-270
1 ;
2 ;
3 ;
4 ;
5 ;
6 ;
7 .
24. ? ?
, , , , .
, , :
- R(/);
- L(/);
- (/);
- G(/).
. . . , , L
R .
, . :
:
1 R; 2 G;
3 L
25. . ?
, ,
:
1. . ,
2.
26. () SHDSL ?
ITU-T G.991.2 , PMS-TC (Physical Medium Specific Transmission Convergence) TPS-TC (Transmission Protocol Specific Transmission Convergence). SHDSL (LTU Line Terminator Unit) (NTU Network Terminator) DLL (Digital Line Loop) SHDSL (Core SDSL). R (Repeater). PMD (Physical Medium Dependent) SHDSL , , , ,
|
|
, SHDSL TMS-TC (Transmission Protocol Specific Transmission Convergence) :
;
;
;
;
.
. SHDSL 8 , .
27. SHDSL ? ?
-.
- - - (Trellis Coded Pulse Amplitude Modulation).
4 ( 2B1Q) 32 , . (Trellis coding) , . , , -16, 2B1Q 20% 35% .
- Z-
n -, 3≤ n ≤36, Z-, 0≤ ≤7
--16 ESHDSL 192 3848 / 8 / ( - 3≤ n ≤60)
--32 768 5696 / 8 / ( - 12≤ n ≤89).
28. (BER) - (PAM).
, . :
- , , , ( - ).
- , ( , , , ).
Q(*) , Ebcp=Pcp*T , Ebcp/N0 , .
|
|
/ (SNR)
1 SNR, W. , , , .
2 W, SNR. , , , .
3 SNR .
2 3 , .