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Recent questions in Communications
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answers
41
GATE ECE 2013 | Question: 48
Bits $1$ and $0$ are transmitted with equal probability. At the receiver, the pdf of the respective received signals for both bits are as shown below. If the detection threshold is $1,$ the $BER$ will be $\frac{1}{2} \\ $ $\frac{1}{4} \\$ $\frac{1}{8} \\$ $\frac{1}{16}$
Milicevic3306
asked
in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
62
views
gate2013-ec
communications
basic-electrical-rhythm
digital-modulation
0
votes
0
answers
42
GATE ECE 2013 | Question: 47
Let $U$ and $V$ be two independent and identically distributed random variables such that $P(U=+1)=P(U=-1) = \dfrac{1}{2}.$ The entropy $H(U + V)$ in bits is $\frac{3}{4} \\$ $1$ $\frac{3}{2} \\$ $\log_{2}3$
Milicevic3306
asked
in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
60
views
gate2013-ec
communications
entropy
0
votes
0
answers
43
GATE ECE 2013 | Question: 13
The bit rate of a digital communication system is $R$ kbits/s. The modulation used is $32$-QAM. The minimum bandwidth required for ISI free transmission is $R/10\: Hz$ $R/10\: kHz$ $R/5\: Hz$ $R/5\: kHz$
Milicevic3306
asked
in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
36
views
gate2013-ec
digital-communications
communications
0
votes
0
answers
44
GATE ECE 2012 | Question: 39
The signal $m(t)$ as shown is applied both to a phase modulator (with $k_p$ as the phase constant) and a frequency modulator (with $k_f$ as the frequency constant) having the same carrier frequency. The ratio $\frac{k_p}{k_f}$ (in $rad/Hz$) for the same maximum phase deviation is $8\pi$ $4\pi$ $2\pi$ $\pi$
Milicevic3306
asked
in
Communications
Mar 25, 2018
by
Milicevic3306
15.8k
points
86
views
gate2012-ec
communications
frequency-modulation
0
votes
0
answers
45
GATE ECE 2012 | Question: 27
A BPSK scheme operating over an AWGN channel with noise power spectral density of $\frac{N_o}{2}$, uses equiprobable signals $s_1(t)=\sqrt{\frac{2E}{T}}\sin(\omega_ct)$ and $s_2(t)=-\sqrt{\frac{2E}{T}}\sin(\omega_ct)$ over the symbol interval $(0,T)$. If the local oscillator ... $Q(\sqrt{\frac{E}{N_o}})$ $Q(\sqrt{\frac{E}{2N_o}})$ $Q(\sqrt{\frac{E}{4N_o}})$
Milicevic3306
asked
in
Communications
Mar 25, 2018
by
Milicevic3306
15.8k
points
55
views
gate2012-ec
communications
autocorrelation-and-power-spectral-density
0
votes
0
answers
46
GATE ECE 2012 | Question: 3
In a baseband communications link, frequencies upto $3500\:Hz$ are used for signaling. Using a raised cosine pulse with $75\%$ excess bandwidth and for no inter-symbol interference, the maximum possible signaling rate in the symbols per second is $1750$ $2625$ $4000$ $5250$
Milicevic3306
asked
in
Communications
Mar 25, 2018
by
Milicevic3306
15.8k
points
46
views
gate2012-ec
communications
calculation-of-bandwidth
0
votes
0
answers
47
GATE ECE 2012 | Question: 2
The power spectral density of a real process $X(t)$ for positive frequencies is shown below. The values of $E[X^2(t)]$ and $ \mid E[X(t)] \mid$, respectively, are $\frac{6000}{\pi}\:,\:0$ $\frac{6400}{\pi}\:,\:0$ $\frac{6400}{\pi}\:,\:\frac{20}{(\pi\sqrt2)}$ $\frac{6000}{\pi}\:,\:\frac{20}{(\pi\sqrt2)}$
Milicevic3306
asked
in
Communications
Mar 25, 2018
by
Milicevic3306
15.8k
points
53
views
gate2012-ec
communications
autocorrelation-and-power-spectral-density
0
votes
0
answers
48
GATE ECE 2018 | Question: 28
Consider a white Gaussian noise process $\text{N(t)}$ with two-sided power spectral density $S_{N}\left ( f \right )=0.5\:W/Hz$ as input to a filter with impulse response $0.5e^{-t^{2}/2}$ (where $t$ is in seconds) resulting in output $Y(t)$. The power in $Y(t)$ in watts is $0.11$ $0.22$ $0.33$ $0.44$
gatecse
asked
in
Communications
Feb 19, 2018
by
gatecse
1.5k
points
90
views
gate2018-ec
gaussian-noise
autocorrelation-and-power-spectral-density
communications
0
votes
0
answers
49
