Difference Between Pure ALOHA vs. Slotted ALOHA

Key Differences

The difference between Pure ALOHA and Slotted ALOHA is that in Pure ALOHA time is continuous whereas in slotted ALOHA time is discrete.

Pure ALOHA vs. Slotted ALOHA

In a computer system, there is a sub-link layer, and pure ALOHA and slotted ALOHA are random access protocol that is implemented. In the system of network protocols, the purpose of both pure ALOHA and slotted ALOHA is the same that is to determine the competing station must get the next chance of accessing the multi-access channel. And that is done on the MAC layer that is the medium access control layer. There are types of ALOHA that are pure ALOHA, and slotted ALOHA and the main difference between pure ALOHA and slotted ALOHA is that in Pure ALOHA time is continuous whereas in time slotted ALOHA time is discrete. After the invention of Pure ALOHA in 1970 slotted ALOHA was introduced by Robert that was another method to improve the capacity of Pure ALOHA. Slotted ALOHA improves all the problems that were in Pure ALOHA. In slotted ALOHA time is divided into different time slots. This time slot corresponds to the length of frames. Pure ALOHA allows the transmission of data whenever the data to send whereas Slotted ALOHA does not allow the transmission of data. The slotted ALOHA wait till the next time slot is free. It allows each frame to be achieved with the help of special frames. The formula of slotted ALOHA is S=S*e^-G and when the throughput is maximum, that is G=1 that is 37% of total transmitted data frames.

In Pure ALOHA time is continuous, Pure ALOHA was introduced by Norman Abramson and Pure ALOHA was introduced in the association of the University of Hawaii in 1970. Pure ALOHA has data to be sent, and it allows every station to transmit data. There is a possibility of the collision of data frames so when every station transmits the data without checking whether the channel is free or not. If the frame is free then it is ok to get the frame for the transmission of data whereas if there is no free frame, then data collide. This collision cause frame overloading and the frame are destroyed. When the frame has damaged the stations, have to wait for the random amount of type, and when the frame is free, the transmission is done successfully. There is a waiting time of each frame and when the waiting time is transmitting data the size of the frame should be random. Waiting time of frames should not be the same as it can cause data collisions. When frame size is uniform the throughput of pure ALOHA is maximum. There is a formula to calculate the throughput that is S- = G*e^-2G.

Comparison Chart

Pure ALOHASlotted ALOHA
In Pure ALOHA time is continuousIn slotted ALOHA time is discrete.
Introduced
Pure ALOHA was introduced by Norman Abramson and Pure ALOHA was introduced in the association of the University of Hawaii in 1970Slotted ALOHA was introduced by Robert that was another method to improve the capacity of Pure ALOHA
Formula
There is a formula to calculate the throughput that is S- = G*e^-2G.The formula of slotted ALOHA is S=S*e^-G
Global
Time is globally synchronized in Pure ALOHATime is not globally synchronized in slotted ALOHA

What is Pure ALOHA?

In Pure ALOHA time is continuous, Pure ALOHA was introduced by Norman Abramson and Pure ALOHA was introduced in the association of the University of Hawaii in 1970. Pure ALOHA has data to be sent, and it allows every station to transmit data. There is a possibility of the collision of data frames so when every station transmits the data without checking whether the channel is free or not. If the frame is free then it is ok to get the frame for the transmission of data whereas if there is no free frame, then data collide. This collision cause frame overloading and the frame are destroyed. When the frame has damaged the stations, have to wait for the random amount of type, and when the frame is free, the transmission is done successfully. There is a waiting time of each frame and when the waiting time is transmitting data the size of the frame should be random. Waiting time of frames should not be the same as it can cause data collisions. When frame size is uniform, the throughput of pure ALOHA is maximum. There is a formula to calculate the throughput that is S- = G*e^-2G.

What is Slotted ALOHA?

After the invention of Pure ALOHA in 1970 slotted ALOHA was introduced by Robert that was another method to improve the capacity of Pure ALOHA. Slotted ALOHA improves all the problems that were in Pure ALOHA. In slotted ALOHA time is divided into different time slots. This time slot corresponds to the length of frames. Pure ALOHA allows the transmission of data whenever the data to send whereas Slotted ALOHA does not allow the transmission of data. The slotted ALOHA wait till the next time slot is free. It allow each frame to be achieved with the help of special frames. The formula of slotted ALOHA is S=S*e^-G, and when the throughput is maximum, that is G=1 that is 37% of total transmitted data frames.

Key Differences

  1. In Pure ALOHA time is continuous whereas in slotted ALOHA time is discrete.
  2. Pure ALOHA was introduced by Norman Abramson and Pure ALOHA was introduced in the association of the University of Hawaii in 1970 whereas Slotted ALOHA was introduced by Robert that was another method to improve the capacity of Pure ALOHA.
  3. There is a formula to calculate the throughput that is S- = G*e^-2G whereas the formula of slotted ALOHA is S=S*e^-G.
  4. Time is globally synchronized in Pure ALOHA whereas time is not globally synchronized in slotted ALOHA

Comparison Video

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Harlon Moss

Harlon currently works as a quality moderator and content writer for Turpy Media. He graduated from the University of California in 2010 with a degree in Computer Science. Follow him on Twitter @HarlonMoss or on Pinterest @HarlonMoss

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