## Data Transmission MCQ

Data Transmission MCQ, Multiple Choice Questions on Data Transmission, Phase Shifting Key MCQ, BPSK MCQ, ASK MCQ, BFSK MCQ, DPSK MCQ, Engineering MCQ, Analog Communication MCQ, Digital Communication MCQ, Data Transmission MCQ

### Multiple-Choice Questions

Q.1. Which of the following gives maximum probability of error?

- ASK
- BFSK
- BPSK
- DPSK

**Answer: **ASK

Q.2. Which of the following gives minimum probability of error?

- ASK
- BFSK
- BPSK
- DPSK

**Answer:** BPSK

Q.3. The output S/N ratio of a matched filter, fed at its input by a rectangular pulse of amplitude A and duration T, is given as (assume τ as noise power spectral density)

- 2A
^{2}T/τ - A.T
- A/T
- A/τ

**Answer: **2A^{2}T/τ

Q.4. Binary data is transmitted using BPSK signalling scheme with S_{1}(t)=A\cos \omega _{c}t, S_{2}(t)=-A\cos \omega _{c}t, 0\leq t\leq T_{b} where bit duration *T _{b}* is equal to 0.2 ns. The carrier frequency

*f*= 5

_{c}*f*. The carrier amplitude at the receiver input is 1 mV and the power spectral density of the AWGN at the input is 10

_{b}^{-11}W/Hz. The probability of error for an optimum filter will be

- erfc\sqrt{5.5}
- \frac{1}{2}erfc\sqrt{5}
- erf\sqrt{5.5}
- \frac{1}{2}erf\sqrt{5}

**Answer: **\frac{1}{2}erfc\sqrt{5}

Q.5. In a BPSK system, the transmitted binary data rate = 2.5 Mbits/s, power spectral density of zero mean AWGN γ/2 = 10^{-2} W/Hz and the amplitude of the received signal in the absence of noise is 1 µV. The average probability of symbol error will be

*erf*(6.6)- 1/2
*erf*(6.6) *erfc*(2.45)- 1/2
*erfc*(2.45)

**Answer: ***erfc* (2.45)

Q.6. The input to a matched filter is given by

S(t)=\left\{\begin{matrix}10sin(2\pi 10^{6}t), & 0 \leq t\leq 10^{-4}s\\0, & otherwise \\\end{matrix}\right.The peak amplitude of the filter output is

- 10 V
- 5 V
- 10 mV
- 5 mV

**Answer: **10 V

Q.7. The impulse response of a matched filter to a data pulse tg(t) with 0 ≤ t ≤ T is

- \delta ^{\bigotimes }(t)
- g ^{\bigotimes }(t)
- g ^{\bigotimes }(t-T)
- g ^{\bigotimes }(T-t)

**Answer: **g ^{\bigotimes }(T-t)

Q.8. The main circuit used in a DPSK modulator is

- NOR gate
- NAND gate
- XNOR gate
- OR gate

**Answer: **XNOR gate

Q.9. The correlation receiver consists of

- a multiplier and an integrator
- an adder and an integrator
- a multiplier and a differentiation
- an adder and a differentiator

**Answer: **a multiplier and an integrator

Q.10. Among BPSK, QPSK and DPSK for same Pe, the QPSK requires

- maximum power
- minimum power
- same power
- power in between BPSK and DPSK

**Answer: **minimum power

Q.11. ASK, FSK and PSK are examples of following encoding:

- Digital to analog
- Digital to digital
- Analog to analog
- Analog to digital

**Answer: **Digital to digital

Q.12. If the baud rate for a QPSK system is 100, then the bit rate is

- 100
- 200
- 400
- 800

**Answer: **400

Q.13. The input to a matched filter is given by

S(t)=\left\{\begin{matrix}10sin(2\pi 10^{6}), & 0 \leq t\leq 10^{-4}\\0, & otherwise \\\end{matrix}\right.The peak amplitude of the filter output is

- 10 V
- 5 V
- 10 mV
- 5 mV

**Answer: **5 mV

Q.14. In a digital communication system employing FSK, the 0 and 1 bits are represented by sine waves of 10 kHz and 25 kHz respectively. These waveforms will be orthogonal for a bit interval of

- 45 µs
- 200 µs
- 50 µs
- 250 µs

**Answer: **200 µs

Q.15. If a binary PSK modulation is used for transmission, the required minimum bandwidth is 9600 Hz. To reduced the transmission bandwidth to 2400 Hz, the modulation scheme to be adopted should be

