WorksheetsEC8501 Digital Communication IAT I MCQ
Total questions: 25
Worksheet time: 59mins
The capacity of Gaussian channel is
C = 2B(1+S/N) bits/s
C = B2(1+S/N) bits/s
C = B(1+S/N) bits/s
C = B(1+S/N)2 bits/s
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
The capacity of a binary symmetric channel, given H(P) is binary entropy function is
1 - H(P)
H(P) - 1
1 - H(P)2
H(P)2 - 1
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
Both b and c are correct
The negative statement for Shannon's theorem states that
If R > C, the error probability increases towards Unity
If R < C, the error probability is very small
Both a & b
None 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 1-P and logic 0 by 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
The technique that may be used to increase average information per bit is
Shannon-Fano algorithm
ASK
FSK
Digital modulation techniques
Code rate r, k information bits and n as total bits, is defined as
r = k/n
k = n/r
r = k * n
n = r * k
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(X) - H(Y)
I(X;Y) = H(Y) - H(X)
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
When probability of error during transmission is 0.5, it indicates that
Channel is very noisy
No information is received
Channel is very noisy & No information is received
None of the mentioned
Find entropy when Pk = 0 & Pk = 1
0
1
1.5
2
When X and Y are statistically independent, then I (x,y) is
1
0
Ln 2
Cannot be determined
When the base of the logarithm is 2, then the unit of measure of information is
Bits
Bytes
Nats
None of the mentioned
In digital transmission, the modulation technique that requires minimum bandwidth is
Delta modulation
PCM
DPCM
PAM
In Differential Pulse Code Modulation techniques, the decoding is performed by
Accumulator
Sampler
PLL
Quantizer
The factors that cause quantizing error in delta modulation are
Slope overload distortion
Granular noise
White noise
Both a and b are correct
The digital modulation technique in which the step size is varied according to the variation in the slope of the input is called
Delta modulation
PCM
Adaptive delta modulation
PAM
Coding speech at lower bit rates is done by
Delta modulation
ADPCM
DPCM
PCM
An analog signal is bandlimited to B Hz, sampled at the Nyquist rate, and the samples are quantized into 4 levels. The quantization level Q1,Q2,Q3 and Q4 are assumed to be independent and occur with probabilities P1=P4=1/8 and P2=P3=3/8. Find the information rate of the source.
3.6 bits/sec
1.4 bits/sec
2.8 bits/sec
5.8 bits/sec
A source emitting symbols x, y, z with probabilities of 0.6, 0.3, 0.1 respectively. What is the entropy of the source?
2.525 bits/symbol
1.295 bits/symbol
0.532 bits/symbol
3.564 bits/symbol
An alphabet set contains 3 letters A, B, C transmitted with probabilities of 1/3, 1/4, 1/4. Find entropy.
2.42 bits/symbol
1.53 bits/symbol
3.25 bits/symbol
4.62 bits/symbol
A delta modulator with a fixed step size of 0.75V is given a sinusoidal signal. If the sampling frequency is 30 times the Nyquist rate, determine the maximum permissible amplitude of the message signal if slope overload is to be avoided
4.12 V
7.17 V
8.21 V
3.12 V
Consider the test signal m(t) defined by a hyperbolic tangent function where A and β are constants. Determine the minimum step size for delta modulation of this signal, which is required to avoid slope overload.
AβTS
Aβ
ATS
β
