ECE 402: Communications Engineering
Homework 8 (Fall 2009)
Due: Thursday 12/3 (at the *beginning* of class)
1. Consider a channel that occupies the frequency band 820920 kHz. Suppose we want to transmit
an MP3 audio ﬁle (200 kb/s) over this channel in real time using PSK bandpass signaling with a
raisedcosine rolloﬀ characteristic (
r
= 0
.
5). Find a PSK constellation, carrier frequency, and symbol
rate that occupies the entire band.
2. Suppose data are transmitted over the baseband system below using 2PAM modulation with transmit
pulse
g
(
t
) = sinc(2
t/T
) and receive ﬁlter
H
r
(
f
) = cos(
πfT/
2), where
f
b
= 1
/T
is the symbol rate.
( )
a t
( 29
y t
ˆ( )
a t
⊗
( 29
comb
T
t
( 29
x t
Channel
Modulator
Rcv Filter
Threshold
( )
G f
( )
c
H
f
( )
r
H
f
(
29
y nT
( )
( )
( )
( )
c
r
P f
G f H
f H
f
=
system pulse
( 29
z t
(a)
Suppose that the transmitted signal travels to the receiver by two paths, so that
z
(
t
) =
x
(
t
+
T/
4) +
x
(
t

T/
4) is received. Find the channel frequency response
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 Fall '08
 Townsend
 Frequency, maximum data rate, Project III

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