Digital Communication MCQ Questions & Answers

51

Four independent messages have bandwidths of 100 Hz, 100 Hz, 200 Hz, and 400 Hz, respectively. Each is sampled at the Nyquist rate, and the samples are Time Division Multiplexed (TDM) and transmitted. The transmitted sample rate (in Hz) is

A) 1600 B) 800 C) 400 D) 200

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Answer & Solution

Answer: Option B

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52

In a PCM system with uniform quantization, increasing the number of bits from 8 to 9 will reduce the quantization noise power by a factor of

A) 9 B) 8 C) 4 D) 2

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Answer & Solution

Answer: Option C

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53

The line code that has zero dc component for pulse transmission of random binary data is

A) Non-return to zero (NRZ) B) Return to zero (RZ) C) Alternate mark inversion (AMI) D) None of the above

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Answer & Solution

Answer: Option C

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54

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 symbols per second is

A) 1750 B) 2625 C) 4000 D) 5250

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Answer & Solution

Answer: Option C

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55

An analog signal is band-limited to 4 kHz, sampled at the Nyquist rate and the samples are quantized into 4 levels. The quantized levels are assumed to be independent and equally probable. If we transmit two quantized samples per second, the information rate is

A) 1 bit/sec B) 2 bits/sec C) 3 bits/sec D) 4 bits/sec

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Answer & Solution

Answer: Option D

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56

The minimum step-size required for a Delta-Modulator operating at 32 K samples/sec to track the signal (here u(t) is the unit-step function)
x(t) = 125t(u(t) - u(t - 1)) + (250 - 125t)(u(t - 1) - u(t - 2)) so that slope-overload is avoided, would be

A) 2^-10 B) 2^-8 C) 2^-6 D) 2^-4

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Answer & Solution

Answer: Option B

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57

Consider the signal x(t) shown in the figure. Let h(t) denote the impulse response of the filter matched to x(t), with h(t) being non-zero only in the interval 0 to 4 sec. The slope of h(t) in the interval 3 < t < 4 sec is
Digital Communication mcq question image

Digital Communication mcq question image

A) $$\frac{1}{2}{\sec ^{ - 1}}$$ B) -1 sec^-1 C) $$ - \frac{1}{2}{\sec ^{ - 1}}$$ D) 1 sec^-1

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Answer & Solution

Answer: Option B

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58

Compression in PCM refers to relative compression of

A) Higher signal amplitudes B) Lower signal amplitudes C) Lower signal frequencies D) Higher signal frequencies

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Answer & Solution

Answer: Option A

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59

If S represents the carrier synchronization at the receiver and p represents the bandwidth efficiency, then the correct statement for the coherent binary PSK is

A) $$\rho = 0.5,S$$ is required B) $$\rho = 1.0,S$$ is required C) $$\rho = 0.5,S$$ is not required D) $$\rho = 1.0,S$$ is not required

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Answer & Solution

Answer: Option A

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60

In a digital communication system, transmissions of successive bits through a noisy channel are assumed to be independent events with error probability p. The probability of at most one error in the transmission of an 8-bit sequence is

A) $$\frac{{7\left( {1 - p} \right)}}{8}+\frac{{7\left( {1 - p} \right)}}{{8 + \frac{p}{8}}}$$ B) (1 - p)⁸ + 8p(t - p)⁷ C) (1 - p)⁸ + (1 - p)⁷ D) (1 - p)⁸ + p(1 - p)⁷

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Answer & Solution

Answer: Option B

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Digital Communication MCQ Questions & Answers | ECE