802.11, :
1. 802.11;
2. 802.11b;
3. 802.11a;
4. 802.11g;
5. 802.11n.
Wi-Fi . , . 2,4 5,5 . 2,4 , 802.11, 5 . , ISM (Industrial, Scientific, Medical), , - . 2 MAC.
802.11
() 802.11 2,4 2 /. 802.11 2 , [10]:
FHSS (Frequency Hopping Spread Spectrum);
DSSS (Direct Sequence Spread Spectrum).
FHSS GSM EDGE, DSSS CDMA. FHSS 2,402 2,480 79 . 79 1. , . 2,5 . FHSS DSSS 2/, 802.11b, 802.11a, 802.11g, 802.11n.
802.11b
802.11b HR-DSSS (High Rate Direct Sequence Spread Spectrum). 11 , 11 B1=(10110111000). - (DBPSK DQPSK, ). 11 1 2 /. 802.11b 11 5,5 /. (-, Complementary Code Keying), 8 , 11 /. 5,5 / 4 . FEC. 802.11b+ 22 /. 802.11b , /. . , 2,4 . 802.11b . 2,4 802.11a 5 . . 802.11b . 5,5; 11 22 /.
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802.11a
802.11 5 54 /. , Wi-Fi. 802.11 OFDM (Orthogonal Frequency Division Multiplexing). OFDM - . , . 124 (2010 ) 802.11a : 5,150-5,350 5,650-6,425 . 802.11a 20 . 52 . 48 , - . . . : 1/2, 2/3, 3/4. 3/4, . BPSK 125 /. 48 6 / (48*125 /.). QPSK 12 /. 16- QAM-16, 4 , 24 /. 64- QAM-64 - 54 /. 24.1 802.11.
24.1. 802.11
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BPSK | 1/2 | |
BPSK | 3/4 | |
QPSK | 1/2 | |
QPSK | 3/4 | |
QAM-16 | 1/2 | |
QAM-16 | 3/4 | |
QAM-64 | 2/3 | |
QAM-64 | 3/4 |
802.11 5 , ( 2,4 300 , 5 - 100 ).
802.11g
802.11g 802.11b. 2,4 54 /. 802.11a 802.11a . DSSS OFDM. 802.11g 2400-2483,5 .
802.11n
802.11n . , 802.11a OFDM (2,4 5 ). :
2400-2483,5 ;
5150-5350 ;
5650-6425 .
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20 40 , 20 . 24.2 802.11n 20 [90,91]. 40 , ( 52 108). 800 400 .
MIMO (Multiple Input Multiple Output), .. . . , . MIMO , . I ( ) . . MIMO , /. 802.11n , /.
24.2. 802.11n 20
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BPSK | 1/2 | 7,2 |
QPSK | 1/2 | 14,4 |
QPSK | 3/4 | 21,7 |
QAM-16 | 1/2 | 28,9 |
QAM-16 | 3/4 | 43,3 |
QAM-64 | 2/3 | 57,8 |
QAM-64 | 3/4 | 65,0 |
QAM-64 | 5/6 | 72,2 |