2. Mng t bonh ngha: Mng t bo l mt mng v tuyn phn tn trn cc khu vc a l c gi l cell (t bo), mi t bo c phc v bi t nht mt thit b thu pht c nh c gi l cell site hoc base station. Khi cc cell ny c c ni kt vi nhau, chng cung cp dch v v tuyn trn mt vng che ph a l rng.Cc thnh phn: MSC (Mobile Switching Center): Kt ni cc t bo vo mng din rng. Qun l vic thit lp cuc gi. X l vn di ng. Cell: Ph qua mt khu vc a l, cung cp dch v cho khu vc . BS ging vai tr 802.11 AP. Mobile user kt ni vi mng qua BS. Air-innterface: ng lin kt cc my truyn thng nhau.Cc thnh phn trong Cellular: Control channel (knh iu khin) dng chuyn giao cc thng tin iu khin chng hn nh thit lp v duy tr cuc gi. Traffic channels (knh lu thng) knh truyn d liu ting ni hay data.Nhng tng chnh ca mng cellular: C nhiu transmiter c mc nng lng thp. Mng chia thnh nhiu t bo: Tm ph ti a khi lp t. Mi cell c mt anten ca ring n. Mi cell c vng tn s ca ring n. c phc v bi mt trm c s ring. Cc cell ln cn th s dng tn s khc nhau trnh hin tng xuyn m.u im mng cellular: Tng cng kh nng ca mng. Gim mc s dng nng lng. Vng che ph ln hn. Gim mc sp vi cc tn hiu khc.Cc hnh dng t bo: Hnh vung:

Tt c khu vc c che ph tt nhng anten li khng c khong cch u nhau. Hnh trn:

Khong cch u nhng l ra l hng hoc chng lp nhau. Hnh lc gic:

Khong cch d=RKhng chng lp hay l hng. L do dng hnh lc gic: Tim cn n m hnh trn v c cung cp bi vng ph sng mt anten ng hng. C th sp xp cnh nhau m khng to ra cc vng chng lp hoc nhng khu vc khng c che ph. M hnh thit k cho php phn tch h thng d dng. Chuyn giao trn mng t bo- Hand over: chuyn giao: cc thit b c th di chuyn vo ra vng ph sng v i vo mt vng ph sng khc khi ang thc hin cuc gi.- Seamless: trong sut, ngi dng khng nhn ra.- Hn ch ti a chuyn giao khng cn thit.- Xc sut kha cuc gi mi trong t bo mi phi mc thp.-Phi chuyn n mt knh c SNR (Signal to Noise Ratio)tt hn ch cuc gi b drop.- Hand over: phn loi- chuyn giao cng: ph v trc khi thit lp: Mi khi thit b i vo mt Cell mi th phi c gn mt knh mi tip tc truyn thng. Cc knh mi s c gn trong qu trnh chuyn giao v MS phi ngt kt ni vi BS hin ti kt ni vo BS mi.- chuyn giao mm: thit b c th s dng t nhiu BS ng thi, MS thm knh mi t BS ch kt hp tn hiu t nhiu BS. Thit b truyn v nhn ng thi t nhiu BS. BS c NSR thp b loi. S dng CDMA.Cc bc thc hin chuyn giao: Khi to: hoc thit b, hoc h thng cn chuyn giao. Gi ti nguyn: cc ti nguyn cn thit chuyn giao s c xc nh trc. Thc hin chuyn giao v thit b chuyn sang s dng ti nguyn mi. Hon tt.Cc tham s quan trng: SNRout: xc nh t l SNR ca BS c. SNRnew: SNR ca knh mi. D=new-out. D : khng thi gian chuyn giao.4. Ti s dng tn s: Thit k gm hai bc: lp k hoch ph sng ph hp. phn b knh truyn. Cell, Cluster v ti s dng tn s: Cell: khu vc a l c cung cp bi 1 BS. Cluster: mt nhm Cell nm cnh nhau. Ti s dng tn s: s dng tn s radio truyn nhiu hn mt cuc hi thoi (Dng li tn s). Mt cch hiu qu ca vic qun l tn s v tuyn l do ti s dng cng mt tn s, trong khu vc dch v, cng nhiu cng tt. Ti s dng tn s ny l c th nh vo tnh cht truyn ca sng v tuyn CCI (Co-channel Interference): khng th s dng cng mt tn s trong cc Cell lin k. K hoch ti s dng tn s: Gn tn s cho cc Cell khc nhau. Cc Cell lin k c gn cc tn s khc nhau trnh b can thip hoc nhiu xuyn tm (crosstalk). i tng chnh ti s dng tn s l cc cell gn nhau (nhng khng lin k) m khng can thip ln nhau. Bin php gim CCI: Cell Splitting: chia nh cc Cell. Beam tilting: pht ra mt chm tia, gim mc nng lng n cell cnh nhau. Channel assignment: gn knh truyn. Sectored antenna. Dng anten nh hng.5. DSDV v CHGS routing: DSDV Mi node duy tr mt bng nh tuyn lu tr ng i n mi ch n c th c trong mng v s bc n ch. Mi mc trong bng c nh du bng mt s sequence number c gn bi node ch, sequence number cho php node phn bit gia ng i c v mi. Mt thng ip qung b ng i (route broadcast): a ch ng i. S bc cn i n ch. Sequence number ca thng tin nhn c ch l mt sequence number mi v duy nht ca mi thng ip broadcast. Quy trnh bo tr ng i: Nu c nhiu ng i n cng mt ch, ng i c sequence number gn nht s c s dng. Nu 2 thng tin cp nht c cng sequence number, ng i c s bc nh hn s c chn. gim thiu overhead, cc node c th tr hon vic gi thng tin cp nht trong mt khong thi gian nh trc. Sau khong thi gian ny c th c ng i tt hn c tm thy. DSDV s dng 2 loi gi tin cp nht: Full dump: Mang tt c thng tin nh tuyn v c th cn nhiu n v d liu giao thc mng (NPDU). Increamental packet: Ch mang nhng thng tin thay i t ln full dump gn nht. Gi tin dng ny ch trong phm vi mt NPDU. Quy trnh nh tuyn CHGS: B1: 1 gi tin c gi t 1 node, c chuyn n cluster hoead ca node . B2: T cluster head ny, gi tin c chuyn n node gateway ri n CH ca cluster ln cn. Vic tng t c lp li n khi gi tin n c CH node ch. B3: Gi tin c truyn n node ch. Mi mc lu tr 1 bng cluster table, lu tr CH ch ca mi node trong mng. CMT c gi qung b nh k gia cc node v dng gii thut DSDV. Mi node lu tr mt bng nh tuyn xc nh bc k tip n ch. Khi truyn mt gi tin, node s kim tra CMT v routing table theo xc nh: CH gn nht trn ng n ch. Bc tip theo n CH ny.6. ALOHA: Pure (P) ALOHA: Pht trin vo nhng nm 1970 cho mng d liu gi bi Hawaii University. Ch mt thit b u cui c d liu cn truyn th n truyn. Bn gi s xc nhn vic truyn thnh cng khng bng cch nghe thng ip t my nhn. Nu c ng , pha gi s gi li trong thi gian ch ngu nhin. Slotted (S) ALOHA: Ci tin: Thi gian chia thnh cc khung v 1 gi tin ch c th chuyn khi bt u khung. Gim ng .7. CSMA (Carrier Sense Multiple Access-a truy cp cm ng sng mang): Trc khi truyn mt terminal s cm nhn knh truyn xem c sng mang hay khng. Nu c sng mang, treminal ch mt thi gian truyn d liu v khng cm nhn li. Nu khng c sng mang, terminal bt u truyn. Detection delay l thi gian cn thit terminal cm nht knh truyn c ri hay khng. Propagation delay l khong cch cho mt packet i t BS n MS.Cc phin bn: CSMA/CD (CSMA vi d tm ng ) CSMA/CA (CSMA vi trnh ng ) CSMA/CA vi ACK CSMA/CA vi RTS/CTSCc kiu CSMA: p-persistent CSMA protocols (Ch i): B1: Nu ng truyn ri, truyn vi xc sut p. B2: Nu vic truyn b hon li trong mt khung thi gian, tip tc vi bc 1. B3: Nu ng truyn bn, tip tc lng nghe cho khi ng truyn ri, n bc 1. Nonpersistent CSMA (khng ch i): Bc 1: Nu ng truyn ri th truyn ngay lp tc. Bc 2: Nu ng truyn bn, ch mt thi gian ngu nhin ri quay li bc 1. 1-persistent CSMA protocol: Bc 1: Nu ng truyn ri th truyn ngay lp tc. Bc 2: Nu ng bn, tip tc lng nghe v ch n khi ri ri truyn.CSMA/CA: Nu trm c frame truyn th lng nghe Nu ng truyn ri th truyn Nhng nu bn th ch n khi ht bn mi truyn. Trong CSMA/CA tch hp: DIFS: khng gian DCF gia cc frame l mt khong thi gian xc nh mt knh ri bao lu trc khi c mt knh truyn. SIFS: khong thi gian ngn gia cc frame qui ch mt khong thi gian bao lu trc khi gi ACK hoc cc thng ip phn hi khc.CSMA/CA Basic: Trm tin hnh cm nhn ng truyn, nu ng truyn ri, n s ch ng truyn c ri hay khng trong thi gian DIFS, nu ng th truyn ngay lp tc. Nu ht thi im m ng truyn bn th trm s hon vic truyn v tip tc theo di ng truyn cho ti khi vic truyn hin ti kt thc. Nu ng truyn hin ti kt thc th trm s ch mt khong thi gian DIFS khc. Nu ng truyn tip tc ri trong thi gian ny th trm s ch mt khong thi gian random trnh ng v cm nhn ng truyn. Trong thi gian backoff, nu ng truyn bn th thi gian ny s tm ngng v tip tc nu ng truyn tr nn ri. Nu vic truyn khng thnh cng, vic ny xc nh bng vic khng c tn hiu ACK th coi nh c ng xy ra.Tnh tin cy: Dng ACK -> four-way handshake: Ngi gi gi i cc RTS (Ready-to-send) Ngi nhn tr li vi CTS (Clear-to-send) Ngi gi gi cc gi d liu. Ngi nhn p li bng gi ACK.