- (MPDU) , PLCP- ( 2.12). (SYNC) 16- (SFD) F3A016. PLCP- SIGNAL ( ), SERVICE ( , PBSS-) LENGTH ( , ). 16- CRC.
2.12 - 802.11b PHY-
IEEE 802.11b : ( 2.13). (128 56 ), , , . , 1 /, 1 /, 2 /. , SIGNAL SERVICE. IEEE 802.11b .
2.13 - 802.11b
IEEE 802.11 , , Ethernet. . , . IEEE 802.11b.
, IEEE 802.11 DSSS (Barker) 11 : 1 = (10110111000). 2 ( Ȼ) , . . B1, B1. 11 . - (DBPSK DQPSK, ). 11 1 2 /.
IEEE 802.11b 11 5,5 /. - (Complementary Code Keying ). Intersil ( Harris Semiconductor) Agere Systems ( , Lucent Technologies).
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, 5,5 11 / , , 1 2 /, - . , 8 (complex chip), 1 2 / 11- . 8- 4, 8 . 11 /, .. 8 4 8 5,5 11 /.
5,5 /, 4 (b0, b1, b2 b). (b2 b) 8 , 2.3, {cl, 2, , 4, 5, 6, 7, 8} . 2.3 j , - 1, , .
2.3 -
(b2, b) | 1 | 2 | 3 | 4 | 5 | 6 | 7 | 8 |
j | j | -1 | j | -1 | ||||
-j | -1 | -j | j | -j | ||||
-j | -j | -1 | -j | j | ||||
j | -1 | j | -j | j |
, , (b2, b), (b0, b1) , DQPSK, ( 2.4). 4- PSDU, 0, , . , DQPSK, QPSK, , PSDU, DQPSK , 2 /.
2.4 -
(b0,b1) | ||
- | ||
- |
8 , .
11 /, PSDU 8 . 6 , 8 , 64 , , (b2, b) . (b0,b1) , 5,5 / .
-? , -. - , . , . , - 3 ( ), QPSK- 11 / 22 /. , - , . IEEE 802.11b .
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. , . - , 2 . (Packet Binary Convolutional Coding). IEEE 802.11b () . ( 2.14) Alantro Communications, 2000 Texas Instruments. IEEE 802.11b 5,5; 11 22 /.
2.14 - -
, . 5,5 11 / ( 2.15.). . d (c0, c1). 11 / 0 c1 QPSK-. 5,5 / BPSK-, c0 1. 22 /, ( 2.15.): (c0-c2) 8- 8-S-.
PSK- . s ( 2.9) (s = 0), (s = 1). s 256- S. U = 338Bh, .
2.15 - -: 5,5 11 /; 22 /
, 11 5,5 /, 64 . , -. / , ( 2.16). . , - Texas Instruments .
Texas Instruments, 22 / IEEE 802.11b, IEEE 802.11b+ 100 , D-Link NDC. 22 /. , . , , . Intersil Texas Instruments. , -.
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2.16 - ( Texas Instruments 100)
, 22 / , 54 /.