wifi và ứng dụng

8/10/2019 wifi v ng dng

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n t t nghi p L i m u

SVTH : Nguyn V c L p KTVT-50

L I M U

Mng my tnh t lu tr thnh mt thnh phn khng th thiu i v inhiu lnh vc i sng x hi, t cc h thng mng cc b dng chia s tinguyn c nhn chon h thng mng ton cu nh Internet. Cc h thng mnghu tuyn v v tuyn ang ngy cng pht trin v pht huy vai tr ca mnh. Tuynhin, c th k t ni Internet ng i s dng phi truy nh p Internet t mt v tr

c nh thng qua mt my tnh k t ni vo mng. iu ny i khi gy ra rt nhiukh khn cho nhng ng i s dng khi ang di chuyn hoc n mt ni khng ciu kin k t ni vo mng.

Mng khng dy l mt trong nhng b c tin l n nht ca ngnh cng ngh thng tin v truyn thng, mng khng dy to nn mt cuc cch mng trong victruy c p v truyn thng tin gia cc thit b u cui. Mng khng dy lm thay

i hon ton cuc sng ca con ng i, thi quen v k nng ca con ng i trongsinh hot, hc t p v cng vic c ci thin vi nng sut v hiu qu cao nht. Ngy nay mng khng dy ang tr nn ph bin trong cc t chc, doanh nghi pv c nhn. Chnh v s tin l i ca mng khng dy nn n dn thay th cho cc h thng mng c dy truyn thng hin ti. S ra i ca n khc phc nhng hn ch m mng ni dy khng th gii quyt c, v l gii php cho xu th pht trinca cng ngh truyn thng hin i.

Mng khng dy mang li l i ch r t to l n cho cng ngh thng tin vtruyn thng trong tt c cc lnh vc. Vi u im tin l i, linh hot v n gintrong qu trnh trin khai v s dng, mng khng dy ang p ng hu ht ccnhu cu trong cuc sng hin i. Cng ngh Wifi hay chun IEEE 802.11 l mttrong nhng cng ngh khngdy c ng dng r ng ri nht hin nay. S phttrin v ci tin khng ngng ca cng ngh Wifi nhm gii quyt nhng hn ch

ang tn ti nh tc , phm vi ph sng, an ton thng tin, tt c v mc ch


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n t t nghi p L i m u


nng cao cht l ng dch v cho ng i s dng. V i mong mun tm hiu nhngvn quan tm trn, em la chn ti Cng ngh Wifi vng dng, tigip em hiu r hn v nhng kin thc chuyn ngnh c hc v ng dngca n trong thc t cuc sng.

Mc ch ca ti:

Mc ch ca ti l tm hiu cng ngh Wifi, mt cng ngh khng dy ph bin nht hin nay. Ni dung chnh ca ti l trnh by qu trnh hot ngv ng dng trong thc t, t nh gi s pht trin trongtng lai ca cngngh Wifi.

i t ng v phm vi nghin c u:

i t ng nghin cu ca ti l cc vn lin quan n mng khng dyni chung v cng ngh Wifi ni ring. Cc kha cnh ca cng ngh Wifi cnghin cu l lch s ra i v pht trin, m hnh kin trc trin khai, nguyn lhot ng, u nhc im, ng dng v bo mt. Trong ni bt l nguyn l

hot ng vng dng trong cuc sng ca cng ngh Wifi. Phm vi nghin cu y l cc cng ngh mng khng dy, cc chun, cc hnh thc v thit b ngdng, cc k thut x l v truyn dn tn hiu v tuyn ca cng ngh Wifi.


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n t t nghi p M c l c


MC LCTrang

T BANHIM V THIT K TT NGHIP

L I M U

MC LC

DANH MC VIT TT

DANHMC HNH V

DANH MC BNG

CH NG 1. TNG QUAN V CNG NGH MNG KHNG DY ............. 1

1.1 Lch s pht trin cng ngh mng khng dy:........................................... 1

1.1.1 Lch s pht trin cng ngh mng khng dy: ......................................... 1

1.1.2 Gi i thiu cng ngh mng khng dy: ..................................................... 2

1.2 Phn loi v c im mng khng dy: ...................................................... 2

1.2.1 Phn loi mng khng dy: ........................................................................ 2

1.2.2 c im ca mng khng dy: ................................................................. 5

1.2.3 M hnh ca mng khng dy cc b WLAN: .......................................... 7

1.3 Nh ng cng ngh v giao th c s dng trong mng khng dy: ............. 10

1.3.1 Nhng cng ngh s dng trong mng khng dy: ................................ 10

1.3.2 Nhng giao thc s dng trong mng khng dy: .................................. 20

1.4 u i m v nh c i m ca mng khng dy:.......................................... 23

1.4.1 u im ca mng khng dy: ............................................................... 23

1.4.2 Nhc im ca mng khng dy: ......................................................... 24

1.4.3 So snh mng khng dy v mng c dy: ............................................. 25


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1.5 Mt s ng dng ca mng khng dy:...................................................... 26

1.5.1 Vai tr truy c p: ...................................................................................... 26

1.5.2 M r ng mng: ........................................................................................ 261.5.3 K t ni cc ta nh: ................................................................................. 26

1.5.4 Kh nng di ng: ................................................................................... 27

1.5.5 Hi thoi v truyn d liu: .................................................................... 28

CH NG 2. TNG QUAN V CNG NGH WIFI ........................................ 29

2.1 Khi nim, s ra i v pht trin ca Wifi:.............................................. 292.1.1 Khi nim cng ngh Wifi: ...................................................................... 29

2.1.2 S ra i v pht trin cng ngh Wifi: ................................................... 31

2.2 Cc tiu chun ca Wifi: .............................................................................. 33

2.2.1 Cc tiu chun ph bin ca Wifi: ........................................................... 33

2.2.2 Mt s tiu chun m r ng v ang pht trin ca Wifi: ........................ 38

2.3 u i m v nh c i m ca Wifi: ............................................................... 39

2.3.1u im ca cng ngh Wifi: .................................................................. 39

2.3.2 Nhc im ca cng ngh Wifi: ............................................................ 40

2.3.3. So snh Wifi v cc cng ngh khng dy khc: .................................... 40

2.4 Cc thit b c bn ca mng WLAN:........................................................ 41

2.4.1 im truy c p khng dy Wireless AP: ................................................... 41

2.4.2 B nh tuyn khng dy WR: ................................................................. 42

2.4.3 Thit b Wireless Router Modem: ............................................................ 43

2.4.4 Cu ni khng dy WB: ........................................................................... 44

2.4.5 B chuyn i khng dy v Card mng khng dy: .............................. 44


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CH NG 3. CC VN K THUT V NGUYN L HOT NGCA WIFI ................................................................................................................ 47

3.1 Kin trc ca cng ngh Wifi: ..................................................................... 473.1.1 Cc thnh phn kin trc: ......................................................................... 47

3.1.2 Kin trc cc l p trong m hnh OSI ca chun IEEE 802.11: ............... 51

3.2 K thut c bn trong Wifi:......................................................................... 56

3.2.1 K thut tr i ph: ..................................................................................... 56

3.2.2 K thut ghp knh phn chia tn s tr c giao OFDM: .......................... 61

3.2.3 K thut a truy nh p cmng sng mang chng va chm CSMA/CA: 64

3.3 Cch th c hot ng ca Wifi: .................................................................... 68

3.3.1 Hot ng ca mng wifi: ........................................................................ 68

3.3.2 Ty chn k t ni mt tr m v i mt hin hu: ...................................... 73

3.3.3 Chuyn vng: ........................................................................................... 76

3.3.4 Gi ng b: ............................................................................................ 76

3.3.5 Tit kim nng l ng: .............................................................................. 77

3.3.6 Phn on v t p h p: .............................................................................. 78

3.3.7 Gii thut quay li theo lut s m:......................................................... 79

3.3.8 Cc kiu khung ......................................................................................... 80

3.4 Cc ch tiu k thut ca mng WLAN:..................................................... 85

3.4.1 Phm vi ph sng: .................................................................................... 85

3.4.2 Lu l ng: ................................................................................................ 85

3.4.3 S ton vn v tin cy: ........................................................................ 85

3.4.4 Kh nng kt ni v i c s h tng mng ni dy: .................................. 86

3.4.5 Kh nng kt ni v i c s h tng mng khng dy: ............................. 86


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3.4.6 Nhiu : ...................................................................................................... 86

3.4.7 Tnh n gin v d dng trong s dng: ................................................ 87

3.4.8 Bo mt: ................................................................................................... 873.4.9 Chi ph: ..................................................................................................... 88

3.4.10 Tnh linh hot: ........................................................................................ 88

3.4.11 Tui th ngun pin cho cc sn phm di ng: ..................................... 88

3.4.12 An ton: .................................................................................................. 88

3.5 Bo mt trong Wifi: ...................................................................................... 893.5.1 C s bo mt mng Wifi: ....................................................................... 89

3.5.2 C ch bo mt WEP: .............................................................................. 93

3.5.3 C ch bo mt WPA: .............................................................................. 96

3.5.4 C ch bo mt WPA2: ............................................................................ 97

3.5.5 Tng quan v chun bo mt IEEE 802.11i: ........................................... 98

CH NG 4. NG DNG V S PHT TRIN TRONG T NG LAI CAWIFI .......................................................................................................................100

4.1 ng dng ca cng ngh Wifi:...................................................................100

4.1.1 Truy c p mng cng cng: .....................................................................100

4.1.2 K t ni v truyn ti d liu:..................................................................101

4.1.3 Thit l p mng gii tr gia nh:.............................................................1034.1.4 T ng ha ngi nh: ...........................................................................104

4.1.5 Gii php vn phng di ng: ................................................................105

4.1.6 Gii php Wifi chuyn dng: .................................................................106

4.2 Cng ngh Wifi ti Vit Nam: ....................................................................108

4.2.1 S pht trin ca cng ngh Wifi ti Vit Nam: ....................................108


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4.2.2 Mt s d n Wifi ti Vit Nam: ...........................................................110

4.3 Mt s thit b s dng cng ngh Wifi: ...................................................115

4.3.1 My tnh xch tay v my tnh bng: .....................................................1154.3.2 in thoi di ng: .................................................................................117

4.3.3 Cc thit b dn dng: ............................................................................119

4.4 S pht trin trong t ng lai ca cng ngh Wifi: ..................................120

4.4.1 C hi ca cng ngh Wifi: ...................................................................120

4.4.2 Thch thc ca cng ngh Wifi: ............................................................1224.4.3 S pht trin trong t ng lai ca cng ngh Wifi: .................................123

K T LUN

L I CM N

TI LIU THAM KHO


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n t t nghi p Danh m c vi t t t


DANH MC VIT TT

T vit tt Ting Anh Ting Vit ADSL Asymmetric Digital Subscriber

Lineng dy thu bao s bt ixng

AES Advanced Encryption Standard Tiu chun m ha tin tin AMPS Advanced Mobile Phone System H thng in thoi di ng

nng cao nm 1977 AP Access Point im truycp

ASM Automatic Storage Management Qun l lu tr t ng ATM Asynchronous Transfer Mode Ch truyn dn khng ng

bBAP Battery Assisted Passive Pin h tr th ng BSS Basic Service Sets Tp dch v c bn

M hnh mng c s BPSK Binary Phase Shift Keying Kha dch pha nh phn CCMP Counter Cipher Mode Protocol Giao thc m ha d liu CDMA Code Division Multiple Access a truy nhp phn chia theo

m

DES Data Encryption Standard Tiu chun m ha d liu DLNA Digital Living Network Alliance Cng ngh giao tip khng dy

gia nh

DS Distribution System H thng phn phi DSL Digital Subscriber Line ng dy thu bao s DSSS Direct Sequence Spread SpectrumTri ph chui trc tip ESS Extended Service Sets Tp dch v m rng

M hnh mng m rng ETSI European Telecommunications

Standards InstituteVin Tiu chun Vin thngChu u

FCC Federal Communications y ban truyn thng


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Commission Lin bang Hoa K FHSS Frequency Hopping Spread

SpectrumTri ph nhy tn

FSK Frequency Shift Keying Kha dch tn s FSO Free Space Optics Truyn thng quang v tuyn FTP File Transfer Protocol Giao thc truyn tp tin FTS File Transfer Service Dch v truyn tp tin GPRS General Packet Radio Service Dch v v tuyn gi tng hp GPS Global Positioning System H thng nh v ton cu

