Test: Digital Communications - 2

Question 1

The Autocorrelation function is given by exp . Then the PSD is given by

Accepted Answer

Answer

Answer

Answer

Question 2

X is a binary memory less source with p (x = 0) = 0.3. If the source is transmitted over a BSC with cross-over probability = 0.1, then the capacity of the channel is

Accepted Answer

0.531&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;

Answer

0.231&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;

Answer

0.441&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;

Answer

0.881

Question 3

Two binary random variables X and Y are distributed according to the joint distributions p(x = y = 0) = p(x = 0, y = 1) = p(x = y = 1) = 1/3. Then the entropy

H(x) is

Accepted Answer

0.9183

Answer

0.9327

Answer

0.9651

Answer

0.9832

Question 4

In a Binary digital communication system, the threshold voltage of comparator is 'x' volts and voltage at input of comparator is uniformly distributed in the range of x-0.5 to x+0.25 when '0' is transmitted and it is in the range x-0.25 to x+0.5 when bit '1' is transmitted, the average probability of error in the system is_____________

Accepted Answer

Question 5

If probability of error of PSK signal is 'x', then what will be probability of error of FSK and ASK signal. (Assume x =

Accepted Answer

None of these

Answer

respectively

Answer

respectively

Answer

respectively

Question 6

If input to matched filter is s(t) = f(t)+ 2f (t)δ(t - 0.5) + f(t - 2.5)*8δ(t+ 0.5)

where f(t) is shown below, then determine the impulse response of matched filter h(t) ; 2 5 ≤ t < 3

(Note: δ is Delta function and * is convolution operator)

Accepted Answer

- 2t + 6

Answer

t - 3

Answer

2t - 3

Answer

-2t - 6

Question 7

Match the following:

Modulation Type of signaling format to be

technique used for modulation

ASK (a) ON-OFF
PSK (b) Non return to zero
FSK (c) Return to zero
DPSK
QPSK

Accepted Answer

1- a 2,3,4,5 - b

Answer

1, 4 - a 2,3,5 - b

Answer

1- a 2,3 - b, 4,5-c

Answer

1- a 2,3,4 - b, 5-c

Question 8

Consider a BSC with cross-over probability of error P. Suppose that R is the number of bits in a source code word that represents one of 2^R possible levels at the output of quantizer. If R = 5, P = 0.01, then the probability of having 5 or less bits in error in a code word is_____________

Accepted Answer

Question 9

A black and white television picture may be viewed as consisting of approximately 3x10⁵ elements, each of which may occur one of 10 distinct brightness levels with equal probability. Transmission rate is 30 picture frames/ second and SNR is 30 dB. Then the minimum bandwidth required to support the transmission of the resulting video signal is MHz

Accepted Answer

Question 10

A random variable X has

Q. The value of constant K is

Accepted Answer

Answer

Answer

Answer

Question 11

A random variable X has

Q. The value of P(4 < x 5 ≤ 8) is

Accepted Answer

0.48&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;

Answer

0.24&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;

Answer

0.36&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;

Answer

0.64

Question 12

A telegraphic source has two symbols dot and dash. The dot duration is 0.2sec. The dash is twice as long as the dot and half as probable.

Q. The entropy of source is

Accepted Answer

0.92bits/symbol

Answer

1.92 bits/symbol

Answer

2.92bits/symbol

Answer

3.92bits/symbol

Question 13

A telegraphic source has two symbols dot and dash. The dot duration is 0.2sec. The dash is twice as long as the dot and half as probable.

Q. The information rate is

Accepted Answer

3.45 bits/sec

Answer

1.45bits/sec

Answer

2.45 bits/sec

Answer

4.45 bits/sec

Question 14

Consider a cascaded block of an LTI system

The impulse response of S_1. is h_1. t = δ t -2 The impulse response of 5₂ is h₂ t = t.e^-ru t

The input x(t) is wide sense stationary random process with R_xx 0 = 3 and variance = 1

Q. The mean of the random process w(t) is

Accepted Answer

Answer

W(t) will not be wide sense stationary so mean will not a be a constant.

Answer

1

Answer

2

Question 15

Consider a cascaded block of an LTI system

The impulse response of S_1. is h_1. t = δ t -2 The impulse response of 5₂ is h₂ t = t.e^-ru t

The input x(t) is wide sense stationary random process with R_xx 0 = 3 and variance = 1

Q. If w(t) is input to system 5₂, then mean of process Y(t) will be

Accepted Answer

Answer

Y(t) will not be, wide sense stationary thus mean is not a constant value

Answer

4

Answer

2

Question 16

CDF of a random variable x is given below.

