Week 5

Question 1

What is MAC

Answer 1

Medium Access Control

Question 2

What is MAC and what it do

Answer 2

• Channel access procedure
• Protocol Data Unit(PDU) addressing
• Frame Formatting
• Error Checking
• Fragmentation and Reassembly of MSDU

Question 3

More Information on MAC

Answer 3

It ensures security and authentication/privacy
It support roaming and assist stations in power management

Question 4

How does MAC avoid collision in station?

Answer 4

Utilise MAC protocol called Carrier Sense Multiple Access(CSMA), to check channel before transmission.
If someone is transmitting, backoff and transmit ltr

Question 5

Can we use CSMA in wireless?

Answer 5

No. Because wireless network is a spread spectrum, also there is hidden node problem.

Question 6

What is done to prevent collision in wireless 802.11

Answer 6

Employment of RTS and CTS. Right to send and Clear to send

Question 7

What is IFS and its usage

Answer 7

Inter-frame Spacing(IFS), it is a short delay between transmission of frames operating in the medium access control (MAC) sublayer where carrier-sense multiple access with collision avoidance (CSMA/CA) is used.

It add spacing onto frame, to delay the transmit process, depending on priority

Question 8

HOW IFS control transmission

Answer 8

It allocates different sizes of IFS block based on importance of frames sent.
SIFS – Short Interframe Spacing
PIFS – Point Coordination Interframe Spacing
DIFS – Distributed Interframe Spacing

Most important to least

Question 9

What happen if Collision of frame occurs in IFS

Answer 9

Inter-frame spacing. If collision occurs, it will push the transmission of frame backwords by Binary Exponential Backoff Algorithm