Communication Engineering Set 13

Computer Science Engineering (CSE)

Practice Mode Previous Next
On This Page

This set of Communication Engineering Multiple Choice Questions & Answers (MCQs) focuses on Communication Engineering Set 13

Q1 | Which modulation scheme is preferred for direct sequence spread spectrum process?
  • bpsk
  • qpsk
  • bpsk & qpsk
  • none of the mentioned
Answer: bpsk & qpsk
Explaination:
both the modulation scheme bpsk and qpsk can be used for direct sequence spread spectrum process.
Q2 | The processing gain is given as              modulation scheme.
  • wss/r
  • r/wss
  • wss/2r
  • r/2wss
Answer: wss/r
Explaination:
the processing gain is given by
Q3 | The minimum spacing between consecutive hop positions gives the
  • minimum number of chips necessary
  • maximum number of chips necessary
  • chip rate
  • none of the mentioned
Answer: minimum number of chips necessary
Explaination:
the minimum spacing between consecutive hop positions given the minimum number of chips necessary in the frequency word.
Q4 | Which system allows larger processing gain?
  • direct sequence
  • frequency hopping
  • direct sequence & frequency hopping
  • none of the mentioned
Answer: frequency hopping
Explaination:
frequency hopping spread spectrum system allows greater processing gain than direct sequence spread spectrum technique.
Q5 | In which technique is phase coherence hard to maintain?
  • direct sequence
  • frequency hopping
  • direct sequence & frequency hopping
  • none of the mentioned
Answer: frequency hopping
Explaination:
in frequency hopping spread spectrum phase coherence is hard to maintain from hop to hop.
Q6 | Which type of demodulator is used in the frequency hopping technique?
  • coherent
  • non coherent
  • coherent & non coherent
  • none of the mentioned
Answer: non coherent
Explaination:
as it is difficult to maintain phase coherence, non coherent demodulator is used.
Q7 | Robustness gives the inability of a signal to withstand the impairments.
  • true
  • false
Answer: false
Explaination:
robustness gives the ability of a signal to withstand the impairments such as noise, jamming etc.
Q8 | Chips are the
  • repeated symbols
  • non repeated symbols
  • smallest length symbols
  • none of the mentioned
Answer: repeated symbols
Explaination:
the repeated symbols are called as chips.
Q9 | Slow frequency hopping is
  • several hops per modulation
  • several modulations per hop
  • several symbols per modulation
  • none of the mentioned
Answer: several modulations per hop
Explaination:
slow frequency hopping is several modulation per frequency hop.
Q10 | Fast frequency hopping is
  • several modulations per hop
  • several modulations per symbol
  • several symbols per modulation
  • none of the mentioned
Answer: none of the mentioned
Explaination:
fast frequency hopping is several frequency hops per modulation.
Q11 | Which duration is shorter?
  • hop duration
  • symbol duration
  • chip duration
  • none of the mentioned
Answer: hop duration
Explaination:
in frequency hopping technique hop duration is shorter than the symbol duration.
Q12 | Frequency division multiple access (FDMA) assigns              channels to                 users.
  • individual, individual
  • many, individual
  • individual, many
  • many, many
Answer: individual, individual
Explaination:
frequency division multiple access (fdma) assigns individual channels to individual users. each user is allocated a unique frequency band or channel. these channels are assigned on demand to users who request service.
Q13 | If the FDMA channel is not in use, it can be used by other users.
  • true
  • false
Answer: false
Explaination:
if an fdma channel is not in use, it sits idle and cannot be used by other users to increase or share capacity. it is essentially a wasted resource.
Q14 | The bandwidth of FDMA channel is
  • wide
  • narrow
  • large
  • zero
Answer: narrow
Explaination:
the bandwidth of fdma channels is relatively narrow as each channel supports only one circuit per carrier. that is, fdma is usually implemented in narrow band systems.
Q15 | Which of the following is not true for FDMA systems as compared to TDMA systems?
  • low complexity
  • lower cell site system cost
  • tight rf filtering
  • narrow bandwidth
Answer: lower cell site system cost
Explaination:
fdma systems have higher cell site system costs as compared to tdma systems. it is due to single channel per carrier design, and the need to use costly bandpass filters to eliminate spurious radiation at the base station.
Q16 |                      is undesired RF radiation.
  • intermodulation frequency
  • intermediate frequency
  • instantaneous frequency
  • instrumental frequency
Answer: intermodulation frequency
Explaination:
intermodulation (im) frequency is undesired rf radiation which can interfere with other channels in the fdma systems. the nonlinearities cause signal spreading in the frequency domain and generate im frequency.
Q17 |                      is based on FDMA/FDD.
  • gsm
  • w-cdma
  • cordless telephone
  • amps
Answer: amps
Explaination:
the first us analog cellular system, the advanced mobile phone system (amps) is based on fdma/fdd. a single user occupies a single channel while the call is in progress.
Q18 | In US AMPS, 416 channels are allocated to various operators with 10 kHz guard band and channel between them is 30 kHz. What is the spectrum allocation given to each operator?
  • 12.5 khz
  • 30 khz
  • 12.5 mhz
  • 30 mhz
Answer: 12.5 mhz
Explaination:
spectrum allocated to each cellular operator is 12.5 mhz. as bt = nbc + 2bguard; which is equal to 416*30*103+2(10*103) = 12.5 mhz.
Q19 | TDMA systems transmit in a continuous way.
  • true
  • false
Answer: false
Explaination:
tdma systems transmit data in a buffer and burst method. thus, the transmission for any user is not continuous.
Q20 |                      are utilized to allow synchronization of the receivers between different slots and frames.
  • preamble
  • data
  • guard bits
  • trail bits
Answer: guard bits
Explaination:
guard times are utilized to allow synchronization of the receivers between different slots and frames.
Q21 | Which of the following is not true for TDMA?
  • single carrier frequency for single user
  • discontinuous data transmission
  • no requirement of duplexers
  • high transmission rates
Answer: single carrier frequency for single user
Explaination:
tdma share a single carrier frequency with several users, where each user makes use of non-overlapping time slots. the number of time slots per frame depends on several factors, such as modulation technique, available bandwidth etc.
Q22 | Because of                transmissions in TDMA, the handoff process in                      
  • continuous, complex
  • continuous, simple
  • discontinuous, complex
  • discontinuous, simple
Answer: discontinuous, simple
Explaination:
because of discontinuous transmissions in tdma, the handoff process is much simpler for a subscriber unit, since it is able to listen for other base stations during idle time slots.
Q23 |                      synchronization overhead is required in TDMA due to                 transmission.
  • high, burst
  • high, continuous
  • low, burst
  • no, burst
Answer: high, burst
Explaination:
high synchronization overhead is required in tdma systems because of burst transmissions. tdma transmissions are slotted, and this requires the receivers to be synchronized for each data burst.
Q24 | TDMA allocates a single time per frame to different users.
  • true
  • false
Answer: false
Explaination:
tdma has an advantage that it can allocate different numbers of time slots per frame to different users. thus, bandwidth can be supplied on demand to different users by concatenating or reassigning time slots based on priority.
Q25 |                        of TDMA system is a measure of the percentage of transmitted data that contains information as opposed to providing overhead for the access scheme.
  • efficiency
  • figure of merit
  • signal to noise ratio
  • mean
Answer: efficiency
Explaination:
efficiency of tdma system is a measure of the percentage of transmitted data that contains information as opposed to providing overhead for the access scheme.
Previous Next