Các Phương Pháp Mã Hóa Kênh Trong Thông Tin Di Đ NG 4G

N TT NGHIP
LI CAM OAN
Ti xin cam oan rng y l cng trnh nghin cu ca ti, c s h tr t
Gio vin hng dn l TS. Lm Hng Thch. Cc ni dung nghin cu v kt qu
trong ti ny l trung thc v cha tng c ai cng b trong bt c
cng trnh nghin cu no trc y.
Mi tham kho dng trong lun vn u c trch dn r rng tn tc gi, tn
cng trnh, thi gian, a im cng b.
Mi sao chp khng hp l, vi phm quy ch o to, hay gian tr, ti xin chu hon
ton trch nhim.
Hi An, ngy 05 thng 05 nm
2012
Sinh vin thc hin
Nguyn Th Thu Hng
GVHD: Lm Hng Thch SVTH: Nguyn Th Thu Hng

i
N TT NGHIP
LI CM N
hon thnh n tt nghip ny, li u tin em xin chn thnh cm n cc
thy gio, c gio Khoa Khoa hc v cng ngh Trng i hc Phan Chu Trinh,
nhng ngi dy d, trang b cho em nhng kn thc b ch trong bn nm hc va
qua.
Em xin by t lng bit n su sc nht ti thy gio Lm Hng Thch, ngi
tn tnh hng dn, ch bo em trong sut thi gian thc tp v lm n.

Em xin chn thnh cm n !
Hi An, ngy 10 thng 04 nm 2012

Sinh vin
Nguyn Th Thu Hng

ii
N TT NGHIP
MC LC
Nguyn Th Thu Hng ii
MC LC iii
DANH MC HNH V xii
Nguyn Th Thu Hng ii xii
MC LC iii xii
Nguyn Th Thu Hng ii iii xii
MC LC iii iii xii
DANH MC HNH V viii iii xii
LI M U 1 iii xii
Chng 1 S PHT TRIN CA H THNG THNG TIN DI NG VIT
NAM 1 iii xii
1.1 Gii thiu v cc h thng thng tin di ng 1 iii xii
1.2 Cng ngh thng tin di ng tng lai 6 iii xii
Hnh 1.1 Nng lc ca cc h thng 3G m rng. 8 iii xii
Hnh 1.2 Mng tng lai thng nht, bao gm nhiu h thng truy nhp an xen
nhau 9 iii xii
Hnh 1.3 Nhng vn k thut lin quan n cng ngh v tuyn 11 iii xii
Hnh 1.4 Cu hnh h thng 4G 15 iii xii
Hnh 1.5 Lin lc thng qua cc kt ni multi-hop 16 iii xii
Chng 2 M HA KNH TRONG THNG TIN DI NG 20 iii xii
2.1 Qu trnh m ha v nguyn l 20 iii xii

iii
N TT NGHIP
Hnh 2.1 Qu trnh m ha trong h thng truyn thng s 21 iii xii
2.2 Vai tr ca m ha 22 iii xii
2.3 Cc phng php m ha knh trong h thng 3G 23 iii xii
Hnh 2.2 M ha khi 24 iii xiii
Hnh 2.3 B m c tnh h thng v khng h thng 25 iii xiii
Hnh 2.4 B m ha xon t l 1/3 27 iv xiii
Hnh 2.5 B m ha Turbo 29 iv xiii
Hnh 2.6 B gii m Turbo 30 iv xiii
Hnh 2.7 S khi ca mt h thng MIMO 37 iv xiii
2.6 Kt lun chng 39 iv xiii
3.1 Phng php m ha khng gian - thi gian 40 iv xiii
Hnh 3.1 Mt m hnh h thng bng tn gc 41 iv xiii
Hnh 3.2 S m li 47 iv xiii
Hnh 3.3 B m li k=1, K=3 v n=2 47 iv xiii
Hnh 3.4 Li m v s trng thi vi k=1, K=3 v n=2 48 iv xiii
Hnh 3.5 S khi ca b m ha STTC 50 iv xiii
Hnh 3.6 ng bin gia tiu chun TSC v tiu chun vt 54 iv xiii
Hnh 3.7 B m ha STTC vi 4-PSK 55 iv xiii
Hnh 3.8 c tnh FER ca h thng BPSK Alamouti vi 1 v 2 anten thu trn knh
fading Rayleigh chm 58 iv xiii
Hnh 3.9 c tnh FER ca h thng QPSK Alamouti vi 1 v 2 anten thu trn knh
fading Rayleigh chm 59 iv xiii

iv
N TT NGHIP
Hnh 3.11 S khi ca b m ha ST Alamouti 62 iv xiii
Hnh 3.14 c tnh BER ca h thng BPSK Alamouti vi 2 v 1 anten thu trn
knh fading Rayleigh chm 70 iv xiii
knh fading Rayleigh chm 73 iv xiv
Hnh 3.17 c tnh m STBC, STBC+TCM, STTC s dng m 4 v 8 trng 75 iv xiv
thi vi 2 anten pht, 3 anten thu (IEEE, 2001) 75 v xiv
DANH MC HNH V viii xiv
LI M U 1 xiv
NAM 1 xiv
1.1 Gii thiu v cc h thng thng tin di ng 1 xiv
1.2 Cng ngh thng tin di ng tng lai 6 xiv
Hnh 1.1 Nng lc ca cc h thng 3G m rng. 8 xiv
nhau 9 xiv
Hnh 1.3 Nhng vn k thut lin quan n cng ngh v tuyn 11 xiv
Hnh 1.4 Cu hnh h thng 4G 15 xiv
Hnh 1.5 Lin lc thng qua cc kt ni multi-hop 16 xiv
Chng 2 M HA KNH TRONG THNG TIN DI NG 20 xiv
2.1 Qu trnh m ha v nguyn l 20 xiv
Hnh 2.1 Qu trnh m ha trong h thng truyn thng s 21 xiv
2.2 Vai tr ca m ha 22 xiv

v
N TT NGHIP
2.3 Cc phng php m ha knh trong h thng 3G 23 xiv
Hnh 2.2 M ha khi 24 xiv
Hnh 2.3 B m c tnh h thng v khng h thng 25 xiv
Hnh 2.4 B m ha xon t l 1/3 27 xv
Hnh 2.5 B m ha Turbo 29 xv
Hnh 2.6 B gii m Turbo 30 xv
Hnh 2.7 S khi ca mt h thng MIMO 37 xv
2.6 Kt lun chng 39 xv
3.1 Phng php m ha khng gian - thi gian 40 xv
Hnh 3.1 Mt m hnh h thng bng tn gc 41 xv
Hnh 3.2 S m li 47 xv
Hnh 3.3 B m li k=1, K=3 v n=2 47 xv
Hnh 3.4 Li m v s trng thi vi k=1, K=3 v n=2 48 xv
Hnh 3.5 S khi ca b m ha STTC 50 xv
Hnh 3.6 ng bin gia tiu chun TSC v tiu chun vt 54 xv
Hnh 3.7 B m ha STTC vi 4-PSK 55 xv
fading Rayleigh chm 58 xv
fading Rayleigh chm 59 xv
Hnh 3.11 S khi ca b m ha ST Alamouti 62 xv
knh fading Rayleigh chm 70 xv

vi
N TT NGHIP
knh fading Rayleigh chm 73 xv
Hnh 3.17 c tnh m STBC, STBC+TCM, STTC s dng m 4 v 8 trng 75 xv
thi vi 2 anten pht, 3 anten thu (IEEE, 2001) 75 xvi
LI M U 1
NAM 1
1.1 Gii thiu v cc h thng thng tin di ng 1
1.2 Cng ngh thng tin di ng tng lai 6
Hnh 1.1 Nng lc ca cc h thng 3G m rng. 8
nhau 9
Hnh 1.3 Nhng vn k thut lin quan n cng ngh v tuyn 11
Hnh 1.4 Cu hnh h thng 4G 15
Hnh 1.5 Lin lc thng qua cc kt ni multi-hop 16
Chng 2 M HA KNH TRONG THNG TIN DI NG 20
2.1 Qu trnh m ha v nguyn l 20
Hnh 2.1 Qu trnh m ha trong h thng truyn thng s 21
2.2 Vai tr ca m ha 22
2.3 Cc phng php m ha knh trong h thng 3G 23
Hnh 2.2 M ha khi 24
Hnh 2.3 B m c tnh h thng v khng h thng 25
Hnh 2.4 B m ha xon t l 1/3 27

vii
N TT NGHIP
Hnh 2.5 B m ha Turbo 29
Hnh 2.6 B gii m Turbo 30
Hnh 2.7 S khi ca mt h thng MIMO 37
2.6 Kt lun chng 39
3.1 Phng php m ha khng gian - thi gian 40
Hnh 3.1 Mt m hnh h thng bng tn gc 41
Hnh 3.2 S m li 47
Hnh 3.3 B m li k=1, K=3 v n=2 47
Hnh 3.4 Li m v s trng thi vi k=1, K=3 v n=2 48
Hnh 3.5 S khi ca b m ha STTC 50
Hnh 3.6 ng bin gia tiu chun TSC v tiu chun vt 54
Hnh 3.7 B m ha STTC vi 4-PSK 55
fading Rayleigh chm 58
fading Rayleigh chm 59
Hnh 3.11 S khi ca b m ha ST Alamouti 62
knh fading Rayleigh chm 70
knh fading Rayleigh chm 73
Hnh 3.17 c tnh m STBC, STBC+TCM, STTC s dng m 4 v 8 trng 75
thi vi 2 anten pht, 3 anten thu (IEEE, 2001) 75

viii
N TT NGHIP
DANH MC T VIT TT
3G Third generation Th h th 3
4G Fourth generation Th h th 4
A
ARM Adaptive multi rate Tc a thch ng
ARQ Automatic repeat request Yu cu lp li t ng
AWGN Additive white Gaussian noise Tp m Gaussian trng cng
B
BER Bit error rate T l li bit
BPSK Binary phase shift keying Kho dch pha nh phn
C
CDMA Code division multiple access a truy cp phn chia theo m
CRC Cyclic redundancy check Kim tra d chu trnh
CSI Channel state information Thng tin trng thi knh
D
DAB Digital audio broadcasting Pht thanh s
DPSK Differential phase shift keying Kho dch pha vi sai
DVB Digital video broadcasting Truyn hnh s
E
EXIT Extrinsic information transfer Chuyn giao thng tin ngoi
F
FEC Forward error correction Sa li trc
FER Frame error rate T l li khung
G
GPRS General packet radio services Dch v v tuyn gi chung
H
HSPA High speed packet access a truy cp gi tc cao
I
IEEE Institute of Electrical and
Electronic Engineers
Vin nghin cu k thut in v
in t
i.i.d Independent identically S phn b c lp nhau

ix
N TT NGHIP
distributed
L
LLR Log-likelihood ratio T l on cc i
LOS Line-of-sight Nhn thng
LTE Long term evolution S pht trin trong tng lai
LST Layered space-time Tng khng gian thi gian
M
MAP Max a posteriori Gi tr cui ln nht
MC-CDMA MultiCarrier Code Division
Multiple Access
a truy nhp phn chia theo m iu
ch a sng mang
MIMO Multiple-input Multiple-output Nhiu anten ra, nhiu anten vo
MLSE Maximum likelihood sequence
estimator
Kh nng ging nht
MMS Multimedia messages service Dch v tin nhn a phng tin
MMSE Minimum mean square error Li bnh phng trung bnh nh
nht
MMS Maximal ratio combining Kt hp t l ti a
N
NLOS Non line of sight Khut
O
OFDMA Othogonal frequency division
multiple access
a truy nhp phn chia tn s trc
giao
P
PCBC Parallel concatenated block
coder
M khi kt ni song song
PCCC Parallel concatenated
convolutional coder
M xon kt ni song song
PDF Probability density function Hm mt xc sut
PSF Phase shift keying iu ch kho dch pha
Q
QAM Quadrature amplitude
modulation
iu ch bin cu phng
QPSK Quadrature phase-shift keying Kho dch pha cu phng
QoS Quality of service Cht lng dch v

x
N TT NGHIP
S
SER Symbol error rate T l li h thng
SCBC Serial concatenated block coder M khi theo th t ni tip
SCCC Serial concatenated
convolutional coder
M xon theo th t ni tip
SNR Signal to noise ratio T s tn hiu trn tp m
S/P Serial-to-parallel Ni tip/song song
ST Space-time Khng gian thi gian
STC Space-time code M khng gian thi gian
SCBC Space-time block codes M khi khng gian thi gian
STTC Space-time trellis code M ho li khng gian thi gian
SVD Singular value decomposition Phn tch gi tr ring
T
TCM Trellis coded modulation iu ch m trellis
U
UE User equipment Thit b ngi dung
UMB Ultra Mobile Broadband Di ng bng tn siu rng
UMTS Universal mobile
telecommunication systems
H thng vin thng di ng ton
cu
UTRAN Universal terrestrial radio access
network
Mng truy nhp v tuyn mt t
ton cu
W
WCDMA Wideband code division access a truy nhp phn chia theo m
bng rng

xi
N TT NGHIP
DANH MC HNH V
Nguyn Th Thu Hng.............ii
MC LC.............................................................................................................iii
Nguyn Th Thu Hng ii.........iii
MC LC iii.........................................................................................................iii
DANH MC HNH V xii......................................................................................iii
Nguyn Th Thu Hng ii xii....iii
MC LC iii xii....................................................................................................iii
Nguyn Th Thu Hng ii iii xii iii
MC LC iii iii xii................................................................................................iii
DANH MC HNH V viii iii xii............................................................................iii
LI M U 1 iii xii..............................................................................................iii
NAM 1 iii xii.............................................................................................................iii
1.1 Gii thiu v cc h thng thng tin di ng 1 iii xii........................................iii
1.2 Cng ngh thng tin di ng tng lai 6 iii xii..................................................iii
Hnh 1.1 Nng lc ca cc h thng 3G m rng. 8 iii xii....................................iii
nhau 9 iii xii.............................................................................................................iii
Hnh 1.3 Nhng vn k thut lin quan n cng ngh v tuyn 11 iii xii........iii
Hnh 1.4 Cu hnh h thng 4G 15 iii xii...............................................................iii
Hnh 1.5 Lin lc thng qua cc kt ni multi-hop 16 iii xii...................................iii

xii
N TT NGHIP
Chng 2 M HA KNH TRONG THNG TIN DI NG 20 iii xii.........iii
2.1 Qu trnh m ha v nguyn l 20 iii xii............................................................iii
Hnh 2.1 Qu trnh m ha trong h thng truyn thng s 21 iii xii..................iv
2.2 Vai tr ca m ha 22 iii xii..............................................................................iv
2.3 Cc phng php m ha knh trong h thng 3G 23 iii xii.............................iv
Hnh 2.2 M ha khi 24 iii xiii..............................................................................iv
Hnh 2.3 B m c tnh h thng v khng h thng 25 iii xiii.............................iv
Hnh 2.4 B m ha xon t l 1/3 27 iv xiii...........................................................iv
Hnh 2.5 B m ha Turbo 29 iv xiii......................................................................iv
Hnh 2.6 B gii m Turbo 30 iv xiii......................................................................iv
Hnh 2.7 S khi ca mt h thng MIMO 37 iv xiii.........................................iv
2.6 Kt lun chng 39 iv xiii.................................................................................iv
3.1 Phng php m ha khng gian - thi gian 40 iv xiii.....................................iv
Hnh 3.1 Mt m hnh h thng bng tn gc 41 iv xiii..........................................iv
Hnh 3.2 S m li 47 iv xiii..............................................................................iv
Hnh 3.3 B m li k=1, K=3 v n=2 47 iv xiii......................................................iv
Hnh 3.4 Li m v s trng thi vi k=1, K=3 v n=2 48 iv xiii.....................iv
Hnh 3.5 S khi ca b m ha STTC 50 iv xiii...............................................iv
Hnh 3.6 ng bin gia tiu chun TSC v tiu chun vt 54 iv xiii.................iv
Hnh 3.7 B m ha STTC vi 4-PSK 55 iv xiii......................................................iv
fading Rayleigh chm 58 iv xiii................................................................................iv

xiii
N TT NGHIP
fading Rayleigh chm 59 iv xiii................................................................................iv
Hnh 3.11 S khi ca b m ha ST Alamouti 62 iv xiii.................................v
knh fading Rayleigh chm 70 iv xiii........................................................................v
knh fading Rayleigh chm 73 iv xiv.........................................................................v
Hnh 3.17 c tnh m STBC, STBC+TCM, STTC s dng m 4 v 8 trng 75 iv xiv
...................................................................................................................................v
thi vi 2 anten pht, 3 anten thu (IEEE, 2001) 75 v xiv..........................................v
DANH MC HNH V viii xiv.................................................................................v
LI M U 1 xiv...................................................................................................v
NAM 1 xiv..................................................................................................................v
1.1 Gii thiu v cc h thng thng tin di ng 1 xiv.............................................v
1.2 Cng ngh thng tin di ng tng lai 6 xiv.......................................................v
Hnh 1.1 Nng lc ca cc h thng 3G m rng. 8 xiv.........................................v
nhau 9 xiv..................................................................................................................v
Hnh 1.3 Nhng vn k thut lin quan n cng ngh v tuyn 11 xiv.............v
Hnh 1.4 Cu hnh h thng 4G 15 xiv.....................................................................v
Hnh 1.5 Lin lc thng qua cc kt ni multi-hop 16 xiv........................................v
Chng 2 M HA KNH TRONG THNG TIN DI NG 20 xiv..............v

xiv
N TT NGHIP
2.1 Qu trnh m ha v nguyn l 20 xiv.................................................................v
Hnh 2.1 Qu trnh m ha trong h thng truyn thng s 21 xiv......................v
2.2 Vai tr ca m ha 22 xiv...................................................................................v
2.3 Cc phng php m ha knh trong h thng 3G 23 xiv.................................vi
Hnh 2.2 M ha khi 24 xiv...................................................................................vi
Hnh 2.3 B m c tnh h thng v khng h thng 25 xiv.................................vi
Hnh 2.4 B m ha xon t l 1/3 27 xv.................................................................vi
Hnh 2.5 B m ha Turbo 29 xv...........................................................................vi
Hnh 2.6 B gii m Turbo 30 xv...........................................................................vi
Hnh 2.7 S khi ca mt h thng MIMO 37 xv..............................................vi
2.6 Kt lun chng 39 xv.......................................................................................vi
3.1 Phng php m ha khng gian - thi gian 40 xv..........................................vi
Hnh 3.1 Mt m hnh h thng bng tn gc 41 xv...............................................vi
Hnh 3.2 S m li 47 xv...................................................................................vi
Hnh 3.3 B m li k=1, K=3 v n=2 47 xv...........................................................vi
Hnh 3.4 Li m v s trng thi vi k=1, K=3 v n=2 48 xv..........................vi
Hnh 3.5 S khi ca b m ha STTC 50 xv....................................................vi
Hnh 3.6 ng bin gia tiu chun TSC v tiu chun vt 54 xv.......................vi
Hnh 3.7 B m ha STTC vi 4-PSK 55 xv............................................................vi
fading Rayleigh chm 58 xv.....................................................................................vi