GSM Global System for MobileCommunications

H thng thng tin di ngton cu

HDMI High Definition MultimediaInterface

Giao tip a phng tin tincy cao

HTTP Hyper Text Transfer Protocol Giao thc truyn ti siu vn bn

IBSS Independent Basic Service Sets Tp dch v c bn c lp M hnh mng c lp

IEEE Institute of Electrical andElectronic Engineers

Vin K s in v in t

IMTS Improved Mobile TelephoneService

Dch v in thoi di ng citin nm 1964

IP Internet Protocol Giao thc Internet

ISM Industrial, Scientific, Medical Bng tndnh cho cngnghip, khoa hc v y hc

ISO International Socialist OrganizationT chc tiu chun ha quc t ISP Internet Service Provider Nh cung cp dch v Internet LAN Local Area Network Mng cc b MIMO Multi Input Multi Output a u vo- a u ra MAC Media Access Control iu khin truy nhpmi

trng


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NFC Near Field Communication Cng ngh giao tip khongcch gn

NIC Network Interface Card Card giao din mng NOS Network Operation System H thng iu hnh mng OBEX OBject EXchange Giao thc trao i d liu dng

hng ngoi OFDM Orthogonal Frequency Division

MultiplexingGhp knh phn chia tn strc giao

PC Persional Computer My tnh c nhn

PDA Personal Digital Assistant Thit b k thut s h tr cnhn

PMD Physical Media Dependent Phn lp ph thuc mi trngvt l

PSK Phase Shift Keying Kha dch pha QAM Quadrature Amplitude Modulationiu ch bin cu phng QoS Quality of Service Cht lng dch v QPSK Quadrature Phase Shift Keying Kho dch pha cu phng RF Radio Frequency Tn s v tuyn RFID Radio Frequency

IdentificationCng ngh Nhn dang tn sv tuyn

SSID Service Set Identifier B nhn dng dch v TKIP Temporal Key Integrity Protocol Giao thc ton vn kha thi

gianUHF Ultra High Frequency Di tn s cc cao UMTS Universal Mobile

Telecommunications SystemH thng vin thng di ngton cu

USB Universal Serial Bus Chun gia UWB Ultra Wide Band Cng ngh siu bng rng VHF Very High Frequency Di tn s rt cao VPN Virtual Private Network Mng ring o


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VLAN Virtual Local Area Network Mng cc b o

WAP Wireless Application Protocol Giao thc ng dng khng dy

WEP Wired Equivalent Privacy Bo mt tng ng mng idy

WLAN Wireless Local Area Network Mngv tuyn cc b

WMAN Wireless Metropolitan Area Network

Mng v tuyn th

WPA Wi-Fi Protected Access Bo v truy cp Wi-Fi

WPAN Wireless Personal Area Network Mng v tuyn c nhn WRAN Wireless Regional Area Network Mng v tuyn khu vc WWAN Wireless Wide Area Network Mng v tuyn din rng WWW World Wide Web H thng lin kt d liu ton

cu


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n t t nghi p Danh m c hnh v


DANH MC HNH V

Hnh 1.1 Phn lo i mng khng dy ........................................................................... 3

Hnh 1.2 M hnh m ng Ad-hoc .................................................................................. 7

Hnh 1.3 M hnh m ng Infrastructure ....................................................................... 8

Hnh 1.4 M hnh m ng m r ng ................................................................................ 9

Hnh 1.5 Phin b n m i nh t Bluetooth 4.0 .............................................................. 11

Hnh 1.6 Thi t b ng d ng cng ngh Bluetooth ..................................................... 12

Hnh 1.7 ng d ng ca RFID ................................................................................... 13

Hnh 1.8 ng d ng ca cng ngh NFC ................................................................... 15

Hnh 1.9 M hnh cng ngh WiMAX ....................................................................... 17

Hnh 2.1 Bi u t ng cng ngh Wifi ......................................................................... 29

Hnh 2.2 T c v kho ng cch truy n d liu ca Wifi ......................................... 38

Hnh 2.3 Access Point chu n N ................................................................................. 41

Hnh 2.4 Wireless Router Linksys chu n N ............................................................... 42

Hnh 2.5 Wireless Router Modem Linksys chu n N .................................................. 43

Hnh 2.6 Wireless Bridge Linksys ............................................................................. 44

Hnh 2.7 PC Card c a Asus v Planet ...................................................................... 45 Hnh 2.8 Adapter Card TP-Link ................................................................................ 45

Hnh 2.9 Wireless USB Card TP-Link ...................................................................... 46

Hnh 3.1 Cc thnh ph n ki n trc c a Wifi ............................................................. 47

Hnh 3.2 M hnh DS v ESS .................................................................................... 49

Hnh 3.3 V tr c a 802.11 trong m hnh OSI .......................................................... 51


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Hnh 3.4 L p vt l ca 802.11 ................................................................................. 53

Hnh 3.5 M hnh phn l p MAC .............................................................................. 54

Hnh 3.6 L p MAC ca 802.11 ................................................................................. 56

Hnh 3.7 S kh i h th ng tr i ph nh y t n ....................................................... 58

Hnh 3.8 V d v tr i ph nh y t n .......................................................................... 59

Hnh 3.9 S kh i h thng tr i ph chu i tr c ti p ............................................. 60

Hnh 3.10 Nguyn l tr i ph chu i tr c ti p ........................................................... 61

Hnh 3.11 So sng k thut sng mang khng ch ng ph (a) v sng mang ch ng ph (b) ....................................................................................................................... 63

Hnh 3.12 S kh i h th ng OFDM ..................................................................... 64

Hnh 3.13 C ch hot ng ca CSMA/CA ............................................................. 66

Hnh 3.14 Qu trnh trao i y ca cm ng sng mang o ........................... 67

Hnh 3.15 S phn b knh trong d i t n s 2.4GHz .......................................... 69

Hnh 3.16 S phn b knh trong d i t n s 5GHz ............................................. 70

Hnh 3.17 Ch qut th ng ............................................................................... 74

Hnh 3.18 Ch qut ch ng ............................................................................... 74

Hnh 3.19 Phn on khung ...................................................................................... 79

Hnh 3.20 Khun d ng khung chu n IEEE 802.11 ................................................... 80

Hnh 3.21 Khun d ng khung MAC .......................................................................... 81

Hnh 3.22 Tr ng i u khi n khung c a l p MAC ................................................... 81

Hnh 3.23 Khung nh d ng RTS .............................................................................. 83

Hnh 3.24 Khun nh d ng CTS .............................................................................. 84

Hnh 3.25 Khun d ng khung ACK .......................................................................... 84

Hnh 3.26 Cc m c bo v mng ......................................................................... 90


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Hnh 3.27 Chng thc h thng m.......................................................................... 92

Hnh 3.28 Ch ng th c kha chia s .......................................................................... 93

Hnh 3.29 Quy trnh m ha WEP s d ng RC4 ...................................................... 94

Hnh 3.30 Thnh ph n ca IEEE 802.11i ................................................................. 98

Hnh 4.1 ng d ng truy c p mng cng c ng ........................................................101

Hnh 4.2 M hnh k t ni Wifi trong gia nh.........................................................102

Hnh 4.3 M hnh k t n i ca WiFi Direct .............................................................103

Hnh 4.4 ng d ng gi i tr gia nh.......................................................................104

Hnh 4.5 Gi i php vn phng di ng ...................................................................105

Hnh 4.6 M hnh gi i php Wifi tr ng hc ..........................................................106

Hnh 4.7 M hnh cng ngh Hybrid Wicell ...........................................................108

Hnh 4.8 My tnh xch tay Osborne 1 ...................................................................115

Hnh 4.9 My tnh xch tay v my tnh b ng ........................................................116

Hnh 4.10 S pht tri n ca in tho i di ng ......................................................118

Hnh 4.11 Smartphone c a Samsung, HTC v Apple .............................................118

Hnh 4.12 My in Canon tch h p Wifi ...................................................................119

Hnh 4.13 My nh v my quay tch h p Wifi .......................................................120

Hnh 4.14 Camera quan st khng dy ...................................................................120

Hnh 4.15 Bng thng 160MHz trong tn s 5GHz ................................................125

Hnh 4.16 So snh cch pht d liu gi a Wifi hi n nay v 802.11ac ...................126


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n t t nghi p Danh m c b ng


DANH MC BNG

Bng 1. So snh m ng khng dy v m ng c dy ................................................... 25

Bng 2.1 Cc l a ch n ca chu n 802.11b .............................................................. 35

Bng 2.2 Cc tiu chu n ph bi n ca IEEE 802.11 ................................................ 38

Bng 2.3 So snh Wifi v cc cng ngh khng dy khc ........................................ 40


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1 n t t nghi p Chng 1


CH NG 1 . TNG QUAN V CNG NGH

MNG KHNG DY

1.1 Lch s pht trin cng ngh mng khng dy:

1.1.1 Lch s pht trin cng ngh mng khng dy:

Nh khoa hc Guglielmo Marconi sng l p ra mng khng dy. Nm 1894, Marconi bt u cc cuc th nghim v nm 1895 ng thnh cng

khi gi cc tn hiu v tuyn qua khong cch 2,5km. Nm 1899 ng thit l p c h thng truyn thng v tuyn qua bin Mngs (Manche) ni Anh vPhp. Thnh tu chuyn tin bng tn hiu ny nh du mt tin b l n v ldu hiu cho s ra i mt h thng cc gi tr mang tnh thc tin cao.

Nm 1901 ng lp c mt k tch l pht tn hiu m Moox (morse) quai Ty Dng t Anh qua Canada chng minh r ng sng v tuyn khng

b nh h ng b i b cong tri t m ra trin vng thit l p h thng v tuynin ton cu. Cng ngh khng dy m Marconi pht trin l mt s pha t pgia in bo c dy truyn thng v sng Hertz.

Trong chin tranh th gi i I, ln u tin n c s dng cuc chin Boernm 1899, v nm 1912, mt thit b v tuyn c s dng trong con tuTitanic.

Tr c thp nin 1920, in bo v tuyn tr thnh mt phng tin truyn

thng hu hiu b i n cho php gi cc tin nhn c nhn bng qua cc lc a.Cng v i s ra i ca radio (my pht thanh), cng ngh khng dy c th tn ti mt cch thng mi ha. Nm 1927, dch v in thoi v tuyn cthng mi ha v hot ng gia 2 n c Britain v US (United States).

Vo u th p nin 1970, IMTS (Improved Mobile Telephone System) phttrin thu pht d liu ng thi, tng s l ng knh truyn v cng sut l nhn.


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Nm 1977, AMPS (Advanced Mobile Phone System) c pht minh b i BellLabs, hot ng u tin US v i nhng vng a l c phn chia thnh

nhng t bo. Th p nin 1980, cng ngh v tuyn l nhng tn hiu tng t. Th p nin

1990, chuyn sang tn hiu s ngy cng c cht l ng tt hn, nhanh chngv hiu qu cao hn.

1.1.2 Gi i thiu cng ngh mng khng dy:

Mng khng dy (Wireless Network) l mng s dng cng ngh cho php hai

hay nhiu thit b k t ni v i nhau bng cch s dng mt giao thc chun mkhng cn nhng k t ni bng dy mng. Mng khng dy (mng v tuyn )l mt mng d liu linh hot c thc hin nh mt s m r ng hoc mt s la chn m i cho mng my tnh c dy (mng hu tuyn).

Mng my tnh khng dy s dng cc sng in t khng gian (sng vtuyn hoc sng nh sng) thu, pht d liu qua khng kh, gim thiu nhu cuv k t ni bng dy. V vy, cc mng my tnh khng dy k t h p lin k t d liu vi tnh di ng ca ng i s dng.

Mng khng dy thc s ang thay th cho mng my tnh c dy, cung c pkh nng x l linh ng hn v t do hn chott c cc lnh vc trong cucsng. Ng i dng c th truy c p thng tin t mng, chia s v trao i d liuv i nhau t bt c a im no trong vng ph sng ca mng m khng b rng buc b i cc k t ni vt l.

