DIFFERENCE BETWEEN PURE ALOHA AND SLOTTED ALOHA PDF

Introduced by Norman Abramson and his associates at the University of Hawaii in Introduced by Roberts in Frame Transmission The user can transmit the data frame whenever the station has the data to be transmitted. The user has to wait till the next time slot start, to transmit the data frame. The time here is globally synchronized. When every station transmits the data without checking whether the channel is free or not there is always the possibility of the collision of data frames.

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The user has to wait till the next time slot start, to transmit the data frame. The time here is globally synchronized. When every station transmits the data without checking whether the channel is free or not there is always the possibility of the collision of data frames. If the acknowledgment arrived for the received frame, then it is ok or else if the two frames collide Overlap , they are damaged.

If a frame is damaged, then the stations wait for a random amount of type and retransmits the frame till it transmits successfully. The waiting time of the each station must be random and it must not be same just to avoid the collision of the frames again and again. He proposed to divide the time into discrete intervals called time slots. Each time slot corresponds to the length of the frame. The Slotted ALOHA makes the station to wait till the next time slot begins and allow each data frame to be transmitted in the new time slot.

Synchronization can be achieved in Slotted ALOHA with the help of a special station that emits a pip at the beginning of every time slot as a clock does. As the probability of collision is less in Slotted ALOHA as compared to Pure ALOHA because 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. Related Differences:.