CÔNG NGHỆ WIMAX VÀ ỨNG DỤNG

7/24/2019 CNG NGH WIMAX V NG DNG

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I HC QUC GIA H NI

TRNG I HC CNG NGH

MNH HI

CNG NGH WIMAX V NG DNG

Ngnh:

Cng ngh in T-

Vin thng

Chuyn ngnh: K thut in t

M s: 60.52.70

LUN VN THC S

NGI HNG DN KHOA HC:TS. TRN MINH TUN

H Ni2009


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1

LI NI U

S ra i ca WiMAX/IEEE 802.16 khi u mt thi i mi ca truy nhp

khng dy bng rng. WiMAX/IEEE 802.16 cung cp truy nhp khng dy v di ngbng rng cho cc dch v da trn IP. N cho php chuyn giao gia cc mng c

cc cng ngh khc nhau ca cc nh qun l khc nhau v cung cp bng thng rng

trong cc vng xa xi.

Mc tiu ca n ny l nghin cu cc tiu chun 802.16 ca cng ngh

WiMAX trong tp trung ln WiMAX di ng. l nhng ni dung cn bn nht

ca cng ngh Wimax.

nbao gm 5 chng.Chng 1: Tng quan v h tiu chun IEEE 802.16 v WiMAX Forum.

Ni dung chng ny gii thiu v h tiu chun IEEE 802.16 gm 802.16c

nh ngha cc h s cho cc ng dng inhnh, 802.16a, bao gm cc tng cng

cho iu khin, a ra ch li v h tr cc tn s b sung.ng thi cc sa i

b sung ny a vo truyn dn trong di 2 GHz n 10 GHz, truyn dn khng trc

x v cc dch v cp php v min php. Sa i chnh c cng b vo nm 2004

dng tiu chun IEEE 802.16d hay IEEE 802.16-2004. Chun ny kt hp v hon

thin chun 802.16, sa i b sung 802.16c v IEE.16a. Mt b sung cho IEEE

802.16d c khi tho vi tn gi l 802.16e (hon thnh vo cui nm 2005)

WiMAX Forum nh ngha cc hs trn c s s dng cc ty chn kh dng

ca 802.16 cp pht chng nhn cho cc sn phm v nh ngha cc c ch b

sung cho vic kt ni mng

Chng 2: Giao din v tuyn cho cc h thng khng dy bng rng c

nh ca WiMAX.

Ni dung chng nytrnh by ton b phn giao din v tuyn ca Wimax c

nh.

Chng 3: Lp MAC ca WiMAX di ng.

Ni dung chng ny trnh by v lp MAC. Nhim v chnh ca lp MAC

(Medium Access Control) l qun l cc ti nguyn v tuyn ca giao din v tuyn

mt cch hiu qu.


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Chng 4: M hnh lp vt lca WiMAX di ng v cc tnh nng tin tin

ca n.

Ni dung chng ny trnh by v lp vt l ca Wimax, gm lp vt l

s dng:

n sng mang

OFDM

OFDMA

Chng 5: Mt s ng dng ca Wimax

Ni dung chng ny trnh by mt s ng dng c bn ca Wimax.

Ti xin c gi li cm n chn thnh n TS Trn Minh Tun gip

ti hon thnh n ny.


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3

MC LC

Chng 1

TNG QUAN H TIU CHUN IEEE 802.16 V WIMAX FORUM........................... 14

1.1. TNG QUAN H TIU CHUN IEEE 802.16 ............................................................. 14

1.2. WiMAX FORUM ........................................................................................................... 16

1.3. WiMAX DI NG ......................................................................................................... 17

1.4. L TRNH PHT TRIN SN PHM WiMAX ........................................................... 19

1.5. KT LUN .................................................................................................................... 20

Chng 2

GIAO DIN V TUYN CHO CC H THNG KHNG DY BNG RNG C

NH CA WIMAX ........................................................................................................... 21

2.1. M U ........................................................................................................................ 21

2.2. M HNH THAM KHO .............................................................................................. 21

2.3. TNG QUAN CC TNH NNG LP MAC ................................................................ 21

2.4. TNG QUAN CC TNH NNG LP VT L, PHY ................................................. 23

2.4.1. Bng tn ................................................................................................................... 23

2.4.1.1. Bngtn cp php 10-66 MHz ........................................................................... 232.4.1.2. Cc tn s thp hn 11 MHz .............................................................................. 23

2.4.1.3. Cc tn s min php di 11 MHz (ch yu l 5-6MHz) .................................. 23

2.4.2. K thut ghp song cng .......................................................................................... 23

2.4.2.1. Ghp song cng phn chia theo tn s, FDD ...................................................... 24

2.4.2.2. Ghp song cng phn chia theo thi gian, TDD ................................................. 24

2.5. CC TY CHN ........................................................................................................... 25

2.5.1. H thng anten thch ng, AAS ................................................................................ 25

2.5.2. M ha khng gian thi gian, STC ........................................................................... 282.5.3. Pht li t ng, ARQ .............................................................................................. 28

2.5.4. Cu hnh im a im v li ................................................................................. 28

2.6. TNG KT CC C T GIAO DIN V TUYN KHC NHAU TRONG IEEE

802.16e2005 CHO TRUY NHP C NH ...................................................................... 29

2.7. WIRELESSMAN OFDM ................................................................................................ 30

2.7.1. Tng quan cc tnh nng ca WirelessMAN OFDM ................................................. 30

2.7.2. Cu trc khung ......................................................................................................... 32

2.7.3. Cu trc lp vt l WirelessMAN OFDM ................................................................. 34

2.7.3.1. Cc thng s WirelessMAN OFDM................................................................... 34


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2.7.3.2. S khi my pht v my thu WirelessMAN OFDM ..................................... 35

2.7. 4. M t cc khi ......................................................................................................... 38

2.7.4.1. Ngu nhin ha, PBRS ...................................................................................... 38

2.7.4.2. Khi m ha knh .............................................................................................. 38

2.7.4.3. B an xen/ gii an xen .................................................................................... 402.7.4.4. iu ch/ gii iu ch ....................................................................................... 40

2.7.4.5. IFFT v FFT ...................................................................................................... 42

2.7.4.6. B c tnh knh vcn bng ............................................................................ 43

2.8. WirelessMAN OFDMA .................................................................................................. 45

2.8.1. M t k hiu OFDMA, cc thng s k hiu v tn hiu pht.................................. 45

2.8.2. Sp xp knh con v khe OFDMA ............................................................................ 47

2.8.3. n nh cc sng mang con OFDMA ....................................................................... 48

2.8.4. Sp xp knh con ng xung ................................................................................ 492.8.4.1. Cu trc k hiu cho FUSC ............................................................................... 49

2.8.4.2. Cu trc k hiu ng xung PUSC ................................................................. 50

2.8.4.3. Cu trc k hiu ng xung TUSC1 v TUSC2 ............................................. 52

2.8.5. Cu trc k hiu ng ln PUSC ............................................................................ 52

2.8.6. Khe OFDMA v vng s liu ................................................................................... 53

2.8.7. Sp xp s liu OFDMA ........................................................................................... 54

2.8.8. Cu trc khung PMP ................................................................................................ 57

2.9. TNG KT .................................................................................................................... 58

Chng 3

LP MAC CA WIMAX DI DNG .................................................................................. 60

3.1. M U ........................................................................................................................ 60

3.2. CU TRC LP MAC .................................................................................................. 61

3.3. LP CON PHN CHUNG CA MAC (MAC CPS) ...................................................... 63

3.3.1. Khun dng MACPDU............................................................................................. 63

3.3.2. Cc dch v MAC ..................................................................................................... 653.3.2.1. H tr cht lng dch v (QOS) ....................................................................... 65

3.3.2.2. Dch v lp biu MAC ....................................................................................... 67

3.3.2.3. C ch yu cu v n nh bng thng ............................................................... 69

3.3.3. Qun l cng sut v di ng .................................................................................... 71

3.3.3.1. Qun l cng sut .............................................................................................. 71

3.3.3.2. Chuyn giao....................................................................................................... 71

3.3.4. An ninh .................................................................................................................... 73

3.4. TNG KT .................................................................................................................... 74


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Chng 4

M HNH LP VT L V CC TNH NNG TIN TIN CA WIMAX DI DNG 76

4.1. M U ........................................................................................................................ 76

4.2. OFDMA KH NH C................................................................................................ 784.3. CU TRC K HIU OFDM........................................................................................ 81

4.4. SP XP KNH CON.................................................................................................... 81

4.4.1. Sp xp knh con s dng ton b ng xung (FUSC: Down Link Fully Used

Channelization) .................................................................................................................. 83

4.4.2. Sp xp knh con s dng mt phn (PUSC: Partially Used Subchannelization)....... 84

4.4.3. Sp xp AMC ........................................................................................................... 85

4.5. IU CH V M HA ............................................................................................... 86

4.6. CC CNG NGH ANTEN THNG MINH................................................................. 89

4.7. CU TRC KHUNG TDD............................................................................................. 92

4.8. CC TNH NNG TNG CNG KHC CA LP VT L ................................... 96

4.9. CC TNH NNG TIN TIN CA WiMAX .............................................................. 96

4.9.1. Ti s dng tn s mt phn ..................................................................................... 96

4.9.2. Dch v a phng v qung b (MBS) .................................................................... 98

4.10. QU NG TRUYN CA H THNG WiMAX DI NG................................ 99

4.10.1. Cc thng s ca h thng WiMAX di ng ........................................................... 99

4.10.2. Qu ng truyn WiMAX .................................................................................. 102

4.11. THNG TIN B SUNG V TIN CY MAP CA WiMAX DI NG............. 1064.12. PH TN CA WiMAX ........................................................................................... 108

4.13. TNG KT................................................................................................................. 109

Chng 5

NG DNG CA WIMAX........................................................................................... 110

5.1 GII THIU .................................................................................................................. 110

5.1.1 ng dng cho mng khng dy ............................................................................... 110

5.1.2 ng dng trong y hc .............................................................................................. 111

5.1.3 H thng bo mt .................................................................................................... 111

5.1.4 Kt ni mng ngn hng .......................................................................................... 112

5.1.5 VoIP ........................................................................................................................ 113

5.1.6 Truy nhp ti nh .................................................................................................... 114

5.1.7 Kt lun ................................................................................................................... 116


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DANH MC HNH V

Hnh 1.1. Cu hnh topo ca WMAN ................................................................................. 14

Hnh 1.2. L trnh pht trin cng ngh WiMAX ............................................................... 20

Hnh 2.1. M hnh tham kho ngn xp giao thc ca 802.16. ............................................ 22Hnh 2.3. Cu trc khung TDD........................................................................................... 25

Hnh 2.4. Vng AAS, FDD ................................................................................................ 26

Hnh 2.5. Vng AAS, TDD ................................................................................................ 27

Hnh 2.6. Nguyn l STC. .................................................................................................. 28

Hnh 2.7. iu ch thch ng trong lp vt l ..................................................................... 32

Hnh 2.8. Cu trc khung OFDM ng xung .................................................................. 33

Hnh 2.9. Cu trc khung OFDM ng ln ....................................................................... 34

Hnh 2.10. Tin t di ng xung ................................................................................... 34

Hnh 2.11. S khi my pht v my thu WirelessMAN OFDM .................................... 36

Hnh 2.12. S khi bng gc ca my pht v my thu WirelessMAN OFDM .............. 37

Hnh 2.13. B ngu nhin ha ............................................................................................ 38

Hnh 2.14. B m ha xon ................................................................................................ 39

Hnh 2.15. Cc chm tn hiu iu ch BPSK, QPSK, 16QAM, 64QAM ........................... 42

Hnh 2.16. Cu trc thi gian ca k hiu OFDM ............................................................... 46

Hnh 2.17. M t min tn s OFDMA (ba knh) ............................................................... 47

Hnh 2.18. Cu trc truyn dn c s ng xung ............................................................ 49

Hnh 2.19. Cu trc k hiu ng xung cho on 0 trn k hiu s 1 s dng FUSC...... 50

Hnh 2.20. Cu trc cm .................................................................................................... 51

Hnh 2.21. M t lt ng ln ........................................................................................... 53

Hnh 2.22. Th d v vng s liu trong n nh OFDM ..................................................... 54

Hnh 2.23. Th d v sp xp cc khe OFDMA vo cc knh con v cc k hiu trn ng

xung (trong ch PUSC)................................................................................................ 55