1.2 Phn loi v c im mng khng dy:1.2.1 Phn loi mng khng dy:

i v i h thng mng khng dy, chng ta cng c s phn loi theo quym v phm vi trin khai tng t nh h thng mng c dy: WPAN (WirelessPersonal Area Network), WLAN (Wireless Local Area Network), WMAN(Wireless Metropolitan Area Network), WWAN (Wireless Wide Area Network),

WRAN (Wireless Regional Area Network). Ngoi ra, mng khng dy cn c


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phn loi theo phng thc truyn thng tin, bao gm truyn thng tin bng sngv tuyn v bng tn hiu hng ngoi.

WWAN

< 15kmGSM, CDMA, 3G UMTS

WRAN

< 100km802.22

WMAN

< 5kmWiMAX

WLAN

< 150mWifi, HiperLAN

WPAN


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WLAN (Wireless Local Area Network): mng v tuyn cc b, c kh nngk t ni phm vi r ng hn v i nhiu vng ph sng khc nhau, do cc thit

b di ng c th t do di chuyn gia cc vng v i nhau. WLAN l mt phnca gii php vn phng di ng, cho php ng i s dng k t ni mng cc b ti cc khu vc cng cng nh vn phng, khch sn, sn bay, tr ng hc, bnh vin. Phm vi hot ng t 100m n 500m v i tc truyn d liutrong khong 11Mbps - 54Mbps. Cng ngh ni bt nht trong nhm ny lWifi v i tiu chun IEEE 802.11. Bn cnh WiFi th cn mt chun khc lHiperLAN v HiperLAN2, i th cnh tranh ca Wifi c chun ha b iVin Tiu chun Vin thng chu u ETSI (European TelecommunicationsStandards Institute).

WMAN (Wireless Metropolitan Area Network): mng v tuyn th, s dng tiu chun IEEE 802.16. Vic a ra chun ny m ra mt cng ngh m i truy nh p khngdy bng rng WiMAX (Worldwide Interoperability forMicrowave Access) cho giao ti p dnh cho h thng truy cp khng dy bng

r ng c nh v i mc tiu cung c p nhng tr c k t ni tr c ti p trong mng th t bng thng tng ng cp, ng dy thu bao s DSL (DigitalSubscriber Line), tr c T1 ph bin hin nay. Cng ngh WiMAX c kh nng ph sng r ng hn, bao ph c mt khu vc thnh th hay mt khu vc nngthn nht nh. Cng ngh ny c th cung c p v i tc truyn d liu n75Mbps ti mi tr m pht sng v i tm ph sng t 2kmn 10km. Ngoi rac chun IEEE 802.20, c gi l truy nh p v tuyn bng rng di ng

WBMA (Mobile Broadband Wireless Access). N c th h tr ngay c khiang di chuyn v i vn tc ln t i 250km/h. Trong khi chuyn vng caWiMAX nhn chung b gi i hn trong mt phm vi nht nh, th chun IEEE802.20 ging nhcng ngh 3G (Third Generation Technology) c kh nngh tr chuyn vng ton cu. Trong mng IEEE 802.20, vic ng b gia ng ln v ng xung u c thc hin hiu qu.


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Cc k t ni khng dy c thit l p bng sng in t. Ty theo mc chhot ng m cc dng k t ni khc nhau s s dng cc di tn s khc nhau,

ng th i cc thit b s dng k t ni s giao ti p theo cc phngthckhc nhau.

Trong phn ln tr ng h p, d liu c truyn i do cc thit b tham giamng khng dy pht sng ra mi h ng xung quanh (qung b) ch khngc nh h ng bng dy dn. Cng ng ngha v i vic nhng thit b khng phi ca ng i nhn cng c th ti p cn cc sng c cha d liu ca bn, nhng nh vo cc phng php nh danh v bo mt ca tng giao thcmng nn th ng th ch ng i nhn m i c th m d liu bn gi i.

Cc sng v tuyn thng c xem nh cc sng mang v tuyn do chngch thc hin chc nng cung cp nng l ng cho mt my thu xa. D liukhi phti c iu ch trn sng mang v tuyn sao cho c th c khi phc chnh xc ti my thu.

Nhiu sng mang v tuyn c th tn ti trong cng khng gian, ti cng th i

im m khng can nhiu ln nhau nu cc sng v tuyn c pht trn cctn s v tuyn khc nhau. nhn li d liu, my thu v tuyn s thu trntn s v tuyn xc nh trong khi s loi b cc tn s v tuyn khc.

Trong mng khng dy tiu chun, mt thit b thu v pht c gi l mtim truy c p, ni v i mng hu tuyn ti mt v tr c nh s dng cpEthernet tiu chun. Chc nng ca im truy c p l thu,lu vo b nh m,v pht d liu gia mng khng dy v cs h tng mng hu tuyn. Mt

im truy cp n h tr mt nhm nh ng i s dng v thc hin chc nngtrong mt phm vi nht nh. im truy c p c t bt k v tr no minl nm trong vng ph sng mong mun.

Ng i s dng truy c p vo mng khng dy thng qua cc b thchng mytnh khng dy c tch h p trong cc thit b u cui nh my vi tnh, inthoi di ng v cc thit b c nhn khc. Cc b thchng my tnh khngdy cung c p mt giao din gia h thng iu hnh mng NOS (Network


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Operation System) ca my khch (Client) v cc sng khng gian qua mtanten.

Cng ngh khng dy bao gm cc thit b v h thng phc tp nh h thngWLAN, in thoi di ng (Mobile Phone) cho n cc thit b n gin nhtay nghe khng dy, microphone khng dy v nhiu thit b khc c kh nngtruyn nhn v lu tr thng tin t mng. Ngoi ra cng bao gm c nhngthit b h tr hng ngoi nhthit b iu khin t xa (Remote Control), inthoi truyn d liu tr c din gia 2 thit b.

1.2.3 M hnh ca mng khng dy cc b WLAN: M hnh mng c l p IBSS (Independent Basic Service Sets):

- M hnh ny cn c gi l m hnh mng Ad-hoc, l mng gm hai haynhiu my tnh c trang b card khng dy m khng dng n cc thit b nh tuyn hay thu pht khng dy.- Cc my tnh c vai tr ngang nhau, cc thit b tham gia mng khng dyAd-hoc ngoi vic giao ti p vi nhau cn m nhim lun c vic chuyn ti p

d liu cho cc thit b khc trong mng.

Ng i dng A

Ng i dng B Ng i dng C

Hnh 1.2 M hnh m ng Ad-hoc


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- Mng Ad-hoc hot ng ch khi cc my tnh ca n nm gn v i nhau v phng din vt l v ch khi gi i hn v con s. Hn na, truy c p v chia

s Internet, mt trong cc my tnh vn phi c k t ni v i mng Internetthng qua cp hoc k t ni khng dy khc.

M hnh mng c s h tng BSSs (Basic Service Sets):- M hnh ny cn gi l m hnh mng Infrastructure, l mng gm mt haynhiu im truy c p AP (Access Point) m r ng phm vi hot ng ca ccTr m (Station) c th k t ni v i nhau v i mt phm vi gp i, nhiu imtruy c p AP lin k t mng khng dy v i mng ni dy v cho php cc ng idng chia s cc ti nguyn mng mt cch hiu qu.- AP ng vai tr l im truy c p cho cc client trao i d liuv i nhau vtruy xut ti nguyn ca my ch (Server). Mi AP c th lm im truy c pcho 10-15 client ng th i ti mt thi im ty sn phm v hng sn xut.

Ng i dng A

Ng i dng B Ng i dng C

Hnh 1.3 M hnh m ng Infrastructure


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M hnh mng m r ng ESSs (Extended Service Sets):- Mng 802.11 m r ng phm vi di ng t i mt phm vi bt k thng qua

ESS. Mt ESSs l mt t p hp cc BSSs ni m cc AP giao ti p v i nhau chuyn lu l ng t mt BSS ny n mt BSS khc lm cho vic dichuyn d dng ca cc tr m gia cc BSS, AP thc hin vic giao ti pthng qua h thng phn phi DS (Distribution System).- H thng phn phi l mt l p mng trong mi AP m n xc nh chn cho mt lu lng c nhn t mt BSS. H thng phn phi c

ti p sng tr li mt ch trong cng mt BSS, chuyn ti p trn h thng phn phi t i mt AP khc, hoc g t i mt mng c dy ti ch khngnm trong ESS. Cc thng tin nhn b i AP t h thng phn phi ctruyn t i BSS s c nhn b i tr m ch.

Ng i dng A

Ng i dng B

Ng i dng C

Access Point 1

Ng i dng D

Access Point 2

Wired Network (DS)

Hnh 1.4 M hnh m ng m r ng


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1.3 Nh ng cng ngh v giao th c s dng trong mng khng dy:

1.3.1 Nhng cng ngh s dng trong mng khng dy:

Cng ngh Bluetooth:- Bluetooth l chun 802.15.1 mng WPAN, chun k t ni khng dy tmngn, thit k cho cc k t ni thit b c nhn hay mng cc b nh, trong phm vi bng tn chung ISM (Industrial, Scientific, Medical) 2.4 - 2.485 GHz. Nm 1994, hng Ericsson xut vic nghin cu v pht trin giao din vtuyn cng sut nh, chi ph th p, s dng sng v tuyn k t ni khng dy

gia cc thit b di ng v i nhau v cc thit b in t khc, t chc SIG(Special Interest Group) chnh thc gi i thiu phin bn 1.0 ca Bluetoothvo thng 7 nm 1999. - Bluetooth h tr tc truyn ti d liu ln t i 720Kbps trong phm vi 10mn 100m v c th t c tc truyn d liu 1Mbps. Bluetooth s dng phng php tri ph nhy tn FHSS (Frequency Hopping Spread Spectrum), c thit k hot ng trn 79 tn s khc nhau, n th ng thc hin 1600 b c nhy trong mt giy, khi AFH (Adaptive FrequencyHopping) c kchhot. Mt thit b Bluetooth tng th c th giao ti p v i ti a l 7 thit b trong mt Piconet (mt mng Ad-hoc s dng cng ngh Bluetooth).- V tm ph sng, bluetooth c 3 l p (class): class 1 c cng sut 100mW v itm ph sng gn 100m; class 2 c cng sut 2,5mW, tm ph sng khong10m; v class 3 l 1mW v i tm ph sng khong 5m. Bluetooth c nhiu

giao thc hot ng khc nhau. A2DP (Advanced Audio Distribution Profile)l c ch truyn dn m thanh stereo qua sng bluetooth t i cc tai nghe, loa;FTP (File Tr ansfer Protocol) l c ch chuyn i d liu qua k t ni bluetooth gia cc thit b FTS (File Transfer Services); hay OBEX (OBjectEXchange), c pht trin b i chnh nh mng Verizon, cho php xa d liuthng qua bluetooth.- Bluetooth tri qua khong 7 phin bn chnh. Ngoi phin bn 2.1 l

phin bn u tin h tr k t ni nhiu thit b cng lc, hin nay trn th


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tr ng ch yu tn ti cc bin th ca hai phin bn m i nht l 3.0 v 4.0.Bluetooth 3.1 hay Bluetooth 3.0 + HS (High Speed) c gi i thiu vo nm

2009 cho php truyn ti d liu v i tc ln t i 24Mbps. Ngy 30/6/2010,Bluetooth SIG a ra Bluetooth phin bn 4.0 l s k t h p ca classicBluetooth (Bluetooth 2.1 v 3.0), Bluetooth high speed (Bluetooth 3.0+HS) v Bluetooth low energy (Bluetooth Smart Ready/Bluetooth Smart).

Hnh 1.5 Phin b n m i nh t Bluetooth 4.0- Ccng dng ni bt ca Bluetooth gm:

iu khin v giao ti p khng giy gia mt in thoi di ng v tainghe khng dy.

Giao ti p khng dy v i cc thit b vo ra ca my tnh, chng hn nhchut, bn phm v my in.

Thay th cc giao ti p ni ti p dng dy truyn thng gia cc thit b o,thit b nh v dng h thng nh v ton cu GPS (Global PositioningSystem), thit b y t, my qut m vch, v cc thit b iu khin giaothng.

iu khin t xa cho cc thit b tr chi in t nh Wii- My chi trchi in t th h 7 ca Nintendo v PlayStation 3 ca Sony.

K t ni Internet cho PC hoc PDA (Personal Digital Assistant) bng cch

dng in thoi di ng thay modem.


