Generic selectors
Exact matches only
Search in title
Search in content
Search in posts
Search in pages
Filter by Categories
nmims post
Objective Type Set
Online MCQ Assignment
Question Solution
Solved Question
Uncategorized

## Communications MCQ Set 1

1. In M-ary FSK, as M increases error
a) Increases
b) Decreases
c) Does not get effected
d) Cannot be determined

Answer: b [Reason:] In M-ary FSK as M increases error decreases.

2. In M-ary FSK as M tends to infinity, probability of error tends to
a) Infinity
b) Unity
c) Zero
d) None of the mentioned

Answer: c [Reason:] In M-ary FSK as M tends to infinity, probability of error becomes zero.

3. For non coherent reception of PSK _____ is used.
a) Differential encoding
b) Decoding
c) Differential encoding & Decoding
d) None of the mentioned

Answer: c [Reason:] For non coherent reception of PSK, differential encoding is used at the transmitter and decoding is used at the receiver.

4. Which modulation technique have the same bit and symbol error probability?
a) BPSK
b) DPSK
c) OOK
d) All of the mentioned

Answer: d [Reason:] BPSK, DPSK, OOK and non coherent FSK have same bit and symbol error probability.

5. An amplifier uses ______ to take input signal.
a) DC power
b) AC power
c) DC & AC power
d) None of the mentioned

Answer: a [Reason:] An amplifier uses DC power to take an input signal and increase its amplitude at the output.

6. Which has 50% maximum power efficiency?
a) Class A
b) Class B
c) Class AB
d) None of the mentioned

Answer: a [Reason:] Class A amplifiers have 50% maximum power efficiency.

7. Which generates high distortion?
a) Class A
b) Class B
c) Class C
d) Class AB

Answer: c [Reason:] Class C amplifiers generates high distortion and it is closer to switch than an amplifier.

8. Class B linear amplifiers have maximum power efficiency of
a) 50%
b) 75%
c) 78.5%
d) None of the mentioned

Answer: c [Reason:] Class B linear amplifiers have maximum power efficiency of 78.5%.

9. Which has the maximum power efficiency?
a) Class A
b) Class B
c) Class C
d) Class AB

Answer: c [Reason:] Class C has the maximum power efficiency when compared to the other linear amplifiers.

10. Free space in idealization which consists
a) Transmitter
c) Transmitter & Receiver
d) None of the mentioned

Answer: c [Reason:] Free space is a idealization that consists of only transmitter and receiver.

## Communications MCQ Set 2

1. The limit which represents the threshold Eb/N0 value below which reliable communication cannot be maintained is called as
a) Probability limit
b) Error limit
c) Shannon limit
d) Communication limit

Answer: c [Reason:] Eb/N0 curve has waterfall shape. Shannon limit gives the threshold value below which reliable communication cannot be maintained.

2. M-ary signalling produces _______ error performance with orthogonal signalling and _______ error performance with multiple phase signalling.
c) Improved, improved

Answer: b [Reason:] In M-ary signalling as k increases, the curve moves towards the degraded error performance. It produces improved error performance in case of orthogonal signalling and degraded error performance in case of multiple phase signalling.

3. Which is more vulnerable to noise?
a) 2-ary system
b) 4-ary system
c) Binary system
d) None of the mentioned

Answer: b [Reason:] The minimum energy noise vector for 4-ary system is smaller than 2-ary system. So 4-ary system is more vulnerable to noise.

4. In which system, bit stream is portioned into even and odd stream?
a) BPSK
b) MSK
c) QPSK
d) FSK

Answer: c [Reason:] In QPSK bit stream is portioned into even and odd stream, I and Q bit streams. Each new stream modulates as orthogonal component at half bit rate.

5. The error performance of MPSK ______ as M or k increases.
a) Increases
b) Decreases
c) Stays constant
d) None of the mentioned

Answer: b [Reason:] The error performance of MPSK degrades as M or k increases.

6. In MPSK adding new signals _______ make it vulnerable to noise and in MFSK _______ make it vulnerable.
a) Does , does not
b) Does not, does
c) Does, does
d) Does not, does not

Answer: a [Reason:] In MPSK adding new signals that is on crowding the signals it makes it vulnerable to noise where as in MFSK it does not.

7. In orthogonal signalling with symbols containing more number of bits we need ____ power.
a) More
b) Less
c) Double
d) None of the mentioned

Answer: a [Reason:] In orthogonal signalling with symbols having more number of bits need more power but requirement per bit is reduced.

