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Communications MCQ Set 1

1. What is the full form of LF?
a) Line Feed
b) Link Feed
c) Line Forward
d) Link Forward

View Answer

Answer: a [Reason:] Line feed means moving one line forward. It is basically a control character, coded upto 10 decimal places.

2. In synchronous transmission, frames are about the same length as in asynchronous transmission.
a) True
b) False

View Answer

Answer: b [Reason:] In synchronous transmission both sender and receiver access the data according to same clock. It has no start and stop bits and thus it has more efficient. In synchronous transmission, frames are much longer than the frames in asynchronous transmission.

3. What is the full form of UART?
a) Universal Asynchronous Receiver Transmitter
b) Universal Automatic Receiver Transmitter
c) Unaltered Asynchronous Receiver Transmitter
d) Unaltered Automatic Receiver Transmitter

View Answer

Answer: a [Reason:] UART is a computer hardware device. It is mainly used for asynchronous serial communication. It is used in modules like Bluetooth etc. It stands for Universal Asynchronous Receiver Transmitter.

4. AM spectrum consists of ________
a) Carrier frequency
b) Upper sideband
c) Lower sideband
d) Carrier frequency with both upper and lower sideband

View Answer

Answer: d [Reason:] Spectrum of AM wave consists of a carrier with two sidebands. It is found that if carrier frequency is 5KHz then the two sidebands produced by it is 5KHz away from the carrier.

5. To maintain synchronization in synchronous transmission, __________
a) long strings of 1s and 0s must not be allowed
b) transmission must stop periodically
c) clock circuits must be precisely adjusted
d) channel must be noise free

View Answer

Answer: a [Reason:] In synchronous transmission both sender and receiver access the data according to same clock. It has no start and stop bits and thus it has more efficient. To maintain synchronization long strings of 1s and 0s are not allowed.

6. CRC stands for __________
a) Cyclic Redundancy Check
b) Cyclic Repeat Check
c) Cyclic Redundancy Character
d) Cyclic Redundancy Character

View Answer

Answer: a [Reason:] CRC is an error detecting code. It is generally used in digital network. It was invented by W. Wesley Peterson. CRC stands for Cyclic Redundancy Check.

7. What do you understand by the term Internet?
a) a network of networks
b) a very large client-server network
c) a very large CSMA/CD network
d) not a network

View Answer

Answer: a [Reason:] Internet is a global network providing us a variety of information. It is a network of networks that consists of public, private, business, and government networks of local to global scope.

8. Which statement is correct about circuit-switched network?
a) each channel can carry only one data stream
b) usually uses a bus topology
c) usually uses a star topology
d) communication is half-duplex

View Answer

Answer: a [Reason:] In circuit switching a circuit is applied for the duration of transmission. Its example is telephone. In it each channel can carry only one data stream.

9. When two or more PCs try to access a baseband network cable at the same time, it is called ________
a) contention
b) collision
c) excess traffic
d) multiple access

View Answer

Answer: a [Reason:] Contention is a term of networks, used when two or more PCs try to access a baseband network cable at the same time.

10. When two PCs send data over a baseband network cable at the same time, it is called ________
a) contention
b) collision
c) excess traffic
d) multiple access

View Answer

Answer: b [Reason:] Collision is a term of networks, used when two PCs send data over a baseband network cable at the same time.

Communications MCQ Set 2

1. Which of the following is not a standard used for paging system?
a) POCSAG
b) ERMES
c) IS-95
d) FLEX

View Answer

Answer: c [Reason:] IS-95 is a standard used for cellular system which is based on code division multiple access (CDMA). POCSAG (Post Office Code Standard Advisory Group), ERMES (European Radio Messaging System) and FLEX are the protocols used in paging system.

2. Paging system uses which mode of transmission?
a) Full duplex
b) Simplex
c) Half Duplex
d) Duplex

View Answer

Answer: b [Reason:] Simplex systems communicate in only one way. For the paging systems, messages received are not acknowledged and thus they use simplex mode of transmission.

3. The information sent by paging system is known as a:
a) Note
b) Line
c) Message
d) Page

View Answer

Answer: d [Reason:] Page is concise information sent by a paging system to the subscribers of entire service area.