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Hnh 1.6 Thi t b ng d ng cng ngh Bluetooth

Cng ngh nhn dng tn s v tuyn RFID (Radio Frequency Identification):- RFID l cng ngh xc nhn d liu i t ng bng sng v tuyn nhndng, theo di v lu thng tin trong mt th (Tag). K thut RFID s dngtruyn thng khng dy truyn d liu t cc th n cc b c (Reader).

Reader qut d liu th v gi thng tin n c s d liu lu tr trn my tnhhoc h thng qun l.- RFID hot ng trn nguyn tc: D liu c cha trong Chip nh (Tag/MDS), d liu ny c truyn thng v i PC/PLC (Programmable LogicController) thng qua cc module bao gm, module reader v adapter moduleASM (Access Switching Module)). Chip nh v module reader cng c ch to v i nhiu chng loi khc nhau ph h p v i yu cu s dng.- Th RFID c th c gn lin v i mt i t ng v s dng theo di vqun l i tng xc nh. Th RFID d dng c che giu hoc k t h ptrong cc mt hng khc. RFID l i th hn cc h thng bng tay hoc s dng m vch. Th c th c c nu c thng qua gn b c, ngay c khi n c bao ph bi cc i t ng khc hoc khng nhn thy c.- H thng RFIDth ng c ba cu hnh: cu hnh PRAT (Passive Reader

Active Tag), h thng m c b c th ng m ch nhn c tn hiu v


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tuyn t th ang hot ng, phm vi ti p nhn ca PRAT c th ln n 60m,do cho php s linh hot trong ccng dng nh bo v v gim st ti

sn. Cu hnh ARPT (Active Reader Passive Tag) cu c hot ng ch ng, trong truyn tn hiu thm vn v nhn c tr l i xc thc t ccth th ng. Cu hnh ARAT (Active Reader Active Tag)trong th anghot ng c kch hot v i mt tn hiu thm vn t b c hot ng. Mt bin th ca h thng ny l s dng pin h tr th ng BAP (BatteryAssisted Passive).- Khong cch c ph thuc vo mt s thng s v iu kin c th, tythuc vo th l Active hay Passive Tag. Phn l n th RFID Passive ckhong cch c < 1m, ty thuc vo di tn s ca u c. H thng RFIDs dng di tn UHF s c khong cch c ln hn, c th ln t i 100m ph thuc vo tng ng dng c th. Th RFID c th c trong khong th i gian< 10ms.

Hnh 1.7 ng d ng ca RFID

Th RFID Thit b c th H tng Tch h p

My ch


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Cng ngh giao ti p khong cch gn NFC (Near Field Communications):

- NFC l cng ngh k t ni khng dy phm vi tm ngn trong khong cch lthuyt l 10cm nhng thc t ch 4cm, s dng cm ng t trng thchin k t ni gia cc thit b khi c s ti p xc tr c tip hay gn nhau. NFC c ph chun ISO/IEC (International Organization forStandardization/International Electrotechnical Commission) vo cui nm2003. Cng ngh NFC ra i t s k t h p cng ngh nhn dng khng ti pxc v nhng cng ngh k t ni truy c p m i

- NFC hot ng di bng tn 13,56MHz nn khngnh hng n cccng ngh k t ni khng dy khc. Khi mng NFC c kch hot, ng idng vn c th s dng cc cng ngh k t ni khc nh Bluetooth, Wi-Fi numun k t ni tm xa hn hay khi cn truyn l ng d liu ln hn.

- NFC c tc truyn ti d liu trong khong 106Kbps n 848Kbps. Dokhong cch truyn d liu kh ngn nn giao dch qua cng ngh NFC cxem l an ton. NFC m ra mt xu hng trao i d liu theo dng mngngang hng (P2P). Loi hnh NFC ang c ng dng hin nay l th nhndng NFC (NFC tag). Th nhn dng NFC c vai tr tng t m vch hay mQR (Quick Response). Th NFC th ng cha d liu ch c nhng cng cth ghi c. NFC c 4 nh dng th da trn cc chun ISO 14443 TypeA, 14443 Type B v ISO 18092.

- Cng ngh NFC c 2 ch truyn d liu: ch ng (active) v th ng(passive). Trong ch th ng: thit b ngun pht s pht ra t trng nngun ch, ngun ch tr ng thi b ng v ch tr l i khi nhn tn hiu t ngun pht. Trong ch ch ng: c thit b ngun pht v thit b chtruyn d liu bng cch to ra t tr ng ring.

- Mt giao dch din ra trn NFC tun t theo cc b c: pht hin (Discovery),xc thc (Authentication), trao i (Negotiation), truyn d liu (Transfer) v

xc nhn t pha nhn d liu (Acknowledgment). Trong tr ng h p mun


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tng c ng tnh bo mt trong lc giao dch, cng ngh NFC c thm 2 chunm ha: chun m ha tin tin AES (Advanced Encryption Standard) v

chun m ha d liu Triple DES (Data Encryption Standard).

Hnh 1.88 ng d ng ca cng ngh NFC

Cng ngh WiMAX (Worldwide Interoperability for Microwave Access):

- WiMAX l l mt cng ngh khng dy bng thng rng c thit k davo tiu chun IEEE 802.16. Tiu chun IEEE 802.16-2001 ban hnh vothng 4nm 2002,giao din khng gian cho h thng truy nhp bng rng c nh hot ng di tn hot ng l 10-66GHz v tha mn tm nhn thng

LOS (Line Of Sight) v i bn knh cell t 2 - 5km. IEEE 802.16-2001 c tc trong khong 32 - 134Mbps v i knh 28MHz, s dng phng php iuch pha cu phng QPSK (Quadrature Phase Shift Keying) v iu ch bin cu phng QAM (Quadrature Amplitude Modulation).

- Tiu chun 802.16-2004 c ban hnhnm a ra thng 7 nm 2004 m r ng cc c im k thut ca WiMAX di tn s 2-11GHz, s dng

phng thc iu ch ghp knh phn chia tn s tr c giao OFDM


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(Orthogonal Frequency Division Multiplexing). 802.16-2004 c th cung c pcc dch v c nh, nomadic (ng i s dng c th di chuyn nhng c nh

trong lc k t ni) theo tm nhn thng LOS v khng theo tm nhn thng NLOS (Non Line Of Sight). 802.16-2004 m t h s h thng WiMAX v s ph h p tiu chun n mi tr ng mng khng dy t ng, gi i thiu v kiu mt l i. IEEE 802.16-2004 l kh nng truyn t node t i cc nodexung quanh.

- Tiu chun IEEE 802.16e-2005 cn gi l Mobile WiMAX hay WiMAX di

ng, c ban hnh vo thng 12 nm 2005. Tiu chun ny s dng phngthc iu ch SOFDMA (Scalable Orthogonal Frequency DivisionMultiplexing Access), cho php thc hin cc chc nng chuyn vng vchuyn mng, c th cung cp ng th i dch v c nh, nomadic, di nghn ch v di ng. IEEE 802.16e-2005 hot ng cc bng tn nh hn6GHz, tc ln t i 15Mbps v i knh 5MHz, bn knh cell t 2 - 5km. IEEE802.16e-2005 h tr h thng thch nghi aanten AAS (Adaptive Antenna

Systems) v cng ngh MIMO (Multiple Input and Multiple Output). Ngoi ratiu chun ny cng ci tin cc kh nng tit kim cng sut cho cc thit b di ng v cc c im bo mt linh hot hn.

- Tiu chun m i nht IEEE 802.16m-2011 l cng ngh ct li cho WiMAX2. c t k thut ca WiMAX 2 c xy dng trn IEEE 802.16mm bokh nng tng thch ng c v cng tn ti v i chun trc . Trm gc

802.16m s lm vic v i thit b u cui 16e v 16m. Nhng telco ang s dng 16e hin ti s c 2 h ng la chn: chuyn mt phn sang 16m haychuyn tt c. Kin trc khung ca 16m c kh nng tn ti song song v i h thng 16e. im ci thin ni bt ca WiMAX 2 so v i WiMAX th h utin l tc - tc WiMAX 2 ln n 300Mbps, WiMAX 2 h tr 2 k thut a anten chnh l SU-MIMO (Single User Multiple Input MultipleOutput) v MU-MIMO (Multiple User Multiple Input Multiple Output).

WiMAX 2 h tr c 2 di bng tn ca phin bn u tin v phin bn IEEE


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802.16-2009. IEEE 802.16m h tr bng thng c r ng 5MHz, 10MHz,20MHz v 40MHz v i mt t p hp a sng mang ln n 100MHz. Cht

l ng dch v QoS (Quality of Service) l mt giao thc quan tr ng trongIEEE 802.16m, c s dng trong vic phn b ti nguyn v tuyn v lul ng theo lch trnh, QoS c th kim sot h ng ti ln. Ngoi ra, WiMAX 2cn c tr kh thp, iu ny s gip cc dch v VoIP tr nn thng suthn.

- Cng ngh WiMAX l gii php cho nhiu loi ng dng bng rng tc

cao cng thi im v i khong cch xa v cho php cc nh khai thc dch v hi t tt c trn mng IP cung c p d liu, thoi v video. WiMAX v i s h tr QoS, kh nng vn xa v tc truyn d liu cao c dnh cho ccng dng truy cp bng rng nhng vng xa xi, ho lnh nht l khikhong cch qu ln i v i mng hu tuyn cng nh cho cc khu vc thnhth cc nc ang pht trin. Nhng ng dng cho h dn gm c Internettc cao, thoi qua IP, video cht lng cao v tr chi trc tuyn. i v i

doanh nghi p c ng dng nh hi ngh truyn hnh, gim st video v mngringo bo mt.

Hnh 1.9 M hnh cng ngh WiMAX


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thc truy nh p v tuyn dng chung SWAP (Shared Wireless AccessProtocol) c thit k cho c d liu v ting ni.

- Cng ngh DLNA (Digital Living Network Alliance): DLNA l mt t chcthng mi phi l i nhun thnh l p bi Sony trong thng 6 nm 2003 vi hn230 thnh vin l cc cng ty thuc nhiu ngnh cng nghi p khc nhau trnkh p th gii, nh in t tiu dng, in thoi di ng, my tnh c nhn,cung c p dch v, t v cng nghi p bn dn. H to ra DLNA v i mc chgip ng i dng c th trao i d liu gia cc sn phm k thut s mt

cch d dng v thun tin hn. Mc tiu chung ca DLNA l t ra cc tiuchun v nguyn tc cho cc thit b mng gia nh v phng tin gii tr,mt khi chng t chun DLNA (DLNA Certified) th d dng chia s nidung video HD, nhc, hnhnh v i nhau trong mng ni b, bt k thit b thuc dng no hay ca nh sn xut no. DLNA s dng giao thc UpnP(Universal Plug and Play) trong vic qun l v iu khin ngun ti nguyna phng tin. Theo , UPnP s xc nh r rng nhng dng thit b m

DLNA h tr cng nh phng thc truy cp th vin gii tr ny quamng ni b nh th no v nhng nguyn tc ca DLNA s c p dngcht ch trong nh dng d liu, chun m ha v phn gii m thit b h tr . Hin ti, nhng dng thit b t chng nhn h p chun DLNA c tchra thnh 3 l p sau: l p thit b mng gia nhHND (Home Network Devices),l p thit b di ng cm tay MHD (Mobile Handheld Devices), l p thit b cs h tng HID (Home Infrastructure Devices).

- Cng ngh Zigbee: l mt giao thc c xy dng theo chun IEEE802.15.4. Giao thc ny c to ra nhm phc v cho nhng ng dng yucu gi thnh v cng sut thp nhng phi c kh nng linh ng trong phmvi r ng. Chun Zigbee c pht trin v xc tin b i hng Zigbee Alliance,v i s h tr t hn 200 cng ty trn th gii nh: SIEMENS, ATMEL, NEC,TEXAS INSTRUMENTS, EPSON....Zigbee c dng vo r t nhiu ng

dng trong cuc sng nh: Cc h chiu sng thng minh, HVAC (Heating,


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Ventilation and Air Conditioning), Cng nghi p, Sensor khng dy, bnhvin....

- Cng ngh HiperLAN (High Performance Radio Local Area Networks): lmt mng LAN khng dy theo chun ca Chu u, c ban hnh b i ETSIvo nm 1992, tng ng v i cng ngh IEEE 802.11. HiperLAN hotng bng tn 2,4n 17GHz, c tc d liu khong 54Mbps v chunny cng h tr cho cc ngi dng di ng tc th p.