Hnh 2.24. Th d v sp xp cc khe OFDMA vo cc knh con v cc k hiu cho ng

ln ...................................................................................................................................... 56

Hnh 2.25. Th d v cu trc khung theo thi gian TDD (vng bt buc).......................... 58Hnh 2.26. Khung OFDM c nhiu vng. ........................................................................... 58

Hnh 3.1. Ch PMP trong cc mng 802.16 ................................................................... 60

Hnh 3.2. Ch mng 802.16 h hp ............................................................................... 61

Hnh 3.3. Cu trc lp MAC ca WiMAX ......................................................................... 62

Hnh 3.4. Khun dng MACPDU ....................................................................................... 64

Hnh 3.5. Htr QoS ca WiMAX di ng ........................................................................ 66

Hnh 3.6. Qu trnh chuyn giao ......................................................................................... 73

Hnh 4.1. Cu trc lp vt l ca S-OFDMA ca WiMAX ................................................. 80Hnh 4.2. Cu trc sng mang con OFDMA ....................................................................... 81


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Hnh 4.3 Cu hnh sng mang con cho 1024-FFT OFDMA DL FUSC ............................... 83

Hnh 4.4. Cc cu trc DL PUSC v UL PUSC .................................................................. 85

Hnh 4.5. Cc cu hnh knh con c t chc theo BIN trong AMC................................. 86

Hnh 4.6. Chuyn mch thch ng cho cc ch MIMO ................................................... 91

Hnh 4.7. Cu trc khung OFDMA TDD (ch cho vng bt buc)...................................... 93Hnh 4.8. Cu trc khung a vng ...................................................................................... 97

Hnh 4.9. Ti s dng tn s mt phn ............................................................................... 98

Hnh 4.10. H tr MBS nhng bng cc vng MBS ........................................................... 99

Hnh 4.11. Kt qu m phng hiu nng knh iu khin cho knh m hnh truyn sng TU

(thnh ph in hnh) [7,8] ............................................................................................... 107

Hnh 4.12. Cm MAP con. ............................................................................................... 107

Hnh 5.1 Kin trc mng di ng s dng T1 nh l lung truyn dn gia cc MSC. ...... 110

Hnh 5.2 ng dng y t .................................................................................................... 111Hnh 5.3 Kin trc Wimax cho ng dng bo mt ............................................................ 112

Hnh 5.4 Kin trc Wimax cho hot ng gim st. .......................................................... 112

Hnh 5.5 Kt ni Wimax cho h thng ngn hng ............................................................. 113

Hnh 5.6 Kin trc h thng VoIP n gin ...................................................................... 114

Hnh 5.7 Mch vng ni ht trong mng PSTN ................................................................ 115


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DANH MC BNG

Bng 1.2. Cc loi ng dng cho h thng da trn 802.16e ............................................... 18

Bng 2.1. Cc c t giao din v tuyn ............................................................................. 29

Bng 2.2. Cc tnh nng ca WirelessMAN OFDM............................................................ 31

Bng 2.3 Cc thng s chnh WirelessMAN OFDM ........................................................... 35

Bng 2.4. Th d v t knh cho cc bng cp php .......................................................... 45

Bng 2.5. Cc thng s ca mt k hiu ............................................................................. 49

Bng 2.6. n nh sng mang con ng xung OFDM-PUSC.......................................... 50

Bng 2.7. Cc thng s ca mt k hiu ............................................................................. 52Bng 3.1. Cc trng trong tiu MAC PDU ................................................................... 64

Bng 3.2. QoS v cc ng dng ca WiMAX ..................................................................... 66

Bng 3.3. Cc ty chn lp biu dch v ............................................................................. 68

Bng 4.1. Cc ng dng ca WiMAX ................................................................................ 77

Bng 4.2. Cc thng s cu S-OFDMA .............................................................................. 79

Bng 4.3. Cc cu hnh knh FUSC c s.......................................................................... 83

Bng 4.4. Cc dng iu ch v m ha c s dng lp vt l..................................... 87

Bng 4.5. Tc s liu vt l cho cc knh con PUSC ..................................................... 87Bng 4.6. Cc tnh nng ty chn anten tin tin ................................................................ 90

Bng 4.7. Cc tc s liu cho cc cu hnh SIMO/MIMO khc nhau (cho knh 10 MHz,

khung 5ms, knh con PUSC, 44 k hiu OFDM s liu) .................................................... 91

Bng 4.8. Cc thng s h thng WiMAX di ng ........................................................... 101

Bng 4.9. Cc thng s OFDMA ...................................................................................... 101

Bng 4.10. M hnh truyn sng ....................................................................................... 102

Bng 4.11. Qu ng truyn DL cho Mibile WiMAX .................................................... 103

Bng 4.12. Qu ng truyn UL cho WiMAX di ng ................................................... 104


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THUT NG V T VIT TT

A

A AS Adaptive Atenna System H thng anten thch ng

ACK Acknowledge Cng nhn

AES Advanced Encryption Standard Chun mt m tin tin

AG Absolute Grant Cho php tuyt i

AMC Adaptive Modulation and Codding iu ch v m ho thch ng

A-MIMO Adaptive Multiple Input MultipleOutput

a u vo a u ra thch ng

AMS Adaptive MIMO Switching Chuyn mch MIMO thch ng

ARQ Automatic Repeat reQuest Yu cu pht lp t ng

ASP Application Service Network Mng dch v ng dng

B

BE Best Effort N lc nht

BRAN Broadband Radio Access Network Mng truy nhp v tuyn bng rng

C

CCI Co-Channel Interference Nhiu ng knh

CINR Carrier to Interference +Noise Ratio T s sng mang trn nhiu cng tp

m

CP Cyclic Prefix Tin t chu trnh

CQI Channel Quality Indicator Ch th cht lng knh

CSN Connectivity Service Network Mng dch v kt ni

CSTD Cyclic Shift Transmit Diversity Phn tp pht dch tun hon

CTC Convolutional Turbo Code M turbo xon

D

DL Downlink ng xung

DOCSIS Data Over Cable Service Interface c t giao din dch v d liu qua


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Specification cp

DSL Digital Subcriber Line ng thu bao s

DVB Digital Video Broadcast Qung b video s

E

EAP Extensible Authentication Protocol Giao thc nhn thc kh

m rng

EIRP Equivalent Isotropic Radiated Power Cng sut bc x ng hng tng

ng

F

FBSS Fast Base Station Switching Chuyn mch trm gc nhanh

FCH Frame Control Header Tiu iu khin khung

FDD Frequency Division Duplex Ghp song cng phn chia theo tn

s

FFT Fast Fourier Transform Bin i Fourier nhanh

FUSC Fully Used Sub-Channel Knh con s dng ton b

G

GKEK Group Key Encryption Key Kha mt m ca kha nhm

GMH Generic MAC Header Tiu MAC chung

GTEK Group Traffic Encryption Key Kha mt m lu lng nhm

H

HARQ Hybrid Automatic Repeat reQuest Yu cu pht li t ng ai ghp

HiperMAN High Performance Metropolitan

Area Network

Mng vng th hiu nng cao

HO Hand-off Chuyn giao

HTTP Hyper Text Transfer Protocol Giao thc truyn siu vn bn

I

IE Information Element Phn t thng tin

IETF Internet Engineering Task Force Lc lng c trch k thut Internet

IFFT Inverse Fast Fourier Transform Bin i Fourier nhanh ngc

IR Incremental Redundancy Tch lu tng dn


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ISI Inter-Symbol Interference Nhiu gia cc k hiu

L

LDPC Low-Density-Parity-Check Kim tra chn l mt thp

LOS Line of Sight Trc x (Tm nhn thng)

M

MAC Media Access Control iu khin truy nhp mi trng

MAI Multiple Access Interference Nhiu a truy nhp

MAN Metropolitan Area Network Mng vng th

MBS Multicast and Broadcast Service Dch v a phng v qung b

MDHO Macro Diversity Hand Over Chuyn giao phn tp v mMIMO Multiple Input Multiple Output a u vo a u ra

MMS Multimedia Message Service Dch v bn tin a phng tin

MPLS Multi-Protocol Label Switching Chuyn mch nhn a giao thc

MS Mobile Station Trm di ng

N

NACK Not Acknowledge Khng cng nhn nhnNAP Network Access Provider Nh cung cp truy nhp mng

NLOS Non Line of Sight Khng trc x (Tm nhn khng

thng)

NRM Network Reference Model M hnh tham kho mng

nrtPS Non-Real-Time Polling Service Dch v tham d phi thi gian thc

NSP Network Service Provider Nh cung cp dch v mng

O

OFDM Orthogonal Frequency Division

Multiplex

Ghp knh phn chia theo tn s

trc giao

OFDMA Orthogonal Frequency Division

Multiplex Access

a truy nhp phn chia theo tn s

trc giao

P

PER Packet Error Rate T l li gi


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PKM Public Key Management Qun l kho cng cng

PUSC Partially Used Sub-Channel Knh con s dng mt phn

Q

QAM Quadrature Amplitude Modulation iu ch bin vung gc

QoS Quality of Service Cht lng dch v

QPSK Quadrature Phase Shift Keying Kho dch pha vung gc

R

RG Relative Grant Cho php tng i

RTG Receiver/Transmit Transition Gap Khong trng chuyn thu sang

pht

rtPS Real-time Polling Service Dch v thm d thi gian thc

S

SDMA Space Division Multiple Access a truy nhp phn chia theo khng

gian

SF Spreading Factor H s tri ph

SFN Single Frequency Network Mng tn s n

SGSN Serving GPRS Support Node Node h tr dch v GPRS

SHO Soft Hand-Off Chuyn giao mm

SIM Subscriber Indentify Module Phn nhn dng thu bao

SIMO Single Input Multiple Output Mt u vo nhiu u ra

SNIR Signal to Noise+Interference Ratio T s tn hiu trn nhiu+tp m

SLA Service Level Agreement Tho thun mc dch v

SM Spatial Multiplexing Ghp knh khng gian

SMS Short Message Service Dch v bn tin ngn

SNR Signal to Noise Ratio T s tn hiu trn tp m

S-OFDMA Scalable Orthogonal Frequency

Division Multiplex Access

a truy nhp phn chia theo tn s

trc giao kh nh c

SS Subscriber Station Trm thu bao

SSRTG SS Receive /Transmit Transit Gap Khong thi gian chuyn i


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SSTRG SS Transmit/Receive Transit Gap Khong thi gian chuyn i mt

sang thu ca SS

STC SpaceTime Coding M ho thi gian khng gian

TTDD Time Division Duplex Ghp song cng phn chia theo thi

gian

TEK Traffic Encription Key Kho mt m lu lng

TTG Transmit/receive Transition Gap Khong trng chuyn pht sang thu

TTI Transmission Time Interval Khong thi gian truyn dn

TU Typical Urban Thnh ph in hnh

U

UE User Equipment Thit b ngi s dng

UGS Unsolicited Grant Service Dch v cho php khng khn ni

UL Uplink ng ln

UMTS Universal Mobile Telephone System H thng vin thng di ng ton

cu

V

VoIP Voice over Internet Protocol Thoi qua giao thc IP

W

WiFi Wireless Fideliry

WAP Wireless Application Protocol Giao thc ng dng khng dy

WiBro Wireless Broadband Khng dy bng rng

WiMAX Worldwide Interoperability forMicrowave Access Kh nng tng hp ton cu ivi truy nhp vi ba


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Chng 1

TNG QUAN H TIU CHUN IEEE 802.16 V WIMAX FORUM

1.1. TNG QUAN H TIU CHUN IEEE 802.16

H tiu chun IEEE 802.16 (giao din v tuyn mng vng th khng dy)

cho truy nhp bng rng (BWA: Broadband Wireless Access) cung cp cng ngh truy

nhp "km cui cng" cho cc im nng vidch v s liu, video, v thoi tc

cao. u im ni bt nht ca BWA l gi thnh lp t v bo dng thp so vi truy

nhp mng cp ng v cp quang nht l i vi vng xa xi ni kh lp t mngtruy nhp hu tuyn. BWA c th m rng mng cp quang v cung cp dung lng

cao hn mng cp ng hay ng dy thu bao s (DSL: Digital Subsscriber Line).

