MCQOPTIONS
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MCQOPTIONS
This section includes 84 Mcqs, each offering curated multiple-choice questions to sharpen your Wireless Mobile Communications knowledge and support exam preparation. Choose a topic below to get started.
| 51. |
Directions: The item consists of two statements, one labeled as the ‘Assertion (A)’ and the other as ‘Reason (R)’.You are to examine these two statements carefully and select the answers to the item using the codes given below:Assertion (A): PCM/FM systems transmit PCM pulses by modulating a high-frequency carrier and hence occupy large bandwidth and eliminate distortion.Reason (R): Large bandwidth ensures SNR trade-off and hence distortionless transmission is ensured. |
| A. | Both A and R individually true and R is the correct explanation of A |
| B. | Both A and R are individually true but R is not the correct explanation of A |
| C. | A is true but R is false |
| D. | A is false but R is true |
| Answer» B. Both A and R are individually true but R is not the correct explanation of A | |
| 52. |
A TDM link has 24 signals and each channel is sampled 8000 times/sec. Each sample is represented by 8 binary bits and it contains an additional bit for synchronization. The total bit rate made from the TDM link is |
| A. | 1600 K bits/sec |
| B. | 1728 K bits/sec |
| C. | 1826 K bits/sec |
| D. | 2056 K bits/sec |
| Answer» C. 1826 K bits/sec | |
| 53. |
1 Mbps BPSK receiver detects waveform S1(t) =Acosω0t or s2(t) = -Acosω0t with a matched filter. If A= 1 mV, then the average bit error probability assuming single-sided noise power expected density N0 = 10-11 w/hz is nearly |
| A. | Q (0.63) |
| B. | Q (0.16) |
| C. | \(Q\sqrt {0.1} \) |
| D. | \(Q\sqrt {0.3} \) |
| Answer» D. \(Q\sqrt {0.3} \) | |
| 54. |
Directions: It consists of two statements, one labeled as the ‘Statement (I)’ and the other as ‘Statement (II). Examine these two statements carefully and select the answer using the codes given below:Statement (I): High-frequency DSB is obtained in practice using two AM modulators arranged in a balanced configuration.Statement (II): Perfect square-law devices are difficult to design. |
| A. | Both Statement (I) and Statement (II) are individually true and Statement (II) is the correct explanation of Statement (I) |
| B. | Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I) |
| C. | Statement (I) is true but Statement (II) is false |
| D. | Statement (I) is false but Statement (II) is true |
| Answer» B. Both Statement (I) and Statement (II) are individually true but Statement (II) is not the correct explanation of Statement (I) | |
| 55. |
If the desired transmission bit rate for a coherent binary FSK system is 4 Kbits / sec, the best possible interval between the carriers is |
| A. | 0.25 mS |
| B. | 0.5 mS |
| C. | 1 mS |
| D. | 5 mS |
| Answer» C. 1 mS | |
| 56. |
In the digital T1 carrier PCM telephony, the data rate is: |
| A. | 1.544 Mbps |
| B. | 1.866 Mbps |
| C. | 2.176 Mbps |
| D. | 8.000 Mbps |
| Answer» B. 1.866 Mbps | |
| 57. |
Eye Diagram gives an idea of |
| A. | Modulation scheme |
| B. | Cock jitter |
| C. | SNR |
| D. | All of the above |
| Answer» E. | |
| 58. |
Consider the following statements for multiple access system in a satellite earth station:1. Access to the same repeater sub-systems and the same RF channel is possible.2. Frequency division multiple access is used.3. Several carriers are not amplified by the same TWT.Which of the above statements are correct? |
| A. | 2 and 3 only |
| B. | 1 and 3 only |
| C. | 1 and 2 only |
| D. | 1, 2 and 3 |
| Answer» B. 1 and 3 only | |
| 59. |
Four voice signals, each limited to 4 kHz and sampled at Nyquist rate, are converted into binary PCM signal using 256 quantization levels. The bit transmission rate for the time-division multiplexing signal will be |
| A. | 8 kbps |
| B. | 64 kbps |
| C. | 256 kbps |
| D. | 5126 kbps |
| Answer» D. 5126 kbps | |
| 60. |
Output SNR of a n bit PCM was found to be 30 dB, desired SNR is 42 dB. To achieve desired SNR by increasing the number of quantization levels, then new levels will be |
| A. | 128 |
| B. | 512 |
| C. | 2018 |
| D. | 1024 |
| Answer» B. 512 | |
| 61. |
Converting an analog signal to a digital signal is done by Sampling and |
| A. | Companding |
| B. | Mixing |
| C. | Quantizing |
| D. | Pre-emphasis |
| Answer» D. Pre-emphasis | |
| 62. |
Four voice signals, each limited to 4 kHz and sampled at Nyquist rate, are converted into binary PCM signal using 256 quantization levels. The bit transmission rate for the time-division multiplexed signal will be |
| A. | 8 kbps |
| B. | 64 kbps |
| C. | 256 kbps |
| D. | 512 kbps |
| Answer» D. 512 kbps | |
| 63. |
In PCM, if the number of bits are changed from n to (n + 8), then SNR changes by: |
| A. | 8 dB |
| B. | 48 dB |
| C. | 16 dB |
