This set of Wireless & Mobile Communications Multiple Choice Questions & Answers (MCQs) focuses on “Introduction to Multiple Access”.
1. Multiple access schemes are used to allow ________ mobile users to share simultaneously a finite amount of radio spectrum.
a) Many
b) One
c) Two
d) Ten-Fifteen
View Answer
Explanation: Multiple access schemes are used to allow many mobile users to share simultaneously a finite amount of radio spectrum. The sharing of spectrum is required to achieve high capacity by simultaneously allocating the available bandwidth to multiple users.
2. The technique that makes possible the task of listening and talking in communication system is called ________
a) Simplexing
b) Duplexing
c) Modulating
d) Multiple access technique
View Answer
Explanation: In conventional telephone systems, it is possible to talk and listen simultaneously. This effect is called duplexing and is generally required in wireless telephone systems.
3. Frequency division duplexing provides ________ distinct bands of frequencies for _________ user.
a) Two, two
b) One, two
c) Two, one
d) Two, many
View Answer
Explanation: Frequency division duplexing (FDD) provides two distinct bands of frequencies for every user. In FDD, any duplex channel actually consists of two simplex channels.
4. The forward band in FDD provides traffic from the mobile to base station.
a) True
b) False
View Answer
Explanation: The forward band in FDD provides traffic from the base station to the mobile. The reverse band provides traffic from the mobile to the base station.
5. The frequency separation between each forward and reverse channel changes throughout the system.
a) True
b) False
View Answer
Explanation:The frequency separation between each forward and reverse channel is constant throughout the system. It is regardless of the particular channel being used. A device called a duplexer is used inside each subscriber unit and base station to allow simultaneous bidirectional radio transmission.
6. Time division duplexing uses ________ to provide both a forward and reverse link.
a) Frequency
b) Time
c) Time and frequency
d) Cell spacing
View Answer
Explanation: Time division duplexing (TDD) uses time instead of frequency to provide both a forward and reverse link. In TDD, multiple users share a single radio channel by taking turns in the time domain.
7. TDD is effective for _________
a) Fixed wireless access and users are stationary
b) Dynamic wireless access and users are stationary
c) Fixed wireless access and users are moving
d) Dynamic wireless access and users are moving
View Answer
Explanation: TDD is effective for fixed wireless access when all users are stationary. This makes the propagation delay does not vary in time among the users. Because of rigid timing required for time slotting, TDD generally is limited to cordless phone or short range potable access.
8. In wideband systems, the transmission bandwidth of a single channel _________ coherence bandwidth of the channel.
a) Equal to
b) Not related to
c) Larger than
d) Smaller than
View Answer
Explanation: In wideband systems, the transmission bandwidth of a single channel is much larger than the coherence bandwidth of the channel. Thus, multipath fading does not greatly vary the received signal power within a wideband channel.
9. In narrowband system, the channels are usually operated using TDD.
a) True
b) False
View Answer
Explanation: In narrowband system, channels are usually operated using FDD. To minimize interference between forward and reverse links on each channel, the frequency separation is made as great as possible within the frequency spectrum.
10. Narrowband FDMA allows users to share the same radio channel allocating a unique time slot to each user.
a) True
b) False
View Answer
Explanation: In narrowband FDMA, a user is assigned a particular channel which is not shared by other users in the vicinity. However narrowband TDMA allows the users to share the same radio channel allocating a unique time slot to each user.
Sanfoundry Global Education & Learning Series – Wireless & Mobile Communications.
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