Mng khng dy ny c lp t rt nhanh bng cch t trm gc (BS: Base Station)

trn ta nh cao tng hoc trn cc ct to nn h thng truy nhp khng dy tc

cao. Hnh 1.1 cho thy cu hnh ca mng WMAN.

Trm gcVn phng

nh

Bit th

B lp

Trm gcCng xng

Mngli

Chung

c

Hnh 1.1. Cu hnh topo ca WMAN

Thnh vin u tin ca h BWA l chun IEEE 802.16. Chun ny c d

tho u tin vo 12/2001 v phin bn cui cng c cng b 8/ 4/2002. Bng tn


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cng tc ca chun ny l 10-66 GHz, vi truyn sng trc x. Cu hnh topo ca

chun ny da trn mng im a im trong lu lng c truyn gia mt trm

gc BS (Base Station) v nhiu trm thu bao SS (Subscriber Station). Tiu chun

IEEE 802.16 c cng b vo 9/2001, vi tiu "ng tn ti vi cc h thng truy

nhp bng rng khng dy c nh" cng bao ph 10-66GHz. Tiu chun 802.16.c

"Cc h s chi tit cho 10-66 GHz" c d tho u tin vo 24/5/2002 v phin bn

cui cng c pht hnh vo 15/1/2003.

Vic sa i b sung ny cp nht v m m rng iu khon 12 ca tiu

chun IEEE 802.16 2001 lin quan n h s v tp tnh nng v chc nng p dng

cho cc trng hp thc hin trin khai in hnh. Tuy nhin, do BWA ngy cng

c s dng nhiu cho cc vng dn c, nn truyn trc x khng con thch hp do

a hnh v cy ci. Ngoi ra, nhiu a ng truyn v gi thnh lp t anten ngoitri cao. V th, cn sa i b sung cho chun 802.16 hin hu. y l l do ra i

tiu chun 802.16a c ban hnh vo 1/4/2003. Chun ny bao hm sa i lp

MAC (Media Access Control) v nhiu c t lp vt l cho c bng tn cp php v

min php. Mt sa i ng k ca lp MAC l cc ch li ty chn. im khc

bit gia ch im a im (PMP) v li l: trong ch PMP lu lng ch xy

ra gia BS v cc SS, cn trong ch li lu lng c th nh tuyn qua cc SS

khc v c th trc tip gia cc SS. u im ca ch ny l hot ng vn c

m bo ngay c khi c chng ngi ln nh ni i chn ng truyn trc x gia

SS v BS. Cc SS b chn ny c th kt ni gin tip n BS thng qua cc SS khc.

Mt thay i ng k na ca lp MAC l h tr nhiu c t lp vt l, trong mi

ct ph hp cho mt mi trng khai thc c th. Trong chun 802.16a ba cu trc

lp vt l (PHY) c nh ngha: SC (Single Carrier: n sng mang), 256-OFDM v

2048-OFDMA.

Chun IEEE 802.16-2004 c cng b vo nm 2004 hp nht v sa i

cc chun 802.16- 2001, 802.16c v 802.16a thnh b chun chung. Trong 802.16-2001 cho hot ng trong di tn t 10- 66 GHz trc x trc y c tn mi trong

chun ny l WirelessMAN 802.16-SC, cn 802.16a cho bng tn di 11 GHz khng

trc x c ba ch lp vt l vi ba tn mi sau y: WirelessMAN 802.16-SCa,

WirelessMAN 802.16-OFDM v WirelessMAN 802.16-OFDMA.

C 802.16 v 802.16a u c s dng cho truy nhp khng dy bng rng c

nh. Trn c s chun 802.16a, nhm cng tc IEEE 802.16e xy dng chun

802.16e gm "cc lp vt l v MAC cho khai thc c nh v di ng trong bng tncp php". Trong chun ny tnh di ng c b sung cho SS trc y ch h tr kt


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ni mng c nh trong cc bng tn t 2 n 6GHz. Bng 1.1 so snh cc tnh nng

ca cc chun 802.16, 802.16a v 802.16e.

Bng 1.1. So snh cc chun IEEE 802.16, 16a, 16e

802.16 802.16a 802.16e

Ngy hon

thnh8/2002 4/2003 2006

Bng tn 10-66GHz 2-11GHz 2-6GHz

iu kin knh LOS NLOS NLOS

iu ch QPSK, 16QAM,64QAM

OFDM 256 sngmang, BPSK,

QPSK, 16QAM,

64QAM

OFDMA kh nh c,BPSK, QPSK, 16-QAM,

64QAM

Tnh di ng C nh C nh Di ri, xch tay, di ng

Bng thng

knh20, 25, 28MHz kh nh c t

1,75 n 20 MHz

Kh nh c: 1,25; 5;

10; 20 MHz

Bn knh in

hnh2-5 km 7-40 km 2-5 km

Chun IEEE cho mng LAN v MAN, phn 16: Giao din v tuyn cho h

thng truy nhp khng dy bng rng c nh v di ng a ra sa i b sung

cho IEEE 802.16-2004 v IEEE 802.16.2005.

1.2. WiMAX FORUM

Chun IEEE 802.16 c pht trin nhiu nm vi s tham gia ca nhiunh cng nghip. Tuy nhin, chun ny qu rng v vic hp chun IEEE 802.16 cha

m bo c thit b ca mt nh cung cp s tng hp vi thit b ca nh cung

cp khc. WiMAX Forum, t chc phi li nhun bao gm trn 350 thnh vin, tip

nhn cng vic m IEEE li. Trong s cc thnh vin ca WiMAX Forum c nh

cung cp dch v, nh cung cp thit b, nh sn xut bn dn v thit b. WiMAX

cng cng tc vi HiperMAN, nhm cng tc trong trong y ban k thut ca ETSI

BRAN. Vic hp tc ny dn n s hi ha hon ton gia ETSI HiperMAN v IEEE

802.16, c th hin ti liu b sung 802.16e v cc chun tng tc: PHY (TS 102


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17

177v.1.6.1) v DLC (TS 102.178v.1.6.1). Hot ng khi tho ca cc tiu chun o

kim c dng trong qu trnh kim tra ca WiMAX Forum c thc hin vi s

cng tc cht ch ca ETSI BRAN HiperMAN, nhm cng tc WiMAX Forum v

nhm cng tc chng nhn WiMAX Forum. Vi nhiu thnh vin khc nhau, i din

ton th gii v s cng tc ca ETSI, WiMAX Forum sn sng c v vic tip

nhn ton cu v hi ha gii php v tuyn bng rng c chun ha da trn chun

v tuyn IEEE 802.16 m bo c tnh tng tc. t c mc ch ny, Forum

nh ngha hiu nng h thng v h s chng nhn bao gm tp con chun IEEE

802.16 vi tnh nng bt buc v ty chn cng vi mt b o kim tnh tng tc v

hp chun kim tra thit b v m bo tnh tng tc ca nhiu nh cung cp. V

th nhn chng nhn WiMAX m bo c s hp chun WiMAX 802.16 ln tnh

tng tc. Cc phng tin o kim cp chng nhn u tin c thit lp tiCetecom Labs Malaga, Ty Ban Nha thng 7 nm 2005 v cc sn phm c cp

chng nhn WiMAX trn chun 802.16-2004 bt u xut hin trn th trng. Cc

phng tin cp chng nhn b sung cng s c thit lp to iu kin cho

qu trnh cp chng nhn v p ng cc yu cu b sung cho qu trnh o kim cp

chng nhn cho 802.16e cho ng dng di ng. Cc nhm cng tc cp chng nhn v

k thut ca WiMAX Forum ang nghin cu cp chng nhn sn phm WiMAX

di ng s bt u a ra vo qu 4 nm 2006 n gia nm 2007. K vng rng s c

nhiu s tham gia ca cc thnh vin h thng, cc i tc v nhu cu v cc sn phm802.16e stng, gi thnh trn mt thu bao s gim trong 2 -3 nm tip theo.

1.3. WiMAX DI NG

WiMAX di ng c xy dng trn chun IEEE 802.16e l mt gii php

khng dy bng rng cho php hi t mng di ng v c nh thng qua mt cng

ngh v tuyn bng rng vng rng chung v kin trc mng linh hot. Giao din v

tuyn ca WiMAX di ng tip nhn a truy nhp phn chia theo tn s trc giao

(OFDMA) ci thin hiu nng cho mi trng truyn dn khng trc x. S-

OFDMA (OFDMA kh nh c) c a vo 802.16e h tr bng thng kh nh

c t 1,25 n 20 MHz. Nhm k thut di ng (MTG) trong WiMAX Forum pht

trin h s h thng WiMAX di dng nh ngha tnh nng bt buc v ty chn

ca chun IEEE. Cc tnh nng ny cn thit xy dng giao din v tuyn hp

chun vi chng nhn ca WiMAX Forum. H s h thng WiMAX di ng cho php

lp cu hnh h thng di ng da trn tp tnh nng c s chung m bo hot

ng tng hp cho thit b u cui v trm gc. Mt s phn t ca h s trm gcc c t ty chn m bo tnh linh hot khi trin khai trong cc trng hp c


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bit i hi cu hnh khc (chng hn nh ti u ha dung lng hoc vng ph). Pht

hnh 1 ca h s WiMAX di ng s bao ph cc bng thng 5; 7; 8.75; 10 MHz cho

cc n nh ph tn trong cc bng cp php: 2,3 GHz; 2,5 GHz; 3,3 GHz v 3,5 GHz.

WiMAX Forum nh ngha mt s ng dng cho h thng s dng 802.16ev nghin cu m hnh lu lng v ng dng cho chng, chng Cc ng dng ny

c chia thnh nm loi,chng c tng kt trong bng 1.2 di y cng vi cc

thng s tr v jitter m bo cht lng ngi s dng.

Bng 1.2. Cc loi ng dng cho h thng da trn 802.16e

Loi ng dng Bng thng Tr Jiiter

1 Tr chi tngtc a lp Thp 50 kbps Thp


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tr tc s liu nh ng xung ln n 63 Mbps trn on v tc s

liu nh ng ln ln n 28 Mbps trn on trong knh 10 MHz

2. Cht lng dch v (QoS): im cn bn ca kin trc IEEE 802.16 MAC l

QoS. N nh ngha cc lung dch v nhm sp t chng ln cc im mDiffServ hoc ccnhn MPLS truyn IP u cui u cui theo QoS. Ngoi

ra vic phn chia knh con v s bo hiu da trn MAP cng to ra c ch

linh hot lp biu ti u ti nguyn khng gian, tn s v thi gian trn giao

din v tuyn theo tng khung.

3. Kh nhc: Vic phn b ti nguyn tn s cho thng tin khng dy bng

rng rt khc nhau. V th cng ngh WiMAX di ng phi c thit k c

th nh c theo cc knh khc nhau c bng thng t 1,25 MHz n 20 MHz.

4. An ninh: WiMAX di ng s m bo tnh nng an ninh tt nht vi: nhn

thc da trn EAP (Extensible Authentication Protocol: giao thc nhn thc

kh m rng), mt m ha vi nhn thc da trn AES-CCM, CMAC v

HMAC da trn s bo v bn tin iu khin. H tr tp chng nhn ngi

s dng khc nhau bao gm: SIM/USIM, th thng minh, chng nhn s v cc

s tn ngi s dng/ mt khu da trn c phng php EAP cho kiu

chng nhn

5.

Di ng: WiMAX di ng h tr s chuyn giao ti u vi tr thp hn 50

ms m bo ng dng thi gian thc nh VoIP. Cc s qun l kha linh

hot m bo an ninh trong qu trnh chuyn giao.

1.4. L TRNH PHT TRIN SN PHM WiMAX

Phng th nghim kim nh cp chng nhn cho cc h thng WiMAX c nh

c thit lp ti ti Cetecoms Labs ti Malaga, Ty Ban Nha vo thng 7 nm

2005 v hin nay sn phm hp chun WiMAX cho dch v c nh kh dng v c trin khai trong bng 3,5 GHz (bng tn cp php) v 5,8GHz (bng tn khng

cn cp php). Phng th nghim cp chng nhn th hai, TTA c thit lp ti

Hn Quc. C hai phng th nghim cp chng nhn theo chun ca pht hnh 1

WiMAX di ng vo qu ba nm 2006 nhm trin khai sn phm c chng nhn

WiMAX di ng vo cui nm 2006.

