Suppose there are n stations in a slotted LAN. Each station attempts to…

2017

Suppose there are n stations in a slotted LAN. Each station attempts to transmit with a probability P in each time slot. The probability that only one station transmits in a given slot is _______.

  1. A.

    nP(1 – P)n – 1

  2. B.

    nP

  3. C.

    P(1 – P)n – 1

  4. D.

    nP(1 – P)n – 1

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Correct answer: A

Answer: n × P × (1 − P)^(n − 1)

Derivation:

  • There are n choices for which station is the sole transmitter.

  • The chosen station transmits with probability P.

  • Each of the other n − 1 stations does not transmit with probability (1 − P), so together that is (1 − P)^(n − 1).

  • Multiply these factors: n × P × (1 − P)^(n − 1).

Note: P × (1 − P)^(n − 1) is the probability for a specific station to be the sole transmitter; multiplying by n accounts for any one of the n stations.

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