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WorksheetsDIGITAL COMMUNICATION MCQ
Total questions: 45
Worksheet time: 45mins
Name
Class
Date
1.
The process of converting the analog sample into discrete form is called
a)
Modulation
b)
Multiplexing
c)
Quantization
d)
Sampling
2.
The negative statement for Shannon's theorem states that
a)
If R > C, the error probability increases towards Unity
b)
If R < C, the error probability is very small
c)
Both a & b
d)
None of the above
3.
The technique that may be used to increase average information per bit is
a)
Shannon-Fano algorithm
b)
ASK
c)
FSK
d)
Digital modulation techniques
4.
For a binary symmetric channel, the random bits are given as
a)
Logic 1 given by probability P and logic 0 by (1-P)
b)
Logic 1 given by probability 1-P and logic 0 by P
c)
Logic 1 given by probability P2 and logic 0 by 1-P
d)
Logic 1 given by probability P and logic 0 by (1-P)2
5.
Information rate is defined as
a)
Information per unit time
b)
Average number of bits of information per second
c)
rH
d)
All of the above
6.
The relation between entropy and mutual information is
a)
I(X;Y) = H(X) - H(X/Y)
b)
I(X;Y) = H(X/Y) - H(Y/X)
c)
I(X;Y) = H(X) - H(Y)
d)
I(X;Y) = H(Y) - H(X)
7.
The memory less source refers to
a)
No previous information
b)
No message storage
c)
Emitted message is independent of previous message
d)
None of the above
8.
Synchronization of signals is done using
a)
Pilot clock
b)
Extracting timing information from the received signal
c)
Transmitter and receiver connected to master timing source
d)
All of the above
9.
QPSK is a modulation scheme where each symbol consists of
a)
4 bits
b)
2 bits
c)
1 bits
d)
M number of bits, depending upon the requirement
10.
The binary waveform used to generate BPSK signal is encoded in
a)
Bipolar NRZ format
b)
Manchester coding
c)
Differential coding
d)
None of the above
11.
In On-Off keying, the carrier signal is transmitted with signal value '1' and '0' indicates
a)
No carrier
b)
Half the carrier amplitude
c)
Amplitude of modulating signal
d)
None of the above
12.
ASK modulated signal has the bandwidth
a)
Same as the bandwidth of baseband signal
b)
Half the bandwidth of baseband signal
c)
Double the bandwidth of baseband signal
d)
None of the above
13.
The transmission bandwidth of the raised cosine spectrum is given by
a)
Bt = 2w(1 + α)
b)
Bt = w(1 + α)
c)
Bt = 2w(1 + 2α)
d)
Bt = 2w(2 + α)
14.
Zero forced equalizers are used for
a)
Reducing ISI to zero
b)
Sampling
c)
Quantization
d)
None of the above
15.
Equalization in digital communication
a)
Reduces inter symbol interference
b)
Removes distortion caused due to channel
c)
Is done using linear filters
d)
All of the above
16.
Roll - off factor is defined as
a)
The bandwidth occupied beyond the Nyquist Bandwidth of the filter
b)
The performance of the filter or device
c)
Aliasing effect
d)
None of the above
17.
The filter used for pulse shaping is
a)
Raised - cosine filter
b)
Sinc shaped filter
c)
Gaussian filter
d)
All of the above
18.
The criterion used for pulse shaping to avoid ISI is
a)
Nyquist criterion
b)
Quantization
c)
Sample and hold
d)
PLL
19.
Matched filters are used
a)
For maximizing signal to noise ratio
b)
For signal detection
c)
In radar
d)
All of the above
20.
The time interval over which the received signal may be sampled without error may be explained by
a)
Width of eye opening of eye pattern
b)
Rate of closure of eye of eye pattern
c)
Height of the eye opening of eye pattern
d)
All of the above
21.
Eye pattern is
a)
Is used to study ISI
b)
May be seen on CRO
c)
Resembles the shape of human eye
d)
All of the above
22.
