Part $1$: $[5]$ True$/$False questions: Please read each sentence carefully and indicate whether it is true or false.

Collision does not occur when using TDMA MAC protocol.

In FDMA, nodes are assigned different frequency bands, and each node can access the channel in a

fixed$-$length time slot in each round.

In slotted ALOHA, two nodes will never collide with each other in a time slot when they retransmit their

packets after a collision occurs.

In slotted ALOHA, nodes can transmit packets at any time interval.

Link layer handles error detection or correction.

Note: simply write $\text{'}T\text{'}$ for true or $\text{'}F\text{'}$ for false

Part $2$: Suppose we have $9$ nodes using the slotted ALOHA random access protocol to share a channel. $4$

nodes out of these $9$ nodes send packets in each time slot with probability $=0\mathrm{.}1$ and the other $5$ nodes with

probability $=0\mathrm{.}05$

A$.[3]$ What is the efficiency of this system?

B$.[3]$ What is the probability that no node transmits in a slot?

C$.[3]$ What is the probability of collision in a slot?

D$.$ If two more nodes are added to share this channel and these $2$ nodes send packet in each time slot with

probability $=\frac{1}{11}.$

I. $[1]$ How does the probability of successful transmission change? $($increase or decrease$)$

II$.[3]$ What is the probability of successful transmission now?

III. $[1]$ Why does the probability change?

Note: Your numerical answer can be shown up to $3$ decimal places.