Computer-Networks

Question 15

Consider a simplified time slotted MAC protocol, where each host always has data to send and transmits with probability p = 0.2 in every slot. There is no backoff and one frame can be transmitted in one slot. If more than one host transmits in the same slot, then the transmissions are unsuccessful due to collision. What is the maximum number of hosts which this protocol can support, if each host has to be provided a minimum through put of 0.16 frames per time slot?

A	1
B	2
C	3
D	4

Computer-NetworksData-Link-LayerGATE 2004-IT

Question 15 Explanation:

Let there be N such hosts. Then when one host is transmitting then others must be silent for successful transmission. So throughput per host,
0.16 = 0.2 × 0.8^N-1
⇒ 0.8 = 0.8^N-1

⇒ N = 2

Correct Answer: B

Question 15 Explanation:

Let there be N such hosts. Then when one host is transmitting then others must be silent for successful transmission. So throughput per host,
0.16 = 0.2 × 0.8^N-1
⇒ 0.8 = 0.8^N-1

⇒ N = 2