Slotted aloha Assumptions Operation o All frames same size o when node obtains fresh o Time is divided into equal frame, it transmits in next size slots time to transmit slot 1 frame o no collision, node can send o Nodes start to transmit new frame in next slot frames only at beginning If collision, node retransmits of slots frame in each subsequent o Nodes are synchronized slot with prob. p until o If2 or more nodes success transmit in slot all nodes detect collision 5: Dat
Slotted ALOHA Assumptions All frames same size Time is divided into equal size slots, time to transmit 1 frame Nodes start to transmit frames only at beginning of slots Nodes are synchronized If 2 or more nodes transmit in slot, all nodes detect collision Operation When node obtains fresh frame, it transmits in next slot No collision, node can send new frame in next slot If collision, node retransmits frame in each subsequent slot with prob. p until success 5: DataLink Layer 5-16
Slotted aloha node1 [1 [1 node2 2 node 3 alot C E C6 E C E S Pros Cons o Single active node can o Collisions wasting slots continuously transmit at o Idle slots full rate of channel ● Nodes may be able to o Highly decentralized: only detect collision in less than slots in nodes need to be in time to transmit packet Sync Clock synchronization ◆Smpe 5: Dat
Slotted ALOHA Pros Single active node can continuously transmit at full rate of channel Highly decentralized: only slots in nodes need to be in sync Simple Cons Collisions, wasting slots Idle slots Nodes may be able to detect collision in less than time to transmit packet Clock synchronization 5: DataLink Layer 5-17