4. Which type of message cannot be sent with the help of paging system?
a) Alphanumeric message
b) Video message
c) Voice message
d) Numeric message

View Answer

Answer: b [Reason:] The message sent by a paging system can be numeric, alphanumeric or voice depending upon the type of service.

5. What is a paging access number?
a) An e mail id
b) A username
c) A toll free telephone number
d) A registration number

View Answer

Answer: c [Reason:] Paging access number is a telephone number which is used to send the information to the subscriber.

6. Which type of transmission technique is employed by paging system?
a) Simulcasting
b) Multicasting
c) Unicasting
d) Hybrid

View Answer

Answer: a [Reason:] Simulcast is a reliable technique used by paging system by transmitting the same paging signal from multiple paging transmitters at approximately equal times.

7. Which of the following is not the property of paging system?
a) Asymmetric communication
b) Light weight
c) High cost
d) Wide area coverage

View Answer

Answer: c [Reason:] One of the main reasons for the increased users of paging system was its less cost. But as the prices of cellular system declined, the users of paging system also decreased.

8. Which of the following properties describes the transmitters and receivers in paging system?
a) High complexity and high power transmitter, high complexity and high power receivers
b) Low complexity and low power transmitter, low complexity and low power receivers
c) Low complexity and low power transmitter, high complexity and high power receivers
d) High complexity and high power transmitter, low complexity and low power receivers

View Answer

Answer: d [Reason:] High power of transmitters helps paging signal to easily penetrate the building and low power receivers allow long usage time and light weight batteries.

9. What is a pager in the paging system?
a) A transmitter
b) A receiver
c) A transceiver
d) An equalizer

View Answer

Answer: b [Reason:] A pager is a wireless device which receives the page, i.e. numeric, alphanumeric or voice message sent by the transmitter.

10. Who introduced the paging system for the first time?
a) Al Gross
b) Teri Pall
c) Alexander Graham Bell
d) Martin Cooper

View Answer

Answer: a [Reason:] AL Gross introduced the first paging system during world war in 1949.

Communications MCQ Set 3

1. The term small scale fading describes the slow fluctuations of received power level due to changes in receiver position. State whether True or False.
a) True
b) False

View Answer

Answer: b [Reason:] The term small scale fading describes the rapid fluctuations of received power level due to changes in receiver position. This effect is due to the constructive and destructive interference of the numerous multipath waves that impinge upon a wireless receiver.

2. The rapid fluctuations due to small scale fading affect the _________ design.
a) Receiver
b) Transmitter
c) MSC
d) Base station

View Answer

Answer: a [Reason:] The rapid fluctuation due to small scale fading affect every aspect of receiver design such as dynamic range, equalization, diversity, modulation scheme and channel error correction coding. These fluctuations are a function of direction of travel as related to the angle of arrival of multipath delay.

3. An approximately omnidirectional channel model accurately describes fading statistics if directional antennas are employed at the receiver. State whether True or False.
a) True
b) False

View Answer

Answer: b [Reason:] An approximately omnidirectional channel model accurately describes fading statistics if directional or smart antenna systems are employed at the receiver. Unfortunately, recent measurements and models have shown that the arriving multipath in a local area bears little resemblance to the omnidirectional propagation.

4. Which of the following is not a principle shape factor?
a) Angular spread
b) Angular constriction
c) Azimuthal direction of maximum fading
d) Angle of arrival

View Answer

Answer: d [Reason:] Three principle shape factors are angular spread, angular constriction, and azimuthal direction of maximum fading. They are exactly related to the average rate at which a received signal fades.

5. Angular spread is a measure of how multipath concentrates about ___________.
a) Angle of arrival
b) Transmitted power
c) Single azimuthal direction of arrival
d) Received power

View Answer

Answer: c [Reason:] The shape factor, angular spread is a measure of how multipath concentrates about a single azimuthal direction of arrival. It has several advantages like it is invariant under changes in transmitted power.