Q. E[x] is

Accepted Answer

Answer

Answer

Answer

Question 17

CDF of a random variable x is given below.

Q. Variance is

Accepted Answer

Answer

Answer

Answer

Question 18

Consider a discrete memory less source X with two symbols x1 and x2 and P (x_i) = 0.9, P (x₂) = 0.1. These symbols are encoded as below.

Q. Find the source efficiency η

Accepted Answer

46.9%

Answer

34.5%&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;

Answer

53.1%

Answer

66%

Question 19

Consider a discrete memory less source X with two symbols x1 and x2 and P (x_i) = 0.9, P (x₂) = 0.1. These symbols are encoded as below.

Q. Find the redundancy γ

Accepted Answer

53%

Answer

33%&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;&#160;

Answer

66%

Answer

88%

Question 20

The input to a linear delta modulator having a step-size D = 0.628 is a sine wave with frequency f_m and peak amplitude E_m. If the sampling frequency f_s = 40kHz, the combination of the sine-wave frequency and peak amp, where slope overload will take place is
E_m    f_in E_m                    f_in
(a) 0.3V 8kHz                            (b)       1.5V                 4kHz
(c)          1.5V               2kHz                            (d)       3.0V                 1kHz

E_m f_in E_m f_in

(a) 0.3V 8kHz (b) 1.5V 4kHz

(c) 1.5V 2kHz (d) 3.0V 1kHz

Accepted Answer

b

Answer

a

Answer

c

Answer

d

GATE ECE (Electronics) Test: Digital Communications - 2 Free Online Test

MCQ Practice Test & Solutions: Test: Digital Communications - 2 (20 Questions)

The Autocorrelation function is given by exp . Then the PSD is given by

X is a binary memory less source with p (x = 0) = 0.3. If the source is transmitted over a BSC with cross-over probability = 0.1, then the capacity of the channel is

Two binary random variables X and Y are distributed according to the joint distributions p(x = y = 0) = p(x = 0, y = 1) = p(x = y = 1) = 1/3. Then the entropy
H(x) is

If probability of error of PSK signal is 'x', then what will be probability of error of FSK and ASK signal. (Assume x =

If input to matched filter is s(t) = f(t)+ 2f (t)δ(t - 0.5) + f(t - 2.5)8δ(t+ 0.5)
where f(t) is shown below, then determine the impulse response of matched filter h(t) ; 2 5 ≤ t < 3
(Note: δ is Delta function and is convolution operator)

Match the following:
Modulation             Type of signaling format to be
technique                     used for modulation
ASK               (a)       ON-OFF
PSK                (b)       Non return to zero
FSK                (c)       Return to zero
DPSK
QPSK

Consider a BSC with cross-over probability of error P. Suppose that R is the number of bits in a source code word that represents one of 2^R possible levels at the output of quantizer. If R = 5, P = 0.01, then the probability of having 5 or less bits in error in a code word is_____________

A random variable X has
Q. The value of constant K is

A random variable X has
Q. The value of P(4 < x 5 ≤ 8) is

A telegraphic source has two symbols dot and dash. The dot duration is 0.2sec. The dash is twice as long as the dot and half as probable.
Q. The entropy of source is

A telegraphic source has two symbols dot and dash. The dot duration is 0.2sec. The dash is twice as long as the dot and half as probable.
Q. The information rate is

Consider a cascaded block of an LTI system

The impulse response of S_1. is h_1. t = δ t -2 The impulse response of 5₂ is h₂ t = t.e^-ru t
The input x(t) is wide sense stationary random process with R_xx 0 = 3 and variance = 1
Q. The mean of the random process w(t) is

CDF of a random variable x is given below.
Q. E[x] is

CDF of a random variable x is given below.
Q. Variance is

Consider a discrete memory less source X with two symbols x1 and x2 and P (x_i) = 0.9, P (x₂) = 0.1. These symbols are encoded as below.
Q. Find the source efficiency η

Consider a discrete memory less source X with two symbols x1 and x2 and P (x_i) = 0.9, P (x₂) = 0.1. These symbols are encoded as below.
Q. Find the redundancy γ

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GATE ECE (Electronics) Test: Digital Communications - 2 Free Online Test

MCQ Practice Test & Solutions: Test: Digital Communications - 2 (20 Questions)

The Autocorrelation function is given by exp . Then the PSD is given by

X is a binary memory less source with p (x = 0) = 0.3. If the source is transmitted over a BSC with cross-over probability = 0.1, then the capacity of the channel is

