- (. 21.6).
. 21.6. - -
, .
, 4 . .
- () . , - () .
, . .
, . .
. .
.
, . 64 /c. (encoder) , .. , . . (decoder) . GSM LPC (Liner Predictive Coding). , , , , . , , . , m . 20- , 260 . , 4.92 (64 / *20 )/260 , 64 /c 13 /c.
( ) . DRT (Diagnostic Rhyme Test ). , ( , ), , . , .
|
|
DAM (Diagnostic Acceptability Measure ). , , -, . , (Mean Opinion Score MOS). , - . . 21.3 GSM - .
21.3. MOS
, / | MOS | |
4.12 | ||
RPE-LTP ( GSM) | 3.58 |
/ , .. , , .. BTS MS. , HDLC, , TCP. . , , - .
, , . , , , . ( ) , / , , . GSM , (frequency hopping). , . . , . , .
, GSM, 260- :
|
|
1a: 50 , .
1b: 132 , .
2a: 78 , .
50 3- . 260 . 53 , 132 1b, 4 - (.. 189 ), . . FEC (Forward Error Correction).
(. 21.7) K , k n- , n > k, .
2 ( Kk ) K , n 2. n, k, K (n, k, K).
. 21.7. (4, 2, 5)
(n = 4, k =2; R = k/n = ½)
R=k/n . K ( ), .
, , 1 , 2, 3, 4, 5 , , , . k = 1, .. , . , . 21.7 , k = 2.
GSM 189 (2, 1, 5), 456 (189*2 78 ). 13 / 22.8 / - (13 / *456 /260 ).
. 21.8 20- .
. 21.8. 20-
(2.1.5) . . , , , . . 260/456, .. 0,57. (.. ). . , .. , , , . ( ) . , , , . , () , . , , . , , . , , .
, , , , . . 21.9, , ai, bi, ci. , , . , , .. .
|
|
. 21.9.
n ( ) , k . k*n (. 21.10), . , a 1, a 2,..., an, b 1, b 2,..., bn, k 1, k 2,..., kn, : a 1, b 1,..., k 1, a 2, b 2,..., k 2, an, bn,..., kn. , , . , , .
. 21.10.
GSM - . 456 20- 8 . 57 , , 4 , ( ) . , , .
70-80 20 , 10-20 40 .
. , SACCH, FACCH, FCCH, PCH, AGCH, SDCCH (224, 184), (2, 1, 5) , . RACH, SCH , (2, 1, 5), . , . . 21.11 MS BTS. , .
23 , .. 184 . ( ) 40 - CRC.
184/456=0,4. , , , . 21.10.
|
|
. 21.11.
(. 20.8) , , . , .. () () . , - . , , .
, : AM (Amplitude Modulation AM), (Frequency Modulation FM) (Phase Modulation PM). , , (Quadrature Phase Shift Keying QPSK), (Binary Phase Shift Keying) . , , , () . GSM MSC (Gaussian Minimum Shift Keying GMSK). MSK , .. MSK . QAM ( 3, 3.4), GSM, WiMAX .