WiMAX di ng thng xuyn xem xt cc h s chun hiu nng WiMAX di

ng b sung da trn kh nng ca th trng. Cc chun ny cp cc bng tn

khc nhau, cc bng thng knh v cc gii php FDD ph hp vi yu cu lut a


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phng trong th trng c chn. Hnh 1.2 cho thy l trnh pht trin sn phm

chun WiMAX.

802.16-2004

Cc ng dng c nhn sng mang trc x10-66MHz; OFDM bngcp php 2-11MHzkhng trc x,bngcp php v min php

Cc h sWiMAX

Kim tra cpchng nhn

OFDM

3,5 GHz

5,8 GHz

Cc h sWiMAX

Kim tra cpchng nhn

2,3 GHz

2,5 GHz

3,5 GHz

Trin khai cc dch v di ng theochun WiMAX di ng/802.16e

Cc h s pht hnh 1

Cc h s WiMAX di dng khc:Bng tn, bng thng knh, FDD....(ty theo th trngv c hi)

802.16e

Cc ng dng di ngv c nh; SOFDMA


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21

Chng 2

GIAO DIN V TUYN CHO CC H THNGKHNG DY

BNG RNG C NH CA WIMAX

2.1. M U

IEEE 802.16-2004 c t giao din v tuyn cho cc h thng truy nhp khng

dy bng rng (BWA) h tr cc dch v a phng tin cho mng vng. Lp MAC

trc ht h tr kin trc im a im cng vi cu hnh topo li ty chn. MAC

c cu trc h tr nhiu dng lp vt l, trong mi dng lp vt l ph hp

cho mt mi trng c th. i vi cc tn s trong trong di tn t 10 -66 GHz,

m bo truyn sng trc x lp vt l WirelessMAN-SC PHY (iu ch n sng

mang) c c t. i vi cc tn s trong di tn thp hn 11 GHz, m bo

truyn sng khng trc x (NLOS), ba lp vt l c c t: WirelessMAN -OFDM,

WirelessMAN- OFDMA v WirelessMAN -SCa (iu ch n sng mang). Chun

ny sa i v thng nht cc chun IEEE-802.16-2001, IEEE-802.16a-2003 v IEEE

802.16c-2002. Chun IEEE 802.16 e-2005 sa i v b sung cc chun trc v

bao hm c cc dch v truy nhp khng dy c nh v di ng. WiMAX ch cpn cc dch v truy nhp khng dy dc trn WirelessMAN-OFDM, WirelessMAN-

OFDMA. Trong phn ny ta s xt cc giao din v tuyn cho truy nhp khng dy c

nh cu WiMAX

2.2. M HNH THAM KHO

Hnh 2.1 cho thy m hnh tham kho giao din v tuyn ca chun IEEE

802.16e-2005

2.3. TNG QUAN CC TNH NNG LP MAC

MAC bao gm ba lp con: (i)lp con hi t c th dch v (CS: Convergence

Sublayer); (ii) lp con phn chung ca MAC (MAC CPS); (iii) lp con an ninh.

Lp con hi t c th dch v (CS) : m bo chuyn i cc s liu nhn t

mng ngoi qua im truy nhp dch v CS (CS SAP) vo cc MAC SDU (n v s

liu dch v MAC) v cung cp chng cho lp con phn chung ca MAC qua im

truy nhp dch v MAC(MAC SAP). MAC SDU gm: cc n v s liu dch v(SDU) t mng ngoi, nhn dng lung dch v (SFID: Service Flow Identifier) MAC


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v nhn dng kt ni (CID: Connection Identifier). N c th c c chc nng nn tiu

ti tin (PHS: Payload Header Supression). Nhiu c t CS c a ra cho

php giao tip vi cc giao thc khc nhau. Khun dng bn trong ca ti tin CS l

duy nht i vi CS v MAC CPS khng cn bit khun dng ny hay bt k thng tin

no v ti trng CS.

Lpvtl(PHY)

Lpconanninh

LpconphnchungcaMACMACCPS

Lpconhitcthdchv(CS)

CSSAP

MACSAP

PHYSAP

Thcthqunl

Cclpconhitcthdchv

Thcthqunl

LpconphnchungcaMAC

Thcthqunl

PHY

Lpconanninh

M

P

Ht

hngq

unl

m

ng

Phmvicatiuchun

Mtphngsliu/iukhin Mtphngqunl

Khiu:

SAP:ServiceAccessPoint:imtruynhpdchvMAC:MediumAccessControl:iukhintruynhpmitrngCS:ConvergenceSublayer:lpconhitCPS:CommonPartSublayer:lpconphnchungPHY:Physical:lpvtl

Hnh 2.1. M hnh tham kho ngn xp giao thc ca 802.16.Lp con MAC CPS: cung cp chc nng MAC li ca h thng truy nhp nh:

cp pht bng thng, thit lp kt ni v duy tr kt ni. N nhn s liu t cc CS

khc nhau thng qua MAC SAP (c phn loi cho tng kt ni c th). p dng

QoS cho truyn dn v lp biu s liu a n lp vt l.

Lp con an ninh:MAC cng cha mt lp con an ninh ring m bo nhn

thc, trao i kha v mt m.


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2.4. TNG QUAN CC TNH NNG LP VT L, PHY

2.4.1. Bng tn

2.4.1.1. Bng tn cp php 10-66 MHz

Bng tn 10-66 MHz c s dng cho mi trng vt l, trong do bc

sng ngn, nn ch s dng ng truyn trc x (LOS), cn cc ng truyn phn

x v tn x (NLOS) khng ng k. Trong bng tn ny, bng thng c s dng

thng l 25 hay 28 MHz. Vi tc bit th ln hn 10Mbps, mi trng ny rt

thch hp cho truy nhp im a im (PMP) phc v cc ng dng khc nhau t

cc ng dng vn phng nh hoc vn phng ti nh (SOHO: Small Office/Home

Office) n cc ng dng vn phng ln v trung bnh. Trong bng tn ny giao dinv tuyn iu ch n sng mang c c t trong chun giao din v tuyn

"WirelessMAN-SC".

2.4.1.2. Cc tn s thp hn 11 MHz

Cc tn s thp hn 11 MHz c s dng trong mi trng vt l, trong do

bc sng di, nn LOS khng ng k v ch yu l NLOS. c th h tr cc

trng hp cn trc x v khng trc x (NLOS), lp vt l phi c chc nng b sung

nh: cc k thut qun l cng sut tin tin, loi b nhiu, hoc ng tn ti nhiu v

a anten.

Ti y mt s tnh nng c b sung cho MAC nh: cu hnh li v yu cu

t ng pht li (ARQ: Automatic Repeat Request).

2.4.1.3. Cc tn s min php di 11 MHz (ch yu l 5-6MHz)

Mi trng vt l cc bng tn min php di 11 MHz tng t nh mi

trng cho cc bng tn min php trong di tn ny. Tuy nhin bn cht ca min

php l gy thm nhiu v cc vn ng tn ti, ng thi cc quy nh cng hn

ch cng sut c php pht x. Ngoi cc tnh nng nh trnh by trong 2.2.2, lp

PHY v MAC trong trng hp ny cn c thm tnh nng chn tn s ng (DFS:

Dynamic Frequency Selection) pht hin v trnh li.

2.4.2. K thut ghp song cng


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Giao thc MAC h tr mt s k thut ghp song cng cho PHY. Vic la

chn k thut ghp song cng nh hng ln mt s thng s PHY cng nh cc tnh

nng c th c h tr.

2.4.2.1. Ghp song cng phn chia theo tn s, FDD

Trong h thng FDD, knh ng ln v ng xung c n nh tn s

ring, v s liu ng xung c th truyn theo cm. Khung c di c nh c

s dng cho c ng xungv ng ln. iu ny cho php s dng cc kiu iu

ch khc nhau. Ngoi ra n cng cho php cc trm thu bao (SS: Subscriber Station)

s dng ch pht song cng (pht thu ng thi) v bn song cng (pht thu khng

ng thi) dng ty chn. Trongch bn song cng, b iu khin bng thng

khng cp pht bng thng ng ln cho SS khi n thu s liu trn knh ngxung, bao gm c tr truyn lan, khong thi gian chuyn i t pht sang thu ca SS

(SSTTG)v chuyn i t thu sang pht ca SS (SSRTG).

Hnh 2.2 cho thy vic n nh bng thng FDD theo cm. Vic knh ng ln

v ng xung u s dng khung c di c nh lm n gin gii thut n nh

bng thng. SS song cng c th lin tc i thu t knh ng xung trong khi SS

bn song cng ch c th thu t knh ng xung khi n khng pht trn ng ln.

ngxung

ngln

Khung

Thi gian

Qung b

SS song cng

SS bn song cng 1

SS bn song cng 2

Hnh 2.2. n nh bng thng FDD theo cm

2.4.2.2. Ghp song cng phn chia theo thi gian, TDD


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Trong trng hp TDD, truyn dn ng xungv ng ln xy ra trong cc

thi gian khc nhau v cng s dng chung mt tn s. Khung TDD (xem hnh 2.3) c

di c nh v cha mt khung con ng xung v mt khung con ng ln.

thun tin cho vic phn chia bng thng, cc khung ny c chia thnh mt s

nguyn ln cc PS (Physical Slot: khe vt l). Vic n nh khung TDD thay i (thch

ng) vi s thay i n nh bng thng ng xung so vi n nh bng thng

ng ln. Phn chia ng xung v ng ln l mt thng s h thng v c

iu khin bi cc lp trn trong h thng.

Khung j-2 Khung j-1 Khung j Khung j+1 Khung j+2

n=(Tc x thi gian khung)/4

Thch ng

Khung con ng ln Khung con ng xung

PS0PSn-1

i vi SC, SCa, tc l tc k hiu; i vi OFDM v OFDMA tc l tn s ly mu danh nh (fs)

Hnh 2.3. Cu trc khung TDD.

2.5. CC TY CHN

2.5.1. H thng anten thch ng, AAS

Thng qua vic s dng nhiu phn t anten, h thng anten thch ng c th

ci thin c ly ph sng v dung lng h thng bng cch thch ng mu pht x

anten v tp trung pht x n tng SS. Hiu sut s dng tn ph tng tuyn tnh theos lng phn t anten. iu ny t c nh vic li cc tia n cc ngi s dng

khc nhau nh vy cth t c tha s ti s dng tn s gia cc bng mt v

ni t l vi s phn t anten. Ngoi ra cng tng c t s tn hiu trn tp m nh

vic kt hp tng quan cc tn hiu v c kh nng iu khin li ny cho cc

ngi s dng c th.Mt li ch na l gim c nhiu nh vic li cc hng pht

x bng khng n n cc cc ngun nhiu ng knh. Kt hp cc li ch do tng

li SNR ca mt s ngi s dng v li pht x khng cho php c th pht ng thi

cc cm n cc SS nm cch nhau trong khng gian. Cng c th p dng phng


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php ny cho ng ln mt cch tng h. Vic truyn ng thi cc cm khng ch

tng vng ph ca h thng m c th tng dung lng h thng.

Vic thit k ty chn AAS (Adaptive Antenna System: h thng anten thch

ng) cung cp c ch chuyn t mt h thng khng AAS n mt h thng cho phpASS, trong thay th ban u BS khng c AAS bng BS c AAS s lm mt dch

v ca cc SS khng c kh nng AAS.

trnh iu ny cn dnh mt phn khungcho lu lng khng AAS v mt

phn khung cho lu lng AAS. Vic n nh c thc hin ng bi BS. Cc SS

khng AAS s b qua lu lng AAS. nhn ra lu lng ny chng s dng cc

bn tin DL MAP v UL MAP (sp xp ng ln v ng xung).

Phn AAS ca khung ng xung c bt u bng mt tin t c th AASnh cho trn hnh 2.4 v 2.5.

Tint

ng

xungthngthng

FCH

C

m1

C

m2

TintAAS

VngAA

Sng

xu

ng

Cc cmng xungthng thng

Vng

ngln

A

AS

Cc cm ng lnthng thng

Hnh 2.4. Vng AAS, FDD


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Tint

ng

xu

ngthngthng

FCH

Cm1

Cm2

TintAA

S

VngAAS

ng

xu

ng

Cc cmng xungthng thng

Vngngl

nAAS

Cc cm ng lnthng thng

Hnh 2.5. Vng AAS, TDD


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2.5.2. M ha khng gian thi gian, STC

STC (s Alamouti) c th c s dng cho ng xung cung cp phn

tp pht (khng gian) bc hai. Hai anten pht c s dng ti BS v mt anten thu

c s dng ti SS. S ny i hi c tnh knh MISO (Multi Input Single

Output: nhiu u vo mt u ra). Hai anten pht pht ng thi hai k hiu s liu

OFDM khc nhau. B gii m pha thu s thc hin gii m sau khi nhn c c hai

k hiu ny t mi anten. Trong s ny mi k hiu c pht lp theo thi gian

trn hai anten khc nhau.

