, . , . (. . 17.1) . () ( , , .). , " " - , ( ).
. 17.1. : 1 () ; 2, 3
, , . 17.1 . / , , . -, ( ). , , , . , ( /) . (CRC Cyclic Redundancy Check), 2 4 , . . . ( arj, rar, pkzip .), . , (""). , , ( ) "". , ( ) , , , . . / . 17.1, , , , , . , ( ) , /. , (, , ) , () ( 0 +5 ). , RS-232C "" (3...12) +(3...12) . , , .
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() :
V (/), , , , ( ), S/N / . . 17.2( " ").
. 17.2. V - S/N
, , . , . "" , , "" .
, , , :
n () (). ( ) k , n=2k. , n / S/N .
, , :
p , , , , . ITU -T p<=3*10-5, p<=10-6 ( 10-9). - (3) (2). (k=1, n=2) p=1/2 (3) , V=0, p->0 p->1 . , p=1/2 ( ). p->1 ( , ) .
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, V . V / S/N V . , (). , . (, , , ) , /. , , . / 35 ( 3000 56 ), / ( , , 33600 /). 56 ( ) , , ( !).
, ( " ")
() , , , , , . , . . , , - . - , .
, , , , " ". .
, , ( ).
(. . 17.3). - ( ) . .
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. 17.3. ( )
220 () , ( , , .) (, .). , (, ..). "" , . 100...150 , , (1,5...80 ), (2...40 ) ( 15 ). .
, , (power line modems). 10 /c . , , . , ( ). , Ethernet ( 14 /c). . ( ). (, ) , , .
( ), , "", . , ( "" "" ). , "" "" . ( , .), . .
, . , ( ).
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( ) "" , .
, (CATV), . , "" : cable modems. . , , (100 / Fast Ethernet .). , , ( 10 /) ( 40 /). .
, - -, IP- ( ) (VPN).
(Digital Subscriber Line Loop xDSL) . () . xDSL , . , . , . xDSL .
xDSL :
- HDSL ;
- ADSL ;
- ISDL ISDN ;
- SDSL ;
- VDSL Very HDSL;
- RADSL ;
- UADSL .
"" ISDN 20- . 2- 128 / ( 160 /). 2 xDSL :
- ADSL, () 8 1,5 /, 1,5 / 640 /. - " " 1 /.
- SDSL, 2 / ( 1,5 /).
( ). , . , " ". . xDSL. " " - .
(-) , ( , ..). () , - (radio modems). (2000...2500 ) . , , . , , - , -. 2 /. , ( ~ 900 ) ( ) 50 .
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. : 6/4 ( 14/12 ). 50 /. , . , , 100, (TDMA) 100*2*(37100 /300000 /) 24 . , "" , - SDU (Satellite Delay compensation Unit).
, , . HPNA (Ethernet ) Bluetooth ( ). , " " , 100- . (, ), ( , , "" ). , ( power line modems, cable modems radio modems) . , , , , .
, , , V.34, V.90 V.92. xDSL , , . ( ) ( , ), .
, , , . , ( ).
(leased) | (switched) |
(many-points) | (point-to-point) |
(tone dial) | (pulse dial) |
(, V.34) , . , - (), ( ) , . " ", .
, - .
:
- ( ) ;
- - ( ), ;
- 600 20% 400 1800 . , ;
- ( , ) .
, , , 300..3400 . 8....12. . :
- ( 1900 );
- - ( );
- ( );
- ( );
- ( ).
, : , , , .
"" , , , (. ). , - S/N, , . 17.2, "" 10 / V.34 - 15 . , , - .