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Most viewed questions in Communications
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1
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
0
votes
0
answers
2
GATE ECE 2016 Set 2 | Question: 48
An information source generates a binary sequence $\left \{ \alpha _{n} \right \}$. $\alpha _{n}$ can take one of the two possible values $-1$ and $+1$ with equal probability and are statistically independent and identically distributed. This sequence is precoded ... there is a null at $f=\frac{1}{3T}$ in the power spectral density of $X(t)$, then $k$ is ________
Milicevic3306
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in
Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
570
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gate2016-ec-2
numerical-answers
autocorrelation-and-power-spectral-density
communications
1
vote
0
answers
3
GATE ECE 2020 | Question: 8
The components in the circuit shown below are ideal. If the op-amp is in positive feedback and the input voltage $V_{i}$ is a sine wave of amplitude $1$ $\text{V}$, the output voltage $V_{o}$ is a non-inverted sine wave of $2$ $\text{V}$ amplitude. an inverted sine ... . a square wave of $5$ $\text{V}$ amplitude. a constant of either $+5$ $\text{V}$ or $-5$ $\text{V}$.
go_editor
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in
Communications
Feb 13, 2020
by
go_editor
1.9k
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444
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gate2020-ec
communications
amplitude
0
votes
0
answers
4
GATE ECE 2019 | Question: 7
A linear Hamming code is used to map $4-bit$ message to $7-bit$ codewords. The encoder mapping is linear. If the message $0001$ is mapped to the codeword $0000111$, and the message $0011$ is mapped to the codeword $1100110$, then the message $0010$ is mapped to $0010011$ $1100001$ $1111000$ $1111111$
Arjun
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in
Communications
Feb 12, 2019
by
Arjun
6.0k
points
426
views
gate2019-ec
communications
hamming-codes
0
votes
0
answers
5
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
6
GATE ECE 2016 Set 1 | Question: 49
A digital communication system uses a repetition code for channel encoding/decoding. During transmission, each bit is repeated three times ($0$ is transmitted as $000$, and $1$ is transmitted as $111$). It is assumed that the source puts ... a $1$. Assuming a binary symmetric channel with crossover probability $p=0.1$, the average probability of error is _________
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Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
345
views
gate2016-ec-1
numerical-answers
digital-communications
communications
0
votes
0
answers
7
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
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in
Communications
Nov 17, 2017
by
admin
35.7k
points
277
views
gate2017-ec-1
digital-communication
communications
0
votes
0
answers
8
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
9
GATE ECE 2020 | Question: 12
A digital communication system transmits a block of $N$ bits. The probability of error in decoding a bit is $\alpha$. The error event of each bit is independent of the error events of the other bits. The received block is declared erroneous if at least one of its bits is decoded ... $\alpha ^{N}$ $1-\alpha ^{N}$ $1-\left ( 1-\alpha \right )^{N}$
go_editor
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in
Communications
Feb 13, 2020
by
go_editor
1.9k
points
242
views
gate2020-ec
digital-communications
communications
0
votes
0
answers
10
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
2
answers
11
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
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in
Communications
Feb 19, 2018
by
gatecse
1.5k
points
172
views
gate2018-ec
numerical-answers
communications
amplitude-modulation
0
votes
0
answers
12
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
13
GATE ECE 2015 Set 3 | Question: 36
A three bit pseudo random number generator is shown. Initially the value of output $Y\equiv Y_{2} Y_{1} Y_{0}$ is set to $111.$ The value of output $Y$ after three clock cycles is $000$ $001$ $010$ $100$
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Communications
Mar 28, 2018
by
Milicevic3306
15.8k
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129
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gate2015-ec-3
communications
pseudo-random-number
0
votes
0
answers
14
GATE ECE 2020 | Question: 42
For the modulated signal $x\left ( t \right )=m\left ( t \right )\cos\left ( 2\pi f_{c}t \right )$, the message signal $m\left ( t \right )=4\cos\left ( 1000\pi t \right )$ and the carrier frequency $f_{c}$ is $1\: MHz$. The signal $x(t)$ is passed ... $\cos\left ( 920\pi t \right )$ $\cos\left ( 1000\pi t \right )$ $\cos\left ( 540\pi t \right )$
go_editor
asked
in
Communications
Feb 13, 2020
by
go_editor
1.9k
points
124
views
gate2020-ec
communications
demodulator
0
votes
0
answers
15
GATE ECE 2019 | Question: 46
A voice signal $m(t)$ is in the frequency range $5\:kHz$ to $15\:kHz$. The signal is amplitude-modulated to generated an AM signal $f(t)=A\left(1+m(t)\right)\cos 2\pi f_{c}t,$ where $f_{c}=600\: kHz.$ ... for the encoding. The rate, in Megabits per second (rounded off to $2$ decimal places), of the resulting stream of coded bits is ________ Mbps.