Hnh 2.6 cho thy v tr ca STC trong chui truyn dn OFDM. Mi anten pht

c mt chui truyn dn OFDM ring, nhng chng c cng b dao ng ni cho mc

ch ng b.

iu chknh con

ng giu vo

IFFT M ha

phn

tp pht

IFFT

IFFT

Lc DAC RF

Lc DAC RF

RF ADC Lc FFTB kt

hp phntp

B giiiu chknh con

Ly Logt l kh

ging

B giim

BS

SS

Hnh 2.6. Nguyn l STC.

2.5.3. Pht li t ng, ARQ

C ch ARQ (Automatic Repeat Request) l mt b phn ca MAC, n c

s dng nh mt ty chn. Khi ARQ c ci t, n c cho php theo tng kt

ni. ARQ s c c t v m phn trong qu trnh to lp kt ni. Mt kt ni

khng th c hn hp c lu lng ARQ v lu lng khng ARQ.

2.5.4. Cu hnh im a im v li

WiMAX c nhcho php h tr c hai cu hnh im a im (PMP: Point to

Multipoint) v li(Mesh), trong cu hnh PMP l bt buc.


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1. Cu hnh bt buc im a im, PMP

Trong chun IEEE 802.16e-2005 cho cc h thng khng dy c nh, cu hnh

im a im (PMP) l bt buc. Trong cu hnh ny, ng xung t BS n cc SS

lm vic trn c s im a im. ng truyn v tuyn ca IEEE 802.16e -2005 lmvic vi mt BS trung tm c anten phn on c th x l ng thi nhiu on .

Trong mt knh tn s cho trc v mt on cho trc, tt c cc SS nhn c

cng mt truyn dn. BS ch l my pht pht theo hng ny, v th n ch vic pht

m khng phi hp vi cc SS khc tr vic phn chia thi gian cho ng ln v

ng xung trong TDD. Ni chung ng xung pht qung b. Trong trng hp

bn tin sp xp ng xung (DL MAP) khng ch th mt on khung con ng

xung cho mt SS c th, th tt c cc SS c th thu on khung con ny u s thu.

Cc SS s kim tra CID (Connection Identifier: nhn dng kt ni) ca cc PDU

(Protocol Data Unit) thu c v s ch nhn cc PDU gi cho n.

2. Cu hnh li, Mesh

Khc bit chnh gia ch PMP v ch li l trong ch PMP, lu

lng ch xy ra gia BS v cc SS, cn trong ch li (Mesh) lu lng c th

c nh tuyn qua cc SS khc v c th xy ra gia cc SS. Ph thuc vo gii

thut cu giao thc truyn dn c s dng, iu ny c th c thc hintrn c sbnh ng khi s dng lp biu phn b hoc trn c s u tin. ca Mesh BS.

Trong mt mng Mesh, mt h thng c kt ni trc tip n cc dch v ng

trc ra bn ngoi mng Mesh c gi l Mesh BS. Tt c cc h thng khc ca

mng Mesh u c gi l Mesh SS. Ni chung, cc h thng ca mng Mesh c

gi l cc nt. Trong ng cnh Mesh, cc ng ln v ng xung c nh ngha

l lu lng trong hng n Mesh BS v v ngc li.

2.6. TNG KT CC C T GIAO DIN V TUYN KHC NHAUTRONG IEEE 802.16e2005 CHO TRUY NHP C NH

Bng 2.1. tng kt cc c t giao din v tuyn khc nhau trong chun IEEE

802.16 e cho truy nhp c nh.

Bng 2.1. Cc c t giao din v tuyn

Tn c t ng dng Yu cu

lp MAC

Cc ty

chn

K thut

ghp song


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b sung cng

Wireless MAN-SC 10-66GHz TDD

FDD

WirelessMAN-SCa

Cc bng tn cp

php di 11

MHz

AAS**

ARQ***

STC****

TDD

FDD

WirelessMAN-

OFDM

Cc bng tn cp

php di 11

MHz

AAS

ARQ

Cu hnh

li

STC

TDD

FDD

WirelessMAN-

OFDMA

Cc bng tn cpphp di 11

MHz

AASHARQ

STC

TDDFDD

WirelessHUMAN* Cc bng tn min

php di 11

MHz

DFS AAS

ARQ

Cu hnh

li

STC

TDD

* HUMAN: High Speed Unlicensed Metropolitan Network: Mng th min

php tc cao

** AAS: Adaptive Antenna System: H thng anten thch ng

***ARQ: Automatic Repeat Request: Yu cu pht li t ng

****STC: Space Time Coding: M khng gian thi gian

V WiMAX ch cp n OFDM v OFDMA nn trong cc phn di y ta

s xt WirelessMAN OFDM v WirelessMAN OFDMA.

2.7. WIRELESSMAN OFDM

2.7.1. Tng quan cc tnh nng ca WirelessMAN OFDM

Bng tn cng tc cn thit cho WirelessMAN OFDM l 2-11GHz, v khng

th m bo truyn khng trc x (NLOS: Non Line of Sight) trong bng tn cao hn.

Bng 2.2 cho thy cc tnh nng chnh ca lp vt l (PHY) ca IEEE 802.16e -2005

cho h thng khng dy c nh.


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Bng 2.2. Cc tnh nng ca WirelessMAN OFDM

Tnh nng Li chDng sng 256 im FFT OFDM h tr cc mi trng LOS v NLOS

ngoi tri

iu ch v thay i m sa li thch

ng theo tng cm sng v tuyn

m bo ng truyn v tuyn bn vng

nhng vn duy tr tc bit cc i cho

tng thu bao

H tr TDD v FDD p ng cc iu l khc nhau cc vng

khc nhau trn th gii

Kch thc knh linh hot (3,5MHz;

5MHz; 10 MHz...)

Cung cp nhu cu khai thc linh hot trong

cc bng tn khc nhau ph thuc vo yu

cu knh khc nhau trn th gii

Thit k h tr cc h thng an ten

thch ng (to bp) v STC

Cc h thng ny cng kh dng v gi

thnh ngy cng r. Chng cho php gim

nhiu, tng li h thng v s tr nn

quan trong khi trin khai BWA.

Vic s dng nhiu im FFT trong WirelessMAN OFDM hn trong 802.11a

(256 so vi 64) cho php m rng thi gian mt k hiu v v th kh nng chu ng

tr a ng ln hn i vi hot ng NLOS c ly xa.

m bo tnh bn vng v thng lng cc ai, cc s iu ch thch ng

c s dng trong chun WirelessMAN OFDM: QPSK, 16QAM, 64 QAM. Khi iu

kn knh tt, iu ch 64QAM tc s liu cao c la chn, tri li khi iu kin

knh km iu ch QPSK tc s liu thp hn c la chn (hnh 2.7).


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Trm gc

SS3

SS1

SS2

SS4

Hnh 2.7. iu ch thch ng trong lp vt lMt tnh nng tin tin khc ca WirelessMAN OFDM l n cho php nh c

knh t 1,75 MHz n 20 MHz. V th nh sn sut thit b c th linh hot s dng

ton b bng thng c cp pht. Chng hn nu bng thng c cp pht l 14

MHz, h s khng s dng bng thng 6MHz v s lng ph 2MHz. H c th s dng

bng thng 1,75MHz, 3,5 MHz cng nh 7MHz. Nh vy ton b bng thng s c

s dng.

2.7.2. Cu trc khung

H thng s dng khung c di 0,5; 1 hay 2 ms. Mi khung c chia thnh

cc khe vt l (PS: Physical Slot) n nh bng thng v nhn dng s chuyn i

lp vt l. Lp vt l OFDM h tr ba phng n ghp song cng: FDD, TDD v

HFDD. Mi khung bao gm mt khung con ng xung v mt khung con ng

ln. Trong phng n FDD khung con ng xung v ng ln c truyn trong

ton b thi gian khung nhng hai tn s khc nhau. Trong phng n TDD, khung

con ng ln c truyn tip sau khung con ng xung trong cng mt thi giankhung trn cng mt sng mang, gia khai khung con ny c mt khong bo v

trnh chng ln do ng b khng tt. Mi khung cha cc PDU (Protocol Data Unit:

n v s liu giao thc) lp vt l, cc khong trng v cc khong bo v.

Cu trc khung con ng xung v ng ln ca OFDM c cho trn hnh

2.8 v 2.9.

Khung con ng xung ch cha mt PDU ng xung. Khung con ng ln cha

cc khong va chm (tranh chp) c lp biu cho nh c ly khi u, yu cu


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bng thng v mt hay nhiu PDU lp vt lng ln t cc SS khc nhau. PDU lp

vt l ng xung bt u bng mt tin t di s dng cho ng b lp vt l. Sau

tin t ny l cm FCH (Frame Control Header: tiu iu khin khung). Cm FCH

c di mt k hiu OFDM c pht bng cch iu ch BPSK vi s m ha

knh t l m 1/2. FCH cha DLFP (DL Frame Prefix:tin t khung ng xung)

c t h s cm v di ca mt hay nhiu cum ng xung tip sau FCH. Bn tin

DL-MAP (sp xp ng xung) (nu c truyn trong khung ny) s l PDU ca

lp MAC u tin tip sau FCH. Sau DL-MAP (nu c truyn) l UL-MAP (sp

xp ng xung). Tiptheo UL-MAP l UCD (m t knh ng ln) v DCD (m

t knh ng xung) nu cc m t ny c truyn. Mc d cm 1 cha thng tin

qung b, nhng khng nht thit phi s dng iu ch v m ha chc chn nht. C

th s dng s iu ch m ha hiusut nht cho ttc cc SS ca BS.Cc cm ng xung sau FCH c truyn vi cc h s cm khc nhau. Mi

cm cha mt s nguyn cc k hiu OFDM. V tr v h s cm th nht c c t

trong DLFP. V tr v h s ca cc cm tip theo c c t trong DL-MAP c

pht qung b trong cm 1.

Khung n-1- Khung n Khung n+1 Khung n+2

DL PHY PDU

Tin t FHC Cm DL#1 Cm DL#m

DLFP

MAC PDU 1 MAC PDU n m

Cc bn tinqung b

Cc MAC PDUthng thng

Cm DL#2

Mt k hiu OFDM sdng BPSK t l 1/2

Tiu MAC(6 byte)

Ti tin MAC(ty chn)

CRC (tychn)

Cha mt hay nhiu cm DL vi iu ch v m hakhc nhau c pht theo th t gim dn bn chc

Thi gian

DL: Downlink: ng xungMAC: Medium Access Control: iu khin truy nhp mi trngPDU: Protocol Data Unit: n v s liu giao thcDL-MAP: sp xp ng xungUL-MAP: sp xp ng lnDCD: Downlink Channel Descriptor: m t knh ng xungUCD: Uplink Channel Descritor: m t knh ng lnDLFP: Downlink Frame Prefix: tin t ng xung

Cha: DL-MAPUL-MAP, DCD,

UDC

Khung con ng xung

Hnh 2.8. Cu trc khung OFDM ng xung


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Khung n-1- Khung n Khung n+1 Khung n+2

Thi gian

UL: Uplink: ng lnMAC: Medium Access Control: iu khin truy nhp mi trngPDU: Protocol Data Unit: n v s liu giao thc

Khung con ng ln

Khe va chm nh c ly lnu

Khe va chm yu cubng thng

PDU lp vt l t SS#1 PDU lp vt l t SS#n

Tin t Cm UL

MAC PDU#1 MAC PDU#n m

Mt cm UL cho mt PDU lp vtl c truyn theo iu ch v

m ha ring cho tng SS

Tiu MAC(6 byte) Ti tin MAC(ty chn) CRC (tychn)

Hnh 2.9. Cu trc khung OFDM ng ln

DL-MAP xc nh mc s dng cc on thi gian ng xung cho mt cm.

