Digital Communications

Structured Sequence

Question 1
Marks : +2 | -2
Pass Ratio : 100%
In Gaussian channel demodulator ______ decision is made.
Hard
Soft
Hard & Soft
None of the mentioned
Explanation:
In Gaussian channel demodulator consists of continuous alphabet or quantized approximation thus soft decision is made.
Question 2
Marks : +2 | -2
Pass Ratio : 100%
In binary symmetric channel, in the demodulator _____ decision is made.
Hard
Soft
Hard & Soft
None of the mentioned
Explanation:
In binary symmetric channel the demodulator consists of only two discrete elements. Thus it makes hard or firm decision.
Question 3
Marks : +2 | -2
Pass Ratio : 100%
Structured sequences are
Block codes
Convolutional codes
Turbo codes
All of the mentioned
Explanation:
Structured sequences are those which add structured redundancy to the source code. Examples are turbo codes, block codes, and convolutional codes.
Question 4
Marks : +2 | -2
Pass Ratio : 100%
In a real time communication system addition of redundant bits leads to
More bandwidth requirement
Faster rate of transmission
More bandwidth requirement & Faster rate of transmission
None of the mentioned
Explanation:
In a real time communication system the addition of redundant bits dictates a faster transmission rate and which means more bandwidth.
Question 5
Marks : +2 | -2
Pass Ratio : 100%
The ratio of redundant bits to data bits is called as
Code rate
Redundancy rate
Symbol rate
Transmission rate
Explanation:
The ratio of redundant bits to data bits is called as redundancy of the code and the ratio of data bits to total bits is called as code rate.
Question 6
Marks : +2 | -2
Pass Ratio : 100%
The probability of message error is written as
Block error
Word error
Block & Word error
None of the mentioned
Explanation:
We can write the probability of message error also called as block error or word error.
Question 7
Marks : +2 | -2
Pass Ratio : 100%
Coding gain is defined as
Reduction in Eb/N0
Increase in Eb/N0
Same as Eb/N0
None of the mentioned
Explanation:
For a given bit error probability coding gain can be defined as reduction in Eb/N0 that can be realized through the use of code.
Question 8
Marks : +2 | -2
Pass Ratio : 100%
The summation operation is performed using _____ logical operation.
EX-OR
AND
OR
EX-NOR
Explanation:
The summation operation is performed using modulo 2 arithmetic or exclusive OR operation.
Question 9
Marks : +2 | -2
Pass Ratio : 100%
Which decoders are less complex?
Soft decision decoder
Hard decision decoder
Hard & Soft decision decoder
None of the mentioned
Explanation:
The design of a soft decision decoder is more complex than the design of hard decision decoder.
Question 10
Marks : +2 | -2
Pass Ratio : 100%
If the parity bit takes value one then the summation of code-word gives
Even result
Odd result
Even & Odd result
None of the mentioned
Explanation:
The parity bit takes on the value of one or zero to ensure that the summation of all the bits in the code-word yields even or odd result.