Arjun
asked
in
Communications
Feb 12, 2019
by
Arjun
6.0k
points
114
views
gate2019-ec
numerical-answers
communications
amplitude-modulation
0
votes
0
answers
16
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
17
GATE ECE 2020 | Question: 22
A binary random variable $X$ takes the value $+2$ or $-2$. The probability $P(X=+2)=\alpha $. The value of $\alpha$ (rounded off to one decimal place), for which the entropy of $X$ is maximum, is __________.
go_editor
asked
in
Communications
Feb 13, 2020
by
go_editor
1.9k
points
96
views
gate2020-ec
numerical-answers
entropy
communications
0
votes
0
answers
18
GATE ECE 2015 Set 3 | Question: 22
The modulation scheme commonly used for transmission from GSM mobile terminals is $4$-QAM $16$-PSK Walsh-Hadamard orthogonal codes Gaussian Minimum Shift Keying (GMSK)
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in
Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
91
views
gate2015-ec-3
communications
gaussian-minimum-shift-keying
0
votes
0
answers
19
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
20
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
21
GATE ECE 2014 Set 2 | Question: 23
Consider sinusoidal modulation in an AM system. Assuming no overmodulation, the modulation index ($\mu$) when the maximum and minimum values of the envelope, respectively, are $3$ V and $1$ V, is ___________.
Milicevic3306
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in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
85
views
gate2014-ec-2
numerical-answers
communications
amplitude-modulation
0
votes
0
answers
22
GATE ECE 2016 Set 2 | Question: 49
An ideal band-pass channel $500 \: Hz â€“2000 \:Hz$ is deployed for communication. A modem is designed to transmit bits at the rate of $4800$ bits/s using $16-QAM$. The roll-off factor of a pulse with a raised cosine spectrum that utilizes the entire frequency band is __________
Milicevic3306
asked
in
Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
83
views
gate2016-ec-2
numerical-answers
communications
0
votes
0
answers
23
GATE ECE 2014 Set 3 | Question: 51
In a $PCM$ system, the signal $m(t)=\left \{\sin(100\pi t)+\cos(100\pi t) \right \}V$ is sampled at the Nyquist rate. The samples are processed by a uniform quantizer with step size $0.75$ $V$. The minimum data rate of the $PCM$ system in bits per second is ______.
Milicevic3306
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in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
82
views
gate2014-ec-3
numerical-answers
digital-communications
pulse-code-modulation-systems
communications
0
votes
0
answers
24
GATE ECE 2013 | Question: 49
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. The optimum threshold to achieve minimum bit error rate $(BER)$ is $\frac{1}{2} \\$ $\frac{4}{5} \\$ $1\\$ $\frac{3}{2} $
Milicevic3306
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in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
81
views
gate2013-ec
communications
digital-modulation
basic-electrical-rhythm
0
votes
0
answers
25
GATE ECE 2016 Set 1 | Question: 21
Consider binary data transmission at a rate of $56$ kbps using baseband binary pulse amplitude modulation (PAM) that is designed to have a raised-cosine spectrum. The transmission bandwidth (in kHz) required for a roll-off factor of $0.25$ is ________
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in
Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
80
views
gate2016-ec-1
numerical-answers
communications
modulation
0
votes
0
answers
26
GATE ECE 2014 Set 3 | Question: 19
A modulated signal is $y(t)= m(t)\cos(40000\pi t)$, where the baseband signal $m(t)$ has frequency components less than $5$ KHz only. The minimum required rate (in KHz) at which $y(t)$ should be sampled to recover $m(t)$ is _______.
Milicevic3306
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in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
80
views
gate2014-ec-3
numerical-answers
digital-communications
communications
0
votes
0
answers
27
GATE ECE 2014 Set 3 | Question: 50
A real band-limited random process $X(t)$ ... -pass filter of unity gain with centre frequency of $8$ $kHz$ and band-width of $2$ kHz. The output power (in Watts) is ___________.
Milicevic3306
asked
in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
80
views
gate2014-ec-3
numerical-answers
autocorrelation-and-power-spectral-density
communications
0
votes
0
answers
28
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
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in
Communications
Feb 19, 2018
by
gatecse
1.5k
points
78
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gate2018-ec
numerical-answers
communications
hamming-codes
0
votes
0
answers
29
GATE ECE 2015 Set 2 | Question: 51
Consider a binary, digital communication system which uses pulses $g(t)$ and $-g(t)$ for transmitting bits over an AWGN channel. If the receiver uses a matched filter, which one of the following pulses will give the minimum probability of bit error?