UL-MAP xc nh mc s dng ng ln c th hin dch thi cm so vi

thi im cp pht ban u.

DDC v UDC l cc bn tin MAC m t cc c tnh lp vt l ca knh

ng xung v ng ln.

Tin t trong khung ng xung c gi ltin t di bao gm CP sau l

4x64, tip theo li l mt CP vi 2x128 mu i sau nh trn hnh 2.10.

CP CP64 64 64 64 128 128

TG GTTFFT TFFT

Hnh 2.10. Tin t di ng xung

Tin t di c s dng ng b v c tnh knh.

2.7.3. Cu trc lp vt l WirelessMAN OFDM

2.7.3.1. Cc thng s WirelessMAN OFDM

Cc thng s chnh ca WirelessMAN OFDM OFDM c cho trong bng 2.3(cho trng hp bng thng 3,5MHz)


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Bng 2.3 Cc thng s chnh WirelessMAN OFDM

Thng s Gi tr

Bng thng 3,5MHz

T l tn s ly mu trn bng thng,

n=fs/B

i vi bng thng l bi s 1,75 GHz:

n=8/7, i vi bng thng l bi s 1,5

GHz: n=86/75, i vi bng thng l bi s

1,25 GHz: n=144/125, i vi bng thng l

bi s 2,75GHz: n=316/275, i vi bng

thng l bi s 2GHz: n=57/50; i vi

bng thng khng c c t khc: n=8/7.

S im FFT 256

S sng mang con tch cc 200

S sng mang con bo v (tri) 28

S sng mang con bo v (phi) 27

Ch s dch tn ca cc sng mang con

bo v

-128, -129,...,-101

+101, +102,..., +127

Khong cch tn s sng mang con

(kHz), f

15,625

Thi gian k hiu hu ch (s), TFFT 64

Khong bo v vi gi thit 12% (s),

TGP

8

Thi gian k hiu OFDM (s), T 72

T l di tin t trn di hiu

dng ca k hiu OFDM (TG/TFFT)

1/4, 1/8, 1/16, 1/32

2.7.3.2. S khi my pht v my thu WirelessMAN OFDM

My pht v my thu WirelessMAN OFDM c th c chia thnh 2 phn:phn bng gc v phn v tuyn (xem hnh 2.11).


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Bnggc

D/A

D/A

IFLO

RFLO

90

RFLO

IFLO

A/D

A/D

Bnggc90

Sync

Re

Im

Lungbit

Lungbit

Re

Im

Myphtvtuyn

Mythuvtuyn

o

K hiu:

Re: Phn thc, Im:Phn o, D/A: bin i s vo tng t, A/D: bin i tng t vos, IFLO: B giao ng ni trung tn, RF LO: B giao ng ni v tuyn, Sync: Mch

ng b

Hnh 2.11. S khi my pht v my thu WirelessMAN OFDM

Trc ht lung bit ti u ra ca MAC c a n bng gc ca my pht,

sau x l bng gc, lung s c chia thnh phn thc (Re) v phn o (Im). Sau

bin i s v tng t (D/A), phn thc v phn o c bin i vo cc sng ngpha v vung gc. Sng ng pha c nhn vi sng mang trung tn hm cos, cn

sng vung gc c nhn vi sng mang trung tn hm sin. Sau hai sng ny

c cng vi nhau to thnh sng mang trung tn c iu ch. Cui cng sng

ny c nhn vi sng mang v tuyn c bin i nng tn trc khi vo anten.

Ti my thu, cc thao tc ngc c thc hin theo th t ngc li. Cn m

bo ng b chnh xc m bo x l bng gc chnh xc. Cn ng b tn hiu

OFDM cn thit pht hin gi. ng b bao gm ng b k hiu v ng b tn

s.

Pht hin gi nhm tm ra v tr u ca gi, qu trnh ny c thc hin vi

s h tr ca cc k hiu hoa tiu (chng hn cc tin t). C hai cch thc hin

iu ny: (1) Ly t tng quan tn hiu thu, trong trng hp ny tin t thng bao

gmhai phn ging nhau; (2) Ly tng quan tn hiu thu vi cc tin t. V tr nhn

c gi tr nh chnh l im u ca gi.

Cc tn hiu thu tng t cn c ly mu ti thi im chnh xc ca chu k

ly mu (chu k A/D)cho qu trnh x l tn hiu s. Tuy nhin pha v chu k ly mu


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lun khc nhau gia D/A (pha pht) v A/D (pha thu). C th hiu chnh khc bit

ny bng vng kha pha tr (DPLL: Delay Phase Locked Loop) v VCO iu chnh

tn s A/D. V pha thu lun c th xc nh chnh xc c v tr cu cc hoa tiu trn

chm tn hiu v ly mu sai ch dn n quay chm tn hiu, v th da trn khong

cch quay ta c th tnh ra c cc tn s cn thit iu chnh A/D.

Cc h thng OFDM rt nhy cm vi dch tn v y l nguyn nhn dn n

mt tnh trc giao gia cc sng mang con. Dch tn c c tnh vi s h tr cu

cc tin t v dch pha trn chm tn hiu dn n dch tn s cc sng mang con. C

th thc hin c tnh trong c min thi gian ln min tn s da trn mt tiu chun

thng k no , chng hn kh ging cc i. u ra ca b c tnh c a ngc

tr v iu chnh VCO.

Cu trc bng gc c trnh by trn hnh 2.12.

Ngunhin ha

M ha

knhiu ch

Lp rpkhung

256

IFFT

Chn

CPP/S

Knh

ng bS/PLoi CP256 FFTc tnh knh

Cn bngmin tn s

Tho gkhunng

Gii iu chGii m

knh

Gii ngunhin

Bng gc pht

Bng gc thu

Hnh 2.12. S khi bng gc ca my pht v my thu WirelessMAN OFDM

Trc ht lung bit t MAC c ngu nhin ha, sau c m ha knh

chng li cc nh hng l gim cht lng ca knh nh: tp m, phainh v nhiu.

tng hiu qu m ha knh lung s sau m ha knh c an xen. M ha knhc th l Reed-Solomon, xon kt hp chch b ( iu chnh tc bit). M turbo v

m turbo xon (CTC) cng vi an xen CTC cng c th c s dng dng ty

chn.

iu ch thc hin sp xp tn hiu s vo dng tng t c th truyn n

trn knh. iu ch c s dng l BPSK. QPSK, 16QAM v 64QAM m Gray.

iu ch OFDM bao gm ba phn: lp rp khung OFDM, to lp tn hiu

OFDM bng IFFT v chn tin t chu trnh (CP: Cyclic Prefix).


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Ti pha thu ngoi cc khi thc hin thao tc ngc so vi ph t, ngoi ra cn

c thm b cn bng knh. C ba dng b cn bng knh trong min tn s: b cn

bng LS c h tr bi hoa tiu, b cn bng LMMSE vi h tr hoa tiu v b cn

bng LS vi h tr tin t.

Knh truyn l knh AWGN v phainh Rayleigh.

2.7. 4. M t cc khi

2.7.4.1. Ngu nhin ha, PBRS

Khi u tin cu my pht l khi ngu nhin ha. Khi ny c s dng

trnh xy ra cc chui di ton "1" hoc ton "0". Cc gi s liu c ngu cng

modul-2 vi mt chui gi ngu nhin (PRBS: Pseudo Random Binary Sequence:chui nh phn gi ngu nhin). Trong chun WirelessMAN OFDM, b ngu nhin

ha l mt thanh ghi dch 15 bit c hai cng XOR (xem hnh 2.13).

1 2 3 4 5 6 7 8 9 10 11 12 13 14 15

S liu vo S liu ra

Hnh 2.13. B ngu nhin ha

a thc thc to m ca b ngu nhin ha trong trng hp ny l:

g(x)=x15+x+14+1. Ti khi u ca mi cm thanh ghi dch PRBS c xa v c

np bit chui hai ging 100101010000000. Ngu nhin ha chr p dng cho cc bit

thng tin.

Ti my thu s ny cng c s dng gii ngu nhin.

2.7.4.2. Khi m ha knh

M ha knh c thc hin bng cch mc ni hai m Reed -Solomon v m

ha xon c t l tng thch (RS-CC). H tr m BTC (Bock Turbo Code: m turbo

khi) v CTC (Convolutional Turbo Code: m turbo xon) lty chn. T l m RS-

CC 1/2 lun c s dng khi yu cu truy nhp mng (tr cc ch phn knh con

trong ch s dng m xon 1/2) v trong cc cm FCH.


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Trc ht lung s c chia thnh cc khi v a vo b m ha RS, sau

c a vo b m ha xon CC (Convolutional Code) vi kt cui bng khng.

M Reed-Solomon

Vai tr ca m ha knh l chn thm cc bit d trc khi khi pht sa li

pha thu. Khi u tin trong m ha knh l b m ha Reed-Solomon. M Reed-

Solomon l m khi cho php hiu chnh li cm tt. Cc m ny c k hiu dng

(N,K,T), trong N l s byte u ra, K l s byte u vo v T l s byte c th sa

li c. Vi K byte u vo b m ha, ta c K byte ny ti u ra b m ha vi

tip sau l N-K byte d b sung hiu chnh li. B m ha Reed-Solomon c rt

ra t b m ha RS h thng chun RS(N=255,K=239,T=7).

B m ha xon/ gii m Viterbi

B m ha xon c trnh by trn hnh 2.14 sa li ngu nhin. B m ha

xon ny c t l m 1/2 v di hn ch 7.

D1 D2 D3 D4 D5 D6

Vo sliu

Ra sliu

Y

X

Hnh 2.14. B m ha xon

a thc to m trong trng hp ny nh sau:

G1=(171)OCTcho X (2.1)

G2=(133)OCTcho Y (2.2)


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Ti pha thu b gii m Viterbi c s dng gii m vi su ca li l

34.

2.7.4.3. B an xen/ gii an xen

Tt c cc bit sau m ha knh RS-CC u s c an xen khi bi b an xen

khi vi kch thc tng ng vi s cc bit sau m ha trn cc knh con c n

nh trn k hiu OFDM, Ncbps. Ph thuc vo s iu ch BPSK, QPSK, 16QAM

hay 64QAM, Ncbpsbng 192, 384, 768, 1152. an xen c thc hin theo hai bc

hon v. Hon v bc 1 m bo rng cc bit cnh nhau c sp xp ln cc sng

mang khng cnh nhau. V th khi phainh su lm hng mt bit th bit cnh n khng

b nh hng ca phainh nh vy c th hiu chnh c nh hng cu phainh ny.

Hon v th hai m bo rng cc bit cnh nhau lun phin c t vo cc bit ctrng s cao hn hoc thp hn ca chm tn hiu. Nh vy tch tn hiu chnh xc

hn v trnh c cc on di cc bit c tin cy thp. Gii an xen c thc hin

ngc li.

Phng trnh (2.3) biu din quan h gia cc ch s k, mkv jkca bit sau khi

an xen ln th nht v ln th hai. Trong Ncl tng s cc bit trong khi, s=M/2,

trong M l bc ca iu ch (2 i vi QPSK, 4 i vi 16QAM v 6 i vi

64QAM). V d l mt thng s bt k c t bng 16:

mod( )

koor

d

ck d

Nm k fl

d

(2.3a)

k

mod( )

.m. oor oor

s

kk k c

c d

d mj s fl m N fl

N

(2.3b)

Trong : k=0,1,., Nc-1

mod( )

.. oor oor

sj c

c d

j d jm s fl j N fl

N

(2.4a)

j

c

d.m1 . oor

Nj c

k dm N fl

(2.4b)

trong hmfloor(x) l hm ly gi tr nguyn ca (x)

2.7.4.4. iu ch/ gii iu ch


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Sau an xen, lung bit c a ln b sp xp iu ch c sp t ln

chm tn hiu. iu ch BPSK, QPSK, 16QAM v 64QAM m Gray c s dng

(trong bng min php 64-QAM l ty chn). Chm tn hiu ny s c nhn vi mt

hng s c cn bng cng sut trung bnh. c bng 1 cho BPSK, 1/ 2 cho QPSK,

1/ 10 cho 16QAM v 1/ 42 cho 64QAM.

Bng 2.4 cho thy quan h gia iu ch v t l m c s dng trong cm ng

xung u tin ngay sau FCH.

