Activity $1$: Investigating Multiple Access Control Protocols

We use different medium access protocols in the data link layer to enable packet transmission in a link with a given shared medium.

We use WiFi on daily basis. In WiFi, we have a shared medium $($wireless$)$ to send packets that are generating in the host devices and

to receive packets.

Let's do a small role play to understand the MAC protocol. Assume that your group forms a Wireless LAN $($WLAN$)$ that uses Wi$-$Fi

technology $($has a wireless access point $($AP$)$ and three wireless devices that connect to Wi$-$Fi AP$).$ One member can be the Wi$-$Fi

AP and other members are the hosts $($could be laptops, smart watches, smart phones, etc.$).$ Assume all the devices in the network

would like to send packets to Internet simultaneously. For example, when you need to send a packet, you can say $"$I$\text{'}$m sending a

packet". If another group member said the same thing at the same time, then a collision occurred, and both need to retransmit

packets.

Your group needs to act as a Wireless LAN and provides a mechanism to enable successful packet transmission. You can

illustrate the protocol that you have designed in a timing diagram $($Shows in Figure $1).$ You are not required to replicate the exact

protocol used in WiFi. You can design your own protocol based on random access that allows hosts to communicate with WiFi AP

with minimal collisions and act fast in case of a packet collision.

WiFi AP

Checking whether

the link is idle

Host A

Host B

Host C$.$

Figure $1$: Timing Diagram of the Protocol

Once you have completed the above activity, discuss the following question with your group members.

What is the medium access control $($MAC$)$ protocol that can be used in WiFi?