1
GATE ECE 2007
MCQ (Single Correct Answer)
+2
-0.6
An input to a 6-level quantizer has the probability density function f(X) as shown in the figure. Decision boundaries of the quantizer are chosen so as to maximize the entropy of the quantizer output. It is given that 3 consecutive decision boundaries are ‘-1’, ‘0’ and ‘1’. GATE ECE 2007 Communications - Noise In Digital Communication Question 21 English

Assuming that the reconstruction levels of the quantizer are the mid-points of the decision boundaries, the ratio of signal power to quantization noise power is

A
$${152 \over 9}$$
B
$${64 \over 3}$$
C
$${76 \over 3}$$
D
$$28$$
2
GATE ECE 2007
MCQ (Single Correct Answer)
+2
-0.6
Two 4-ray signal constellations are shown. It is given that $${\phi _1}$$ and $${\phi _2}$$ constitute an orthonormal basis for the two constellations. Assume that the four symbols in both the constellations are equiprobable. Let $${{{N_0}} \over 2}$$ denote the power spectral density of white Gaussian noise. GATE ECE 2007 Communications - Noise In Digital Communication Question 20 English

The ratio of the average energy of Constellation 1 to the average energy of Constellation 2 is

A
$$4{a^2}$$
B
$$4$$
C
$$2$$
D
$$8$$
3
GATE ECE 2007
MCQ (Single Correct Answer)
+2
-0.6
Two 4-ray signal constellations are shown. It is given that $${\phi _1}$$ and $${\phi _2}$$ constitute an orthonormal basis for the two constellations. Assume that the four symbols in both the constellations are equiprobable. Let $${{{N_0}} \over 2}$$ denote the power spectral density of white Gaussian noise. GATE ECE 2007 Communications - Noise In Digital Communication Question 19 English

If these constellations are used for digital communications over an AWGN channel, then which of the following statements is true?

A
Probability of symbol error for Constellation 1 is lower
B
Probability of symbol error for Constellation 1 is higher
C
Probability of symbol error is equal for both the constellations
D
The value of N0 will determine which of the two constellations has a lower probability of symbol error.
4
GATE ECE 2006
MCQ (Single Correct Answer)
+2
-0.6
In the following figure the minimum value of the constant “C”, which is to be added to y1(t) such that y1(t) and y2(t) are different, is GATE ECE 2006 Communications - Noise In Digital Communication Question 25 English
A
$$\Delta $$
B
$${\Delta \over 2}$$
C
$${{{\Delta ^2}} \over {12}}$$
D
$${\Delta \over L}$$
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