8. For FSK signalling , WT is equal to
a) 0
b) 1
c) 0.737
d) Infinity

Answer: b [Reason:] For FSK signalling the detection bandwidth is typically equal to symbol rate 1/T that is WT is nearly equal to 1.

9. Energy per symbol Es is given as
a) Es=Eb(log2M)
b) Es=Eb/(log2M)
c) Es=2Eb(log2M)
d) Es=Eb/2(log2M)

Answer: a [Reason:] In M-ary PSK signalling, the energy per symbol is given as Es=Eb(log2M).

10. The relation between probability of bit error and probability of symbol error in M-ary orthogonal signalling is
a) M/M-1
b) 2M/M-1
c) (M/2)/M-1
d) M/M+1

Answer: c [Reason:] The relationship between the probability of bit error and probability of symbol error is (M/2)/M-1 in M-ary orthogonal signalling.

11. As limit of k increases, the ratio of PB/PE becomes
a) 1:2
b) 2:1
c) 1:3
d) 3:1

Answer: a [Reason:] As the limit of k increases, the ratio of PB/PE becomes 1:2.

## Communications MCQ Set 3

1. What is the source for performance degradation?
a) Thermal noise
b) Man made noise
c) Natural noise
d) All of the mentioned

Answer: d [Reason:] The sources for performance degradation are thermal noise, natural noise and man made noise.

2. The received power is attenuated by a factor called
a) Path loss
b) Free space loss
c) Path & Free space loss
d) None of the mentioned

Answer: c [Reason:] The received power expressed in terms of transmitted power is attenuated by a factor called path loss or free space loss.

3. Scintillation describes the fading caused by
a) Atmospheric changes
b) Physical changes
c) Thermal noise
d) Propagating effects

Answer: b [Reason:] Scintillation is used to describe fading caused by physical changes in the propagating medium.

4. Large scale fading refers the attenuation in
a) Amplitude
b) Phase
c) Signal power
d) None of the mentioned

Answer: c [Reason:] large scale fading refers to signal power attenuation or path loss due to motion in large area.

5. Small scale refers to changes in
a) Amplitude
b) Phase
c) Amplitude & Phase
d) None of the mentioned

Answer: c [Reason:] Small scale fading refers to changes in amplitude and phase as a result of small changes in spatial positioning between transmitter and receiver.

6. Small scale fading manifests due to
a) Signal dispersion
b) Time variant behavior
c) Signal dispersion & Time variant behavior
d) None of the mentioned

Answer: c [Reason:] Small scale fading manifests itself in two mechanisms- time spreading of the signal ( signal dispersion) and time variant behavior of the channel.

7. The parameters used to describe large scale fading are
a) Reference distance
b) Path loss exponent
c) Standard deviation of random variable
d) All of the mentioned

Answer: d [Reason:] The parameters used to statistically describe path loss due to large scale fading are reference distance, path loss exponent and standard deviation of random variable.

8. Small scale fading occurs due to
a) Doppler shift
b) Time delay
c) Doppler shift & Time delay
d) None of the mentioned

Answer: c [Reason:] Small scale fading occurs due to time delay and frequency or Doppler shift.

9. What are the types of small scale fading that occurs due to Doppler shift?
c) Slow & Fast fading
d) None of the mentioned

Answer: c [Reason:] Slow fading and fast fading occurs due to Doppler or frequency shift.

## Communications MCQ Set 4

1. PCM includes the process of
a) Amplitude discretization
b) Time discretization
c) Amplitude & Time discretization
d) None of the mentioned

Answer: c [Reason:] Time discretization and amplitude discretization are the two processes done in PCM system.

2. For which quantization process is used?
a) Amplitude discretization
b) Time discretization
c) Amplitude & Time discretization
d) None of the mentioned

Answer: a [Reason:] Sampling process is used for time discretization and quantization process is used for amplitude discretization.

3. Modulation process corresponds to ______ the amplitude, frequency or phase.
a) Switching
b) Keying
c) Any of the mentioned
d) None of the mentioned

Answer: c [Reason:] Modulation process corresponds to switching or keying the amplitude, frequency or phase of CW carrier.

4. Matched filter
a) Is a non linear filter
b) Produces maximum output SNR
c) Both of the mentioned
d) None of the mentioned

Answer: b [Reason:] Matched filter is a linear filter which produces maximum output SNR for a given transmitted signal.

5. Which has same probability of error?
a) ASK and FSK
b) ASK and PSK
c) PSK and FSK
d) None of the mentioned

Answer: c [Reason:] Uni-polar base-band signalling, PSK and FSK has same probability of error.