xv
N TT NGHIP
fading Rayleigh chm 59 xv.....................................................................................vi
Hnh 3.11 S khi ca b m ha ST Alamouti 62 xv......................................vi
knh fading Rayleigh chm 70 xv............................................................................vi
knh fading Rayleigh chm 73 xv...........................................................................vii
Hnh 3.17 c tnh m STBC, STBC+TCM, STTC s dng m 4 v 8 trng 75 xvvii
thi vi 2 anten pht, 3 anten thu (IEEE, 2001) 75 xvi...........................................vii
LI M U 1.......................................................................................................vii
NAM 1.....................................................................................................................vii
1.1 Gii thiu v cc h thng thng tin di ng 1.................................................vii
1.2 Cng ngh thng tin di ng tng lai 6...........................................................vii
Hnh 1.1 Nng lc ca cc h thng 3G m rng. 8.............................................vii
nhau 9......................................................................................................................vii
Hnh 1.3 Nhng vn k thut lin quan n cng ngh v tuyn 11................vii
Hnh 1.4 Cu hnh h thng 4G 15........................................................................vii
Hnh 1.5 Lin lc thng qua cc kt ni multi-hop 16............................................vii
Chng 2 M HA KNH TRONG THNG TIN DI NG 20..................vii
2.1 Qu trnh m ha v nguyn l 20.....................................................................vii
Hnh 2.1 Qu trnh m ha trong h thng truyn thng s 21..........................vii

xvi
N TT NGHIP
2.2 Vai tr ca m ha 22.......................................................................................vii
2.3 Cc phng php m ha knh trong h thng 3G 23......................................vii
Hnh 2.2 M ha khi 24........................................................................................vii
Hnh 2.3 B m c tnh h thng v khng h thng 25......................................vii
Hnh 2.4 B m ha xon t l 1/3 27....................................................................vii
Hnh 2.5 B m ha Turbo 29..............................................................................viii
Hnh 2.6 B gii m Turbo 30..............................................................................viii
Hnh 2.7 S khi ca mt h thng MIMO 37.................................................viii
2.6 Kt lun chng 39.........................................................................................viii
3.1 Phng php m ha khng gian - thi gian 40.............................................viii
Hnh 3.1 Mt m hnh h thng bng tn gc 41.................................................viii
Hnh 3.2 S m li 47.....................................................................................viii
Hnh 3.3 B m li k=1, K=3 v n=2 47.............................................................viii
Hnh 3.4 Li m v s trng thi vi k=1, K=3 v n=2 48.............................viii
Hnh 3.5 S khi ca b m ha STTC 50.......................................................viii
Hnh 3.6 ng bin gia tiu chun TSC v tiu chun vt 54.........................viii
Hnh 3.7 B m ha STTC vi 4-PSK 55..............................................................viii
fading Rayleigh chm 58........................................................................................viii
fading Rayleigh chm 59........................................................................................viii
Hnh 3.11 S khi ca b m ha ST Alamouti 62........................................viii

xvii
N TT NGHIP
knh fading Rayleigh chm 70...............................................................................viii
knh fading Rayleigh chm 73...............................................................................viii
Hnh 3.17 c tnh m STBC, STBC+TCM, STTC s dng m 4 v 8 trng 75. viii
thi vi 2 anten pht, 3 anten thu (IEEE, 2001) 75...............................................viii
DANH MC HNH V .......................................................................................... xii
LI M U ............................................................................................................ 1
NAM .......................................................................................................................... 1
1.1 Gii thiu v cc h thng thng tin di ng ...................................................... 1
1.2 Cng ngh thng tin di ng tng lai ................................................................ 6
Hnh 1.1 Nng lc ca cc h thng 3G m rng. ................................................. 8
nhau .......................................................................................................................... 9
Hnh 1.3 Nhng vn k thut lin quan n cng ngh v tuyn ..................... 11
Hnh 1.4 Cu hnh h thng 4G ............................................................................. 15
Hnh 1.5 Lin lc thng qua cc kt ni multi-hop ................................................. 16
Chng 2 M HA KNH TRONG THNG TIN DI NG ....................... 20
2.1 Qu trnh m ha v nguyn l ......................................................................... 20
Hnh 2.1 Qu trnh m ha trong h thng truyn thng s ............................... 21
2.2 Vai tr ca m ha ........................................................................................... 22
2.3 Cc phng php m ha knh trong h thng 3G .......................................... 23

xviii
N TT NGHIP
Hnh 2.2 M ha khi ............................................................................................ 24
Hnh 2.3 B m c tnh h thng v khng h thng ........................................... 25
Hnh 2.4 B m ha xon t l 1/3 ......................................................................... 27
Hnh 2.5 B m ha Turbo .................................................................................... 29
Hnh 2.6 B gii m Turbo .................................................................................... 30
Hnh 2.7 S khi ca mt h thng MIMO ....................................................... 37
2.6 Kt lun chng ............................................................................................... 39
3.1 Phng php m ha khng gian - thi gian ................................................... 40
Hnh 3.1 Mt m hnh h thng bng tn gc ....................................................... 41
Hnh 3.2 S m li ........................................................................................... 47
Hnh 3.3 B m li k=1, K=3 v n=2 ................................................................... 47
Hnh 3.4 Li m v s trng thi vi k=1, K=3 v n=2 ................................... 48
Hnh 3.5 S khi ca b m ha STTC ............................................................. 50
Hnh 3.6 ng bin gia tiu chun TSC v tiu chun vt ............................... 54
Hnh 3.7 B m ha STTC vi 4-PSK .................................................................... 55
fading Rayleigh chm .............................................................................................. 58
fading Rayleigh chm .............................................................................................. 59
Hnh 3.11 S khi ca b m ha ST Alamouti .............................................. 62
knh fading Rayleigh chm ..................................................................................... 70

xix
N TT NGHIP
knh fading Rayleigh chm ..................................................................................... 73
Hnh 3.17 c tnh m STBC, STBC+TCM, STTC s dng m 4 v 8 trng ....... 75
thi vi 2 anten pht, 3 anten thu (IEEE, 2001) ..................................................... 75

xx
N TT NGHIP
LI M U
1.Tnh cp thit ca ti: Cc h thng thng tin di ng ang bng n c trn
th gii v c Vit Nam.Trc yu cu ngy cng cao ca ngi s dng thng tin di
ng v cht lng v tnh a dng ca dch v v c bit l cc dch v truyn d liu
tc cao v a phng tin,vic nghin cu, ng dng cc cng ngh v k thut tin
tin p ng nhu cu ny lun l mt i hi cp thit. Trc s pht trin v cng
mnh m ca cc dch v s liu, trc xu hng tch hp v IP ho t ra cc yu
cu mi i vi cng nghip Vin Thng di ng. Mng thng tin di ng th h ba ra
i khc phc c cc nhc im ca cc mng thng tin di ng th h trc .
Tuy nhin, mng di ng ny cng c mt s nhc im nh: Tc truyn d liu
ln nht l 2Mbps, vn cha p ng c yu cu ngy cng cao ca ngi dng, kh
nng p ng cc dch v thi gian thc nh hi ngh truyn hnh l cha cao, rt kh
trong vic download cc file d liu ln,cha p ng c cc yu cu ca ngi s
dng.
Trong bi cnh ngi ta chuyn hng sang nghin cu h thng thng tin
di ng mi c tn gi l 4G. Nghin cu v m ho knh l ti quan trng v c
ngha nht l trong thi k cc h thng vin thng ang tin n 4G. S ra i ca h
thng ny m ra kh nng tch hp tt c cc dch v, cung cp bng thng rng, dung
lng ln, truyn dn d liu tc cao, cung cp cho ngi s dng nhng hnh nh
video mu cht lng cao, cc tr chi ho 3D linh hot, cc dich v m thanh s.
Vic pht trin cng ngh giao thc u cui dung lng ln, cc dich v gi d liu tc
cao, cng ngh da trn nn tng phn mm cng cng mang n cc chng trnh
ng dng download, cng ngh truy nhp v tuyn a mode, v cng ngh m ho
media cht lng cao trn nn cc mng di ng.

1
N TT NGHIP
2.Tnh hnh nghin cu: Hin nay Viettel a vo s dng GPRS p ng
nhu cu s dng cc dch v d liu ngy cng cao ca cc thu bao. Cc dch v ch
yu ca GPRS nh: WAP, truy nhp Internet c hai phng thc l truy nhp gin tip
v truy nhp trc tip, dch v nhn tin a phng tin, video, xem cc on phim ti v,
xem video trc tuyn. Ngoi ra cn c dch v thng mi in t di ng, dch v ngn
hng, qung co trn in thoi di ngdo gi cc cn cao nn cc loi bao c thu
nhp trung bnh v cao.
3.Mc ch nghin cu: Mc ch ca vic m ha knh l nhm chun b cc
lung d liu sao cho vi nhng li xy ra trong qu trnh truyn, cc my thu chc chn
c th pht hin ra v chun ha li c.Cng vic ny c thc hin hon ton thng
qua qu trnh tnh ton s liu d phn t cc lung d liu.Trong khi m ha ngun
hng ti loi b cc d liu d tha, th m ha knh lm tng tng dung lng d liu
s truyn dn ng tin cy hn v ci thin cht lng dch v .Cng ngh truyn
thng di ng th h th 4 l thc hin truyn thng v tuyn tc cao bng vi tc
trong cc h thng truyn dn si quang hin ti. Tuy cc h thng truyn thng di
ng 4G c d on s c p dng trong tng lai, nhng cc cng ngh tin thn
v cc dch v ca n hin c gii thiu. Vi vic tch hp Internet v cc ng
dng a truyn thng trong cc h thng vin thng th h 4G, yu cu v cc dch v
truyn thng tc cao bng rng ngy cng tng. Nhng v ph tn s sn c b gii
hn nn t c tc d liu cao hn th ch cn cch nghin cu v a ra nhng
k thut x l tn hiu mi, hiu qu hn.
4. Nhim v nghin cu: Nhng nghin cu gn y v l thuyt thng tin
cho thy rng cc knh v tuyn c dung lng ln c th t c trong h thng
MIMO (multiple-input multiple-output). Knh MIMO c xy dng vi nhiu anten
phn t c hng pht ln hng thu. M khng gian-thi gian (space-time coding) l
mt tp hp cc k thut sp xp tn hiu thc t nhm t c mc ch l tin n

2
N TT NGHIP
gn gii hn dung lng l thuyt ca cc knh MIMO. Nn tng ca m ha khng
gian-thi gian c t ra bi Tarokh, Seshadri v Calderbank vo nm 1998. s kt hp
gia m ha khng gian-thi gian v x l tn hiu MIMO sm tr thnh mt phm
vi nghin cu si ni nht trong truyn thng v tuyn. Lc ny, nhim v chnh ca
nghin cu l trit nhiu ti my thu.
5. Phng php nghin cu: M ha khng gian thi gian da vo mi quan h
tng quan gia cc tn hiu c pht c 2 min khng gian v thi gian. Bng
phng php ny, ta s t c ng thi li phn tp v li m ha, cng c
ngha l t c hiu qu ph tn cao. Cc nghin cu ban u tp trung vo vic thit
k mi quan h ph thuc khng gian-thi gian tn hiu pht vi mong mun t c
li phn tp v li m ha cao. Nhng gn y, cc nghin cu li chuyn sang
hng tn hiu ch c m ha trong min thi gian v c pht bi nhiu anten c
lp.
6. Kt qu t c ca ti : l nn tng so snh vi cc m ha knh s
dng trong thng tin di ng 3G thy c nhng u im ni bt, tnh cp thit ca
qu trnh hng ti h thng thng tin di ng 4G, cho mt nn cng ngh k thut pht
trin v ang ngy mt i ln khng ngng.
7. Ni dung ti: Ni dung ti bao gm 3 chng :
- Chng 1: S pht trin ca h thng thng tin di ng ca Vit Nam.
- Chng 2: M ha knh trong thng tin di ng
- Chng 3: Cc phng php m ha knh xut s dng trong 4G.

Xin chn thnh cm n !

3
N TT NGHIP
Chng 1 S PHT TRIN CA H THNG THNG TIN DI NG
VIT NAM
1.1 Gii thiu v cc h thng thng tin di ng
1.1.1 Mng thng tin u tin 1G
H thng thng tin di ng 1G hay cn gi l s khi u gin n. 1G l ch vit
tt ca cng ngh in thoi khng dy th h u tin (1st Generation). N l h thng
giao tip thng tin qua kt ni tn hiu analog c gii thiu ln u tin vo nhng
nm u thp nin 80. N s dng cc ng-ten thu pht sng gn ngoi, kt ni theo tn
hiu analog ti cc trm thu pht sng v nhn tn hiu x l thoi thng qua cc module
gn trong my di ng.
Mc d l th h mng di ng u tin vi tn s ch t 150MHz nhng mng 1G
cng phn ra kh nhiu chun kt ni theo tng phn vng ring trn th gii. Mt trong
nhng cng ngh 1G ph bin l NMT (Nordic Mobile Telephone) c s dng cc
nc Bc u, Ty u v Nga. Cng c mt s cng ngh khc nh AMPS (Advanced
Mobile Phone Sytem h thng in thoi di ng tin tin) c s dng M v c;
TACS (Total Access Communication Sytem h thng giao tip truy cp tng hp)
c s dng Anh, C-45 Ty c, B o Nha v Nam Phi, Radiocom 2000
Php; v RTMI Italia.
1.1.2 Mng thng tin di ng th h 2G
1.1.2.1 Cng ngh s dng
L th h kt ni thng tin di ng mang tnh ci cch cng nh khc hon ton so
vi th h u tin. Vi cng ngh GSM , n s dng cc tn hiu k thut s thay cho
tn hiu analog ca th h 1G v c p dng ln u tin ti Phn Lan bi Radiolinja
(hin l nh cung cp mng con ca tp on Elisa Oyj) trong nm 1991. Mng 2G mang

1
N TT NGHIP
ti cho ngi s dng di ng 3 li ch tin b trong sut mt thi gian di: m ho d
liu theo dng k thut s, phm vi kt ni rng hn 1G v c bit l s xut hin ca
tin nhn dng vn bn n gin SMS. Theo , cc tin hiu thoi khi c thu nhn s
uc m ho thnh tn hiu k thut s di nhiu dng m hiu (codecs), cho php
nhiu gi m thoi c lu chuyn trn cng mt bng thng, tit kim thi gian v chi
ph. Song song , tn hiu k thut s truyn nhn trong th h 2G to ra ngun nng
lng sng nh hn v s dng cc chip thu pht nh hn, tit kim din tch bn trong
thit b hn.
Nhng cng ngh 2G c chia lm hai dng chun : TDMA (Time Divison
Mutiple Access : a truy cp phn chia theo thi gian), v CDMA ( Code Divison
Multple Access : a truy cp phn chia theo m), ty thuc vo hnh thc ghp knh
c s dng
Cc chun cng ngh ch yu ca 2G bao gm:
- GSM (thuc TDMA) c ngun gc t chu u, nhng c s dng trn tt
c cc quc gia 6 lc a. Ngy nay, cng ngh GSM vn cn c s dng vi 80%
in thoi di ng trn th gii.
- IS-95 cn c gi l aka cdmaOne (thuc CDMA, thng c gi ngn gn
l CDMA ti M) c s dng ch yu l chu M v mt s vng chu . Ngy
nay, nhng thu bao s dng chun ny chim khong 17% trn ton th gii. Hin ti,
cc nc Mexico, n , c v Hn Quc c rt nhiu nh cung cp mng CDMA
chuyn sang cung cp mng GSM.
- PDC (thuc TDMA) l mng t nhn, ti Japan.
- IS-136 aka D-AMPS (thuc TDMA thng c gi tt l TDMA ti M)
tng l mng ln nht trn th trng M nay chuyn sang GSM.
- iDEN (nn tng TDMA) s dng bi Nextel ti Hoa K v Telus Mobility ti
Canada.
1.1.2.2 c tnh ca mng

2
N TT NGHIP
cng ngh 2G tn hiu k thut s c s dng trao i gia in thoi v
cc thp pht sng, lm tng hiu qu trn 2 phng din chnh :
- Th nht, d liu s ca ging ni c th c nn v ghp knh hiu qu hn
so vi m ha Analog nh s dng nhiu hnh thc m ha, cho php nhiu cuc gi
cng c m ha trn mt di bng tn.
- Th hai, h thng k thut s c thit k gim bt nng lng sng radio pht
t in thoi. Nh vy, c th thit k in thoi 2G nh gn hn; ng thi gim chi
ph u t nhng thp pht sng.
Hn na, mng 2G tr nn ph bin cng do cng ngh ny c th trin khai mt
s dch v d liu nh Email v SMS. ng thi, mc bo mt c nhn cng cao hn
so vi 1G.
Tuy nhin, h thng mng 2G cng c nhng nhc im, v d, nhng ni dn
c tha tht, sng k thut s yu c th khng ti c cc thp pht sng. Ti nhng
a im nh vy, cht lng truyn sng cng nh cht lng cuc gi s b gim ng
k.
1.1.3 Mng thng tin di ng th h 2.5G
2,5G chnh l bc m gia 2G vi 3G trong cng ngh in thoi khng dy.
Ch s 2.5G chnh l biu tng cho vic mng 2G c trang b h thng chuyn mch
gi bn cnh h thng chuyn mch theo knh truyn thng. N khng c nh ngha
chnh thc bi bt k nh mng hay t chc no v ch mang mc ch duy nht l tip
th cng ngh mi theo mng 2G.
Mng 2.5G cung cp mt s li ch tng t mng 3G v c th dng c s h tng
c sn ca cc nh mng 2G trong cc mng GSM v CDMA. V tin b duy nht chnh

3
N TT NGHIP
l GPRS - cng ngh kt ni trc tuyn, lu chuyn d liu c dng bi cc nh cung
cp dch v vin thng GSM. Bn cnh , mt vi giao thc, chng hn nh EDGE cho
GSM v CDMA2000 1x-RTT cho CDMA, c th t c cht lng gn nh cc dch
v c bn 3G (bi v chng dng mt tc truyn d liu chung l 144 kbit/s), nhng
vn c xem nh l dch v 2.5G (hoc l nghe c v phc tp hn l 2.75G) bi v n
chm hn vi ln so vi dch v 3G thc s.
* EDGE (Enhanced Data Rates for GSM Evolution), hay cn gi l EGPRS, l
mt cng ngh di ng c nng cp t GPRS - cho php truyn d liu vi tc c
th ln n 384 kbit/s dnh cho ngi dng c nh hoc di chuyn chm, 144kbit/s cho
ngi dng di chuyn vi tc cao. Trn ng tin n 3G, EDGE c bit n nh
l cng ngh 2.75G. Thc t bn cnh iu ch GMSK, EDGE dng phng thc iu
ch 8-PSK tng tc d liu truyn. Chnh v th, trin khai EDGE, cc nh cung
cp mng phi thay i trm pht sng BTS cng nh l thit b di ng so vi mng
GPRS.
1.1.4 Mng thng tin di ng ng i 3G
L th h truyn thng di ng th ba, tin tin hn hn cc th h trc . N
cho php ngi dng di ng truyn ti c d liu thoi v d liu ngoi thoi (ti d
liu, gi email, tin nhn nhanh, hnh nh, m thanh, video clips...). ,). H thng 3G
yu cu mt mng truy cp radio hon ton khc so vi h thng 2G hin nay. Trong cc
dch v ca 3G, cuc gi video thng c m t nh mt dch v trng tm ca s
pht trin.
Cng ngh 3G cng c nhc n nh l mt chun IMT-2000 ca T chc Vin
thng Th gii (ITU). Ban u 3G c d kin l mt chun thng nht trn th gii,
nhng trn thc t, th gii 3G b chia thnh 4 phn ring bit:
- UMTS (W-CDMA)