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Communications
Mar 28, 2018
by
Milicevic3306
15.8k
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74
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gate2015-ec-2
digital-communications
communications
0
votes
0
answers
30
GATE ECE 2016 Set 3 | Question: 23
A binary baseband digital communication system employs the signal $p(t) = \begin{cases}\large\frac{1}{\sqrt T_s},&0\leq t\leq T_s \\ \: 0, & \text{otherwise} \end{cases}$ for transmission of bits. The graphical representation of the matched filter output $y(t)$ for this signal will be
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Communications
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by
Milicevic3306
15.8k
points
72
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gate2016-ec-3
digital-communications
communications
0
votes
0
answers
31
GATE ECE 2019 | Question: 34
A single bit, equally likely to be $0$ and $1$, is to be sent across an additive white Gaussian noise (AWGN) channel with power spectral density $N_{0}/2.$ Binary signaling with $0 \mapsto p(t),$ and $1 \mapsto q(t),$ is used for the transmission, along with ... $E$ would we obtain the $\textbf{same}$ bit-error probability $P_{b}$? $0$ $1$ $2$ $3$
Arjun
asked
in
Communications
Feb 12, 2019
by
Arjun
6.0k
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67
views
gate2019-ec
gaussian-noise
autocorrelation-and-power-spectral-density
communications
0
votes
0
answers
32
GATE ECE 2014 Set 1 | Question: 51
Let $Q(\sqrt{\gamma})$ be the BER of a BPSK system over an AWGN channel with two-sided noise power spectral density $N_{0}/2.$ The parameter $\gamma$ is a function of bit energy and noise power spectral density. A system with two independent and identical ... both the channels. If the BER of this system is $Q( b \sqrt{\gamma})$ then the value of $b$ is _____.
Milicevic3306
asked
in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
66
views
gate2014-ec-1
numerical-answers
communications
digital-modulation
basic-electrical-rhythm
0
votes
0
answers
33
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 __________.
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Communications
Feb 19, 2018
by
gatecse
1.5k
points
66
views
gate2018-ec
numerical-answers
probability-density-function
communications
0
votes
0
answers
34
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 ____________
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in
Communications
Nov 25, 2017
by
admin
35.7k
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65
views
gate2017-ec-2
numerical-answers
communications
0
votes
0
answers
35
GATE ECE 2014 Set 2 | Question: 40
In the circuit shown, choose the correct timing diagram of the output (y) from the given waveforms $W1$, $W2$, $W3$ and $W4$. $W1$ $W2$ $W3$ $W4$
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Communications
Mar 26, 2018
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Milicevic3306
15.8k
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64
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gate2014-ec-2
communications
timing-diagram
0
votes
0
answers
36
GATE ECE 2014 Set 3 | Question: 23
Consider an $FM$ signal $f(t)= \cos\left [ 2\pi f_{c} t+\beta _{1}\sin2\pi f_{1}t+\beta _{2}\sin2\pi f_{2}t\right ].$ The maximum deviation of the instantaneous frequency from the carrier frequency $f_{c}$ is $\beta _{1}f_{1}+\beta _{2}f_{2}$ $\beta _{1}f_{2}+\beta _{2}f_{1}$ $\beta _{1}+\beta _{2}$ $f _{1}+f _{2}$
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Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
62
views
gate2014-ec-3
digital-communications
frequency-modulation
communications
0
votes
0
answers
37
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} \\ $ $\frac{1}{4} \\$ $\frac{1}{8} \\$ $\frac{1}{16}$
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Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
62
views
gate2013-ec
communications
basic-electrical-rhythm
digital-modulation
0
votes
0
answers
38
GATE ECE 2019 | Question: 45
Let a random process $Y(t)$ be described as $Y(t)=h(t) \ast X(t)+Z(t),$ where $X(t)$ is a white noise process with power spectral density $S_{x}(f)=5$W/Hz. The filter $h(t)$ ... power spectral density as shown in the figure. The power in $Y(t),$ in watts, is equal to _________ $W$ (rounded off to two decimal places).
Arjun
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Communications
Feb 12, 2019
by
Arjun
6.0k
points
61
views
gate2019-ec
numerical-answers
communications
autocorrelation-and-power-spectral-density
0
votes
0
answers
39
GATE ECE 2014 Set 2 | Question: 50
Coherent orthogonal binary FSK modulation is used to transmit two equiprobable symbol waveforms $s_{1}( t )= \alpha \cos 2\pi f_1 t$, and $s_2(t) = \alpha \cos 2 \pi f_2 t$ where $\alpha = 4$ ... error probability for a data rate of $500$ kbps is $Q(2)$ $Q(2\sqrt{2})$ $Q(4)$ $Q(4\sqrt{2})$
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Communications
Mar 26, 2018
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Milicevic3306
15.8k
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61
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gate2014-ec-2
communications
frequency-shift-keying
0
votes
0
answers
40
GATE ECE 2014 Set 4 | Question: 51
An M-level PSK modulation scheme is used to transmit independent binary digits over a band-pass channel with bandwidth $100$ kHz. The bit rate is $200$ kbps and the system characteristic is a raised-cosine spectrum with $100 \%$ excess bandwidth. The minimum value of M is __________
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Communications
Mar 26, 2018
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Milicevic3306
15.8k
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60
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gate2014-ec-4
numerical-answers
communications
phase-shift-keying
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