Communication Engineering Set 11

Computer Science Engineering (CSE)

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This set of Communication Engineering Multiple Choice Questions & Answers (MCQs) focuses on Communication Engineering Set 11

Q1 | For a error free channel, conditional probability should be
  • zero
  • one
  • equal to joint probability
  • equal to individual probability
Answer: zero
Explaination:
for a error free channel
Q2 | Average effective information is obtained by
  • subtracting equivocation from entropy
  • adding equivocation with entropy
  • ratio of number of error bits by total number of bits
  • none of the mentioned
Answer: subtracting equivocation from entropy
Explaination:
according to shannon the average effective information is obtained by subtracting the equivocation from the entropy of the source.
Q3 | Turbo codes are
  • forward error correction codes
  • backward error correction codes
  • error detection codes
  • none of the mentioned
Answer: forward error correction codes
Explaination:
turbo codes are a class of high performance forward error correction codes.
Q4 | Components used for generation of turbo codes are
  • inter leavers
  • punching pattern
  • inter leavers & punching pattern
  • none of the mentioned
Answer: inter leavers & punching pattern
Explaination:
there are many instances of turbo codes, using different component encoders, input/output ratios, inter leavers, punching patterns.
Q5 | Decoders are connected in series.
  • true
  • false
Answer: true
Explaination:
two elementary decoders are
Q6 | The inter leaver connected between the two decoders is used to
  • remove error bursts
  • scatter error bursts
  • add error bursts
  • none of the mentioned
Answer: scatter error bursts
Explaination:
an inter leaver installed between the two decoders connected in series is used to scatter error bursts.
Q7 | In soft decision approach what does -127 mean?
  • certainly one
  • certainly zero
  • very likely zero
  • very likely one
Answer: certainly zero
Explaination:
the decoder front end produces an integer for each bit in the data stream. this integer is the measure of how likely it is that the bit 0 or 1 and is called as soft bit. it ranges from -127 to 127. here -127 represents certainly zero.
Q8 | In soft decision approach 100 means?
  • certainly one
  • certainly zero
  • very likely zero
  • very likely one
Answer: very likely one
Explaination:
the decoder front end produces an integer for each bit in the data stream. this integer is the measure of how likely it is that the bit 0 or 1 and is called as soft bit. it ranges from -127 to 127. here 100 represents very likely one.
Q9 | In soft decision approach 0 represents
  • certainly one
  • certainly zero
  • very likely zero
  • could be either zero or one
Answer: could be either zero or one
Explaination:
the decoder front end produces an integer for each bit in the data stream. this integer is the measure of how likely it is that the bit 0 or 1 and is called as soft bit. it ranges from -127 to 127. here 0 represents ‘could be either zero or one’.
Q10 | In layering, n layers provide service to
  • n layer
  • n-1 layer
  • n+1 layer
  • none of the mentioned
Answer: n+1 layer
Explaination:
in layering n layer provides service to n+1 layer and use the service provided by n-1 layer.
Q11 | Which can be used as an intermediate device in between transmitter entity and receiver entity?
  • ip router
  • microwave router
  • telephone switch
  • all of the mentioned
Answer: all of the mentioned
Explaination:
ip router, microwave router and telephone switch can be used as an intermediate device between communication of two entities.
Q12 | Which has comparatively high frequency component?
  • sine wave
  • cosine wave
  • square wave
  • none of the mentioned
Answer: square wave
Explaination:
square wave has comparatively high frequency component in them.
Q13 | Which has continuous transmission?
  • asynchronous
  • synchronous
  • asynchronous & synchronous
  • none of the mentioned
Answer: synchronous
Explaination:
synchronous has continuous transmission where as asynchronous have sporadic transmission.
Q14 | Which requires bit transitions?
  • asynchronous
  • synchronous
  • asynchronous & synchronous
  • none of the mentioned
Answer: synchronous
Explaination:
synchronous transmission needs bit transition.
Q15 | In synchronous transmission, receiver must stay synchronous for
  • 4 bits
  • 8 bits
  • 9 bits
  • 16 bits
Answer: 9 bits
Explaination:
in synchronous transmission, receiver must stay synchronous for 9 bits.
Q16 | How error detection and correction is done?
  • by passing it through equalizer
  • by passing it through filter
  • by amplifying it
  • by adding redundancy bits
Answer: by adding redundancy bits
Explaination:
error can be detected and corrected by adding additional information that is by adding redundancy bits.
Q17 | Which is more efficient?
  • parity check
  • cyclic redundancy check
  • parity & cyclic redundancy check
  • none of the mentioned
Answer: cyclic redundancy check
Explaination:
cyclic redundancy check is more efficient than parity check.
Q18 | Which can detect two bit errors?
  • parity check
  • cyclic redundancy check
  • parity & cyclic redundancy check
  • none of the mentioned
Answer: cyclic redundancy check
Explaination:
crc is more powerful and it can detect various kind of errors like 2 bit errors.
Q19 | CRC uses
  • multiplication
  • binary division
  • multiplication & binary division
  • none of the mentioned
Answer: multiplication & binary division
Explaination:
crc uses more math like multiplication and binary division.
Q20 | Block codes can achieve a larger coding gain than convolution coding.
  • true
  • false
Answer: false
Explaination:
convolution code can achieve a larger coding gain that can be achieved using a block coding with the same complexity.
Q21 | Which of the following indicates the number of input bits that the current output is dependent upon?
  • constraint length
  • code length
  • search window
  • information rate
Answer: constraint length
Explaination:
constraint length determines the number of input data bits that the current output is dependent upon. the constraint length determines how powerful and complex the code is.
Q22 | Which of the following is not a way to represent convolution code?
  • state diagram
  • trellis diagram
  • tree diagram
  • linear matrix
Answer: linear matrix
Explaination:
linear matrix is not a way to represent convolution code. various ways of representing convolution codes are generator matrix, generator polynomial, logic tables, state diagram, tree diagram and trellis diagram.
Q23 | Which of the following is not an algorithm for decoding convolution codes?
  • viterbi algorithm
  • stack algorithm
  • fano’s sequential coding
  • ant colony optimization
Answer: ant colony optimization
Explaination:
there are a number of techniques for decoding convolution codes. the most important of these methods is viterbi algorithm. other decoding algorithms for convolutional codes are fano’s sequential coding, stack algorithm and feedback coding.
Q24 | Fano’s algorithm searches all the paths of trellis diagram at same time to find the most probable path.
  • true
  • false
Answer: false
Explaination:
fano’s algorithm searches for the most probable path through the trellis diagram by examining one path at a time. the error rate performance of fano’s algorithm is comparable to viterbi’s algorithm.
Q25 | Which of the following is not an advantage of Fano’s algorithm in comparison to Viterbi’s algorithm?
  • less storage
  • large constraint length
  • error rate
  • small delays
Answer: small delays
Explaination:
in comparison to viterbi decoding, sequential decoding has a significantly larger delay. in advantage over viterbi decoding is that it requires less storage, and thus codes with larger constraint lengths can be employed.
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