Alternate Mark Inversion (AMI) is also known as
a)
Pseudo ternary coding
b)
Polar NRZ format
c)
Noise immunity
d)
None of the above
23.
The advantage of using Manchester format of coding is
a)
Power saving
b)
Polarity sense at the receiver
c)
Noise immunity
d)
None of the above
24.
The maximum synchronizing capability in coding techniques is present in
a)
Manchester format
b)
Polar NRZ
c)
Polar RZ
d)
Polar quaternary NRZ
25.
In a uni-polar RZ format
a)
The waveform has zero value for symbol '0'
b)
The waveform has A volts for symbol '1'
c)
The waveform has positive and negative values for '1' and '0' symbol respectively
d)
Both a and b are correct
26.
In polar RZ format for coding, symbol '0' is represented by
a)
Zero voltage
b)
Negative voltage
c)
Pulse is transmitted for half the duration
d)
Both b and c are correct
27.
Scrambling of data is
a)
Removing long strings of 1's and 0's
b)
Exchanging of data
c)
Transmission of digital data
d)
All of the above
28.
Regenerative repeaters are used for
a)
Eliminating noise
b)
Reconstruction of signals
c)
Transmission over long distances
d)
All of the above
29.
For a (7, 4) block code, 7 is the total number of bits and 4 is the number of
a)
Information bits
b)
Redundant bits
c)
Total bits- information bits
d)
None of the above
30.
For M equally likely messages, the average amount of information H is
a)
H = log10M
b)
H = log2M
c)
H = log10M2
d)
H = 2log10M
31.
The capacity of a binary symmetric channel, given H(P) is binary entropy function is
a)
1 - H(P)
b)
H(P) - 1
c)
1 - H(P)2
d)
H(P)2 - 1
32.
The channel capacity according to Shannon's equation is
a)
Maximum error free communication
b)
Defined for optimum system
c)
Information transmitted
d)
All of the above
33.
Probability density function defines
a)
Amplitudes of random noise
b)
Density of signal
c)
Probability of error
d)
All of the above
34.
In DPSK technique, the technique used to encode bits is
a)
AMI
b)
Differential code
c)
Uni polar RZ format
d)
Manchester format
35.
In coherent detection of signals,
a)
Local carrier is generated
b)
Carrier of frequency and phase as same as transmitted carrier is generated
c)
The carrier is in synchronization with modulated carrier
d)
All of the above
36.
QPSK system uses a phase shift of
a)
Π
b)
Π/2
c)
Π/4
d)
2Π
37.
Calculate entropy for the given 1/2,1/4,1/4
a)
1.8 bits/symbol
b)
1.5 bits/symbol
c)
2 bits/symbol
d)
2.5 bits/symbol
38.
If the bandwidth is infinite then the channel
a)
s/no
b)
1.44s/no
c)
s/1.44so
d)
1.44no/s
39.
The maximum value of quantization error
a)
delta/2
b)
delta
c)
delta/3
d)
delta/4
40.
The code rate of convolutional encoder
a)
n/k
b)
k/n
c)
k/2n
d)
mn
41.
The sequence of operations in which PCM is done is
a)
Sampling, quantizing, encoding
b)
Quantizing, encoding, sampling
c)
Quantizing, encoding, sampling
d)
None of the above
42.
In Delta modulation,
a)
One bit per sample is transmitted
b)
All the coded bits used for sampling are transmitted
c)
The step size is fixed
d)
Both a and c are correct
43.
In Differential Pulse Code Modulation techniques, the decoding is performed by
a)
Accumulator
b)
Sampler
c)
PLL
d)
Quantizer
44.
For a line code, the transmission bandwidth must be
a)
Maximum possible
b)
As small as possible
c)
Depends on the signal
d)
None of the above
45.
The information rate R for given average information H= 2.0 for analog signal band limited to B Hz is
a)
8 B bits/sec
b)
4 B bits/sec
c)
2 B bits/sec
d)
16 B bits/sec
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