WorksheetsEC8501 DIGITAL COMMUNICATION IAE#1
Total questions: 50
Worksheet time: 50mins
If a signal is defined only at specific instants of time, then it is known as a ________ signal.
Continuous time
Analog
Digital
Discrete time
If a signal is defined for all instants of time, then it is known as a ________ signal.
Continuous time
Analog
Digital
Discrete time
Identify the type of signal.
Discrete time signal
Continuous time signal
Identify the type of signal.
Analog signal
Digital signal
Select the advantages of Digital communication
Digital cable systems are more economical.
Digital signal characteristics are convenient for electronic switching.
The transmission of digital signals requires circuits with a very large bandwidth.
All the above.
For M equally likely messages, the average amount of information H is
H = log10M
H = log2M
H = log10M2
H = 2log10M
The channel capacity is
The maximum information transmitted by one symbol over the channel
Information contained in a signal
The amplitude of the modulated signal
All of the above
According to Shannon Hartley theorem,
The channel capacity becomes infinite with infinite bandwidth
The channel capacity does not become infinite with infinite bandwidth
Has a tradeoff between bandwidth and Signal to noise ratio
The channel capacity does not become infinite with infinite bandwidth and has a tradeoff between bandwidth and Signal to noise ratio
The channel capacity according to Shannon's equation is
Maximum error free communication
Defined for optimum system
Information transmitted
All of the above
The technique that may be used to increase average information per bit is
Shannon-Fano algorithm
ASK
FSK
Digital modulation techniques
Information rate is defined as
Information per unit time
Average number of bits of information per second
rH
All of the above
The mutual information
Is symmetric
Always non negative
Is symmetric & Always non negative
None of the above
Entropy is
Average information per message
Information in a signal
Amplitude of signal
All of the above
The memory less source refers to
No previous information
No message storage
Emitted message is independent of previous message
None of the above
The expected information contained in a message is called
Entropy
Efficiency
Coded signal
None of the above
In discrete memoryless source, the current letter produced by a source is statistically independent of _____
Past output
Future output
Past output & Future output
None of the above
Huffman coding technique is adopted for constructing the source code with ________ redundancy.
Maximum
Constant
Minimum
Unpredictable
Which type of channel does not represent any correlation between input and output symbols?
Noiseless Channel
Lossless Channel
Useless Channel
Deterministic Channel
In digital communication system, smaller the code rate, _________are the redundant bits.
less
more
equal
unpredictable
Shannon and Weaver’s (1949) model of communication has the following components: ______.
precontemplation, contemplation, preparation, action, maintenance
product, price, place, promotion
source, transmitter, channel, receiver, destination
none of these
Select the source coding techniques.
prefix coding
Shannon-fano coding
Huffman coding
All of the mentioned.
Granular noise occurs when
a. Step size is too small
b. Step size is too large
c. There is interference from the adjacent channel
d. Bandwidth is too large
The channel capacity according to Shannon’s equation is
a. Maximum error free communication
b. Defined for optimum system
c. Information transmitted
d. All of the above
For a binary symmetric channel, the random bits are given as
Logic 1 given by probability P and logic 0 by (1-P)
Logic 1 given by probability P and logic 0 by (1-P)
Logic 1 given by probability P2 and logic 0 by 1-P
Logic 1 given by probability P and logic 0 by (1-P)2
For M equally likely messages, M>>1, if the rate of information R > C, the probability of error is
Arbitrarily small
Close to unity
Not predictable
Unknown
According to Shannon Hartley theorem,
the channel capacity becomes infinite with infinite bandwidth
channel capacity does not become infinite with infinite bandwidth
as a tradeoff between bandwidth and Signal to noise ratio
Both b) and c) are correct
The capacity of a binary symmetric channel, given H(P) is binary entropy function, is
1-H(P)
1-H(P)2
The channel capacity is
The maximum information transmitted by one symbol over the channel
Information contained in a signal
The amplitude of the modulated signal
All of the above
The information I contained in a message with probability of occurrence is given by (k is constant)
I = k log21/P
. I = k log2P
. I = k log21/2P
. I = k log21/P2
The relation between entropy and mutual information is
I(X;Y) = H(X) – H(X/Y)
I(X;Y) = H(X/Y) – H(Y/X)
I(X;Y) = H(Y) – H(X)
I(X;Y) = H(Y) – H(X)
The mutual information is
Is symmetric
Always non nagative
Both a and b correct
None of the above
The channel capacity according to Shannon’s equation is
Maximum error free communication
Defined for optimum system
Information transmitted
All of the above
The technique that may be used to increase average information per bit is
Shannon Fano Algorithm
ASK
FSK
Digital modulation techniques
The information rate R for given average information H= 2.0 for analog signal band limited to B Hz is
a. 8 B bits/sec
b. 4 B bits/sec
c. 2 B bits/sec
d. 16 B bits/sec
The memory less source refers to
a. No previous information
b. No message storage
c. Emitted message is independent of previous message
d. None of the above
The expected information contained in a message is called
a. Entropy
b. Efficiency
c. Coded signal
d. None of the above
As per Shannon-Hartley theorem, a noise less Gaussian channel has
A.zero capacity
B.infinite capacity
C.small capacity
D.none of the above
On which factor/s do/does the channel capacity depend/s in the digital communication system?
a. Bandwidth
b. Signal to Noise Ratio
c. Both a and b
d. None of the above
In digital communication system, smaller the code rate, _________are the redundant bits
a. less
b. more
c. equal
d. unpredictable
Hartley’s Law is:
a. I = ktB
b. C = 2B log2M
c. C = B log2(1 + S/N)
d. SR = 2fmax
The Shannon Limit is given by:
a. I = ktB
b. C = 2Blog2M
c. C = Blog2(1 + S/N)
d. SR = 2fmax
In discrete memoryless source, the current letter produced by a source is statistically independent of _____
a. Past output
b. Future output
c. Both a and b
d. None of the above
According to Shannon's second theorem, it is not feasible to transmit information over the channel with ______error probability, although by using any coding technique.
a. small
b. large
c. stable
d. unpredictable
The negative statement for Shannon's theorem states that
a. If R = C, the error probability increases towards Unity
b. If R < C, the error probability is very small
c. Both a & b
d. None of the above
For M equally likely messages, M>>1, if the rate of information R ≤ C, the probability of error is
a. Arbitrarily small
b. Close to unity
c. Not predictable
d. Unknown
For M equally likely messages, M>>1, if the rate of information R > C, the probability of error is
a. Arbitrarily small
b. Close to unity
c. Not predictable
d. Unknown
The negative statement for Shannon’s theorem states that
a. If R > C, the error probability increases towards Unity
b. If R < C, the error probability is very small
c. Both a & b
d. None of the above
