Trm pht sng ti gia FemtocellFemtocell l g ? Trong mng thng tin di ng t bo, sng raio c ph nh vo cc trm pht sng BTS. Mi mt BTS s ph mt vng gi l cell (t bo). Nhiu cell c thit k cn k nhau ph sng trn din rng. Chnh v cu trc ny m mng thng tin di ng cn c gi l mng t bo hay mng t ong. Trong mng thng tin di ng t bo truyn thng, chng ta thng nghe nhc n macrocell (t bo v m, c bn knh ph ln tm km), microcell (t bo vi m, c bn knh ph gii hn vi trm mt). Vi s pht trin ca mng thng tin i ng t bo, ngi ta cn thit k cc picocell (vng ph tng t nh mt AP WiFi) tng kh nng ca h thng v tng tc truyn thng.

Gn y, khi nim femtocell mi c ra i.Femtocell l mt trm pht sng nh ca mng thng tin di ng t bo c dng nng cao cht lng dch v v cung cp cc dch v gi tr gia tng phm vi gia nh hay vn phng, cng s. Femtocell c xem nh trm pht sng trong nh (home base station) hay im truy nhp mng t bo ging im truy nhp WiFi. Femtocell l cng kt ni ca mng thng tin di ng t bo t ti nh khch hng. S khc bit ln ca femtocell so vi cc macrocell hay microcell truyn thng l femtocell kt ni vi mng ca nh cung cp dch v thng qua mng c nh bng rng nh DSL hay cp, thay v thng qua mng ring ca nh cung cp dch v di ng. Femtocell l mt gii php cho hi t c nh di ng, cung cp kt ni tc cao cho ngi dng trong nh. Nhng tim nng v dch v a phng tin trong tng lai chnh l n by cho vic trin khai femtocell. y l mt gii php thay th cho gii php hi t c nh-di ng UMA (Unlicensed Mobile Access) hin gp khng t kh khn trong vic thu ht ngi dng. S khc bit ln nht gia UMA v femtocell l femtocell s dng cng giao din v tuyn nh mng thng tin di ng thay v dng WiFi. Do vy, ngi dng femtocell khng nht thit phi trang b in thoi dual-mode (c th kt ni vi WiFi v GSM/UMTS). ng lc cho gii php femtocell Theo nghin cu gn y ca ABI Research th n ht nm 2011, s c hn 70 triu femtocell c bn ra th trng, cung cp dch v cho khong 150 triu ngi. Con s ny tng ng vi mt phn ba doanh thu ca th trng Wi-Fi, tc tm 2 t la. Cn theo mt d bo ca cng ty t vn OVUM th ring Ty u, tnh n 2011 s c khong 11 triu femtocells c ci t. Thc t cho thy c hn 30% cuc gi di ng v hn 35% ngi dng dch v Tivi di ng khi ang ti nh. Li ch m cng ngh ha hn mang n cho ngi dng:

Gim chi ph gi in thoi di ng ti nh. C mt kt ni tt, cht lng dch v tt hn, tc cao hn

Tit kim nng lng tiu tn Cui thng ch cn chi tr mt ha n duy nht cho c in thoi c nh v di ng Nhiu ngi c th cng dng chung mt femtocell (femtocell hin ti c th h tr ng thi 5-6 kt ni di ng ).

Li ch cho nh cung cp mng di ng:

Cnh tranh cng nh gim mi e da t cc dch v VoIP ca nh cung cp dch v Internet. Tng s tri nghim ca khch hng v gim vic khch hng b sang dng mng ca nh cung cp khc. Tng cht lng ph sng trong cc cng trnh cng nh tng dung lng v cc dch v gi tr gia tng cho ngi dng. Tng doanh thu bnh qun ca mt thu bao/thng ARPU

Khuyn khch ngi dng s dng 3G hay WiMAX, t tng s thu bao 3G, WiMAX trong tng lai. Nh vy, gii php femtocell ha hn mang li li nhun v tin ch cho c nh cung cp dch v ln ngi s dng dch v. Cc gii php cho php kt ni t femtocell n mng li di ng (core network CN) Trong mng thng tin di ng th h th 3G UMTS, cc trm pht sng Node B (bao gm cc macro-cell, micro-cell hay c pico-cell) kt ni trc tip vi khi iu khin mng v tuyn RNC (Radio Network Controller) bng ng truyn dnh ring nh E1/T1. Cc RNC ghp cc lu lng d liu t cc Node B trc khi gi chng n mng li di ng. RNC phn pht lu lng thoi (ca mng chuyn ni mnh) n cc tng i MSC (Mobile Switching Center) thng qua giao din Iu-CS v d liu gi (ca mng chuyn ni gi) n SGSN (Serving GPRS Support Node) thng qua giao din Iu-PS. V l do gi thnh v tin li s dng, femtocell phi p ng tnh nng cm v chy (plug-and-play) ging nh cch m ngi ta ci t v s dng mt trm truy nhp WiFi. Trong tng lai, hng ngn femtocell s c ni kt vi kin trc mng li di ng thng qua mng cng cng Internet. iu ny t ra bi ton v kh nng m rng (scalability), tnh bo mt v s chun ha ca cc thit b v gii php. Di y, chng ta s cng tm hiu 4 gii php c ngh kt ni thit b femtocell n mng li di ng.