1.3.2 Nhng giao thc s dng trong mng khng dy:

Giao thc khng dy tngng dng WAP (Wireless Application Protocol)- WAP l mt tiu chun k thut truy c p thng tin qua mt mng inthoi di ng khng dy. Mt trnh duyt WAP l mt trnh duyt web chothit b di ng nh in thoi di ng hay PDA. Phin bn m i nht WAP 2.0c ban hnh vo nm 2002. - M hnh WAP chnh l m hnh WWW (World Wide Web) v i mt s tnhnng nng cao. Trong , hai tnh nng quan trng nht l: y v h tr thoi. Ni dung thng tin WAP c truyn ti nh mt t p cc giao thc truynthng tiu chun trong t p giao thc WAP.- WAP nh ngha mt t p cc thnh phn tiu chun cho php truyn thnggia thit b u cui v my ch mng gm:

M hnh tn tiu chun: Cc URL (Uniform Resource Locator) c s dng nhn dng ni dung WAP trn cc my ch, URL c s dng

nhn dng ti nguyn trong mt thit b, v d nh chc nng iukhin cuc gi.

Kiu ni dung:c a ra trn kiu c trng ging nh WWW. Cc khun dng ni dung tiu chun: da trn cng ngh WWW v bao

gm ngn ng nh du, thng tin lch, cc i t ng, hnhnh v ngnng k ch bn.


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Cc giao thc truyn thng tiu chun: cho php truyn thng cc yu cuu cui di ng t i my ch mng thng qua cng WAP.

- Tng t nh m hnh kt ni h thng m OSI (Open SystemsInterconnection), cc ngn x p ca giao thc WAP c chia thnh cc l pcho php d dng m r ng, thay i v pht trin. Tt c cc ngn x p giaothc WAP u c thit k ph h p vi cc iu kin rng buc ca mngdi ng. Mi mt l p cung c p mt t p cc chc nng hoc cc dch v t i ccdch v vng dng khc qua t p giao din tiu chun.- Kin trc WAP tch cc giao ti p dch v t cc giao thc cung c p dch v cho php m r ng cc c tnh v t do la chn cc giao thc thch h pcho mt ni dung c th. R t nhiu cc dch v trong ngn x p c th c h tr b i mt hoc nhiu giao thc. Giao thc truy nh p ng dng v tuynWAP gm c 5 l p:

L p truyn ti: giao thc datagram v tuyn WDP (Wireless DatagramProtocol), l p ny cung c p s hi t gia cc dch v mang v i cc phn

cn li ca ngn x p WAP. L p bo mt: giao thc l p truyn ti v tuyn WTLS (Wireless Transport

Layer Security), mc tiu l m bo tnh nng bo mt gia cc thit b u cui WAP v cng/y quyn WAP.

L p giao vn: giao thc giao vn v tuyn WTP (Wireless TransactionProtocol), c nhim v p ng cc yu cu v tr l i v phng tintruyn thng t ng i s dng t i my ch ng dng v ng c li.

L p phin: giao thc phin v tuyn WSP (Wireless Session Protocol), h tr l p ng dng ca WAP m t trong phin v i mt giao ti p ca 2 dchv phin: k t ni c hng m bo tin cy v phi k t ni khng m bo tin cy

L p ng dng: Mi tr ng ng dng v tuyn WAE (WirelessApplication Enviroment), nm trong l p ng dng cung cp mi tr ng


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cho php m r ng min ccng dng c s dng trn cc thit b vtuyn bao gm c dch v tin nhn a phng tin.

Giao thc khng dy tng mng:- ExOR (Extremely Opportunistic Routing): l s k t h p ca giao thc nhtuyn v iu khin a truy nh p MAC (Media Access Control) cho mt mngkhng dy Ad-hoc v i thut ton nhsau: ngun thng tin pht qung b mtl ng cc gi tin.- HSLS (Hazy Sighted Link State): l mt giao thc nh tuyn cho mng l ikhng dy,y l mt thut ton cho php cc my tnh giao ti p thng quai pht thanh k thut s trong mt mng l i chuyn ti p cc tin nhnn cc my tnh ra khi tm v i ca vng v tuyn tr c ti p.- DSR (Dynamic Source Routing): l mt giao thc nh tuyn cho mng l ikhng dy, n to thnh mt ng truyn khi c mt yu cu t my tnhtruyn i, n s dng ngun nh tuyn thay v bng nh tuyn ti mi thit b trung gian.

Giao thc Internet khng dy WIP (Wireless Internet Protocol):

- WIP l b cc giao thc khng dy sau WAP 2.0. N bao gm XHTML(Extensible HyperText Markup Language)c bn, Nokia XHTML MobileProfile, v s pht trin tng lai ca WAP do Open Mobile Alliance .

- Giao thc Internet khng dy c th cung c p cc trang XHTML v i ccthit b khng dy thch h p m khng cn HTTP proxy (Hypertext Transfer

Protocol), cc trang web c th c phn hi khc nhau trong cc trnh duytweb v trn thit b cm tay m khng cn hai phin bn khc nhau ca cngmt trang.

Giao thc nh tuyn khng dy WRP (Wireless Routing Protocol):- WRP l l mt giao thc nh tuyn ch ng cho mng v tuyn ty binMANETs (Mobile Ad-hoc Networks), s dng nh mt phin bn nng cao


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ca giao thc nh tuyn distance-vector , trong s dng cc thut tonBellman-Ford tnh ton ng dn.

- Do tnh cht di ng ca cc nt trong Manet, giao thc a ra c ch lmgim vng l trnh v m bo trao i tin nhn ng tin cy.

Giao thc chuyn ti lin lc khng dy WCTP (Wireless CommunicationsTransfer Protocol):- WCTP l phng php c s dng gi tin nhn n cc thit b khngdy trn mng dch v lin lc c nhn bng h p NPCS (Narrowband PersonalCommunications Service). Phin bn hin ti l WCTP 1.3.- WCTP cung c p mt cch n gin to mt lin k t gia Internet v mtTAP ph phn trang thit b u cui. WCTP c bit nhm to ra mt phng tin d dng chuyn thng i p ch s nh phnn v i t cc h thng dy v cc thit b khng dy c kh nng hai chiu.- WCTP c to ra cung c p mt tiu chun cng nghi p khng dycho vic gi tin nhn khng dy thng qua Internet. WCTP l mt cch gi

tin nhn khng dy, c mt v hai chiu, v i cc thit b nhn thch hp nhmy nhn tin, in thoi di ng hoc cc thit b khng dy khc.

1.4 u im v nh c i m ca mng khng dy:

1.4.1 u im ca mng khng dy:

Tnh ding: to ra s thoi mi trong vic truyn ti d liu gia cc thit b c h tr m khng c s rng buc v khong cch v khng gian nh mng

c dy thng thng. Ng i dng mng khng dy c th k t ni vo mngtrong khi di chuyn bt c ni no trong phm vi ph sng ca thit b truyc p. iu ny s p ng k p th i yu cu v th i gian v ci thin hiu suttrong vic cung c p dch v, tha mn nhu cu v thng tin m cc mng hutuyn khng th c c.


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Tnh n gin: lp t, thit l p, k t ni mt mng my tnh khng dy l r td dng, n gin v c th trnh c vic trin khai dy cp phc t p. Ngoi

ra cn thun l i cho vic bo tr v sa cha thit b v h thng mng. Tnh linh hot: c th trin khai nhng ni m mng hu tuyn khng th

trin khai c nh vng xa xi, ho lnh. Nhng vng ny nm ngoi kh nng trin khai mng hu tuyn do kh khn trong vic thi cng v chi phl n.

Tit kim chi ph lu di:Trong khi u t cn thit ban u i v i phncng ca mt mng my tnh khng dy c th cao hn chi ph phn cng camt mng hu tuyn nhng ton b ph tn lp t v cc chi ph v th i giantn ti c th thp hn ng k. Chi ph di hn c l i nht trong cc mitrng ng cn phi di chuyn v thay i th ng xuyn.

Kh nng thay i v m r ng: Cc h thng mng khng dy c nh hnhtheo cc kiu topo khc nhau p ng cc nhu cu ca ccng dng v ccci t c th. Cu hnh mng d thay i t cc mng c l p ph h p v i s

nh ngi dng n cc mng c s h tng vi hng nghn ng i s dngtrong mt vng r ng l n.

1.4.2 Nhc im ca mng khng dy:

Phm vi ng dng: cc h thng mng khng dy ch ph h p v i phm vinh nh nh gia nh, qun cafem khng th p ng nhu cu mt phm vi ln hn nh mt ta nh, khu dn c.

Tc : tc c gi i hn do ph thuc vo bng thng v k thut truyn tnhiu.

tin cy: v s dng sng v tuyn nn kh nng b nhiu r t l n, tn hiucn b suy gim do s dng chung di tn v i cc thit b gia nh.

Bo mt: do truyn trong mi trng khng dy v c tnh ca mng mnhiu ng i c th truy c p v ph hoi dn n an ton v nguyn vn cathng tin khng cao.


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1.4.3 So snh mng khng dy v mng c dy:

Bng 1. So snh m ng khng dy v m ng c dy

H thng Mng c dy Mng khng dy

Phm ving dng

- C th ng dng trong ttc cc m hnh mng nh,trung bnh, l n, r t l n

- Gp kh khn nhng

ni xa xi, a hnh phct p, nhng ni khng nnh, kh ko dy, ngtruyn

- Ch yu l trong m hnh mngnh v trung bnh, v i nhng mhnh l n phi k t h p v i mng cdy

- C th trin khai nhng nikhng thun tin v a hnh,khng n nh, khng trin khaimng c dy c

Bo mt

v tin cy

- Kh nng chu nh hngkhch quan bn ngoi nhthi tit, kh hu tt

- B nh hng bi cc yu t bnngoi nh mi trng truyn sng,can nhiu do thi tit

- Kh nng an ton thp hn so vimng c dy

Thi cngv trin

khai

- Thi cng phc tp do phi thit k li ton b hthng.

- Thi cng trin khai nhanh chng,n gin v d dng

Kh nng

m rng

- i hi chi ph cao khimun m rng h thngmng c bit l m rng bng cp quang

- Kh nng m rng khong cchtt vi chi ph hp l.

Tnh linhhot

- Cc v tr thit k khngc ng phi thit k linu thay i cc v tr ktni mng

- Cc v tr kt ni mng c ththay i m khng cn phi thitk li


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1.5 Mt s ng dng ca mng khng dy:

1.5.1 Vai tr truy c p:

Mng khng dy ngy nay hu nh c trin khai l p truy nh p, ngha lchng c s dng mt im truy c p vo mng c dy thng th ng. K tni khng dy l mt phng php n gin ng i dng c th truy c pvo mng, y lmng l p lin k t d liu nh tt c nhng phng phptruy c p khc. V tc thp nn WLAN t c trin khai mng li v h thng phn phi.

Ti mi im cung c p dch v truy c p Internet khng dy ny, nh cung c pdch v t cc AP, hoc cc anten thu pht tn hiu, cho php nhng khchhng c my tnh xch tay hoc thit b di ng c tch h p cng ngh khngdy Wi-Fi truy c p Internet m khng cn dy dn. Gii php ny c bit phh p v i vic cung c p dch v truy c p internet cng cng cho ccim cngcng nh: Sn bay, Nh ga, Tr ng hc, Bnh vin, Trung tm Hi ngh,Trin lm, Sn vn ng, Khch sn, Nh hng,Cc to nh thng mi...

1.5.2 M r ng mng:

Cc mng khng dy c th c xem nh mt phn m r ng ca mi mngc dy. Khi mun m r ng mng c dy hin tai, trin khai cp v ci t dchv s kh khn v tn km. V vy, mng khng dy l s la chn ti u chovic m r ng v i kh nng lp t n gin, nhanh chng v ci t d dng.

Bn cnh , ti nhng vng ho lnh, xa xi vi a hnh phc t p khin victrin khai cp r t phc t p v i chi ph r t l n, trin khai h thng mng khngdy l gii php thc t v c hiu qu cao.

