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Binary or Antipodal Signaling
Reading:
Textbook section 7.1 and 7.2.
Material covered:
1. PAM and PPM transmission
•
Recall: PAM uses multiple levels of amplitude to encode info,
∑
∞
∞
=

=
n
n
nT
t
h
a
t
y
)
(
)
(
where
}
3
,
,
,
3
{
A
A
A
A
a
n
+
+


∈
for 4PAM.
•
Recall: PPM uses shifted position of a pulse within
T
to encode info.
•
We can generalize
M
ary modulation where we have
M
different symbols being
transmitted. Let:
PAM
PPM
Let the symbol 1 be represented by
)
(
1
t
s
Let the symbol 2 be represented by
)
(
2
t
s
Let the symbol
M
be represented by
)
(
t
s
M
•
Symbols are transmitted consecutively and independently every
T.
•
Consider transmission of one symbol, say
)
(
t
s
, which can be any of the symbols.
•
Channel adds noise so that received signal is
)
(
)
(
)
(
t
n
t
s
t
r
+
=
•
Often noise is assumed to be Additive White Gaussian Noise (AWGN) with power
spectral density
2
)
(
0
N
f
S
n
=
.
•
Question: At the receiver, how do we decide what symbol was sent, given corruption
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 Spring '09
 Hui

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