a) Kin trc da trn UMTS

Gii php u tin i theo hng gi nguyn h tng mng nm pha sau RNC. Vic lin lc t cc femtocell v mng li s thc hin bng ng hm IP c bo mt thng qua mng IP bng rng cng cng. Chng ta c th phn ra 2 loi: Iub trn IP (nu ng hm IP c thit lp gia femtocell v RNC) v Iu trn IP (nu ng hm c thit lp gia RNC v MSC/SGSN). Trong khung gii php ny, Iu-concentrator (cn c gi l Femtocell Aggregator hay Femtocell Gateway FGW) c ngh nh im tp trung lu lng thng tin t hng nghn femtocell trc khi i vo mng li di ng tng kh nng m rng (scalability). Gii php Iub trn IP Trong gii php ny, femtocell ng vai tr ca mt Node B, cn FGW s nm gia femtocell v RNC. Gii php ny thch hp khi c t ngi kt ni vi femtocell cng lc (v d trong gia nh hay vn phng t ngi). Ty theo s lng femtocell kt ni vi FGW m FGW v RNC c th thit k trong cng mt thit b hay 2 thit b ring l. y ta xt trng hp chng tch bit nhau v lin lc gia FGW v RNC thc hin trn giao din Iub. Gii php Iu trn IP Trong gii php ny, cc femtocell s c tch hp vi mng li di ng thng qua cc FGW nh minh ha hnh 3. Nhng chc nng ca RNC v Node B s c ci t trn femtocell v do femtocell s lin lc vi FGW thng qua giao din 3G Iu trn IP. S nhn din ca femtocell trong trng hp ny khi lin lc vi FGW c dng a ch ca mt RNC (12 bits). FGW to ng hm cho cc thng ip bo hiu RANAP t femtocell n mng li. Nu mng li khng h tr vn ti IP, FGW s m nhim vic chuyn i gia truyn ti IP v truyn ti ATM nh vo giao thc truyn ti bo tin SIGTRAN. b) Kin trc da trn gii php UMA/GAN Cng ngh UMA cho php thc hin cc dch v GSM /GPRS trn cc bng tn khng cp php (s dng cho Bluetooth v WiFi). UMA c 3GPP chun ha vi tn gi l cng ngh GAN (Generic Access Network). UMA/GAN ngh mt thc th mi gi l GANC (GAN controller), hay UNC (UMA Network Controller) thc hin cc chc nng ging nh mt b iu khin trm gc BSC trong GSM. GAN nh ngha mt giao din Up mi gia GANC v thit b di ng UE. c) Kin trc da trn IMS Gii php ny nhm kt ni femtocell trc tip vi mng li IMS (IP Multimedia Subsystem). Mt gii php thay th trong cng hng ny l dng softwitch trong cc femtocell c kt ni vi cc softwitch thng qua giao din SIP (Session Initiation Protocol). Vic kt ni trc tip vi IMS li mang li nhiu li ch nh: gim ti lu lng cho mng li di ng v lu lng t cc femtocell s khng phi i qua mng li, gim thi gian truyn ti v gim s nt mng m mt gi thng tin phi i qua. Cui cng, y mt gii php di hn cung cp dch v a phng tin ca IMS trong tng lai. Nh trnh by trn, r rng c nhiu cch tch hp hng nghn femtocells vi mng li di ng. Mi gii php c nhng im mnh v nhng im yu ring, c sc hp dn ring i vi tng nhm nh cung cp dch v. Trong mi trng hp, phn cng ca femtocell s khng thay i, ch c phn mm v giao din bo hiu m femtocell phi h tr l thay i. Do kh nng nng cp phn mm t xa femtocell l mt yu t cn thit. Vic tn ti nhiu gii php kin trc dn n yu cu v tng vn gia cc thit b, cc gii php. Nhng ngi trong cuc chy ua Th trng femtocell ang dn nng ln v hu nh nhiu cng ty sn xut thit b, nhiu nh cung cp mng cng khng mun b l phn bnh ca mnh. Danh sch ny ngy cng di ra. Nh sn xut thit b Netgear