6. Angular constriction is a measure of how multipath concentrates about ______ azimuthal direction.
a) Single
b) Two
c) Three
d) Four

View Answer

Answer: b [Reason:] The shape factor, angular constriction is a measure of how multipath concentrates about two azimuthal directions. The measure for angular constriction is invariant under changes in transmitted power.

7. Shape factor, azimuthal direction of maximum fading is a directional parameter. State whether True or False.
a) True
b) False

View Answer

Answer: a [Reason:] Azimuthal direction of maximum fading is the third shape factor which is a directional or orientation parameter. Its value corresponds to the direction in which s mobile user would move in order to experience the maximum fading rate in the local area.

8. _______of a stationary process is actually the variance of the rate of change.
a) Mean
b) Mean square
c) Mean squared derivative
d) Mean squared integral

View Answer

Answer: c [Reason:] Mean squared derivative of a stationary process is actually the variance of the rate of change. The mean derivative of the stationary process is zero; the mean squared derivative is the simplest statistics that measures the fading rate of a channel.

9. Complex received voltage is a summation of __________ that have impinged upon receiver antenna.
a) Multipath waves
b) Waves
c) Power density
d) Single path waves

View Answer

Answer: a [Reason:] Complex received voltage is a baseband representation. It us a summation of numerous multipath waves that have impinged upon the receiver antenna and have excited a complex voltage component at the input of a receiver.

10. Which of the following is equal to received power?
a) Square of complex voltage
b) Complex voltage
c) Magnitude of complex voltage
d) Magnitude squared of complex voltage

View Answer

Answer: d [Reason:] The received power is equal to the magnitude squared of complex voltage. The mathematical operation of taking the squared magnitude of a complex quantity is a nonlinear operation.

11. Which of the following is equal to received envelope?
a) Square of complex voltage
b) Complex voltage
c) Magnitude of complex voltage
d) Magnitude squared of complex voltage

View Answer

Answer: c [Reason:] The received envelope is equal to the magnitude of the complex voltage. The channel is assumed to be Rayleigh fading in order to calculate the mean squared fading rate.

12. Which of the following describes the average fading rate within a local area?
a) Angular spread
b) Angular constriction
c) Azimuthal direction of maximum fading
d) Angle of arrival

View Answer

Answer: a [Reason:] Angular spread describes the average fading rate within a local area. The average of the two fading rate variances, regardless of the orientation of the measurement, is always given by averaging the variances observed over two perpendicular directions within the local area.

13. Angular constriction affects the average fading rate within local area. State whether True or False.
a) True
b) False

View Answer

Answer: b [Reason:] Angular constriction does not affect the average fading rate within local area. It describes the variability of fading rates taken along different azimuthal directions.

Communications MCQ Set 4

1. Small scale fading describes the _____ fluctuations of the amplitude, phases of signal.
a) Rapid
b) Slow
c) Instantaneous
d) Different

View Answer

Answer: a [Reason:] Small scale fading or simply fading, is used to describe the rapid fluctuations of amplitudes, phases, or multipath delays of a radio signal over a short period of time or travel distance. It ignores the large scale path loss.

2. Fading is caused by interference.(True/False)
a) True
b) False

View Answer

Answer: a [Reason:] Fading is caused by interference. It is caused by interference between two or more versions of the transmitted signal which arrive at the receiver at slightly different times.

3. Which of the following is not an effect caused by multipath in radio channel?
a) Rapid changes in signal strength
b) Random frequency modulation
c) Power of base station
d) Time dispersion

View Answer

Answer: c [Reason:] Rapid changes in signal strength over a small travel distance are caused due to multipath. It causes random frequency modulation due to varying Doppler shifts on different multipath signals. Time dispersion is also caused by multipath propagation delays.

4. In urban areas, fading occurs due to height of mobile antenna ________ than height of surrounding structure.
a) Same
b) Smaller
c) Greater
d) Very larger

View Answer

Answer: b [Reason:] In urban areas, fading occurs because height of the mobile antenna is below the height of surrounding structures. Therefore, there is no single line of sight path to the base station.

5. Fading does not occur when mobile receiver is stationary. State whether True or False.
a) True
b) False

View Answer

Answer: b [Reason:] The received signal may fade even when the mobile receiver is stationary. It is due to the movement of surrounding objects in the radio channel. The multipath components combine vectorially at the receiver antenna and cause signal to distort or fade.