- quadrature phase-shift keying
- minimum shift keying
- 16-ary quadrature amplitude modulation
- 8-ary PSK

**Answer: **16-ary quadrature amplitude modulation

Q.16. For a given data rate, the bandwidth *β _{p}* of a BPSK signal and the bandwidth βo of the OOK signal are related as

- β
_{p}= β_{0}/2 - β
_{p}= 2 β_{0} - β
_{p}= β_{0}/4 - β
_{p}= β_{0}

**Answer: **β_{p} = 2 β_{0}

Q.17. For a bit-rate of 8 kbps, the best possible values of the transmitted frequencies in a coherent binary FSK system are

- 16 kHz and 20 kHz
- 20 kHz and 32 kHz
- 20 kHz and 40 kHz
- 32 kHz an 40 kHz

**Answer: **32 kHz an 40 kHz

Q.18. For a given probability of error, binary coherent FSK is inferior to binary coherent PSK by

- 6 dB
- 3 dB
- 2 dB
- 0 dB

**Answer: **3 dB

Q.19. If S represents the carrier synchronization at the receiver and ρ represents the bandwidth efficiency, then the correct statement for the coherent binary PSK is

- ρ = 0.5, S is required
- ρ = 1, S is required
- ρ = 0.5, S is not required
- ρ = 1, S is not required

**Answer: **ρ = 0.5, S is required

Q.20. A source produces binary data at the rate of 10 kbps. The binary symbols are represented as shown in the figure.

The source output is transmitted using two modulation schemes, namely binary PSK and quadrature PSK. Let B1 and 82 be the bandwidth requirements of BPSK and QPSK respectively. Assuming that the bandwidth of the above rectangular pulse is 10 kHz, B1 are and B2

- 20 kHz, 20 kHz
- 10 kHz, 20 kHz
- 20 kHz, 10 kHz
- 10 kHz, 10 kHz

**Answer: **20 kHz, 10 kHz

Q.21. Choose the correct one from among the alternatives A, B, C, D after matchling an item from Group 1 with the most appropriate item in Group 2.

Group 1 | Group 2 |

1. FM | P. Slope Overload |

2. DM | Q . μ .-law |

3. PSK | R . Envelope-detector |

4. PCM | T. Hilbert transform |

S. Capture effect | |

U. Matched filter |

- l -T, 2-P, 3-U, 4-S
- 1-S, 2-U, 3-P, 4-T
- 1-S, 2-P, 3-U, 4-Q
- 1-U, 2-R, 3-S, 4-Q

**Answer: **1-S, 2-P, 3-U, 4-Q

Q.22. Two 4-ary signal constellations are shown. It is given that ϕ1 and ϕ2 constitute an orthonormal basis for the two constellations. Assume that the four symbols in both the constellations are equiprobable. Let N_{0}/2 denote the power spectral density of white Gaussian noise.

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

- 4a
^{2} - 4
- 2
- 8

**Answer:** 4

Q.23. If the constellations of above examples are used for digital communication over AWGN channel, then which of the following statements is true?

- Probability of symbol error for constellation 1 is lower.
- Probability of symbol error for constellation 1 is higher.
- Probability of symbol error is equal for both the constellations.
- The value of N
_{0}will determine which of the two constellations has a lower probability of symbol error.

**Answer: **Probability of symbol error for constellation 1 is lower.

Q.24. Which of the following statements about the matched filter in a communication receiver are correct?

- Its impulse response depends on the signal shape.
- It maximizes the SNR at the detection instant.
- It produces ISI.
- It may produce phase error if synchronization is improper.

Select the correct answer from the codes given below:

- 1 and 4 only
- 1 and 2 only
- 2, 3 and 4
- 1, 2 and 4

**Answer: **1 and 2 only

Q.25. In DPSK, no synchronous carrier is needed at the receiver.

- True
- False

**Answer: **True

Q.26. In BFSK, no synchronous carrier is needed at the receiver.

- True
- False

**Answer: **False

Q.27. Probability of error in DPSK in less than BPSK.

- True
- False

**Answer: **False

28. Amplitude shift keying is also known as on-off keying.

- True
- False

**Answer: **True

29. Correlator is a coherent system of signal reception.

- True
- False

**Answer: **True