| D. | 10 dB |
| Answer» C. 16 dB | |
| 64. |
In a PCM system, non-uniform quantization leads to |
| A. | increased quantizer noise |
| B. | simplification of the quantization process |
| C. | higher average SNR |
| D. | increased bandwidth |
| Answer» D. increased bandwidth | |
| 65. |
In a PCM system each quantization level is encode into 8 bits. The signal to quantization noise ratio is |
| A. | 12 dB |
| B. | 48 dB |
| C. | 64 dB |
| D. | 256 dB |
| Answer» C. 64 dB | |
| 66. |
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 N0/2. Binary signaling, with 0 ↦ p(t) and 1 ↦ q(t), is used for the transmission, along with an optimal receiver that minimizes the bit-error probability. Let φ1 (t), φ2(t) form an orthonormal signal set. If we choose p(t) = φ1 (t) and q(t) = −φ1 (t), we would obtain a certain bit-error probability Pb. If we keep p(t) = φ1(t), but take \(q\left( t \right) = \sqrt E\) φ2 (t) for what value of E would we obtain the same bit-error probability Pb? |
| A. | 0 |
| B. | 1 |
| C. | 2 |
| D. | 3 |
| Answer» E. | |
| 67. |
PSK and FSK are which type of modulation? |
| A. | Analog Modulation |
| B. | Digital Modulation |
| C. | Both Analog Modulation & Digital Modulation |
| D. | None of these |
| Answer» C. Both Analog Modulation & Digital Modulation | |
| 68. |
In which modulation technique does the phase of the carrier signal is changed by varying the sine and cosine inputs at a particular time. |
| A. | Frequency modulation |
| B. | Phase shift key modulation |
| C. | Analog modulation |
| D. | Pulse code modulation |
| Answer» C. Analog modulation | |
| 69. |
An analog voltage is in the range of 0 to 8 V is divided in eight equal intervals for conversion to 3-bit digital output. The maximum quantization error is |
| A. | 0 V |
| B. | 0.5 V |
| C. | 1 V |
| D. | 2 V |
| Answer» C. 1 V | |
| 70. |
A 1 MHz pulse train with 90% duty cycle shall have an ON-time of |
| A. | 900 ns |
| B. | 100 ns |
| C. | 50 μs |
| D. | 0.5 μs |
| Answer» B. 100 ns | |
| 71. |
Indicate which of the following pulse modulation scheme is analog |
| A. | PCM |
| B. | Differential PCM |
| C. | Delta modulation |
| D. | PWM |
| Answer» E. | |
| 72. |
Following type of multiplexing cannot be used for analog signalling? |
| A. | FDM |
| B. | TDM |
| C. | WDM |
| D. | None of these |
| Answer» C. WDM | |
| 73. |
BRI in ISDN has which of the following channels? |
| A. | 30B + 1D |
| B. | 2B + 1D |
| C. | 30B + 2D |
| D. | Only 2 B Channels |
| Answer» C. 30B + 2D | |
| 74. |
WHICH_OF_THE_FOLLOWING_IS_DEFINED_AS_THE_RANGE_OF_FREQUENCIES_OVER_WHICH_THE_SIGNAL_HAS_A_NON_ZERO_POWER_SPECTRAL_DENSITY??$ |
| A. | Null to null bandwidth |
| B. | Half power bandwidth |
| C. | 3 dB bandwidth |
| D. | Absolute bandwidth |
| Answer» E. | |
| 75. |
Half power bandwidth is also called ______$ |
| A. | Absolute bandwidth |
| B. | Null to null bandwidth |
| C. | 3 dB bandwidth |
| D. | Zero dB bandwidth |
| Answer» D. Zero dB bandwidth | |
| 76. |
_______ is equal to width of main spectral lobe.$ |
| A. | Null to null bandwidth |
| B. | Half power bandwidth |
| C. | 3 dB bandwidth |
| D. | Absolute bandwidth |
| Answer» B. Half power bandwidth | |
| 77. |
Which of the following is the ratio of the throughput data rate per Hertz? |
| A. | Bandwidth efficiency |
| B. | Spectral density |
| C. | Power efficiency |
| D. | Power density |
| Answer» B. Spectral density | |
| 78. |
Increasing the data rate implies the increase in pulse width of digital symbol. State whether True or False. |
| A. | True |
| B. | False |
| Answer» C. | |
| 79. |
Which of the following is the ratio of signal energy per bit to noise power spectral density? |
| A. | Bandwidth efficiency |
| B. | Spectral density |
| C. | Power efficiency |
| D. | Power density |
| Answer» D. Power density | |
| 80. |
In digital communication system, in order to increase noise immunity, it is necessary to increase _____. |
| A. | Signal power |
| B. | Signal amplitude |
| C. | Signal frequency |
| D. | Signal magnitude |
| Answer» B. Signal amplitude | |
| 81. |
The performance of modulation scheme is not measured in terms of _____ |
| A. | Power efficiency |
| B. | Bandwidth efficiency |
| C. | Cost and complexity |
| D. | Transmitted power |
| Answer» E. | |
| 82. |
A desirable modulation scheme provides ____ bit error rates at _____ received signal to noise ratios. |
| A. | Low, low |
| B. | Low, high |
| C. | High, high |
| D. | High, low |
| Answer» B. Low, high | |
| 83. |
Which of the following is not an advantage of digital modulation? |
| A. | Greater noise immunity |
| B. | Greater security |
| C. | Easier multiplexing |
| D. | Less bandwidth requirement |
| Answer» E. | |
| 84. |
Modern mobile communication systems use analog modulation techniques. State whether True or False. |
| A. | True |
| B. | False |
| Answer» C. | |