6. Apparent shift in frequency in multipath wave is caused due to relative motion between________
a) Base station and MSC
b) Mobile and surrounding objects
c) Mobile and MSC
d) Mobile and base station

View Answer

Answer: d [Reason:] Due to relative motion between mobile and base station, each multipath wave experiences an apparent shift in frequency. This shift in received signal frequency due to motion called Doppler shift.

7. Doppler shift is directly proportional to __________
a) Velocity
b) Height of antenna
c) Power of receiving antenna
d) Power of transmitter

View Answer

Answer: a [Reason:] The shift in received signal frequency due to motion is called Doppler shift. It is directly proportional to the velocity and direction of motion of mobile with respect to the direction of arrival of the received multipath wave.

8. Which of the following factor does not influence small scale fading?
a) Multipath propagation
b) Power density of base station
c) Speed of mobile
d) Speed of surrounding objects

View Answer

Answer: b [Reason:] Many physical factors in radio channel influence small scale fading. Multipath propagation, speed of mobile, speed of surrounding objects, transmission bandwidth of the signal influences small scale fading in a large way.

9. Signal will distort if transmitted signal bandwidth is greater than bandwidth of __________
a) Receiver
b) Radio channel
c) Multipath channel
d) Transceiver

View Answer

Answer: c [Reason:] Received signal will be distorted if transmitted signal bandwidth is greater than bandwidth of multipath channel. But received signal strength will not fade much over a local area.

10. What is a measure of the maximum frequency difference for which signals are strongly correlated in amplitude?
a) Coherence bandwidth
b) Narrow bandwidth
c) Incoherent bandwidth
d) Wide bandwidth

View Answer

Answer: a [Reason:] The bandwidth of the channel can be quantified by the coherence bandwidth. It is related to the specific multipath structure of channel. It is a measure of maximum frequency difference for which signals are strongly correlated in amplitude.

11. The Doppler shift for mobile moving with constant velocity, v is given by _______
a) (v*cos θ)/λ
b) v/λ
c) v*cos θ
d) v*λ

View Answer

Answer: a [Reason:] Doppler shift is given by (v*cos θ)/λ. This formula relates the Doppler shift to the mobile velocity and spatial angle between the direction of motion of mobile and the direction of arrival of the wave.

12. Doppler shift is positive if mobile is moving away from direction of arrival of the wave. State whether True or False.
a) True
b) False

View Answer

Answer: b [Reason:] Doppler shift is positive if the mobile is mobile is moving toward the direction of arrivl of the wave, as the apparent received frequency is increased. And if the mobile is moving away from direction of arrival of the wave, Doppler shift is negative.

Communications MCQ Set 5

1. Which of the following multiple access techniques are used by second generation cellular systems?
a) FDMA/FDD and TDMA/FDD
b) TDMA/FDD and CDMA/FDD
c) FDMA/FDD and CDMA/FDD
d) FDMA/FDD only

View Answer

Answer: b [Reason:] First generation cellular system used FDMA/FDD techniques. Second generation standards uses TDMA/FDD and CDMA/FDD multiple access techniques. 2G networks are digital.

2. Which one is not a TDMA standard of second generation networks?
a) GSM
b) IS-136
c) AMPS
d) PDC

View Answer

Answer: c [Reason:] GSM (Global System Mobile), IS-136 (Interim Standard 136) and PDC (Pacific Digital Cellular) are the three most popular TDMA standards of second generation. AMPS is a first generation standard.

3. Which of the following is a CDMA standard of second generation network?
a) IS-95
b) IS-136
c) ETACS
d) EDGE

View Answer

Answer: a [Reason:] Interim Standard 95 (IS-95) is the most popular CDMA standard of second generation networks. IS-136 is a TDMA standard of 2G. EDGE is a standard of 2.5G and ETACS is a 1G standard.

