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Recent questions in Communications
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1
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
asked
in
Communications
Feb 13, 2020
by
go_editor
1.9k
points
432
views
gate2020-ec
communications
amplitude
0
votes
0
answers
2
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
230
views
gate2020-ec
digital-communications
communications
0
votes
0
answers
3
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 __________.
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in
Communications
Feb 13, 2020
by
go_editor
1.9k
points
91
views
gate2020-ec
numerical-answers
entropy
communications
0
votes
0
answers
4
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 ... $\cos\left ( 920\pi t \right )$ $\cos\left ( 1000\pi t \right )$ $\cos\left ( 540\pi t \right )$
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in
Communications
Feb 13, 2020
by
go_editor
1.9k
points
116
views
gate2020-ec
communications
demodulator
0
votes
0
answers
5
GATE ECE 2020 | Question: 47
$S_{PM}(t)$ and $S_{FM}(t)$ as defined below, are the phase modulated and the frequency modlated waveforms, respectively, corresponding to the message signal $m(t)$ ... $S_{PM}(t)$ and $S_{FM}(t)$ are same, then the value of the ratio $\dfrac{K_{p}}{K_{f}}$ is ________ seconds.
go_editor
asked
in
Communications
Feb 13, 2020
by
go_editor
1.9k
points
50
views
gate2020-ec
numerical-answers
communications
frequency-modulation
0
votes
0
answers
6
GATE ECE 2020 | Question: 48
In a digital communication system, a symbol $S$ randomly chosen from the set $\left \{ s_{1},s_{2},s_{3},s_{4} \right \}$ is transmitted. It is given that $s_{1}=-3,s_{2}=-1,s_{3}=+1$ and $s_{4}=+2$. The received ... decoding when the transmitted symbol $S=s_{i}$. The index $i$ for which the conditional symbol error probability $P_{i}$ is the highest is ___________.
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in
Communications
Feb 13, 2020
by
go_editor
1.9k
points
49
views
gate2020-ec
numerical-answers
digital-communications
communications
0
votes
0
answers
7
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
418
views
gate2019-ec
communications
hamming-codes
0
votes
0
answers
8
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
points
64
views
gate2019-ec
gaussian-noise
autocorrelation-and-power-spectral-density
communications
0
votes
0
answers
9
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
asked
in
Communications
Feb 12, 2019
by
Arjun
6.0k
points
58
views
gate2019-ec
numerical-answers
communications
autocorrelation-and-power-spectral-density
0
votes
0
answers
10
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
108
views
gate2019-ec
numerical-answers
communications
amplitude-modulation
0
votes
0
answers
11
GATE ECE 2019 | Question: 55
In the circuit shown, $V_{1}=0$ and $V_{2}=V_{dd}.$ The other relevant parameters are mentioned in the figure. Ignoring the effect of channel length modulation and the body effect, the value of $I_{out}$ is _________ $mA$ (rounded off to $1$ decimal place).
Arjun
asked
in
Communications
Feb 12, 2019
by
Arjun
6.0k
points
46
views
gate2019-ec
numerical-answers
communications
modulations
0
votes
0
answers
12
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
Milicevic3306
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in
Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
70
views
gate2016-ec-3
digital-communications
communications
0
votes
0
answers
13
GATE ECE 2016 Set 2 | Question: 22
A speech signal is sampled at $8$ $kHz$ and encoded into $PCM$ format using $8$ bits/sample. The $PCM$ data is transmitted through a baseband channel via $4$-level $PAM$. The minimum bandwidth (in $kHz$) required for transmission is _________
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in
Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
42
views
gate2016-ec-2
numerical-answers
digital-communications
pulse-code-modulation-systems
communications
0
votes
0
answers
14
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 ________
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Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
565
views
gate2016-ec-2
numerical-answers
autocorrelation-and-power-spectral-density
communications
0
votes
0
answers
15
GATE ECE 2016 Set 2 | Question: 49
An ideal band-pass channel $500 \: Hz –2000 \:Hz$ 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 __________
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Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
80
views
gate2016-ec-2
numerical-answers
communications
0
votes
0
answers
16
GATE ECE 2016 Set 2 | Question: 50
Consider a random process $X\left ( t \right )=3V(t)-8,$ where $V(t)$ is a zero mean stationary random process with autocorrelation $R_{v}\left ( \tau \right )=4e^{-5\mid \tau \mid}.$ The power in $X(t)$ is _________
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in
Communications
Mar 28, 2018
by
Milicevic3306
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points
53
views
gate2016-ec-2
numerical-answers
communications
autocorrelation-and-power-spectral-density
0
votes
0
answers
17
GATE ECE 2016 Set 2 | Question: 51
A binary communication system makes use of the symbols zero and one . There are channel errors. Consider the following events: ... in bits that you obtain when you learn which symbol has been received (while you know that a zero has been transmitted) is _________
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Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
51
views
gate2016-ec-2
numerical-answers
communications
0
votes
0
answers
18
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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Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
76
views
gate2016-ec-1
numerical-answers
communications
modulation
0
votes
0
answers
19
GATE ECE 2016 Set 1 | Question: 24
Concentric spherical shells of radii $2$m, $4$m, and $8$ m carry uniform surface charge densities of $20 \: nC/m^2$, $ – 4 \: nC/m^2$ and $\rho_s$ respectively. The value of $\rho_s$ ($nC/m^2$) required to ensure that the electric flux density $\overrightarrow D$ = $\overrightarrow 0$ at radius $10$ m is ________
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Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
45
views
gate2016-ec-1
numerical-answers
to-be-tagged
communications
0
votes
0
answers
20
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
341
views
gate2016-ec-1
numerical-answers
digital-communications
communications
0
votes
0
answers
21
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
85
views
gate2015-ec-3
communications
gaussian-minimum-shift-keying
0
votes
0
answers
22
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
points
119
views
gate2015-ec-3
communications
pseudo-random-number
0
votes
0
answers
23
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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in
Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
71
views
gate2015-ec-2
digital-communications
communications
0
votes
0
answers
24
GATE ECE 2015 Set 1 | Question: 50
The transmitted signal in a GSM system is of $200$ kHz bandwidth and $8$ users share a common bandwidth using TDMA. If at a given time $12$ users are talking in a cell, the total bandwidth of the signal received by the base station of the cell will be at least (in kHz) ___________.
