Digital Communications

Intersymbol Interference-2

Question 1
Marks : +2 | -2
Pass Ratio : 100%
The symbol of the probability under the tail of Gaussian pdf is called as
Complementary error function
Co error function
Complementary error & Co error function
None of the mentioned
Explanation:
The co error function or complementary error function is a commonly used symbol for probability under the tail of Gaussian pdf.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
An error in binary decision making occurs when the channel noise is
Greater than the optimum threshold level
Lesser than the optimum threshold level
Greater or Lesser than the optimum threshold level
None of the mentioned
Explanation:
An error will occur when s1(t) or s2(t) is sent and if the channel noise is greater or lesser than the optimum threshold level.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
Matched filter provides _____ signal to noise ratio.
Maximum
Minimum
Zero
Infinity
Explanation:
A matched filter is a linear filter designed to give a maximum signal to noise ratio power at the output.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
The likelihood ratio test is done between
Likelihood of s1 by likelihood of s2
Likelihood of s2 by likelihood of s1
Likelihood of s1 by likelihood of s1
None of the mentioned
Explanation:
The likelihood ratio is given with the help of conditional probabilities.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
The detector that minimizes the error probability is called as
Maximum likelihood detector
Minimum likelihood detector
Maximum & Minimum likelihood detector
None of the mentioned
Explanation:
For the signals that are equally likely, the detector used to minimize the error probability is called as maximum likelihood detector.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
Example for antipodal bandpass signaling is
BPSK
ASK
FSK
MSK
Explanation:
One type of antipodal bandpass signaling is binary phase shift keying.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
According to the rule of minimizing the error probabilities, the hypothesis should be like if the priori probabilities are ________ than the ratio of likelihoods.
Lesser
Greater
Equal
None of the mentioned
Explanation:
The rule of minimizing the error probabilities show that the hypothesis should be like if the ratio of likelihoods should be greater than the priori probabilities.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
The impulse response of the filter is the ________ of the mirror image of the signal waveform.
Delayed version
Same version
Delayed & Same version
None of the mentioned
Explanation:
The matched filter’s basic property is that the impulse response of the filter is the delayed version of the mirror image of the signal waveform.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
Optimum threshold value is given by
a0+a1/2
a0-a1/2
a0/2
a1/2
Explanation:
The optimum threshold level value for error probability reduction is given by a0+a1/2.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
For a M-ary signal or symbol the number of likelihood functions are
M
M+1
M-1
2M
Explanation:
For a M-ary signal there will be M likelihood functions representing M signal classes to which a received signal might belong.