4. Popular 2G CDMA standard IS-95 is also known as ______
a) CdmaOne
b) CdmaTwo
c) IS-136
d) IS-95B

View Answer

Answer: a [Reason:] The popular 2G CDMA standard, Interim Standard (IS-95) is also known as CdmaOne. The 2.5G CDMA standard, IS-95B is called CdmaTwo. And IS-136 is a TDMA standard for 2G.

5. How many users or voice channels are supported for each 200 KHz channel in GSM?
a) Eight
b) Three
c) Sixty four
d) Twelve

View Answer

Answer: a [Reason:] GSM is a circuit switched system that divides each 200 KHz channel into eight 25 KHz time slots, i.e. each radio channel is divided into eight voice channels.

6. How many voice channels are supported for each 30 KHz radio channel in IS-136?
a) Eight
b) Thirty
c) Three
d) Sixteen

View Answer

Answer: c [Reason:] Interim Standard 136 (IS-136) was popularly known as North American Digital Cellular (NADC) system. It divides each 30 KHz radio channel into three time slots, each of 10 KHz.

7. How many users are supported in IS-95 for each 1.25 MHz?
a) Eight
b) Sixty four
c) Sixteen
d) Twenty five

View Answer

Answer: b [Reason:] IS-95 supports upto 64 users which are orthogonally coded and simultaneously transmitted on each 1.25 MHz. The services of IS-95 standard are short messaging service, slotted paging, over-the-air activation, enhanced mobile station identities etc.

8. Which modulation technique is used by GSM?
a) GMSK
b) BPSK
c) QPSK
d) GFSK

View Answer

Answer: a [Reason:] GSM uses a form of modulation known as GMSK (Gaussian Minimum Shift Keying). It is a form of modulation with no phase discontinuities and provides data transmission with efficient spectrum usage.

9: IS-95 uses which modulation technique?
a) GMSK
b) BPSK
c) QAM
d) AFSK

View Answer

Answer: b [Reason:] IS- 95 uses BPSK (Binary Phase Shift Keying) with quadrature spreading. It is regarded as one of the most robust digital modulation technique and is used for long distance wireless communication.

10. IS-136 uses which modulation technique?
a) π/4 DQPSK
b) BPSK
c) GMSK
d) AFSK

View Answer

Answer: a [Reason:] IS-136 uses π/4 DQPSK modulation technique. This technique allows a bit rate of 48.6 Kbit/s with 30 KHz channel spacing which gives a bandwidth efficiency of 1.62 bit/s/Hz.

11. Which is one of the disadvantages of 2G standards?
a) Short Messaging Service (SMS)
b) Digital modulation
c) Limited capacity
d) Limited Internet Browsing

View Answer

Answer: d [Reason:] 2G technologies use circuit switched data modems that limits data users to a single circuit switched voice channel. The advantages of 2G network are that they are digital in nature and supports SMS service.

12. GSM (Global System for Mobile) was earlier also known as _______
a) Group System Mobile
b) Global Special Meaning
c) Group Special Mobile
d) Global Special Mobile

View Answer

Answer: c [Reason:] GSM was earlier known as Group Special Mobile. As it became more global, the meaning of acronym was changed to Global System for Mobile.

13. 2G CDMA standard, IS-95, was proposed by which company?
a) Nippon Telephone and Telegraph (NTT)
b) Qualcomm
c) Bellcore and Motorola
d) AT&T Bell Laboratories

View Answer

Answer: b [Reason:] IS-95 was proposed by Qualcomm in early 1990s. Later it was adopted as a standard by Telecommunications Industry Association in TIA/EIA/IS-95 release published in 1995.

14. Which one of the following 2G standard is used in Japan?
a) IS-136
b) GSM
c) PDC
d) AMPS

View Answer

Answer: c [Reason:] PDC (Personal Digital Cellular) was standardized by Japanese Ministry of Posts and Telecommunication in 1991. It is similar to IS- 136, but with 25 KHz voice channels to be compatible with the Japanese analog channels.

15. The 2G GSM technology uses a carrier separation of _______
a) 1.25 MHz
b) 200 KHz
c) 30 KHz
d) 300 KHz

View Answer

Answer: b [Reason:] The Global System for Mobile (GSM) uses a carrier separation of 200 KHz, each channel supporting upto eight users.

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