4
N TT NGHIP
* UMTS (Universal Mobile Telecommunication System), da trn cng ngh truy
cp v tuyn W-CDMA, l gii php ni chung thch hp vi cc nh khai thc dch v
di ng (Mobile network operator) s dng GSM, tp trung ch yu chu u v mt
phn chu (trong c Vit Nam). UMTS c tiu chun ha bi t chc 3GPP,
cng l t chc chu trch nhim nh ngha chun cho GSM, GPRS v EDGE.
* FOMA, thc hin bi cng ty vin thng NTT DoCoMo Nht Bn nm 2001,
c coi nh l mt dch v thng mi 3G u tin. Tuy l da trn cng ngh W-
CDMA, nhng cng ngh ny vn khng tng thch vi UMTS (mc d c cc bc
tip hin thi thay i li tnh th ny).
- CDMA 2000
* L th h k tip ca cc chun 2G CDMA v IS-95. Cc xut ca
CDMA2000 c a ra bn tho v p dng bn ngoi khun kh GSM ti M, Nht
Bn v Hn Quc. CDMA2000 c qun l bi 3GPP2 mt t chc c lp vi
3GPP. V c nhiu cng ngh truyn thng khc nhau c s dng trong
CDMA2000 bao gm 1xRTT, CDMA2000-1xEV-DO v 1xEV-DV.
* CDMA 2000 cung cp tc d liu t 144 kbit/s ti trn 3 Mbit/s. Chun ny
c chp nhn bi ITU.
* Ngi ta cho rng s ra i thnh cng nht ca mng CDMA-2000 l ti
KDDI ca Nhn Bn, di thng hiu AU vi hn 20 triu thu bao 3G. K t nm
2003, KDDI nng cp t mng CDMA2000-1x ln mng CDMA2000-1xEV-DO vi
tc d liu ti 2.4 Mbit/s. Nm 2006, AU nng cp mng ln tc 3.6 Mbit/s. SK
Telecom ca Hn Quc a ra dch v CDMA2000-1x u tin nm 2000, v sau
l mng 1xEV-DO vo thng 2 nm 2002.
- TD-SCDMA
Chun c t c bit n hn l TD-SCDMA, c pht trin ring ti Trung
Quc bi cng ty Datang v Siemens.
- Wideband CDMA

5
N TT NGHIP
H tr tc gia 384 kbit/s v 2 Mbit/s. Giao thc ny c dng trong mt mng din
rng WAN, tc ti a l 384 kbit/s. Khi n dng trong mt mng cc b LAN, tc
ti a ch l 1,8 Mbit/s. Chun ny cng c cng nhn bi ITU.
Trong s cc dch v ca 3G, in thoi video thng c miu t nh l l c
u. Gi tn s cho cng ngh 3G rt t ti nhiu nc, ni m cc cuc bn u gi
tn s mang li hng t Euro cho cc chnh ph. Bi v chi ph cho bn quyn v cc tn
s phi trang tri trong nhiu nm trc khi cc thu nhp t mng 3G em li, nn mt
khi lng vn u t khng l l cn thit xy dng mng 3G. Nhiu nh cung cp
dch v vin thng ri vo kh khn v ti chnh v iu ny lm chm tr vic
trin khai mng 3G ti nhiu nc ngoi tr Nht Bn v Hn Quc, ni yu cu v bn
quyn tn s c b qua do pht trin h tng c s IT quc gia c t ln lm vn
u tin nht. V cng chnh Nht Bn l nc u tin a 3G vo khai thc thng
mi mt cch rng ri, tin phong bi nh mng NTT DoCoMo. Tnh n nm 2005,
khong 40% cc thu bao ti Nht Bn l thu bao 3G, v mng 2G ang dn dn i vo
lng qun trong tim thc cng ngh ti Nht Bn.
1.2 Cng ngh thng tin di ng tng lai
4G l cng ngh a phng tin di ng ca tng lai. y l cng ngh truyn
thng khng dy th h th 4, cho php truyn ti d liu vi tc ti a trong iu
kin l tng ti 1-1,5 GB/s. NTT Docomo xem 4G nh s m rng ca mng thng tin
di ng t bo 3G. Cc nghin cu u tin ca NTT DoCoMo cho bit, in thoi 4G
c th nhn d liu vi tc 100 Mbit/s khi di chuyn v ti 1 Gbit/s khi ng yn,
cng nh cho php ngi s dng c th ti v truyn ln cc hnh nh, video clips cht
lng cao. Mng in thoi 3G hin ti ca DoCoMo c tc ti l 384 Kbit/s v
truyn d liu ln vi tc 129 Kbit/s. NTT DoCoMo cng hy vng trong vng 2010 -
2012 s c th a mng 4G vo kinh doanh. .Quan im ny c xem nh l mt

6
N TT NGHIP
quan im tuyn tnh, trong mng 4G s c cu trc t bo c ci tin cung
ng tc ln trn 100 MB/s. Vi cch nhn nhn ny, 4G s chnh l mng 3G LTE,
UMB hay WiMAX 802.16m.
1.2.1 Hng n h thng 4G
Cc gi thit v tc d liu l mc ch cho s nghin cu v kho st trn cc
cng ngh c s cn thit thc hin vin cnh . Yu cu k thut h thng v thit
k tng lai s da vo cc kt qu ca s nghin cu v kho st ny. Do yu cu tc
d liu cao, ph tn b sung s cn cho cc kh nng mi ca h thng IMT-2000 m
rng. Cc mc tiu v tc d liu cho thy s tin b trong cng ngh v cc gi tr
ny c mong i s t c bi tin ca cng ngh trong khong thi gian nghin
cu v pht trin kh nng mi ca cc h thng IMT-2000 m rng.
Cng vi s pht trin trong tng lai ca IMT-2000 v cc h thng IMT-2000
m rng. S c mt mi quan h ngy cng tng gia vic truy nhp v tuyn v cc h
thng thng tin lin lc, v d nh mng WPAN, LAN, qung b s v truy nhp khng
dy c nh. Da vo cc yu cu v dch v c vch ra, d tnh lu lng v
cng ngh truy nhp v tuyn, ITU-R lm vic trn cu trc h thng tim nng, tng
ng t hnh 1.1 n hnh 1.3. Trong trng hp ny, tnh lu ng chm s c tnh
bng tc i b ( 3km/h), tnh lu ng trung bnh tng ng vi tc xe t trong
thnh ph ( 50-60km/h), lu ng nhanh tng ng vi tc trn ng cao tc hoc
xe la tc cao ( 60km/h n 250km/h hoc hn na).
lu ng v c bn cng lin quan n kch thc cell trong h thng t bo, cng
nh kh nng ca h thng. Ni chung, kch thc cell trong mt h thng t bo phi
ln hn mt lu ng cao no gim ti chuyn giao trong mng.

7
N TT NGHIP
Hnh 1.1 Nng lc ca cc h thng 3G m rng.

8
N TT NGHIP
Hnh 1.2 Mng tng lai thng nht, bao gm nhiu h thng truy nhp an xen nhau
T vin cnh ca ngy hm nay, ITU-R s bt u chun ha h thng, vi cc
bng tn c xc nh v bc u trin khai cc h thng IMT-2000 m rng sau
nm 2010. H thng truy nhp tng lai s bao gm nhng cng ngh truy nhp m
rng v sn c. Ngoi ra, cc cng ngh truy nhp v tuyn mi s t c tc d
liu cao cho truy nhp khng dy c tnh lu ng thp v cho trng hp t bo vi
tnh lu ng cao. Yu cu tc d liu cho trng hp t bo l mt thch thc ln
ca vin cnh cng ngh cng vi ph tn tng lai s c s dng.
1.2.2 Tm hiu s lc v h thng 4G
Vic tin n h thng thng tin di ng 4G c t ra gii quyt cc vn
vn cn tn ti h thng 3G v cng cung cp kh nng p ng rng cho cc dch
v mi, t thoi cht lng cao n truyn hnh phn gii cao, cho n cc knh v
tuyn tc d liu cao. Thut ng 4G c s dng vi mt ngha rng bao gm cc
loi khc nhau ca h thng truyn thng truy nhp v tuyn bng rng, khng ch ring
h thng in thoi t bo. Mt trong cc thut ng cng c dng miu t 4G l
MAGIC a truyn thng di ng (Mobile multimedia), mi lc mi ni (Anytime

9
N TT NGHIP
anywhere), h tr lu ng ton cu (Global mobility support), gii php v tuyn tch
hp (Integrated wireless solution), v dch v thu bao c nhn (Customized personal
service). H thng 4G khng ch s h tr cc dch v di ng th h sau m cn h tr
cho cc mng v tuyn c nh.
1.2.3 Mc tiu thit k h thng thng tin 4G
1.2.4.1 Thng tin bng rng
T trc n nay, lu lng trn mng thng tin di ng vn ch yu l lu lng
thoi. H thng th h 2G, h thng t bo s c nhn PDC (Personal Digital Cellular)
gii thiu cc dch v I-mode. Nhng dch v ang c ph bin hin nay nh: truy
cp Internet, thng mi in t, e-mail. Nhng dch v ny ch yu l thng tin d liu
da trn vn bn qua mng t bo. H thng IMT-2000 xut nhng dch v tc
cao t 64 n 384 kbit/s, v t l lu lng s liu trn thoi tng ln. Tuy nhin, s pht
trin mnh ca cc dch v bng rng nh ADSL (Asymmetric Digital Subscriber Line),
cc h thng truy nhp cp quang, cc mng LAN c quan, gia nh lm tng nhu cu
s dng cc dch v tng ng ca mng thng tin di ng.
1.2.4.2 Chi ph thp
Khi cc dch v bng rng pht trin, cc thu bao c th trao i rt nhiu loi
thng tin vi nhau, tuy nhin h li khng sn sng tr mt chi ph qu cao cho lng
thng tin trao i qu nhiu nh vy. V vy cn phi gim gi cc ca cc dch v
xung bng hoc thp hn gi cc ca cc dch v hin ti. H thng IMT-2000
gim mc cc tnh theo bt v a ra cc mc gi tng i thp, nhng h thng 4G
i hi mt knh bng thng rng vi mc gi thm ch thp hn mc gi theo bit m
IMT-2000 a ra.

10
N TT NGHIP
Hnh 1.3 Nhng vn k thut lin quan n cng ngh v tuyn
1.2.4.3 Vng ph sng rng
Mt trong nhng c tnh ca thng tin di ng l c mt khp mi ni mi lc.
Nhng kh nng ny cng l mt tiu ch quan trng cho s pht trin ca thng tin di
ng trong tng lai. Khi mt h thng mi u tin c gii thiu th ni chung rt
kh khn trong vic cung cp mt vng ph sng rng nh mng hin c, v khch hng
s khng mua cc thit b u cui mi nu h b gii hn vng ph sng
1.2.4.4 Dch v a dng v d s dng
i tng s dng thng tin di ng rt a dng v rt khc nhau. Trong tng lai,
chng ta hy vng c th nng cao phm cht v chc nng h thng c th cung cp
nhiu loi hnh dch v, khng ch l cc dch v thoi truyn thng m cn truyn cc
thng tin lin quan n tt c nm gic quan ca con ngi. V thu bao phi d dng s
dng cc dch v ny (d dng ci t, d dng kt ni, ).

11
N TT NGHIP
1.2.4.5 Tc truyn dn
i tng s dng thng tin di ng rt a dng v rt khc nhau. Trong tng lai,
chng ta hy vng c th nng cao phm cht v chc nng h thng c th cung cp
nhiu loi hnh dch v, khng ch l cc dch v thoi truyn thng m cn truyn cc
thng tin lin quan n tt c nm gic quan ca con ngi. V thu bao phi d dng s
dng cc dch v ny (d dng ci t, d dng kt ni, ).
Mc tiu thit k h thng p nhng yu cu trn y. Coi thng tin d liu v
video l dch v chnh, h thng 4G phi cung cp tc truyn dn cao hn vi dung
lng ln hn (c v s lng thu bao l lu lng) IMT-2000.
Hin nay, coi tc chnh l cht lng truyn dn, mng LAN t c tc t
10 n 100 Mbit/s, v tc ca mng ADSL cng t c 2-3 Mbit/s. Mc tiu thit
k h thng thng tin di ng l t tc xp x 100 Mbit/s i vi mi trng ngoi
tri v c Gbit/s vi mi trng trong nh. S khng c ch cho mng thng tin di ng
th h mi nu khng c tc ln hn t nht 10 ln tc hin ti ca IMT-2000.
m thng tin thi gian thc gia cc thit b u cui vi nhau th h thng mi cn
phi gim thi gian tr truyn dn xung di 50 ms. Gi s rng cc dch v trong
tng lai s da trn truyn dn IP (Internet Protocol), hiu qu truyn dn gi IP qua
mng v tuyn cng cn phi tnh n. H thng mi bn cnh vic nng cao dung
lng truyn dn phi m bo c vic gim chi ph. Chi ph tnh trn 1 bt truyn dn
phi gim xung bng 1/10 hoc 1/100 mc chi ph hin ti bng cch gim chi ph thit
b h tng, chi ph hot ng v chi ph xy dng. Mc tiu thit k c cp trn y
tp trung vo nhng dch v c phm cht tt hn cc dch v hin ti, v d dng s
dng. iu m nhng nh i tin phong trong th trng dch v 4G cn phi lu l
kh nng tch hp h thng LAN khng dy trong nh vi h thng hu tuyn v thc
hin trin khai cc dch v mi trong thi gian ngn.

12
N TT NGHIP
1.2.4 Nhng vn c bn trong cu hnh h thng 4G
Vn k thut cn thit i vi mng thng tin di ng th h 4G p ng
nhng yu cu c nu ra phn trn c trnh by trn hnh 1.7.
1.2.5.1. Dung lng ln v tc truyn dn cao
IMT-2000 trin khai a truy nhp theo m bng rng WCDMA (Wideband
Code Division Multiple Access) v t c tc 2Mbit/s vi bng tn c rng 5
MHz. Ngy nay, vic pht trin k thut iu ch v gii iu ch thch nghi a lp cho
php tc truyn dn t xp x 10 Mbit/s vi cng mt bng tn s dng. t c
tc truyn dn t 100 Mbit/s n 1 Gbit/s, chng ta cn phi s dng bng tn ln
hn v cc h thng truyn dn mi ph hp vi truyn dn tc cao.
i vi thng tin d liu, chng ta s cn h thng truy nhp v tuyn c th truyn
dn gi tin hiu qu. Tm quan trng ca vic ph sng trong nh thc y cc cng
ngh phi pht trin theo hng c th s dng cho c mi trng truyn sng trong nh
v ngoi tri. c c nhng bng tn rng cho truyn dn tc cao v p ng
nhu cu lu lng thoi ang tng cao, chng ta phi quan tm n cc bng tn mi, v
pht trin cc phn t mng cn thit nh cc b khuch i, cc b lc v tnh ton suy
hao truyn sng cho nhng bng tn ny. Cng vi vic nghin cu pht trin cc
gii php s dng hiu qu ti nguyn ph tn hn ch cng rt cn thit.
1.2.5.3 Kt ni mng da trn cng ngh IP
Mt bin php cho nhng thu bao s dng h thng mi khng gp phi vn
v vng ph sng l phi m bo cc thit b u cui mi phi h tr hot ng
trn c h thng c v h thng mi. Mt khc, chng ta phi tnh n kh nng roaming
quc t, mt thit b u cui phi c h tr hot ng trn nhiu h thng nh s
dng cng ngh SDR (Softwave Defined Radio). Vi cng ngh ny, thit b u cui c
th hot ng trn nhiu bng tn khc nhau ca cc quc gia v khu vc khc nhau.

13
N TT NGHIP
Hn na, mng thng tin di ng trong tng lai phi tch hp vi nhiu phng thc
truy nhp khc nhau, vi rt nhiu loi cell c cc kh nng kt ni lin mng da trn
cng ngh IP. Chnh v vy, kt ni lin mng v chuyn giao gia cc h thng truy
nhp l mt yu cu cn thit ngoi yu cu v kh nng chuyn giao v roaming ni b
v gia hai mng thng tin di ng vi nhau.
1.2.5.4 Cu hnh h thng da trn IP
H thng 4G phi c cu hnh kt ni vi mng IP, truyn dn hiu qu cc
gi IP, cng tn ti vi cc h thng truy nhp khc, linh hot khi a vo khai thc, c
kh nng m rng khi cn, Cc mng IP cng c th kt ni d dng hoc ph hp
vi cc h thng truy nhp v tuyn khc hn cc h thng 4G. im truy nhp v tuyn
4G (4G-AP-4G Access Point) s c kt ni vi mt b nh tuyn truy nhp AR
(Access Router) nh trn Hnh 1.4. 4G-AP c cc chc nng iu khin truyn dn v
tuyn, chuyn giao, cho php cc thit b di ng lin lc vi nhau da trn IP. Cc
4G-AP s c t tng ng vi cc cell ca chng. Khi mt thit b di ng di chuyn
gia cc cell, vic chuyn giao s c thc hin bng chuyn mch n gin gia cc
im truy nhp v cc vng v tuyn nu hai im 4G-AP kt ni vi cng mt AR. Nu
hai im 4G-AP thuc hai AR khc nhau th nh tuyn truyn dn gi tin trong mng IP
phi thay i tc th. Lit kt hot ng gia chuyn mch 4G-IP v nh tuyn mng IP
ng mt vai tr rt quan trng i vi qu trnh chuyn giao. i vi chuyn giao gia
mt 4G-AP v mt AP ca h thng khc, thit b di ng phi c chc nng truy nhp
c hai mng. Chuyn giao s c thc hin bng vic theo di v so snh gia cc h
thng khc nhau la chn c mt h thng ph hp.

