System and Method for load balancing in Unified Small Cell Router

Transcription

1 IJISET - Intrnational Journal Innovativ Scinc, Enginring & Tchnology, Vol. 2 Issu 5, May Systm and Mthod for load balancing in Unifid Small Cll outr Murugsan Nallathambi SPVTG Businss unit Cisco Systms India Privat Limitd Chnnai, India mnallath@cisco.com Abstract In a typical connctd hom or corporat ntwork, rquirmnt is to hav a singl dvic to trminat various inputs or singl dvic to provid data and accss srvic. Usr would lik to accss th various things from diffrnt dvic at diffrnt location. Fmto and Pico clls ar srving as an nd point dvic for LTE and Vido Gatway is trminating F and srving vido to th usr via IP mdium. prator and usr rquirmnt is to combin both small clls and Vido Gatway and mak a Unifid Small Cll outr (USC) so that dvic maintnanc and accssibility would b asir. This papr addrss th possibl architctur USC and th factors nd to b considrd in Slf rganizing Ntwork algorithm for USC. Kywords Small Cll; Slf rganizing Ntworks; Vido Gatway; Unifid Small Cll outr I. INTDUCTIN LTE (Long Trm Evolution) is a packt switchd radio accss tchnology standardizd by 3rd Gnration Partnrship Projct [4]. It supports highr data rats (up to 300 Mbps in downlink and 75 Mbps in uplink) and lowr latncy than othr lgacy systms. It supports orthogonal frquncy division multipl accss (FDMA) in downlink and singl carrir frquncy division multipl accss (SC- FDMA) in uplink [5]. Small clls ar low-powr wirlss accss points (APs) that provid improvd cllular covrag for homs and ntrpriss as wll as mtropolitan and rural public spacs. Ths small clls ar also usd to rduc Qos dgradation so that it improvs th data throughput for mobil usrs. This small cll includs Pico cll which covr in th rang 200 mtrs and typically usd in apartmnts and corporat fic. Fmto cll can covr in th ordr 10 mtrs and typically usd in hom. A. About Small Cll Whn thr is a larg numbr small clls, covrag will b improvd but intrfrnc and managing thos dvics will b challnging task. It bcoms important to provid Slf rganizing Ntwork (SN) capabilitis such as dynamic optimization in small cll ntworks so that it will rduc th oprating cost th oprator. This SN includs slf-configuring, slf-optimizing th dvic paramtrs, Load balancing, finding th Nighbor and doing handovr to th corrct dvic whn Usr Equipmnt (UE) movs across th rgion. Load balancing is th SN algorithm by which th small cll ntwork can shar th traffic. With limitation hardwar rsourcs and spctrum, small cll nds to tak dcision whthr to accpt incoming handovr rqust. Also, if nighbor is rady to shar tak som load thn small cll hav to handovr som th UEs to th nighbor. In an LTE typ ntwork, a Nighbor Cll List (NCL) [1] is cratd for ach Usr Equipmnt (UE) and is maintaind by th UE s srving AP. A suitabl AP is chosn from this NCL for handovr whnvr ndd. Cration and updating Nighbor Cll List is a critical activity th oprator. Evry UE masurs th signal rcivd from nighboring APs and masurmnt data in th form frnc Signal civd Powr (SP) or frnc Signal civd Quality (SQ) is mad availabl. It is rportd to srving AP basd on crtain triggrs. n such triggr is calld an A3 Evnt, which occurs whn a masurmnt from nighboring AP is gratr than masurmnt from srving AP by a spcifid fst. Anothr triggr calld an A4 Evnt occurs whn th masurmnt from a nighboring AP xcds a spcifid thrshold. Srving AP for that UE crats NCL (for that UE) using ths masurmnt rports. Slcting th right nighbor basd on NCL is vry important. Wrong nighbor slction can lad to highr call drops or poor connction quality. A packt switchd data ntwork may maintain data / IP (Intrnt Protocol) sssions aftr handovr but QoS may b dgradd as a UE is handd ovr from on 1147