GATE ECE 2018 | Question: 27
Let $c\left ( t \right )=A_{c} \cos \left ( 2\pi f_{c}t\right )$ and $m\left ( t \right )=\cos \left ( 2\pi f_{m}t\right )$. It is given that $f_{c}>> 5f_{m}.$ The signal $c\left ( t \right )+m\left ( t \right )$ is applied to ... wave. If it is desired to have the sideband power of the AM wave to be half of the carrier power, then $a/b$ is $0.25$ $0.5$ $1$ $2$
gatecse
asked
in
Communications
Feb 19, 2018
by
gatecse
1.5k
points
55
views
gate2018-ec
communications
amplitude-modulation
0
votes
0
answers
50
GATE ECE 2018 | Question: 17
A binary source generates symbols $X\in \left \{ -1,1 \right \}$ which are transmitted over a noisy channel.The probability of transmitting $X=1$ is $0.5.$ Input to the threshold detector is $R=X+N$ ... is shown below. If the detection threshold is zero, then the probability of error (correct to two decimal places) is __________.
gatecse
asked
in
Communications
Feb 19, 2018
by
gatecse
1.5k
points
66
views
gate2018-ec
numerical-answers
probability-density-function
communications
0
votes
0
answers
51
GATE ECE 2018 | Question: 16
Consider a binary channel code in which each codeword has a fixed length of $5\: bits$. The Hamming distance between any pair of distinct codewords in this code is at least $2$. The maximum number of codewords such a code can contain is __________.
gatecse
asked
in
Communications
Feb 19, 2018
by
gatecse
1.5k
points
78
views
gate2018-ec
numerical-answers
communications
hamming-codes
0
votes
2
answers
52
GATE ECE 2018 | Question: 15
Consider the following amplitude modulated signal: $s\left ( t \right )=\cos\left ( 2000\:\pi t \right )+4\cos\left ( 2400\:\pi t \right )+ \cos\left ( 2800\:\pi t \right ).$The ratio (accurate to three decimal places) of the power of the message signal to the power of the carrier signal is _________.
gatecse
asked
in
Communications
Feb 19, 2018
by
gatecse
1.5k
points
172
views
gate2018-ec
numerical-answers
communications
amplitude-modulation
0
votes
0
answers
53
GATE ECE 2017 Set 2 | Question: 52
Consider a binary memoryless channel characterized by the transition probability diagram shown in the figure. The channel is lossless noiseless useless deterministic
admin
asked
in
Communications
Nov 25, 2017
by
admin
35.7k
points
179
views
gate2017-ec-2
channel-capacity-theorem
communications
0
votes
0
answers
54
GATE ECE 2017 Set 2 | Question: 51
A modulating signal given by $x(t)=5\sin (4\pi 10^3t -10\pi \cos 2\pi 10^3t)V$ is fed to a phase modulator with phase deviation constant $k_p=5$ rad/V. If the carrier frequency is $20$ kHz, the instantaneous frequency(in kHz) at $t=0.5$ ms is ____________
admin
asked
in
Communications
Nov 25, 2017
by
admin
35.7k
points
65
views
gate2017-ec-2
numerical-answers
communications
0
votes
0
answers
55
GATE ECE 2017 Set 2 | Question: 50
The unmodulated carrier power in an AM transmitter is $5$ kW. This carrier is modulated by a sinusoidal modulating signal. The maximum percentage of modulation is $50 \%$. If it is reduced to $40 \%$, then the maximum unmodulated carrier power (in kW) that can be used without overloading the transmitter is _________
admin
asked
in
Communications
Nov 25, 2017
by
admin
35.7k
points
154
views
gate2017-ec-2
amplitude-modulation
numerical-answers
communications
0
votes
0
answers
56
GATE ECE 2017 Set 2 | Question: 23
A sinusoidal message signal is converted to a PCM signal using a uniform quantizer. The required signal-to-quantization noise ratio (SQNR) at the output of the quantizer is $40$ dB. The minimum number of bits per sample needed to achieve the desired SQNR is __________
admin
asked
in
Communications
Nov 23, 2017
by
admin
35.7k
points
386
views
gate2017-ec-2
digital-communications
numerical-answers
pulse-code-modulation
0
votes
0
answers
57
GATE ECE 2017 Set 2 | Question: 21
Which one of the following graphs shows the Shannon capacity (channel capacity) in bits of a memoryless binary symmetric channel with crossover probability $p$ ?
