Question

A set of nodes are using Slotted Aloha to access a channel. However, a network engineer noticed that their performance is no different to using Pure Aloha. What could be the cause? Hint: clock synchronization.

Answer 1

What is Pure ALOHA ?

whenever the data has to send, Pure ALOHA always allow to transmit whereas Slotted ALOHA does not allow the transmit of data. The slotted ALOHA wait till the next time slot is free. Slotted aloha allow each frame to be achieved with the help of special frames.

The Slotted ALOHA is better than the Pure ALOHA,because in Slotted ALOHA the probability of collision is less as compared to Pure ALOHA. The station waits for the next time slot to begin which let the frame in a previous time slot to pass and avoids the collision between the frames.

Now i tell you why there is no performance issue when we use pure aloha.

we know that In this Pure aloha, any station can transmit the data at any time and  The time is continuous and not globally synchronized. that means its asynchronous and time is continuous so it tackle the asynchronous part and give the same efficiency that slotted aloha gives.

where as in slotted aloha any station can transmit the data at the beginning of any time slot and The time is discrete and globally synchronized.

If you have any doubt feel free to comment and please upvote my answer , its really motivates me to help you.

Thanks in advance