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180+ Digital Communication Solved MCQs

These multiple-choice questions (MCQs) are designed to enhance your knowledge and understanding in the following areas: Electrical Engineering .

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151.

The non coherent FSK needs Eb/N0 than coherent FSK.

A. 1db more
B. 1db less
C. 3db more
D. 3db less
Answer» A. 1db more
discuss
152.

The DPSK needs Eb/N0 than BPSK.

A. 1db more
B. 1db less
C. 3db more
D. 3db less
Answer» A. 1db more
discuss
153.

Which is easier to implement and is preferred?

A. coherent system
B. non coherent system
C. coherent & non coherent system
D. none of the mentioned
Answer» B. non coherent system
discuss
154.

Which is the main system consideration?

A. probability of error
B. system complexity
C. random fading channel
D. all of the mentioned
Answer» D. all of the mentioned
discuss
155.

In the frequency of the carrier signal is varied based on the information in an a digital signal

A. ask
B. psk
C. fsk
D. qam
Answer» C. fsk
discuss
156.

In the amplitude of the carrier signal is varied based on the information in an a digital signal

A. ask
B. psk
C. fsk
D. qam
Answer» A. ask
discuss
157.

In modulation , the bit rate is 8 times the baud rate

A. 8-qam
B. 64-qam
C. 256-qam
D. none of above
Answer» C. 256-qam
discuss
158.

In modulation , the baud rate is 1/4 times the bit rate

A. 4-qam
B. 2-psk
C. 4-psk
D. none of above
Answer» D. none of above
discuss
159.

Which of the following is not a characteristic of PN sequence?

A. balance property
B. autocorrelation property
C. run property
D. non deterministic
Answer» D. non deterministic
discuss
160.

           symbols.

A. 2m
B. m
C. 2m
D. 2m-1
Answer» D. 2m-1
discuss
161.

PN sequence can be generated using .

A. sequential logic circuits
B. op-amp
C. timer ic
D. mosfet
Answer» A. sequential logic circuits
discuss
162.

DSSS system spreads the baseband signal by the baseband pulses with a pseudo noise sequence.

A. adding
B. subtracting
C. multiplying
D. dividing
Answer» C. multiplying
discuss
163.

Frequency hopping involves a periodic change of transmission                

A. signal
B. frequency
C. phase
D. amplitude
Answer» B. frequency
discuss
164.

What is the set of possible carrier frequencies in FH-SS?

A. hopset
B. hop
C. chips
D. symbols
Answer» A. hopset
discuss
165.

The bandwidth of the channel used in the hopset is called                    

A. hopping bandwidth
B. total hopping bandwidth
C. instantaneous bandwidth
D. 3 db bandwidth
Answer» C. instantaneous bandwidth
discuss
166.

The processing gain of FH systems is given by ratio of                

A. hopping bandwidth and hopping period
B. instantaneous bandwidth and hopping duration
C. 3 db bandwidth and bit rate
D. total hopping bandwidth and instantaneous bandwidth
Answer» D. total hopping bandwidth and instantaneous bandwidth
discuss
167.

Pseudorandom signal predicted.

A. can be
B. cannot be
C. maybe
D. none of the mentioned
Answer» A. can be
discuss
168.

In FH-SS which of the following Modulation Demodulation Technique has been used

A. bpsk
B. fsk
C. ask
D. qam
Answer» B. fsk
discuss
169.

In DS-SS which of the following Modulation Demodulation Technique has been used

A. bpsk
B. fsk
C. ask
D. qam
Answer» A. bpsk
discuss
170.

Frequency division multiple access (FDMA) assigns channels to users.

A. individual, individual
B. many, individual
C. individual, many
D. many, many
Answer» A. individual, individual
discuss
171.

The FDMA channel carries phone circuit at a time.

A. ten
B. two
C. one
D. several
Answer» C. one
discuss
172.

The bandwidth of FDMA channel is              

A. wide
B. narrow
C. large
D. zero
Answer» B. narrow
discuss
173.

The symbol time in FDMA systems is thus intersymbol interference is

A. large, high
B. small, low
C. small, high
D. large, low
Answer» D. large, low
discuss
174.

Due to transmission scheme bits are needed for overhead in FDMA systems.

A. continuous, few
B. discontinuous, few
C. continuous, many
D. discontinuous, many
Answer» A. continuous, few
discuss
175.

                     is based on FDMA/FDD.

A. gsm
B. w-cdma
C. cordless telephone
D. amps
Answer» D. amps
discuss
176.

Which of the following is not true for TDMA?

A. single carrier frequency for single user
B. discontinuous data transmission
C. no requirement of duplexers
D. high transmission rates
Answer» A. single carrier frequency for single user
discuss
177.

Because of transmissions in TDMA, the handoff process in                      

A. continuous, complex
B. continuous, simple
C. discontinuous, complex
D. discontinuous, simple
Answer» D. discontinuous, simple
discuss
178.

                   synchronization overhead is required in TDMA due to                 transmission.

A. high, burst
B. high, continuous
C. low, burst
D. no, burst
Answer» A. high, burst
discuss
179.

                     of TDMA system is a measure of the percentage of transmitted data that contains information as opposed to providing overhead for the access scheme.

A. efficiency
B. figure of merit
C. signal to noise ratio
D. mean
Answer» A. efficiency
discuss
180.

A TDMA system uses 25 MHz for the forward link, which is broken into radio channels of 200 kHz. If 8 speech channels are supported on a single radio channel, how many simultaneous users can be accommodated?

A. 25
B. 200
C. 1600
D. 1000
Answer» D. 1000
discuss
181.

US digital cellular system based on CDMA was standardized as                  

A. is-54
B. is-136
C. is-95
D. is-76
Answer» C. is-95
discuss
182.

Which of the following technique used in CDMA

A. qam
B. gmsk
C. ds-ss bpsk
D. fh-ss fsk
Answer» C. ds-ss bpsk
discuss

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