1.5.3 K t ni cc ta nh:

Trong mi tr ng mng chi nhnhhay trong mi tr ng c 2 to nh st nhau,c th c tr ng h p cc ng i dng t to nh ny mun truy c p vo tinguyn ca to nh khc. Trong qu kh th tr ng hp ny c gii quyt

bng cch i mt ng cp ngm gia 2 to nh hay thu mt ng knh


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ring t cng ty in thoi. S dng k thut mng khng dy, thit b c th c ci t mt cch d dng v nhanh chng cho php 2 hay nhiu to nh

chung mt mng. V i cc loi anten khng dy ph h p, th bt k to nh nocng c th k t ni v i nhau vo cng mt mng trong mt khong cch cho php.

C 2 loi k t ni: im - im P2P (Ponit to Point)l cc k t ni khng dygia 2 to nh. Loi k t ni ny s dng cc loi anten tr c ti p hay bn tr cti p mi u lin k t. im -a im P2MP (Point to Multi Point) l cc k tni khng dy gia 3 hay nhiu to nh, th ng dng hub-andspoke haykiu k t ni hnh sao, trong mt to nh ng vai tr trung tm t p trungcc im k t ni. To nh trung tm ny s c mng li, k t ni internet, vmy ch. Cc lin k t P2MP gia cc to nh th ng s dng cc loi antena hng trong to nh trung tm v anten chung h ng trn cc spoke.

1.5.4 Kh nng di ng:

Ch l mt gii php l p truy nh p nn WLAN khng th thay th mng cdy trong vic tc truyn. Mt mi tr ng khng dy s dng cc k t nikhng lin tc v c t l li cao. Do , cc ng dng v giao thc truyn d liu c thit k cho mng c dy c th hot ng km trong mi tr ngkhng dy. L i ch m cc mng khng dy mang li chnh l tng kh nng ding b li tc v QoS.

Trong tng tr ng h p, cc mng khng dy to nn kh nng truyn d

liu m khng cn yu cu th i gian v sc ngi a d liu, cng nhgim c cc thit b c k t ni vi nhau nh mng c dy. Mt trongnhng k thut m i nht ca mng khng dyl cho php ng i dng c th chuyn vng, ngha l di chuyn t khu vc khng dy ny sang khu vc khcm khng b mt k t ni, ging nh in thoi di ng, ng i dng c th chuyn vng gia cc vng di ng khc nhau. Trong mt t chc l n, khi phm vi ph sng ca mng khng dy r ng th vic chuyn vng kh quan

tr ng v ng i dng c th vn gi k t ni v i mng khi h ra ngoi.


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1.5.5 Hi thoi v truyn d liu:

in thoi di ng lng dng ni bt v ph bin nht ca mng khng dy.Cc in thoi khng dy s dng sng v tuyn cho php h ng i dngthc hin cuc gi in thoi t nhiu a im trn ton th gi i. S phttrin khng ngng ca mng thng tin di ng ngoi vic nng cao cht l ngca cuc gi th n cn cung c p cc dch v tin ch v s liu v truy c pInternet.

Truyn d liu khng dy l mt thnh phn thit yu ca in ton di ng.

Cc cng ngh khc nhau c sn khc nhau sn c ca a phng, phm vi ph sng v hiu sut, v trong mt s tr ng hp, ng i s dng phi s dng nhiu loi k t ni v chuyn i gia chng.


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CH NG 2 . TNG QUAN V CNG NGH WIFI

2.1 Khi nim, s ra i v pht trin ca Wifi:

2.1.1 Khi nim cng ngh Wifi:

Cng ngh Wifi c pht trin da trn chun IEEE 802.11 c to ra vduy tr b i Tiu ban Tiu chun LAN/MAN (IEEE 802) ca Vin K s inv in t IEEE. Tiu ban ny c ch nh b nh danh 802 nn michun c quyt nh b i tiu ban ny s bt u v i b nh danh 802. IEEE802.11 l t p h p cc tiu chun ca t chc IEEE bao gm cc c t k thutlin quan n h thng mng khng dy, hay ni cch khc l c lin quan ns iu bin trong khng gian.

Hnh 2.1 Bi u t ng cng ngh Wifi

IEEE l mt t chc khoa hc ngh nghip c xy dng nhm mc ch h tr cc hot ng nghin cu khoa hc, thc y s pht trin khoa hc cngngh trong cc lnh vc in t, vin thng, cng ngh thng tin, khoa hcmy tnh. Vin ny gm c nhiu k s in v in t, h l cc chuyn giatrong tng lnh vc. T chc cc chun ny ra i xut pht t s cn thit cnc cc chun c ch p thun r ng ri bo m kh nng tng thch giacc thit b trn ton th gii. y chnh l mt trong nhng nhim v kh

khn nht ca IEEE, bo m s ch p thun r ng ri; mt nhim v m h khng phi lc no cng thc hin c. Cc chun c cng b b i IEEE


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bao gm tt c cc lnh vc k thut in t c lin quan n mng my tnh.T chc ny chnh thc hot ng u nm 1963 v hin nay c khong400000 thnh vin. n nm 2005 c gn 900 tiu chun c ban hnh vhot ng trn thc t.

Wi-Fi Alliance l mt hi p hi thng mi nhm thc y cng ngh mngcc b khng dy v chng nhn sn phm nu chng ph h p v i cc tiuchun nht nh ca kh nng tng tc. Wi-Fi Alliance s hu thng hiuWi-Fi. Cc nh sn xut c th s dng thng hiu cho cc sn phm cchng nhn thuc v mt phn ca thit b WLAN da trn chun IEEE

802.11. Wi-Fi Alliance cng s hu v kim sot cc biu t ng Wi-Fi CERTIFIED -

nhn hiu ng k ch c c p php cho thit b qua th nghim. Qutrnh c p giy chng nhn bao gm ba loi xt nghim m bo kh nngtng tc. Cc sn phm Wi-Fi CERTIFIED c kim tra v kh nng tngthch v i cc thit b c chng nhn, kim tra s ph h p ca thit b v icc yu t ca chun IEEE 802.11, kim tra hiu sut v i vic p ng cc c p

hiu nng cn thit p ng s mong i ca ng i dng trong ccngdng quan tr ng.

Wifi l mt cng ngh ph bin cho php mt thit b in t trao i d liu khng dy bng cch s dng sng v tuyn trn mt mng my tnh.Chun ny p dng cho vic thc hin lin lc trong mng khng dy ni b WLAN, dng cho cc thit b di ng c h tr Wireless, phc v cho ccthit b c phm vi hot ng tm trung bnh.

Mng Wifi l h thng mng khng dy s dng sng v tuyn, ging nhin thoi di ng, truyn hnh v radio. H thng nythng th ng hot ng mt s sn bay, qun cafe, th vin hoc khch sn. H thng cho php truyc p Internet ti nhng khu vc c sng ca h thng ny, hon ton khng cnn cp ni. Ngoi cc im k t ni cng cng (hotspots), WiFi c th cthit l p ngay ti nh ring.


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2.1.2 S ra i v pht trin cng ngh Wifi:

Nm 1985, y ban lin lc lin bang M FCC (Federal Communications

Commission), quyt nh m ca mt s bng tn ca di sng khng dy,cho php s dng chng m khng cn giy php ca chnh ph. yl mtiu kh bt th ng vo thi im . Tr c s thuyt phc ca cc chuynvin k thut, FCC ng th 3 di sng cng nghi p, khoa hc v y t cho gi i kinh doanh vin thng.

Ba di sng ny, gi l cc bng tn rc (900MHz, 2.4GHz, 5.8GHz), c phn b cho cc thit b s dng vo cc mc ch ngoi lin lc, chng hn

nh l n ng vi sng s dng cc sng v tuyn un nng thc n. FCC a cc bng tn ny vo phc v mc ch lin lc da trn c s : bt c thit b no s dng nhng di sng u phi i vng trnhnh h ng cavic truy c p t cc thit b khc. iu ny c thc hin bng cng ngh gil ph r ng (vn c pht trin cho qun i M s dng), c kh nng phttn hiu v tuyn qua mt vng nhiu tn s, khc vi phng php truynthng l truyn trn mt tn s n l c xc nh r.

Du mc quan tr ng cho Wi-Fi din ra vo nm 1985 khi tin trnh i n mtchun chung c khi ng. Trc , cc nh cung c p thit b khng dydng choLAN nh Proxim v Symbol M u pht trin nhng sn phmc quyn, tc l thit b ca hng ny khng th lin lc c v i ca hngkhc. Nh s thnh cng ca mng hu tuyn Ethernet, mt s cng ty bt unhn ra r ng vic xc l p mt chun khng dy chung l r t quan tr ng. V

ngi tiu dng khi s d dng ch p nhn cng ngh m i nu h khng cn b b h p trong sn phm v dch v ca mt hng c th.

Nm 1988, cng ty NCR, v mun s dng di tn rc lin thng cc myrt tin qua k t ni khng dy, yu cu mt k s ca h c tn VictorHayes tm hiu vic thit l p chun chung. ng ny cng v i chuyn giaBruce Tuch ca Trung tm nghin cu Bell Labs ti p cn v i T chc k s in v in t IEEE, ni m mt tiu ban c tn 802.3 xc l p ra chun


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mng cc b Ethernet ph bin hin nay. Mt tiu ban mi c tn 802.11 rai v qu trnh thng l ng h p nht cc chun bt u.

Th tr ng phn tn thi im ng ngha v i vic phi mt kh nhiuthi gian cc nh cung c p sn phm khc nhau ng v i nhng nhngha chun v ra mt tiu ch m i v i s ch p thun ca t nht 75% thnhvin tiu ban. Cui cng, nm 1997, tiu ban ny ph chun mt b tiu chc bn, cho php mc truyn d liu 2Mbps, s dng mt trong 2 cng ngh di tn r ng l frequency hopping (trnh nhiu bng cch chuyn i lin tcgia cc tn s radio, cn gi l truyn cho) hoc direct-sequence

transmission (pht tn hiu trn mt di gm nhiu tn s, cn gi l truynthng).

Chun m i chnh thc c ban hnh nm 1997 v cc k s ngay l p tc btu nghin cu mt thit b mu tng thch vi n. Sau c 2 phin bnchun, 802.11b hot ng trn bng tn 2,4GHz v 802.11a hot ng trn bng tn 5,8GHz, ln lt c ph duyt vo nm 1999. Sau khi c chun802.11b, cc cng ty bt u pht trin nhng thit b tng thch v i n. Tuy

nhin, b tiu ch ny qu di v phc t p v i 400 trang ti liu v vn tng thch vn ni cm. V th, vo thng 8/1999, c 6 cng ty bao gmIntersil, 3Com, Nokia, Aironet (v sau c Cisco sp nh p), Symbol vLucent lin k t vi nhau to ra Lin minh tng thch Ethernet khng dyWECA (Wireless Ethernet Compatibility Alliance).

Mc tiu hot ng ca t chc WECA l xc nhn sn phm ca nhng nhcung c p phi tng thch thc s v i nhau. Tuy nhin, cc thut ng nhtng thch WECA hay tun th IEEE 802.11b vn gy bi r i i v i c cng ng. Cng ngh m i cn mt cch gi thun tin i vi ng i tiudng. Cc chuyn gia t vn xut mt s ci tn nh FlankSpeed hayDragonFly. Nhng cui cng c ch p nhn li l cch gi Wi-Fi vnghe va c v cng ngh cht l ng cao (hi-fi) v hn na ng i tiu dngvn quen v i kiu khi nim nh u a CD ca cng ty no th cng u

tng thch v i b khuch i amplifier ca hng khc. Th l ci tn Wi-Fi ra


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i. Cch gii thch Wi-Fi c ngha lWireless Fidelity v sau ny ng i tami ngh ra. Gn y, nhiu chuyn gia cng vit bi khng nh li Wi-Fithc ra ch l mt ci tnt ra cho d gi ch ch c ngha g ban u.

2.2 Cc tiu chun ca Wifi:

2.2.1 Cc tiu chun ph bin ca Wifi:

Tiu chun IEEE 802.11 - 1997:- Thng 6 nm 1997, IEEEa ra chun mng ni b khng dy (WLAN) utin l 802.11 theo tn ca nhm gim st s pht trin ca chun ny. Lcny, 802.11 s dng bng tn ISM v i tn s 2,4GHz v h tr bng thng1Mbps v 2Mbps. Chun 802.11-1997 cho php ba cng ngh khc nhauc th s dng: hng ngoi, tr i ph nhy tn s FHSS (Frequency HopingSpread Spectrum) v tr i ph chui tr c ti p DSSS (Direct Sequence SpreadSpectrum). Do tc kh chm cho hu ht ccng dng nn cc sn phmchun khng dy ny khng cn c sn xut na.

