proc. of Int. Symp. on Modeling Analysis and Simulation of Wireless and Mobile Sys., Monfreal, Canada, Oct. 2005, pp. 79-86.
[6] E. Cohen and S. Shenker, "Replication sttategies in unstructured peer-to-peer networks," in Proc. of ACM SIG., Aug.
2002, PA, USA.
[7] A. Derhab and N. Badache, "Data replication protocols for mobile ad-hoc networks: a survey and taxonomy," IEEE Com. Surveys & Tutorials, vol. 11, no. 2, pp. 33-51, Jun. 2009.
18] V. Srivastava and M. Molani, "Cross- layer design: a survey and the road ahead," IEEE Com. Magazine, vol. 43, Issue: 12, pp. 112-119, Dec. 2005.
[9] T. Q. Duong, Nguyen-Son Vo, et al,
"RepHcation sfrategies for video on- demand over WMNs: A cross-layer optimization approach," Chapter 15 in Using Cross-Layer Techniques for Com.
Sys., Eds. H. F. Rashvand and Y. S.
Kavian, IGI Global, USA, accepted. A part of this chapter was presented in I C C ' l l , Kyoto, Japan.
[10] L. Breslau, et al, "Web caching and zipf-like distributions: Evidence and imphcations,"in Proc. of IEEE INFOCOM, Mar 1999, New York, NY, USA
Ngay nh|n bai: 06/10 nam 2013 Ngay chip nhan dang: 17/10/2013 Phan bign: TS. Vo C6ng Phmrag