14
N TT NGHIP
Hnh 1.4 C u hnh h th ng 4G
1.2.5.5 Phn loi v cu hnh cell theo mi trng truyn dn
H thng 4G c cell ngoi tri, trong nh, trong phng tin di chuyn, nh trn
Hnh 3. Nhng cell ngoi tri c vng ph sng rng, cho php cc thit b u cui
ang di chuyn vi tc cao trao i thng tin vi tc cao. Vng ph trong nh
c thc hin bi cc indoor AP. Cc Indoor AP c thit k khng ch gip trao i
thng tin tc cao v hot ng n gin m cn p ng nhng yu cu ca mt
mng LAN v tuyn tng lai.
Ngoi ra, cc cell trong phng tin giao thng di chuyn nh xe but, tu ho
(c gi l cc cell/mng di ng) c phc v bi mt b nh tuyn di ng MR
(Mobile Router). MR c chc nng chuyn tip tn hiu gia trm gc v thit b u
cui trn phng tin, nn nhng thit b u cui ny khng lin lc trc tip vi trm

15
N TT NGHIP
gc nh thng thng. Cu hnh ny c thit k t c hiu qu v cng sut
pht ca thit b u cui, tc truyn dn, ln ca tn hin iu khin. Kt ni
multi-hop a chng, mt phng php hiu qu m rng kch thc cell s c
nghin cu nh l mt cch gii quyt vn cc im cht gy ra bi hiu ng
bng. Truyn dn d liu qua trm chuyn tip c thc hin ngay c khi b gii hn
v cng sut pht ca thit b u cui v suy hao truyn sng ln.
1.2.5.6 Thng tin a phng tin
Cu hnh h thng 4G cho php truyn dn vi tc cao, hot ng lin kt vi
cc mng IP trong khi vn phi m bo c QoS ca truyn dn gi.
Hnh 1.5 Lin l c thng qua cc k t n i multi-hop
1.2.5 Cng ngh cho 4G
Tip theo mng thng tin di ng (TTD) th h th 3 (3G - 3
rd
Generation), Lin
minh Vin thng quc t (ITU) ang hng ti mt chun cho mng di ng t bo mi

16
N TT NGHIP
th h th 4 (4G - 4
th
Generation). 4G c nhng tnh nng vt tri nh: Cho php thoi
da trn nn IP, truyn s liu v a phng tin vi tc cao hn rt nhiu so vi cc
mng di ng hin nay Theo tnh ton, tc truyn d liu c th ln ti 100 Mb/s,
thm ch ln ti 1 Gb/s trong cc iu kin tnh.
Hnh 1.6 S tm lc qu trnh pht trin ca mng thng tin di ng t bo
3 cng ngh di y c xem l cc cng ngh tin 4G, l cc cng ngh lm
s c xy dng nn chun 4G trong tng lai.
LTE (Long-Term Evolution)
T chc chun ha cng ngh mng TTD t bo th h th ba 3G UMTS 3GPP
(3
rd
Generation Partnership Project) bao gm cc t chc chun ha ca cc nc chu
, chu u v Bc M bt u chun ha th h tip theo ca mng di ng 3G l
LTE.
LTE c xy dng trn nn cng ngh GSM (Global System for Mobile
Communications), v th n d dng thay th v trin khai cho nhiu nh cung cp dch
v. Nhng khc vi GSM, LTE s dng phng thc ghp knh phn chia theo tn s
trc giao (OFDM) - truyn d liu tc cao bng cch phn chia thnh cc sng mang

17
N TT NGHIP
con trc giao. LTE s dng ph tn mt cch thch hp v mm do, n c th hot
ng bng tn c rng t 1,25 MHz cho ti 20 MHz. Tc truyn d liu ln nht
(v l thuyt) ca LTE c th t ti 250 Mb/s khi rng bng tn l 20 MHz. LTE
khc vi cc cng ngh tin 4G khc nh WiMAX II ch, n ch s dng OFDM
hng ln, cn hng xung n s dng a truy nhp phn chia theo tn s n sng
mang nng cao hiu qu trong vic iu khin cng sut v nng cao thi gian s
dng pin cho thit b u cui ca khch hng.
UMB (Ultra Mobile Broadband)
T chc chun ha cng ngh mng TTD th h th ba CDMA2000 3GPP2 (3
rd
Generation Partnership Project 2) c thnh lp v pht trin bi cc t chc vin
thng ca Nht Bn, Trung Quc, Bc M v Hn Quc cng vi cc hng nh Alcatel-
Lucent, Apple, Motorola, NEC v Verizon Wireless. Thnh vin ca 3GPP2, Qualcomm
l hng i u trong n lc pht trin UMB, mc d hng ny cng ch tm c vo vic
pht trin LTE.
UMB da trn CDMA (Code Division Multiple Access) c th hot ng bng
tn c rng t 1,25 MHz n 20 MHz v lm vic nhiu di tn s. UMB c
xut vi tc truyn d liu ln ti 288 Mb/s cho lung xung v 75 Mb/s cho lung
ln vi rng bng tn s dng l 20 MHz. Cng ngh ny s cung cp kt ni thng
qua cc sng mang da trn a truy nhp phn chia theo m CDMA.
IEEE 802.16m (WiMAX II)
IEEE 802.16 l mt chui cc chun do IEEE pht trin, chng h tr c c nh
(IEEE 802.16-2004) v di ng (IEEE 802.16e-2005). IEEE 802.16m (hay cn gi l
WiMAX II) c pht trin t chun IEEE 802.16e, l cng ngh duy nht trong cc
cng ngh tin 4G c xy dng hon ton da trn cng ngh a truy nhp phn chia
theo tn s trc giao OFDMA (k thut a truy cp vo knh truyn OFDM).

18
N TT NGHIP
Cng ngh WiMAX II s h tr tc truyn d liu ln ti 100 Mb/s cho cc ng
dng di ng v c th ln ti 1Gb/s cho cc ngi dng tnh. Khong cch truyn ca
WiMAX II l khong 2 km mi trng thnh th v khong 10 km cho cc khu vc
nng thn.
Hng Intel ang dn u v xut s dng v pht trin WiMAX II cho h thng
4G, mt chin lc m cc Hng Alcatel-Lucent, AT&T, Motorola, Nokia, Samsung,
Sprint Nextel v cc thnh vin khc ca WiMAX Forum cng h tr tch cc.
1.2.6 Kt lun chng
H thng thng tin di ng 4G v ang c nghin cu nhiu ni trn th
gii. Vi mc ch gii thiu nhng nt c bn nht v h thng thng tin di ng trong
tng lai, h thng 4G. H thng 4G l h thng khng dy c tc truyn dn cao ph
hp vi nhng nhu cu ngy cng cao ca con ngi. Chng 1gii thiu v nhng th
h thng tin di ng p dng v qu trnh i ln ca h thng thng tin di ng Vit
Nam v chng 1 cng trnh by cc cng ngh ca 4G trong tng lai nh l: LTE,
UMB v IEEE 802.16m. V cng ch ra c nhng u im ca 4G vt tri hn
nhng cng ngh truy nhp v tuyn hin nay.

19
N TT NGHIP
Chng 2 M HA KNH TRONG THNG TIN DI NG
2.1 Qu trnh m ha v nguyn l
2.1.1 Qu trnh m ha
Mt lung thng tin i xuyn qua mt mng truy nhp v tuyn s nh l UTRAN
phi tri qua nhiu qu trnh m ha, c m t trong hnh 2.1. Thng tin a vo h
thng ny phi dng s (d liu) hoc cng c th l thng tin tng t (thoi). Chc
nng m ngun l chuyn i lu lng ngi s dng sang dng s v m rng hn
na l nn d liu. B m ha ngun ph thuc vo loi thng tin cn m ha. Tc
c m ha bng cch s dng mt b m ha tc (b m a tc thch nghi
AMR, trong UTRAN), truyn hnh th s dng b m ha hnh. B m ha ngun c
gng m ha thng tin thnh mt s lng bit thp nht c th m b gii m ngun
pha thu c th xy dng li thng tin ngun nu khng c li no c to ra trong sut
qu trnh truyn ca n. Cc k thut nn khc nhau c th c s dng t c mc
ch m ha ngun. M ha ngun c th b i hu ht cc thng tin d tha ca ngi
s dng. Mt dng khc ca phn d c thm vo sau lung d liu d liu c th
c ti to li my thu mc d iu ny s lm tn tht bng thng ca knh v
tuyn.
Bng cch chn cc bit kim tra c tnh ton trc vo pha sau ca lung d
liu ca ngi s dng, m ha knh s tr nn ng tin cy hn trong qu trnh pht cc
bit thng tin qua giao din v tuyn. Knh truyn c th gy ra li cho cc bit pht, cc
li ny trc ht phi c pht hin v sau c sa li nu c th. Nhim v ny
kh c th thc hin c nu khng thm vo mt s thng tin ph (cc bit kim tra)
vo lung d liu. S lng bit d liu lun c tng ln trong m ha knh. S lng
cc bit ny c tng ln bao nhiu l ty thuc vo tng s m ha. B iu ch s

20
N TT NGHIP
nhn chui bit t b m ha knh v chuyn i lung c m ha knh thnh dng
sng thch hp vi knh truyn. Trong UTRAN, phng php iu ch l QPSK (hoc
16 QAM) hng xung v QPSK knh i (HPSK)
Hnh 2.1 Qu trnh m ha trong h thng truyn thng s
2.1.2 Nguyn l m ha
Vo na cui thp nin 40 ca th k trc, Claude Shannon pht trin mt b
nguyn l m ngy nay chng ta vn thng bit n vi tn gi nh lut Shannon.
Vn m Shannon nghin cu l s lng thng tin ti a c th truyn qua knh
truyn c nhiu tc ng. Trc , n vn c mong i l s cao hn tc d liu
v cng cao th iu tt yu l phi chp nhn li truyn. Shannon chng t rng
khng nht thit phi nh vy, trong mt chng mc no , ta c th t c t l li
gn bng 0, c th t ti dung lng knh ti a hoc bt k tc no di dung
lng knh.Dung lng knh ti a c th c xc nh t ng thc sau:

21
N TT NGHIP
C = W log2 (1+S/N)
Trong , W l bng thng ca knh truyn, S l cng sut ca tn hiu v N l
cng sut nhiu.
nh lut ny thit lp tc truyn d liu tuyt i c th t ti. Ta c th d
dng nhn ra rng nu tng bng thng hoc cng sut ca tn hiu ln th c th tng
dung lng knh ti a ln cao hn. Cn rng khi tng mc nhiu ln th ta cng
phi tng mc tn hiu ln vn m bo c tc truyn d liu nh trc lc
tng mc nhiu. T s tn hiu trn nhiu S/N thng c s dng nh t s gia mc
nng lng trn bit (Eb) v mc nng lng trn Hertz (N
0
) ca nhiu, t s E
b
/N
0
.
Nguyn l ny rt quan trng v cn thit phi ghi nh, c bit trong mt h thng
WCDMA nh UTRAN, ni m qu trnh truyn ca nhng ngi s dng gy nhiu ln
nhau.
2.2 Vai tr ca m ha
Mc ch ca l thuyt M ha trn knh truyn (channel encoding theory) l tm
nhng m c th truyn thng nhanh chng, cha ng nhiu m k (code word) hp l
v c th sa li (error correction) hoc t nht pht hin cc li xy ra (error detection).
Cc mc ch trn khng ph thuc vo nhau, v mi loi m c cng dng ti u cho
mt ng dng ring bit. Nhng c tnh m mi loi m ny cn cn tu thuc nhiu
vo xc sut li xy ra trong qu trnh truyn thng.
Mi m thng ch thch hp cho mt ng dng nht nh. Vin thng trong v tr
(deep space) b gii hn bi nhiu nhit (thermal noise) trong thit b thu. Hin trng ny
khng xy ra mt cch t pht bt thng, song xy ra theo mt chu trnh tip din.
Tng t nh vy, modem vi di tn hp b hn ch v nhiu m tn ti trong mng
li in thoi. Nhng nhiu m ny c th c biu hin r hn bng mt m hnh m
tp tip din. in thoi di ng "Cell phones" hay c vn do s suy sng nhanh

22
N TT NGHIP
chng xy ra. Tn s cao c dng c th gy ra s suy sng tn hiu mt cch nhanh
chng (rapid fading), ngay c khi my nhn ch di ch vi phn Anh (inches) 1. Mt ln
na, ngi ta hin c mt loi thuc hng M ha trn knh truyn c thit k
i u vi tnh trng suy sng.
2.3 Cc phng php m ha knh trong h thng 3G
2.3.1 M khi
M khi thao tc d liu trn mt khi ti cng mt thi im. B m ha s thm
mt s bit kim tra vo khi bit d liu v b gii m s s dng chng xc nh rng
c li no xy ra trong qu trnh truyn hay khng. Do , s bit ng ra ca b m
ha lun lun ln hn ng vo. T s gia khi bit thng tin k (ng vo) v khi bit
c m ha knh n (ng ra) c gi l t l m ha:
Rc = k/n
B m tng ng c xem nh l b m (n,k). Do , phn bit kim tra c
cng thm vo b m (n,k) s l (n k)/n. Cng nhiu bit kim tra c thm vo th
kh nng xc nh li ca b gii m knh s cng tt hn. Tuy nhin, cc bit kim tra
cng s lm tn bng thng ca knh truyn nn cn phi tm ra mt s cn bng tt
nht.Ty thuc vo cch m cc bit kim tra c thm vo t m n m b m nhn
c c th c gi l b m h thng hoc khng h thng. Trong b m h thng,
cc bit kim tra s c trn ln cng vi cc bit thng tin.
C 2
k
khi thng tin c sp xp vo 2
n
t m. Nh chng ta thy, hu ht 2
n
t
m s khng c s dng pha bn tri. B t m c s dng th khng c chn
mt cch ngu nhin m theo cch tt nht b gii m knh c th thc hin c.

23
N TT NGHIP
Hnh 2.2 M ha khi
Khong cch Hamming c o gia 2 t m khc nhau. V d, nu ta c 2 t m
a v b nh sau:
a = 100110001
b = 100101001
Khong cch Hamming d(a,b) = 2 v 2 t m ny khc nhau chnh xc 2 v tr bit
(bit 5 v 6). Khong cch nh nht gia tt c cc t m trong b m c gi l khong
cch ti thiu d
min
. l mt n v o rt quan trng v n ch ra b m ny tt n
mc no trong vic pht hin li. Khong cch ti thiu l i ch ra rng b gii m knh
c th pht hin i 1 bit li. Nu c nhiu hn i -1 bit li th t m thu c s ging vi
t m hp l no ; do , n s c chp nhn nh l mt t m ng.
M khi thng c s dng vi mt phng php yu cu lp li t ng ARQ.
M khi rt hiu qu trong vic tm li v khi tm thy li, mt yu cu pht li khi b
li s c pht ra t mt thc th ngang hng. S phi hp ny i hi d liu hng
khi (block oriented), nhng rng buc v mt thi gian i vi d liu khng c

24
N TT NGHIP
cht ch nn d liu ca ngi s dng phi chu c s tr hon. Mi qu trnh truyn
li s lm tng thm tr truyn ca ton b h thng.
Hnh 2.3 B m c tnh h thng v khng h thng
Phng php kim tra d tha vng CRC l mt phng php ph bin ca m ha
khi. Cc bit CRC cng c s dng trong WCDMA. Vic thm vo cc bit CRC
c thc hin trc khi m ha knh v chng s c kim tra li sau khi gii m
knh. Kch thc ca trng CRC c thm vo cho mt khi truyn c th l 0, 8, 12,
16 hoc 24 bit trong WCDMA. Cc a thc sinh tng ng c cho trong bng 2.1. a
thc sinh c th c gii thch vi mt v d t bng ny. a thc sinh CRC: D
8
+ D
7
+
D
4
+ D
2
+D + 1 ng ngha vi chui bit 110010111. Khi thng tin c chia modulo
2 cho a thc sinh v phn s d s c dng lm trng kim tra (checksum).
Bng 2.1 Cc a thc sinh CRC

25
N TT NGHIP
S lng bit CRC a thc
24
16
12
08
D
24
+ D
23
+ D
6
+ D
5
+ D + 1
D
16
+ D
12
+ D
5
+ 1
D
12
+ D
11
+ D
3
+ D
2
+ D + 1
D
8
+ D
7
+ D
4
+ D
2
+ D + 1
Ngoi ra cn c mt s loi m khi c th c s dng cho mc ch sa li
mc d chng khng c s dng trong WCDMA.
2.3.2 M xon
K thut m ha xon l mt cch khc bo v cc bit thng tin khi cc li c
th xy ra. Trong khi m khi c s dng pht hin li v c ch ARQ c th
sa chng th m xon kt hp c 2 chc nng ny. M xon thng c s dng khi
nhng s rng buc v mt thi gian l cht ch v khng cn dng n c ch ARQ.
D liu c m ha phi cha thng tin kim tra to cho n mt kh nng c
th sa c t nht l mt s li c pht hin trong b gii m knh m khng cn
phi yu cu lp li.
C ch ny c bit n nh l c ch sa li hng ti FEC. My thu khng
yu cu pht li khi pht hin li m n s c gng t sa li .
M xon khc vi m khi ch n hot ng lin tc trn cc lung d liu. N
c mt b nh, iu c ngha l cc bit ng ra khng ch ph thuc vo cc bit vo
hin ti m cn ph thuc vo nhiu bit vo trc na. Mt m xon do c th
c miu t bng cch s dng dng (n, k, m), trong n l s bit ng ra trn mt t
d liu, k l s bit ng vo v m l chiu di b nh ca b m ha. T l m ha ca m
xon cng ging vi m khi:
Rc = k/n

26
N TT NGHIP
Mt b m xon (3, 1, 9) c miu t hnh 2.4. N l mt s kt hp gia thanh
ghi dch D v cc b chc nng XOR. phn cui ca chui d liu va c m ha,
b m ha s thm vo m 1 bit 0 vo chui ng ra. iu ny c thc hin tun hon
m bo b m ha tr li trng thi ban u. Mi ln mt b m ha xon b trn
ngp bi cc li knh th tht kh khn c th phc hi li c t s hn n ca
n. Vic t li trng thi theo chu k c th gii quyt c vn . Cu trc ca b
m ha th n gin hn v hot ng ca n cng khng phc tp lm. Tuy nhin, b
gii m th khc hon ton.
Hnh 2.4 B m ha xon t l 1/3
B gii m ti u l b nh gi chui ng nht MLSE da trn tng mt
chui bit c gii hn, my thu s to ra tt c cc chui m b m ha c th gi. Tip
my thu s so snh chui bit nhn c thc s vi mi chui m n to ra v tnh
khong cch Hamming ca mi cp chui. Khong cch Hamming nh nht s nhn
din c chui c pht ging nht.
Phng php MLSE cung cp b gii m xon hiu qu nht nhng vn l mi
ln chiu di ca chui bit c pht tng th s phc tp ca thut ton MLSE s tr

27
N TT NGHIP
nn kh kim sot. Mt gii php cho vn ny l s dng thut ton Viterbi c th
c tnh sao cho thut ton MLSE hp l vn gi c hiu qu.
Cc b gii m xon c th l b gii m quyt nh cng hoc mm. S phn bit
ny da vo cch m b gii m nhn bit thng tin t b gii iu ch. Trong phng
php quyt nh cng, ng ra ca b gii iu ch l bit 0 hoc 1. Cn trong phng
php quyt nh mm, b gii iu ch gi n khng ch bit nhn c (0 hoc 1) m
cn c mt s c lng v kh nng tin cy ca quyt nh . Vic c lng c
th da trn mt s c s nh l mc tn hiu thu c hin ti. B gii m sau c th
s dng d liu c lng ny nh l mt thng s trong thut ton gii m ti u ca
n.
B gii m xon lm vic tt c th trnh khi cc li ngu nhin nhng nhc
im ca chng l d gy ra cc cm li, c trng trong cc h thng thng tin di ng.
Cc thit b ca ngi s dng (UE) di chuyn nhanh trong cc h thng CDMA c th
gy ra cc li khi nu kh nng iu khin cng sut khng nhanh kim ch
nhiu. i ph vi vn ny, ngi ta chia khi bn tin cn gi thnh cc cm ngn
ri hon v cc cm ny vi cc cm ca khi bn tin khc, nh vy khi xy ra cm li
di, mi bn tin ch mt i mt cm nh, phn cn li ca bn tin vn cho php b gii
m khi phc li ng sau khi sp xp li cc cm ca bn tin theo th t pha
pht. Qu trnh ny c gi l ghp xen tn hiu (interleaving), mc ch l tri cc bit
li ra trn mt khong thi gian di v do lm cho b gii m xon hiu qu hn.
2.3.3 M turbo
M Turbo l mt pht minh tng i mi, n c cp n ln u tin vo
nm 1993. N t c hiu sut rt cao v n c th thc hin gn n gii hn l
thuyt ca nh lut Shannon. Hiu sut ca n t ti u vi cc dch v tc d liu
cao v khng hiu qu my i vi cc dch v tc thp.