Tiu chun IEEE 802.11a:

- IEEE 802.11ac IEEE ban hnh vo thng 9 nm 1999,l mt chun c ci thin t 802.11-1997. Trong khi 802.11-1997 ch c th truyn ti d liu v i tc 2Mbps th 802.11a c th truyn ti d liu v i tc 54Mbps,chun ny tuy c cng tc v i chun 802.11g nhng chun ny c tn s hot ng cao nht l 5Ghz. Bng thng l n nn cha c nhiu knh hnhai chun 802.11b v 802.11g. Nhng do chun ny c tn s hot ng caohn tn s ca cc thit b vin thng nn h thng s dng mng khng dythit b 802.11a t b nh h ng ca sng. cng chnh l nguyn nhn lmcho h thng mng khng dy s dng chun ny khng tng thch v i cch thng mng khng dy s dng chun 802.11b, 802.11g. Chun 802.11at tc 36->54Mbps trong phm vi 10->15m- IEEE 802.11a s dng mt phng thc m ha c gi l ghp knh phnchia tn s tr c giao OFDM (Orthogonal Frequency Division Multiplexing),

y c coi l k thut tr i hn so v i tr i ph chui tr c ti p DSSS. OFDMhot ng bng cch chia nh knh truyn d liu tc cao thnh nhiu knh


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truyn ph c tc thp hn, v sau s c truyn song song. Mi knhtruyn tc cao c r ng l 20MHz v c chia nh thnh 52 knh ph,mi ci c r ng khong 300kHz. OFDM c tc truyn cao hn v ckh nng phc hi li tt hn, nh vo k thut m ha v sa li ca n.- Ngoi vic tng v tc , mt u im khc trong vic s dng tn s 5GHzl khng c nhiu thit b s dng tn s ny, v vy kh nng xuyn nhiugia cc thit b s gim. Mc d vy vic s dng bng tn 5GHz cng cmt nhc im l n. Do tn s 5GHz s dng sng ngn nn k thut ny c phm vi ph sng km hn v tn hiu b cn tr nhiu hn b i nhng vt cn

nh cc bc t ng; thm ch khng c nhiu bc tng nhng nu tn hiutruyn trong khng gian c nhiu i t ng (bn v gh,) cng tn hiu b suy gim r t nhanh.Do chi ph cao hn, 802.11a th ng ch c s dngtrong cc mng doanh nghip, ng c li, 802.11b thch hp hn cho nhu cugia nh.

Tiu chun IEEE 802.11b:- Song hnh v i 802.11a, IEEE ti p tc a ra chun m r ng th hai cng

da vo 802.11 u tin l 802.11b, v i tn s hot ng 2,4GHz. Vic ti ptc s dng tn s 2,4GHz c c u im v nhc im. u im y ltn s ny khng b iu chnh li v v vy gi thnh chi ph sn xut s r hn.- Thay i ch yu trong 802.11b l tc d liu ti a. Tc d liu ti aca 802.11b t khong 11Mbps, con s c th so snh v i tc Ethernettruyn thng nhng nm 1999 v 2000. V i tc ny, nhiu khch hng cth s dng Wi-Fi v tha h ng tt c nhng u im v kh nng di ngm khng b cc nhc im v tc . Cng v i vic gim c nh k githnh trong cng ngh lm cho cng ngh 802.11b c s ch p thun mtcch r ng ri.- IEEE 802.11b s dng k thut DSSS v giao thc a truy c p cmng sngmang chng va chm CSMA/CA (Carrier Sense Multiple Access with

Collision Avoidance). Do giao thc trn CSMA/CA, trong thc t 802.11b c


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tc ti a m mt ng dng c th t c l khong 5,9Mbps s dnggiao thc iu khin truyn vn TCP (Transmission Control Protocol) v7,1Mbps s dng UDP (User Datagram Protocol). Chun 802.11b tha h ngk thut DSSS t chun 802.11-1997 ban u v s dng k thut kha m bCCK (Complementary Code Keying). CCK s dng mt t p 64 t c m 8 bit,cho php chng c bn nhn nhn ra mt cch chnh xc v i cc k thutkhc, ngay c khi c s hin din ca nhiu.- V i tc 5,5Mbps s dng CCK m ha 4 bit mi sng mang, v v itc 11Mbps m ha 8 bit mi sng mang. C hai tc u s dng k

thut iu ch kha dch pha cu phngQPSK (Quadrature Phase ShiftKeying) v tn hiu 1,375MB ps. V FCC iu chnh nng l ng u ra thnh1W EIRP (Effective Isotropic Radiated Power). Do v i nhng thit b 802.11, khi di chuyn ra khi sng radio, radio c th thch nghi v s dng k thut m ha phc tp hn gi d liu v k t qu l tc chm hn. - Mt trong nhng nhc im ca IEEE 802.11b l bng tn d b nghn vh thng d b nhiu b i cc h thng mng khc, l vi ba, cc loi in thoi

hot ng tn s 2,4 GHz v cc mng Bluetooth. ng th i IEEE 802.11bcng c nhng hn ch nh: thiu kh nng kt ni gia cc thit b truynging ni, khng cung c p cht l ng dch v QoS (Quality of Service) chocc phng tin truyn thng.

Bng 2.1 Cc l a ch n ca chu n 802.11b

Tc d liu M v di m iu ch

Tc kt Bits/Symbol

1Mbps 11(Baker sequence) BPSK 1MSps 1

2Mbps 11 (Baker sequence) QPSK 1MSps 2

5,5Mbps 8 (CCK) QPSK 1.375MSps 4

11Mbps 8 (CCK) QPSK 1.375MSps 8


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Tiu chun IEEE 802.11g hay IEEE 802.11g-2003:- Khi tc Ethernet tng, iu ny tc ng n chun 802.11, thng7/2003, IEEE ph chun 802.11g. Chun ny c gng k t h p tt nht 802.11av 802.11b, hot ng tn s 2.4 GHz ging nh 802.11b v 802.11-1997 .- IEEE 802.11 s dng k thut OFDM, c th cung c p cc dch v c tc ln t i 54Mbps. Trc y, FCC cm s dng OFDM ti 2,4GHz. Nhnghin nay FCC cho php s dng OFDM ti c hai bng tn 2.4GHz v5GHz.802.11g cng c h tr CCK.- Mt thun l i r rng ca 802.11g l tng thch vi 802.11b ( c s dng

r t r ng ri ) v c c tc truyn cao nh 802.11a . Tuy nhin s knh tia m 802.11g c s dng vn l 3 nh 802.11b. Bn cnh , do hot ng tn s 2,4 GHz nh 802.11b, h thng s dng 802.11g cng d b nhiunh 802.11b.

Tiu chun IEEE 802.11n:- V i nhu cu ngy cng cao ca ng i s dng, tc 11 Mbps ca chun802.11b, 54Mbps ca chun 802.11a/g d r t h p dn nhng cng cha tha

yu cu ca ngi dng. p ng nhu cu ngy cng cao hn , IEEE hnh thnh nhm lm vic pht trin chun 802.11n. Phm vi lm vic canhm ny l nh ngha iu chnh l p vt l v lp MAC chuyn giao mtgi tr nh nht 100Mbps thng qua mt im truy nh p dch v MAC. Chun802.11n c IEEE ph duyt a vo s dng chnh thc vo thng 10nm 2009 v cng c Hi p hi Wi-Fi (Wi-Fi Alliance) kim nh v c pchng nhn cho cc sn phm t chun.

- 802.11n s dng mt quan im pht trin ang s dng ti cc cng ngh hin hu trong khi gi i thiu cng ngh m i chng cung c p hiu qu lm vic s pht trin thy c yu cu ca vic pht trin nhng ngdng. S dng li nhng cng ngh qu bu nh OFDM, m ha sa li t pha trc, an xen v nh x iu bin bin cu phng c sa vgi li, gi c gim xung v hon tontng thch v i cc cng ngh tr c.


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- Mt trong nhng iu mong i nht ca ng i dng thit b u cui Wi-Fikhng g khc ngoi tc v tm ph sng. Theo c t k thut, chun802.11n c tc l thuyt ln n 600Mbps (cao hn 10 ln chun 802.11g)v vng ph sng r ng khong 250m (cao hn chun 802.11g gn 2 ln,140m). Hai c im then cht ny gip vic s dng ccng dng trong mitr ng mng Wi-Fi c ci tin ng k, phc v tt cho nhu cu gii tr a phng tin, nhiu ng i dng c th xem phim cht l ng cao, gi in thoiqua mng Internet (VoIP), ti tp tin dung l ng ln ng th i... m chtl ng dch v v tin cy vn lun t mc cao.

- Chun 802.11n h tr k thut OFDM tt hn, h tr bng thng rng hnv tc m ha cao hn tng tc t ti a 65Mbps so v i 52Mbps cachun 802.11a v 802.11g. 802.11n s h tr tc ln n 300Mbps.802.11n cng cho tm ph sng tt hn cc chun Wi-Fi trc nh tngcng tn hiu. Chun 802.11n xy dng trn cc chun 82.11 trc bng cch thm vo anten MIMO, cc knh 40 MHz v s k t h p khung trnl p MAC.

- Anten MIMO s dng nhiu anten gi nhiu thng tin hn so v i khi s dng mt anten. N to ra phn t p anten v ghp knh khng gian cho802.11n. Chc nng ghp knh phn chia theo khng gian SDM (SpatialDivision Multiplexing) cho php ghp nhiu lung d liu c l p trong mtknh. MIMO SDM c th lm tng ng k tc d liu khi s cc lung d liu trong khng gian tng ln. V i 4 anten cho c hai u cui, chun 802.11n

c th cho tc ln t i 600 Mbps. Cc knh 40MHz, gp i bng thng g pi knh 20MHz s dng trong cc chun 802.11a/g trc , iu ny cho php tng gp i tc d liu trong mt knh n 20MHz. Thit b c th lm vic c c bng 5GHz v 2,4GHz.

- Vi u im l tc nhanh nht, vng ph sng tt nht; tr khng ln hn chng nhiu t cc tc ng ca mi trng, tng lai chun IEEE 802.11n

s ph bin trn ton cu v thay th cc chun IEEE 802.11 khc.


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Bng 2.2 Cc tiu chu n ph bi n ca IEEE 802.11

Tiu chun 802.11a 802.11b 802.11g 802.11n

Tc ti a 54Mbps 11Mbps 54Mbps 300Mbps

K thut sdng OFDM DSSS

DSSS,OFDM OFDM

Tn s 5GHz 2,4GHZ 2,4GHZ 2,4GHz,5GHz

Lung d liu 1 1 1 1 - 4

rng bngthng

20MHz 20MHz 20MHz 20 MHz,40 MHz

600

Combined

300

Tc (Mbps)

150

54

11

140 250

Khong cch truyn

(m)

802.11n Dual band

2.4GHz

5GHz

802.11n 2 Tx / 2 Rx

802.11n 1 Tx / 1 Rx

802.11g

802.11b

Hnh 2.2 T c v kho ng cch truy n d liu ca Wifi

2.2.2 Mt s tiu chun m r ng v ang pht trin ca Wifi:

Tiu chun m r ng: (nm ph chun)- IEEE 802.11c: cc th tc hot ng Bridge (2001).- IEEE 802.11d: m r ng chuyn vng quc t (2001).

- IEEE 802.11e: ci tin cht l ng dch v QoS (2005).- IEEE 802.11i: tng c ng bo mt (2004).


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- IEEE 802.11-2007: bao gm sa i a, b, d, g, h, i, k. (2007).- IEEE 802.11s: sa i cho mng l i (7/2011).- IEEE 802.11v: qun l mng khng dy (2/2011).- IEEE 802.11-2012: bao gm sa i k, n, p, r, s, u, v, w, y, z (3/2012).

Tiu chun ang pht trin:- IEEE 802.11ac: Cung cp lu lng cao trn bng tn 5GHz v i tc lnn 1Gbps, s dng cc knhc bng thng rng 80MHz hoc 160MHz v h tr ln n 8 lung d liu (thay v 4 lung nh 802.11n). - IEEE 802.11ad: Cung cp lu lng cao trn bng tn 5GHz v 60GHz.

Bng tn 60GHz c phm vi ph sng nh do kh nng xuyn thu th p,nhng v i ph tn r ng s h tr lu lng ln n 7Gbps.