v Nokia thng bo s phi hp cho ra i nhng b nh tuyn tt c trong mt tch hp femtocell v c Wi-Fi. Orange v Vodafone cng khng nh h gi RFP (request for proposal) t gia nm 2007 bit rng h vn ang thng mi loi hnh in thoi Unik. G khng l Google cng u t 25 triu la cho cng ty sn xut thit b Ubiquisys sn xut cc trm pht sng ti gia femtocell. V pha Motorola mi chun b gn nh hon tt. Nhng th nghim femtocell vi mng 3G vi nhiu nh cung cp mng Chu u cho nhng kt qu nh mong i. Motorola cng tin hnh th nghim vi Softbank Nht. Huawei cng th nghim femtocell vi Telefonica O2 Ty Ban Nha v Anh quc. Alcatel-Lucent k hp ng vi Sagem cng nhau sn xut v thng mi ha cc ng-ten femtocell. Erisson th cho bit h nhn c nhng n t hng v femtocell nhng l femtocell cho 2G. Bouygues Telecom (nh cung cp mng ca Php) chn gii php ca Nokia Siemens Networks ci tin vng ph sng GSM cho thu bao ca Bouygues bn trong cc to nh, trong cc cng ty, di tng hm v xung quanh cc trm pht sng Wi-Fi. Nhng th nghim ban u thnh cng v hin ti gii php ny sn sng trin khai. M, Sprint Nextel l ngi u tin thng mi ha femtocell. H trin khai femtocell cho ngi dng Denver v Indianapolis. Chc chn Sprint Nextel s tip tc m rng vic trin khai femtocell trong nm nay. Thit b femtocell ca h c cung cp bi Samsung, c bn vi gi 50 la cho khch hng. i vi ngi dng n l, h ch phi tr thm 15 la hng thng dng in thoi khng gii hn. Nu ngi dng femtocell cho quy m gia nh (2-5 ngi) th h phi tr 30 la/thng. Theo Idate, vic trin khai femtocell cho mng 3G UMTS trong nm 2008 s rt hn ch v cc chun cho gii php ny cha sn sng cng nh vic tch hp femtocell vo mng c nh s gp khng t kh khn. Do vy, theo h th th trng femtocell s ch c th khi sc 2009 hoc 2010. Cng theo Idate, nhng nh cung cp mng u tin trin khai femtocell Chu u s l Telefonica O2, T-Mobile v Vodafone. Nhng vng mc ca femtocell Tri ngc vi cho v b ngoi li cun, cng ngh femtocell vn n cha nhiu vn nghim trng cng nh nhiu him ha. Femtocell, theo nhiu chuyn gia, vn cha t c chn cng ngh, nht l cc vn v phn cp tn s, nhiu gy ra gia femtocell v macrocell hay cc femtocell ln cn. Nhiu giao thoa c th to ra cc vng cht (dead-spot). V femtocell s c lp t gn ging nh Wi-Fi nn nh cung cp hu nh khng th iu chnh v tr ca femtocell hn ch nhiu. Gii php cho cc thch thc ny cn phi c cc c ch d tn s v tuyn ng, t cu hnh nhanh li tn s ca femtocell trnh nhiu (ging nh gii php v tuyn nhn thc radio cognitive). Vn cht lng dch v khi tch hp vi mng c nh s khng tht d dng. Do nh cung cp dch v mng di ng femtocell khng nht thit s hu mng bng rng IP, nn vn QoS trn mng IP nm ngoi s qun l ca nh cung cp dch v. Thng tin thi gian thc t femtocell n mng li di ng s phi cnh tranh bng thng cng vi cc lu lng thng tin khc trn mng IP nh P2P. S hi t cht ch gia mng c nh v di ng l cn thit c th cung cp dch v cht lng cao. Hin ti vn cha c mt chun thng nht hay mt kin trc mng thng nht cho femtocell. iu ny cng s gy khng t kh khn cho vic trin khai chng rng khp. Ngoi cc vn k thut, vn lin quan n sc khe ngi tiu dng khi em cc trm pht sng vo tn trong nh hay vn phng cng cn phi c quan tm v xem xt mt cch cn thn. Mt khi cu tr li v cc vn ny cha r rng, ngi tiu dng s rt e ngi khi chp nhn cng ngh femtocell.