I'm trying to understand slotted ALOHA and I have a question regarding the probabilities. Here is an example: I have 3 nodes, ready to send a frame each. The probability of them sending = 0.5. What is the probability that at time 3 (3 time slots later) they will have all been successful? I know that: P(given node successful) = p(1-p)^(N-1) P(any node successful) = Np(1-p)^(N-1) I have a couple versions of the answer and I'm not sure which one is correct(or none at all): 1) P(node 1 success) + P(node 2 " ") + P(node 3 " ") = 3*[0.5(1-0.5)^(3-1)] = 3/8 OR 2) P(1 node successful) * P(next node " ") * P(last node " ") = 3(0.5)(0.5)^(3-1) * 2(0.5)(0.5)^(2-1) * 1(0.5)(0.5)^(1-1) I'm leaning towards version 2 of my answer, but I don't see how to extend it to t = 4. I don't remember much from my discrete math days. But I'm leaning towards the first one(or a variation of the first one). Please help me clear this up. Thanks for looking! In case you didn't know slotted ALOHA works like this: You have nodes, ready to send "frames" of data. They send every time slot, but when more than one node sends on the same time slot there is a collision and the frames don't make it to its destination. That is why every node sends at the beginning of every time slot based on a certain probability. If there is another crash, the nodes involved resend their frames based on probability p. This continues until eventually only 1 frame is expressed on a time slot, and it is sent successfully.