2 IJISET - Intrnational Journal Innovativ Scinc, Enginring & Tchnology, Vol. 2 Issu 5, May AP to anothr AP. It bcoms dsirabl to hav an NCL list that hlps to rduc QoS dgradation upon handovr. It is also ndd handovr dcision nds to b considr th intrnal CPU load and hardwar rsourc limitation. B. About Vido Gatway Vido Gatway (VGW) is a hybrid dvic which inputs ar adio Frquncy (F) input and IP (it can b Ethrnt or cabl modm). adio frquncy input can b com from diffrnt mdium lik satllit, trrstrial and cabl which us diffrnt modulation schm. VGW dmodulat F signal, transcod it. utput VGW is connctd to hom ntwork (which can b Wi-Fi, Multimdia vr Cabl Allianc tc.,). Hom ntworking standard lik Digital Living Ntwork Allianc (DLNA) allows UE to rqust contnt from Gatway and play it on th UE. For xampl, 1. UE asks for list liv channls availabl in F ntwork. VGW gt th rqust, and chck th channl list is availabl in its local cach. If channl list is not availabl, it will tun to F channl, gt th list according to [9] and stor it in its local cach. Th stord channl list will b snd to UE via hom ntwork 2. UE asks channl numbr 1 s vido and audio contnt. n gtting this rqust, VGW tun to F channl #1, transcod it and buffr contnt in its local circular buffr. Th buffrd contnt will b snd to UE via local hom ntwork VGW also trminat th srvic basd copy protction. It dcrypts th contnt basd on oprator and ncrypts it for th hom ntworking (simpl ncryption schm lik DTCP-IP is usd in most th tim). VGW may contain big prsistnt storag (lik hard-disk or compact flash) to stor th vido contnt which can b rtrid/playd back aftr somtim.. VGW usd to contain many F tunrs in ordr to srvic many clints (UE). Most th VGW is dsignd to work alon and work in hom nvironmnt. Whn VGW is dployd in big apartmnts or in ntrpris or in big stadium, it nds to communicat with othr VGW and shar th rsourc. Dploymnt VGW and LTE small-clls ar going to happn in sam plac and almost sam purpos (as Vido is th most traffic in LTE and IP world). Also, most th vido bing watchd in UE instad lgacy st top boxs so it is mak sns to combin both VGW and small cll into a singl box. I. UNIFIED SMALL CELL UTE Figur 1 Unifid Small Cll outr block diagram Figur 1 dscribs th block diagram Unifid Small Cll outr (USC), it has vido tunrs (it can b insrtd via PCI slot or via USB or Ethrnt port) attachd to Pico or Fmto clls. This tunr card will hav tunr PLL, dmodulator (basd on F ntwork) and output intrfac modul. In addition to normal LTE opration, this USC will b having two hardwar componnts. n is to transcod th incoming vido contnt and hardwar is lgacy LTE small cll hardwar. LTE hardwar rcivs th contnt - it can b vido, audio or data (lik channl, rcordd list) from transcoding hardwar and also from IP backhaul. utput USC is CFDM signal or MCA to support lgacy st top boxs. II. SN ALGITHM Considr a cas larg community ara whr popl want to s th high dfinition contnt whrvr thy ar in th community ara; it can b with in th hom or in th common ara or in th markt. And usr xpct smooth transition whn mov out from community ara. Whnvr th UE is in th community ara and watching liv channls, USC will srv that from F tunr. In this way, IP traffic can b avoidd. Whn usr is moving out from currnt srving USC, USC will hand ovr to anothr USC or normal SC basd on currnt UE application contxt and availability small cll. At th tim handovr, if UE is playing liv contnt or from rcordd contnt, SC or USC giv mor prfrnc to USC. Handovr dcision is th combination nighbor's signal strngth, load, prvious history (failur in handovr) and capabilitis. If USC is not availabl and UE is playing liv vido thn USC signal MME (oprator) and it can snd command to th UE to tak vido 1148

