Types of MAC Protocols Quiz

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Questions and Answers

What is the main advantage of ALOHA protocol?

Trivially simple

What is the main disadvantage of ALOHA protocol?

Collisions can and will occur

Describe the performance assumption in ALOHA protocol.

Assume a Poisson arrival process to describe packet transmissions; infinite number of stations, all behave identically, independently; time between two attempts is exponentially distributed, independent for any pairs of events; all packets are of unit time length

What is required for a packet transmission to be successful in ALOHA?

It must not collide with any other packet Signup and view all the answers

What is the goal of ALOHA protocol?

Use of satellite networks Signup and view all the answers

In ALOHA, what year was it introduced and by whom?

1985 by Abrahmson et al., University of Hawaii Signup and view all the answers

What is the main problem with 1-persistent CSMA?

Guaranteed collisions when more than one station wants to transmit Signup and view all the answers

What is the main advantage of 1-persistent CSMA over pure ALOHA or slotted ALOHA?

Better efficiency despite guaranteed collisions Signup and view all the answers

What does Carrier Sense Multiple Access (CSMA) require stations to do before transmitting?

Sense the carrier to check if it is idle Signup and view all the answers

What is the crucial question addressed by CSMA protocols?

How to behave when the carrier is busy Signup and view all the answers

What is the key feature of 1-persistent CSMA when the carrier is busy?

Wait until the carrier is idle before transmitting Signup and view all the answers

Why does a CSMA scheme suffer from a principal complication related to propagation delay?

A CSMA scheme suffers from a principal complication related to propagation delay because if two stations become ready to send at nearly the same time, the second station may not detect the already started transmission of the first station due to the delay, leading to collisions. Signup and view all the answers

What is the purpose of Collision Detection in CSMA/CD?

The purpose of Collision Detection in CSMA/CD is to detect collisions immediately so that transmissions can be aborted, saving time and allowing for a new transmission attempt. Signup and view all the answers

How can collisions be detected in wired networks like Ethernet under CSMA/CD?

In wired networks like Ethernet under CSMA/CD, collisions can be detected by the sender comparing the signal current/power it sends with the signal current/power it receives. If the received power is higher than the sent power, a collision is declared. Signup and view all the answers

Why does the collision detection method using signal power not work for wireless networks?

The collision detection method using signal power does not work for wireless networks because in wireless setups, the sender cannot listen and receive at the same time due to the half-duplex constraint. Signup and view all the answers

What is the impact of a larger propagation delay on collision probability in CSMA schemes?

In CSMA schemes, a larger propagation delay leads to less synchronicity between stations, increasing the likelihood of collisions. Signup and view all the answers

How does the lack of synchronicity between stations due to propagation delay contribute to collision occurrences in CSMA schemes?

The lack of synchronicity between stations due to propagation delay in CSMA schemes increases the probability of collisions, especially when stations become ready to send at nearly the same time. Signup and view all the answers

Study Notes

ALOHA Protocol

The main advantage of ALOHA Protocol is its simplicity
The main disadvantage of ALOHA Protocol is its high probability of collisions and low efficiency
ALOHA Protocol performance assumes that packet transmissions are independent and occur randomly
For a packet transmission in ALOHA to be successful, there must be no other transmissions occurring during that packet's duration
ALOHA Protocol aims to enable multiple users to share a single communication channel without central control
ALOHA Protocol was introduced in 1970 by Norman Abramson
The main problem with 1-persistent CSMA is that it can lead to a high number of collisions in a high-contention environment
The main advantage of 1-persistent CSMA over pure ALOHA or slotted ALOHA is that it allows stations to sense the channel before transmitting to reduce the number of collisions
Carrier Sense Multiple Access (CSMA) requires stations to listen to the channel before transmitting to detect if another station is already transmitting
CSMA protocols address the question of how to manage access to a shared channel with multiple users, while minimizing collisions
The key feature of 1-persistent CSMA when the carrier is busy is that it continuously listens for the carrier to become idle before transmitting
A CSMA scheme suffers from a principal complication related to propagation delay because the time it takes for a signal to travel from one station to another can create uncertainty about whether the channel is busy or not
The purpose of Collision Detection in CSMA/CD is to detect if a collision has occurred during a transmission
Collisions can be detected in wired networks like Ethernet under CSMA/CD by sensing the voltage on the cable, it drops significantly during a collision
The collision detection method using signal power doesn't work for wireless networks because wireless signals are typically received from multiple directions, leading to multiple sources of noise and making it difficult to differentiate collision-induced signals
A larger propagation delay in CSMA schemes increases the collision probability because there is a greater chance that two or more stations will begin transmitting simultaneously without knowing that another station has already started transmitting
The lack of synchronicity between stations due to propagation delay in CSMA schemes contributes to collisions because it leads to uncertainty about the state of the channel and whether or not other stations are already transmitting. This uncertainty can cause two or more stations to attempt to transmit at the same time, resulting in a collision.

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Description

Test your knowledge on types of MAC protocols including collision-free protocols, limited contention protocols, and collision protocols. Explore concepts like static multiplexing, dynamic channel allocation, ALOHA, and Ethernet in this quiz.