6. Which has higher error probability performance?
a) Uni-polar base-band signalling
b) Bipolar base-band signalling
d) FSK

Answer: b [Reason:] Bipolar base-band signalling has high error probability performance than the others. The probability of error value is A2T.

7. Time division multiplexing uses
a) High pass filter
b) Commutator
c) High pass filter & Commutator
d) None of the mentioned

Answer: b [Reason:] Time division multiplexing uses low pass filter and commutator.

8.In TDM, at the receiver end, ____ filter is used.
a) Low pass
b) High pass
c) Band pass
d) Band stop

Answer: a [Reason:] In TDM, at the receiver end low pass filtering is done to obtain individual signals.

9. Which provides more secure communication?
a) CDMA
b) FDMA
c) TDMA
d) None of the mentioned

Answer: a [Reason:] CDMA provides more secure communication than TDMA and FDMA.

10. Entropy is the measure of
a) Randomness
b) Information
c) Randomness & Information
d) None of the mentioned

Answer: c [Reason:] Entropy can be defined as the measure of randomness or information.

11. Entropy calculation returns
a) Random variable
b) Deterministic number
c) Random number
d) None of the mentioned

Answer: b [Reason:] Entropy calculation returns a deterministic number and not a random variable.

12.Entropy of N random variables is the _____ of the entropy of individual random variable.
a) Sum
b) Product
c) Sum of squares
d) Average

Answer: a [Reason:] Entropy of N random variables is the sum of the entropy of individual random variable.

## Communications MCQ Set 5

1. Properties used to determine stream’s fidelity
a) Sampling rate
b) Bit depth
c) Sampling rate & Bit depth
d) None of the mentioned

Answer: c [Reason:] Two basic properties to determine stream’s fidelity are bit depth and sampling rate, number of times per second that samples are taken.

2. In bipolar codes, pulses can be
a) Positive
b) Negative
c) Absent
d) All of the mentioned

Answer: d [Reason:] In bipolar codes, the pulses can be positive, negative or absent.

3. Delta modulation is ______ conversion.
a) Analog to digital
b) Digital to analog
c) Both of the mentioned
d) None of the mentioned

Answer: c [Reason:] Delta modulation is the process of analog to digital and digital to analog conversion technique used for transmission of voice signals.

4. To achieve high signal to noise ratio, delta modulation must use
a) Under sampling
b) Over sampling
c) Aliasing
d) None of the mentioned

Answer: b [Reason:] To achieve high signal to noise ratio, delta modulation must use over sampling techniques.

5. The demodulator in delta modulation technique is
a) Differentiator
b) Integrator
c) Quantizer
d) None of the mentioned

Answer: b [Reason:] The demodulator used in delta modulation is a simple form of integrator.

6. Source of noise in delta modulation is
a) Granularity
c) Granularity & Slope overload
d) None of the mentioned

Answer: c [Reason:] Sources of noise in delta modulation are granularity and slope overload.

7. When probability of receiving a symbol is 1 then how much information will be obtained?
a) Little information
b) Much information
c) No information
d) None of the mentioned

Answer: c [Reason:] When the probability of receiving a symbol is 1 then the information obtained is zero.

8. In channel encoding procedure
a) Redundancy bits are added
b) Error are corrected
c) Both of the mentioned
d) None of the mentioned

Answer: c [Reason:] In channel encoding includes addition of redundancy to the signal such that any bit errors can be corrected.

9. Modulation process includes
a) Analog to digital conversion
b) Digital to analog conversion
c) Both of the mentioned
d) None of the mentioned

Answer: b [Reason:] Modulation procedure includes digital to analog conversion which produces a continuous time signal that can be sent through the channel.

10. Switching exists in
a) Point to point communication
c) Both of the mentioned
d) None of the mentioned

Answer: a [Reason:] Circuit connection in point to point communication is called as switching. Switching does not exist in broadcast communication or network.

11. Space division has dedicated
a) Paths
b) Time slots
c) Paths & Time slots
d) None of the mentioned

Answer: a [Reason:] Space division has dedicated paths and time division has dedicated time slots.

12. In time division system, the actual switch is called as
a) Speech memory
b) Cross point
c) Connecting point
d) None of the mentioned

Answer: a [Reason:] In time division, actual switch is called as speech memory and in space division actual switch is called as cross point.

13. In time division, connection is established using
a) Data exchange
b) Galvanic connection
c) Data exchange & Galvanic connection
d) None of the mentioned

Answer: a [Reason:] In time division, connection is established using data exchange and in space division it is established using galvanic connections.

14. Analogue switches provides
a) Good bandwidth
b) Low distortion
c) Low cost
d) All of the mentioned