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in
Communications
Mar 28, 2018
by
Milicevic3306
15.8k
points
44
views
gate2015-ec-1
numerical-answers
communications
time-divison-multiple-accessamplifiers
0
votes
0
answers
25
GATE ECE 2014 Set 4 | Question: 23
In a double side-band (DSB) full carrier AM transmission system, if the modulation index is doubled, then the ratio of total sideband power to the carrier power increases by a factor of __________.
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Communications
Mar 26, 2018
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Milicevic3306
15.8k
points
39
views
gate2014-ec-4
numerical-answers
communications
amplitude-modulation
0
votes
0
answers
26
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
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Milicevic3306
15.8k
points
57
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gate2014-ec-4
numerical-answers
communications
phase-shift-keying
0
votes
0
answers
27
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 _______.
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in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
77
views
gate2014-ec-3
numerical-answers
digital-communications
communications
0
votes
0
answers
28
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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Milicevic3306
15.8k
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59
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gate2014-ec-3
digital-communications
frequency-modulation
communications
0
votes
0
answers
29
GATE ECE 2014 Set 3 | Question: 49
Let $X(t)$ be a wide sense stationary $(WSS)$ random process with power spectral density $S_{X}(f).$ If $Y(t)$ is the process defined as $Y(t)= X(2t-1)$, the power spectral density $S_{Y}( f )$ ... $S_{Y}( f )= \frac{1}{2}S_{X}\left ( \frac{f}{2} \right )e^{-j2\pi f }$
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in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
42
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gate2014-ec-3
communications
autocorrelation-and-power-spectral-density
0
votes
0
answers
30
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 ___________.
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in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
74
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gate2014-ec-3
numerical-answers
autocorrelation-and-power-spectral-density
communications
0
votes
0
answers
31
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 ______.
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in
Communications
Mar 26, 2018
by
Milicevic3306
15.8k
points
79
views
gate2014-ec-3
numerical-answers
digital-communications
pulse-code-modulation-systems
communications
0
votes
0
answers
32
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 ___________.
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Communications
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by
Milicevic3306
15.8k
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79
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gate2014-ec-2
numerical-answers
communications
amplitude-modulation
0
votes
0
answers
33
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
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Milicevic3306
15.8k
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63
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gate2014-ec-2
communications
timing-diagram
0
votes
0
answers
34
GATE ECE 2014 Set 2 | Question: 44
The input-output relationship of a causal stable LTI system is given as $y[n] = \alpha \: y[n-1] + \beta \: x[n]$. If the impulse response $h[n]$ of this system satisfies the condition $\sum_{n=0}^{\infty}h[n]= 2$, the relationship between $\alpha$ and $\beta$ is $\alpha = 1-\beta /2$ $\alpha = 1+\beta /2$ $\alpha = 2\beta$ $\alpha = -2\beta$
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39
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gate2014-ec-2
communications
linear-time-invariant-systems
0
votes
0
answers
35
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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Milicevic3306
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59
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gate2014-ec-2
communications
frequency-shift-keying
0
votes
0
answers
36
GATE ECE 2014 Set 2 | Question: 51
The power spectral density of a real stationary random process $X(t)$ is given by $ S_X (f) = \begin{cases} \frac{1}{W}, & \mid f \mid \leq W \\ 0, & \mid f \mid > W \end{cases}$ The value of the expectation $E \left [ \pi X(t)X\left ( t-\frac{1}{4W} \right ) \right ]$ is __________.
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45
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gate2014-ec-2
numerical-answers
communications
autocorrelation-and-power-spectral-density
0
votes
0
answers
37
GATE ECE 2014 Set 1 | Question: 22
In a code-division multiple access $(\text{CDMA})$ system with $N = 8$ chips, the maximum number of users who can be assigned mutually orthogonal signature sequences is ________.
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Communications
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52
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gate2014-ec-1
numerical-answers
code-division-multiple-access
communications
0
votes
0
answers
38
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 _____.
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61
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gate2014-ec-1
numerical-answers
communications
digital-modulation
basic-electrical-rhythm
0
votes
0
answers
39
GATE ECE 2014 Set 1 | Question: 52
A fair coin is tossed repeatedly until a ‘Head’ appears for the first time. Let $L$ be the number of tosses to get this first ‘Head’. The entropy $H(L)$ in bits is _____.
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44
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gate2014-ec-1
numerical-answers
entropy
communications
0
votes
0
answers
40
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} $
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communications
digital-modulation
basic-electrical-rhythm
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