Slotted Aloha assumptions Poisson external arrivals No capture Packets involved in a collision are lost Capture models are also possible Immediate feedback Idle(o), Success(1), Collision(e) If a new packet arrives during a slot, transmit in next slot If a transmission has a collision, node becomes backlogged while backlogged, transmit in each slot with probability qr until successful Infinite nodes where each arriving packet arrives at a new node Equivalent to no buffering at a node(queue size 1) Pessimistic assumption gives a lower bound on Aloha performanceSlotted Aloha Assumptions • Poisson external arrivals • No capture – Packets involved in a collision are lost – Capture models are also possible • Immediate feedback – Idle (0) , Success (1), Collision (e) • If a new packet arrives during a slot, transmit in next slot • If a transmission has a collision, node becomes backlogged – while backlogged, transmit in each slot with probability qr until successful • Infinite nodes where each arriving packet arrives at a new node – Equivalent to no buffering at a node (queue size = 1) – Pessimistic assumption gives a lower bound on Aloha performance Eytan Modiano Slide 7