MAC Protocols Flashcards
(33 cards)
What is Pure ALOHA?
A protocol where any station can send data at any time, waiting for an acknowledgment after sending.
What happens if an acknowledgment is not received in Pure ALOHA?
The station waits for a random amount of time called back-off time and resends the data.
What is the effect of random back-off time in Pure ALOHA?
It decreases the probability of further collisions.
What occurs when two frames collide in Pure ALOHA?
Both frames are garbled.
What is the throughput formula for Pure ALOHA?
Throughput = G*
What is Slotted ALOHA?
A protocol developed to improve the efficiency of Pure ALOHA by dividing time into discrete slots.
How does Slotted ALOHA reduce collision probability?
Sending is allowed only at the beginning of time slots.
What is required for Slotted ALOHA to function correctly?
The time must be globally synchronized.
What is the throughput formula for Slotted ALOHA?
Throughput = G*
What does CSMA stand for?
Carrier Sense Multiple Access
What is the principle behind CSMA?
Listen before talk.
What does it mean if the carrier is busy in CSMA?
Transmission is taking place.
What does it mean if the carrier is idle in CSMA?
No transmission is taking place.
What can still occur in CSMA despite listening before talking?
Collisions can occur due to propagation delay.
What are the types of CSMA?
- 1-persistent CSMA
- P-persistent CSMA
- Non-persistent CSMA
- O-persistent CSMA
What is a characteristic of 1-persistent CSMA?
If the channel is idle, the station transmits immediately.
What does a busy channel lead to in 1-persistent CSMA?
The station continuously checks the channel until it becomes idle.
What impact does propagation delay have on 1-persistent CSMA performance?
Longer delays worsen performance.
What does Non-Persistent CSMA do when the channel is busy?
The station checks the channel randomly instead of continuously.
What is the advantage of Non-Persistent CSMA over 1-persistent CSMA?
Better channel utilization with longer delays.
How does P-Persistent CSMA operate on slotted channels?
Transmits with probability P if idle, defers with probability (1-P).
What happens in P-Persistent CSMA if another station begins transmission?
The station waits a random time and starts again.
What is O-Persistent CSMA?
Each node is assigned a transmission order by a supervisory node.
What does CSMA/CD stand for?
Carrier Sense Multiple Access with Collision Detection.