28
N TT NGHIP
Trong m ha Turbo, ng ra ca qu trnh gii m s c s dng iu chnh
li d liu ng vo.M turbo u tin s dng 18 vng lp.
B m ha Turbo c s dng trong UTRAN v c trnh by trong hnh 2.5.
B m ha ny l mt b m xon c ni song song (PCCC). N bao gm 2 b m
xon song song nhau v c cch ly bi b ghp xen. Cc b m ha l quy v c
tnh h thng. iu ny ch ng i vi b m Turbo. Cc b m ha cng c th c
ni tun t vi nhau (b m xon c ni tun t SCCC), trong trng hp ny, b
ghp xen c t gia cc b m ha. Cc b m ha cng c th l cc b m khi
thay v b m ha xon, trong trng hp , b m ha Turbo s l mt b m khi
c ni song song PCBC hoc mt b m khi c ni tun t SCBC.
Hnh 2.5 B m ha Turbo
Nhim v ca b ghp xen l ngu nhin ha d liu trc khi n n b m
ha th 2. B ghp xen gm c mt ma trn vung. N cho php hon v c 2 dng

29
N TT NGHIP
intra-row v inter-row cho cc bit ng vo v chui bit ng ra c xn bt bng cch
xa cc bit ny m khng cn tch chui bit ng vo.
B gii m Turbo c m t hnh 2.6. N gm c 2 b gii m SISO c ni
vi nhau bi b ghp xen v b gii ghp xen. Tn hiu t ng ra ca b gii m th 2
c lm tr v hi tip tr li ng vo ca b gii m th nht. Mi ln lp li s ci
thin chnh xc ca d liu gii m. D liu c x l trong vng lp da trn c s
block-by-block. Kch thc ca khi c th thay i t 40 n 5114 bit, bao gm c 2
gi tr ny. Vi s lng d liu nh hn kch thc ti thiu th cn phi chn vo cc
bit gi c th t c kch thc ti thiu.
Hnh 2.6 B gii m Turbo
L
u
= cc gi tr u tin i vi tt c cc bit thng tin u
12
e
L
= thng tin t b gii m 1 vo b gii m 2
21
e
L
= thng tin t b gii m 2 vo b gii m 1
( ) p
c
L r
= thng tin kim tra (parity)

30
N TT NGHIP
( ) s
c
L r
= thng tin h thng (systematic)
2.4 M hnh knh fading v dung lng h thng MIMO trong knh truyn
2.4.1 M hnh knh fading
Xut pht t l do c rt nhiu tham s lin quan trong qu trnh truyn dn trong
mi trng v tuyn di ng, nn s thun tin hn nhiu nu p dng k thut thng k
m t s thay i ca tn hiu.
Trong mt h thng bng hp, tn hiu pht lun chim bng tn nh hn bng tn
kt hp ca knh, bng tn ny c nh ngha l di tn s m qu trnh fading knh l
tng ng. Ngha l mi thnh phn ph ca tn hiu pht c cng s suy gim
fading. Loi fading ny c gi l fading khng chn lc hay fading phng. Mt khc
nu di thng tn hiu pht ln hn di thng kt hp knh, th cc thnh phn ph ca
tn hiu pht vi phn ph ln hn di thng kt hp b fading c lp. Ph tn hiu thu
s b mo v s bin i gia cc thnh phn ph ca tn hiu pht l khng ging nhau.
Hin tng ny c gi l fading chn lc theo tn s. Trong cc h thng bng rng,
tn hiu pht lun chu nh hng ca fading chn lc theo tn s.
Chng ny cp ti m hnh fading Rician v Rayleigh m t s thay i ca
tn hiu trong mi trng a ng bng hp. M hnh fading chn lc theo tn s cho
h thng bng rng s c suy ra bng cch coi bng tn rng l mt tp trc giao cc
bng tn con.
2.4.1.1 Fading Rayleigh
Xt qu trnh truyn dn 1 tn hiu n vi bin khng i. Trong khu vc knh
v tuyn di ng in hnh ta gi s rng sng trc tip b chn v my thu di ng ch
thu c sng phn x. Khi s lng sng phn x ln, theo nh l gii hn trung tm,
2 thnh phn vung gc ca tn hiu thu l qu trnh ngu nhin Gaussian khng tng
quan vi tr trung bnh 0 v phng sai
2
s
. Kt qu l ng bao ca tn hiu thu mi


31
N TT NGHIP
thi im c phn b xc sut Rayleigh v pha ca n phn b ng dng trong khong
p v p . Hm mt phn b ca phn b Rayleigh cho bi cng thc:
( )
2 2
/ 2
2
0
0 0
s
s
a
e a
p a
a

'
<
(2.1)
Gi tr trung bnh l m
a
v phng sai
2
s
ca bin ngu nhin phn b Rayleigh

c cho bi cng thc:
2 2 2
1.2533
2
2 0.4292
2
a s s
a s s
m

_

,
(2.2)
Nu hm mt phn b trong (2.3) c chun ho cng sut tn hiu trung
bnh (
2
E a
) l n v, khi phn b Rayleigh chun ho c cho bi cng thc:
( )
2
2 0
0 0
a
ae a
p a
a
'
<
(2.3)
Gi tr trung bnh v phng sai l:
2
0.8862
0.2146
a
a
m
(2.4)
Trong knh fading vi lng dch tn Doppler cc i f
dmax
, tn hiu thu c ph b
tri trong
ax d m
f f t
. Gi s rng 1 anten v hng vi cc sng ti theo phng ngang,
cc sng phn x v cng sut thu ng dng trn cc gc ti, mt ph cng sut ca
bin fading c cho bi cng thc:

32
N TT NGHIP
( )
2 2
ax
1
2
0
dm
P f f f

'
(2.5)
Trong f l tn s v f
dmax
l t l fading cc i. Gi tr f
dmax
T
s
l t l fading cc
i c chun ho bng tc symbol. N c dng nh 1 tiu chun ca b nh
knh. Vi knh fading tng ng h s ny nm trong di 0< f
dmax
T
s
<1 ch ra 1 b
nh knh gii hn. Hm t tng quan ca qu trnh fading c cho bi cng thc:
( ) ( )
0 ax
2
dm
R J f
(2.6)
Trong J
0
(.) l hm Bessel bc 0 loi 1.
2.4.1.2 Fading Rician
Trong mt vi trng hp nh ng truyn v tinh, knh v tuyn di ng vi t
bo, v c bn l tn ti tia trc tip (LOS). Tn hiu thu bao gm 1 tia sng trc tip v
cc tia phn x. Sng trc tip l tn hiu c bin khng thay i. Cc sng phn x l
tn hiu ngu nhin c lp. Tng ca chng c gi l thnh phn phn tn ca tn
hiu thu. Khi s lng cc sng phn x ln, cc thnh phn vung gc ca tn hiu phn
tn c c tnh nh qu trnh ngu nhin Gaussian vi trung bnh 0 v phng sai
2
s
.
ng bao ca cc thnh phn phn tn c phn b xc sut Rayleigh. Tng ca thnh
phn trc tip v thnh phn phn tn cho kt qu l tn hiu vi phn b ng bao
Rician. pdf ca phn b Rician cho bi cng thc:
( )
( )
2 2
2
2
0 2 2
0
0 0
s
a D
s s
a aD
e I a
p a
a
'
,
<
(2.7)
Trong D
2
l cng sut tn hiu trc tip v I
0
(.) l hm Bessel bc 0 loi 1

nu
cc gi tri cn li
33
N TT NGHIP
Gi s tng cng sut tn hiu trung bnh c chun ho bng 1, pdf trong (2.7)
tr thnh:
( )
( )
( )
( )
( )
2
1
0
2 1 2 1 0
0 0
K K a
a K e I a K K a
p a
a
+ +
'
<
Trong K l h s Rician, c nh ngha l t s ca tia trc tip vi cc thnh

phn phn tn. H s Rician c cho bi cng thc:
2
2
2
s
D
K
(2.8)
Gi tr trung bnh v phng sai ca bin ngu nhin phn b Rician c cho bi
cng thc:
( )
0 1
1
2 2 2
1
2 1
K K K
K I KI
a
m e
K
1 _ _
+ +
1
, , ]
+
(2.9)
2 2
1
a a
m
Trong I
1
(.) l hm bessel loi 1 bc 1. Gi tr K nh ch ra knh b fading ln.
Vi K = 0 th khng c tia trc tip v pdf Rician tr thnh pdf Rayleigh. Mt khc gi
tr K ln ch ra knh b fading nh. Vi K tim cn v cc th khng c fading v kt qu
l knh tr thnh knh AWGN.
2.5 Tng quan v h thng thng tin di ng MIMO
2.5.1 Gii thiu
Cc yu cu i vi dung lng trong cc h thng vin thng v tuyn khin cho
dung lng ca cc h thng di ng t bo, Internet v cc dch v truyn thng a
phng tin buc phi tng ln mt cch nhanh chng din rng. Mt khc, ti
nguyn v ph tn s li b gii hn v dung lng ca cc h thng thng tin s khng
th p ng c nu khng c s gia tng v mt hiu sut s dng ph tn. Cc tin

34
N TT NGHIP
b trong m ha, nh l m turbo v m kim tra parity mt thp (low density parity
check codes), to iu kin thun li t c gii hn dung lng Shannon trong
cc h thng vi mt lin kt anten n. Cc ci tin quan trng sp ti v hiu sut s
dng ph tn l tp trung vo vic tng s lng anten c my pht v my thu.
Trong chng ny, ta s cp n cc gii hn v mt dung lng c bn i vi
truyn dn qua knh MIMO (Multiple-input multiple-output). Cc gii hn v mt dung
lng ny s lm ni bt hiu sut s dng ph ca knh MIMO, s tng xp x tuyn
tnh vi s lng anten (trong trng hp l tng). Dung lng s c tn dng bi
tc d liu ti a c th t c vi mt xc sut li thp ty min l tn hiu phi
c m ha bi mt m khng gian-thi gian di ty . Mt knh MIMO c th c
hnh dung vi cc dy anten a phn t. V s quan tm ch yu ca ta nhm vo s lan
truyn trong cc knh ring bit gia cc cp anten pht v thu cho trc c m hnh
ha bi mt qu trnh fading Rayleigh phng c lp. y, ta gii hn vic phn tch
trng hp knh bng hp do chng c th c m t bi cc m hnh tn s phng
(frequency flat). Kt qu c tng qut ha cho cc knh bng rng, n gin bng
cch xem nh mt knh bng rng nh l mt tp hp ca nhiu knh bng hp trc
giao. Cc m hnh Rayleigh l thc t cho cc mi trng c s ng tn xa ln. Trong
cc knh fading Rayleigh c lp, mt tn hiu c pht t mi anten pht ring l s
xut hin khng tng quan ti mi anten thu. Dn n mt kt qu l tn hiu tng
ng vi mi anten pht s c mt du hiu phn bit v mt khng gian ti mt anten
thu.
M hnh knh fading Rayleigh c lp c th c xp x ha trong cc knh
MIMO ni m khong cch gia cc anten phn t ln hn nhiu so vi bc sng ca
sng mang hoc rng ca gc m sng tc ng l tng i ln (ln hn 30
0
). Mt
v d ca knh ny l ng xung trong h thng v tuyn t bo. cc trm gc c
t trn cao, cc tn hiu thu c t anten l tng quan do gc tc ng nh ca sng

35
N TT NGHIP
ti v vic chia anten ra thnh nhiu anten phn t l cn thit thu c cc tn hiu
c lp gia cc phn t anten ln cn hn l nu gc tc ng ca sng ti ln. C rt
nhiu kt qu o th ch ra rng nu 2 anten thu c s dng cungcp s phn tp
ti my thu trm gc, chng phi c trn 10 bc sng cung cp kh nng gii tng
quan. Tng t, cc php o cng ch ra rng c c cng mi trng phn tp nh
vy ti cc thit b cm tay, n phi chia cc anten rathnh khong 3 bc sng.
2.5.2 M hnh h thng MIMO
Chng ta cng kho st mt h thng MIMO im-im n vi cc dy n
T
anten
pht v n
R
anten thu. Ta tp trung vo mt m hnh h thng tuyn tnh bng tn gc
phc (complex baseband linear system) c miu t ri rc v mt thi gian. S
khi h thng c cho trn hnh 2.1. Tn hiu c pht mi chu k symbol c
miu t bi mt ma trn ct x kch thc n
T
1, trong , thnh phn th i l x
i
i din
cho tn hiu c pht t anten i. Xt mt knh Gaussian, theo l thuyt thng tin [9],
hm phn b tt nht ca tn hiu pht cng l Gaussian. Do , cc phn t ca x c
xt n nh cc bin Gaussian phn b ng nht c lp (i.i.d: independent identically
distributed) trung bnh 0. Ma trn hip phng sai ca tn hiu pht c cho bi:
{ }
H
xx
R E xx
(2.10)
Trong , E{.} k hiu cho k vng v ton t A
H
biu din Hermitian ca ma trn
A, c ngha l chuyn v v lin hp phc tng thnh phn (componentwise) ca ma trn
A . Tng cng sut pht c n nh bi P, bt chp s lng anten pht n
T
. N c th
c biu din nh sau:
P = tr(R
xx
) (2.11)
Vi tr(A) k hiu vt ca ma trn A, t c bng tng ca cc phn t trn
ng cho ca ma trn A . Nu knh cha c bit ti my pht, ta gi s rng cc tn

36
N TT NGHIP
hiu c pht t cc phn t anten ring l c cng sut bng nhau v bng P/ n
T
. Ma
trn hip phng sai ca tn hiu pht c cho bi:
T
xx n
T
P
R I
n
(2.12)
Trong ,
T
n
I
l ma trn n v n
T
n
T
. Bng thng tn hiu pht l hp p
ng tn s ca n c th c xem nh l phng. Ni cch khc, ta gi s rng knh l
khng nh (memoryless).
Hnh 2.7 S khi ca mt h thng MIMO
Knh c m t bi mt ma trn phc n
R
n
T
, biu din bi H. Thnh phn th
ij ca ma trn H, c k hiu bi h
ij
, biu din cc h s fading knh t anten pht th
j n anten thu th i. Thng thng, ta gi s rng cng sut nhn c i vi mi
nhnh ca n
R
nhnh thu bng vi tng cng sut pht. V mt vt l, n c ngha l ta b
qua suy gim v khuch i tn hiu trong qu trnh lan truyn, gm c li ante. Do
, ta s thu c gii hn chun cho cc phn t ca H, trn mt knh vi cc h s c
nh, nh sau:
2
1
, 1, 2, ,...,
T
n
ij T R
j
h n i n
(2.13)

37
N TT NGHIP
Khi cc phn t ma trn knh l cc bin ngu nhin, s chun ha s c dng
vo gi tr c mong i ca biu thc trn. Ta gi s rng ma trn knh c bit ti
my thu nhng khng lun lun c bit ti my pht. Ma trn knh c th c nh
gi ti my thu bng cch truyn mt chui trainning. Thng tin trng thi knh CSI
c nh gi c th c truyn n my pht thng qua mt knh hi tip tin cy. Cc
phn t ca ma trn knh H c th l xc nh hoc ngu nhin. Ta s tp trung vo cc
v d thch hp vi truyn thng v tuyn bao gm cc phn b Rayleigh v Rician ca
cc phn t ma trn knh. Trong hu ht cc hon cnh, ta xem xt phn b Rayleigh v
n tiu biu cho lan truyn v tuyn khng theo tm nhn thng NLOS. Nhiu ti my
thu c miu t bi mt ma trn ct n
R
1, k hiu bi n. Cc thnh phn ca n l cc
bin Gaussian trung bnh 0 phc c lp thng k. Ma trn hip phng sai ca nhiu
my thu c cho bi:
R
nn
= E{nn
H
} (2.14)
Nu khng c s tng quan gia cc thnh phn ca n, ma trn hip phng t
c nh sau:
R
nn
=
2
R
n
I
(2.15)
Mi nhnh ca n
R
nhnh thu c cng sut nhiu ng nht l
2
. My thu s da
vo nguyn l maximum-likelihood thc hin thng qua n
R
anten thu. Cc tn hiu thu
c biu din bi mt ma trn ct n
R
1 , k hiu bi r, trong mi thnh phn phc
i din cho mt anten thu. Ta k hiu cng sut trung bnh ti ng ra ca mi anten thu
l P
r
. T s SNR trung bnh ti mi anten thu c nh ngha nh sau:
2
r
P
(2.16)

38
N TT NGHIP
V ta gi thit rng tng cng sut thu trn anten bng vi tng cng sut pht,
t s SNR bng vi t s gia tng cng sut pht v cng sut nhiu trn anten thu v
n c lp vi n
T
. Do , n c th c vit li nh sau:
2
P
(2.17)
Bng cch s dng m hnh tuyn tnh, vect thu c th c m t nh sau:
r = Hx + n (2.18)
Ma trn hip phng sai ca tn hiu thu, c nh ngha bi E{rr
H
}, bng cch
s dng, c cho bi:
R
rr
= HR
xx
H
H
(2.19)
Trong khi tng cng sut tn hiu thu c th c biu din bng tr(R
rr
) .
2.6 Kt lun chng
Chng 2 cp n nhng phng php m ho trong 3G nh: M khi, M
xon, M turbo. Cc phng php m ho ny gip cho h thng 3G nng cao hiu
sut s dng bng tn v dung lng knh trong qu trnh download v upload so vi
cc h thng GSM v GPRS. Cc phng php ny gip ci thin dung lng h thng,
cung cp nhiu hn cc dch v c in hng ti mt h thng thng tin di ng tt
hn trong tng lai p ng nhu cu s dng ca ngi tiu dng.

