
CSE5501: MOBILE & DISTRIBUTED COMPUTING SYSTEMS
Lecture 3: Wireless LANs
18
Direct Sequence Spread Spectrum
Direct Sequence Spread Spectrum
Direct Sequence Spread Spectrum
•
•
DATA SIGNAL SPREAD BY A PN CODE
DATA SIGNAL SPREAD BY A PN CODE
•
•
PROPERTIES OF PN CODE
PROPERTIES OF PN CODE
•
•
CHIP RATE
CHIP RATE
•
•
DS PROCESSING GAIN
DS PROCESSING GAIN
•
•
PN CORRELATION AT RECEIVER
PN CORRELATION AT RECEIVER
•
•
PSK DATA MODULATION
PSK DATA MODULATION
G
G
P
P
(dB) = 10LOG (
(dB) = 10LOG (
CHIP RATE
CHIP RATE
DATA RATE
DATA RATE
)
)
AP96358 2
AP96358 2
-
-
11
11
FREQUENCY (MHz)
FREQUENCY (MHz)
CW SIGNAL
CW SIGNAL
AMPLITUDE
AMPLITUDE
(
(
dBm
dBm
)
)
SPREAD SIGNAL
SPREAD SIGNAL
AMPLITUDE
AMPLITUDE
(
(
dBm
dBm
)
)
2.45
2.45
2.44
2.44
2.43
2.43
2.46
2.46
2.47
2.47
1
1
0
0
DATA
DATA
BARKER
BARKER
CODE
CODE
SPREAD
SPREAD
DATA
DATA
CHIP
CHIP
CLOCK
CLOCK
0
0
3
3
6
6
9
9
12
12
15
15
18
18
0
0
0.2
0.2
0.4
0.4
0.6
0.6
0.8
0.8
1.0
1.0
1.2
1.2
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