xDSL :
- SHDSL(TC-PAM) 10 /;
- ADSL (DMT) 48 /;
- VDSL(OFDM) 100 /.
19. ISDN ? ISDN?
Integrated Services Digital Network ( ) , , . .
:
- ISDN . ISDN -;
- ISDN . ;
ISDN
LT: ; ISDN;
NT1: 1: , ( ISDN), , () ; 2- U- 4- S/T-;
NT2: 2; , , ;
NT: ; , NT1 NT2;
TA: ; , -ISDN ISDN;
TE: ; , , .;
TE1: , ISDN (.. ISDN);
TE2: , ISDN-.
ISDN :
U: 2- , - NT1 LT1 ISDN . 2B1Q.
T: 4- NT1 NT2
S: 4- , NT ( NT2) TE (TA)
R: -ISDN -ISDN TE2
ISDN
ISDN BRI - Basic Rate Interface , ;
ISDN PRI - Primary Rate Interface , .
ISDN- BRI: B-, 64 \, , ISDN; D-, 16 \ ISDN ISDN. IP, X.25. ISDN BRI 144 \, ( ) 192\.
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ISDN- PRI (, .): 30 - , 64 \; 2 D- 64 \; 30B +2D-2048 \. (30*8B+8D+8F)*8K = 2.048 Mbps : 23B + D (23*8B+8D+1F)*8K = 1.544 Mbps
ISDN: BRI physical-layer specification: ITU-T I.430. PRI physical-layer specification: ITU-T I.431.
ISDN: LAPD (Link Access Protocol) . ITU-T Q.920, Q.921, Q.922, Q.923.
ISDN: ITU-T Q.930 (I.450). ITU-T Q.931 (I.451).
ISDN
: 3.1 3,1 . : 64 / ISDN 3.1 . :
ISDN : - ;
- ; - ; - ; - ISDN ; - ISDN- ; - ; .
20. ? ?
- Non Return to Zero (NRZ) , .
- Return to Zero (RZ) , . - RZ RZ .
() - Alternate Mark Inversion (AMI) - , : , - . , , .
-3 - High-Density Bipolar (HDB-3). , AMI, , . (0000) , , , .
2 B1Q.
2B1Q (2 Binary 1 Quaternary) U BRI ISDN (Integrated Services Digital Network).
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2B1Q - () .
. , .
, (data rate - ) (symbol rate).
-.
TC-PAM . TC-PAM Trellis Coded Pulse Amplitude Modulation ( -). ( ) 4 ( 2B1Q) 8, 16, 32- .
QAM.
QAM
(Quadrature Amplitude Modulation) - .
(I) (Q) (fc), /2.
Z .
CAP. - (Carrierless Amplitude-Phase Modulation) QAM, . , 64 128 . , , , ,
.
DMT (Digital-Multi-Tone) , , . QAM, , . 4,3125 . (, )
OFDM (Orthogonal Frequency Division Multiplexing) DMT. DMT, OFDM . , OFDM, DMT.
. , DMT , . . , , , .
21. DSL? ?
:
- ;
|
|
- ;
- ;
- ;
- .
DSL:
DSL - FSAN NM Noise Margin ( ) (upstream) (downstream) .
, , . .
, .
22. DSL?
DSL , :
.
.
( ).
- .
.
( ).
.
.
( ).
( ).
( ).
( / ).
.
.
.
23. ? ? ? ?
7 (OSI Open System Inteconnect), xDSL , , .
, .
xDSL - () () .
() , .
, , , .
, .
, 15,438 . () 77,385 . ().
:
:
;
, ;