Digital Signal Processing Reference
In-Depth Information
x
(
n
)
0
y
(
n
)
x
(
n
)
s
(
n
)
0
s
(
n
)
0
H
(
z
)
0
F
(
z
)
0
C
(
z
)
P
P
+
channel
s
(
n
)
1
x
(
n
)
1
s
(
n
)
1
noise
F
(
z
)
1
H
(
z
)
1
P
P
x
(
n
)
s
(
n
)
s
(
n
)
M
−
1
M
−1
M
−
1
F
(
z
)
M
H
(
z
)
M
P
P
−
1
−
1
transmitter
filters
receiver filters
Figure 3.26
.The
M
-user transmultiplexer system with redundancy (
P>M
).
guard bands
F
1
F
M
−1
F
0
F
0
(a)
ω
0
π
/
P
2
2
π
X
X
1
X
0
frequency-multiplexed signals
0
(b)
ω
0
π
/
P
2
2
π
Figure 3.27
. (a) Examples of frequency responses of filters in the transmultiplexer
with redundancy, and (b) examples of outputs of the filters. See text.
3.8.3 Types of distortion in transmultiplexers
The received signals
s
k
(
n
) in general are different from
s
k
(
n
) for several reasons.
1. First, there is
interchannel
interference. This means that
s
k
(
n
) is affected
not only by
s
k
(
n
)
,
but also by
s
m
(
n
)
,m
=
k.
This is also sometimes called
multiuser interference, or
MUI
. The term “multiuser” interference arises
from the fact that historically the transmultiplexer was used to multiplex
several users in TDM format into an FDM format [Bellanger and Daguet,
1974]. Today, the same mathematical structure can be used to describe a
wider range of communication systems as we shall see.
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