39
N TT NGHIP
Chng 3 CC PHNG PHP M HA KNH XUT S DNG
TRONG 4G
Nhng ngi s dng v tuyn khng khng dy hm nay mong i nhiu th ln
t cc mng v tuyn khng dy ngy mai. H ch i rng cc mng v tuyn khng
dy th h tip theo nht l 4G s mang li g? Thm ch ngi ta mong mun rng lu
lng thoi c truyn i ti cc thit b cm tay trong cc gi (tri ngc vi vic
phn pht thng qua knh chuyn mch dnh ring). N s a ra mt chui cc nghin
cu tip theo cho cc cng ngh v tuyn khng dy ang xut hin. S nghin cu ny
tp chung chnh vo cc ng dng (cc dch v v cc thch thc) ang hoch nh cho
s pht trin ca mng v tuyn khng dy th h th t 4G.Cng ngh 4G l cung cp
thng tin d liu gi ha, rng bng ln, tc cao. Chuyn mch knh lin quan ti
k thut trong cc knh dnh ring c s dng pht v nhn tn hiu thoi hay
d liu. S thng tin d liu gi ha lin quan ti k thut bo hiu s trong thng tin
(thoi hay d liu) c chuyn thnh m nh phn v c chia ct thnh cc on
ngn (segments).Phng php M ha khng gian thi gian c xut s dng
trong 4G vi nhng c tnh tt nhm p ng mc tiu a phng tin hng n ca
h thng mng trong tng lai.
3.1 Phng php m ha khng gian - thi gian
3.1.1 Gii thiu
i vi mt h thng c mt s lng ln anten pht v thu, mt knh fading
phng c lp nh bit ti my thu, dung lng s tng mt cch tuyn tnh vi s
lng anten ti thiu.
Mt cch thc t v hiu qu n gn dung lng ca cc knh v tuyn MIMO
(Multiple-input multiple-output) l thc hin m ha khng gian-thi gian ST (Space-

40
N TT NGHIP
time). M ha khng gian-thi gian l mt k thut m ha c thit k s dng vi
nhiu anten pht. M ha c thc hin trong c 2 min khng gian v thi gian a
vo s tng quan gia cc tn hiu c pht t cc anten khc nhau ti cc chu k thi
gian khc nhau. S tng quan khng gian-thi gian c s dng khai thc fading
knh MIMO v ti thiu ha li truyn my thu. M ha khng gian-thi gian c th
t c li phn tp pht v li cng sut hn cc h thng khng c m ha
khng gian m vn khng lm hao ph bng thng. C nhiu hng khc nhau trong cu
trc m ha, bao gm m STBC (Space-time block codes), STTC (Space-time trellis
codes), ST turbo TC (Space time turbo trellis codes) v m LST (layered space-time).
Kt qu chnh trong tt c cc s trn l s khai thc cc hiu ng a ng t
c cc hiu qu cao v ph tn v li hot ng.
3.1.2 Cc h thng m ha khng gian thi gian
Ta xt mt h thng truyn thng c m ha khng gian-thi gian bng tn gc
vi n
T
anten pht v n
R
anten thu, nh c trnh by trn hnh 4.1.
Hnh 3.1 Mt m hnh h thng bng tn gc
D liu pht c m ha bi mt b m ha khng gian-thi gian. Ti mi thi
im t, mt khi m symbol thng tin nh phn, c k hiu bi:
c
t
= (c
1
t,
c
t
2
,...,c
t
m
) (3.1)

41
N TT NGHIP
c a vo ng vo ca b m ha khng gian-thi gian. B m ha khng
gian-thi gian s nh x khi m symbol nh phn ng vo ny thnh n
T
symbol iu ch
t mt b tn hiu M = 2
m
im. D liu c m ha s c a vo b chuyn i
t ni tip sang song song (S/P) xut ra mt chui n
T
symbol song song, c sp xp
thnh mt vecto ct n
T
1
1 2
( , , )
t
n T
t t t t
x x x x
(3.2)
Trong , T c ngha l chuyn v ca mt ma trn. n
T
ng ra song song c pht
ng thi bi n
T
anten pht khc nhau, nh vy m symbol x
i
,1 i n
T
, c pht bi
anten i v tt c cc symbol c pht u c cng mt khong thi gian T (giy). Vect
symbol iu ch m ha t cc anten khc nhau, nh c ch ra (3.2), c gi l
symbol khng gian-thi gian (space-time symbol). Hiu sut ph ca h thng l
b
r
m
B
bit/s/Hz (3.3)
Trong , r
b
l tc bit v B l bng thng knh truyn. Hiu sut ph trong (3.3)
bng vi hiu sut ph ca mt h thng khng m ha vi mt anten pht. Nhiu anten
c my pht v my thu to ra mt knh MIMO. i vi thng tin di ng v tuyn,
mi lin kt t mt anten pht n mt anten thu c th c m hnh ha bi fading
phng, nu ta gi s rng knh truyn l khng nh.
Trong mt knh fading nhanh, cc h s fading l hng s trong mi chu k symbol
v thay i t mt symbol ny sang symbol khc. Ti my thu, tn hiu ti mi n
R
anten
thu l mt s chng nhiu ca n
T
tn hiu pht b suy bin bi fading knh. Ti thi im
t, tn hiu thu c ti anten j, j= 1, 2, , n
R
, c k hiu bi r
j
t
,c cho bi
,
1
T
n
j t i i
t j i t t
i
r h x n
(3.4)

42
N TT NGHIP
Vi
i
t
n
l thnh phn nhiu ca anten thu j ti thi im t. N l mt mu c lp
ca bin ngu nhin Gaussian phc trung bnh 0 vi mt ph cng sut N
0
. Ta miu t
cc tn hiu thu c t n
R
anten thu ti thi im t bng mt vect ct n
R
1.
1 2
( , ,..., )
R
n T
t t t t
r r r r
(3.5)
Nhiu ti my thu c th c m t bi mt vect ct n
R
1, c k hiu bi n
T
1 2
( , ,..., )
R
n T
t t t t
n n n n
(3.6)
Trong , mi thnh phn s ch n mt mu nhiu ti mt anten thu. Do ,
vect tn hiu thu c c th c biu din nh sau:
r
t
= H
t
x
t
+ n
t
(3.7)
Ta gi s rng b gii m ti my thu s s dng mt thut ton maximum-
likelihood khi phc chui thng tin pht v rng my thu c thng tin trng thi
knh CSI l tng trn knh MIMO. Mt khc, my pht li khng c thng tin v knh.
Ti my thu, s metric quyt nh c tnh ton da trn bnh phng khong cch
Euclidean gia chui thu gi thit v chui thu thc s nh sau:
2
,
1 1
T T
n n
i t i
t j i t
t j i
r h x

(3.8)
B gii m s chn mt t m vi s metric quyt nh nh nht lm chui gii m.
3.2 Phn tch c tnh ca m khng gian thi gian
Ta phn tch c tnh m ha khng gian thi gian qua hai v d sau:
V d:
V d 1: M khng gian-thi gian chuyn mch thi gian (Time-Switch
Space-Time Code)

43
N TT NGHIP
Chng ta hy xt mt m khng gian-thi gian chuyn mch thi gian (TSSTC)
sau:
0
0
t
t
x
X
x
1
1
]
(3.9)
Trong h thng ny, ch c mt anten hot ng trong mi khe thi gian v symbol
c iu ch x
t
c pht t anten 1 v 2 ti thi im 2t v 2t +1 tng ng. V mi
symbol iu ch c pht 2 khe thi gian, t l m ha l .
Ma trn:
0
0
t
t
x
X
x
1
1
]
(3.10)
l t m khc vi
t t
x x
. Ma trn hiu m gia 2 t m l:
( )
0
,
0
t t
t t
x x
B X X
x x
1
]
(3.11)
V
t t
x x
nn bc ca ma trn ( )
, B X X
l r = 2 . Ch rng cc ma trn
( )
, A X X
v ( )
, B X X
c cng bc v ( )
, A X X
= ( )
, B X X
( )
,
H
B X X
H thng ny t
c li phn tp l 2 nu s lng anten thu l 1. i vi mt anten thu n, cc tn
hiu thu c ti cc thi im 2t v 2t +1, k hiu bi r
t
1
v r
t
2
tng ng, c cho
bi:
1 1 1
2 2 2
t t t t
t t t t
r h x n
r h x n
+
+
(3.12)
Vi
1
t
h
v
2
t
h
l cc h s fading knh gia anten pht 1, 2 v anten thu tng ng,
1
t
n
v
2
t
n
l cc mu nhiu ti cc thi im 2t v 2t +1 tng ng. Gi s rng cc h s
fading c bit hon ton ti my thu. B gii m maximum likelihood s chn mt tn

44
N TT NGHIP
hiu x
t
t tp hp tn hiu iu ch ti thiu ha s metric bnh phng khong cch
Euclidean:
( ) ( )
2 1 1 2 2 2
, ' , '
t t t t t t
d r h x d r h x +
(3.13)
Da vo phng php MRC, my thu xy dng mt tn hiu thng k quyt nh,
c k hiu bi
'
t
x
:
( )
( ) ( )
1 * 1 2 * 2
* * 2 2
1 2 1 1 2 2
( ) ( )
t t t t t
t t t t t t t
x h r h r
h h x h n h n
+
+ + +
%
(3.14)
Quy tc m ha maximum likelihood c th c vit li nh sau:
( )
( )
2
' 1 2 2 '
arg min 1 ,
t t t t t
x h h d x x + + %
(3.15)
M ha khng gian-thi gian chuyn mch thi gian vi mt anten thu n c th t
c cng li phn tp vi 2 anten thu nh l mt h thng phn tp thu MRC 2
nhnh. Tuy nhin, m ha khng gian-thi gian chuyn mch thi gian ch l bn tc v
c c tnh km hn 3 dB so vi h thng phn tp thu MRC.
V d 2: M lp
Ta tip tc xt mt m khng gian-thi gian bng cch pht cc symbol c iu
ch ging nhau t 2 anten. Ma trn t m khng gian-thi gian c cho bi:
t
t
x
X
x
1
1
]
(3.16)
T l m ha l 1. i vi bt k 2 t m ring bit no vi x
t

t
x%
, ma trn hiu t
m c cho bi:
( )
t t
t t
x x
B X X
x x
1
]
(3.17)

45
N TT NGHIP
Hin nhin, cp ca ma trn ch l 1. Do , m lp c c tnh ging nh mt h
thng khng phn tp (n
T
= n
R
= 1)
3.3 M trellis khng gian-thi gian (STTC)
3.4.1 Gii thiu
STTC cho php phn tp y v li m cao, STTC l loi m chp c m
rng cho trng hp MIMO. Cu trc m chp c bit ph hp vi truyn thng v tr
v v tinh, do ch s dng b m ha n gin nhng t c hiu qu cao nh vo
phng php gii m phc tp.
Nu nh STBC x l c lp tng khi k t u vo to ra mt chui cc
vector m c lp, th STTC x l tng chui k t u vo to ra tng chui vector
m ph thuc vo trng thi m trc ca b m ha.
B m ha cc vc tor m bng cch dich chuyn cc bt d liu qua thanh ghi dch
qua K tng mi tng c k bt. Mi b n ghp cng nh phn vi u vo l K tng s to
ra vector m n bit cho mi k bit u vo. Ti mt thi im, k bit d liu u vo s
c dch vo tng u tin ca thanh ghi dch, k bit ca tng u s c dch vo k bit
ca tng k. Mi ln dch k bit d liu vo s to ra mt vector m n bit.
Tc m l
K l s tng ca thanh ghi dch c gi l constraint length ca b m. Hnh di
cho ta thy r mi vector m trong m li ph thuc vo kK bit, b gm k bit d liu
vo tn u tin v bit ca tng cui ca b m ha, tng cui
ny gi l trng thi ca b m ha, trong khi ch c k bit d liu u vo trong m
khi nh hng ti vector m.

46
N TT NGHIP
Hnh 3.2 S m li
M li c biu din thng qua li m (code trellis) hoc s trng thi
( state diagram) m t s bin i t trng thi hin ti sang trng thi k tip ty thuc k
bit d liu u vo.
V d: B m li k=1, K=3 v n=2
Hnh 3.3 B m li k=1, K=3 v n=2
Hnh 3.3 m t s m ha vi k=1, K=3 v n=2, hnh 3.9 m t li m v s
trng thi ca b m

47
N TT NGHIP
00 =0
01 =1
10 =2
11 =3
00 =0
01 =1
10 =2
11 =3
Trang thai
hien tai
Trang thai
ketiep
Vector ma
00, 11
11, 00
10, 01
01, 10
0
1
3
2
00
11
01
10
01
11
00 10
Ngovao
TX1
TX2
1 1 0 1 1 1
1 1 1 0 1 0
1 0 0 0 0 1
Li ma S otrang thai
Bit vao 1
Bit vao 0
Hnh 3.4 Li m v s trng thi vi k=1, K=3 v n=2
Tn hiu nhn c ti my thu s c b gii m tng quan ti a khng gian-
thi gian STMLD (space-Time Maximum Likelood Decoder) gii m. B STMLD s
c thc hin thnh gii thut vector Viterbi, ng m no c metric tch ly nh nht
s c chn l chui d liu c gii m. phc to ca b gii m tng theo hm
m vi s trng thi trn gin chm sao v s trng thi m li, mt b STTC c
bc phn tp l D truyn d liu vi tc R bps th phc tp ca b gii m t l vi
h s .
STTC cung cp li m tt hn nhiu STBC li ca STTC tng ln khi tng
s trng thi ca li m. Tuy nhin li phc tp ca STBC thp hn nhiu phc
tp ca STTC, do STBC c m ha v gii m n gin nh vo cc gii thut x l
tuyn tnh, nn STBC c m ha v gii m n gin nh vo cc gii thut x l
tuyn tnh, nn STBC ph hp vi cc ng dng thc t trong h thng MIMO hn
STTC.
V d : vi m k/n=2/3 vi 2 bit vo, 3bit ra theo a thc sinh G(x) nh sau

48
N TT NGHIP
G(x)= 5 4 7
7 4 2
Mch thit k c dng hai nhnh V s ln nht trong mi hng l 7 nn D=2
ngha l mi nhnh c 2 b tr. Cc u ra c u ni da trn cc ct ca ma trn
gia cc hng. Nh hnh v di y
Ta c kt qu trng thi dch chuyn ca mch v u ra
Trng thi tip theo u ra
numInputSymbols: 4
numOutputSymbols: 8
numStates: 16
nextStates: [16x4 double]
outputs: [16x4 double]
C th s dng lnh
t = poly2trellis([3 3],[4 5 7;7 4
2]);
trong mathLab kim tra li
0 8 2 10
0 8 2 10
1 9 3 11
1 9 3 11
0 8 2 10
0 8 2 10
1 9 3 11
1 9 3 11
4 12 6 14
4 12 6 14
0 6 7 1
3 5 4 2
1 7 6 0
2 4 5 3
4 2 3 5
7 1 0 6
5 3 2 4
6 0 1 7
5 3 2 4
6 0 1 7

49
N TT NGHIP
5 13 7 15
5 13 7 15
4 12 6 14
4 12 6 14
5 13 7 15
5 13 7 15
4 2 3 5
7 1 0 6
1 7 6 0
2 4 5 3
0 6 7 1
3 5 4 2
3.3.1 H thng m ha khng gian-thi gian
Ta xt mt h thng c m ha khng gian-thi gian bng tn gc vi n
T
anten
pht v n
R
anten thu, nh c trnh by trn hnh 3.5
Hnh 3.5 S khi ca b m ha STTC
D liu c pht sau khi c m ha qua b m ha khng gian-thi gian. Ti
mi thi im t, mt khi m symbol thng tin nh phn c k hiu bi:
( )
1 2
, ,...,
m
t t t t
c c c c
(3.21)
c a vo b m ha khng gian-thi gian. B m ha khng gian-thi gian s
nh x khi m d liu ng vo nh phn thnh n
T
symbol iu ch t mt tp hp tn hiu
M = 2
m
im. D liu sau khi c m ha s c a n b chuyn i tun t sang
song song (S/P) to ra mt chui n
T
symbol song song, c sp xp thnh mt vect
ct n
T
1

50
N TT NGHIP
( )
1 2
, ,...,
T
T
n
t t t t
s s s s (3.22)
Trong , T c ngha l chuyn v ca mt ma trn. n
T
ng ra song song c pht
ng thi t tt c n
T
anten, nh , symbol
i
t
s
s i n c pht bi antenth i v tt
c cc symbol c pht u c cng khong thi gian T giy. Vect ca cc symbol
c iu ch m ha t cc anten khc nhau, c trnh by trong (3.22), c gi l
symbol khng gian-thi gian. Hiu sut ph ca h thng l:
/ /
b
r
m b s Hs
B

(3.23)
Vi r
b
l tc d liu v B l bng thng ca knh truyn. Hiu sut ph trong
(4.84) bng vi hiu sut ph ca mt h thng khng c m ha vi mt anten pht.
Vic s dng nhiu anten c hng pht v hng thu s to ra mt knh MIMO. Ta
gi s c fading phng gia mi anten pht v cng gi s knh truyn l khng nh.
3.3.2 Tiu chun thit k t m khng gian-thi gian
Ta gi s rng chiu di khung d liu c pht l L symbol cho mi anten. iu
ny dn n mt ma trn t m khng gian-thi gian n
T
L
[ ]
1 1 1
1 2
2 2 2
1 2
1 2
1 2
, ,...,
T T T
L
L
L
n n n
L
s s s
s s s
S s s s
s s s
1
1
1

1
1
1
]
K
K
M M O M
K
(3.24)
Trong , mi hng tng ng vi chui d liu c pht t mi anten v mi ct
l symbol khng gian-thi gian ti thi im t.
Xc sut li tng cp PEP (pairwise error probability) l xc sut m b gii m
maximum-lidelihood la chn bng s nh gi ca n i vi tn hiu thu

51
N TT NGHIP
1 2 1 1
1 1 1 2 2
... ... ...
T T T
n n n
L L
e e e e e e e e
trong khi thc t tn hiu
1 2 1 1
1 1 1 2 2
... ... ...
T T T
n n n
L L
s s s s s s s s
c pht.
iu ny s xy ra nu, tnh tng tt c cc symbol, cc anten v cc chu k thi gian:
2 2
, ,
1 1 1 1 1 1
. .
R T R T
n n n n L L
j t i j t i
t i j t t i j t
t j i t j i
r h s r h e

(3.25)
N c th c vit li nh sau:
( ) ( )
2
*
, ,
1 1 1 1 1 1
2Re (
R T R R
n n n n L L
j t i i t i i
t i j t t i j t t
t j i t j i
h e s h e s

' )

(3.26)
Trong , Re{.} l phn thc ca ca s phc.
Nu ta gi s rng my thu c s hiu bit hon ton v knh truyn th i vi
li knh truyn { h
j,i
} trong trng hp c th cho trc, biu thc v phi ca (3.26)
l mt hng s bng vi d
2
(e,s) v biu thc v tri l mt bin ngu nhin Gaussian
trung bnh 0 vi s thay i 4
2
d
2
(e,s). Do , PEP c quyt nh bi vic hiu bit {
h
j,i
} c cho bi
( )
( )
( ) ( )
,
0
,
, 1,..., , 1,...,
2
exp , / 4
i j T R
s
d s e
P s e h i n j n Q
d s e E N
_

