Probability Question: Slotted Aloha

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In summary, Zulfi asked for help understanding a solution they found on the internet. The other person refused to provide an answer and encouraged Zulfi to show their own work and explain their thought process. Zulfi admitted to struggling with probability and shared their attempt at solving a problem. They asked for feedback on their answer.
  • #1
zak100
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11
Homework Statement
Suppose four active nodes – nodes A, B, C and D – are competing for access to a channel using slotted ALOHA. Assume each node ha an infinite number of packets to send. Each node attempts to transmit in each slot with probability p. The first slot is numbered slot 1, the second slot is numbered slot 2, and so. What is the probability that node A succeeds for the first time in slot 5?
Relevant Equations
I found a solution which does something like that:
(1-p(A))^4 * P(A).
Can some body please explain me this solution?

Zulfi.
 
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  • #2
zak100 said:
Can some body please explain me this solution?
Not until you show us your work. How did you derive that solution?
 
  • #3
Hi,
I got it from internet. I can't understand it. Please guide me.

Zulfi.
 
  • #4
zak100 said:
Hi,
I got it from internet. I can't understand it. Please guide me.

Zulfi.
That violates our rules. We are not here to feed you answers. We help you to do your own work. If you have done no work other than an Internet search, then you're not ready to ask for help.

What course are you taking? What background do you have that should prepare you to be able to do that homework? Why would you use the Internet instead of using that background?
 
  • #5
Probability is my weak point. I can't solve probability questions. That's why I am asking help
Zulfi.
 
  • #6
Describe the whole sequence of events "succeeds for the first time in slot 5".

Once you have a description of the events, you can model them.

What happens at slot 1?
What happens at slot 2?
etc
 
  • #7
Hi,
Success = P(A)
Failure = 1-P(A)
Slot1= no success= 1-P(A)
Slot2 = no success = 1-P(A)
Slot3 = no success = 1-P(A)
Slot4 = no success = 1-P(A)
Probability from 1 to 4 = (1-P(A))^4
Slot 5 = Success of A but failure of other nodes = P(A) * (1-P(B)) * (1-P(C)) * (1-P(D))

Total probability = (1-P(A))^ 4 * P(A) * (1-P(B)) * (1-P(C)) * (1-P(D))

I think I am very close to the answer. Please tell me how to correct the answer?

Zulfi.
 
  • #8
Hi,
Still waiting for your correction.

Zulfi.
 

FAQ: Probability Question: Slotted Aloha

What is Slotted Aloha?

Slotted Aloha is a random access protocol used in telecommunications and computer networks to regulate data transmission. It was developed in the 1970s and is still used today in some systems.

How does Slotted Aloha work?

Slotted Aloha divides time into discrete slots and assigns each slot to a user for data transmission. Users can only transmit data during their assigned slot, and if there is a collision, the data is retransmitted in a future slot.

What is the main advantage of using Slotted Aloha?

The main advantage of Slotted Aloha is that it allows for a higher throughput compared to other random access protocols. By assigning specific time slots, it reduces the likelihood of collisions and increases the efficiency of data transmission.

What is the drawback of using Slotted Aloha?

The main drawback of Slotted Aloha is that it is not suitable for large networks with high traffic. As the number of users and data transmissions increase, the chances of collisions also increase, leading to a decrease in efficiency.

How is the probability of successful transmission calculated in Slotted Aloha?

The probability of successful transmission in Slotted Aloha is calculated as G * e^(-2G), where G is the offered load or the average number of data transmissions per slot. This formula takes into account the probability of successful transmission in a given slot and the probability of no other transmissions occurring in that slot.

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