Bng 2.4. Quan h gia iu ch v t l m

Nhn dng t l

(Rate_ID)

iu ch T l m RS-CC

0 BPSK 1/2

1 QPSK 1/2

2 QPSK 3/4

3 16QAM 1/2

4 16QAM 3/4

5 64QAM 2/3

6 64QAM 3/4

7-15 d phng

Hnh 2.15 cho thy cc chm tn hiu ca iu ch BPSK, QPSK, 16-QAM v 64

QAM.


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hiu OFDM vo phn u ca n. Trong chun IEEE 802.16e -2005, c th p dng

CP thch ng vi di 1/4; 1/8; 1/16; 1/32. Ti pha thu thao tc ngc c thc

hin.

2.7.4.6. B c tnh knh v cn bng

1. M hnh knh

Knh truyn c cc c tnh sau:

Tn hao ng truyn (che ti chng hn)

Tri tr a ng

Cc c tnh phainh

Tri Doppler Nhiu ng knh v nhiu knh ln cn

Tn hao ng truyn

Tn hao ng truyn ph thuc rt nhiu vo a hnh v mt cc vt chn

trn ng truyn sng. Mt vt chn cao v a hnh i ni s dn n tn hao

ln.

Tri tr a ng

Mi trng tn x dn n tin hiu truyn n im thu theo nhiu ng vi

cc thi gian tr khc nhau. Tn hiu ti im thu s l tng vect ca cc tn hiu n

t cc ng khc nhau ni trn.

Phainh

Phainh l qu trnh trong tn hiu thu b thng ging mt cch ngu nhin.

Phainh c c trngbng mt m hnh phn b thng k. Khi c rt nhiu ng

truyn khng trc x t BS n SS v cng sut ca chng ln hn nhiu so vi cngsut ca ng trc x, ta c phainh Rayleigh. Trong trng hp ng truyn trc

x ni tri so vi cc ng truyn khng trc x ta c phainh Rice.

Dch Doppler

Dch tn Doppler gy ra do s chuyn ng tng i gia my thu v my

pht. i vi mi trng thng tin v tuyn di ng, ph thuc vo a hnh ta c th

c phn b mt ph xng sut Doppler dng Jake hoc Gauss.


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Ngoi cc yu t knh ni trn, khong cch nht qun, nhiu ng knh, h s

gim li anten cng cn c xem xt trong h thng thng tin a knh v MIMO.

2. c tnh knh v cn bng knh

Cc tn hiu OFDM b nh hng ca phainha ng v hiu ng Doppler

khi truyn trn knh v tuyn. c th gii iu ch v gii m knh chnh xc, my

thu cn c tnh c hm truyn t knh. Tip sau c tnh knh l cn bng knh.

c tnh knh c th c thc hin c trong min tn s v min thi gian. i vi

h thng OFDM, FFT cn c thc hin cho tt c cc sng mang con v th x l

trong min tn s c thc hin trc tip. V th di y ta s xt c tnh knh v

cn bng knh trong min tn s cho h thng SISO (mt anten pht v mt anten thu).

Ta k hiu X l tn hiu c pht, H l p ng xung kim, l tp m trng

ca knh, tn hiu thu s l:

Y=X*H+ (2.6)

X=(Y-)/H=Y/ H (2.7)

trong H l hm truyn t knh c tnh. khi phc li tn hiu Y ta cn bit

H . Trong chun IEEE 802.16e-2005, ta c mt s tn hiu bit trc ti my thu: cc

hoa tiu v cc tin t. Bng cch phn tch s thay i ca cc tn hiu ny khi c hng

c truyn n my thu t pha pht, my thu c th tnh ra c H da trn mt s

tiu ch thng k. Di y l ba phng php c tnh knh da trn c cc hoa tiu

v cc tin t di:

B c tnh knh LS vi h tr hoa tiu

B c tnh knh LMMSE vi h tr hoa tiu

B c tnh knh LS vi h tr tin t di

Cc tiu ch thng k c chn cho ba phng php ny s l: (1) c tnh

theo bnh phng trung bnh (LS: Least Mean Square), c tnh theo bnh phng

trung bnh cc tiu tuyn tnh (LMMS: Linear Minimum Mean Square).

Trong c tnh knh da trn LS, hm truyn t knh c tnh c tnh ton

n gin bng cch chia tn hiu thu theo tn hiu c pht chnh xc.

HLS=Y/X (2.8)


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trong Y l vect thu cn X l vect pht.

Trong c tnh knh da trn LMMSE,

H LMMSE=Rhh{Rhh+2N

(XXh)-1 H LS (2.9)

Rhh=E{ H LS. hLSH } (2.10)

trong 2N

l phng sai ca tp m Gauss trng cng, ch s h pha trn l chuyn

v Hermitian ca ma trn.

2.8. WirelessMAN OFDMA

WirelessMAN OFDMA c xy dng trn c s iu ch OFDM v c

thit k cho hot ng khng trc x (NLOS) trong bng tn thp hn 11 MHz.Th d, nu bng thng quy dnh l 14 MHz trong di t 3400 MHz n 3414

MHz, th cc bng thng c php s dng s l cc gi tri c cho trong bng 2.4.

Bng 2.4. Th d v t knh chocc bng cp php

To knh (MHz) Cc tn s trung tm

14 3407

7 3403,5+n.0,25 n{0,...,28}3,5 3401,5+n.0,25 n{0,...,42}

1,75 3400,875+n.0,25 n{0,...,49}

2.8.1. M t k hiu OFDMA, cc thng s k hiu v tn hiu pht

1. M t trong min thi gian

Bin i Fourier ngc to nn dng sng OFDMA, khong thi gian ny

ch gi l thi gian hiu dng ca k hiu, TFFT. Copy phn cui cng (TGD) ca

thi gian hiu dng k hiu (CP: Cyclic Prefix) c s dng loi b nh hng a

ng trong khivn duy tr c tnh trc giao ca cc sng mang con. Hnh 2.16 cho

thy cu trc ny.


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TGDTFFT

T

Hnh 2.16. Cu trc thi gian ca k hiu OFDM

Khi du, SS phi tm tt c cc CP c th c cho n khi tm c CP c sdng bi BS. SS s s dng chnh CP ny cho ng ln.

2. M t trong min tn s

M t min tn s bao gm cu trc ca mt k hiu OFDMA

Mt k hiu OFDMA bao gm cc sng mang con, trong s lng cc sng

mang con xc nh kch thc FFT c s dng. C mt s dng sng mang con:

Cc sng mang con s liu: truyn s liu Cc sng mang con hoa tiu: cho cc mc ch c tnh khc nhau

Cc sng mang con rng: cho cc bng bo v v sng mang DC.

Trong ch OFDMA, cc sng mang tch cc c chia thnh cc tp sng

mang con, mi tp c gi l mt knh con. Trn ng xung mt knh con c th

c th c dnh cho cc my thu (nhm cc my thu) khc nhau. Trn ng ln,

my pht c th c n nh mt hay nhiu knh con nhiu my pht c th pht

ng thi. Khi nim ny c cho trn hnh 2.17.

Knh con 1 Knh con 2 Knh con 3Knh DC

Bng bo v triBng bo v phi


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Hnh 2.17. M t min tn s OFDMA (ba knh)

3. Cc thng s s cp

Cc thng s c trng cho mt k hiu OFDMA nh sau:

B: Bng thng knh

Nu: S sng mang con hiu dng (bao gmc sng mang DC)

n: tha s ly mu. Thng s ny cng vi B v N xc nh khng khong

cch gia cc sng mang con.

G: TGD/TFFT; cc gi tr dc s dng nh sau: 1/32, 1/16, 1/8 v 1/4

4. Cc thng s th cp

N: s hai ly tha nh nht ln hn Nu

Tn s ly mu: fs=n.B khong cch gia cc sng mang: f=fs/N

Thi gian hiu dng k hiu: TFFT=1/f

Thi gian k hiu OFDM: T=TGD+TFFT

Thi gian ly mu: TFFT/N

4. Tn hiu pht

Tn hiu pht c xc nh nh sau:

j

RF,k

R

(t - kT) =x

c

i=N/2-1

i,k

FFTi=-N/2

GD FFT

ie w(t - kT) x exp f + (t - kT) ,

T

kT - T t kT +T

0, nu khc

2

; (2.7)

2.8.2. Sp xp knh con v khe OFDMA

Cc sng mang con trong WiMAX c chia thnh cc nhm sng mang con

c gi l cc knh con. WiMAX c nh ch cho php s dng mt dng hn ch

Sp xp knh con trn ng ln. Tiu chun nh ngha 16 knh con trong c th

cp pht cho mt trm thu bao (SS) trn ng ln 1,2,4,8 hoc ton b tp knh con.

Sp xp knh con trn ng ln trong WiMAX c nh cho php cc trm thu bao

ch s dng mt phn (t nht l 1/16) bng thng m trm gc cp pht cho n. Mc


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cp pht bng thng m bo ci thin qu ng truyn tng cng vng ph

sng hoc tit kim cng sut acqui. Tha s Sp xp knh con 1/16 cho php tng

qu ng truyn 12dB.

Khe OFDMA l ti nguyn thi gian-tn s ti thiu m h thng WiMAX cppht cho mt lin kt. Mi khe bao gm mt knh con trn mt, hai hay ba k hiu

OFDM ty thuc v s phn chia knh c s dng. Mt chui cc khe lin tc

c n nh cho mt ngi s dng c gi l mt vng (Region).

2.8.3. n nh cc sng mang con OFDMA

i vi OFDMA, tn s ly mu fs=nB. Lai b cc sng mang con bo v t

N sng mang con ta c cc sng mang con kh dung. i vi c ng ln v

ng xung, cc sng mang con ny c s dng n nh cho cc sng mang conhoa tiu v cc sng mang con s liu. Tuy nhin vic n nh ny khc nhau cho cc

vng khc nhau. i vi FUSC (Down Link Fully Used Subchannelization: Sp xp

knh con s dng ton b ng xung), cc tn s hoa tiu c n nh trc, cc

sng mang con cn li sdnh cho s liu v c chia thnh cc knh con. i vi

PUSC (Partially Used Subchannelization: Sp xp knh con s dng mt phn) trn

ng xung v ng ln, th trc ht tp cc sng mang con kh dng c chia

thnh cc knh con, sau cc sng mang con hoa tiu c n nh trong tng knh

con. Nh vy trong FUSC ch c mt tp sng mang con hoa tiu chung, cn trong

PUSC mi knh con c cc sng mang con hoa tiu cho ring mnh.


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2.8.4. Sp xp knh con ng xung

ng xung c th c chia thnh ba cu trc on vi m u l tin t.

Cc sng mang con tin t c chia thnh 3 tp sng mang. Ty thuc vo vic on

s dng tp sng mang no, ta s c ba nhm. Hnh 2.18 cho thy cu trc truyn dn

c s ng xung.

T

int

Khius

liu

Khius

liu

Khius

liu

Khius

liu

Kh

ius

liu

Kh

ius

liu

Khius

liu

Hnh 2.18. Cu trc truyn dn c s ng xung

2.8.4.1. Cu trc k hiu cho FUSC

Trong FUSC (Down Link Fully Used Channelization: Sp xp knh con s

dng ton b ng xung), cu trc k hiu c xy dng trn cc sng mang hoa

tiu, s liu v cc sng mang rng. Trc ht l k hiu cha cc hoa tiu tng ng

cng vi cc sng mang rng. Sau l cc sng mang cn li dnh cho s liu

(chng c chia thnh cc knh con).

C hai tp hoa tiu kh bin v hai tp hoa tiu c nh. Trong FUSC, mi on

s dng c tp hoa tiu kh bin v c nh. Trong ch STC, mi anten s dng

mt na ti nguyn tp hoa tiu. Bng 2.5 tng kt cc thng s ca mt k hiu.

