What type of multiplexing is widely used in cellphones? - Avionics MCQ

Aeronautical & Aerospace Engineering : Avionics - Quiz(MCQ)

What type of multiplexing is widely used in cellphones?

A)

Spatial multiplexing

B)

Time division multiplexing

C)

Frequency division multiplexing

D)

Code division multiplexing

Correct Answer : Code division multiplexing

Explanation : Another form of multiple accesses is known as code-division multiple access (CDMA). It is widely used in cell phone systems to allow many cell phone subscribers to use a common bandwidth at the same time. This system uses special codes assigned to each user that can be identified. CDMA uses a technique called spread spectrum to make this type of multiplexing possible.

Recently Updated in Avionics Questions

A special PCM system uses 16 channels of data, one whose purpose is an identification (ID) and synchronization. The sampling rate is 3.5 kHz. The word length is 6 bits. Find the serial data rate.

A)

451kHz

B)

336kHz

C)

326kHz

D)

152kHz

Correct Answer : Option (B) : 336kHz

Explaination : Serial data rate = sampling rate x no. bits/frame = 3.5 kHz x 96 = 336 kHz.

Which of the following is false with respect to PCM?

A)

Reliable

B)

Inexpensive

C)

Resistant to noise

D)

Not easily recoverable

Correct Answer : Option (D) : Not easily recoverable

Explanation : When signals have been degraded because of noise, attenuation, or distortion, all the receiver has to do is to determine whether a pulse was transmitted. Amplitude, width, frequency, phase shape, and so on do not affect reception. Thus PCM signals are easily recovered and rejuvenated, no matter what the circumstances.

Which of the following statements is true with respect to PCM?

A)

Analog data is transmitted directly

B)

Analog signal is amplified before transmission

C)

The parallel binary data is converted into serial before transmission

D)

The analog signal is converted into parallel binary data before transmission

Correct Answer : Option (C) : The parallel binary data is converted into serial before transmission

Explanation : The analog signal is converted into a digital signal. Since the converted digital signal is parallel bits of data, it has to be converted to serial before it can be multiplexed and transmitted.

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