,

(3.27)
Trong , Q(x) l hm b li c cho bi ( )
2
/ 2 t
x
Q x e dt
Lc ny, d
2
(e,s) c th c vit li nh sau:
( ) ( )
*
* ' '
, ',
1 ' 1
T T
n n
i i i i
i j i j t t t t
i i
h h s e s e

(3.28)
Trong , x* l lin hip phc ca x . Do :
( ) ( )
*
2 * ' '
, ',
1 1 1 ' 1
( , )
R T T
n n n L
i i i i
i j i j t t t t
t j i i
d s e h h s e s e

(3.29)
Nu ta k hiu
j
= h
1,j
,h
2,j
,...,h
nT,j
, ta c th vit li:

52
N TT NGHIP
2
1
( , )
R
n
H
j j
j
d s e A
(3.30)
Vi
H
j
k hiu cho chuyn v Hermitian ca

j
v A=A(e,s) l mt ma trn n
T
n
T
c lp vi thi gian v cha ( ) ( )
*
,
1
L
p p q q
p q t t t t
t
A s e s e
. V vy, PEP tr thnh

( ) ,
1 0
, 1,..., , 1,..., exp
4
R
H
n
j j s
i j T R
j
A E
P s e h i n j n
N
_

,
(3.31)
V A l ma trn chuyn v Hermitian, do tn ti mt ma trn V tha mn VV
H
= I
v mt ma trn cho thc D sao cho VAV
H
= I
Hng { }
1 2
, ,...,
T
n
v v v
ca ma trn V l cc vect ring ca ma trn A v to thnh mt
c s trc giao hon ton ca mt khng gian vect n
T
hng. Hn na, cc phn t trn
ng cho ca ma trn D l cc gi tr ring
i
, i =1,2,..., n
T
ca ma trn A l nhng s
thc khng m v A l ma trn chuyn v Hermitian. Theo cch xy dng ma trn A, ma
trn hiu t m B c cho bi:
( )
1 1 1 1 1 1
1 1 2 2
2 2 2 2 2 2
1 1 2 2
1 1 1 1 1 1
,
T T T T T T
L L
L L
n n n n n n
e s e s e s
e s e s e s
B s e
e s e s e s
_

,
K
K
M M O M
K
(3.32)
L mt nghim bnh phng ca ma trn A (c ngha l A = BB
H
).
Tip theo, ta s biu din d
2
(s,e) di dng {
i
} . Gi s (
1,j
,
2,j
,,
nT,j
= ) , ta
c:
2
,
1
T
n
H H H
j j j j j i j
i
A V DV
(3.33)
2
2
,
1 1
( , )
R T
n n
j i j
j i
d s e

(3.34)

53
N TT NGHIP
V h
i,j
l cc mu ca mt bin ngu nhin Gaussian phc vi gi tr trung bnh Eh
i,j
, ta c:
K
j
= (Eh
1,j
,Eh
2,j
,...,Eh
nT,j
)
V ma trn V l duy nht, iu ny ni ln rng
i,j
l cc bin Gaussian ngu nhin phc
c lp vi s thay i 0.5 trn th nguyn v vi gi tr trung bnh l K
j
.v
i
.
3.3.3 M ha/gii m STTC trn knh fading phng gi tnh
Qu trnh m ha i vi STTC tng t nh iu ch m ha trellis ngoi tr
phn u v phn cui mi khung, b m ha phi trong trng thi 0. Ti mi thi im
t, ph thuc vo trng thi ca b m ha v cc bit ng vo, mt nhnh chuyn tip s
c chn. Nu nhn ca nhnh truyn l
1 2
, ,...,
T
n
t t t
s s s
th anten pht i, c s dng
gi chm sao symbol
i
t
s
, i=1,2,...,n
T
v tt c cc qu trnh pht ny l song song nhau.
Hnh 3.6 ng bin gia tiu chun TSC v tiu chun vt
Mt v d v mt b m ha STTC c trnh by trong hnh 3.7 i vi iu ch 4-
PSK. Tp hp h s ca b gii m, c k hiu bi:
( ) ( ) ( )
0,1 0,2 0, 1,1 1,2 1, ,1 ,2 ,
, ,..., , , ,..., ,..., , ,...,
T T i i i T
i i i i i i i i i i
y n n v v v n
g g g g g g g g g g
1
]
(3.35)

54
N TT NGHIP
Hnh 3.7 B m ha STTC vi 4-PSK
Mi
,
i
L k
g
l mt phn t ca b chm sao 4-PSK {0, 1, 2, 3} v v
i
l bc nh ca
thanh ghi dch th i. Ng ra b nhn c cng module 4. B m ha trong hnh 4.16 c
th c miu t di dng a thc sinh. Chui nh phn ng vo n thanh ghi dch
pha trn c th c m t nh sau:
1 1 1 1 2 1 3
0 1 2 3
( ) ... u D u u D u D u D + + + +
(3.36)
Tng t, chui nh phn ng vo n thanh ghi dch pha di c th c vit li
nh sau:
2 2 2 2 2 2 3
0 1 2 3
( ) ... u D u u D u D u D + + + +
(3.37)
Trong ,
k
j
u
,j = 0,1,2,..., k = 1,2... l cc symbol nh phn 0, 1. a thc sinh i
vi b m ha pha trn v anten pht th i , vi i = 1, 2 c th c vit li nh sau:
( )
1 2 2 2 2 2 3
0 1 2 3 i
G D u u D u D u D + + + +K
(3.38)
Trong ,
, 1
, 0,1,...,
k
i j
g j v
l cc h s khng phi nh phn, c th ly cc gi tr t
mt chm sao, v d nh 4-PSK l 1, j, 1, j v v
1
l bc nh ca b m ha pha trn.
Tng t, a thc sinh i vi b m ha pha di v anten pht i, vi i = 1, 2 c th
c vit li nh sau:
( )
2
2
2 2 2 2
0, 1, ,
...
v
i i i v i
G D g g D g D + + +
(3.39)
Trong ,
2
0,i
g
,j = 0,1,...,v
2
cng l cc h s khng phi nh phn, c th ly gi tr
t mt chm sao, v d nh 4-PSK l 1, j, 1, j v v
2
l bc nh ca b m ha pha
di. Chui symbol m ha c pht i t anten i c cho bi:
( ) ( ) ( ) ( )
1 1 2 2
mod 4
i
i i
s D u D G D u G D +
(3.40)
Ta cn c th biu din n nh sau:

55
N TT NGHIP
( ) ( ) ( )
( )
( )
1
1 2
2
mod 4
i i
i
G D
s D u D u D
G D
1
1
1
]
]
(3.41)
Gi s
i
t
r
l tn hiu thu c ti anten j ti thi im t , s metric nhnh (branch
metric) c cho bi:
,
1 1
R T
n n
i i
t i j t
j i
r h q

(3.42)
Thut ton Viterbi c s dng tnh ton ng i vi s metric nhnh thp
nht. Trong mi trng CSI khng l tng, ta s c lng CSI da vo cc symbol
trainig.
3.4 M khi khng gian-thi gian (STBC)
3.4.1 Gii thiu
Trong phn ny chng ta s cp n m khi khng gian-thi gian STBC v
nh gi c tnh ca n trn knh fading MIMO. u tin chng ta s gii thiu v m
Alamouti, l mt s phn tp pht 2 nhnh n gin. c im chnh ca s
ny n c th t ti mt li phn tp kh cao vi mt thut ton m ha maximum-
likelihood n gin. Tip , chng ta cng s xem xt n STBC vi mt s lng ln
anten pht da trn thit k trc giao.
3.4.2 c tnh ca h thng Alamouti
Do tnh trc giao gia cc chui n t 2 anten pht, h thng Alamouti c th t
c s phn tp pht y vi n
T
= 2. Ta hy xem xt 2 chui m ring bit v
X

c to ra bi cc tn hiu ng vo ( )
1 2
, x x
v ( )
1 2
, x x
tng ng, vi ( )
1 2
, x x

( )
1 2
, x x
. Ma trn hiu t m c cho bi:
( )
* *
1 1 2 2
* *
2 2 1 1

,

x x x x
B X X
x x x x
1 +
1

]
(3.43)

56
N TT NGHIP
V cc dng ca ma trn m trc giao vi nhau nn cc dng ca ma trn hiu t
m cng trc giao vi nhau. Ma trn khong cch t m c cho nh sau:
( ) ( ) ( )
2 2
1 1 2 2
2 2
1 1 2 2

, , ,
0
0
H
A X X B X X B X X
x x x x
x x x x
1
+
1
1 +
]
(3.44)
V ( )
1 2
, x x

( )
1 2
, x x
, nn cc ma trn khong cch ca 2 t m phn bit bt k
u c mt dy y ca c 2.
Ni cch khc, h thng Alamouti c th t c mt s phn tp y vi n
T
=
2. nh thc ca ma trn ( )
, A X X
c cho bi:
( ) ( ) ( )
2
2 2
1 1 2 2
det , A X X x x x x + (3.45)
T (3.44) cho h thng Alamouti, ta thy ma trn khong cch t m c 2 gi tr
ring ng nht. Gi tr ring ti thiu bng vi khong cch Euclidean bnh phng ti
thiu trong chm sao tn hiu. iu ny rt c ngha i vi h thng Alamouti,
khong cch ti thiu gia 2 chui m c truyn bt k vn phi ging nhau nh trong
h thng khng m ha.
3.4.3 M khng gian-thi gian Alamouti
S Alamouti l m STBC u tin cung cp phn tp pht y vi 2 anten
pht. Mt s khc cng cn c nhc n l s phn tp tr, n cng c th t
c kh nng phn tp y nhng n li gy nhiu symbol v cn phi c mt b d
(detector) phc tp my thu. Sau y chng ta s tm hiu k thut phn tp pht ca
Alamouti, bao gm cc thut ton m ha, gii m v c tnh ca chng.
H thng Alamouti t c kh nng phn tp y vi thut ton gii m rt
n gin l thut ton gii m maximum-likelihood. c im chnh ca h thng l

57
N TT NGHIP
tnh trc giao gia cc chui c pht bi 2 anten. H thng ny suy rng n mt s
lng anten pht ty bng cch p dng nguyn l ca cc mu trc giao (orthogonal
design). Cc h thng c suy rng c xem nh l cc h thng STBC. Cc m
khi khng gian-thi gian c th t c kh nng phn tp pht y c nh r
bng s anten pht n
T
, trong khi vn chp nhn thut ton gii m maximum-likelihood,
ch da trn vic x l tuyn tnh cc tn hiu nhn c
fading Rayleigh chm

58
N TT NGHIP
fading Rayleigh chm
Hnh 3.9 m t cu trc ca mt b m ha ca m khi khng gian-thi gian.
Thng thng, mt b m khi khng gian-thi gian c nh ngha bi mt ma trn
truyn n
T
p. y, n
T
i din cho s anten pht v p i din cho s chu k thi gian
pht mt khi symbol m ha.
Ta gi s rng chm sao tn hiu gm c 2
m
im. Ti mi hot ng m ha, mi
khi gm m bit thng tin c nh x vo chm sao tn hiu chn k tn hiu iu ch
x
1
, x
2
,..., x
k
, vi mi nhm m bit s chn mt tn hiu trong chm sao. k tn hiu iu ch
s c m ha bi b m ha khi khng gian-thi gian to ra n
T
chui tn hiu song
song c chiu di p tng ng vi ma trn truyn . Cc chui ny c pht thng qua
n
T
anten pht ng thi trong khong thi gian p .

59
N TT NGHIP
Trong m ha khi khng gian-thi gian, s lng symbol m b m ha yu cu
ng vo ca n trong mi hot ng m ha l k. S chu k truyn c yu cu pht
cc symbol c m ha thng qua nhiu anten pht l p. Ni cch khc, c p symbol
khng gian-thi gian c pht t mi anten cho mi khi k symbol vo. T l ca mt
m khi khng gian-thi gian c nh ngha l t s gia s symbol m b m ha ly
ng vo v s symbol m ha c pht t mi anten. N c cho bi:
R = k / p (3.46)
Hiu sut ph ca m khi khng gian-thi gian:
/ /
b s
s
r r mR km
bit s Hz
B r p

(3.47)
Vi r
b
v r
s
l tc bit v tc symbol, B l bng thng.
Hnh 3.10 B m ha STBC
Cc phn t ca ma trn truyn X l t hp tuyn tnh ca k symbol iu ch
x
1
,x
2
,...,x
k
v lin hp ca chng x
1
*
,x
2
*
,...,x
k
*
. t c kh nng phn tp pht y
ca n
T
, ma trn truyn X c xy dng da trn cc mu trc giao.

60
N TT NGHIP
( )
2 2 2
1 2
. ...
T
H
k n
X X c x x x I + + +
(3.48)
Vi c l hng s,
H
l ma trn Hermitian ca X v
T
n
I
l mt ma trn n v
n
T
n
T
. Hng th i ca X tng ng vi cc symbol c pht t anten pht th i lin tip
trong khong thi gian pht p , trong khi ct th j ca X tng ng vi cc symbol c
pht ng thi qua n
T
anten pht ti thi im j. Phn t ca X trong hng th i v ct
th j , x
i,j
, i = 1,2,..., n
T
, j =1,2,..., p, tng ng vi tn hiu c pht t anten i ti thi
im j.
Ta thy rng t l ca m khi khng gian-thi gian vi kh nng phn tp y
th nh hn hoc bng 1, R 1. B m t l ti a R =1 khng yu cu m rng bng
thng trong khi b m vi t l R < 1 yu cu m rng bng thng bng 1/R . i vi m
khi khng gian-thi gian c n
T
anten pht, ma trn truyn c biu din bi X
nT
. B
m ny c gi l m khi khng gian-thi gian kch thc n
T
.
Ch rng cc mu trc giao c p dng xy dng b m khng gian-thi
gian. Cc hng ca ma trn truyn
nT
trc giao ln nhau. iu ny c ngha l trong mi
khi, cc chui tn hiu t bt k 2 anten pht no cng trc giao vi nhau.
V d, nu ta gi s rng x
i
=(x
i,1
,x
i,2
,...,x
i,p
) l chui c pht t anten th i, vi
i=1,2,...,n
T
, ta c:
{ }
*
, ,
1
. . 0, , , 1, 2,...,
p
i j i t j t R
t
x x x x i j i j n
(3.49)
Vi x
i
.x
j
biu din tch trong ca cc chui x
i
v x
j
. Tnh trc giao cho php t n
kh nng phn tp y cho mt s lng anten pht cho trc. Hn na, n cn cho
php my thu gii ghp cc tn hiu c pht t cc anten khc nhau v do cn c
mt qu trnh gii m ng nht ch da trn qu trnh x l tuyn tnh tn hiu thu c.
3.4.3.1 M ha khng gian-thi gian Alamouti

61
N TT NGHIP
Hnh 3.11 S khi ca b m ha ST Alamouti
Ta gi s rng phng php iu ch M-ary c s dng. Trong b m ha ST
Alamouti, u tin, mi nhm m bit thng tin s c iu ch, vi m = log
2
M. Sau ,
b m ha s ly mt khi ca 2 symbol c iu ch x
1
v x
2
mi hot ng m
ha v a chng n anten pht theo mt ma trn m c cho bi:
*
1 2
*
2 1
x x
X
x x
1
1
]
(3.50)
Ng ra b m ha c a vo 2 chu k pht lin tc ca 2 anten pht. Trong
khong chu k pht th nht, 2 tn hiu x
1
v x
2
c pht ng thi t anten 1 v anten
2 tng ng. Trong khong chu k th 2, tn hiu
*
2
x
c pht t anten pht 1 v tn
hiu
*
1
x
c pht t anten pht 2, trong
*
1
x
l lin hp phc ca x
1
. Qu trnh m ha
lm vic rt r rng c 2 min khng gian v thi gian. iu ny c ngha l chui x
1
v x
2
c pht t anten 1 v 2 tng ng l:
1 *
1 2
2 *
2 1
,
,
x x x
x x x
1
]
1
]
(3.51)
c im chnh ca s Alamouti l cc chui pht t 2 anten phi trc giao vi
nhau tch trong ca cc chui x
1
v x
2
bng 0, c ngha l:

62
N TT NGHIP
x
1

.x
2
= x
1
x
2
- x
2
*
x
*
1
(3.52)
Ma trn m c tnh cht sau:
( )
2 2
1 2
2 2
1 2
2 2
1 2
0
.
0
H
x x
x x
x x
1
+
1
1 +
]
+
2
XX
I
(3.53)
Trong , I
2
l ma trn n v (identity) 22.
Gi s rng c mt anten thu c s dng my thu. S khi ca my thu
trong h thng Alamouti c trnh by hnh 3.11. Cc h s knh Fading t anten
pht th nht v th 2 n anten thu ti thi im t c biu hin tng ng bi h
1
(t) v
h
2
(t). Gi s rng cc h s fading l hng s qua 2 chu k truyn symbol lin tip,
chng c th c biu din nh sau:
1
1 1 1 1
( ) ( )
j
h t h t T h h e

+
(3.54)
V
2
2 2 2 2
( ) ( )
j
h t h t T h h e

+
(3.55)
Trong ,
i
h
v
i
, vi i = 0, 1, l li bin v dch pha t anten pht i n
anten thu, T l thi gian 1 symbol. Ti anten thu, cc tn hiu thu c qua 2 chu k
symbol lin tip, c biu din bi r
1
v r
2
cho cc thi im t v t + T . Chng c
biu din nh sau:
1 1 1 2 2 1
r h x h x n + +
(3.56)

* *
2 1 2 2 1 2
r h x h x n + +
(3.57)

63
N TT NGHIP
Trong , n
1
v n
2
l cc bin phc c lp vi trung bnh khng v mt ph
cng sut N
0
/2 trn th nguyn, tng ng vi cc mu nhiu Gaussian trng cng thm
ti thi im t v t + T.
Hnh 3.12 My thu ca h thng Alamouti
3.4.3.2 Gii m Maximum Likelihood v Combining

64
N TT NGHIP
Nu cc h s knh fading h
1
v h
2
c th c b li hon ton ti my thu th b
gii m s s dng chng nh thng tin v trng thi knh CSI. Gi s rng tt c tn
hiu trong chm sao iu ch u c kh nng xy ra nh nhau, mt b gii m
maximum likelihood s chn mt cp tn hiu
1 2
( , ) x x
t chm sao iu ch tn hiu
gim n mc ti thiu khong cch Mtric
( )
2 2 * *
1 1 1 2 2 2 1 2 2 1
2
2
* *
1 1 1 2 2 2 1 2 2 1
, ( , )

d r h x h x d r h x h x
r h x h x r h x h x
+ + +
+ +
(3.58)
qua tt c cc gi tr c th c ca
1
x
v
2
x
. Thay (3.56) v (3.57) vo (3.58), gii m
maximum likelihood c th c miu t nh sau:
( )
( ) ( )
( ) ( )
1 2
2 2 2 2
2 2
1 2 1 2 1 2 1 1 2 2
( , )
, arg min 1 , ,
x x C
x x h h x x d x x d x x
+ + + + % %
(3.59)
Trong C l tp hp ca tt c cc cp symbol c iu ch ( )
1 2
, , x x

