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COSC 4214: Digital Communications
Assignment # 3: Intersymbol Intereference, Equalization, and Broadband Modulation
Coverage: Sections 3.3 – 3.4 (upto 3.4.3.2) and Sections 4.1 – 4.4
Due Date: November 21, 2006
In Chapter 4, we covered a wide range of digital modulation schemes including Pulse Shift Keying (PSK),
Amplitude Shift Keying (ASK), Phase Shift Keying (PSK), and Amplitude Phase Keying (APK). We also
covered coherent (or synchronous) detection of PSK, where the phase and frequency of the carrier signal is
known precisely. Please cover the coherent detection for FSK (section 4.4.4), which was not covered explicitly
in the class. Noncoherent detection schemes do not require exact knowledge of the phase and the frequency of
the carrier to demodulate the transmitted signal. The coverage of the noncoherent detection schemes is beyond
the scope of the course.
An important measure of performance used to compare the performance of the digital modulation schemes is the
probability of error
P
E
. The derivations of the probability of error for various modulation schemes were not
explicitly covered in the lecture but you should know the following expressions for the probability of error
P
E
for
BPSK and BFSK corrupted with additive White Gaussian noise (AWGN) and detected using coherent detection
schemes.
BPSK (Coherent Detection):
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
=
0
2
N
E
Q
P
b
B
BFSK (Coherent Detection):
⎟
⎟
⎠
⎞
⎜
⎜
⎝
⎛
ρ
−
=
0
)
1
(
N
E
Q
P
b
B
where
E
b
is the signal energy per binary symbol,
N
0
/2 is the power spectral density (PSD) of the AWGN, and
ρ
is the correlation coefficient between the two transmitted waveforms used in BFSK.
Problems 5 to 10 apply these formulas for calculating the probability of bit error including the derivation of the
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