admin
asked
in
Communications
Nov 23, 2017
by
admin
35.7k
points
262
views
gate2017-ec-2
channel-capacity-theorem
communications
0
votes
0
answers
58
GATE ECE 2017 Set 1 | Question: 50
In binary frequency shift keying (FSK), the given signal waveforms are $u_{0}(t)=5\, \cos(20000\pi t)\, ;0\leq t\leq T \text{, and } \\ u_{1}(t)=5\, \cos(22000\pi t)\, ;0 \leq t \leq T,$ where $T$ is the bit-duration interval and $t$ is in seconds ... (in milliseconds) required to have $u_{0}(t)$ and $u_{1}(t)$ uncorrelated is $0.25$ ms $0.5$ ms $0.75$ ms $1.0$ ms
admin
asked
in
Communications
Nov 17, 2017
by
admin
35.7k
points
114
views
gate2017-ec-1
digital-communication
frequency-shift-keying
communications
0
votes
0
answers
59
GATE ECE 2017 Set 1 | Question: 51
Let $X(t)$ be a wide sense stationary random process with the power spectral density $S_{X}(f)$ as shown in Figure (a), where $f$ is in Hertz$(Hz)$. The random process $X(t)$ ... Select the correct option: only I is true only II and III are true only I and II are true only I and III are true
admin
asked
in
Communications
Nov 17, 2017
by
admin
35.7k
points
51
views
gate2017-ec-1
autocorrelation-and-power-spectral-density
communications
0
votes
0
answers
60
GATE ECE 2017 Set 1 | Question: 23
In a digital communication system, the overall pulse shape $p(t)$ at the receiver before the sampler has the Fourier transform $P(f)$. If the symbols are transmitted at the rate of $2000$ symbols per second, for which of the following cases is the inter symbol interference zero?
admin
asked
in
Communications
Nov 17, 2017
by
admin
35.7k
points
277
views
gate2017-ec-1
digital-communication
communications
0
votes
0
answers
61
GATE ECE 2017 Set 1 | Question: 21
Let $\left ( X_{1},X_{2} \right )$ be independent random variables. $\left ( X_{1} \right )$ has mean $0$ and variance $1$, while $\left ( X_{2} \right )$ has mean $1$ and variance $4$. The mutual information $I\left (X_{1},X_{2} \right )$ between $X1$ and $X2$ in bits is_______.
admin
asked
in
Communications
Nov 17, 2017
by
admin
35.7k
points
50
views
gate2017-ec-1
information-theory
mutual-information
numerical-answers
communications
0
votes
0
answers
62
GATE ECE 2017 Set 1 | Question: 22
Which one of the following statements about differential pulse code modulation (DPCM) is true? The sum of message signal sample with its prediction is quantized The message signal sample is directly quantized, and its prediction is not ... signal sample and a random signal is quantized The difference of message signal sample with its prediction is quantized
admin
asked
in
Communications
Nov 17, 2017
by
admin
35.7k
points
1.1k
views
gate2017-ec-1
digital-communications
differential-pulse-code-modulation
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