3 IJISET - Intrnational Journal Innovativ Scinc, Enginring & Tchnology, Vol. 2 Issu 5, May contnt from unicast UL. If this channl is availabl in Evolvd Broadcast Multicast Signal thn UE will join into this broadcast and gt th signal from EnodB. Evolvd Broadcast Multicast Signal is th standard by which vido can b broadcastd/multicast in LTE, bcaus bandwidth limitation, vido quality in this mod transmission may b lss compar to high quality vido availabl in F. TABLES I Srvd cll Information Mssag No tabl figurs ntris found. Numb r Tunr Storag Prsnc ang IE typ and rfrnc 0 or 1 Smantics dscriptio n Numbr Tunrs attachd to th SC. If this valu zro mans, thn SC dosn't support VGW functionali ty Indicat storag supportd Figur 2 SN Algorithm C. Nighbor Cll List Mchanism USC maintains th nighbor list and ach nighbor list's capabilitis (it includs it has support for vido tunrs, how many rsourc availabl tc., ). Thr ar lot prior art [1] to dscrib how to prpar Nighbor lation Tabl (NT). Most th NT algorithm us A3 or A4 vnts from UE and by doing th slf-masuring. Basd on th powr lvl nighbor (it varis basd on UE moving dirction) it assigns priority to SC and this list will b sortd basd on priority. In th background, srving SC will try to stablish th X2 intrfac to th top fw nighbors. It gt various factors lik numbr tunrs, hav rcording capabilitis, load availabl tc., th cll list algorithm uss ths variabls and rcalculat th priority. X2 is th point-to-point intrfac btwn two NBs within th E-UTAN. A point to-point logical intrfac should b fasibl vn in th absnc a physical dirct connction btwn th two SCs[3]. To addrss USC rquirmnts, w ar proposing following changs in [3] 1. "Srvd Cll Information in can b addd with following variabls 2. "Load Information" mssag is snt by an SC to transfr load and intrfrnc co-ordination information. Following filds can b addd into this information to dscrib Vido Gatway functionality in SC TABLE II Load Information Mssag IE/Gro up Nam Availabl numbr playbac k sssion Prsn c ang IE typ and rfrnc Smantic s dscripti on Numbr Tunrs availabl in th SC or Numbr playback sssion (it can b from local storag) possibl with currnt 1149

4 IJISET - Intrnational Journal Innovativ Scinc, Enginring & Tchnology, Vol. 2 Issu 5, May powr mod numb r powr mod load. If this valu zro mans, thn SC can't tak nw vido playback rqust indicats currnt powr mod USC D. Load balancing Mchanism USC has two sparat hardwar ntity, it is ncssary to switch f som componnts whn not in us. By dfault, all attachd tunrs and vido hardwar is powrd f in USC. At uniform tim intrval, USC stwar waks up and collcts th Mta data from th F path and kps it in th local storag. It is also possibl that this hardwar can b wak up by th schduld rcording. This schduld rcording can b happn at local storag or storag shar by many USC (common cloud storag for th particular community or ntrpris). Th load balancing algorithm mntiond in prior art [7] is, Loop: 1) Gt potntial Targt NBs list for Handovr. 2) Sort abov list basd on priority NBs (priority == availabl rsourc blocks and nighbor's nighbor load). Gt availabl rsourc blocks via X2 and nighbor's nighbor load from srvr. Final list will b Targt EnodB which can accommodat many UEs ar listd first 3) Incras Handovr valu by on stp 4) With th modifid Handovr fst, chck how many UEs can b handovr. Chck for ach UE, how many rsourc blocks ar rquird. 