Two binary random variables X and Y are distributed according to the joint distributions p(x = y = 0) = p(x = 0, y = 1) = p(x = y = 1) = 1/3 . Then the entropyH(x) is

If probability of error of PSK signal is 'x', then what will be probability of error of FSK and ASK signal. (Assume x =

If input to matched filter is s(t) = f(t)+ 2f (t)δ(t - 0.5) + f(t - 2.5)*8δ(t+ 0.5)where f(t) is shown below, then determine the impulse response of matched filter h(t) ; 2 5 ≤ t < 3(Note: δ is Delta function and * is convolution operator)

Match the following:Modulation Type of signaling format to betechnique used for modulationASK (a) ON-OFFPSK (b) Non return to zeroFSK (c) Return to zeroDPSKQPSK

Consider a BSC with cross-over probability of error P. Suppose that R is the number of bits in a source code word that represents one of 2R possible levels at the output of quantizer. If R = 5, P = 0.01, then the probability of having 5 or less bits in error in a code word is_____________

A random variable X has Q. The value of constant K is

A random variable X has Q. The value of P(4 < x 5 ≤ 8) is

A telegraphic source has two symbols dot and dash. The dot duration is 0.2sec. The dash is twice as long as the dot and half as probable.Q. The entropy of source is

A telegraphic source has two symbols dot and dash. The dot duration is 0.2sec. The dash is twice as long as the dot and half as probable.Q. The information rate is

Consider a cascaded block of an LTI system The impulse response of S1. is h1. t = δ t -2 The impulse response of 52 is h2 t = t.e-ru tThe input x(t) is wide sense stationary random process with Rxx 0 = 3 and variance = 1Q. The mean of the random process w(t) is

Consider a cascaded block of an LTI system The impulse response of S1. is h1. t = δ t -2 The impulse response of 52 is h2 t = t.e-ru tThe input x(t) is wide sense stationary random process with Rxx 0 = 3 and variance = 1Q. If w(t) is input to system 52, then mean of process Y(t) will be

CDF of a random variable x is given below.Q. E[x] is

CDF of a random variable x is given below.Q. Variance is

Consider a discrete memory less source X with two symbols x1 and x2 and P (xi) = 0.9, P (x2) = 0.1. These symbols are encoded as below.Q. Find the source efficiency η

Consider a discrete memory less source X with two symbols x1 and x2 and P (xi) = 0.9, P (x2) = 0.1. These symbols are encoded as below.Q. Find the redundancy γ

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GATE ECE (Electronics) Mock Test Series 2027

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Two binary random variables X and Y are distributed according to the joint distributions p(x = y = 0) = p(x = 0, y = 1) = p(x = y = 1) = 1/3. Then the entropy
H(x) is

If input to matched filter is s(t) = f(t)+ 2f (t)δ(t - 0.5) + f(t - 2.5)8δ(t+ 0.5)
where f(t) is shown below, then determine the impulse response of matched filter h(t) ; 2 5 ≤ t < 3
(Note: δ is Delta function and is convolution operator)

Match the following:
Modulation Type of signaling format to be
technique used for modulation
ASK (a) ON-OFF
PSK (b) Non return to zero
FSK (c) Return to zero
DPSK
QPSK

Consider a BSC with cross-over probability of error P. Suppose that R is the number of bits in a source code word that represents one of 2^R possible levels at the output of quantizer. If R = 5, P = 0.01, then the probability of having 5 or less bits in error in a code word is_____________

A random variable X has
Q. The value of constant K is

A random variable X has
Q. The value of P(4 < x 5 ≤ 8) is

A telegraphic source has two symbols dot and dash. The dot duration is 0.2sec. The dash is twice as long as the dot and half as probable.
Q. The entropy of source is

A telegraphic source has two symbols dot and dash. The dot duration is 0.2sec. The dash is twice as long as the dot and half as probable.
Q. The information rate is

Consider a cascaded block of an LTI system

The impulse response of S_1. is h_1. t = δ t -2 The impulse response of 5₂ is h₂ t = t.e^-ru t
The input x(t) is wide sense stationary random process with R_xx 0 = 3 and variance = 1
Q. The mean of the random process w(t) is

CDF of a random variable x is given below.
Q. E[x] is

CDF of a random variable x is given below.
Q. Variance is

Consider a discrete memory less source X with two symbols x1 and x2 and P (x_i) = 0.9, P (x₂) = 0.1. These symbols are encoded as below.
Q. Find the source efficiency η

Consider a discrete memory less source X with two symbols x1 and x2 and P (x_i) = 0.9, P (x₂) = 0.1. These symbols are encoded as below.
Q. Find the redundancy γ