Frequency Division Multiple Access (FDMA)

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Questions and Answers

What is the purpose of frequency division duplex (FDD) in cellular networks?

  • To establish a duplex channel for secure communication
  • To regulate the basic frequency allocation scheme for GSM networks
  • To allocate frequencies to transmission channels according to frequency division multiplexing
  • To allow for simultaneous transmission in both directions using different frequencies (correct)

What is the main function of frequency division multiple access (FDMA)?

  • To establish a duplex channel for secure communication
  • To regulate the basic frequency allocation scheme for GSM networks
  • To allocate frequencies to transmission channels according to frequency division multiplexing (correct)
  • To listen into the medium to know the frequencies in advance

What distinguishes uplink and downlink frequencies in the context of cellular networks?

  • Uplink frequencies use FDD, and downlink frequencies use FDMA
  • Uplink frequencies are fixed, and downlink frequencies are regulated by national authorities
  • Uplink frequencies are from mobile station to base station, and downlink frequencies are from base station to mobile station (correct)
  • Uplink frequencies are for listening into the medium, and downlink frequencies allow for simultaneous transmission

What is the significance of knowing the frequencies in advance in cellular networks?

<p>To prevent interference and ensure efficient communication (D)</p> Signup and view all the answers

In a cellular network based on GSM standard for 900 MHz, what is the basic frequency allocation scheme for uplinks?

<p>Between 890.2 and 915 MHz (D)</p> Signup and view all the answers

What role does frequency division multiplexing (FDM) play in cellular networks?

<p>It is used for simultaneous access to the medium by base station and mobile station (C)</p> Signup and view all the answers

What is the main characteristic of time division multiple access (TDMA)?

<p>It allocates certain time slots for communication (D)</p> Signup and view all the answers

What is the typical solution for wireless phone systems using Fixed TDM?

<p>Allocating fixed bandwidth and using a fixed pattern for time slots (B)</p> Signup and view all the answers

What is the term used to describe assigning different slots for uplink and downlink using the same frequency in TDM?

<p>Time division duplex (TDD) (A)</p> Signup and view all the answers

What is the main characteristic of Classical Aloha?

<p>No coordination among the users, with no collision detection and no central arbiter (A)</p> Signup and view all the answers

What is the main improvement provided by Slotted Aloha compared to Classical Aloha?

<p>Introduction of time slots for synchronized transmissions (B)</p> Signup and view all the answers

What is the main feature of non-persistent CSMA?

<p>Stations sense the carrier and start sending immediately if the medium is idle (D)</p> Signup and view all the answers

What does p-persistent CSMA involve?

<p>Sensing the medium and transmitting with a probability p (A)</p> Signup and view all the answers

What does SDMA (space division multiple access) involve?

<p>Assigning an optimal base station to a mobile phone user based on different quality (D)</p> Signup and view all the answers

What is the main drawback of Classical Aloha compared to Slotted Aloha?

<p>Data retransmission is not supported after collision (B)</p> Signup and view all the answers

What type of multiple access involves allocating separated space to users in wireless networks?

<p>Space division multiple access (SDMA) (A)</p> Signup and view all the answers

What is the purpose of frequency division duplex (FDD) in cellular networks?

<p>To allow for simultaneous transmission in both directions by using different frequencies for uplink and downlink.</p> Signup and view all the answers

What is the main function of frequency division multiple access (FDMA)?

<p>Allocating frequencies to transmission channels according to frequency division multiplexing (FDM).</p> Signup and view all the answers

What distinguishes uplink and downlink frequencies in the context of cellular networks?

<p>Uplink frequencies are from mobile station to base station, and downlink frequencies are from base station to mobile station.</p> Signup and view all the answers

What type of multiple access involves allocating separated space to users in wireless networks?

<p>Space Division Multiple Access (SDMA).</p> Signup and view all the answers

What does frequency division multiplexing (FDM) allow for in cellular networks?

<p>Simultaneous access to the medium by base station and mobile station.</p> Signup and view all the answers

What is the significance of knowing the frequencies in advance in cellular networks?

<p>It allows for establishing a duplex channel, i.e., a channel that allows for simultaneous transmission in both directions.</p> Signup and view all the answers

What is the main difference between Fixed TDM and TDMA in terms of flexibility?

<p>Fixed TDM results in a fixed bandwidth, while TDMA offers a much more flexible scheme by allocating certain time slots for communication.</p> Signup and view all the answers

What is the term used to describe the allocation of different time slots for uplink and downlink using the same frequency in TDM?

<p>Time division duplex (TDD)</p> Signup and view all the answers

What is the main drawback of Classical Aloha compared to Slotted Aloha?

<p>No coordination among the users and lack of collision detection in Classical Aloha, leading to a lot of collisions.</p> Signup and view all the answers

What is the main function of frequency division multiple access (FDMA)?

<p>FDMA involves allocating different frequency bands to multiple users for simultaneous communication.</p> Signup and view all the answers

What type of multiple access involves allocating separated space to users in wireless networks?

<p>SDMA (space division multiple access)</p> Signup and view all the answers

What is the main characteristic of Classical Aloha?

<p>Lack of coordination among users and no collision detection</p> Signup and view all the answers

What is the main feature of non-persistent CSMA?

<p>Stations sense the carrier and start sending immediately if the medium is idle, or pause a random amount of time before sensing the medium again if it is busy.</p> Signup and view all the answers

What is the main purpose of frequency division duplex (FDD) in cellular networks?

<p>FDD allows simultaneous transmission and reception on different frequencies, enabling full-duplex communication.</p> Signup and view all the answers

What distinguishes slotted Aloha from classical Aloha?

<p>Slotted Aloha introduces time slots and synchronized transmissions, reducing collisions compared to the lack of coordination and collision detection in Classical Aloha.</p> Signup and view all the answers

What is the main characteristic of time division multiple access (TDMA)?

<p>TDMA allocates certain time slots for communication, achieving synchronization between sender and receiver in the time domain.</p> Signup and view all the answers

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