1
x%
v
2
x%
l
2 i lng thng k quyt nh c xy dng bng cch kt hp cc tn hiu nhn
c vi thng tin trng thi knh. i lng thng k quyt nh c cho bi:
* *
1 1 1 2 2
* *
2 2 1 1 2
x h r h r
x h r h r
+
+
%
%
(3.60)
Thay r
1
v r
2
t (3.56) v (3.57) tng ng vo (3.60), i lng thng k quyt
nh c th vit li nh sau:
( )
( )
2 2
* *
1 1 2 1 1 1 2 2
2 2
* *
2 1 2 2 1 2 2 1
x h h x h n h n
x h h x h n h n
+ + +
+ +
%
(3.61)
i vi s thc hin ca mt knh cho trc h
1
v h
2
, cc i lng thng k
quyt nh
i
x%
, i = 1, 2, ch c mt chc nng ca x
i
, i = 1, 2. Nh vy, quy tc gii m

65
N TT NGHIP
maximum likelihood (4.36) c th c tch ra thnh 2 quy tc gii m c lp nhau cho
x
1
v x
2
, c cho bi:
( )
( )
( )
( )
1
2
2 2 2
2
1 1 2 1 1 1
2 2 2
2
2 1 2 2 2 2
arg min 1 ,
arg min 1 ,
x S
x S
x h h x d x x
x h h x d x x
+ +
+ +
%
%
(3.62)
i vi chm sao tn hiu M PSK, ( )
2 2 2
1 2 1
1 h h x +
,i=1,2, l hng s i vi tt
c cc im tn hiu, gy ra cc h s fading knh. Do , cc quy tc quyt nh trong
(3.62) c th n gin ha hn na thnh:
3.5 H thng Alamouti vi nhiu
anten thu
H thng Alamouti c th c ng dng cho mt h thng vi 2 anten pht v
n
R
anten thu. Qu trnh m ha v pht ca cu hnh ny cng ging vi trng hp mt
anten thu n. Cc tn hiu thu c r
1
j
v r
2
j
t anten thu th j ti thi im t v t + T
tng ng:
r
1
j
=h
j,1
x
1
+ h
j,2
x
2
+ n
1
j
r
2
j
=h
j,1
x
2
+ h
j,2
x
1
+ n
2
j
(3.63)
Trong h
i,j
, i = 1, 2; j = 1, 2, ,n
R
l h s fading cho ng t anten pht i
n anten thu j v n
1
i
, n
2
j
l cc tn hiu nhiu ca anten thu j ti thi im t v t +T
tng ng. My thu xy dng 2 i lng thng k quyt nh da trn s kt hp tuyn
tnh ca cc tn hiu nhn c. Cc i lng thng k quyt nh
1
x%
v
2
x%
c cho
bi:

( )
( )
1
2
2
1 1 1
2
1 2 2
arg min ,
arg min ,
x S
x S
x d x x
x d x x
%
%
66
N TT NGHIP
( )
( )
( )
( )
*
*
1 ,1 1 ,2 2
1
2
2
*
*
, 1 ,1 1 ,2 2
1 1 1
*
*
2 ,2 1 ,1 2
1
2
2
*
*
, 2 ,2 1 ,1 2
1 1 1
R
R R
R
R R
n
j j
j j
j
n n
j j
j i j j
i j j
n
j j
j j
j
n n
j j
j i j j
i j j
x h r h r
h x h n h n
x h r h r
h x h n h n

+
+ +

+

%
%
(3.64)
Cc quy tc gii m maximum likelihood cho 2 tn hiu c lp x
1
v x
2
c cho
bi :
( )
( )
1
2 2
2
2
1 ,1 ,2 1 1 1
1
arg min 1 ,
R
n
j j
x S
j
x h h x d x x
1 _
+ +
1
1
, ]
%
(3.65)
( )
( )
2
2 2
2
2
2 ,1 ,2 2 2 2
1
arg min 1 ,
R
n
j j
x S
j
x h h x d x x
1 _
+ +
1
1
, ]
%
(3.66)
i vi iu ch M PSK, tt c tn hiu trong chm sao u c nng lng bng
nhau. Cc quy tc gii m maximum likelihood tng ng vi trng hp ch c mt
anten thu n.
3.5.1 Trng hp 1 anten pht 2 anten thu
Ta gi s rng fading t mi anten pht n mi anten thu th c lp vi nhau v
do my thu s nhn bit mt cch tt nht cc h s knh. Hnh 3.13 biu din t l
li bit BER ca h thng Alamouti vi iu ch BPSK nht qun (coherent) so vi t s
tn hiu trn nhiu SNR trn anten thu. c tnh BER ca h thng phn tp thu 2 v 4
nhnh vi anten pht n v s kt hp t s ti a MRC cng c biu din trong
hnh d so snh. Hn na, ta gi s rng cng sut pht tng t 2 anten ca h thng
Alamouti bng vi cng sut pht t anten pht n ca h thng phn tp my thu
MRC v thng thng chng l mt. Cc kt qu m phng ch ra rng h thng

67
N TT NGHIP
Alamouti vi 2 anten pht v mt anten thu n t c kh nng phn tp nh h
thng phn tp thu 2 nhnh MRC do dc ca c 2 l nh nhau.
Tuy nhin, c tnh ca h thng Alamouti th km hn 3 dB. S thua km l do
nng lng pht x t mi anten pht trong h thng Alamouti ch bng phn na so vi
anten n trong h thng phn tp thu MRC do 2 h thng ny c cng cng sut pht
tng. Nu mi anten pht trong h thng Alamouti pht x cng mc nng lng vi
anten pht n trong h thng phn tp thu MRC th h thng Alamouti s tng ng
vi h thng phn tp thu MRC.
Tng t, t hnh v chng ta c th thy rng h thng Alamouti vi 2 anten thu
s t c kh nng phn tp nh mt h thng phn tp thu MRC 4 nhnh nhng c
tnh li km hn 3 dB. Thng thng, h thng Alamouti vi 2 anten pht v n
R
anten
thu c cng li phn tp vi h thng phn tp thu MRC c 1 anten pht v 2n
R
anten
thu
Hnh 3.13 c tnh BER ca h thng BPSK Alamouti vi 1 v 2 anten thu trn knh
fading Rayleigh chm

68
N TT NGHIP
Vi trng hp ny th almouti STBC chng c truyn t 2 anten pht . Do
truyn ti nng lng trong chng trnh Alamouti c s dng hai ln trong MRC.
Do cn bng chng ta cn lm cho nng lng truyn t 2 anten trong trng hp
STBC mnh ln bng vi nng lng truyn t 1 anten trong MRC.Vi quy m ny
chng ta c th thy rng hiu sut BER ca 2Tx, 1Rx Alamouti trng hp STBC c
hiu sut km hn khong 3dB 1Tx, 2Rx so vi trng hp MRC.
T bi vit T l ti a kt hp, t l li bit cho iu ch BPSK trong knh
Rayleigh vi 1 pht, 2 thu nhn c trng hp l:
(3.67)
Trong :
1/ 2
0
1 1 1
1
2 2 /
MRC
b
p
E N
_
+

,
(3.68)
Khi 2 pht v 1 thu nhn c :
(3.69)
T l li bit:
[ ]
2
,
1 2(1 )
e STBC STBC STBC
P p p + (3.70)
c im :Thc t l mt ma trn ng cho m bo nhng iu sau y:
1. Khng c trao i qua li gia, sau khi cn bng.
2. Qu trnh nhiu vn cn trng

69
N TT NGHIP
2 2 2 2
1 1 1 2 1 *
1 2 *
2 2 2 2
2
2 2 1 2
0 0 0
0 0 0
H H
n n h h n
E H n n H H H
n
n n h h
1 1 1
+
1

1 1 1 1
' )
1
]
1 1 1 + ]

] ] ]
(3.71)
fading Rayleigh chm
T vic tho lun v cc knh v m hnh nhiu chng ta tham kho v nhng tn
hu nhn c khi s dng hai anten pht hai anten thu t anten Alamouti STBC.
1 1
11 21 1 1 1
1 1
12 22 2 2 2
h h x y n
h h x y n
1 1 11
+
1 1 11
]] ] ]
(3.72)

70
N TT NGHIP
Gi nh rng knh vn khng i cho cc khe thi gian th hai, tn hiu nhn
c trong cc khe thi gian th hai l :
2 * 2
11 21 1 2 1
2 * 2
12 22 2 1 2
h h y x n
h h y x n
1 1 1 1
+
1 1 1 1
] ] ] ]
(3.73)
Trong :
1
1
1
2
y
y
1
1
]
L tn hiu nhn c khe thi gian th nht ca 1,2 anten tng ng
2
1
2
2
y
y
1
1
]
L tn hiu nhn c khe thi gian th 2 ca 1,2 anten tng ng
ij
h
L h s knh t anten pht th 1 n anten nhn th j
1 2
, x x
L tn hiu truyn
1
1
1
2
n
n
1
1
]
L h s nhiu khe thi gian th nht trn anten nhn 1 v 2
2
1
2
2
n
n
1
1
]
L h s nhiu khe thi gian th hai trn anten nhn 1 v 2
Kt hp khe thi gian th nht v th 2 ta c :

1 1
11 21 1 1
1 1
12 22 1 2 2
* * 2* 2*
21 11 2 1 1
* * 2* 2*
22 12 2 2
h h y n
h h x y n
h h x y n
h h y n
1 1 1
1 1 1
1
1 1 1
+
1
1 1 1
]
1 1 1
1 1
] ] ]
(3.73)
Chng ta xc nh
11 21
12 22
* *
21 11
* *
22 12
h h
h h
H
h h
h h
1
1
1
1
1
]

71
N TT NGHIP
gii quyt vn ta cn tm ra nghch o ca H, ta bit, cho mt MXN
chung ma trn nghch o gi c nh ngha l :
( )
1
H H
H H H H
+
(3.74)
Ta gii bi ton vi ma trn tm c :
( )
2 2 2 2
11 21 12 22
2 2 2 2
11 21 12 22
0
0
H
h h h h
H H
h h h h
1
+ + +
1
1 + + +
]
(3.75)
V y l ma trn ng cho nghch o O ngc ng cho cc yu t:
( )
2 2 2 2
1
11 21 12 22
2 2 2 2
11 21 12 22
1
0
1
0
H
h h h h
H H
h h h h
1
1
+ + +
1
1
1
+ + +
1
]
(3.76)
c tnh ca biu tng truyn:
( )
1
1
1
1
1 2
* 2*
2 1
2*
2
H H
y
x y
H H H
x y
y
1
1
1
1
1
1
]
1
1
]
(3.77)

72
N TT NGHIP
fading Rayleigh chm
3.3 So snh gia STBC V STTC
Trong hnh 3.16 (m ha 4 trng thi), ta nhn thy rng STBC cho ng c tnh
tt hn tt c cc loi m STTC, thm ch n cn khng c li m ha. iu ny c
th c gii thch bng cu trc a chiu ca STBC, v mi t m s ni 2 symbol lin
tc nhau v trung bnh nhiu tc ng ln chng. Nhng c im khc cn phi ch :
Vi cng s trng thi trellis, ng c tnh ca STBC kt hp nm bn ngoi cc
ng c tnh ca cc STTC cc t s SNR quan trng (tc l 4 n 12 dB i vi
trng hp 2 anten thu v 10 n 18 dB i vi trng hp mt anten thu).Vi vic tng
s lng anten v cc trng thi trellis, ng c tnh STTC bt u bn ngoi STBC
kt hp. Nu s lng anten thu l 1 hoc ti a l 2, mt dy n STBC ni vo nhau
vi m AWGN trellis thun ty

73
N TT NGHIP
Hnh 3.16 c tnh m STBC, STBC+TCM, STTC s dng m 4 v 8 trng
thi vi 2 anten pht, 2 anten thu (IEEE, 2001)

74
N TT NGHIP
Hnh 3.17 c tnh m STBC, STBC+TCM, STTC s dng m 4 v 8 trng
thi vi 2 anten pht, 3 anten thu (IEEE, 2001)
3.4 Qu trnh p dng mng thng tin di ng 4G cho viettel
Hin nay Viettel vt qua cc nh cung cp dch v truyn thng tr thnh
nh cung cp dch v ln hng u Vit Nam. Viettel ang y mnh pht trin thm cc
vng ph sng v mua sm thm cc thit b mi. Th trng di ng Vit Nam hin ti
c nh gi l tng trng ng th 2 trn th gii sau Trung Quc, s thu bao
khng ngng tng, do nhu cu v vic s dng cc dch v ngy cng cao. Trong thi
gian gn y, mng Viettel lin tc pht trin c v vng ph sng v cc loi hnh dch
v.

75
N TT NGHIP
Hin nay Viettel a vo s dng GPRS p ng nhu cu s dng cc dch
v d liu ngy cng cao ca cc thu bao. Cc dch v ch yu ca GPRS nh: WAP,
truy nhp Internet c hai phng thc truy nhp Internet bng GPRS l truy nhp gin
tip v truy nhp trc tip. Dch v nhn tin a phng tin. Video, xem cc on phim
ti v, xem video trc tuyn. Ngoi ra cn c dch v thng mi in t di ng, dch
v ngn hng, qung co trn in thoi di ng Vi nn tng h tng c s, cng vi
s pht trin ca mng di ng Viettel hin nay, chng ta thy rng mng thng tin di
ng ny hon ton c th pht trin ln 4G trong tng lai. pht trin cc h thng
GSM hin ti ln 4G, nh khai thc dch v cn ch ti nhng vn sau:
- Viettel Mobile s tp trung cho vic pht trin mng li thng qua vic xy
dng mt mng li IP c tc cao, s dng nhng cng ngh tin tin. Song song vi
qu trnh ny, Viettel Mobile s nng cp MSC Server, MGW. MGW
- ng thi vi cc cng ngh tin tin trong 3,5G cng gii quyt c cc vn
i vi mng truy nhp v tuyn. Vi cc cng ngh HSDPA v HSUPA cho php
ci thin ng k tc d liu ti ngi s dng. y l nn tng v l bc chun b
cho vic pht trin tip theo ln mng 4G ca Viettel Mobile.
- Thay th dn IPv4 thnh IPv6.Bng vic nng cp qu trnh m ha knh. a
ra mt s giao thc chun cho cc mng d dng trong vic tch hp cc mng vi
nhau. Vi cu trc ny, th Viettel Mobile c th cung cp c nhiu loi hnh dch v
khc nhau, c tc cao, cht lng tt. Lc ny, mng c th tch hp c vi nhiu
mng khc nhau nh WiMAX, WLAN,

76
N TT NGHIP
KT LUN
Hin nay mt trong th loi thng tin di ng ang pht trin nhanh nht l thng
tin di ng t bo. Nhu cu s dng h thng ny khng ch tng v s lng m c v
th loi. Nhiu gii php k thut v cng ngh c nghin cu v p dng vo
mng. Cc th h mng di ng t bo ni tip nhau ra i. V vy h thng thng tin di
ng 4G ra i l mt tt yu nng cao cht lng dch v cho ngi s dng.
Tm li, trong n ny chng ta trnh by cc ni dung bao gm:
- Tm hiu tng quan v h thng thng tin di ng 4G v mi trng v tuyn a
hp trong mng 4G.
- Tm hiu c cc phng php m ha c ng dng trong thng tin di
ng 3G nh m khi, m xon v m turbo.
- Nghin cu phng php m ha khng gian-thi gian c xut s dng
trong h thng thng tin di ng 4G, c bit l tm hiu k v 2 loi m ha khng
gian-thi gian: m khi khng-gian thi gian v m trellis khng gian-thi gian.
- Thit k c kt qu m phng cho h thng Alamouti, kt qu m phng m
khi khng gian-thi gian v m trellis khng gian-thi gian kim chng li c tnh
ca cc loi m ny c cp trong phn l thuyt.
HNG PHT TRIN CA TI
- Nghin cu thm cc phng php m ha khc cho h thng thng tin di ng
4G c th rt ra c u v nhc im ca tng loi m ha.
- So snh vi cc loi m ha s dng trong h thng 3G c th thy c s
khc bit gia chng.
- Nghin cu ng dng cc phng php m ha khng gian-thi gian vo cc h
thng bng rng nh OFDM v CDMA

77
N TT NGHIP
TI LIU THAM KHO
Ti liu ting Vit
[1]. TS. Nguy n Pha m Anh Du ng, Gio trnh Thng tin di ng th h ba, NXB Bu
in, 3/2004.
[2]. TS. Nguy n Pha m Anh Du ng, Gio trnh Thng tin di ng, NXB Bu in,
6/2002.
[3]. TS. Nguy n Pha m Anh Du ng, Thng tin di ng GSM, NXB Bu in, 1999.
Ti liu ting Anh
[4]. Advanced Wireless Networks: 4G Technologies . Savo G. Glisic. University
ofOulu, Finland. 2006. John Wiley & Sons, Ltd.
[5]. Introduction to 3G Mobile Communications Second Edition. Juha Korhonen.2003.
Artech House, Inc.
[6]. Multicarrier Techniques for 4G Mobile Communications. Shinsuke Hara, Ramjee
Prasad. 2003. Artech House, Inc.
[7]. Space-Time Coding. Branka Vucetic. University of Sydney, Australia. Jinhong
Yuan. University of New South Wales, Australia. 2003. John Wiley
[8]. Space-Time Codes and MIMO Systems. Mohinder Jankiraman. 2004. Artech
[9]. Space-Time Codes for High Data Rate Wireless Communication: Performance
Criterion and Code Construction. Tarokh, V., N. Seshadri, and A. R. Calderbank.
March 1998.IEEE Trans. Inform. Theory. Vol. 44, No. 2, March 1998, pp. 744765.
Ti liu trn Internet
[1]. http:// ebook@free4vn.org
[2]. http:// tchdkh.gov.vn, Truy cp cui cng ngy 10/5/2010

78
N TT NGHIP
[3]. http://tcbcvt.gov.vn, 4G - H thng thng tin di ng ca tng lai_KS. Nguyn
Trung Kin, Truy cp cui cng ngy 10/5/2010
[4]. http:// tailieu.vn
[5] . http://www.dientuvienthong.net

79

Các Phương Pháp Mã Hóa Kênh Trong Thông Tin Di Đ NG 4G

Uploaded by

Document Information

Original Title

Copyright

Available Formats

Share this document

Share or Embed Document

Sharing Options

Did you find this document useful?

Is this content inappropriate?

Copyright:

Available Formats

Các Phương Pháp Mã Hóa Kênh Trong Thông Tin Di Đ NG 4G

Uploaded by

Copyright:

Available Formats

N TT NGHIP

. Kt qu l ng bao ca tn hiu thu mi

ca bin ngu nhin phn b Rayleigh

Trong K l h s Rician, c nh ngha l t s ca tia trc tip vi cc thnh

k hiu cho chuyn v Hermitian ca

. V vy, PEP tr thnh

You might also like