2.3 u im v nh c i m ca Wifi:

2.3.1u im ca cng ngh Wifi:

Tnh di ng: cho php ng i dng truy xut ti nguyn mng v trao i d liu bt k ni u trong khu vc c trin khai.

Tinh linh hot: m r ng truy c p nhanh chng, v i s gia tng s ng i s dng my tnh xch tay (laptop) v cc thit b di ng, l mt iu r tthun l i.

Trin khai: thit k v thi cng n gin, vic thit l p h thng mng khngdy ban u ch cn t nht 1 AP. V i mng dng cp, vic trin khai h thngcp nhiu ni trong ta nh l r t phc tp v kh khn. Tit kim th i gianlp t dy cp, khng lm thay i thm m, kin trc ta nh.

Chi ph gim: iu ny c thc hin b i s k t h p ca cc yu t, chi phtng i th p ca cc thit khng dy, gim chi ph thi cng trin khai lp tv bo d ng h thng.

Tnh ph bin: v i mng c dy, cc thit b cn phi c thit k chung 1k t ni vt l, v i k thut Wifi d dng c tch h p trong cc thit b ucui nn nhiu loi thit b khc nhau c th trao i d liu v truy c p

Internet.


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2.3.2 Nhc im ca cng ngh Wifi: Bo mt: mi tr ng k t ni khng dy, truyn d liu bng sng v tuyn

nnng i khc c th d dng thu tn hiu v truy c p mng tri php dn nkh nng thng tin v d liu ca ng i dng b nh c p l r t cao.

Phm vi: mt mng chun IEEE 802.11 v i cc thit b chun ch c th hotng tt trong phm vi vi chc mt. N ph hp trong 1 cn nh,1 khnggian hp nhng v i khng gian r ng th khng p ng c nhu cu. png cn phi mua thm Repeater hay AP, dn n chi ph gia tng.

tin cy: v s dng sng v tuyn nm trong bng tn ISM nn kh nng

nhiu sng v tuyn do th i tit, do cc thit b khng dy khc, hay cc vtchn (nh cc nh cao tng, a hnh i ni), lm gim ng k hiu qu hot ng ca mng.

Tc : mi tr ng truyn l mi tr ng khng kh nn sng v tuyn s chunhiu tc ng ca cc yu t t nhin v cc loi nhiu do cc thit b khcgy ra. Chnh v iu m n nh v cht l ng d liu s km hnmng c dy. Mt trong nhng yu t quan tr ng b nh h ng l tc , tc

ca mng khng dy vo khong 1Mbps - 125Mbps, r t chm so v i mngs dng cp v i tc khong 100Mbps n hng Gbps.

2.3.3. So snh Wifi v cc cng ngh khng dy khc:

Bng 2.3 So snh Wifi v cc cng ngh khng dy khc

Cng ngh Chun Tc Vng ph

sng ti a

Bng tn

UWB 802.15.3a 110-480Mbps 10m 7.5 GHz

Bluetooth 802.15.1 720 Kbps 10m 2.4 GHz

Wi-Fi 802.11a/b11Mbps,54Mbps

100m2.4Ghz,5GHz


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Edge/GPRS 2.5 G 384Kbps 8km 1900 MHz

CDMA2000/1x EV-

DO3G 2,4Mbps 8km

400-2100MHz

WCDMA/UMTS

3G 2Mbps 8km1800-2100

MHz

2.4 Cc thit b c bn ca mng WLAN:2.4.1 im truy c p khng dy Wireless AP (Wireless Access Point):

Hnh 2.3 Access Point chu n N Access Point l thit b c chc nng ging nh thit b Hub trong mng c

dy, thit b ny ni k t v cho php cc my tr m khng dy, c dy c th

truyn d liu v i nhau. Chc nng chnh ca AP l ti p nhn v khuych itn hiu gip tn hiu trong mng khng dy truyn i xa hn, ng th i thit b ny cng c chc quan tr ng khc l chuyn i nh dng d liu giamng khng dy v c dy.

Chc nng ca AP l phc hi tn hiu trong cc segment mng khng dy(ging nh Repeater), chuyn i khun dng d liu gia mng khng dy vmng c dy (ging Gateway). im truy c p ny c th h tr t 15-250

users trong khong cch 20-500m, ty thuc vo cng ngh v mi tr ng.


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Cc im truy c p ny khng ch cung cp trao i thng tin v i cc mng cdy m cn lc lu l ng v thc hin chc nng cu ni v i cc tiu chunkhc. Chc nng lc gip gi gn di thng trn cc knh v tuyn nh loi b cc lu l ng tha. Do bng thng ghp i khng i xng gia thng tin vtuyn v hu tuyn nn cc im truy c p cn c b m thch h p v cc tinguyn ca b nh . Cc b m c dng ch yu lu cc gi d liu im truy c p khi mt nt di ng c gng di chuyn khi vng ph sng hockhi mt nt di ng hot ng ch cng sut th p.

Cc im truy c p trao i v i nhau qua mng hu tuyn qun l cc nt di

ng. Mt im truy c p khng cn iu khin truy c p t nhiu nt di ng,tuy nhin, mt giao thc a truy c p tp trung c iu khin b i mt imtruy c p c nhiu thun li hn.

2.4.2 B nh tuyn khng dy WR (Wireless Router): Router khng dy l thit b mng l p 3 (Network Layer) ca m hnh OSI

(Open Systems Interconnection), c chc nng kt ni hai hay nhiu mng IPv i nhau. IP ca mi my tnh k t ni mng u c th giao tip c v i

Router.

Hnh 2.4 Wireless Router Linksys chu n N

V mt vt l, Router c th k t ni v i cc loi mng khc nhau, t nhngmng Ethernet cc b n mng in thoi ng di. Router phi tnh ton


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nhiu hn tm ra cch dn ng cho cc gi tin khi cc mng k t ni v inhau khng cng tc .

Ging nh router bng thng c dy, router khng dy h tr chia s k t niInternet v i k thut t ng la nm nng cao tnh nng bo mt cho mng.Router khng dy r t ging v i cc im truy c p.

Mt Router hot ng nh mt lin k t gia hai hoc nhiu mng v chuyncc gi d liu gia chng. Router a vo bng nh tuyn (routing table) tm ng i cho gi d liu. Bng nh tuyn c qun tr mng cu hnhtnh (static), ngha l c thit l p 1 ln v th ng do qun tr mng nh p

bng tay, hoc cu hnhng (dynamic), ngha l bng t hc ng i v nidung t ng thay i theo s thay i ca tp mng.

Cc b nh tuyn cho php bn chia s mt a ch IP n c cung c p b inh cung c p dch v ISP (Internet Service Provider) v i nhiu my tnh trnmng thng qua c ch gi l B dch a ch mng NAT (Network AddressTranslation). NAT gip m bo an ninh cho bn trn Internet.

2.4.3 Thit b Wireless Router Modem:

Thit b Modem Router tch h p cng ngh khng dyng th i h tr tnhnng Modem ADSL 2+v i cng LAN Ethernet 10/100 Mbps cho tc k tni cao trong h thng mng c dy.

Hnh 2.5 Wireless Router Modem Linksys chu n N


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2.4.4 Cu ni khng dy WB (Wireless Bridge):

Wireless Bridge l mt thit b c s dng k t ni hai hoc nhiu phn

on mng (LAN hoc cc b phn ca mt mng LAN) v i nhau bng nhng phng thc vt l v logic khc nhau. V i WB ta c th k t ni hu nh btc thit b no c giao ti p cng Ethernet, chng hn mt my in mng vomng khng dy. Ta dng cp ni thit b vo cng Ethernet ca cu ni, vcu ni s truyn d liu t thit b ny n thit b khng dy. Lc ny, bnthn thit b hot ng chng khc g v i khi l p vo mng c dy.

Hnh 2.6 Wireless Bridge Linksys

Thit b cu ni khng dy lm vic theo c p (point-to-point), mt trn mi bn ca "cu ni". Tuy nhin, c th c nhiu ng th i "cu" s dng mtthit b trung tm (im n a im). Cu ni c th c thng qua WDS(Wireless Distribution System) to ra mt cu khng dy mc 2 gia haihoc nhiu im.

2.4.5 B chuyn i khng dy (Wireless Adapter) v Card mng khng dy(Wireless Card):

Thit b ny cn c gi l B iu h p mng khng dy hoc NIC (NetworkInterface Card), l thit b gn trn PC hay thit b cm tay nh Laptop,


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PDA,s dng mi trng l sng in t, cho php PC hay Laptop trao id liu c v i nhau thng qua sng v tuyn.

Chc nng ca Wireless card cng ging nh chc nng ca card mng c dyl truyn d liu gia cc my tr m khng dy v gia cc my tr m v i AP.Card mng khng dy giao ti p my tnh v i mng khng dy bng cch iuch tn hiu d liu v i chui tr i ph v thc hin mt giao thc truy nh pcmng sng mang.

Thit b c 3 chng loi tng ng v i cc kiu giao tip nh sau: - PC Card: Dng cho my tnh xch tay khi s dng khe cm PCMCIA.

Hnh 2.7 PC Card c a Asus v Planet

- Adapter Card: dng cho my tnh bn s dng khe cm PCI, ISA, EISA.

Hnh 2.8 Adapter Card TP-Link


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- Card l p r i bn ngoi, thng th ng loi ny k t ni v i my tnh thng quacng USB, COM,Parallel

Hnh 2.9 Wireless USB Card TP-Link


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- C th k t ni nhiu tr m AP v i nhau bng mng hu tuyn Ethernet hocmt knh khng dy khc to mt h thng phn phi DS (DistributionSystem).- Khi mt AP k t ni tr c tip n mt mng c dy v thit l p mt tr m truyc p khng dy, th cu hnh mng ny c gi l BSS.c th l AP k t nitr c ti p v i DSM (Distribute System Medium). Mt BSS ch c 1 AP v mthoc nhiu tr m. Mt BSS c mt SSID (Service Set Identification).- Mi tr m trong BSS lin lc v i cc tr m khc hay cc host trong mng cdy thng qua AP. Cc tr m khng th lin lc tr c ti p v i nhau m khng

thng qua AP. BSS to nn mt vng sng n hay khu vc RF, xung quanhim truy c p v i tc d liu thay i (vng trn ng tm) ty thuc votc d liu, c o bng Mbps. Tc d liu trong vng trn ng tms ph thuc vo k thut c s dng, tc nh nht khi cch xa AP nhiunht.

T p h p dch v m r ng ESS (Extended Service Set):- T p dch v m r ng c nh ngha nh hai hay nhiu t p dch v c bn

BSS c k t ni tr c ti p b i mt h thng phn phi chung DS. H thng phn phi c th l l c dy, khng dy, LAN, WAN hoc phng php khcca lin k t mng.- Mt ESS phi c t nht 2 AP hot ng mode infrastructure. Ging nhBSS, tt c cc gi trong mt ESS phi thng qua AP. Mt t p dch v m r ng (ESS) l mt t p h p nhiu AP v i s chng l p khu vc ph sng. Mcch ca che l p vng ph sng l chuyn vng lin tc cho cc client trongtr m. Hu ht cc h thng yu cu che l p l 20% t c lin tcchuyn vng. D s lin tc khi chuyn vng l kha cnh then cht trong thitk WLAN, nhng khng yu cu m bo khng ngt k t ni.- Trong tr ng h p mt tr m r i khi khu vc dch v c bn (BSS) ca APu tin s mt k t ni. Tr m s thit l p li k t ni ngay khi n di chuyn votrong khu vc AP th hai. Phng php linh ng gia cc vng c xem

nh s chuyn vng qua li (nomadic roaming). Tr ng h p cui cng, nhiu


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AP trong ESS trng l p hon ton nhau. K thut ESS 802.11 ny c gi lcng v tr (co-location). K thut ny nhm tng cng sut ca cc tm.- Tn ca mt ESS l ESSID. D v bn cht, mt ESSID ng b v i mtSSID, khng yu cu cc AP tham gia trong ESS chia s chnh xc cng tnmng. Cc AP chia s cng mt DSM c th khc SSID v vn han ton nhmt ESS.

Wired Network

ESS

DS

Hnh 3.2 M hnh DS v ESS

H thng phn phi DS (Distribution System):- Thnh phn kin trc dng k t ni cc nhm dch v v i nhau v tch h pv i cc mng LAN to

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