. -, QAM-M (Quadrature Amplitude Modullation), - , .
-16. 11.20
11.20 -16
; - I, Q; ; Σ .
bi 4 mi1mi4 4 . I Q, . S(t)=A(t)sin[ωt+φ(t)],
(t)= ;
() 11.4
11.4
11.21 -16.
11.21 -16
, -16, 11.22. -16.
11.22 -16 -16
-16 -16 -16 (d > d).
-64 -256 6 8 .
, -32 (5 ). 11.23.
11.23
Globe Span Inc Q, (Carrier Less Amplitude modulation / Phase).
Q.
11.7 OFDM (COFDM)
( - )
80- . OFDM (Orthogonal Frequency Division Multiplexing). . (DVB-T, ISDB-T, DAB-T, ATSC-8VSB) DRM. , , COFDM (OFDM c ).
:
2, 4, 6 ( - ) QAM (4, 16, 64) ( 300 6800 ). QAM . , , , QAM-4, .
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(), (. 11.24). - . , - .
, . , (11.2), 1/.
11.24 - OFDM
OFDM . , . .
QAM, , . , .
COFDM QAM-64 . , COFDM , ( ). ... . , COFDM (. .. 8.2.3).
, .. .
11.25
COFDM 11.25 DRM . . COFDM .
11.8 CDMA
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( )
[21] CDMA (Code Division Multiple Access). CDMA, , . , , , , . CDMA . : FH (Frequency Hopping) ; TH (Time Hopping) ; DS (Direct Secuence) . : FH/TH, DS/TH, DS/FH, DS/FH/TH.
FH CDMA : N , () . τ = /N, , . .
TH CDMA , . , .
CDMA DS CDMA, . .
: , (, , ), ( ) . . , .
DS CDMA . , ϻ , 11.26. , .
11.26 CDMA
, , 11.26. , .
, , , . . , , .. .
11.7 C CDMA
11.27 CDMA, e .
DS CDMA .
, , - .
DS CDMA ; , .
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