Praktika_8-2
.pdf
4
1.
:
1.(SDMA);
2.(TDMA);
3.(FDMA);
4.(CDMA);
5..
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CDMA,
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Pure-Aloha (
ALOHA).
1. Pure-ALOHA. a) ; b)
,
, S-ALOHA (ALOHA
).
.
,
.
2. S-ALOHA
, ALOHA
(R-ALOHA).
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1. ( ):
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2.
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3. R-ALOHA. .
( =5 , V=6
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4. ALOHA
ALOHA (PureALOHA S-ALOHA) .
, ,
, .
CSMA (Carrier Sense Multiple Access -
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CSMA:
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CSMA, :
1.CSMA/CD (Carrier Sense Multiple Access with Collision Detection —
).
,
, , jam signal ( ) ,
.
CSMA
.
2.CSMA/CA (Carrier sensing multiple access with collision avoidance -
).
. ,
, jam signal.
, jam signal,
. jam signal
,
CSMA/CA CSMA/CD ,
, jam- . «Collision Avoidance» — ( ).
5.
:
1
16 .
32 ,
64 4- . ALOHA
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Pure-ALOHA?
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= = (64 + 4) 16 32 |
0.265625 |
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1024 1024 |
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S-ALOHA. Pure |
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ALOHA 0,184. |
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= 1024 1024 0.18 |
46 |
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16 32 8 |
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68-46=22 . |
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,
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G1(x)=X6+X4+X3+X+1 |
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[6 5 2] |
, 6.
6
. 26-1=63
, 6, 4, 3 1
. 6, 5 2 .
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XOR |
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XOR |
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XOR
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2400 0.5 ,
, =10dBi
0.1 ?
20dBm 10dBd;
0.3 =6?
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10 |
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1 = 1000 = 1000 |
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1 = 1.64 10 |
= 1.64 10 = 16.4 |
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–
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,
. : 1 1 = 1.64
2 2 = 1.8
, .
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2 2 |
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0.3 10 2400 10 |
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= 133.5 |
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0.1 10 |
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1.2 , 2 .
0.9 , – 350 ,
1.25 .
25 . 15.5 , – 15 .
1 .
, ?
: a=900 , b=350 ,
=1250 , ht=hr=20 .
6.
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10 = 0.5 |
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1200 10 |
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7. |
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= 550 ( ) |
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1 . , N=1.
d1=a=900 , d2=b+c=1600
d1=a+b=1250 , d2=c=1250 .
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1 1 |
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0.25 900 1600 |
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8. |
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1 |
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1 1 |
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900 + 1600 |
= 12 |
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