EBK COMPUTER NETWORKING
EBK COMPUTER NETWORKING
7th Edition
ISBN: 8220102955479
Author: Ross
Publisher: PEARSON
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Chapter 6, Problem P11P

a.

Explanation of Solution

Given:

Consider that there are four nodes “A”, “B”, “C”, and “D”. These four nodes are active and competing for access to a channel using slotted ALOHA. Each nodes have infinite number of packets.

To find: Probability (p) that the node “A” succeeds for the first time in slot number 5.

Solution:

The probability (p) that the node “A” succeeds for the first time in slot number 5 is (1-p(A))4p(A) --- (1).

Here,

p (A) is the probability that the node “A” succeeds in any slot. That is: p (A transmits, B, C, and D does not transmit).

p(A)=p(A transmit) * p(B does not transmit) * p(C does not transmit) * p(D does not transmit)

b.

Explanation of Solution

Given:

Consider that there are four nodes “A”, “B”, “C”, and “D”. These four nodes are active and competing for access to a channel using slotted ALOHA. Each nodes have infinite number of packets.

To find: Probability (p) that any of the nodes “A”, “B”, “C”, or “D” succeeds in slot number 4.

Solution:

From (a), it is clear that if any node succeeds in any slot, the probability is p(node)=p(1-p)3.

So,

  • The probability that the node “A” succeeds in slot number 4 is: p(A)=p(1-p)3
  • The probability that the node “B” succeeds in slot number 4

c.

Explanation of Solution

Given:

Consider that there are four nodes “A”, “B”, “C”, and “D”. These four nodes are active and competing for access to a channel using slotted ALOHA. Each nodes have infinite number of packets.

To find: Probability (p) that 1st success occurs on slot number 3.

Solution:

Probability of some node occurs in a slot = 4p(1-p)3

Probability of no node succeeds in a slot = 1-4p(1-p)3

Probability of the first success occurs in slot number 3 is determined by multiplying the probability of some node succeeds in a slot and probability of no node succeeds in a slot.

Let p(S) = probability of the 1st success occurs in slot number 3

d.

Explanation of Solution

Given:

Consider that there are four nodes “A”, “B”, “C”, and “D”. These four nodes are active and competing for access to a channel using slotted ALOHA. Each nodes have infinite number of packets.

To find: Efficiency of the four node system.

Solution:

The efficiency of the four node system is determined by the success of any nodes succeeds in a slot...

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