5) Tak on Targt cll from cll list, compar numbr availabl rsourc with UE rquird rsourc - if cll can accommodat thn start H 6) Do th stp 5, till all UEs ar handovr or cll list xhaustd with this modifid Handovr fst 7) Go Loop: - if still currnt cll is having mor load In addition th abov, USC nds to do following whil handovr or whil accpting th incoming rqust. 1) USC advrtis its currnt rsourc status via Load information mssag 2) n accpting ach vido rqust, it dcrmnts "Availabl numbr playback sssion". It is possibl that singl UE can consum multipl playback sssion (on is watch th contnt and anothr to rcord) 3) Whn currntly srving UEs ar asking for mor vido rqust (opning multipl straming application) which USC couldn't handl with rquird Qos thn a. USC tris to trminat th old unusd sssion b. Handf th sssion which can b handld by othr frindly nighbor. For xampl, rcording to th common community storag can b handld by th frindly nighbor (which can b far away from srving USC) c. Handovr UE (which ar gtting nough signal powr from th nighbor) to th appropriat nighbor. If SC (which support vido) is availabl thn giv mor priority to th UE which is using vido sssion currntly. 4) Accpt UE basd on its policy (som UE has th rquirmnt to play multipl vido contnt at th tim handovr) and currnt rsourc availability. 5) Promot th USC go to standby, so nvr try to wak up a dvic if th UE can b srvd from anothr USC. Giv low priority th USC which is having "currnt 1150

5 IJISET - Intrnational Journal Innovativ Scinc, Enginring & Tchnology, Vol. 2 Issu 5, May powr mod" is st to VGW dp standby in load information. III. ESULTS Figur 3 Analysis byts consumption in LTE backhaul Figur 3 rsults is takn with th following paramtrs Distanc 0 Without USC With USC mtr Numbr USC-Pico cll rquird USC has connctd with 8 F tunrs - 3 * 8 = 24 2 USC is connct with 5 F tunrs - 2 * 5 =10 So, totally 34 liv vido sssions can b srvicd from this USC from F channl. So, if 34 sssions ar activ at a tim and ach srving HD channl 12 Mbps total 179 Giga Byts IP traffic can b avoidd V. EFEENCES [1] Yoshinori Watanab, Yasuhiko Matsunaga, Kosi Kobayashi, Hiroto Sugahara, and Kojiro Hamab, Dynamic Nighbor Cll List Managmnt for Handovr ptimization in LTE, IEEE Vhicular Tchnology Confrnc (VTC Spring), 2011 IEEE 73rd. [2] 3GPP TS LTE; Evolvd Univrsal Trrstrial adio Accss (E-UTA) and Evolvd Univrsal Trrstrial adio Accss Ntwork (E- UTAN); vrall Dscription;Stag 2 [3] 3GPP TS Evolvd Univrsal Trrstrial adio Accss Ntwork (E-UTAN); X2 application protocol (X2AP) [4] 3GPP spcifications, [5] H. Holma and A. Toskala, LTE for UMTS FDMA and SC-FDMA basd adio Accss, John Wily & Sons Ltd., 2009 [6] Small Cll Forum, [7] Andras Lobingr (NSN), Szymon Stfanski (NSN), Thomas Jansn (TUBS) and Irina Balan (IBBT), "Load Balancing in Downlink LTE Slf- ptimizing Ntworks". socrats.org/fils/prsntations/scates_20 10_VTCSpring%20%20LB%20prsntation.pdf [8] Muksh Tanja, Vikas Bangalor, Gajanana Garuda, Murugsan Nallathambi, Shishir Gupta, Policy basd Automatic Nighbor lation Managmnt for small cll Ntworks [9] Digital vido broadcasting spcification for Srvic information(si) in DVB systms /300468/ _60/n_300468v pdf IV. CNCLUSIN W hav proposd nw possibl product which will srv th usr rquirmnt to watch from anywhr with limitd usag IP. In this way, w ar proposing to us F channl whn it is availabl. This will rduc th LTE backhaul traffic and srvr load. W hav also proposd mthod to do load balancing and communicat th load information rlatd to vido hardwar. This product would b bnficial to th oprator who is running both F channl and LTE ntwork. 1151