Bng 2.5. Cc thng s ca mt k hiu

Thng s Gi tr

S sng mang con DC 1


S sng mang con bo v phi 172

S sng mang con kh dng 1703


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S sng mang con hoa tiu

Tp kh bin #0 24

Tp khng i#1 4

Tp kh bin#1 24

Tp khng i 4

S sng mang con s liu 1536

S sng mang con s liu trn mt knh con 48

S knh con 32

Hnh 2.19 cho thy th d v cu trc k hiu ng xung cho on 0 trn k hiu s

1 s dng FUSC

0 12 24 36 39 1692 1701

Bng bo v tri (173sng mang con)

Bng bo v phi(172 sng mang con)

Hnh 2.19. Cu trc k hiu ng xung cho on 0 trn k hiu s 1 s dng

FUSC

2.8.4.2. Cu trc k hiu ng xung PUSC

Trong PUSC (Partially Used Subchannelization: Sp xp knh con ngxung kiu sp xp knh con s dng mt phn) ng xung, cu trc k hiu c

thit k bng cch s dng cc sng mang con hoa tiu, s liu v khng. Trc ht k

hiu c chia thnh cc cm (Cluster) c s. Cc sng mang hoa tiu v s liu c

n nh cho tng cm. Bng 2.6 cho thy cc thng s ca cu trc k hiu cho trng

hp kch thc FFT bng2048.

Bng 2.6. n nh sng mangcon ng xung OFDM-PUSC


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Thng s Gi tr Ch thch

S sng mang con DC 1


S sng mang con bo v (phi) 183

S sng mang con kh dng 1681 gm c sng mang con

DC

S sng mang con trn mt cm 2x14

S sng mag con hoa tiu trn mi cm 2x4

S cc sng mang con s liu trn mi cm 24

S cm trong mt knh con 2

S cm 120

S knh con 60

Cu trc cm c cho trn hnh 2.20. Hnh 2.20 cho thy cc sng mang con

t tri sang phi theo ch s tng dn. xc nh v tr ca hoa tiu PUSC, cc k

hiu chn v l c c tnh t u vng hin thi. K hiu chn l k hiu u tin.

Tin t khng c tnh nh l b phn ca vng u tin.

K hiu chn

K hiu l

Sngmangcon

hoatiu

Sngmang

consliu

Hnh 2.20. Cu trc cm

n nh cc sng mang con cho cc knh con trong PUSC c thc hin nh sau:

1. Chia cc sng mang con thnh 120 cm vt l vi mi cm cha 14 sng mang

con lin k (bt u t sng mang con 0)

2.

nh s li cc cm vt l thnh cc cm logic theo cng thc sau:


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logicalCluster= RenumberingSequence((PhysicalCluster+13*IDCell)mod120)

Trong vng PUSC u tin ca ng xung, IDCell mc nh c s dng

v

bng 0

3. Chia Cluster thnh 6 nhm chnh. Nhm 0 gm cc cluster 0-23, nhm 1 gm

cc cluster 24-39, nhm 2 gm cc cluster 40-63, nhm 3 gm cc cluster 64-

79, nhm 4 gm cc cluster 80-103, nhm 5 gm cc cluster 104-119. Cc

nhm ny c th c n nh cho cc on nu on c s dng, mi on

c n nh t nht mt nhm

4. Thc hin n nh cc sng mang con cho cc knh con nh sau: trc ht n

nh cc sng mang hoa tiu trong tng cm, sau ly tt c cc sng mangcon s liu li trong k hiu phn chia chng vo cc knh con vi mi knh

cha 24 sng mang con s liu trong mi k hiu. Lu IDCell s dng cho

vng PUSC th nht bng khng

2.8.4.3. Cu trc k hiu ng xung TUSC1 v TUSC2

Cu trc k hiu TUSC1 v TUSC2 ging nh PUSC, tuy nhin s dng hon v

sng mang con khc.

2.8.5. Cu trc k hiu ng ln PUSC

Trong PUSC (Partially Used Subchannelization: Sp xp knh con ng

xung kiu sp xp knh con s dng mt phn) ng ln, cu trc k hiu c thit

k bng cch s dng cc sng mang con hoa tiu, s liu v khng.

ng ln h tr 70 knh con trong mi truyn dn s dng 48 knh con.

Mi ln truyn dn ng ln khi u bng thng s trong bng 2.7.

Bng 2.7. Cc thng s ca mt k hiu

Thng s Gi tr

S sng mang con DC 1


S sng mang con bo v phi 183


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S sng mang con kh dng 1681

S knh con hoa tiu 70

S lt 420

S sng mang con s liu trn mt knh con 48

Cu trc k hiu PUSC ng ln bao gm cc khe (cm). Cc khe trn ng

ln bao gm ba k hiu OFDMA v mt knh con, trong c 48 sng mang con s

liu v 24 sng mang con hoa tiu c v tr c nh.

Knh con c cu trc t 6 lt, mi lt c 4 sng mang con tch cc lin k vi

cu hnh nh cho trn hnh 2.21.

Sngmangcon

hoatiu

Sngmang

consliu

SththtmangconSt

ht

k

h

iu Khiu0

Khiu1

Khiu2

Hnh 2.21. M t lt ng ln

2.8.6. Khe OFDMA v vng s liu

Mt khe trong OFDMA PHY (lp vt l OFDMA) i hi c kch thc thi

gian ln knh con v l n v ti thiu dnh cho s liu.

nh ngha khe OFDMA ph thuc vo cu trc k hiu OFDM, trong khi cu

trc ny thay i i vi ng ln v ng xung.

i vi FUSC ng xung s dng han v sng mang con phn b, mi khel mt knh con trong mt k hiu OFDMA

i vi PUSC ng xung s dng hon v sng mang con phn b, mt khe

l mt knh con trong hai k hiu OFDMA

i vi PUSC ng ln s dng sng mang con phn b v i vi cc

TUSC1 v TUSC2 mt khe l mt sng mang con trong ba k hiu OFDMA


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Trong OFDMA, vng s liu l n nh hai chiu mt nhm cc knh con lin

tc trong mt nhm cc k hiu OFDM lin tc. n nh ny c th c biu din

dng hnh ch nht 4x3 nh trn hnh 4.22.

S th t k hiuSthtknhcon

Hnh 2.22. Th d v vng s liu trong n nh OFDM

2.8.7. Sp xp s liu OFDMA

S liu MAC c x l sau c sp xp ln min s liu cho ng

xung v ng ln theo cc gii thut sau. Min s liu c coi l mt nhm cc

knh con lin tc trong mt nhm cc k hiu OFDMA lin tc. Mt n nh c dng

ch nht kch thc 4x3 c cho trn hnh 2.22.

ng xung

1.

Phn chia s liu sau khi iu ch thnh cc khi c kch thc va mt kheOFDMA

2. Mi khe chim mt knh con trong trc knh con v mt hay nhiu k hiu

OFDMA trong trc thi gian (xem hnh 2.23). Sp xp cc khe sao cho khe c

s th t thp nht chim knh con c nh s thp nht trong k hiu

OFDMA cnh s thp nht

3. Tip tc sp xp theo ch s k hiu OFDMA tng dn. Khi t n bin ca

min s liu, tip tc sp xp bt u t knh con OFDM c s thp nht trong

k hiu kh dng tip theo.


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K-2 K-1 K K+1 K+2 K+3 K+4 K+5 K+6 K+7 K+8 K+9K+1

0

K+1

1K+12

0123

456789101112131415

L

Vngsliu

Sthtknhcon

ChskhiuOFDMA

KhenKhen+1

Khen+11

Vngngln

Khen+12

Hnh 2.23. Th d v sp xp cc khe OFDMA vo cc knh con v cc k hiu

trn ng xung (trong ch PUSC)

ng ln

Sp xp knh con chia thnh hai bc. Bc th nht chn cc khe OFDMA

n nh cho tng cm. Bc th hai thc hin sp xp cc khe c n nh.

Bc 1-n nh cc khe OFDMA cho cc cm

1. Chia s liu thnh cc khi c kch thc va mt khe OFDMA

2.

Mi khe s chim mt hay nhiu knh con trong trc knh con v mt haynhiu k hiu OFDMA trong trc thi gian (xem hnh 2.20). Sp xp cc khe

sao cho khe c s thp nht chim knh con c s thp nht trong k hiu

OFDMA c s thp nht

3. Tip tc sp xp theo ch s k hiu OFDMA tng. Khi t n bin ca min

ng ln (c nh du bng Zone _IE), tip tc sp xp t k hiu OFDMA

c s thp nht trong knh con kh dng tip theo.


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K-2 K-1 K K+1 K+2 K+3 K+4 K+5 K+6 K+7 K+8 K+9K+1

0

K+1

1K+12

0123

456789101112131415

L

Vngsliu

Sthtknhcon

ChskhiuOFDMA

Khen

Khen+10

Vngngln

Khen+11

Khen+22

Hnh 2.24. Th d v sp xp cc khe OFDMA vo cc knh con v cc k hiu

cho ng ln


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Bc 2- Sp xp cc khe OFDMA cho n nh ng ln

1. Sp xp cc khe sao cho khe c s thp nht chim knh con c s thp nht

trong k hiu OFDM c nh s thp nht

2. Tip tc sp xp sao cho ch s knh con tng dn. Khi t n knh con cui cng,

tip tc sp xp t knh con c s thp nht trong k hiu OFDMA tip theo ca n

nh ng ln. Th t c th hin bng mi tn trn hnh 2.24.

2.8.8. Cu trc khung PMP

WirelessMAN OFDMA trong cc bng tn cp php s dng cc phng php

ghp song cng FDD hoc TDD. Cc FDD SS c th l bn song cng (H-FDD).

Trong cc bng tn min php n s dng phng php ghp song cng TDD.

Trong h thng TDD, cu trc khung c thit lp trong mi ln truyn dn

BS v SS. Mi khung ng xung bt u bng mt tin t, sau l cc thi gian

truyn dn ng xung v ng ln (xem hnh 2.25). Trong mi khung, TTG

(khong trng chuyn i t pht sang thu) v RTG (khong trng chuyn i t

thu sang pht) s c chn vo ng xung v ng ln v ti kt thc khung

BS c th chuyn ch .

Trong cc h thng TDD v H-FDD, chuyn i ch pht thu ca SS cthc hin theo SSRTG v SSTTG. BS s khng pht thng tin ng xung n SS

mun hn (SSRTG+RTD) trc khi bt u n nh ng ln u tin ca n theo

lp biu v s khng pht thng tin ng xung sm hn (SSTTG+RTD) sau khi kt

thc n nh ng lncui cng theo lp biu, trong RTD l tr vng.

k

CmDL#3

CmDL#1

Tint

FCH

DL-MAP

UL-MAP

CmDL#2

CmDL#4

CmDL#5

CmUL#1

CmUL#2

CmUL#3

CmUL#4

CmDL#5

Tint

DL-MAP

FCHk+1 k+3

k+5k+7 k+9

k+11k+13 k+15

k+17k+20

k+23k+26 k+29 k+30

k+32

KhungconDL TTG KhungconUL RTG

St

ht

logick

nhcon

ss+1s+2

s+L

KnhconRanging

t


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Hnh 2.25. Th d v cu trc khung theo thi gian TDD (vng bt buc)

n nh knh con c th c thc hin theo hai cch: (1) s dng mt phn

cc knh con (PUSC: Partially Used Subchannelization) trong mt s knh con

c n nh cho my pht v (2) s dng ton b cc knh con (FUSC: Fully UsedSubchannelization) trong ton b cc knh con u c n nh cho my pht.

FCH (Frame Control Header: tiu iu khin khung) s c truyn bng iu ch

QPSK t l m ha 1/2 vi lp bn ln bng s m ha bt buc (thng tin FCH s

c pht trn bn s th t knh con logic lin tip) trong vng PUSC. FCH cha

DL_Frame_Prefix (tin t khung ng xung) v c t di ca bn tin DL -MAP

(i sau tin t khung ng xung) v m ha lp c s dng cho bn tin DL-MAP.

Cc chuyn i gia cc ch iu ch v m ha xy ra trn bin gii ca

khe OFDMA trong min thi gian (tr trng hp trong min AAS) v trn cc knh

con trong mt k hiu OFDMA trong min tn s.

Khung OFDMA c th cha nhiu vng (chng hn PUSC, FUSC, PUSC vi

tt c cc knh con, FUSC ty chn, AMC, TUSC1 v TUSC2), vic chuyn i gia

cc vng c ch th trong DL-MAP bi STC_Zone_IE.Hnh 2.26 cho thy khung

OFDM c nhiu vng.

TInt

PUSC(

vng

u

tinc

haF

CHv

DL-MAP)

PUSC

(DL-PermBaselX)

FUSC

(DL-PermBasely)

FUSC

(DL-PermBaselZ)

FUSCt

yc

hn

AMC

PUSCt

yc

hn

AMC

TUSC1

CÔNG NGHỆ WIMAX VÀ ỨNG DỤNG

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